Intracellular bacteria - Chlamydia; Rickettsia & Orientia; Ehrlichia, Anaplasma & Neorickettsia; Coxiella burnetti Flashcards
Features & examples of Chlamydia
- Little peptidoglycan
- infectious form = elementary body
- EB enters host cell & reproduces in a membrane bound vesicle = reticulate body (replicative form)
- new EBs produced & release from infected cell
- Chlamydia trachomatis
- Chalmydophilia psittaci
- Chlamydophilia pneumoniae
Features of Chlamydia trachomatis
- acquired primarily from human sources
- many strains, distinguished by different surface antigens
1. Oculogenital biovar = A-K
2. Lymphogranuloma venereum (LGV) biovar = L1-L3
Transmission of serovars A, B, Ba, C (C. trachomatis)
- Fingers
- Flies
- Fomites
Clinical presentations of serovars A, B, Ba, C (C. trachomatis)
Trachoma (eye inf common in LDCs)
- repeated infections occur, protective immunity doesn’t develop
1. Pannus formation (cornea becomes clouded)
2. Chronic inflamm & scarring of eyelids & cornea
3. Eventual blindness
Diagnosis of serovars A, B, Ba, C (C. trachomatis)
Serology
- Complement fixation test (genus specific)
- Micro-immunofluorescence species & serovar specific
- generally only useful for more invasive forms of infections
Treatment & prevention of serovars A, B, Ba, C (C. trachomatis)
- Antibiotics
- Education in better hygiene
Transmission of serovars L1, L2, L3 (C. trachomatis)
Sexually transmitted disease
Clinical presentations of serovars L1, L2, L3 (C. trachomatis)
Lymphogranulomavenereum (LGV)
- commonly in tropics/subtropics
1. Primary lesion: small papule/vesicle on genitalia
2. Infection spreads to regional lymph nodes which enlarge, suppurate & discharge through sinuses - M: inguinal glands affected, F & homosexual M: perirectal glands suppurate - proctitis & bloody anal discharge
3. Chronic inflammation - lymphatic blockate - rectal stricture, elephantiasis of genitals
Diagnosis, treatment & prevention of serovars L1, L2, L3 (C. trachomatis)
- Serology - complement fixation test, MIF
- Antibiotics
- Contact tracing, screening of high risk groups, use of condoms, education
Transmission of serovars D-K (C. trachomatis)
- Sexually transmitted disease
- Autoinfection (fingers)
- Vertical
Clinical presentations of serovars D-K (C. trachomatis) (3)
- Males: non/post-gonococcal urethritis - asymptomatic carriage is common, inf may spread to epididymis, prostate, proctitis in homosexuals
- Females: mucopurulent cervicitis, urethritis, ascending infection causing acute salpingitis/acute PID, spread into peritoneal cavity causing peri-appendicitis/peri-hepatitis (Fitz- Hugh- Curtis syndrome), vaginal discharge, proctitis
- Adult inclusion conjunctivitis (due to autoinfection).paratrachoma, ophthalmia neonatorum (due to endocervical inf in mother)
Diagnosis of serovars D-K (C. trachomatis)
- Molecular (PCR)
- Antigen detection (IF/ELISA)
- Serology
Treatment & prevention of serovars D-K (C. trachomatis)
- Antibiotics, contact tracing, screening of high risk groups, use of condoms, education
- Erythromycin as systemic treatment in ophthalmia neonatorum (prevent development of pneumonitis, recurrent conjunctivitis)
Transmission of Chlamydophilia psittaci
Zoonosis, from birds
Clinical presentations of Chlamydophilia psittaci
Psittacosis, Ornithosis
- flu-like initial illness leading to pneumonia
- dissemination - infection of brain, meninges, heart, joints etc
- rare cause of bacterial endocarditis
Diagnosis & treatment/prevention of Chlamydophilia psittaci
- Serology
- Quarantine & treatment of infected birds
Clinical presentations of Chlamydophilia pneumoniae
- from human sources
- Mild pneumonia in young adults
- both upp & lower resp tract symptoms
