Yersinia


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1 : YERSINIA AND PASTEURELLA Eligius Lyamuya, MD, MMed, PhD Department of Microbiology and Immunology, Muhimbili University of Health and Allied Sciences
2 : LEARNING OBJECTIVES Know the general characteristics of Yersinia and Pasteurella Understand the growth characteristics, virulence factors and pathogenesis of infection caused by Y. Pestis, Y enterocolitica, Y. pseudotuberculosis and P. multocida Know the various methods for laboratory diagnosis of infections due to Yersiniae Know the general principles of treatment, prevention and control of plague Know the general principles of treatment, prevention and control of other infections caused by Yersinia spp and Pasteurella spp
3 : YERSINIA Family: Enterobacteriaceae Genus: Yersinia Species of medical importance: Yersinia pestis Yersinia enterocolitica Yersinia pseudotuberculosis
4 : GENERAL CHARACTERISTICS Coccobacillary, ovoid or rod shaped, bipolar staining Gram negative Aerobic or facultatively anaerobic Grow on ordinary media Best growth temp. 25-30?C Oxidase -ve, Catalase +ve, Indole -ve, ONPG +ve, Urease +ve except Y. pestis
5 : Stained preparation showing Yersinia pestis
6 : Yersinia pestis
7 : CULTURAL CHARACTERISTICS Polymorphism in old cultures Capsulated forms in exudates from lesions In broth, stalactites (hanging growth) seen with oil overlay, granular deposits if no oil Colonies on MCA disappear after 2-3 days due to autolysis
8 : Biotypes Biotype Glycerol Nitrite acidification reduction Y. pestis var orientalis - + Y. pestis var antiqua + + Y. pestis var medievalis + -
9 : ANTIGENIC STRUCTURE-1 LPS Capsular (envelope) antigenic complex F1 antigen Heat labile Develops at 37?C Somatic antigenic complex V and W antigens Heat stable Develops at 20?C and 37?C
10 : ANTIGENIC STRUCTURE-2 Other virulence factors:- Low calcium response (lcr) gene Yops (Yersinia outer proteins) Coagulase produced at 28?C Plasminogen activator
11 : PATHOGENESIS Agent for plague Transmission: Wild rodent epizootics ? semidomestic rodents ? domestic rodents ? fleas ? man ? man transmission: fleas, Pulex irritans, airborne (pneumonic) Injection into man by fleas ? regional lymph nodes ? blood stream ? organs (spleen, liver, kidneys, others) Causes infarcts, necrosis and haemorrhage
12 : CLINICAL TYPES Bubonic Septicaemic Pneumonic Others: Plague meningitis Tonsillar or pharyngeal plague Plague carbuncle
13 : LABORATORY DIAGNOSIS Specimens Bubo aspirate Sputum Blood Others depending on clinical presentation Tests Staining (Wayson’s, methylene blue, Gram) Culture Serology
14 : EPIDEMIOLOGY-1 Disease of antiquity First documented epidemic ?1320 BC (Biblical evidence) Major pandemics: Justinian plague: -6th C Black death: -14th C Oriental plague: -Late 19th C
15 : EPIDEMIOLOGY-2 Primarily a disease of rodents and their fleas Case fatality if untreated: 50-75% for bubonic plague; 100% for septicaemic plague Incidence declining globally since early 20th C Some countries (including Tanzania) continue to be affected Reservoirs: Rodents, Fleas (Xenopsilla spp) Plague foci: World wide in countries lying between 50?N and 35?S; in Tanzania-central, northern and eastern parts
16 :
17 : EPIDEMIOLOGY-3 Epidemic types: Sylvatic (rural) plague, Domestic (urban) plague Risk factors: Occupation (hunters, farmers) Poor housing Sleeping on the floor Not keeping cats Socio-cultural factors
18 : CONTROL AND PREVENTION-1 Control of epidemics Mitigate public hysteria Treat cases Closely monitor contacts Investigate all deaths Kill fleas (insecticides) Kill rodents (rodenticides) when flea index <0.5
19 : CONTROL AND PREVENTION-2 Case recognition, medical intervention and field investigation Identify the most likely source of infection in the area Institute appropriate sanitation and control measures to stop the exposure source Ensure dissemination of information concerning areas with active plague transmission, the clinical features of plague and the case definition to health workers Verify that patients have been placed on appropriate antibiotic treatment and that local supplies of antibiotics are adequate to handle further cases Isolate pneumonic plague patients
20 : CONTROL AND PREVENTION-3 Vaccine not available for wide use Continuous surveillance of rodent and human plague Conduct investigation to identify animals and flea species that are implicated in the plague enzootic cycle in the region and develop a programme on environmental management to limit its potential spread Active long-term surveillance of zoonotic foci and rapid response to reduce exposure during epizootic outbreaks
21 : Yersinia enterocolotica
22 : CULTURAL CHARACTERISTICS Capsules in vivo, not in culture Multiplies at 4?C Slow growth on artificial media Selective/enrichment media needed for isolation from faecal specimens
23 : ANTIGENIC STRUCTURE 6 biotypes Several serotypes, 3, 8 and 9 responsible for most human infections Enterotoxin produced at T <30?C
24 : PATHOGENESIS Faeco-oral transmission Causes gastroenteritis; sometimes septicaemia and mesenteric lymphadenitis in the elderly LAB. DIAGNOSIS Specimens Faeces, Blood Tests Culture: cold enrichment, subculture on selective media Serology
25 : Yersinia pseudotuberculosis
26 : GENERAL FEATURES Non capsulated Grows poorly on MCA ANTIGENIC STRUCTURE Serotypes 1-6, type 1 most common Six O groups (I-IV)
27 : PATHOGENESIS Zoonosis Causes mesenteric adenitis in man LAB. DIAGNOSIS Specimens Mesenteric lymphnode biopsy, Blood Tests Culture: incubate at 37?C for 18 hrs Serology
28 : PASTEURELLA Genus: Pasteurella Species of importance: P. multocida P. haemolytica P. pneumotropica P. ureae
29 : P. multocida Gram negative coccobacilli, smaller than Yersiniae Non-motile, non-sporing Capsulated in culture Bipolar staining with methylene blue Aerobic, facultatively anaerobic Does not grow on MCA Oxidase positive
30 : ANTIGENIC STRUCTURE 15 serotypes, 4 capsular Ags and 11 somatic Ags PATHOGENESIS Zoonosis, virulent to animals and birds Rare human infections: local abscess Meningitis RT infections LAB. DIAGNOSIS Specimens Depending on clinical presentation Tests Culture

 

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