6 Flashcards
What do mycobacteria cause? Why cant gram stain be used?
tuberculosis and leprosy
waxy coat and resistant to disinfectant and it resist decolorization
what special staining method is used?
ZIEHL-NEELSEN
what is mycobacterium tuberculosis
acid fast bacillus causes chronic, slowly progressing, pulmonary infection
what is the first stage of tuberculosis?
Primary tuberculosis
steps for Ziehl neelsen staining
- Ziehl-Neelsen carbol fuchsin to the slide for five minutes while applying heat.
- Follow with a gentle wash with water to cool the slide.
- Acid alcohol is now added to decolorize the slide.
- Wash the slide in water again and counterstain with methylene blue for 1-2 minute
how long does it take to see mycobacterium tuberculosis on a Lowenstein Jensen medium
4-6 weeks
how many people does mycobacterium tuberculosis affect
1.7 billion/year
what happens in primary tuberculosis
- Aerosol inhalation
2.Bacteria multiplication in alveoli
3.Macrophage ingestion of bacilli and formation of 1º complex
4.Foci of infection in lungs (may be spread to kidneys, bones, meninges) - 6 weeks CMI is fully active, infection is stopped
(majority of cases)
6.Some bacilli survive, reactivation several years later
what is the second stage of mycobacterium tuberculosis
- Late reactivation of lesions in lungs, kidneys, bones etc
- 5% of cases; higher in patients with AIDS
3.Chronic infection
immunity in tuberculosis
CMI is most important (T-cells)
-tuberculin solution injected intradermally (wait 48-72 hrs)
-mantoux test
-record diameter >10mm (positive), 5-9 (doubtful), <4mm Negative)
-poisitve dont mean active
What is atypical mycobacteria? it has a higher ______. how does it affect the Mantoux test
Occasionally isolated from patients with chronic pulmonary disease indistinguishable from TB (M. kansassi, M. avium, M. intracellulare)
-resistance to anti-tb drug
-gives doubtful Mantoux test
whats tehe difference between M.marinum and M fortuitum
M. marinum: skin infections
* M. fortuitum: soft tissue abscesses
all atypical mycobacterium infections are typically seen in
the elderly
veterans
immune-comprimised
city people
immune-comprimised
what does mycobacterium leprae cause? how many kinds are there? whats the name?
-leprosy
-2 kinds
tuberculoid leprosy and lepromatous leprosy
is myobacteriumrarely found found in developed countries or undeveloped
developed
what is Tuberculoid leprosy:
visible nerve enlargement,
few erythmatous plaques, few bacilli in infected
tissues, but many lymphocytes and granulomas;
low infectivity
Lepromatous leprosy
no visible nerve
enlargement, many erythromatous nodules, many
bacilli in infected tissue; high infectivity
epidemiology of mycobacterium liprae
not common in North America, mostly seen in Asia and Africa
-between 1-2 million cases currently reported worldwide; only 125 new cases seen in US each
year.
-transmission is primarily human to human through respiratory droplets; in some rare cases
transmission occurs through an animal reservoir (armadillos).
how is the diagnoses for mycobacterium leprae
microscopy is used for the lepromatous diagnosis, but not for the tuberculoid form since so
few bacilli are present; skin testing is used for the tuberculoid form
what are the 3 types of spirochetes
Treponema causing syphilis, yaws, pinta
Leptospira causing leptospirosis
Borrrelia causing relapsing fever, known as Lyme disease
what causes syphillis
T.pallidum
-STI
what is primary syphillis?
Appearance of chancre 3-4 weeks after infection
* Fluid from lesion contains bacteria seen under
dark-field microscopy
Secondary syphilis
- 6 weeks after appearance of chancre
- Generalized or local rash
- Mucosal lesions with many treponemes
Latent syphilis
No symptoms of infection
* Non-transmittable after 4 years
* BUT congenital infection may occur
Late syphilis
Obliterative endarteritis
* Can involve skin, mucosae, nervous system,
cardiovascular system and tissues
what testing is used to diagnose syphilis
serology testing
what happens during Non-treponemal tests
Non-specific: use cardiolipin asantigen
* Screening
* Positive in early stages
(VDRL, RPR, Wassermann)
Treponemal tests
- Specific: Use treponemal
extracts - FTA-ABS: Flourescent
Treponemal Antibody Absorption - MHA-TP: Microhemagglutination
of T.pallidum
Used to confirm positive VDRL
what does borrelia burgdorferi cause? how? what does it affect? where is it common or uncommon? how to diagnose it?
