Term
| Streptocci characteristics |
|
Definition
Gram positive cocci
Catalase negative
Facultative anaerobes
Differentiated based on hemolysis on blood agar. |
|
|
Term
| Alpha hemolytic streptococci |
|
Definition
| Pneumococcus (no lancefield grouping): optochin sensitive (O‐VeRPasS) Viridans, Milleri group: optochin resistant |
|
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Term
|
Definition
Group A (S. pyogenes): bacitracin sensitive (B‐BRAS)
Group B (S. agalactiae): bacitracin resistant |
|
|
Term
|
Definition
Group D (S. gallolyticus): penicillin sensitive (P‐ERDS)
Enterococcus (not a Strep): penicillin resistant |
|
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Term
|
Definition
1. Polysaccharide capsule (major virulence factor): antiphagocytic, basis of serotyping
2. Peptidoglycan: act. complement (inflammation), analogous to endotoxin 3. Teichoic acid: attach to TLR of epithelial cells, trigger inflammation via CRP & TLR2
4. Choline‐binding protein (PspA, major virulence factor): antiphagocytic, vaccine target
5. Pneumolysin (major virulence factor): act. Complement (inflammation), vaccine target
3 structures trigger inflammation: teichoic acid, pneumolysin, peptidoglycan
Antibody to pneumolysin > autolysin/PspA |
|
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Term
| Pneumococcus characteristics |
|
Definition
No Lancefield antigen
Incidence & severity of pneumococcal pneumonia is higher in elderly than in younger adults
Pneumococcus is also the most common cause of otitis media & acute sinuisits in children of daycare center |
|
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Term
|
Definition
| Presence of normal flora without symptoms |
|
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Term
|
Definition
| presence of proliferating abnormal bacteria w/o symptoms |
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Term
| Pneumococcus pathogenesis |
|
Definition
Spread of bug:
a. Secretion: travel via secretion (aspiration/inhalation) to enter sterile space w/ poor clearance
Risk factors: Alcohol, smoking, recent viral infection, allergy, asthma, opiates, elderly
b. Local invasion: cross epithelial cell layer to enter blood or lymph to CNS or systemically
Both pathways lead to inflammation (NOT toxin) damages tissues & causes the disease
Prototypical example: pneumonia
1. Pneumococci enter alveoli, poor clearance
2.Capsule prevent phagocytosis
3. Bug trigger inflammation (alternative & classical pathway via LTA binding to TLR2)
4. Alveoli filled w/ WBCs, RBCs, plasma crap => inflammation & damage |
|
|
Term
| Risk factors for pneumococcus |
|
Definition
1. Decreased pulmonary clearance: alcohol, opiates, smoking, viral infection, pollution
2. Decreased neutrophil function: DM, GC, renal failure, liver failure
3. Decreased IgG production: congenital, cancer, CVID, HIV
Absence of spleen => sepsis |
|
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Term
|
Definition
MOPS
1. Diseases caused by direct extension in respiratory tract:
a. Pneumonia (mcc)
b. Acute otitis media and sinusitis (mcc)
c. Acute exacerbation of chronic bronchitis (2nd mcc)
2. Hematogenous spread
a. Meningitis (mcc)
b. Bacteremia
c. Endocarditis (rare)
d. Peritonitis (rare) |
|
|
Term
|
Definition
Symp: cough , fever, "rusty" sputum, chest pain, looking "very sick"; parapneumonic effusion &
empyema may occur
Pneumococcal pneumonia often preceded by viral illness. |
|
|
Term
|
Definition
| Dx: chest X ray, sputum culture, blood culture, polysaccharide urine test (Binex) |
|
|
Term
| Causes of pneumococcal immunity |
|
Definition
1. Local mech (intact clearance mechanisms)
2. Innate immunity
3. Humeral immunity:
- Anti‐pneumolysin, anti‐PspA antibodies
- Anti‐polysaccharide capsule antibodies: takes 2‐3 wks to develop, may develop pneumonia during this time |
|
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Term
|
Definition
1. Polysaccharide capsule vaccine: - Pneumovax
- T‐cell independent, NOT protective < 2 yrs
- Serotype‐specific
2. Protein‐conjugated vaccine:
- Prevnar - T‐cell dependent, protective < 2 yrs - Benefits:
Direct effect: reduced colonization & dz in vaccinated strains
Herd effect: reduced dz in non‐vaccinated kids - Disadvantages:
Serotype‐specific
Bacterial replacement by non‐vaccinated strains |
|
|
Term
|
Definition
ID: resistant to optochin
Alpha‐hemolytic: think of green "verde" bacteria growing in mouth & teeth
Types:S. mitus, S. salivarius, S. mutans, S. sanguis
Normal colonizers of oral cavity 2 main infections:
1. Dental caries: most common infection worldwide
2. Subacute bacterial endocarditis on damaged valves (due to rheumatic fever, etc)
Antibiotic prophylaxis for dental procedures in pt w/ prosthetic valves |
|
|
Term
| Milleri group streptococci |
|
Definition
Types: S. constellatus, S. intermedius, S. anginosus (subgroup of Viridans) (NM: Milleri = Military CIA)
•Normal microaerophilic bowel flora
•Causes pyogenic (pus) abscess (newly formed cavity) & empyema (pre‐existing cavity) in brain or abdominal organs
NM: S. InterMeDius and AnginoSus, IMeDiately Assess for ABSCESS |
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Term
|
Definition
1. M‐protein (major virulence factor): anti‐phagocytic, Ig offers long‐lasting immunity
2. C‐carbohydrate: Lancefield classification
3. Peptidoglycan: phage receptor (needed to obtain exotoxin from a lysogenic phage), endotoxin‐like
4. Lipoteichoic acid: adherence, exist in Gram + cell wall only
5. Capsule (hyaluronic acid): non‐antigenic, anti‐phagocytic |
|
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Term
|
Definition
1. Pyrogenic exotoxin (erythrogenic toxin):
a. Superantigen binds to V‐beta of TCR b. Causes "scarlet fever" & "toxic strep syndrome"
c. Ig offers future protection
2. Streptokinase: activates plasminogen to lyse blood clot in coronary occlusion
3. Streptolysin O (ASO): Ig is marker for rheumatic fever (RF), NOT useful for skin infections, neutralized by cholesterol.
