Methicillin resistance among staphylococci isolated from dogs

Kinga Gortel From the Departments of Veterinary Clinical Medicine (Gortel, Campbell, Weisiger), Veterinary Pathobiology (Kakoma), and Veterinary Biosciences (Whittem, Schaeffer), College of Veterinary Medicine, University of Illinois, Urbana, IL 61802.

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Karen L. Campbell From the Departments of Veterinary Clinical Medicine (Gortel, Campbell, Weisiger), Veterinary Pathobiology (Kakoma), and Veterinary Biosciences (Whittem, Schaeffer), College of Veterinary Medicine, University of Illinois, Urbana, IL 61802.

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 DVM, MS
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Ibulaimu Kakoma From the Departments of Veterinary Clinical Medicine (Gortel, Campbell, Weisiger), Veterinary Pathobiology (Kakoma), and Veterinary Biosciences (Whittem, Schaeffer), College of Veterinary Medicine, University of Illinois, Urbana, IL 61802.

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Ted Whittem From the Departments of Veterinary Clinical Medicine (Gortel, Campbell, Weisiger), Veterinary Pathobiology (Kakoma), and Veterinary Biosciences (Whittem, Schaeffer), College of Veterinary Medicine, University of Illinois, Urbana, IL 61802.

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David J. Schaeffer From the Departments of Veterinary Clinical Medicine (Gortel, Campbell, Weisiger), Veterinary Pathobiology (Kakoma), and Veterinary Biosciences (Whittem, Schaeffer), College of Veterinary Medicine, University of Illinois, Urbana, IL 61802.

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Rita M. Weisiger From the Departments of Veterinary Clinical Medicine (Gortel, Campbell, Weisiger), Veterinary Pathobiology (Kakoma), and Veterinary Biosciences (Whittem, Schaeffer), College of Veterinary Medicine, University of Illinois, Urbana, IL 61802.

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Abstract

Objective

To determine whether methicillin-resistant staphylococci from dogs expressed the mecA gene and to determine what proportion of canine staphylococcal isolates positive for the mecA gene were resistant to oxacillin and other antibiotics.

Sample Population

25 methicillin-resistant (10 coagulase-positive and 15 coagulase-negative) and 15 methicillin-susceptible (8 coagulase-positive and 7 coagulase-negative) staphylococci isolated from dogs.

Procedure

All strains were tested for methicillin resistance by use of oxacillin agar screening and identified by use of standard techniques. Minimum inhibitory concentrations of 16 antibiotics were determined for all 40 isolates. A polymerase chain reaction method targeting a 533-basepair fragment of the mecA gene was used to detect mecA gene expression.

Results

23 of the 25 methicillin-resistant isolates and none of the methicillin-susceptible isolates possessed the mecA gene. For 10 of 16 antibiotics, the proportion of mecA-positive isolates that were resistant or of intermediate susceptibility was significantly higher than the proportion of mecA-negative isolates that were resistant or of intermediate susceptibility. Only 1 methicillin-resistant coagulase-positive isolate was identified as Staphylococcus intermedius; the other 9 were identified as S aureus.

Conclusions and Clinical Relevance

Results confirm that staphylococci isolated from dogs may have methicillin resistance mediated by the mecA gene. Isolates positive for the mecA gene were more likely to be resistant to various antibiotics than were isolates negative for the mecA gene. Results suggest that in dogs, infections caused by staphylococci that have the mecA gene may be difficult to treat because of resistance to antibiotics. (Am J Vet Res 1999;60:1526–1530)

Abstract

Objective

To determine whether methicillin-resistant staphylococci from dogs expressed the mecA gene and to determine what proportion of canine staphylococcal isolates positive for the mecA gene were resistant to oxacillin and other antibiotics.

Sample Population

25 methicillin-resistant (10 coagulase-positive and 15 coagulase-negative) and 15 methicillin-susceptible (8 coagulase-positive and 7 coagulase-negative) staphylococci isolated from dogs.

Procedure

All strains were tested for methicillin resistance by use of oxacillin agar screening and identified by use of standard techniques. Minimum inhibitory concentrations of 16 antibiotics were determined for all 40 isolates. A polymerase chain reaction method targeting a 533-basepair fragment of the mecA gene was used to detect mecA gene expression.

Results

23 of the 25 methicillin-resistant isolates and none of the methicillin-susceptible isolates possessed the mecA gene. For 10 of 16 antibiotics, the proportion of mecA-positive isolates that were resistant or of intermediate susceptibility was significantly higher than the proportion of mecA-negative isolates that were resistant or of intermediate susceptibility. Only 1 methicillin-resistant coagulase-positive isolate was identified as Staphylococcus intermedius; the other 9 were identified as S aureus.

Conclusions and Clinical Relevance

Results confirm that staphylococci isolated from dogs may have methicillin resistance mediated by the mecA gene. Isolates positive for the mecA gene were more likely to be resistant to various antibiotics than were isolates negative for the mecA gene. Results suggest that in dogs, infections caused by staphylococci that have the mecA gene may be difficult to treat because of resistance to antibiotics. (Am J Vet Res 1999;60:1526–1530)

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