E. coli

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Microscopy: gram neg, lactose fermenting

Pathogenesis: adhesins, exotoxins (heat stable & heat labile)

Transmission:

Disease: Gastroenteritis (exogenous)

Symptoms: watery diarrhea (may be bloody), nausea, cramps, vomiting possible

Treatment:

Disease: UTI (endogenous)

Pathogenesis: adhesins + hemolysins = inflamation

Symptoms:

Treatment:

Disease: Sepsis (most common gram neg rod)

Disease: Neonatal Meningitis

Pathogenesis: capsule

Salmonella

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Microscopy: gram neg rod, facultative anaerobe

Transmission: contaminated food

Disease: Salmonellosis (enteritis)

Symptoms: inflammation, fluid secretion (diarrhea)

Pathogenesis: invade M cells in ileum, high ID50

Transmission: zoonotic

Complications: bacteremia

Treatment: self limiting (< 1 wk)

Microscopy: gram neg rods

Transmission: fecal/oral (primarily children)

Pathogenesis: ID50 ~200, shiga toxin (inhibits protein synthesis)

Disease: Shigellosis (gastroenteritis, dysentery)

Symptoms: bloody diarrhea (invade M cells in colon, damage epithelium); inflammation (leukotaxis contribute to damage); cramps, fever, diarrhea, hemorrhage w/in 3 days

Yersinia pestis

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• Microscopy: gram neg rods
• Disease: Plague
• Transmission: vector (fleas), animal reservoir
• Pathogenesis: virulence factors (avoid phagocytosis, inactivate complement, break down fibrin clots) = rapid spread
• Treatment: Streptomycin
• Symptoms:
• Bubonic plague: black hemorrhagic lymph nodes, tissue necrosis
• Pneumatic plague: highly contagious,  100% mortality

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• Microscopy: Gram-negative rods
• Symptoms: subcutaneous nodules that later form painless genital lesions
• Transmission: STD
• Pathogenesis: Intracellular replication; capsule; formation of granuloma
• Treatment: Tetracycline, erythromycin, sulfa/trimethoprim

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• Disease: Gastroenteritis
• Transmission: contaminated food/water
• Symptoms: cramps, diarrhea, fever, pain (1-2 wks)

• Disease: Typhoid fever
• Symptoms: fever, headache, myalgia, malaise
• Pathogenesis: Low ID50; intracellular (enter macrophages, spread to liver, spleen, bone marrow); reinfect GI tract through gallbladder
• Transmission: human reservoir
• Treatment: Ciprofloxacin

Pseudomonas aeruginosa

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• Microscopy: Gram-negative obligate aerobes, oxidase-positive
• Pathogenesis: Opportunistic pathogens,
• Virulence factors: elastase, protease,  phospholipase, pyocyanin (green-blue pigment, release of IL-8, inflammation, tissue damage), capsule (cystic fibrosis), Exotoxin A (inh. protein synthesis); Exoenzymes S & T
• Antibiotic resistance
• Diseases
  • Pneumonia (can be necrotizing)
  • Skin infections (burn wounds, ecthyma gangrenosum, folliculitis)
  • UTI (catheterized patients)
  • Swimmer's ear (otitis externa)

Bordetella pertussis

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• Microscopy: Gram-negative coccobacilli
• Symptoms: Cold-like for 1-2 weeks, then whooping cough paroxysms for 2 - 4 weeks.
• Transmission: Aerosol
• Complications: Systemic effects of toxins possible
• Pathogenesis: Pertussis toxin activates AC; cytotoxins kill ciliated epithelial cells
• Treatment: supportive (antibiotics ineffective); vaccine (DPT)

Francisella tularensis

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• Microscopy: Gram-negative coccobacilli
• Symptoms: Depending on site of infection: skin ulcer, pneumonia, systemic multi-organ infection
• Transmission: direct contact with wild animals, tick bites (zoonotic)
• Complications: High mortality if not recognized (e.g. pneumonia and systemic)
• Pathogenesis: Intracellular pathogen, localized inflammation
• Treatment: Streptomycin

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Brucella spp.

