Community-acquired methicillin-resistant <em>Staphylococcus aureus</em> from ST1 lineage harboring a new SCC<em>mec</em> IV subtype (SCC<em>mec</em> IVm) containing the <em>tetK</em> gene

Abstract

A pivotal event in the evolutionary path of methicillin-resistant Staphylococcus aureus (MRSA) is the acquisition of the staphylococcal cassette chromosome mec (SCCmec) element carrying the mecA gene, the determinant of methicillin resistance. Community-acquired (CA) MRSA is commonly associated with skin/soft tissue infections, and doxycycline is one of the drug choices for this purpose. Doxycycline resistance is associated with the acquisition of the tetK gene carried by the S. aureus plasmid pT181, which may also be integrated into SCCmec III and V. The aim of this study was to describe a novel SCCmec IV subtype (IVm) carrying tetK and reveal the genetic context of this element. The SCCmec sequence was obtained by whole-genome sequencing of the MRSA strain 2288 (ST1 CA-MRSA) and genomic analysis performed using different bioinformatics tools. A copy of pT181 was found to be integrated in the new SCCmec IVm of the strain 2288. The SCCmec IVm has high nucleotide identity (99%) with SCCmec IVa of the strain MW2, except for the J3 region, where the pT181 – carrying tetK gene – is inserted. Inverted repeats (IRs) flanking pT181 were found in this region, suggesting the occurrence of recombination events. The strain 2288 (spa type t125) shares most of the virulence attributes with MW2 (spa type t128), which is recognized in the past as a cause of severe infections in children in USA. The pattern of branching in the phylogenetic tree depicts a recent common ancestor shared by the 2228 strain and other MRSA from USA, including ERS410852, TCH70, CIG1835, CO-41, MW2, and USA400-0051, but none of them carried pT181. This study also showed that the tetK carried by SCCmec IVm is functional, determining resistance to doxycycline and tetracycline. The potential dissemination of the tetK and mecA genes in the same genetic event by the acquisition of this new SCCmec subtype is of concern for community infections.

Antimicrobial Resistance in Methicillin-Resistant Staphylococcus aureus to Newer Antimicrobial Agents

“…Minocycline susceptibility is not affected by tet(K), even after incubation in subinhibitory concentrations of the drug (79). The tet(K) gene, which is plasmid-borne, has been shown to spread through a USA400 MRSA strain (81). The tet(M) gene is a chromosomal gene that enhances ribosomal protection by encoding elongation factor-like proteins.…”

Reductive evolution of virulence repertoire to drive the divergence between community- and hospital-associated methicillin-resistant Staphylococcus aureus of the ST1 lineage

“…This study highlights the combined importance of MGEs in the establishment of virulence (bacteriophages and genomic island SAPImw2) and susceptibility patterns (resistance-associated plasmid pMW2-like). In fact, the presence of a virulence gene in S. aureus is often associated with the acquisition of an associated mobile genetic element (MGE) [ 34 ]. However, it is striking that ST1-SCC mec IV, whether or not they were carrying ear, lukSF-PV, sea, selK, selq , or splDE always harbored the associated MGE in their genomes, which was often associated with a high nucleotide identity.…”

High prevalence of t895 and t9364 spa types of methicillin-resistant Staphylococcus aureus in a tertiary-care hospital in Mexico: different lineages of clonal complex 5

“…In contrast, tetracycline resistance was reported in 6% of MSSA strains and 17% of MRSA strains collected globally between 1997 and 2016 [ 38 ]. Resistance to this antibiotic in S. aureus is encoded by the tet K and tet M genes [ 39 ], mainly detected in SCC mec III, IV, and V MRSA strains [ 9 , 40 , 41 ]. The majority of MRSA strains in our study had SCC mec type II, and this might explain, in part, the absence of tetracycline resistance.…”