4. DNAse B: Ig is marker for RF, can be used for skin infections too
5. Hyaluronidase: Ig is marker for RF, creates dishwater pus? |
|
|
Term
| Directly mediated S. Pyogenes diseases |
|
Definition
1. Strep pharyngitis (strep throat):
-Fever, enlarged tonsil, white exudates
-Throat culture or rapid antigen detection test (RADT)
2. Skin infections:
NM: unlike its counterpart Staph, Strep pyo causes those swollen lymph erysipelas & simple non‐pussy cellulitis
a. Impetigo (pyoderma): epidermis only, crusty and flaky blister around mouth & ear lobe, papule‐vesicle‐pustule
crusting seq
b. Erysipelas: dermis only, raised bright red rash, diffuse lymphangitis of skin
-Saphenous vein harvesting
-Axillary lymph node dissection c. Cellulitis: dermis & subcu fat, diffuse inflammation & edema
d. Cellulitis in dorsum of feet w/o skin lesion: strep infection -
e. Necrotizing fasciitis (gangrene)
3. Scarlet fever:
-Erythema due to pyrogenic/erythrogenic toxin (post‐lysogenic conversion)
-Strawberry tongue & sandpaper rash
-Think of strep pyo causing strep throat, skin/lymph cellulitis & scarlet fever (do you see the strawberry tongue?)
4. Strep toxic shock syndrome: - Caused by pharyngeal (not skin) strep infections (pyrogenic exotoxin) - Hypotension, organ failures (kidney, lung, liver), rash
-Remember Strep toxic shock is HIGH mortality |
|
|
Term
| Auto-immune responses to S. Pyogenes |
|
Definition
1.Acute rheumatic fever:
-Occurs after pharynx strep infection ONLY (never skin)
-Diagnosis: increased ASO, anti‐DNAse B, anti‐hyaluronidase
-Symptoms=CANCER: Carditis, polyArthritis, Nodules, Chorea, ERythema marginatum
-Prophylactic penicillin tx
-Pts with rheumatic fever (valvular heart disease) need to be given antibiotics before dental or surgical procedure
2. Acute glomerulonephritis
-Occurs after pharynx OR skin strep infection
-Diagnosis: decreased C3, C4, hematuria (tea‐colored urine)
-This is a tricky one, tea‐colored urine from glomerulonephritis is the only one due to BOTH Strep throat AND Strep skin (so DNAse B is the better marker here)
3. Acute guttate psoriasis:
-Occurs after pharynx strep infection
-Caused by strep supertoxin => small psoriatic lesions |
|
|
Term
|
Definition
ID: resistant to bacitracin, CAMP+
•Normal bowel & vaginal flora
•Major risk factor: absence of antibody to type‐specific carbohydrates predispose mother & neonates to infection
•Infect neonates, post‐partum women & old/immunocompromised pts (B for Baby) •Neonates: meningitis, pneumonia, sepsis (early: < 7d, late: > 7d)
•Post‐partum women: OBGYN infections
•Old/immunocompromised pts: pneumonia, sepsis |
|
|
Term
|
Definition
|
|
Term
|
Definition
ID: sensitive to penicillin
•S. gallolyticus (S. bovis)
•Normal bowel flora
•Strong association between S. gallolyticus bacteremia/endocarditis & colon cancer, req. colonoscopy!
NM: Bovis in Blood, Cancer in Bowel |
|
|
Term
|
Definition
•ID: Resistant to penicillin & many antibiotics, high tolerance (MBC > 1/32)
•E. faecalis, E. faecium
•Normal bowel flora
•2nd leading cause of nosocomial infection: transmitted via unwashed hands in hospitals
•Infections: endocarditis, nosocomial UTI, nosocomial bacteremia
•Possess intrinsic resistance to antibiotics & can survive on inanimate objects
•Sexually promiscuous: vanA plasmid from vancomycin resistant enterococcus (VRE) can be transferred to Staph aureus
(VRSA)
•Endocarditis & meningitis req. combination of 2 antibiotics for treatment (beta‐lactam + aminoglycoside) to achieve MBC |
|
|
Term
| Staphylococci characteristics |
|
Definition
Gram positive cocci
Facultative anaerobes
• Beta‐hemolytic
•Differentiated based on coagulase testing:
Coagulase positive: high virulence, nasal carriage, #1 cause of endocarditis, osteomyelitis & septic arthritis
-S. aureus: gold color on agar
Coagulase negative: low virulence, nl flora of skin & nasopharynx, nosocomial infection
-S. epidermidis: novobiocin sensitive (NO‐StRES)
-S. saprophyticus: novobiocin resistant |
|
|
Term
|
Definition
1. Peptidoglycan: same as any other PTG, toxic for PMN (refer to sepsis lecture!)
2. Teichoid acid: adherence & IgG formation
3. Capsule glycocalyx:
-Capsule: antiphagocytic, not important -Microcapsule (coagulase pos bugs): antigenic, basis for serotyping
-"Slime" (coagulase neg bugs): adherence, anti‐phagocytic, antibiotic resistance for infection of prosthetic devices
4. Surface proteins:
-Protein A (major virulence factor): antiphagocytic via binding to IgG Fc (used in labs for pull‐down exps!) -MSCRAMM: bind to ECM to aid colonizing |
|
|
Term
|
Definition
1. Catalase: H2O2 => H2O + O2
2. Coagulase: clumping (+ in S. aureus, ‐ in others)
3. Hyaluronidase: destroy ECM to aid spreading |
|
|
Term
|
Definition
1. Alpha‐toxin: disrupt cell memb
2. Exfoliatin: superantigen, scaled skin syndrome, Ig is protective
3. TSST‐1: superantigen, fever & shock, Ig is protective
4. Enterotoxin: superantigen, ST, food poisoning |
|
|
Term
| Staph antibiotic resistances |
|
Definition
1. Beta‐lactam resistant SA (95%):
-Beta‐lactamase carried on plasmid cleaves penicillin => Staph is 95% resistant to penicillin!
