Microbiology- Clinical Bacteriology (Others) Flashcards
Spirochetes and stains
Includes Borrelia (big size), Leptospira, and Treponema.
Only Borrelia can be visualized using aniline dyes (Wright or Giemsa stain) in light microscopy due to size.
Treponema is visualized by dark-field microscopy or direct nfluorescent antibody (DFA) microscopy.
Lyme disease Vector and agent
Caused by Borrelia burgdorferi, which is transmitted by the Ixodes deer tick (also vector for Anaplasma spp. and protozoa Babesia). Natural reservoir is the mouse.
FACE: Facial nerve palsy (typically bilateral) Arthritis Cardiac block Erythema migrans
Stages of lyme disease
Stage 1—early localized: erythema migrans (typical “bulls-eye” configuration is pathognomonic but not always present), flu-like symptoms.
Stage 2—early disseminated: secondary lesions, carditis, AV block, facial nerve (Bell) palsy, migratory myalgias/transient arthritis.
Stage 3—late disseminated: encephalopathy,
chronic arthritis.
Lyme disease Treatment
Treatment: doxycycline (1st line); amoxicillin
and cefuroxime in pregnant women and
children.
Leptospira interrogans
- Leptospirosis
- Weil disease
found in water contaminated with animal urine.
- flu-like symptoms, myalgias (classically of calves), jaundice, photophobia with conjunctival suffusion (erythema without exudate). Prevalent among surfers and in tropics (eg, Hawaii).
- (icterohemorrhagic leptospirosis)—severe form with jaundice and azotemia from liver and kidney dysfunction, fever, hemorrhage, and anemia.
Primary syphilis
Localized disease presenting with painless chancre. If available, use dark-field microscopy to visualize treponemes in fluid from chancre. VDRL ⊕ in ~ 80%.
Secondary syphilis
Disseminated disease with constitutional symptoms, maculopapular rash (including palms and soles), condylomata lata (smooth, painless, wart-like white lesions on genitals), lymphadenopathy, patchy hair loss; also confirmable with dark-field microscopy.
Serologic testing: VDRL/RPR (nonspecific), confirm diagnosis with specific test (eg, FTA-ABS).
Tertiary syphilis
Gummas (chronic granulomas), aortitis (vasa vasorum destruction), neurosyphilis (tabes dorsalis, “general paresis”), Argyll Robertson pupil (constricts with accommodation but is not reactive to light; also called “prostitute’s pupil” since it accommodates but does not react).
Signs: broad-based ataxia, ⊕ Romberg, Charcot joint, stroke without hypertension.
For neurosyphilis: test spinal fluid with VDRL, FTA-ABS, and PCR.
Congenital syphilis
Presents with facial abnormalities such as rhagades (linear scars at angle of mouth), snuffles (nasal discharge), saddle nose, notched (Hutchinson) teeth, mulberry molars, and short maxilla; saber shins; CN VIII deafness.
To prevent, treat mother early in pregnancy, as placental transmission typically occurs after first trimester
VDRL false positives
“false-Positive results on VDRL with:”
Pregnancy Viral infection (eg, EBV, hepatitis) Drugs Rheumatic fever Lupus and leprosy
Jarisch-Herxheimer reaction
Flu-like syndrome (fever, chills, headache, myalgia) after antibiotics are started; due to killed bacteria (usually spirochetes) releasing toxins.
Gardnerella vaginalis Characteristics, disease
A pleomorphic, gram-variable rod involved in bacterial vaginosis. Presents as a gray vaginal discharge with a fishy smell; nonpainful (vs vaginitis).
Gardnerella vaginalis Diagnosis and Treatment
Clue cells (vaginal epithelial cells covered with Gardnerella) have stippled appearance along outer margin.
Amine whiff test—mixing discharge with 10%
KOH enhances fishy odor.
Treatment: metronidazole or clindamycin.
Chlamydiae Forms
2 forms:
- Elementary body (small, dense) is “Enfectious” and Enters cell via Endocytosis; transforms into reticulate body.
- Reticulate body Replicates in cell by fission; Reorganizes into elementary bodies.
Chlamydia trachomatis Disease
Causes reactive arthritis (Reiter syndrome), neonatal and follicular adult conjunctivitis, nongonococcal urethritis, and PID.
