Tetracycline resistance phenotypes and genotypes of coagulase-negative staphylococcal isolates from bubaline mastitis in Egypt

Abstract

Aim::This study was devoted to elucidate the tetracycline resistance of coagulase-negative staphylococci (CNS) derived from normal and subclinical mastitic (SCM) buffaloes’ milk in Egypt.Materials and Methods: ::A total of 81 milk samples from 46 normal buffalo milk samples and 35 SCM buffalo milk samples at private dairy farms of Egypt were used in this study. CNS were identified using phenotypic and molecular methods (polymerase chain reaction [PCR]). CNS isolates were tested for tetracycline resistance using routine methods and multiplex PCR targeting tetracycline (tet) resistance genes followed by sequencing of positive PCR products and phylogenetic analysis.Results::Isolation and identification of 28 (34.5%) CNS from normal and SCM buffaloes’ milk, namely, Staphylococcus intermedius (39.2%), Staphylococcus xylosus (25.0%), Staphylococcus epidermidis (10.7%), Staphylococcus hominis (10.7%), and 3.5% to each of Staphylococcus sciuri, Staphylococcus hyicus, Staphylococcus lugdunensis, and Staphylococcus simulans. Using nested PCR, all the 28 CNS isolates revealed positive for 16srRNA gene specific for genus staphylococci and negative for thermonuclease (nuc) gene specific for Staphylococcus aureus species. The presence of tetracycline resistance-encoding genes (tetK, tetL, tetM, and tetO) was detected by multiplex PCR. All isolates were negative for tetL, M, and O genes while 14 (50%) CNS isolates were positive for tetK gene, namely, S. lugdunensis (100%), S. hominis (100%), S. epidermidis (66.6%), S. intermedius (45.4%), and S. xylosus (42.8%). Nucleotide sequencing of tetK gene followed by phylogenetic analysis showed the high homology between our CNS isolates genes of tetracycline resistance with S. aureus isolates including Egyptian ones. This proves the transfer of the tetracycline resistance encoding genes between coagulase-negative and coagulase positive Staphylococcus spp.Conclusion::CNS isolates have distinguishingly high resistance to tetracycline. Abundant tetracycline usage for mastitis treatment leads to the spread of genetic resistance mechanisms inside CNS strains and among all Staphylococcus spp. Consequently, tetracycline is not effective anymore.

Species Distribution, Antimicrobial Resistance, and Enterotoxigenicity of Non-aureus Staphylococci in Retail Chicken Meat

“…TET resistance is usually conferred by the acquisition of tet (M), tet (O), and tet (S), which encode ribosomal protection proteins, or tet (K) and tet (L), which encode efflux pumps [ 34 ]. Similar to previous publications [ 26 , 46 ], all of the TET-resistant CoNS including S. saprophyticus , S. sciuri , S. simulans , and S. lentus possessed tet (K). In contrast to the TET-resistant CoNS, all the S. chromogenes and S .…”

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

“…Regarding tetracycline, most S. aureus isolates (32/35) were susceptible, while nonsusceptible isolates belonged to the following CNS species: S. caprae (4), S. haemolyticus (3), S. lentus (2), S. capitis (1), S. hominis (2), S. rostri (1), and S. warneri (1). Tetracycline has been widely used in veterinary medicine, and other studies have reported a higher percentage of resistant isolates: 42.8% [82] and 28.9% [45]. On the contrary, our results show a relatively low percentage of non-susceptible isolates (12.4%).…”

Prevalence and Molecular Determinants of Antimicrobial Resistance in Clinical Isolates of Staphylococcus haemolyticus from India

“…Although performed on veterinary specimens, El-Razik et al found 50% of CoNS to have the tetK gene. 21 Moreover, 12 isolates that were positive for the tetK gene were sensitive to tetracycline. Duran et al too reported 15 staphylococcal isolates to be positive for tetK and tetM genes, but these isolates were phenotypically sensitive.…”