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.
Chlamydophila pneumoniae and Chlamydophila
psittaci Disease
Both cause atypical pneumonia; transmitted by aerosol.
C psittaci—has an avian reservoir (parrots)
Chlamydiae diagnosis and treatment
Lab diagnosis: PCR, nucleic acid amplification test. Cytoplasmic inclusions (reticulate bodies) seen on Giemsa or fluorescent antibody– stained smear.
Treatment: azithromycin (favored because onetime
treatment) or doxycycline (+ ceftriaxone for possible concomitant gonorrhea).
Chlamydia trachomatis serotypes
Types A, B, and C
Chronic infection, cause blindness due to follicular conjunctivitis in Africa.
ABC = Africa, Blindness, Chronic infection.
Chlamydia trachomatis serotypes
D–K
Urethritis/PID, ectopic pregnancy, neonatal pneumonia (staccato cough) with eosinophilia, neonatal conjunctivitis (1–2 weeks after birth).
D–K = everything else.
Neonatal disease can be acquired during passage through infected birth canal.
Chlamydia trachomatis serotypes
Types L1, L2, and L3
Lymphogranuloma venereum—small, painless ulcers on genitals swollen, painful inguinal lymph nodes that ulcerate (buboes).
Treat with doxycycline.
Zoonotic bacteria disease and vector:
- Anaplasma spp.
- Bartonella spp.
- Borrelia burgdorferi
- Borrelia recurrentis
- Brucella spp.
- Campylobacter
- Anaplasmosis, Ixodes ticks (live on deer and mice).
- Cat scratch disease, bacillary angiomatosis Cat scratch
- Lyme disease, Ixodes ticks (live on deer and mice)
- Relapsing fever, Louse
- Brucellosis/undulant fever, Unpasteurized dairy
- Bloody diarrhea, Feces from infected pets/animals; contaminated meats/foods/hands.
Zoonotic bacteria disease and vector:
- Chlamydophila psittaci
- Coxiella burnetii
- Ehrlichia chaffeensis
- Francisella tularensis
- Leptospira spp.
- Mycobacterium
- Psittacosis Parrots, other birds
- Q fever, Aerosols of cattle/sheep amniotic fluid
- Ehrlichiosis, Amblyomma (Lone Star tick)
- Tularemia, Ticks, rabbits, deer flies
- Leptospirosis, Animal urine in water; recreational water use.
- leprae Leprosy Humans with lepromatous leprosy; armadillo (rare).
Zoonotic bacteria disease and vector:
- Pasteurella multocida
- Rickettsia prowazekii
- Rickettsia rickettsii
- Rickettsia typhi
- Salmonella spp. (except S typhi)
- Yersinia pestis
- Cellulitis, osteomyelitis, Animal bite, cats, dogs
- Epidemic typhus, Human to human via human body louse
- Rocky Mountain spotted fever, Dermacentor (dog tick)
- Endemic typhus, Fleas
- Diarrhea (which may be bloody), vomiting, fever, abdominal cramps, Reptiles and poultry.
- Plague, Fleas (rats and prairie dogs are reservoirs)
Rickettsial diseases and vector-borne illnesses Treatment:
doxycycline (caution during pregnancy; alternative is chloramphenicol).
Rocky Mountain spotted fever
Rickettsia rickettsii, vector is tick. Occurs primarily in the South Atlantic states, especially North Carolina.
Rash typically starts at wrists and ankles and then spreads to trunk, palms, and soles.
Classic triad—headache, fever, rash (vasculitis).
Typhus
Endemic (fleas)—R typhi.
Epidemic (human body louse)—R prowazekii.
Rash starts centrally and spreads out, sparing palms and soles. “Rickettsii on the wRists, Typhus on the Trunk”
Palms and soles rash is seen in
Coxsackievirus A infection (hand, foot, and mouth disease), Rocky Mountain spotted fever, and 2° Syphilis
(you drive “CARS” using your palms and soles).
Ehrlichiosis
Ehrlichia, vector is tick. Monocytes with morulae (mulberry-like inclusions) in cytoplasm.
MEGA berry—
Monocytes = Ehrlichiosis
Granulocytes = Anaplasmosis
Ehrlichiosis: Agent, vector, characteristics
Ehrlichia, vector is tick. Monocytes with morulae (mulberry-like inclusions) in cytoplasm.
MEGA berry—
Monocytes = Ehrlichiosis
Granulocytes = Anaplasmosis
Anaplasmosis: Agent, vector, characteristics
Anaplasma, vector is tick. Granulocytes with morulae in cytoplasm.
Q fever: Agent, vector/transmission, diesease
Coxiella burnetii, no arthropod vector. Spores
inhaled as aerosols from cattle/sheep amniotic fluid.
Presents as pneumonia. Common cause of culture ⊝ endocarditis.
Q fever is Queer because it has no rash or vector and its causative organism can survive outside in its endospore form. Not in the Rickettsia genus, but closely related.
Mycoplasma pneumoniae Disease
Classic cause of atypical “walking” pneumonia (insidious onset, headache, nonproductive cough, patchy or diffuse interstitial infiltrate).
High titer of cold agglutinins (IgM), which can agglutinate
RBCs. Grown on Eaton agar.
Mycoplasma pneumoniae Treatment
macrolides, doxycycline, or fluoroquinolone (penicillin ineffective since Mycoplasma have no cell wall).