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Bacterial Pathogens and Clinical Microbiology Reference

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Bacterial Pathogens and Clinical Characteristics

Streptococcus pyogenes

  • Features: Gram-positive, unmovable, capsules, protamine, hemolysate, hyaluronic acid, disseminated erythrogenic toxin (scarlet fever), alpha-Dick, endocardial, anti-streptolysin O ("A").
  • Treatment: Penicillin.

Streptococcus pneumoniae

  • Features: Gram-positive, negative capsules, causes pneumonia, sinusitis, meningitis. Blood agar culture, optochin, bile solubility, Quellung reaction.
  • Treatment: Penicillin.

Mycobacterium tuberculosis

  • Features: Ziehl-Neelsen stain, strictly aerobic, intracellular, cord factor, niacin positive, Löwenstein-Jensen medium. Tuberculosis: susceptible, Mantoux test positive (current).

Staphylococcus aureus

  • Features: Gram-positive, facultative anaerobic, food intoxication, osteomyelitis, sepsis, coagulase positive, necrosis toxin from coagulase test, Vogel-Johnson agar.
  • Treatment: Cloxacillin.

Mycobacterium leprae

  • Features: Globio, skin/hair involvement. Lepromatous leprosy: lepromin negative. Tuberculoid leprosy: nerves, skin lesions, positive lepromin (Fernandez-Mitsuda test), armadillo model.
  • Treatment: Dapsone, BCG vaccine.

Panchatantra / Blood Bacillus

  • Features: Blood-borne bacillus.

Salmonella

  • Features: Red plaque, peritrichous flagella bacilli, high motility, blood culture (bright green after 1 week), urine culture, stool culture (2nd week), Kauffmann-White classification, Widal test, deoxycholate citrate agar, tip identification.

Shigella

  • Features: Foodborne transmission, endotoxin, dysentery, fever, tenesmus, diarrhea, stool culture, desoxycholate citrate agar.
  • Treatment: Ampicillin.

Yersinia pestis

  • Features: Encapsulated bacilli, lymph node involvement, bubonic plague, pneumonia, sepsis.
  • Treatment: Tetracycline.

Bacillus Species

  • Features: Motile flagella, 1-3 days incubation, serial layers, peptone broth.
  • Treatment: Tetracycline.

Proteus Species

  • Features: Nosocomial bacillus.
  • Treatment: Cephalosporins.

Klebsiella Species

  • Features: Bacillus, lung disease, Rhinoscleroma (Koss). Diagnostic criteria: greater than 100,000 bacteria per milliliter.

Neisseria gonorrhoeae

  • Features: Diplococcus, aerobic, fastidious, endotoxic, urethritis with purulent secretion, ophthalmia neonatorum, Thayer-Martin medium.
  • Treatment: Penicillin.

Haemophilus ducreyi

  • Features: Soft chancre, coccobacillus, Martin broth.
  • Treatment: Erythromycin, Ceftriaxone.

Chlamydia trachomatis

  • Features: Intracellular, inclusion bodies, urethritis, lymphogranuloma venereum, Frei test.
  • Treatment: Tetracyclines.

Treponema pallidum (Spirochetes)

  • Features: Microaerophilic or anaerobic, axial filaments, disseminated via lymphatics. Syphilis: 1st stage (hard chancre), 2nd stage (condyloma lata), 3rd stage (gumma). Hypersensitivity. VDRL, Wassermann, FTA-ABS confirmation, direct immunofluorescence, silver impregnation staining.
  • Treatment: Penicillin.

Neisseria meningitidis

  • Features: Capsule, endotoxin, oxidase positive, indophenol, cerebrospinal fluid (CSF), Thayer-Martin medium, CO2 requirement.
  • Treatment: Profsulfonamides.

Diplobacillus

  • Features: Meningitis, encapsulated, chocolate agar.
  • Treatment: Cephalosporins, DTP vaccine.

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