Obligate Intracellular Pathogen Rickettsia Chlamydia

Family Rickettsiaceae: Genera Zoonotic infection Human microbial pathogens ~61% zoonotic Rickettsia are arthropod-borne infections Spotted Fever Group Rickettsia rickettsii – Rocky Mountain spotted fever; rodent, tick Typhus Group Rickettsia typhi – Endemic typhus; rodent, flea Rickettsia prowazekii – Epidemic typhus; mammal, louse

Rickettsia: Gram Stain and Culture Gram (-) small, pleomorphic coccobacilli Gram stain poorly, observed by Giemsa stain of infected cell Grow in phagocytic, nonphagocytic cells Lab culture in embryonated eggs or cell tissue culture (similar for virus) Cultivation costly and hazardous; aerosol transmission occurs easily

Chlamydia, Rickettsia, Virus

Rickettsia: Lab ID Giemsa, or Immunofluorescence assay (IFA) - direct detection MO in tissue Weil-Felix reaction – Nonspecific test Rickettsial antibody agglutinate Proteus vulgaris Presumptive evidence of typhus group infection Not very sensitive or specific, many false positives Agglutination or Complement Fixation (CF) assay - use specific Rickettsial antigen, test for infection and antibody

Rickettsia: Virulence Factors Induced phagocytosis, intracelluular growth – protected from host immune clearance Replicates in endothelial cells – cell damage, vasculitis Recruitment of actin - intracellular spread

Rickettsia: Infection and Disease Disease worldwide, USA Arthropod reservoir/vector (tick, mite, louse, flea) Diseases characterized by fever, headache, myalgias, usually rash

R. rickettsii: Rocky Mountain Spotted Fever (RMSF) USA ~500-1000 cases/year Ticks must remain attach for hours Incubation 7 days - headache, chills, fever, aching, nausea Followed by maculopapular rash on extremities (including palms and soles), spread chest, abdomen If untreated Petechial rash, hemorrhages skin and mucous membranes Vascular damage, MO invades blood vessels Death up to 20%, due to kidney or heart failure

Rocky Mountain Spotted Fever

Rickettsia: Typhus Group Incubation 5-18 days Symptoms - severe headache, chills, fever, maculopapular rash (subcutaneous hemorrhaging as MOs invade blood vessel) Rash begins on upper trunk; spread to whole body except face, palms of hands, soles of feet Lasts ~2 weeks Patient may have prolonged convalescence

R. typhi : Endemic Typhus Fever Disease worldwide in warm, humid areas (Gulf states, So Cal.; S. America, Africa, Asia, Australia, Europe) Murine typhus - rat primary reservoir, transmitted to human by rat flea Disease occurs sporadically Clinically same, but less severe than epidemic typhus Restricted to chest, abdomen; generally uncomplicated, lasts <3 weeks Low fatality

R. prowazekii : Epidemic Typhus Fever Disease C & S Americas, Africa; less common USA Human, squirrel primary reservoir Transmitted by louse; bites, defecates in wound At risk - people living in crowded, unsanitary conditions; often war, famine, natural disaster Complications - myocarditis, CNS dysfunction Mortality high untreated cases, up to 20% Brill-Zinsser disease - individual may harbor MO, latent infection with occasional relapses

Rickettsia: Treatment and Prevention RMSF Doxycycline drug of choice Avoid ticks, wear protective clothing, use insect repellents, insecticides In infested areas, check and remove ticks immediately Typhus Fever Doxycycline effective Improve personal hygiene and living conditions, reduce lice by insecticides, control rodent population Inactivated vaccine for epidemic typhus

Family Chlamydiaceae: Genera Chlamydia trachomatis – STD, eye infection Chlamydophila pneumoniae – pneumonia Chlamydophilia psittaci – pneunomia (psittacosis); birds, humans Obligate intracellular parasite Cell wall similar G(-) bacilli, lack peptidoglycan Energy parasites, use ATP of host cell Giemsa stain - Chlamydia inclusions in tissue

Chlamydia: Life Cycle – Elementary Body (EB) Circular, infectious form; 300-400 nm Metabolically inactive Resistant to harsh environments 0 hour - EB binds to host cell, induced phagocytosis Outer membrane of EB prevents lysosome fusion, survives in phagosome 8 hours - EB reorganizes into Reticulate Body (RB)

Chlamydia: Life Cycle – Reticulate Body (RB) Noninfectious form, larger, less dense, 800-1000 nm Metabolically active 8-30 hours Synthesize new materials Multiply by binary division Form inclusion body Reorganize, condense into EB 35-40 hours - cell lyses, releases EB, begins cycle again

Chlamydia: Lab ID Stain tissue Cell culture DNA amplification test Giemsa stain Direct fluorescent antibody (DFA) ELISA Less sensitive Cell culture More sensitive method Grow MO in tissue culture, stain infected cells DNA amplification test Recently developed Specific, sensitive Now routine test of choice