Tx w/ methicillin
2. "Intrinsic resistance" or methicillin‐resistant SA or SE (MRSA, MRSE):
-Mutant PBP2a (decrease affinity of binding by antibiotics) encoded on mecA or SCCmec genes
-2 types:
a. HA‐MRSA: chsm mecA gene, tx with vancomycin or linezolid
b. CA‐MRSA: mobile SCCmec IV gene, Panton‐Valentine Leukocidin is a marker, tx with clindamycin or bactrim
3. Vancomycin‐intermediate SA (VISA): -MRSA + intermediate vancomycin resistance
-These bugs have thicker cell wall
4. Vancomycin‐resistant SA (VRSA):
-MRSA + full vancomycin resistance
-Conjugation of MRSA + VR Enterococcus -Tx with daptomycin or linezolid
•Important Caveat:
-Clindamycin should only be used if SA is sensitive to Erythromycin. If bug is resistant to Erythromycin, D‐test needs to be performed before Rx Clindamycin Pos D‐test: inducible Clindamycin resistance (Erm gene) => cannot use Clindamycin.
Neg D‐test: safe to use Clindamycin |
|
|
Term
|
Definition
Sequential expression of virulence proteins: adherence factors during rapid growth phase, toxins during stationary phase
Adherence is necessary for infection Colonizers in nose & throat
Risk factors for colonization/infection:
-
1. Atopic dermatitis/eczema
2. Needle user/injured skin
3. Sutures/prosthetic devices ‐ encased in protective glycocalyx |
|
|
Term
|
Definition
1. Exotoxin release:
a. Toxic Shock Syndrome: TSST‐1 superantigen leading to septic shock, NOT as fatal as Strep Toxic Shock Syndrome
b. Staph Scaled Skin Syndrome (SSSS): exfoliatin at stratum granulosum in children
c. Gastroenteritis (food poisoning): preformed heat‐stable enterotoxins, explosive onset with 2‐7 hrs incubation,
resolves w/ supportive tx (NOT antibiotics)
2. Direct organ invasion:
NM: anything bubbly (bullous), pussy (pus), or oily (folliculitis) is a Staph skin infection
NM: Staph is #1 cause of acute endocarditis, osteomyelitis & septic arthritis, nosocomial pneumonia
a. Skin infections (refer to skin & soft tissue infections lecture):
-Impetigo: either Strep or Staph cause, bullous impetigo is characteristic of S. aureus infection
-Cellulitis, & wound infection Folliculitis, furuncle, carbuncle, hidradenitis suppurativa: infection of hair follicles, 1st cause is S. aureus
-Hot tub folliculitis: infection due to Pseudomonas aeruginosa (not Staph) in hot tubs
b. Abscess: pus formation, 1st cause is S. aureus (Strep doesn't form pus)
-Pyomyositis: deep soft tissue infection, 1st cause is S. aureus
c. Bacteremia & acute endocarditis: #1 cause - Primary: no obvious focus of infection (endocarditis) - Secondary: secondary to infection (abscess, catheter)
d. S. aureus causes acute infective endocarditis on normal or abnormal valves (refer to endocarditis lecture):
Clues: Young pt with NO underlying illnesses, NO previous valvular dz, also commonly seen in IV drug user
Tx: >4 wks of antibiotics
e. Osteomyelitis & septic arthritis: #1 cause (refer to osteomyelitis lecture)
f. Pneumonia: #1 cause of nosocomial pneumonia (refer to nosocomial lecture) |
|
|
Term
|
Definition
Normal colonizers of skin & nasopharynx •Frequent skin contaminant of blood cultures => 2 blood draws
•Microcapsules help adhere and form biofilms on catheters
• Dz:
1. Infection & failure of prosthetic devices: Prosthetic joints, heart valves, peritoneal dialysis catheters 2. Subacute endocarditis on prosthetic valves or IV drug users
3. #1 cause of primary bacteremia in immunocompromised pts |
|
|
Term
|
Definition
Normal colonizers of skin & nasopharynx •2nd cause of out‐patient UTI
E. coli & S. saprophyticus are the 2 most common causes of UTI
E. coli & Enterococcus are the 2 most common causes of nosocomial UTI |
|
|
Term
| Unique virulence factors in Staph and Strep |
|
Definition
•Strep pneumo: choline‐binding protein (PspA), pneumolysin
•Strep pyogenes: M‐protein,non‐antigenic capsule
•Strep agalacteae: absence of antibody to type‐specific carbohydrate
•Staph aureus: microcapsule, Protein A, MSCRAMM
•Staph epidermidis & saprophyticus: slime |
|
|
Term
| Peptostreptococci, Peptococci |
|
Definition
Gram positive anaerobe cocci
•Normal GI & GU flora
•Cause infections in sterile sites: abscess (brain, lung, genital tract), diabetic foot ulcer, septic abortion, endometritis
Pepto, Strepto, give me abscess in the big toe (DM foot ulcer) & septo (abortion...)
