Microbiology: STDs, TB and atypical pneumonia Flashcards
Treponema pallidum
Syphilis
Gram (-) spirochete
Characteristics:
- obligate parasite (needs human host to live)
Transmission:
1) acquired syphilis: via body fluids during sexual intercourse
- can be oral/anal or vaginal as long at the tissue and mucosa have cuts/breaks in the membranes
- can also be contaminated needles or touching open skin lesions directly
2) congenital syphilis: via maternal infection into the placenta or when the baby is combing out of the womb
Treatment:
- IV/ oral dose of penicillin G*
- doxycycline (when you cant use penicillin G)
Stages of acquired syphilis
1) primary (early localized): 1-3 weeks after exposure
- painless syphilitic chancres infected with spirochetes
- typically heal on their own over time, but can cause lymphadenopathy
2) secondary (disseminated): 6-12 weeks
- caused when spirochetes enter the blood stream
- general lymphadenopathy
- maculopapular rash (non-itchy) that starts centralized and spreads peripherally
- “condylomata lata” pustules (smooth, painless, wart like lesions on most areas of the body)
- papulosquamous lesions (scaly hard pustules throughout the body)
- patchy hair loss over the body
- *can develop into latent syphilis if not treated!
- * most infectious stage
2b) latent stage
- not really a stage since it is secondary that is latent and is recurrent if not treated properly (and sometimes even if)
- can develop into tertiary though
3) tertiary syphilis
- type 4 hypersensitivity reaction to spirochetes in capillaries from T-cells:macrophage interactions
- causes localized and systemic inflammation
- can cause “Gummas” (chronic granulomas)
- can cause aortitis (due to cross reaction to cardiolipids from spirochetes and destroy vaso vasorum (blood supply to the aorta and the hearts own blood supply)
- can cause neruo- syphilis if it gets into the CSF and nests in the posterior column of the spinal cord
Symptoms of neuro-syphilis (“tabes dorsalis”)
- argyle-Robertson pupils*: pupils constrict when looking at close objects (accommodate) but not to light (reactive)
- loss of proprioception and vibration (DCML degeneration)*
- broad ataxia
- general paralysis*
- memory loss/ altered behavior/slurred speech*
- (+) Romberg sign
- stoke/stroke symptoms WITHOUT HTN*
Congenital syphilis symptoms
can be a stillborn baby form this
Symptoms:
- maculopapular rash
- “snuffles” (nose blockage by spirochete infected mucus
- hepatosplenomegaly
- facial abnormalities (saddle nose and rhagedes (linear scars at angles of mouth))
- saber shins (bending of the tibia)
- CN8 demyelination (hearing loss)
Chlamydia trachomatis
Gram (-) bacilli
Characteristics:
- obligate intracellular (cant make own ATP)
- non-motile
- obligate aerobe
- has two life cycle stages
only attacks humans and has 15 serotypes
Serotypes and the infections they cause:
1) (A-C) = chlamydia conjunctivitis (“trachoma”) (adults only)
- untreated leads to keratoconjunctivits and cornea destruction (total blindness)*
- this is super common in Africa*
2) (D-K) = genital chlamydia (classic chlamydia), ectopic pregnancy, neonatal pneumonia, neonatal conjunctivitis
- most common type of STD
- men = urethritis and prostatitis
- women = vulvovaginitis, cervicitis, urethritis, PID
3) (L1/L2/L3) = lymphogranuloma venereum ( small painless ulcers on genitalia and large painful inguinal lymph nodes that looks like buboes when ulcerated)
Treatment:
- azithromycin (1 dose and 1st line)*
- doxycycline (multiple doseage required)
- ceftriaxone (ONLY if co-commitment infection with gonorrhoeae, this often happens)*
What are the 2 life cycle forms of chlamydia?
1) elementary body
- infective form and enters cell to become next stage
2) reticulate body
- replicates inside the cell via binary fission and then reorganizes itself to form multiple elementary bodies
- this cycle just continues*
Gardnerella vaginalis
Bacterial vaginosis
Gram (+/-) Cocobacilli
- usually only infects someone when pH imbalances occur (usually increases in pH or alkaline. Is most common in highly sexually active females, but is NOT STD*
- most common vaginal infection in females of reproductive age*
Characteristics:
- non motile
- non spore forming
- facultative anaerobe
Virulence:
- cytotoxin vaginolysin and enzyme sialidase*: cleaves sialic acid and reduces desquamination of epithelium. allows for adherence to vaginal epithelial cells.
