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Mastitis: Pseudomonas aeruginosa

ISSN 2398-2993

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Synonym(s): Gangrenous toxic dairy mammary gland tissue inflammation inflammatory


  • Cause: Pseudomonas aeruginosa.
  • Signs: mild to severe mastitis.
  • Diagnosis: bacterial culture of milk samples.
  • Treatment: antibiotics, although often challenging.
  • Prognosis: guarded/poor.

Geographic incidence

  • Worldwide.

Age predisposition

  • All milking cows.

Public health considerations

  • Mastitis is often the main reason for antibiotic use on dairy farms and better control of mastitis in general is, therefore, crucial if we are to reduce the requirement for antibiotics and reduce the risk of antimicrobial resistance.

Cost considerations

  • Mastitis is the most costly infectious disease affecting dairy cattle, accounting for 38% of the total direct costs of the common production diseases.



  • In cases of P. aeruginosa Pseudomonas aeruginosa mastitis, the bacterium has been detected in contaminated wash hoses in milking parlors, in water and spray nozzles, and in contaminated antibiotic preparations.
  • Water supplies of all types (wells, troughs, ponds, parlor wash hoses, and sprinkler pens) are the major source of P. aeruginosa on dairy farms.
  • The ability to survive in moist environments contributes greatly to this organism’s ubiquitous presence in nature.
  • P. aeruginosa has also been isolated from waste feed, soil, manure, and animal skin. The presence of unsanitary housing and bedding conditions can contribute to occasional outbreaks of P. aeruginosa infections.

Predisposing factors



  • The pathogenicity of P. aeruginosa is governed by a variety of virulence factors.
    • Bacterial lipopolysaccharide (LPS), a component of the outer leaflet of all Gram negative bacteria protects against the lytic effects of complement, confers resistance to phagocytosis, and facilitates colonization.
    • Pili and flagella, both mediate bacterial adherence and the latter also confers motility.
    • Bacterial secretion of exotoxin A, exoenzyme S, and elastase facilitate invasion and dissemination.
    • P. aeruginosa-derived elastase is also reported to inhibit monocyte and neutrophil chemotaxis and respiratory burst.
    • P. aeruginosa are able to form a biofilm, which protects them from leukocyte-mediated phagocytosis and complement activation, and confers resistance to antibiotics and disinfectants.
  • Together, these virulence factors contribute to the ability of P. aeruginosa to establish infection and resist host innate immune defenses.


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Further Reading


Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Huijps K, Lam T J & Hogeveen H (2008) Costs of mastitis: facts and perception. J Dairy Res 75, 113–20 PubMed.
  • Bannerman D, Chockalingam A, Paape M & Hope J (2005) The bovine innate immune response during experimentally-induced Pseudomonas aeruginosa mastitis. Vet Immunol Immunopathol 107 (3-4), 201–215.
  • Power E (2003) Gangrenous mastitis in dairy herds. Vet Rec 153, 791–792 PubMed.
  • Lerouge I & Vanderleyden J (2002) O-antigen structural variation: mechanisms and possible roles in animal/plant-microbe interactions. FEMS Microbiol Rev 26, 17–47 PubMed.
  • Lyczak J B, Cannon C L & Pier G B (2000) Establishment of Pseudomonas aeruginosa infection: lessons from a versatile opportunist. Microbes Infect 2, 1051–1060 PubMed.
  • Daly M (1999) Molecular analysis of Pseudomonas aeruginosa: epidemiological investigation of mastitis outbreaks in Irish dairy herds. Appl Environ Microbiol 65, 2723–2729.
  • Van Delden C & Iglewski B H (1998) Cell-to-cell signaling and Pseudomonas aeruginosa infections. Emerg Infect Dis 4, 551–560.
  • Kossaibati M A & Esslemont R J (1997) The costs of production diseases in dairy herds in England. Vet J 154, 41–51.
  • McLennan M W, Kelly W R & O’Boyle D (1997) Pseudomonas mastitis in a dairy herd. Aust Vet J 75, 790–792 PubMed.
  • Ijiri Y, Matsumoto K, Kamata R, Nishino N, Okamura R, Kambara T & Yamamoto T (1994) Suppression of polymorphonuclear leucocyte chemotaxis by Pseudomonas aeruginosa elastase in vitro: a study of the mechanisms and the correlation with ring abscess in pseudomonal keratitis. Int J Exp Pathol 75, 441–451 PubMed.
  • Kharazmi A & Nielsen H (1991) Inhibition of human monocyte chemotaxis and chemiluminescence by Pseudomonas aeruginosa elastase. APMIS 99, 93–95 PubMed.
  • Erksine R J G, Unflat R J, Eberhart L J, Hutchinson C R, Hicks & Spencer (1987) Pseudomonas mastitis: difficulties in detection and elimination from contaminated wash-water systems. JAVMA 191, 811–815 PubMed.
  • Kirk J H & Bartlett P C (1984) Nonclinical Pseudomonas aeruginosa mastitis in a dairy herd. JAVMA 184, 671–673 PubMed.
  • Packer R A (1977) Bovine mastitis caused by Pseudomonas aeruginosa. JAVMA 170, 1166 PubMed.
  • Howell D (1972) Survey on mastitis caused by environmental bacteria. Vet Rec 90, 654–657 PubMed.
  • Malmo J, Robinson B & Morris R S (1972) An outbreak of mastitis due to Pseudomonas aeruginosa in a dairy herd. Aust Vet J 48, 137–139 PubMed.

Other sources of information

  • Radostits O M, Blood D C & Gay C C (1994) Veterinary Medicine. 8th edn. pp 598. Bailliere Tindall, UK.