Always think of "polymicrobial abscess" when thinking of anaerobes |
|
|
Term
| Clostridium characteristics |
|
Definition
Gram‐positive anaerobe rods
Spore forming
Secrete powerful exotoxins! |
|
|
Term
|
Definition
Secrete lethal neurotoxins (A‐G) that blocks release of ACh from presynaptic nerve terminals => flaccid muscle paralysis
1. Adult botulism: -Ingesting food contaminated with preformed neurotoxins
Dx: bilateral cranial nerve palsies ‐ diplopia, dysphagia, respiratory paralysis
Tx: antitoxins
2. Infant botulism: - Ingest food contaminated with dormant C. botulinum spores
NM: A bottle of honey gives you a floppy baby
Dx: "floppy babies"
Tx: antitoxins & IGIV |
|
|
Term
|
Definition
Secrete tetanospasmin that enters presynaptic neuron to travel retrogradely to cell bodies of spinal cord ‐ inhibit the
inhibition of efferent neurons => prolonged stimulation at motor end‐plate => twitching muscles
Dx: tetany, lockjaw, respiratory paralysis
NM: Tetany for Twitching
Tx: human tetanus immune globulins (antitoxins), neuromuscular blockade (curare), airway protection |
|
|
Term
|
Definition
Cause 4 infections:
1. Crepitant cellulitis/wound infection: gas gangrene
2. Clostridial myonecrosis: rapid muscle necrosis, alpha‐exotoxin 3. Enteritis necroticans: GI necrosis C. septicum bacteremia = highly associated with GI malignancy
4. Diarrheal illness: food poisoning (8‐14 hrs, longer incubation than Staph aureus) |
|
|
Term
|
Definition
1st cause of nosocomial diarrhea following use of broad‐spectrum antibiotics in hospital (remember the old lady w/
osteomyelitis tx w/ antibiotics in a C. dif spore‐spread hospital and gets diarrhea & leukomoid rxn!)
Cause antibiotic‐associated pseudo‐membranous colitis (diarrhea)
Dx: severe diarrhea (watery or bloody depending on the toxin produced), cramping, fever, pseudomembranes (white
exudate) on inflamed GI mucosa in colonoscopy
Tx: oral Vancomycin (NOT IV as it doesn't enter GI tract!) |
|
|
Term
|
Definition
Gram‐positive fungi‐like bacteria
•"Fungus‐looking beaded‐filamentous anaerobic rod"
•Normal colonizers of mouth & GI
•Cause eroding oral/facial abscesses that drain thru sinus tracts following trauma
•Dx: yellow sulfur granules in sinus tracts, "the most misdiagnosed disease" •Tx: penicillin & surgical drainage |
|
|
Term
| Haemophilus characteristics |
|
Definition
•Gram‐neg coccobacilli
• Growth:
Chocolate agar: contain X factor (hemin), V factor (NAD) & CO2 |
|
|
Term
| Haemophilus cell structure/virulence factors |
|
Definition
1. Capsule: antiphagocytic, polyribosyl ribitol phosphate (PRP), antibody is protective (used in HIB vaccine)
2. Outer Membrane protein: antibody is protective 3. LipoOLIGOsaccharide (LOS): stimulate inflammation, antibody is protective
3. Pilli mediate attachment |
|
|
Term
|
Definition
Pathogenesis (same as pneumococcus):
1. HITB spread via contact, secretion or aerosol
2. HITB penetrate epithelial layers, spread via direct or hematogenous route 3. LOS (endotoxin) stimulates inflammation & cause dz (same as LTA, PTG & pneumolysin in pneumococcus) |
|
|
Term
|
Definition
Dangerous especially to infants
1. Meningitis: HITB used to be the major cause of meningitis in toddlers (6 mo ‐ 4 yrs)
2. Epiglottitis: acute swelling of epiglottis, obstructing esophagus & airway
3. Sepsis: highest risk in asplenic pt 4. Septic arthritis: HITB used to be the leading cause in infants
-Remember, Haemophilus Type B in a Baby is NOT something you want to MESS around with (Meningitis, Epiglottis, Sepsis, Septic Arthritis), so get vaccinated right away! |
|
|
Term
| Nontypable H. influenzae (NTHI), Moraxella catarrhalis & H. parainfluenzae |
|
Definition
Lack of capsule but has OM, less virulent
•Colonizers of pharynx in most kids in day care center (same as pneumococcus) •Pathogenesis (same as pneumococcus):
1. Cause disease when displaced in sterile spaces with poor clearance
2. LOS (endotoxin) stimulates inflammation & cause dz (same as LTA, PTG & pneumolysin in pneumococcus)
•Dz (same as pneumococcus):
1. Acute exacerbation of chronic bronchitis (AECB): NTHI > Pneumococcus > Moraxella > H. parainfluenzae
2. Otitis media & acute sinusitis: Pneumococcus > NTHI > Moraxella > H. parainfluenzae
3. Pneumonia: Pneumococcus > NTHI
4. Puerperal fever/sepsis of newborn: NTHI biotype IV |
|
|
Term
|
Definition
| Causes chancroid: venereal ulcer resembling syphilis chancre but is painful, unilateral painful swollen lymph nodes |
|
|
Term
| H. influenzae subgroup aegyptius |
|
Definition
| Causes Brazilian hemorrhagic fever |
|
|
Term
| Enterobacteriaceae characteristics |
|
Definition
Gram‐negative rods
•Oxidase negative (Neisseriae & Pseudomona are oxidase positive) & nitrate reduction
•Gram negative rods that live in lower GI tract
•Facultative anaerobes, no spore formation
•Most are motile (except Shigella & Klebsiella), Red Proteus swarms • Grow in Gram‐neg‐only medias:
EMB agar: lactose fermenters => purple‐black coloration, E. coli => green
MacConkey agar: lactose fermenters => pink‐purple coloration
Fermentation pattern:
Lactose positive (turn MacConkey pink) ‐ Klebsiella, E. coli, Enterobacter - NM: lactose is KEE so test is with MacConKEE agar
Lactose negative ‐ Salmonella, Shigella, Proteus, Yersinia |
|
|
Term
| Enterobacteriaceae surface antigens |
|
Definition
1. O antigen: outer polysaccharide of LPS endotoxin ‐ antiphagocytic
2. K antigen (virulence factor & poor immunogen!): capsule ‐ antiphagocytic (opsonization needed), biofilm formation
3. H antigen: flagella protein ‐ motility |
|
|
Term
| Enterobacteriaceae virulence factors |
|
Definition
• Adhesins:
Type 2 or P fimbriae = Pyelonephritis
Type 1 fimbriae = cyst1t1s
• Exotoxin:
Heat‐labile (LT), heat‐stable (ST) Shiga‐like toxin
Hemolysin
•Endotoxin: Lipid A of LPS, pyrogenic (induces inflammation)
LPS: live in gut ‐ enterobacteriaceae, vibrio, etc
LOS: sensitive to bile salts, cannot live in gut ‐ Neisseria, Haemophilus, Chlamydia, etc
•Iron‐binding siderophore: Fe+2 scavenger
Fe+2 overload => Yersinia infection
•Capsules: antiphagocytic, NON‐antigenic (just like Strep pyogenes...)
