Short communication: Detection of antibiotic resistance, mecA, and virulence genes in coagulase-negative Staphylococcus spp. from buffalo milk and the milking environment

Abstract

The aim of this study was to determinate whether coagulase-negative staphylococci (CNS) from buffalo milk or the milking environment possess virulence factors that are associated with intramammary infections or antimicrobial resistance. Milk samples (n = 320) from 80 lactating buffalo were evaluated for clinical and subclinical mastitis by physical examination, the strip cup test, California Mastitis Test (CMT), and somatic cell count (SCC) over a 4-mo period. In addition, swabs were obtained from the hands of consenting milkers (16), liners (64), and from the mouths (15) and nostrils (15) of buffalo calves. No clinical cases of mastitis were observed; however, CMT together with SCC results indicated that 8 animals had subclinical mastitis. Eighty-four CNS isolates were identified by MALDI-TOF MS and cydB real-time PCR (qPCR) and then evaluated by qPCR for presence of the eta, etb, sea, sec, cna, seb, sei, seq, sem, seg, see, and tst toxin genes, adhesion-and biofilm-associated genes (eno, ebps, fib, fnbA, coa), and the methicillin resistance gene (mecA). Resistance to antibiotics commonly used for mastitis treatment in Brazil was determined using the Kirby-Bauer test. Two strains were positive for the see and eta toxin genes; and mecA (1), eno (27), ebps (10), fnbA (10), and coa (5) genes were also detected. A notable number of isolates were resistant to erythromycin (30), penicillin (26), and cotrimoxazole (18); importantly, 10 vancomycin-resistant isolates were also detected. A smaller number of isolates were resistant to rifampicin (8), oxacillin (7), clindamycin (5), cefepime (4), tetracycline (3), ciprofloxacin (2), and chloramphenicol (1), and none were resistant to gentamicin or ciprofloxacin. Isolates with resistance to 2 (13 isolates), 3 (3), 4 (3), 5 (1), and 6 (1) antibiotics were detected. Taken together, our findings suggest that CNS isolates may not be a significant cause of clinical or even subclinical mastitis in buffaloes, but they may be a reservoir of virulence and antibiotic resistance genes.

Virulence Factors in Staphylococcus Associated with Small Ruminant Mastitis: Biofilm Production and Antimicrobial Resistance Genes

“…In the CNS group, S. caprae was the most found species and was isolated only from goat's milk samples. It is a commensal organism that prevails in the skin of the goat udder [19] This species is most commonly found in cases of goat mastitis [37,[45][46][47], but it was also isolated from sheep [5,48], buffalo [17], and cow's milk [49].…”

“…This enzyme, encoded by the coa gene, is commonly used to distinguish coagulase positive staphylococci (CPS), namely S. aureus, S. intermedius, and S. pseudintermedius, from CNS species [16]. Nevertheless, this gene has been found also in species known as CNS such as S. epidermidis, S. chromogenes, and S. hominis [17]. The coa gene has also recently been associated with biofilm production [18].…”

Virulence Characteristics of mecA-Positive Multidrug-Resistant Clinical Coagulase-Negative Staphylococci

“…Whereas there have been many studies regarding virulence characteristics of methicillin-resistant S. aureus, limited studies have been reported on CoNS [19,20]. Therefore, investigation of phenotypic and genotypic virulence characteristics in clinical CoNS isolates is of great value for understanding their roles in pathogenesis.…”

Safety Issues Regarding the Detection of Antibiotics Residues, Microbial Indicators and Somatic Cell Counts in Ewes’ and Goats’ Milk Reared in Two Different Farming Systems

“…The result of such an infection is mastitis characterized by increased SCC, reduction of milk yield, compromised lamb development, spontaneous abortions, and high mortality [74]. They form biofilms which act as barriers to the penetration of antibiotics and behave as a hazard to the action of phagocytes [63,69,[75][76][77]. Not all CNS infections lead to inflammation and the outcome depends on the condition of the skin and of the mucous membranes as barriers to the infiltration of the bacteria.…”