Methicillin and aminoglycoside resistance in Staphylococcus aureus isolates from bovine mastitis and sequence analysis of their mecA genes

Abstract

Although methicillin-resistant Staphylococcus aureus (MRSA) were generally isolated from human beings; these agents were recently isolated from various animal species. It has been shown that MRSA isolates are not only resistant to beta-lactam antibiotics, but can also be resistant to the other commonly used antibiotics. In this study, 18 phenotypic methicillin resistant S. aureus isolates from bovine mastitis cases were analyzed by PCR for the presence of mecA gene encoding methicillin resistance and aac (6′)/aph(2″), aph(3′)-IIIa and ant(4′)-Ia genes encoding aminoglycoside resistance. Out of 18 S. aureus isolates (oxacillin MICs, ≥4 μg/ml), 3 were positive for mecA gene. Only one from 3 mecA positive isolates was positive for genes encoding aminoglycoside-modifying enzymes and this isolate carried aac(6′)/aph(2″) in combination with aph(3′)-IIIa gene. The aph(3′)-IIIa gene was detected in 3 isolates. These three isolates carrying the aminoglycoside-modifying enzyme genes were resistant to gentamicin, kanamycin and neomycin. The mecA gene of 3 MRSA isolates was sequenced. All three mecA genes of these isolates were identical to that found in human MRSA strains, except a one-base substitution at nucleotide position 757. From the data presented in this study, it can be concluded that MRSA isolated from bovine mastitis may be originated from human beings, but further studies are needed to investigate the possibility of zoonotic transfer of MRSA.

Identification and Characterisation of Methicillin-Resistant Staphylococcus aureus Isolated from Bovine Mastitis

“…The same results were also stated for the presence of mecA genes from bovine mastitis (Turutoglu et al, 2009 andVishnupuriya et al, 2014) dogs, cats (Malik et al, 2006) and horses (Schnellmann et al, 2006). Based on the results from the present study and the other studies (vanDuijkeren et al, 2004 andMalik et al, 2006), it can be construed that these isolates might have originally come from humans, considering that the methicillin resistance among human Staphylococcus isolates is common.…”

“…The possible reasons for this type of discrepancy are that the isolates appeared to show poor expression of mecA genes or production of methicillinase (alteration of PBP subtypes) or seem to overproducing β-lactamase. The phenotypic expression of resistance could vary due to growth conditions which are also involved in the expression of methicillin resistance (Zmantar et al, 2008;Turutoglu et al, 2009 andTurkylmaz et al, 2010).…”

Cezayir’de İnek Mastitislerinden İzole Edilen Stafilokokların Antibiyotik Direncinin Fenotipik ve Moleküler Yöntemlerle Belirlenmesi

“…On the contrary, de Oliveira et al [45] found that overall level of resistance was generally low to all antimicrobial agents that are currently commercially available to treat bovine mastitis. [18,46,47] . In this study, 100% of isolates of S. aureus and CNS were methicillin-resistant.…”

“…In literature, a few studies have reported the occurrence of MRSA from bovine mastitis and proportion of resisting isolates was low [18,46,47] . In this study, 100% of isolates of S. aureus and CNS were methicillin-resistant.…”

“…In this study, 100% of isolates of S. aureus and CNS were methicillin-resistant. The isolates appeared to demonstrate privileged expression of mecA genes or production of methicillinase or appear to overproducing beta-lactamase [18,47] . The phenotypic expression of resistance could vary due to growth conditions or might be limitations in detection in microbiological methods [48] .…”