•Plasmids: transfer resistance |
|
|
Term
| Enterobacteriaceae members |
|
Definition
Lactose positive: Klebsiella, E. coli, Enterobacter
Lactose negative: Serratia, Salmonella, Shigella, Proteus, Yersinia |
|
|
Term
| Escherichia coli extraintestinal infections |
|
Definition
#1 cause of UTI (CA & nosocomial) Leading cause of abdominal/pelvic infections (peritonitis, abscess)
#2 cause of neonatal meningitis (after Strep agalactiae)
Nosocomial pneumonia or bacteremia: rare |
|
|
Term
| Escherichia coli intestinal infections |
|
Definition
| Divided into ETEC, EHEC, STEC, EAEC, EPEC, and EIEC categories. |
|
|
Term
| Enterotoxigenic E. coli (ETEC) |
|
Definition
Characteristics:
•High‐dose pathogen (food & water) Pathogenesis:
1. Attach to intestinal cell surface via human‐specific fimbriae
2. Secrete Enterotoxin (exotoxin):
-Heat‐labile (LT): increase cAMP (= Cholera AB toxin acts on CFTR to release Cl‐)
-Heat‐stable (ST): increase cGMP
•ETEC does NOT invade the cell
Symp: rice water diarrhea w/out fever ‐ same as Vibro cholera
Dz: 1st cause of travelers' diarrhea Tx: prophylaxis with Pepto‐Bismol |
|
|
Term
| Enterohemorrhagic E. coli (EHEC) & Shigatoxin‐producing E. coli (STEC) |
|
Definition
Characteristics:
•Low‐dose pathogen (daycare center)
•Reservoir in cattle, infected lettuce, spinach & red meat burger
Pathogenesis:
1. Attach to intestinal cell surface via fimbriae (similar to ETEC)
2.Secrete powerful Shiga‐like exotoxin (SLE encoded in lysogenic phage) -EHEC does NOT invade the cell
-O157:H7 strain causes hemolytic uremic syndrome (HUS):
a. Hemolytic anemia
b. Thrombocytopenia
c. Kidney failure
Symp: bloody cramping diarrhea w/out fever (no invasion)
Tx: supportive, antibiotics contraindicated due to lysogeny of phage |
|
|
Term
| Enteroinvasive E. coli (EIEC) |
|
Definition
Pathogenesis:
1. EIEC invade intestinal epithelial cells
2. Secrete tiny amount of Shiga AB toxin
3. Trigger immune‐mediated inflammation
Symp: bloody diarrhea w/ WBCs & fever ‐ same as shigella |
|
|
Term
| Enteropathogenic E. coli (EPEC) |
|
Definition
LEE pathogenicity island (attach & efface): attach to intestinal epithelial cells & destroy microvilli
Dz: 1st cause of neonatal diarrhea in developing countrie
For EPEC, think of P for Pathogenicity island Packed of shitting babies |
|
|
Term
| Enteroaggregative E. coli (EAEC) |
|
Definition
Stack brick appearance
Dz: 1st cause of AIDS‐associated chronic diarrhea & 2nd cause of travelers' diarrhea |
|
|
Term
|
Definition
Non‐motile opportunistic bug
Mucoid capsule: antiphagocytic
Express beta‐lactamase: resistant to beta‐lactams
Extra‐intestinal infections:
-Nosocomial pneumonia (bloody, currant jelly sputum) in alcoholics & immunocompromised pts
-Nosocomial UTI with urinary catheters |
|
|
Term
|
Definition
Same characteristics as Klebsiella except motile
Highly resistant opportunistic bug in ICU |
|
|
Term
|
Definition
|
|
Term
|
Definition
May be lactose‐pos or neg
Widespread opportunistic bug that favors moist environments (navy) Produce bright red pigmented colonies on MacConkey agar
Extra‐intestinal infections:
-Nosocomial infections
-Endocarditis in IV drug users (one of the really really rare causes of endocarditis) |
|
|
Term
| Proteus & cousins (Morganella, Providencia) |
|
Definition
Motile bug that swarms on agar
Produce urease => crystal stone & biofilm formation => encrustation of catheters
Extra‐intestinal infections:
-Nosocomial UTI with urinary catheters -Precipitation of stones on catheters |
|
|
Term
|
Definition
Characteristics:
-Low‐dose pathogen (daycare center)
-Bug ONLY affect humans & primates (remember the dying gorilla!)