- proteolytic carboxylase enzymes*: cleave vaginal peptides into volatile amines (make the vagina smell fishy)
- biofilm (looks like a gray discharge)
Symptoms:
- only a thin white/gray discharge
- can have vaginal/itching/burning/dysuria and dyspareunia (but this means it is a co-infection with mobiluncus species)
- increase chance to have premature birth or miscarriage if having bacterial vaginosis and spread HIV if the female is infected with HIV*
Diagnosis: needs 3/4 at least from the AMSEL criteria
1) thin white-gray discharge
2) vaginal pH > 4.5
3) positive whiff-amine test (smells like fish after mixed with 10% KOH)
4) clue cells are present (epithelial cell tissue samples having coccobacilli along the edges)
Treatment:
- metronidazole (7 day dose)
Chlamydia pneumoniae
Walking pneumonia
Gram (-) acid fast cocci
more common atypical pneumonia in adults/elderly
Characteristics:
- non-motile
- round shaped
- obligate aerobe
- obligate intracellular pathogens (cant generate own ATP and cant grow without host cell)
- stays hidden in epithelial lung tissue until eventual developing mild pneumonia*
- if left untreated, can increase odds of atherosclerosis*
Symptoms:
- often asymptomatic or common flu-like symptoms (fatigue/sore throat/mild fever/dry cough)
Treatment:
- azithromycin
- Doxycycline
Mycobacterium tuberculosis
TB
Gram (+) acid-fast bacilli
- is one of the most relevant latent infections in the world*
- is only infective when active, not latent. If granulomas are present with latent TB, immunosuppressive drugs can push latent to TB -> active*
- always produces granulomas with caseous necrosis*
Characteristics:
- obligate aerobes
- mycotic acid cell wall (resists standard cleaning mechanisms)
Virulence:
- cord factor*: activates macrophages to form granulomas and inhibts phagolysosome fusion
Stages of TB:
1) primary TB
- there are signs of exposure if tested on but symptoms are mostly asymptomatic (or mild flu-like symptoms) and therefore most people are not diagnosed at this stage
2) secondary TB*
- caseating granulomas are present in both macrophages and hilar lymph nodes.
- these granulomas are called “Ghon complexes” and often calcify (make TB latent)*
- these are seen on xray
- * if the immune system is compromised, these Ghon complexes will erupt, making TB active again, causing cavitation in lung tissues and caseous necrosis.
- also can cause dissemination into bloodstream and leads into miliary TB
- symptoms include: fevers, weight loss, night sweats and hemoptysis)
3) Miliary TB
- TB infection in all other organs in the body (including the brain)
- symptoms depend on location, but most common locations are:
1) kidneys = increased WBC in urine and kidney inflammation symptoms
2) meninges = meningitis
3) lumbar vertebrae = pott disease
4) adrenal glands = Addison’s disease
5) liver = hepatitis
6) cervical lymph nodes = lymphadenopathy of the neck
Treatment: - latent = Isoniazid only (9 months) - active = (RIPE therapy) (time frame varies) Rifampin Isoniazid Ethambutol Pyrazinamide
How do you treat XDR-TB (extremely drug resistant forms)?
Combo therapy of
- Pretomanid
- bedaquiline
- linezolid
What is mycobacterium Avium complex?
A subspecies of mycobacterium that is often seen in AIDS patinets (especially if CD4 levels are <50/mm)
Skips straight to progressive primary TB and miliary TB. (Dosent affect lungs usually)
prophylaxis in AIDS patients that have <50/mm CD4T cells with azithromycin is common because it can kill MAC if initially exposured
Treatment:
- RIPE therapy
Mycoplasma pneumoniae
walking pneumonia
Acid-fast gram (+/-) cocobacilli
- most common atypical pneumonia in young adults/ teenagers*
- most often seen in military camps, collage dorms and school settings*
Characteristics:
- facultative anaerobe
- non motile
- non spore forming
Virulence:
- adhesion protien P1*: unique adhesion molecule that binds to epithelium cells in respiratory epithelium and is very good at resisting mucocillary clearance
Complications:
1) atypical pneumonia: uncommon symptoms
- fatigue
- sore throat
- mild fever
- dry hacking cough
2) encephalitis (only in children
- altered mental status
- stiff neck
- fever
Treatment:
- generally self-limiting
- can use tetracyclines or macrolides if it doesnt cure itself
