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 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
Envelope (F-1) antigen: This is a protein-polysaccharide complex which is highly expressed at 37 degrees in the mammalian host but not in the flea and is anti-phagocytic.
V and W proteins: These plasmid-coded proteins are associated with rapid proliferation and septicemia.

10. ANTIGENIC STRUCTURE-2 Other virulence factors:-
Low calcium response (lcr) gene
Yops (Yersinia outer proteins)
Coagulase produced at 28C
Plasminogen activator
Low calcium response (lcr) : This is a plasmid-coded gene that enables the organism to grow in a low Ca++ (intracellular) environment. It also coordinates the production of several other virulence factors, such as V, W and yops (Yersinia outer proteins).
Yops: A group of 11 proteins, which are coded by plasmids, are essential for rodent pathogenesis and are responsible for cytotoxicity, inhibition of phagocyte migration and engulfment and platelet aggregation.
Coagulase and Plasminogen activator: Both of these are plasmid-coded proteins.
Coagulase is responsible for micro thrombi formation
Plasminogen activator promotes the dissemination of the organism. It also destroys C3b on the bacterial surface, thus attenuating phagocytosis.

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 Tests 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

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 LAB. DIAGNOSIS 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

31. Reference