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 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.
Facultad de Ciencias Veterinarias,Universidad Nacional del Litoral,Santa Fe. Argentina. Rvdo. Padre Kreder 2805,(3080) Esperanza,Santa Fe,Argentina.
Norma B
NB
Russi
Lactodiagnóstico Sur. Pedro Goyena 3199,(1636) Olivos,Buenos Aires,Argentina.
Julia
J
Maito
Facultad de Ciencias Exactas,Físico-Químicas y Naturales,Universidad Nacional de Río Cuarto,Ruta 36 Km601,(5804) Río Cuarto,Córdoba,Argentina.
Silvina A
SA
Dieser
Facultad de Ciencias Veterinarias,Universidad Nacional del Litoral,Santa Fe. Argentina. Rvdo. Padre Kreder 2805,(3080) Esperanza,Santa Fe,Argentina.
María S
MS
Renna
Consejo Nacional de Investigaciones Científicas y Técnicas,Avda. Rivadavia 1917,(1033) Ciudad Autónoma de Buenos Aires,Argentina.
Marcelo L
ML
Signorini
Consejo Nacional de Investigaciones Científicas y Técnicas,Avda. Rivadavia 1917,(1033) Ciudad Autónoma de Buenos Aires,Argentina.
Cecilia
C
Camussone
Estación Experimental Agropecuaria Rafaela,Instituto Nacional de Tecnología Agropecuaria,Ruta 34,km 227. (2300) Rafaela,Santa Fe,Argentina.
Verónica E
VE
Neder
Lactodiagnóstico Sur. Pedro Goyena 3199,(1636) Olivos,Buenos Aires,Argentina.
Martín
M
Pol
Lactodiagnóstico Sur. Pedro Goyena 3199,(1636) Olivos,Buenos Aires,Argentina.
Liliana
L
Tirante
Facultad de Ciencias Exactas,Físico-Químicas y Naturales,Universidad Nacional de Río Cuarto,Ruta 36 Km601,(5804) Río Cuarto,Córdoba,Argentina.
Liliana M
LM
Odierno
Facultad de Ciencias Veterinarias,Universidad Nacional del Litoral,Santa Fe. Argentina. Rvdo. Padre Kreder 2805,(3080) Esperanza,Santa Fe,Argentina.
Luis F
LF
Calvinho
D000818:Animals; D002417:Cattle; D004269:DNA, Bacterial / Q000032:analysis; D005188:False Negative Reactions; D005260:Female; D005838:Genotype; D008414:Mastitis, Bovine / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D010400:Penicillin G; D010403:Penicillin Resistance; D010405:Penicillinase / Q000032:analysis; D010641:Phenotype; D013203:Staphylococcal Infections / Q000662:veterinary; D013211:Staphylococcus aureus / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D001618:beta-Lactamases / Q000235:genetics*
D004269:DNA, Bacterial; D010405:Penicillinase; D001618:beta-Lactamases; D010400:Penicillin G
      blaZ; Staphylococcus aureus; intramammary infections; penicillin resistance