Abstract
This study compares the characteristics of Staphylococcus epidermidis (SE) and Staphylococcus haemolyticus (SH) isolates from epidemiologically unrelated infections in humans (Hu) (28 SE-Hu; 8 SH-Hu) and companion animals (CpA) (12 SE-CpA; 13 SH-CpA). All isolates underwent antimicrobial susceptibility testing, multilocus sequence typing and DNA microarray profiling to detect antimicrobial resistance and SCCmec-associated genes. All methicillin-resistant (MR) isolates (33/40 SE, 20/21 SH) underwent dru and mecA allele typing. Isolates were predominantly assigned to sequence types (STs) within a single clonal complex (CC2, SE, 84.8%; CC1, SH, 95.2%). SCCmec IV predominated among MRSE with ST2-MRSE-IVc common to both Hu (40.9%) and CpA (54.5%). Identical mecA alleles and nontypeable dru types (dts) were identified in one ST2-MRSE-IVc Hu and CpA isolate, however, all mecA alleles and 2/4 dts detected among 18 ST2-MRSE-IVc isolates were closely related, sharing >96.5% DNA sequence homology. Although only one ST-SCCmec type combination (ST1 with a non-typeable [NT] SCCmec NT9 [class C mec and ccrB4]) was common to four MRSH-Hu and one MRSH-CpA, all MRSH isolates were closely related based on similar STs, SCCmec genes (V/VT or components thereof), mecA alleles and dts. Overall, 39.6% of MR isolates harbored NT SCCmec elements, and ACME was more common amongst MRSE and CpA isolates. Multidrug resistance (MDR) was detected among 96.7% of isolates but they differed in the prevalence of specific macrolide, aminoglycoside and trimethoprim resistance genes amongst SE and SH isolates. Ciprofloxacin, rifampicin, chloramphenicol [fexA, cat-pC221], tetracycline [tet(K)], aminoglycosides [aadD, aphA3] and fusidic acid [fusB] resistance was significantly more common amongst CpA isolates. SE and SH isolates causing infections in Hu and CpA hosts belong predominantly to STs within a single lineage, harboring similar but variable SCCmec genes, mecA alleles and dts. Host and staphylococcal species-specific characteristics were identified in relation to antimicrobial resistance genes and phenotypes, SCCmec and ACME.
Highlights
Two clinically relevant coagulase-negative staphylococcal (CoNS) species, Staphylococcus epidermidis and Staphylococcus haemolyticus, are among the leading causes of nosocomial infections in humans, in neonates, immunocompromised patients and patients with indwelling and implanted devices [1, 2]
Several studies have indicated that a great diversity of SCC harboring the MR gene mec (SCCmec) and arginine catabolic mobile element (ACME)-arc associated genes exist among CoNS, and that particular CoNS species may be a reservoir for specific SCCmec elements or genes [13]
ST2 was common to both MRSE-Hu andCpA isolates, and this was the predominant sequence types (STs) identified amongst both groups (9/22, 40.9% MRSE-Hu and 9/11, 81.8% MRSE-companion animals (CpA)) (Table 1)
Summary
Two clinically relevant coagulase-negative staphylococcal (CoNS) species, Staphylococcus epidermidis and Staphylococcus haemolyticus, are among the leading causes of nosocomial infections in humans, in neonates, immunocompromised patients and patients with indwelling and implanted devices [1, 2]. Several studies have indicated that a great diversity of SCCmec and ACME-arc associated genes exist among CoNS, and that particular CoNS species may be a reservoir for specific SCCmec elements or genes [13]. Such CoNS often carry non-typeable SCCmec elements with novel cassette chromosome recombinase (ccr) and mec gene complexes, or combinations of these genes, yet unidentified in methicillin resistant S. aureus (MRSA). The direct-repeat unit (dru) region within the SCCmec element has proved useful for tracking the epidemiological spread of different SCCmec elements as well as for further discriminating MRSA [16]
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