-Cause dysentery: frequent stools with blood & mucus
Prevalence: -Highest in preschool children (1‐4 yrs) in crowded daycare & war camps
Pathogenesis:
shigella = EIEC (invasion) + EHEC (Shiga‐like toxin)
1. Shigella invade intestinal epithelial cells
2. Secrete Shiga AB toxin: destroys ribosome
3. Trigger immune‐mediated inflammation
Symp: bloody diarrhea w/ fecal leukocytosis & fever = dysentery
Tx: antibiotics are helpful, but only after ruling out EHEC/STEC! |
|
|
Term
| Salmonella characteristics |
|
Definition
-Intermediate‐dose pathogen (food & water)
-Vi antigen (capsule) = K antigen, vaccine target |
|
|
Term
|
Definition
| Can be typhoidal or non-typhoidal (gastroenteritis). |
|
|
Term
| Gastroenteritis (Salmonella enterica) |
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Definition
Reservoir: Zoonotic, bug lives in GI tract of animal ‐ turtle, chicken & egg (poultry related)
Prevalence: Highest for infants < 1‐yo due to housewives (remember the story of unapproved FBI reporter)
Pathogenesis:
1. Invade intestinal epithelial cells
2. Trigger immune‐mediated inflammation 3. Self‐limiting & long incubation period, usually does NOT invade bloodstream
Symp:
Watery or bloody diarrhea w/ fever Can lead to bacteremia & sepsis: aortic aneurysm & osteomyelitis in sickle cell pts
Tx: supportive, antibiotic tx (cipro, ceftriaxone) should be avoided but MUST TX at‐risk pts (old & young) |
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Term
| Typhoid/enteric fever (Salmonella typhi & paratyphi) |
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Definition
Reservoir:
•Obligate human pathogen: may be chronically carried in gallbladder (Typhoid Mary)
Prevalence:
•Highly associate with travelers to India (know this!)
Pathogenesis:
1. S. typhi invade intestinal epithelial cells
2. Invade lymph nodes & survive in macrophages (facultative intracellular bug)
3. Disseminate in blood
Symp:
Fever, bloody diarrhea, headache, abdominal pain mimicking appendicitis Rose spots on belly
Untreated can lead to intestinal perforation
Dx: blood/marrow culture of intracellular parasite (S. typhi)
Tx: cipro, ceftriaxone (target intracellular bacteria) |
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Term
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Definition
Characteristics: Zoonotic, grow at 4 degress (cold enriched)
Lack siderophore => iron overload increases risk of Y. enterocolitica infection
Reservoir: Domestic & wild animal Transmitted via food (undercooked pork) & water (contaminated camping stream)
Pathogenesis: Invade epithelial cells, disseminate in blood => bacteremia - Secrete ST enterotoxin
Symp: fever, bloody diarrhea, abdominal pain mimicking appendicitis
Dx: culture w/ cold enrichment
For YERsinia enteroCOLitica, pronounce it like "IRONsinia enteroCOLDlitica" and think of a pirate (yerr) who loves to eat iron (iron overload) & cruise the seven bloody seas (disseminated in blood) |
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Term
| Members of Vibrio species |
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Definition
Vibrio Cholera
Vibrio Parahaemolyticus
Vibrio vulnificus |
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Term
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Definition
Characteristics:
-Curved gram‐negative rod w/ single polar flagellum
-Transmitted via water during warm monsoon seasons, epidemic (disease of the poor)
-Increased risk with antacid tx
Pathogenesis: similar to ETEC - Secrete AB choleragen: LT toxin (heat‐labile), increase cAMP, increase Cl‐ & H2O secretion
-No invasion of epithelial cells
Symp: "rice water diarrhea & SEVERE dehydration"
‐similar to ETEC
Tx: rehydration to correct electrolytes: Ringer's Lactate (10% loss of body weight => death) |
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Term
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Definition
Normal flora of shellfish
1st cause of diarrhea in Japan
Virulence:
Enterotoxin → small bowel inflammation
Hemolysin → β hemolysis
Type III secretion system → inject bacterial proteins directly into host cells |
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Term
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Definition
Necrotizing fasciitis: hemorrhagic bullae
Risk factors: immunocompromised pt eating oyster or swimming in brackish water
Tx: surgical debridement & antibiotics (penicillin + clindamycin) |
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Term
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Definition
• Characteristics: Intermediate‐dose pathogen (food & water)
Comma shaped gram‐neg rod w/ bipolar flagellae
Microaerophilic, grow best at 42 degrees
Zoonotic: chicken
• Pathogenesis: -Invade epithelial cells, disseminate in blood => bacteremia -Secrete LT enterotoxin
Flagellae promote motility
Cytolethal distending toxin inhibits innate immunity
High molecular weight plasmid (pVir) enhances invasiveness
PEB1 antigen (surface protein)
Adhesin → colonization, invasion
immunodominant → proposed vaccine antigen
•Symp: fever, bloody diarrhea, abdominal pain (after eating uncooked chicken)
• Infections: Acute enteritis (1st cause of bloody diarrhea in US)
Acute colitis (usually confused w/ Crohn's)
IMPORTANT: 40% precede Guillain‐Barre Syndrome
•Tx: fluid/electrolyte replacement, antibiotics (Azithromycin) |
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Term
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Definition
• Characteristics:
Normal gastric colonizer
Secrete urease to split urea to NH3 & alkalinize stomach
CagA gene is highly associated with gastric cancer & duodenal cancer
VacA gene is immunosuppressive & downregulates T cells
• Dz:
Peptic ulcer: 90% due to H. pylori
Gastric cancer: atrophic gastritis MALT lymphoma (B‐cell): H. pylori infection is highly associated with MALT lymphoma
•Tx: PPI + double coverage of antibiotics, Pepto‐Bismol inhibit growth of H. pylori |
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Term
| "Non‐fermenting" Gram‐negative rods (NFGNB) characteristics |
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Definition
•Oxidase positive, lactose negative non‐fermenters
•Common environmental isolates (NOT usually found in humans but frequent human colonizers in hospital)
•Involved with nosocomial infections (healthcare associated infections): major killer in hospitals
•Have low inherent virulence but opportunistic in Immunocompromised pts •Live in harsh environment and highly resistant to antibiotics (efflux pumps, rapid mutations)
•Never try to sterilize NFGNB pts as treating benign colonizers is impossible |
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Term
| Risk factors for acquiring NFGNB |
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Definition
•Contact with healthcare system (ICU)
•Broad‐spectrum antimicrobial recipient (killing of normal gut flora)
•Immunocompromised state: neutropenia, cancer
•Breakdown of native defense: catheter, surgery, ventilation, burns
•Breakdown of infection ctrl practices: transmission via water, food, hands in hospital |
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Term
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Definition
Stenotrophomonas maltophilia
Pseudomonas aeruginosa
Acinetobacter species
Burkholderia cepacia complex |
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Term
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Definition
Classic PA infections: ventilator‐associate pneumonia, catheter‐related bacteremia & UTI, post‐burn infection,
neutropenia (killed off by broad‐spectrum antibiotics), CFTR (NM: BE PSEUDO)
OBLIGATE AEROBE that loves WATER (hot tub folliculitis)
PA produces slimes (biofilm or microcapsule) to stick to catheters
PA is a major cause of resp failure & death in CF pts with chronic lung dz (know this!)
