Detection and characterization of methicillin-resistant and susceptible coagulase-negative staphylococci in milk from cows with clinical mastitis in Tunisia.

Abstract

Coagulase-negative staphylococci containing a diversity of antimicrobial resistance genes are frequently detected in milk of mastitis cows. This fact emphasizes the importance of identifying CNS when an intramammary infection is present because of the potential risk of lateral transfer of resistant genes among staphylococcal species and other pathogenic bacteria.

Review of Clinically and Epidemiologically Relevant Coagulase-Negative Staphylococci in Africa

“…samples, Klibi et al, using SCCmec typing, discovered methicillin-resistant S. epidermidis possessed SCCmec type-Iva. 41 The isolates also possessed the recombinase genes ccr A2/B2-class B mec gene complex determined by PCR of the ccr recombinases (1-5). Also, Ehlers et al found that SCCmec type IV was the most predominant with 31% of S. epidermidis isolates belonging to that class.…”

“…In comparison to MR-CoNS, the MS-CoNS isolates showed lower levels of resistance to antibiotics. 41 This was expected, as methicillin resistance is known to cause cross resistance to other antibiotics. 103 Dhaouadi et al however, reported the first occurrence of mecC gene in CoNS (S. sciuri) in Africa (having been already reported in animals in Europe), 104 obtained from cows and manure, in a study which also found the ARGs tet(K), mecA, msr(A), blaZ, erm(A), and erm(B) simultaneously from cow (milk), manure, and human (nares) sources, which may be suggestive of an exchange of ARGs among these sources.…”

“…19 The possession for example of virulence factors, such as Panton-Valentine leukocidin or toxic shock syndrome toxin 1 and enterotoxins could be associated with increased pathogenicity of CoNS. 41 The CoNS do not possess as many virulence factors as S. aureus, reflected in the different spectra of diseases they respectively cause. 41 The detection of phenol-soluble modulins in S. epidermidis was found to contribute to endemicity, invasiveness, and persistence in hospital environments 42 and CoNS sepsis, especially when methicillin resistant.…”

“…41 The CoNS do not possess as many virulence factors as S. aureus, reflected in the different spectra of diseases they respectively cause. 41 The detection of phenol-soluble modulins in S. epidermidis was found to contribute to endemicity, invasiveness, and persistence in hospital environments 42 and CoNS sepsis, especially when methicillin resistant. 43 In a study investigating factors that contribute to the pathogenicity of CoNS from clinical sources in comparison with community CoNS strains, it was found that 25% of strains produced toxins that induced hemolysis in 50% of human red blood cells within 1 hour, with some 3% showing lytic activity on human polymorphonuclear cells after 30 minutes.…”

“…Klibi et al while characterizing MR-CoNS and methicillinsusceptible coagulase-negative staphylococci (MSCoNS) from cows with clinical mastitis, found that 70% of MR-CoNS carried the mecA gene, but all MR-CoNS isolates lacked the mecC gene; however, the resistance genes tet(K), dfr(A), Inu(B), erm(C), erm(B), erm(T), mph(C), or msr(A) were detected. 41 The phenotypic observance of methicillin resistance without the genotypic detection of mecA or other known methicillin resistance mechanisms may be due to the emergence of a new methicillinase, overproduction of b-lactamases, or the changes in binding affinity of penicillin-binding proteins. 101,102 It is thus important to investigate alternative methicillin resistance mechanisms.…”