Neisseria, Chlamydia and Treponema Flashcards
Neisseria
- gram-negative
- diplococci
- oxidase-positive
- culture on selective Thayer Martin plates – chocolate agar (heated blood = brown)
- can get false negatives in gram stain
N. gonorrhoeae (gonococcus)
- found only in humans
- gonorrhea
- second most common venereal disease
Other clinical features of N. gonorrhoeae
- cervicitis= relatively asymptomatic
- pharyngitis= often asymptomatic
- pelvic inflammatory disease PID= can be extremely severe, abdominal pain and fever, chronic pelvic pain
Dissemination - gonococci
- gonococcal arthritis (septic)
- ophthalmia (highly contagious)
Therapy N. gonorrhoeae
- B-lactamase-resistant cephalosporin *ceftriaxone
- resistant strains are common *produce b lactamases destroy penicillin
Prevention N. gonorrhoeae
- no vaccine
- safe sex
- adequate contact and treatment of sex partners
Pathogenesis N. gonorrhoeae
-adhesion to genital epithelium
– outer membrane proteins (OMP) – pili
-tissue injury
– cell-wall lipopolysaccharide (LOS) – peptidoglycan
-antigenicity highly variable among strains - antibodies not protective
N. meningitis
- Gram negative diplococci within polymorphonuclear cells -meningococcal antigens -Thayer Martin agar -responds well to antibiotic therapy
Chlamydia trachomatis
-Small, gram-negative rods with no peptidoglycan layer in the cell wall
-Infects nonciliated columnar, cuboidal, and transitional epithelial cells
-Strict human intracellular parasite
-can infect newborns
-Two biovars associated with human disease
• Trachoma
• LGV
C. trachomatis diseases *Chlamydia
-is a common STD caused by C. trachomatis
• most infected people are asymptomatic and lack abnormal physical examination findings
C. trachomatis diseases *Lymphogranuloma venereum (LGV)
-caused by different serovars of the same bacterium, occurs commonly in the developing world,
• has more recently emerged as a cause of outbreaks of proctitis among men who have sex with men (MSM) worldwide
Virulence Chlamydia
- Lipopolysaccharide antigen shared by Chlamydia and Chlamydophila species
- Major outer membrane proteins are species-specific
- Prevents fusion of phagosome with cellular lysosomes
- Pathologic effects of trachoma caused by repeated infections
Epidemiology Chlamydia
- Most common sexually transmitted bacteria in United States
- Ocular trachoma primarily in North and sub-Sahara Africa, the Middle East, South Asia, South America
- LGV highly prevalent in Africa, Asia, and South America
C. trachomatis growth cycle EB and RB
- elementary bodies (EB) - infectious
* reticulate bodies (RB) - noninfectious
Diagnosis Chlamydia
- Culture is highly specific but is relatively insensitive
- Antigen tests (DFA, ELISA) are relatively insensitive
- DNA amplification tests are the most sensitive and specific tests currently available
Treatment Chlamydia
• LGV - doxycycline or erythromycin • Ocular or genital infections - with azithromycin or doxycycline • Newborn conjunctivitis or pneumonia - erythromycin
Treatment CDC
- A single dose of azithromycin or a week of doxycycline (twice daily)
- Same treatment for HIV-positive persons
- Persons should abstain from sexual intercourse for 7 days after single-dose antibiotics or until completion of a 7-day course of antibiotics, to prevent spreading the infection to partners
- All sex partners should be evaluated, tested, and treated.
Risk of reinfection chlamydia
-Women and men with chlamydia should be retested about three months after treatment of an initial infection, regardless of whether they believe that their sex partners were treated.
Chlamydophila pneumoniae
- Human pathogen
- Sinusitis, pharyngitis, bronchitis, and pneumonia
- Only a single serotype (TWAR)
- Transmitted by respiratory secretions
Chlamydophila pneumoniae Treatment
Treat with macrolides (erythromycin, azithromycin, clarithromycin), doxycycline, or levofloxacin
Psittacosis (parrot fever)
- Natural reservoir is virtually any species of bird
- Also sheep, cows, goats, & humans
- Sinusitis, pharyngitis, bronchitis, and pneumonia
- Transmitted to humans by inhalation of dried excrement, urine, or respiratory secretions from psittacine birds (e.g., parrots, parakeets, macaws, cockatiels)
Parrot fever symptoms
- Can be asymptomatic
- Headache, high fever, chills, malaise, and myalgias
- Pneumonia: nonproductive cough, rales, consolidation
- CNS involvement common, usually a headache, but encephalitis, convulsions, coma, and death may occur in severe, untreated cases
- May have GI symptoms, such as nausea, vomiting, and diarrhea
- Other systemic symptoms include carditis, hepatomegaly, splenomegaly, and follicular keratoconjunctivitis
Parrot fever diagnosis
• Serology:
• 4X increase in titer, shown by the CF testing of paired
acute and convalescent phase sera, is suggestive of C. psittaci infection
• Must confirm the serologic diagnosis with species-specific MIF
• C. psittaci can be isolated in cell culture (e.g., with L cells)
after 5 to 10 days of incubation
Treatment parrot fever
- Treat with doxycycline or macrolides
- Prevented only through the control of infections in domestic and imported pet birds
- treat birds with chlortetracycline-HCL for 45 days
Spirochetes
• Gram-negative • long, thin, helical, motile • axial filaments – locomotion – between peptidoglycan layer/ and outer membrane (run parallel)
Syphilis
• chronic
• slowly progressive
• three stages - primary
- secondary - tertiary
Primary syphilis lesions - chancre
- 10 to 60 days
- area of ulceration and inflammation
- many organisms • highly infectious
Secondary (2-10 weeks later) syphilis
- systemic spread
- flu-like symptoms, then rash
- many organisms • highly infectious
Tertiary (several years later) syphilis
• rare • chronic inflammation - the destruction of any organ/tissue - lesions in bone, skin, other tissues • neurosyphilis, cardiovascular syphilis • few organisms
Microbiological diagnosis Syphilis
• not cultureable
• dark field microscopy
– actively motile organisms
– brightly lit against dark backdrop – light shines at an angle
– reflected from thin organisms
– enters objective
• conventional light microscopy – light shines through
– NOT visualized
• fluorescence microscopy – antibody staining
Secondary and Tertiary Syphilis - serology
screening method
- antibodies to cardiolipin
specific diagnosis
- antibodies to a treponemal antigen
Treatment syphilis
• penicillin is effective
- benzathine penicillin - early syphilis – penicillin G - congenital, late syphilis
- no vaccine