Treatment of PA: pipericillin, ceftazidime, cefepime, imipenem, gentamicin, cipro (resistance = efflux pump)
For Pseudomonas, think of water, slime, blue‐green pigment, CF, burn victims, catheter, tennis shoes, hospital |
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Term
| Stenotrophomonas maltophilia |
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Definition
SM is low virulence & true colonizer
SM: colonizer > infection, catheter/ventilator (plastics) bacteremia
Inherent carbapenem resistance: increases prevalence of SM with increasing carbapenem use (know this!)
Rare in Ben Taub, common in MD Anderson (due to cancer & carbapenem use) Treatment of SM: take out the catheters! |
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Term
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Definition
AB is genetically plastic and resistant to nearly all antibiotics (may have to use polymyxin)
AB is a ubiquitous colonizer & common blood contaminant
AB: colonization > infection, ventilator‐pneumonia, catheter‐bacteremia
Treatment of AB: prevention
-For Steno & Acineto, since the bugs themselves are colonizers & have low pathogenicity, how sick the host is will determine the likely outcome of the nosocomial infection |
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Term
| Burkholderia cepacia complex |
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Definition
BCC is used by agro‐industry, but causes disease mainly in CF & CGD pts (non‐nosocomial related) (know this!) BCC: ranges from asymptomatic to granulomatous pneumonia in CF pts
BCC: #2 cause of death (pneumonia) in chronic granulomatous dz (CGD) pts after Aspergillus
Treatment of BCC: prevention
-For BCC, think of agriculture, CF & CGD |
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Term
| Gram‐negative zoonotic rods |
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Definition
Common characteristics:
•Gram‐negative rods
•Cause zoonotic diseases: disease in vertebrate animal that can be directly transmitted to man
•Very virulent
•Intracellular organisms (except Pasteurella)
•Dx: serology (antibody), recall antigen skin test (PPD‐like)
•Prozone effect (know this!): lack of agglutination at high concentrations of antibodies (low titer) due to an excess of antibodies => false negative serology results
•Tx: doxycycline, gentamicin (AG) Common risk factors:
•People who handle animals
•People exposed to arthropods
•People exposed to unprocessed food •Travelers |
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Term
| Gram‐negative zoonotic rod members |
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Definition
Rickettsia, Ehrlichia
Pasteurella & Capnocytophagia
Brucella (brucellosis)
Francisella tularensis
Yersinia pestis |
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Term
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Definition
Clinical case: pt with recent camping trip to Missouri presents with fever, headache & rash (the triad of Rickettsia)
Risk factors: camping or hiking in NC, SC, TN, OK
Transmission: ticks (both vector & reservoir)
Diseases & differentials:
-Rocky Mountain Spotted Fever (RMSF): Rickettsia infects endothelium
Tick bite 1 wk ago => fever & headache => vasculitic rash starts from palms & soles and spreads to trunks
=> tx w/ doxycycline
- HME/HGA: Ehrlichia infects WBCs Tick bite 1 wk ago => fever & headache => no rash but severe leukopenia => tx w/ doxycycline
- Others: Rickettsial pox, Q fever, Typhus Dx: serology
Tx: doxycycline (doxycycline is ID doc's best friend as it treats all the weird & difficult‐to‐dx zoonotic infections!) |
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Term
| Pasteurella & Capnocytophagia |
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Definition
Clinical case: pt who is an alcoholic just had various cat bites
Risk factors: splenectomy, alcoholism (liver cirrhosis)
Transmission: normal oral colonizers of cats & dogs
Diseases:
- Skin & soft tissue infections (necrotizing fasciitis) after cat/dog bite
-Septic arthritis/osteomyelitis in high‐risk pts (asplenic or cirrhotic) Dx: guess
Tx: ampicillin + sulbactam (Unasyn) [this is NOT an intracellular bug, so Unasyn is sufficient] - For Pasteurella the Cat & Capnocytophagia the Dog, think of animal bites in alcoholics |
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Term
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Definition
Clinical case: pt ate unpasteurized goat cheese presents with 1 mo of "fever of unknown origin" w/o any skin lesions
Risk factors: meat‐packing industry workers, farmers, vets, travelers who eat unpasteurized dairy products Transmission: hooved animals (horse, goat, sheep, think of animals in Mongolia)
Diseases: the Great Imitator (undulant fever with generalized symps: chill, sweat, backache, etc)
Bugs to know:
-B. abortus ‐ cow
-B. suis ‐ pig
-B. melitensis ‐ goat
Dx: serology
Tx: Doxycycline |
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Term
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Definition
Clinical case: pt with lots of "bites" during hiking in Oklahoma presents with ulcerated lesion on neck with lymphadenopathy
Risk factors: hunters, trappers, farmers, vets in OK, KS, MO, AR Transmission: Francis the rabbit via ticks
Diseases:
-Ulceroglandular tularemia (fever with ulcer)
-Pneumonic tularemia
Dx: serology, highly contagious, must warn lab!
