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ZaidKhalid MBBS220 Rickettsiae, Orienta, Coxiaella, Bartonella and Ehrlichia Rickettsiae General Characteristics 1. Small gram negative coccobacilli 2. Best stained by Giemsa, particularly in infected cells 3. Cell wall contains lipopolysaccharide a. At least 2 large proteins in the outer membrane b. Peptidoglycan 4. Can only be grown in living host cells a. Embryonated egg b. Cell cultures Epidemiology and Pathogenesis 1. It has animal reservoir a. Insect vectors i. Prominent component of their life cycles 2. It infects vascular endothelium a. After a bite from anthropod vector 3. Vasculitis, primary pathologic lesion a. Multiplication of rickettsiae at the endothelium 4. Focal areas of endothelial proliferation and perivascular infiltration a. Leads to thrombosis b. Leakage of RBC into the surrounding tissues c. Which account for i. Rash ii. Petechial lesion 5. Vascular lesions occur throughout the body a. Causing systemic manifestation of the disease 6. Infection characterised by a. Fever b. Headache with widespread focal lesions c. Rash is the most prominent 5. Outside host cell, rickettsiae a. Ceases metabolic activity b. Leaks in i. Proteins ii. Nucleic acid iii. Essential small molecules c. Thus making it i. Rapid loss of infectivity ii. Cause penetration of a new host cell requires energy 6. Rickettsiae needs to borrow some host cell essential molecules for a. Adequate growth b. Making it fragile in the environment Lab Diagnosis 1. Culturing of rickettsiae is a. Dangerous b. Difficult 2. Only be done in Reference Lab 3. Serological tests are the primary means of diagnosis 4. It includes a. Weil-Felix test i. Serum of pts infected by typhus agglutinate with certain Proteus sp. ii. This test is lacked of 1. Sensitivity 2. Specificity b. Indirect fluorescent antibody (IFA) c. Immunoperoxidase test Treatment DOC – early treatment 1. Tetracycline 2. Chloramphenicol Antibiotics don’t kill the bacteria, only supress its growth Recovery depends solely on pts immune response ZaidKhalid MBBS220 Coxiella Coxiella burnetti General Characteristics 1. Small intracellular bacteria a. Stained poorly by Gram stain b. Best with Giemsa stain 2. Replicates in phagolysosome of infected cells 3. Able to undergo antigenic variation a. Expression of cell wall lipopolysaccharide antigen 4. Have affinity to reticuloendothelial system 5. Resistant to drying a. Able to produce infection thru respiratory route Virulence Factor 1. Categorised in two phases a. Phase I antigen (infectious form) i. Blocks antibody reaction with surface proteins b. Phase II antigen i. Exposing the surface proteins to antibodies ii. Producing a less infectious form 2. Antibody reaction is useful in the determination of a. Acute infection b. Chronic infection 3. Acute disease a. Characterised by antibodies to the exposed phase II antigen 4. Chronic disease a. High antibody titers against Phase I and Phase II antigens are detected in patients Clinical Disease 1. Q fever a. Zoonosis b. Infecting human thru inhalation rather than anthropod bite c. Asymptomatic in humans d. Develops acutely or as a chronic infection 2. Acute disease a. Begins 9-20 days after inhalation b. With abrupt onset of i. Fever ii. Chills iii. Headache c. No rash d. Development of i. Hepatomegaly ii. Abnormal liver function e. Complications like (rare) i. Myocarditis ii. Pericarditis iii. Encephalitis 3. Chronic disease a. Culture-negative endocarditis Diagnosis 1. High rising titer of antibody of Q fever antigen is detected by a. Complication Fixation Test (CFT) b. Indirect Florescent Antibody test (IFA) Treatment 1. DOC of acute infection a. Tetracycline 2. DOC of chronic infection a. Rifampicin b. Plus i. Doxycycline ii. Or Bactrim ZaidKhalid MBBS220 Orienta Orienta tsutsugamushi General Characteristics 1. Formerly known as Rickettsia tsutsugamushi 2. Reservoir is from mite a. Transmitted transovarian means Clinical Disease Scrub typhus 1. Transmitted thru mites a. Chiggers b. Red mites 2. Mite larvae (chiggers) deposit the organism as they feed 3. After 10-12 days of incubation, pts will develop a. Severe headache b. Fever and myalgia 3. Bartonella General Characteristics 1. 2. Treatment c. Macular to popular rash 4. Typical initial lesion a. Necrotic eschar at the site of bite on extremities b. Develops 50-80% of cases 5. May develop generalised a. Lymphadenopathy b. Hepatosplenomegaly The only rickettsiaceae can be cultured on artificial media Media is a. Freshly prepared brain-heart infusion b. Agar with 5% or 10% of i. Rabbit ii. Or horse blood c. Should be incubated in humid atmosphere for up to 3-4weeks Types a. Bartonella quintana i. Causative agent of trench fever ii. Worldwide distribution iii. Named from prominence appearance in the trenches of World War I iv. Reservoir in human v. Vector is the body louse b. Bartonella henselae i. Causative agent of cat scratch disease Clinical Disease Cat scratch disease 1. 2. Lymphocutaneous disease Pts has history of a. Cat scratch b. Cat exposure 3. 5-120 days of incubation a. Nodular/indurated swelling appears at the scratch area b. May discharge few pus Local draining lymph nodes a. Enlarge b. Become tender c. Suppurating and discharging 5. Disease is self-limiting a. May last for 3weeks or more 4. DOC 1. Tetracycline 2. Or chloramphenicol Treatment DOC 1. Oral tetracycline 2. Oral erythromycin These antibiotics may shorten the course of illness ZaidKhalid MBBS220 Ehrlichia General Characteristics 1. Taxonomically grouped with Rickettsiae 2. It is a. Obligatory intracellular organism b. Parasitises the granulocytes c. Gram negative coccus d. Multiplies in intracytoplasmic vacuoles of the infected cells 3. Has tick vectors 4. Tropism for either (polymorph) a. Monocytes Clinical Disease Ehrlichiosis 1. Characterised (manifestation of infectious mononucleosis) by a. Fever b. Lymphadenopathy c. Atypical lymphocytosis 2. Consistent symptoms a. Fever b. Headache c. Malaise d. Myalgia e. Arthralgia f. Nausea 3. 30% of cases a. Patchy erythema b. Maculopapular rash c. Petechiae 4. 90% have history of tick bites 5. Within 48-72 hours, may present with a. Lymphopenia b. Leucopenia c. Thrombocytopenia b. Granulocytes 5. Further divided into a. Ehrlichia chaffeensis i. Causing human monocytotrophic ehrlichiosis ii. Primarily found in the South-Eastern USA b. Ehrlichia sennetsu i. Similar disease ii. Found in 1. Western Japan 2. Malaysia Diagnosis 1. Diagnosis is confirmed by a. Observing typical morulae in WBC b. Indirect florescent antibody test 2. Culture requires variety of tissue culture lines 3. Reference Lab can perform a. PCR b. Culture Treatment DOC 1. Tetracycline in the form of doxycycline 2. Rifampicin is alternative drug