Pseudomonas spp in Horses (Equis) | Vetlexicon
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Pseudomonas spp

ISSN 2398-2977

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Introduction

Classification

Taxonomy

  • Family: Pseudomonaceae.
  • Genus:PseudomonasandBurkholderia.
  • 27 recognized species, the most important in horses are:B. aeruginosa,B. pseudomallei, andP. mallei.

Etymology

  • Gk:pseudes- false;monas- a unit, alone.

Distribution

  • Worldwide.

Significance

Active Forms

Active Form 1

Morphology

  • Gram-negative bacilli.
  • Dimensions: 0.5-1.0 µm by 1.5-5.0 µm.
  • Some are encapsulated.
  • Polar flagellae confer motility.
  • Fimbriae present.

Taxonomy

  • Protein exotoxins produced by various species, eg PA toxin, exotoxin S, elastase, and alkaline protease.
  • Pyocyanin (blue-green pigment) used to identifyP. aeruginosa  Pseudomonas aeruginosa  .
  • Oxidase-positive.
  • P. aeruginosadoes not ferment carbohydrates.B. malleiandB.pseudomalleiferment glucose.

Color

  • Depends on species.

Tolerances

Temperature
  • Grow at 4-42°C.
Humidity
  • Prefer wet environments.
Other
  • Survive in environment.

Development

Growth
  • Obligate aerobes.
  • Grow on all common media.

Resting Forms

Clinical Effects

Epidemiology

Habitat

  • Environmental contamination; saprophytes.
  • Infected horses are the reservoir forB. mallei.

Transmission

  • Endogenous or exogenous.

Pathological effects

  • Specific immune responses relatively unimportant.
  • Immunosuppression may predispose to infection.
  • Depends on species.
  • P. aeruginosa  Pseudomonas aeruginosa  is a secondary invader. Contaminates areas of the body where normal flora reduced or absent   →   liberates exotoxins   →   tissue destruction   →   keratitis   Keratitis: overview  , placentitis, septicemia, arthritis, pneumonia, endocarditis   Heart: endocarditis  and other infections.
  • P. pseudomalleiis associated with glanders   Glanders  . Invasion via intestinal wall   →   bacteremia   →   localization in respiratory tract and skin   →   miliary nodule formation.

Other host effects

  • Can colonize areas of the body with reduced numbers of normal flora or when tissue is injured or compromised.
  • B. pseudomalleiis associated with meliodosis.

Control

Control via animal

  • Correct immune compromising condition.
  • Avoid contact with contaminated fomites.

Control via chemotherapies

Control via environment

  • Avoid contamination.

Vaccination

  • None available.

Diagnosis

Useful samples

  • Tissues, swabs, serum.

Field diagnosis

  • Mallein test forB. mallei: antigen ('mallein') injected intradermally into lower eyelid. Positive reaction (edema, blepharospasm, conjunctivitis   Conjunctivitis: overview  ) read at 48 hours.

Laboratory diagnosis


Biohazard cabinet must be used when working withB. malleiorB. pseudomallei
  • Culture on blood agar and identification by biochemical tests.
  • Serology: complement fixation test forB. pseudomallei.

Further Reading

Publications

Refereed papers

  • Recent references for PubMed and VetMedResource.
  • Sweeney C R & Irby N L (1996) Topical treatment of Pseudomonas spp-infected corneal ulcers in horses: 70 cases (1977-1994). JAVMA 209 (5), 954 PubMed.
  • Verma R D, Venkateswaran K S, Sharma J K & Agarwal G S (1994) Potency of partially purified malleo-proteins for mallein test in the diagnosis of glanders in equines. Vet Microbiol 41 (4), 391-397 PubMed.
  • Ensink J M, Vanklingeren B, Houwers D J et al (1993) In vitro susceptibility to antimicrobial drugs of bacterial isolates from horses in the Netherlands. Equine Vet J 25 (4), 309-313 PubMed.