Chlamydia: Virulence Factors Intracellular replication – protected from host immune defense Prevent fusion of phagolysome – evades phagocytic killing Repeated infections by C. trachoma result in cell pathology Serotypes A-K and L1, L2, L3 - serotype identifies strain’s clinical manifestation

Chlamydia trachomatis: Trachoma “rough” “trachoma” granulations on conjunctiva Serotypes A-C Single, greatest cause blindness developing countries Infections mainly children (reservoir), infected first three months life Transmission eye-to-eye, direct contact (droplet, hand, clothing, fly) Chronic infection, reinfection common Conjunctival scarring, corneal vascularization Scars contract, upper lid turn in so eyelashes cause corneal abrasions Leads to secondary bacterial infections, blindness

C. trachomatis: Lymphogranuloma Venereum Serotypes L1, L2, L3 Venereal disease, occurs developing, tropical areas Primary stage - painless lesion (vesicle or an ulcer) occurs site of entry in few days, heals with no scarring; but widespread dissemination Secondary stage - occurs 2-6 weeks later, symptoms of regional suppurative lymphadenopathy (buboes), may drain for long time, accompanied by fever and chills. Arthritis, conjunctival, CNS symptoms Tertiary stage - urethrogenital perineal syndrome; structural changes, such as non-destructive elephantiasis of the genitals, rectal stenosis

C. trachomatis: STD Urogenital tract infection - serotypes D-K Major cause of nongonococcal urethritis; frequently found concomitantly with N. gonorrhoeae In males - urethritis, dysuria, sometimes progresses to epididymitis In females - mucopurulent cervical inflammation, can progress to salpingitis and PID USA - #1 STD

C. trachomatis: Inclusion Conjunctivitis Newborns and adults Genital tract infection source of eye infection (serotypes D-K) Benign, self-limited conjunctivitis, heals with no scarring Newborns infected during birth process: 1-2 weeks, mucopurulent discharge Lasts 2 weeks, subsides Some develop afebrile, chronic pneumonia In adults – causes an acute follicular conjunctivitis with little discharge

Chlamydia: Treatment and Prevention Genital tract infection and conjunctivitis: Adult - azithromycin or doxycycline, prompt treatment of patients and partners Newborn – erythromycin Public Health education Trachoma: Need prompt treatment, prevent reinfection Systemic tetracycline, erythromycin; long term therapy necessary Improve living, sanitary conditions Difficult to prevent endemic disease in developing countries due to lack of resources, medical care

Chlamydophilia pneumoniae: RT Infection Human pathogen; common infection, especially 6-25 yr. old Most infections asymptomatic or mildly symptomatic Sore throat, hoarseness, flulike symptoms May cause sinusitis, pharyngitis, bronchitis, pneumonia Accounts for ~10% hospitalized pneumonia

Chlamydophila psittaci: Psittacosis “parrot” “parrot fever” Naturally infects avian species Mild to severe respiratory infections Human infection by contact infected bird Infection - subclinical to fatal pneumonia Commonly causes atypical pneumonia with fever, chills, dry cough, headache, sore throat, nausea, and vomiting

Case Study 9 - Chlamydia A 22-year-old man came to the emergency department with a history of urethral pain and purulent discharge that developed after he had sexual contact with a prostitute. Gram stain of the discharge revealed abundant gram-negative diplococci resembling Neisseria gonorrhoeae. The patient was treated with penicillin and sent home. Two days later, the patient returned to the emergency room with a complaint of persistent, watery urethral discharge. Abundant white blood cells but no organisms were observed in Gram stain of the discharge. Culture of the discharge was negative for N. gonorrhoeae but positive for C. trachomatis.

Case Study 9 - Questions 1. Why is penicillin ineffective against Chlamydia? What antibiotic can be used to treat this patient? 2. Describe the growth cycle of Chlamydia. What structural features make the EBs and RBs well suited for their environment? 3. Describe the differences among the three species in the family Chlamydiaceae that cause human disease.

Class Assignment Textbook Reading Chapter 40 Zoonotic and Rickettsial Disease The Rickettsiaceae Omit: Remaining last two Sections of reading Omit: Key Terms, Learning Assessment Questions Chapter 24 Chlamydia, Mycoplasma, and Ureaplasma Chlamydia Key Terms Learning Assessment Questions

Final Exam Tue., March 20, 2012 8:30 – 10:30 am Mycobacterium thru Ureaplasma Lecture, Reading, Key Terms, Learning Assessment Questions Case Study 7, 8, 9, 10 (Mycobacterium, Clostridium, Chlamydia, Legionella) Exam Format: Multiple Choice Terms True/False Statements Short Essay Review, Review, Review! Repetition is the key to retention