yersinia & pasteurella
TRANSCRIPT
YERSINIA AND PASTEURELLA
Eligius Lyamuya, MD, MMed, PhD
Department of Microbiology and Immunology, Muhimbili University of Health
and Allied Sciences
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
YERSINIA
Family: Enterobacteriaceae
Genus: Yersinia
Species of medical importance:• Yersinia pestis• Yersinia enterocolitica• Yersinia pseudotuberculosis
GENERAL CHARACTERISTICS
• Coccobacillary, ovoid or rod shaped, bipolar staining
• Gram negative
• Aerobic or facultatively anaerobic
• Grow on ordinary media
• Best growth temp. 25-30C• Oxidase -ve, Catalase +ve, Indole -ve, ONPG
+ve, Urease +ve except Y. pestis
Stained preparation showing Yersinia pestis
Yersinia pestis
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
Biotypes
Biotype Glycerol Nitrite
acidification reduction
Y. pestis var orientalis - +
Y. pestis var antiqua + +
Y. pestis var medievalis + -
ANTIGENIC STRUCTURE-1
• LPS
• Capsular (envelope) antigenic complexF1 antigenHeat labileDevelops at 37C
• Somatic antigenic complexV and W antigensHeat stableDevelops at 20C and 37C
ANTIGENIC STRUCTURE-2
• Other virulence factors:-
Low calcium response (lcr) geneYops (Yersinia outer proteins)
Coagulase produced at 28CPlasminogen activator
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
CLINICAL TYPES
• Bubonic
• Septicaemic
• Pneumonic
• Others:Plague meningitisTonsillar or pharyngeal plaguePlague carbuncle
LABORATORY DIAGNOSIS
• SpecimensBubo aspirateSputumBloodOthers depending on clinical presentation
• TestsStaining (Wayson’s, methylene blue, Gram)CultureSerology
EPIDEMIOLOGY-1
• Disease of antiquity
• First documented epidemic ?1320 BC (Biblical evidence)
• Major pandemics:Justinian plague: -6th CBlack death: -14th COriental plague: -Late 19th C
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
50N and 35S; in Tanzania-central, northern and eastern parts
EPIDEMIOLOGY-3
• Epidemic types: Sylvatic (rural) plague, Domestic (urban) plague
• Risk factors:Occupation (hunters, farmers)Poor housingSleeping on the floorNot keeping catsSocio-cultural factors
CONTROL AND PREVENTION-1
• Control of epidemicsMitigate public hysteriaTreat casesClosely monitor contactsInvestigate all deathsKill fleas (insecticides)Kill rodents (rodenticides) when flea index <0.5
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 sourceEnsure 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
CONTROL AND PREVENTION-3
• Vaccine not available for wide use• Continuous surveillance of rodent and human
plagueConduct 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
Yersinia enterocolotica
CULTURAL CHARACTERISTICS
• Capsules in vivo, not in culture
• Multiplies at 4C• Slow growth on artificial media
• Selective/enrichment media needed for isolation from faecal specimens
ANTIGENIC STRUCTURE
• 6 biotypes• Several serotypes, 3, 8 and 9 responsible for most
human infections
• Enterotoxin produced at T <30C
PATHOGENESIS • Faeco-oral transmission• Causes gastroenteritis; sometimes septicaemia
and mesenteric lymphadenitis in the elderly
LAB. DIAGNOSIS• Specimens
Faeces, Blood
• TestsCulture: cold enrichment, subculture on selective
mediaSerology
Yersinia pseudotuberculosis
GENERAL FEATURES•Non capsulated•Grows poorly on MCA
ANTIGENIC STRUCTURE•Serotypes 1-6, type 1 most common•Six O groups (I-IV)
PATHOGENESIS •Zoonosis•Causes mesenteric adenitis in man
LAB. DIAGNOSISSpecimens•Mesenteric lymphnode biopsy, Blood
Tests•Culture: incubate at 37C for 18 hrs•Serology
PASTEURELLA
Genus: Pasteurella
Species of importance:
• P. multocida
• P. haemolytica
• P. pneumotropica
• P. ureae
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
ANTIGENIC STRUCTURE•15 serotypes, 4 capsular Ags and 11 somatic Ags
PATHOGENESIS •Zoonosis, virulent to animals and birds•Rare human infections:
local abscessMeningitisRT infections
LAB. DIAGNOSISSpecimens•Depending on clinical presentationTests •Culture