Molecular identification of coagulase-negative staphylococci isolated from bovine mastitis and detection of β-lactam resistance

Abstract

Introduction: Bovine mastitis is a frequent cause of economic loss in dairy herds. Coagulase-negative staphylococci (CoNS) are increasing in importance as cause of bovine intramammary infection throughout the world in recent years. CoNS have been isolated from milk samples collected from cows with clinical and subclinical mastitis in several countries. Identification of mastitis pathogens is important when selecting appropriate antimicrobial therapy. Methodology: A total of 93 strains of Staphylococcus spp isolated from bovine mastitis in Argentina between 2010 and 2013 were identified by PCR-restriction fragment length polymorphism (PCR-RFLP) using the gap gene and were tested for the presence of blaZ and mecA genes by PCR and for the susceptibility to penicillin and cefoxitin by disk diffusion. Results: The most common CoNS species was S. chromogenes 46.2% (43/93), followed by S. devriesei 11.8% (11/93) and S. haemolyticus 9.7% (9/93). The blaZ gene was detected in 19 (20.4%), but only 16 (17.2%) isolates were resistant to penicillin; the mecA was detected in 6 (6.5%) isolates but only 4 (4.3) were resistant to cefoxitin. The 6 mecA-positive isolates showed oxacillin MICs ≥ 0.5 μg/ml. Discussion: CoNS are important minor mastitis pathogens and can be the cause of substantial economic losses. The presence of methicillin resistant isolates emphasizes the importance of identification of CoNS when an intramammary infection is present because of the potential risk of lateral transfer of resistant genes among staphylococcal species.

Identification of Variable Traits among the Methicillin Resistant and Sensitive Coagulase Negative Staphylococci in Milk Samples from Mastitic Cows in India

“…CoNS were earlier considered as the minor group of bacteria with less pathogenicity, as they were only reported in sub-clinical mastitis cases and hence, less attention was paid toward them (Pyörälä and Taponen, 2009). However, reports of clinical mastitis infection caused by various CoNS species have now surfaced largely and they have emerged as an important pathogen (Pyörälä and Taponen, 2009; Preethirani et al, 2015; Srednik et al, 2015). …”

“…However, methicillin resistant Staphylococcus aureus (MRSA) have been more widely studied and well characterized in comparison to MRS especially in India (Monecke et al, 2007; Fessler et al, 2010; Türkyilmaz et al, 2010). Increased drug exposure and use of antibiotics in animal diseases also poses a hazard to human health whose impact and effect is still not well characterized but may result in emergence of antibiotic resistant strains making the surveillance of antibiotic susceptibility very crucial (Pyörälä and Taponen, 2009; Fessler et al, 2010; Preethirani et al, 2015; Srednik et al, 2015). Another, concern associated with CoNS is that they may also act as reservoirs of antimicrobial resistance genes (Becker et al, 2014), and can transfer the resistance gene into the S. aureus genome leading to the development of new and multidrug resistant strains (Otto, 2012; Vitali et al, 2014).…”

β-lactam resistance in coagulase-negative Staphylococcus isolated from subclinical goat mastites

“…It is also worth highlighting that the low sensitivity of the phenotypic methods used in the present study may be due to the non-expression of the blaZ gene, as pointed out by Srednik et al (2015).…”

“…It was observed that the most penicillin-resistant isolates harbored the blaZ gene and produced β-lactamase, suggesting that the enzymatic inactivation of β-lactam antimicrobials is the most predominant resistance mechanism expressed by the assessed CoNS. As shown in previous studies, staphylococci are key reservoirs of β-lactam resistance markers, which are normally present in mobile DNA, such as conjugative plasmids and transposons, contributing to the transferability of these antimicrobial resistance genes between different species or genera, which is extremely important to human and veterinary medicine (Srednik et al, 2015;Haubert et al, 2017;Nobrega et al, 2018).…”

“…The presence of the blaZ gene in CoNS causing mastitis had already been observed at rates ranging from 6 to 66.6% (Srednik et al, 2015;Klimiene et al, 2016;Haubert et al, 2017;Nobrega et al, 2018;Cantekin et al, 2019). In the present study, the frequency of detection of the blaZ gene was high (91%).…”