Lyme disease
* Tick bites
* Affects skin, joints, nervous system and heart
* Common in US, rare in Canada
* Use serology for diagnosis (ELISA)
why cant a microscope be used for diagnoses? when would a serology test be ineffective?
organism is very difficult to see under microscope
* difficult to culture
* Serology does not give +ve result in first 2-4 weeks
of infection
what is the treatment for lyme disease?
Doxycycline, amoxicillin, cefuroxime for early
disease
* For neurological and musculoskeletal
manifestations, undergo prolonged treatment
what is the prevention for lyme disease?
avoid ticks and wear protective clothing in woods
(long sleeves and pants)
* Vaccine available: ospA antigen of organism
what is Chylmydae
small bacteria (cocci)which are obligate intracellular energy parasites
They have a unique life cycle with 2 forms: infectious
elementary body (300-400 nm) and reticulate body (800-1000 nm).
what can NOT be done to chylmadie
- Can NOT make their own ATP or other energy
intermediates - Can NOT be grown on artificial media
Life cycle has 2 forms:
Elementary body (300-400 nm)
– Infectious form
– No growth or replication
* Reticulate body (800-1000 nm)
– Replication and growth
what is the most common std in Canada and US? how does it affect each sex respectively?
Chlamydia trachomatis
Males: urethritis
Females: cervicitis
what happens if chlamydia trachomatis goes untreated?
Untreated male: prostatitis,epididymitis
Untreated female: PID, tubal infertility,
ectopic pregnancy, chronic pelvic pain
species has been divided into 2 biovars:
trachoma and LGV (lymphogranuloma venereum)
Other infections caused by C. trachomatis:
a chronic ocular infection; leading cause of blindness in the middle-East, North Africa,
and S.E. Asia.
-Inclusion conjunctivitis and less frequently pneumonia in the newborn as a result of perinatal transmission
Lymphogranuloma venereum: STD from some
serotypes of C. trachomatis; endemic in tropical
and subtropical countries
Other Chlamydiae
CHLAMYDIA PNEUMONIAE
* Respiratory tract infections, mild pneumonia
* Usually sub-clinical infections
* CHLAMYDIA PSITTACI
* Bird pathogen
* Can transmit to humans
* Pneumonia or endocarditis
what is a mycoplasma? where is it usually found
Smallest free-living bacterium (100-300 nm)
-Saprophytes, part of normal flora of oropharynx and
genital tract of humans and animals
PRIMARY cause of atypical pneumonia
* More common in younger individuals (15-35 years)
* RARELY complications lead to meningoencephalitis,
myocarditis
* Diagnosis is usually clinical, no lab confirmation
* Treatment: erythromycin or tetracycline
MYCOPLASMA PNEUMONIAE (causes, who it effects, complication, diagnois, treatment)
GENITAL MYCOPLASMA (MYCOPLASMA HOMINIS,
UREAPLASMA UREALYTICUM)
- Part of normal genital flora
- Rate of colonization increases with number of sexual
partners - May cause urethritis, epididymitis, pelvic inflammatory
disease and postpartum fever - ?? Infertility and premature birth ??
level of depths of infections
Superficial
Cutaneous
Subcutaneous
Systemic
Aspergillus flavus
spores of this mold are everywhere
- some develop type 1 hypersensitivity reaction (IgE-mediated)
- persons with lung cavitations from TB or malignancies can get aspergillus fungal ball
(aspergilloma) in cavity
- immunocompromised persons can develop invasive pneumonias and disseminated diseases
- A. flavus and other fungi produce toxins called mycotoxins
- A. flavus produces aflatoxin
o Contamination of peanuts, grains and rice