Tx: cipro
-For Francisella the rabbit, think of rabbit & tick bites in the Southcentral US states & fever with skin ulcer & lymph node swelling |
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Term
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Definition
Clinical case: pt from flea‐infected household presents with bubo (swelling of lymph nodes in the groin) in NM Risk factors: hunters, trappers, rodent/flea exposure in endemic areas (AR, NM, CA)
Transmission: rodents via fleas Bubonic plague:
Carried by rodents, transferred by flea (vector)
Proliferation of bug in lymph nodes
Symp of "black death": fever, bubo, septicemia (DIC), black skin necrosis
Pneumonic plague: Transmitted by inhalation
Bug from blood invade lung => pneumonia & hemorrhagic pulmonary failure Coughing => aerosol transmission
Dx: Wayson stain: bipolar "safety‐pin" staining gram negative rods, serology, highly contagious, must warn lab!
Tx: gentamicin
-For bipolar pestis, think of flea bites in the Southwestern states & fever with bubo (painful swollen lymph nodes in groin) & black skin necrosis |
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Term
| Nonstainable "atypical" bacteria characteristics |
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Definition
Legionella, Mycoplasma, Chlamydia (LMC)
Atypical pathogen, lack usual cell wall, no gram stain, IMPOSSIBLE to culture
•Intracellular bugs: not susceptible to cell‐wall active antibiotics (beta‐lactam)
•Tx (atypical bugs): azithromycin (macrolides), cipro (quinolones), tetracycline
•Atypical "walking" pneumoniae:
Pneumonia that doesn't respond to penicillin
Mycoplasma is the most common cause but LMC can all cause it
Manifestation: diffuse non‐lobar pneumonia |
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Term
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Definition
• Characteristics:
Lack usual cell wall, facultative intracellular bug
Live in amoebas in warm water source (disease of technology via aerosol) Causes sudden outbreak of infections: Legionnaires & Pontiac fever
• Dz: Legionnaire's disease:
-Pneumonia: recent travel history
-Extra‐pulmonic manifestations: CNS, liver - Pt lacking cellular immunity at risk: age, GC, DM
Pontiac fever:
-Flu‐like illness: fever, myalgia, headache, resolves in days
•Dx: sputum direct fluorescent antibody (DFA) test & urinary antigen test Tx: azithromycin (macrolide), cipro (quinolone) or tetracycline, NOT beta‐lactams |
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Term
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Definition
• Characteristics:
Mycoplasma pneumoniae, Ureaplasma urealyticum
Lack usual PTG cell wall (contain cholesterol), ubiquitous colonizers Smallest free‐living virus‐like organism
Cause URI & atypical pneumoniae (M. pneumoniae), genital diseases (U. urealyticum) & autoimmune problems Close confine transmission
• Dz:
Atypical pneumonia & URIs (Mycoplasma pneumoniae): - Walking (non‐severe) pneumonia: pronounced cough, patchy lung infiltrates (X‐ray looks worse than pt)
Genital diseases (Ureaplasma urealyticum): - Has urease that splits urea into NH3 (just like Proteus) - Urethritis & PID
Autoimmune dz:
-Cold agglutinin disease (IgM against RBCs): necrosis of extremities - Weird rashes: erythema multiforme or Stevens‐Johnson syndrome
•Dx: cold agglutinin test at 4 degrees (DMM will kill you if you use serology for dx Mycoplasm)
•Tx: azithromycin (macrolide), cipro (quinolone) or tetracycline, NOT beta‐lactams |
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Term
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Definition
• Characteristics:
OBLIGATE intracellular bug (Rickettsiae & Chlamydia are the only 2 obligates) Unique life cycle:
-Elementary body that Enters cell via endocytosis
-Reticulate body that Replicates in cell via fission
Leading cause of ocular trachoma, STD (C. trachomatis) & atypical pneumonia (C. pneumoniae, C. psittacosis)
• Dz: Ocular trachoma & STDs (C. trachomatis): personal transmission
-Ocular trachoma: corneal opacity & blindness
-Lymphogranuloma venereum (LGV): painful genital ulcer & pussy node - Urethritis: painful urination with thick discharge
-PID: "PID shuffle" & "Chandelier sign" may lead to infertility
-Neonatal conjunctivitis
Atypical pneumoniae (C. pneumoniae): aerosol transmission
-Walking pneumonia: TWAR agent
Psittacosis (C. psittaci): bird transmission
-Psittacosis: multisystem zoonosis (broad‐spectrum of dz)
•Dx: DNA probes (differentiate Chlamydia from gonococcus) (DMM will kill you if you use serology for dx Chlamydia)
•Tx (C. trachomatis, C. pneumoniae): azithromycin (macrolide), cipro (quinolone) or tetracycline, NOT beta‐lactams
•Tx (C. psittaci): doxycycline (use doxycycline for ANY weird zoonotics) |
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