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Brucella and mycoplasma
 

Brucella and mycoplasma

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    Brucella and mycoplasma Brucella and mycoplasma Presentation Transcript

    • BrucellaBrucellosis Dr Kamran AfzalAsst Prof Microbiology
    • Background Brucella melitensis discovered by Bruce in 1887 Members of this genus are pathogenic to animals from which they are transmitted to man causing „brucellosis‟ (Undulant or Malta fever)
    • The genus includes Br. melitensis, causing infection in goats and sheep Br. abortus, causing abortion of cattle Br. suis, causing infection in pigs Br. ovis, causing infection in birds Br. canis, causing infection in dogsPathogenic types in humans: Br. melitensis, abortus, canis and suis Zoonotic disease
    • Epidemiology
    • Morphology Gram negative short cocco-bacilli, non- motile, non- sporing and non capsulated Aerobes, require enriched media for growth 10-20% CO2 is required for primary growth of Br. abortus but not for the others Br. abortus and Br. suis produce H2SAntigenic structure: Two Lp antigens, A and M are present in different proportions in the four species They can be differentiated by specific monoclonal antibodies
    • Who is at Risk? Occupational Disease  Cattle ranchers/ dairy farmers  Veterinarians  Abattoir workers  Meat inspectors  Lab workers Hunters Travelers Consumers of unpasteurized dairy products
    • TransmissionThree methods of transmission: Ingestion – unpasteurized milk or dairy products Ingestion is most common method of transmission Inhalation – breathing in the aerosolized organism Lab workers are at high risk
    •  Inoculation/Wound contamination – high risk occupations include hunters, slaughterhouse workers, meat packing plant workers and veterinarians
    • Transmission
    • Pathogenesis Incubation period 1-6weeks Can multiply and survive within the neutrophils and macrophages Reticuloendothelial system  Liver spleen and bone marrow (Septicemia)
    •  Cell mediated response of the host results in granuloma and abscess formation in the bone or any organ
    • Brucellosis: Undulant fever An acute bacteraemic phase A chronic stage that may extend over many years and may involve many tissues Intermittent fever, bouts of fever for 3-4 weeks, alternating with afebrile period of a similar duration A prolonged course accompanied with weakness, malaise, profuse sweating, headache, joint and muscle pain Enlarged lymph nodes, liver, and spleen It may be complicated by osteomyelitis
    • Lab Diagnosis Specimens  Blood, pleural/peritoneal fluids, CSF, Bone marrow (92% sensitive), biopsy: liver, spleen and lymph node
    • Lab DiagnosisI-Blood Culture: Isolation of the organism from the blood by repeated blood cultures incubated in 10-20% CO2 for 4-6 weeks Subcultures are done on serum dextrose agar (SDA), chocolate agar, Thayer-Martin medium Isolated organisms are serologically identified by specific antisera
    • II-Serologic diagnosis: Detection of antibodies A tube agglutination test is done using dilutions of the serum A titer of at least 1/60 in convalescent serum is diagnosticCoomb’s antiglobulin method : to detect the non-agglutinating IgA antibodies that appear during the subacute stage of infection, and tend to persist for years They are called blocking or incomplete antibodiesDetection of IgG and IgM by ELISA
    • III-Direct detection in clinical material by PCRIV- Brucellin test: It is similar to tuberculin test and is based ondelayed type hypersensitivity, it is unreliable and is rarely used
    • Treatment Prolonged treatment  Chronicity of the disease  Intracellular survival of the organism 6 weeks course of a combination of antibiotics Doxycycline and rifampin or doxycyclin and streptomycin or rifampin and trimethoprim-sulfamethoxazol are used
    • Prevention/Infection control Pasteurizing milk and dairy products Eradicating infection from herds and flocks Live attenuated vaccine is used for cattle No vaccine is available for humans Observing safety precautions for occupational exposures including  rubber boots  wearing impermeable clothing  gloves and face masks  practicing good personal hygiene
    • Biological warfare In 1954, B. suis became the first agent weaponized by the US Brucella species survive well in aerosols and resist drying Brucella and all other remaining biological weapons in the U.S. arsenal were destroyed in 1971–72 when the U.S. offensive biological weapons (BW) program was discontinued The United States BW program focused on three agents of the Brucella group:  Porcine Brucellosis (Agent US)  Bovine Brucellosis (Agent AB)  Caprine Brucellosis (Agent AM)
    • MycoplasmaMycoplasmosisAtypical pneumonia
    • Mycoplasmas Smallest free-living capable of autonomous growth Key genera: Mycoplasma, Spiroplasma Lack cell walls  Key components of peptidoglycan are missing  Muramic acid and diaminopimelic acid Mycoplasma cells are pleomorphic  Cells may be cocci or filaments of various lengths
    • Taxonomy
    • Differentiation of species M. pneumoniae - glucose M. hominis - arginine U. urealyticum - urea M. genitalium - difficult to culture
    • Diseases O rg a n is m D is e a s eM . p n e u m o n ia e U p p e r re s p ira to ry tra c t d is e a s e , tra c h e o b ro n c h itis , a ty p ic a l p n e u m o n ia , (c h ro n ic a s th m a ? ? )M . h o m in is P y le o n e p h ritis , p e lv ic in fla m m a to ry d is e a s e , p o s tp a rtu m fe v e rM . g e n ita liu m N o n g o n o c o c c a l u re th ritisU . u re a ly tic u m N o n g o n o c o c c a l u re th ritis , (p n e u m o n ia a n d c h ro n ic lu n g d is e a s e in p re m a tu re in fa n ts ? ? )
    • Morphology Smallest free-living bacteria (0.2 - 0.8 µm) Small genome size Strict aerobe Lack a cell wall Grow slowly by binary fission “Fried egg” colonies
    • “Fried Egg” Colonies of Mycoplasma M. pneumoniae colonies have a granular appearance
    • Can be part of normal flora They reside extracellularly in the respiratory and urogenital tracts and rarely penetrate the sub-mucosa, except in the case of immunosuppression or instrumentation, when they may invade the bloodstream and disseminate to numerous organs and tissues
    • Mycoplasma are cell wall deficient  Cross-section of Mycoplasma bacteria
    • Pathogenesis Adherence  P1 pili  Movement of cilia ceases  Clearance mechanism stops Toxic metabolic products  Peroxide and superoxide Immuno-pathogenesis  Activate macrophages  Stimulate cytokine production
    • Clinical manifestations Tracheo-bronchitis  70-80% of infections Pneumonia  Approximately 10% of all atypical pneumonias  “Primary atypical pneumonia”  Mild disease but long duration
    •  Incubation 2-3 weeks  Radiological signs Persistent non-productive cough precede symptoms  Slow resolution  Rarely fatal
    • Laboratory Diagnosis Microscopy  Difficult to stain Immunochromatography (ICT) Immunofluorescence (IF) Culture (definitive diagnosis)  Sputum (usually scant) or throat washings  May take 2-3 weeks Molecular diagnosis  PCR-based tests, rapid, sensitive and specific
    •  Serology  Cold agglutinins (40C)  ELISA  1/3 - 2/3 of patients  Complement fixation  Appear earlier  May take 4-6 weeks  Non-specific  Fourfold rise in titer  Presumptive diagnosis
    • Culturing Mycoplasma Mycoplasma can be cultured on liquid or solid media  Broth enriched with 20% horse or human serum Grows optimally at 35 - 370 C up to 3 weeks The colonies appear as fried egg
    • Treatment and Prevention Treatment  Tetracycline or erythromycin  Newer fluoroquinolones  They are relatively resistant to pencillins and cephalosporins Prevention  Avoid close contact  No vaccine