L24 - Medical Microbiology Laboratory (Yersinia spp. & others) by Hussein Abid

1. Medical Microbiology Laboratory
Gram Negative Bacilli – Enterobacteriaceae
(Yersinia and others)
Hussein A. Abid
Medical Laboratory Scientist
Member at American Society of Microbiology
Chairman of Iraqi Medical Laboratory Association
Teacher at Middle Technical University

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Enterobacteriaceae
 A large Family of aerobic bacterial flora of intestine of
humans and other animals.
 Its members are non-spore forming, non acid-fast,
gram negative bacilli.
 Capsule (variable)
 Motility (variable)
 Aerobic and facultatively anaerobic, grow readily on
ordinary media
 Ferment glucose, reduce nitrates to nitrites, catalase
positive but oxidase negative.

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CLASSIFICATION ACCORDING TO LACTOSE
FERMENTATION
Lactose Non-fermentative Lactose Fermentative
Salmonella spp.
Shigella spp.
Proteus spp.
Yersinia spp.
E. coli
Klebsiella spp.
Enterobacter spp.
Citrobacter spp.
Culture media used to differentiate lactose fermenter from
lactose non fermenter are:
1. MacConkey’s (Mac) agar medium
2. Eosin Methylene Blue (EMB) agar medium
3. Salmonella-Shigella (SS) agar medium
4. Triple Sugar Iron (TSI) agar medium

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TAXONOMY
Scientific name Rank
• Enterobacteriaceae Family
• Yersinia Genus
• Y. enterocolitica
• Y. pseudotuberculosis
• Y. pestis
Species
(medically important spp.)

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Yersinia spp.
 Gram-negative, non-motile rod-
shaped coccobacillus
 With no spores
 Facultative anaerobic organism
that can infect humans via the
oriental rat flea.
 Yersinia able to not only survive but
actively proliferate at temperatures
as low as 1-4 ºC.
Oriental rat flea infected with
plague

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Yersinia spp.
 Y. enterocolitica
 Acquired via consumption of food or water contaminated with
animal feces
 Causes inflammation of the intestinal tract
 Y. pseudotuberculosis
 Similar to Y. enterocolitica but produces a less severe intestinal
inflammation
 Y. pestis
 Bubonic plague-characterized by high fever and swollen, painful
lymph nodes called buboes
 Pneumonic plague-rapidly developing infection of the lungs

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Yersinia pestis (hosts)
 Mammalian
o Human
o Rodent
 Insects
o Xenopsylla cheopis
Xenopsylla cheopis

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Yersinia infections
Y. pestis
 Bubonic plague with swollen and painful axillary (arm pit) & inguinal
(groin) lymph nodes (buboes)
 Transmitted from mammalian reservoirs by flea (arthropod)
bites or contact with contaminated animal tissues
 Pneumonic plaque
 Person-to-person spread
Yersinia enterocolitica
 Enterocolitis
 Transfusion-related septicemia

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Yersinia diagnosis
 Characteristic symptoms are usually sufficient for diagnosis
 Culture, staining and rapid detection test may be used
 Using Autonomous Pathogen Detection System (APDS)
APDS
rapid detection test

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TAXONOMY
Scientific name Rank
• Enterobacteriaceae Family
• Morganella Genus
• M. morganii Species
(medically important spp.)

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Morganella morganii
 Gram-negative bacteria
 It has a commensal relationship
within the intestinal tracts of
humans, mammals, and reptiles
as normal flora
 M. morganii is uncommon cause of community-acquired
infection and it is most often encountered in
postoperative and other nosocomial infections such as
urinary tract infections.

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M. morganii (culture)
 Blood agar: medium to large sized, greyish to off-white,
round, opaque, elevated (beta-hemolytic) colonies.

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BIOCHEMICAL TESTS
1. Catalase: positive (+ve)
2. Oxidase: negative (-ve)
3. Motility: motile
4. Triple Sugar Iron (TSI): K/A, gas (+), H2S (-)
5. Indole, MR, VP, Citrate (IMViC): +, +, -, -
6. Urease test: positive (+ve)