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New perspectives on the bacteriology and antimicrobial susceptibility of dog bite wounds

Abstract number: 1733_735

Meyers B., Schoeman J., Goddard A., Seakemela E., Picard J.

Objectives: In spite of dog bite wounds being a common reason for dogs requiring veterinary care, there is surprisingly little data on the bacteriology of bite wounds. Thus, a prospective study was performed on dogs presenting at the Onderstepoort Veterinary Academic Hospital, University of Pretoria, and a nearby animal shelter with various grades of bite wound.

Methods: Fifty dogs with bite wounds inflicted within the previous 72 hours were selected. This represented 104 wounds. Wounds were clinically graded according to severity and evaluated cytologically. Swabs were collected from all wounds for bacterial culture. Wounds were classified as infected or non-infected. Infection was diagnosed if 2 of the following 3 criteria were met: macroscopic purulence, phagocytosed bacteria present or if the wounded dog had pyrexia. Non-infected wounds were either sterile (established by culture) or contaminated (culture positive but bacteria not phagocytosed on cytology). All wounds were cultured aerobically and anaerobically and all aerobic cultures were evaluated for antibiotic susceptibility.

Results: Of the 104 wounds, 21 were judged to be infected and 83 non-infected. Seventeen (16%) of all wounds were sterile were also classified as non-infected. This was statistically significant (P = 0.02). Of the 84% that were culture positive, 16% grew aerobes, 1% anaerobes and 67% a mixture of aerobes and anaerobes. A total of 211 isolates were cultured representing a mean of 2.1 isolates per wound. Of the aerobes cultured, 22%, 20% and 17% belonged to Pasteurella, Streptococcus and Staphylococcus species, respectively. Within these groups, Pasteurella multocida (65%) and Staphylococcus intermedius (70%) were predominant. Pasteurella canis and pyogenic streptococci were common in infected wounds, whereas Bacillus spp., Actinomyces spp. and the oral streptococci were usually found in contaminated wounds. Three anaerobic genera were cultured, namely, Prevotella, Clostridium and Peptostreptococcus, and were usually associated with wounds with dead space. This is also the first recorded case of Capnocytophaga canimorsus in an infected dog bite wound. Significantly, clinical examination and cytological assessment were capable of establishing whether antibiotics were required or not. Although no single antibiotic was considered to be effective against all the bacteria, in vitro, potentiated sulphonamides, ampicillin and amoxycillin plus clavulanic acid gave the best results.

Table 1. Percentage antibiotic susceptibility of the most common bacteria

 Susceptibility (%)a
Pasteurella multocida n = 30Pasteurellaceae n = 13Staphylococcus intermedius n = 23Pyogenicb streptococci n = 27Escherichia coli n = 10  
Amoxycillin-clavulanate87100917880
Cloxacillin6483907022
Penicillin G9392658110
Cephalothin93921008620
Ceftiofur9344658144
Enrofloxacin938591750
Orbifloxacin6490744850
Doxycycline9385576710
-Sulphamethazole + trimethoprim90100748960
Gentamicin4392911960
Amikacin6590100789
Kanamycin8392951150
Lincomycin173140010
Lincospectin335033n/a0
Tylosin7692957710
aShaded areas indicate susceptibility of 50% or less.bPyogenic streptococci included: S. canis, S. pyogenes, S. agalactiae, Group-C streptococci.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Subject:
Location: ICC, Munich, Germany
Presentation type:
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