Comparison of phenotypic tests for detecting penicillin G resistance with presence of blaZ gene in Staphylococcus aureus isolated from bovine intramammary infections

Few studies have described the relationship between genotypic and phenotypic methods for detecting penicillin resistance in Staphylococcus aureus isolated from bovine intramammary infection (IMI). Six phenotypic methods for penicillinase detection were compared with a genotypic method testing the pr...

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Bibliographic Details
Published in:Journal of dairy research 2015-08, Vol.82 (3), p.317-321
Main Authors: Russi, Norma B, Maito, Julia, Dieser, Silvina A, Renna, María S, Signorini, Marcelo L, Camussone, Cecilia, Neder, Verónica E, Pol, Martín, Tirante, Liliana, Odierno, Liliana M, Calvinho, Luis F
Format: Article
Language:English
Subjects:
Animals
benzylpenicillin
beta-lactamase
beta-Lactamases - genetics
Cattle
DNA, Bacterial - analysis
False Negative Reactions
Female
genes
Genotype
mastitis
Mastitis, Bovine - microbiology
Microbial Sensitivity Tests
minimum inhibitory concentration
Penicillin G
Penicillin Resistance
Penicillinase - analysis
Phenotype
Staphylococcal Infections - veterinary
Staphylococcus aureus
Staphylococcus aureus - drug effects
Staphylococcus aureus - enzymology
Staphylococcus aureus - genetics
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Summary:Few studies have described the relationship between genotypic and phenotypic methods for detecting penicillin resistance in Staphylococcus aureus isolated from bovine intramammary infection (IMI). Six phenotypic methods for penicillinase detection were compared with a genotypic method testing the presence of the β-lactamase gene blaZ in Staph. aureus (n = 150) isolated from bovine IMI. Highest sensitivities and specificities were observed for disk diffusion (DD) (93 and 97·4%), minimum inhibitory concentration (MIC) (90·3 and 97·4%), Cefinase™ (85·9 and 97·4%) and Diatabs™ (85·7 and 98·7%). The estimated cut-off points estimated in the present study can be considered close to the ones indicated by CLSI (2013). The molecular detection of blaZ gene is the only method that may indicate the real or potential capacity of producing β-lactamase in Staph. aureus. Considering that from a clinical standpoint a false negative result from a phenotypic test is the most unfavourable situation, a combination of standard DD with Diatabs™ or Cefinase™ should be performed by routine mastitis laboratories to minimise false negative results.
ISSN:0022-0299
1469-7629
1469-7629
DOI:10.1017/S0022029915000242