- reinfection/chronic infection in older patients, roles in asthma, COPD, bronchitis etc - May contribute to atherosclerosis & CHD
- diagnosis: serology
Features of rickettsia & orientia
- Small gram neg bacilli
- Obligate intracellular pathogens
- Reproduce in endothelial cells lining blood vessels
Transmission of rickettsia & orientia
Zoonosis, by arthropod vectors
- Typhus Group - louse or flea
- Spotted Fever Group - mostly by ticks (R. akari by mouse mite, R. felis by cat flea)
- Scrub Typhus Group - chiggers (parasitic larval stage of mite)
Clinical presentations of rickettsia & orientia (3)
Triad of fever + rash + tick bite
- PUO with headache & muscle pain
- Skin Rash (macular/papular/petechial/vesicular in rickettsial pox), if severe - damage of blood vessels - hypotension & hypoperfusion of organs - multiple organ failure - SIRS, death
- Bite mark, eschar (ulcer w dark/black crust, in spotted fever/scrub typhus)
Classification of rickettsia & orientia
Typhus Group
- Epidemic typhus: R. prowazekii - spread person to person by body louse, infection kills louse vector, inf may reactivate after many years: Brill-Zinsser Disease
- Murine typhus: R. typhi (assoc w rats, fleas are the vector)
Spotted Fever Group
- R. rickettsi (rocky mountain, spotted fever, ecchymotic rash)
- R. conorii (boutonneuse fever)
- R. africae (African tick bite fever)
- R. akari (rickettsial pox)
- R. felis (flea-borne SF)
Scrub Typhus Group
- Orientia tsutsugamushi
Diagnosis of rickettsia & orientia
Serology - no longer use Weil-Felix test due to low sensitivity & specificity
Treatment of rickettsia & orientia
Doxycycline
- antibiotic resistant O. tsutsugamushi detected in N Thailand
Prevention of rickettsia & orientia (2)
- Delouse at risk populations
2. Physician awareness & stringent rodent control measures
Features of ehrlichia, anaplasma & neorickettsia
- Obligate intracellular pathogens of WBCs - replicate in leukocytes
Features of E. chaffeensis, A. phagocytophilum, E. ewingii
- E. chaffeensis infects human monocytes/macrophages
- A. phagocytophilum & E. ewingii infect granulocytes
- transmitted via tick bite, animal reservoirs
- fever, sometimes rash & severe multi-system disease, may develop secondary opportunistic infections
Features of Neorickettsia sennetsu
- infections found in Japan & Malaysia, infects human macrophages
- transmitted via eating raw fish containing infected trematodes (flukes)
- glandular fever like illness (infectious mononucleosis) with chills, fever & enlarged cervical lymph nodes
- rash is rare, usually a mild infection
Diagnosis of ehrlichia, anaplasma & neorickettsia
- Serology
2. Morula seen in cytoplasm of leukocytes - intracellular inclusion w replicating bacteria
Treatment of ehrlichia, anaplasma & neorickettsia
Doxycycline
Features of Coxiella burnetti
- Obligate intracellular pathogen
- Replicates in acidified vesicle (phagolysosome) within macrophages
- Spore-forming (resistant spore-like structures), survive drying & other environmental stresses
Transmission of Coxiella burnetti
- naturally infects many animal species - sheep, cattle, goats, shed in large numbers in urine, faeces, milk, birth products
Zoonosis (airborne or drinking infected milk)
Clinical presentations of Coxiella burnetti (2)
- Acute Q fever
- many infected asymptomatically/minor symptoms, some with pneumonia, hepatitis, PUO - Chronic Q fever
- endocarditis (“culture negative endocarditis” as organism does not grow in conventional blood culture systems), rarely cholecystitis
Diagnosis of Coxiella burnetti
Serology, PCR, culture
Treatment of Coxiella burnetti (2)
- Acute infection: Doxycycline + Rifampicin
2. Endocarditis: difficult, combinations of drugs for long periods or valve replacement