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• Microscopy: Gram-negative rods
• Transmission: Direct contact with animal reservoir (zoonotic)or contaminated food (zoonotic) ID50 = 10 - 100 bacteria
• Symptoms: Initial symptoms are non-specific (malaise, chills, sweats, fatigue etc)
• Complications: Recurring fever, GI symptoms, chronic infection
• Pathogenesis: Intracellular pathogens (macrophages & monocytes) - cause granulomas in spleen, liver, kidney, lymph nodes
• Treatment: tetracycline, doxycycline

• Fastidious Gram-negative rods
• Capsule + virulence factors = damage to respiratory epithelium
• Translocation across epithelium can lead to bacteremia
• Childhood vaccine cut pediatric infections
  • Otitis and sinusitis: H. influenzae b (Hib)
  • Meningitis (pediatric): Hib
  • Epiglottitis: life-threatening; Hib
  • Otitis, sinusitis, respiratory tract infection: non-encapsulated H. influenzae
  • Brazilian purpuric fever: Starts with conjunctivitis; if untreated, often fatal (shock)

Haemophilus ducreyi

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• Cause: Haemophilus ducreyi
• Microscopy: Gram-negative rods
• Symptoms:  painful ulcerating genital lesion after ~7 - 9 days
• Transmission: Sexual (STD)
• Treatment: cephalosporin, azithromycin, ciprofloxacin

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Legionella pneumophila

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• Microscopy: Gram-negative rods; pleomorphic in culture
• Symptoms: fever, chills, myalgia, headache.
• Transmission: Inhalation from contaminated water source
• Complications: severe Legionnaire's disease (Fever, chills, cough, headache, multiorgan disease, pneumonia), mild (Pontiac fever)
• Pathogenesis: Intracellular replication
• Treatment: Azithromycin, ciprofloxacin

Bartonella henselae

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• Microscopy: Gram-negative short rods
• Transmission: Flea vector or direct contact with infected animal (zoonotic)
• Symptoms: Sore at infection site; fever, local lymphadenopathy
• Complications: bacteremia
• Pathogenesis: Intracellular pathogen: Penetration of bacteria into RBCs and endothelial cells; inflammation of local lymph nodes
• Treatment: does not respond to antibiotics

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• Microscopy: Gram-negative short rods
• Transmission: Vector = Human body louse (human reservoir)
• Symptoms: Headache, fever, weakness, severe pain in long bones (tibia). Fever may recur at 5 day intervals
• Complications: Bacillary angiomatosis and endocarditis in immunocompromised
• Pathogenesis: Intracellular pathogen: Invasion of RBCs and vascular endothelial cells
• Treatment: broad spectrum antibiotics (gentamycin, erythromycin)

• Carrion disease/Oroya fever (acute stage)/Bartonellosis
• Microscopy: Gram-negative short rods
• Transmission: Sandfly vector from animal reservoir (zoonotic)
• Symptoms: Sore at bite site; fever, myalgia, arthralgia, headache, severe anemia; verruga (chronic stage): skin pustules
• Pathogenesis: Intracellular pathogen: Penetration of bacteria into RBCs destroys them, causing anemia. Immune response (endotoxin release) causes symptoms as well
• Treatment: difficult; broad=spectrum antibiotics

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• Nosocomial infections (B. cepacia)
• Melioidosis (B. pseudomallei) - bioterror threat

• Microscopy: Gram-negative coccobacilli
• Symptoms:
• Transmission: Environmental, often introduced during battle trauma (Iraq war)
• Complications: septicemia & death
• Pathogenesis: Multiple drug resistance
• Treatment: cephalosporin or Imipenem + aminoglycoside

• Microscopy: Gram-negative rods
• Symptoms:  Wound infections: redness, swelling
• Transmission: wound contact with contaminated water
• Complications: Bacteremia
• Pathogenesis: Aeromonas possesses virulence factors (proteases, siderophores, hemolysins)
• Treatment: Ciprofloxacin

• Gastroenteritis

• Rat-bite fever
• Haverhill fever (contaminated food, water, milk, turkey)

• Obligate anaerobes; resident microbes
• Respiratory tract, brain abscesses, abdominal infections
• Periodontal disease