Expression of genes encoding resistance in Staphylococcus spp. isolated from bovine subclinical mastitis in Brazil.

Eveline Zuniga,Marco Antonio Laes,Priscilla Anne Melville,Lilian Abgail Ribeiro De Oliveira,Nilson Roberti Benites,Priscila Luiza Mello,Paulo Eduardo Brandão,Aline Santana Da Hora,Sueli Akemi Taniwaki,Sheila Oliveira De Souza Silva

doi:10.3855/jidc.12611

Abstract

Staphylococci are the most important agents associated with bovine mastitis. This study aimed at characterizing resistance factors to antimicrobials in Staphylococcus spp. isolated from the milk of cows with subclinical mastitis. In vitro resistance of 243 Staphylococcus spp. isolates to antimicrobials commonly used in clinical practice was evaluated. The detection and expression of genes encoding resistance mecA (gene encoding penicillin binding protein 2a) mecALGA251 (mecA homologue), blaZ (gene encoding penicillin resistance), femA and femB (genes encoding essential factors - A and B - for the expression of methicillin resistance) and aacA-aphD (gene encoding for a bifunctional enzyme that confers resistance to gentamicin) using PCR and RT-PCR was investigated. One or more genes encoding resistance to different antimicrobials were detected in 184 Staphylococcus spp. The femA and femB genes were the most frequent. Regarding the variables' detection (N = number of strains) and expression (% of strains), the following results were obtained: blaZ (N = 40 - 82.5%), femA (N = 147 - 47.6%), aacAaphD (N = 30 - 43.3%), femB (N = 138 - 29.7%), mecA (N = 33 - 27.3%), mecALGA251 (N = 01 - 0.0%). There was a higher occurrence of phenotypic resistant strains for amoxicillin, ampicillin and penicillin in isolates positive for detection and/or expression of blaZ gene when compared with the other genes. The present study provides new information on genotypic traits of Staphylococcus isolates from bovine subclinical mastitis especially regarding the evaluation of expression of genes associated with antimicrobial resistance in Staphylococcus spp. using molecular tools.

Highlights

IntroductionThis study aimed at characterizing resistance factors to antimicrobials in Staphylococcus spp. isolated from the milk of cows with subclinical mastitis
Staphylococci are the most important agents associated with bovine mastitis
Considering the importance of the Staphylococcus genus in mastitis etiology, we evaluated the resistance of Staphylococcus spp. isolated from bovine subclinical mastitis to the most commonly used antimicrobial agents in clinical practice, evaluating phenotype and genotype characteristics

Summary

Introduction

This study aimed at characterizing resistance factors to antimicrobials in Staphylococcus spp. isolated from the milk of cows with subclinical mastitis. Results: One or more genes encoding resistance to different antimicrobials were detected in 184 Staphylococcus spp. samples. Regarding the variables’ detection (N = number of strains) and expression (% of strains), the following results were obtained: blaZ (N = 40 – 82.5%), femA (N = 147 – 47.6%), aacAaphD (N = 30 – 43.3%), femB (N = 138 – 29.7%), mecA (N = 33 – 27.3%), mecALGA251 (N = 01 – 0.0%). Conclusions: The present study provides new information on genotypic traits of Staphylococcus isolates from bovine subclinical mastitis especially regarding the evaluation of expression of genes associated with antimicrobial resistance in Staphylococcus spp. using molecular tools. Bacterial resistance to beta-lactam antimicrobials that has been described in isolates obtained from milk produced by mastitis infected cows [4], is the result of different mechanisms.

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