First Staphylococcal Cassette Chromosome mec Containing a mecB -Carrying Gene Complex Independent of Transposon Tn 6045 in a Macrococcus caseolyticus Isolate from a Canine Infection

Abstract

A methicillin-resistant mecB-positive Macrococcus caseolyticus (strain KM45013) was isolated from the nares of a dog with rhinitis. It contained a novel 39-kb transposon-defective complete mecB-carrying staphylococcal cassette chromosome mec element (SCCmec KM45013 ). SCCmec KM45013 contained 49 coding sequences (CDSs), was integrated at the 3= end of the chromosomal orfX gene, and was delimited at both ends by imperfect direct repeats functioning as integration site sequences (ISSs). SCCmec KM45013 presented two discontinuous regions of homology (SCCmec coverage of 35%) to the chromosomal and transposon Tn6045-associated SCCmec-like element of M. caseolyticus JCSC7096: (i) the mec gene complex (98.8% identity) and (ii) the ccr-carrying segment (91.8% identity). The mec gene complex, located at the right junction of the cassette, also carried the ␤-lactamase gene blaZm (mecRm-mecIm-mecB-blaZm). SCCmec KM45013 contained two cassette chromosome recombinase genes, ccrAm2 and ccrBm2, which shared 94.3% and 96.6% DNA identity with those of the SCCmec-like element of JCSC7096 but shared less than 52% DNA identity with the staphylococcal ccrAB and ccrC genes. Three distinct extrachromosomal circularized elements (the entire SCCmec KM45013 , ⌿SCCmec KM45013 lacking the ccr genes, and SCC KM45013 lacking mecB) flanked by one ISS copy, as well as the chromosomal regions remaining after excision, were detected. An unconventional circularized structure carrying the mecB gene complex was associated with two extensive direct repeat regions, which enclosed two open reading frames (ORFs) (ORF46 and ORF51) flanking the chromosomal mecB-carrying gene complex. This study revealed M. caseolyticus as a potential diseaseassociated bacterium in dogs and also unveiled an SCCmec element carrying mecB not associated with Tn6045 in the genus Macrococcus.T he genus Macrococcus is composed of seven species of Grampositive bacteria closely related to staphylococci, including Macrococcus caseolyticus (formerly identified as Staphylococcus caseolyticus) (1). Unlike staphylococci, macrococci do not usually cause human or animal diseases and are typically isolated from animal skin and food products, such as milk and meat (1, 2). The only association of M. caseolyticus with an infection was observed in abscesses from slaughtered lambs in 1992 (3). Even though M. caseolyticus is not primarily targeted by antibiotic treatment as an infectious agent, a few strains have acquired antibiotic resistance mechanisms identical or similar to those found in staphylococci, such as cfr-mediated multidrug resistance (4) and mecB-mediated methicillin resistance (5), respectively.In staphylococci, methicillin resistance is caused by the synthesis of a modified penicillin binding protein (PBP2a) with low affinity to virtually all ␤-lactams. This protein is encoded by either the mecA or the mecC gene (6, 7), whose expression is often regulated by the presence of MecR1 (sensor/signal transducer mecR1 gene) and MecI (mec transcription repressor mecI gene). These gene...

Complete Genome Sequence of the Type Strain of Macrococcus canis

“…M. canis also has the ability to acquire antibiotic resistance genes, including the methicillin resistance gene mecB . mecB has been shown to be present on the staphylococcal cassette chromosome mec element (SCC mec ) in strain KM45013 (SCC mec KM45013 ) ( 3 ). At the time of isolation, strain KM45013 was identified as M. caseolyticus and was recognized as a new Macrococcus species in early 2017.…”

“…In addition to the methicillin resistance gene mecB conferring resistance to β-lactam antibiotics ( 3 ), the genome of M. canis strain KM45013 T contains genes for a bicomponent γ-hemolysin ( hlgB at complement positions 98969 to 99922 and hlgC at complement positions 99935 to 100879 in GenBank accession no. CP021059) explaining the hemolytic phenotype observed on sheep blood agar plates.…”

Genome analysis of methicillin resistance in Macrococcus caseolyticus from dairy cattle in England and Wales

“…However, a role for Macrococcus , in particular Macrococcus caseolyticus and Macrococcus canis in veterinary infections has become increasingly recognised. M. caseolyticus having been isolated from ovine abscesses [ 2 ], bovine mastitis [ 3 ], canine dermatitis [ 4 ], canine rhinitis [ 5 ] and canine otitis [ 3 ] with M. canis being linked to a range of canine infections [ 4 ]. Methicillin resistance has been described in both M. caseolyticus and M. canis .…”

Description and Comparative Genomics of Macrococcus caseolyticus subsp. hominis subsp. nov., Macrococcus goetzii sp. nov., Macrococcus epidermidis sp. nov., and Macrococcus bohemicus sp. nov., Novel Macrococci From Human Clinical Material With Virulence Potential and Suspected Uptake of Foreign DNA by Natural Transformation

“…Although none of the species of the genus Macrococcus are thought to be human pathogens, there are reports of macrococci associated with animal infections (Gómez-Sanz et al, 2015 ; Hansen et al, 2015 ; Cotting et al, 2017 ). These findings suggest the possible pathogenicity of macrococci.…”

“…These findings suggest the possible pathogenicity of macrococci. Furthermore, the identification of methicillin-resistant strains of macrococci carrying the staphylococcal cassette chromosome (SCC) in their genome reveals a potential broad host-range dissemination of this resistance element between the genera Macrococcus and Staphylococcus (Baba et al, 2009 ; Rubin and Chirino-Trejo, 2010 ; Tsubakishita et al, 2010 ; Cicconi-Hogan et al, 2014 ; Gómez-Sanz et al, 2015 ; Micheel et al, 2015 ).…”