Widespread distribution of disinfectant resistance genes among staphylococci of bovine and caprine origin in Norway

We demonstrate here a widespread distribution of genes mediating efflux-based resistance to quaternary ammonium compounds (QACs) in staphylococci from unpasteurized milk from 127 dairy cattle herds and 70 dairy goat herds. QAC resistance genes were identified in 21% of the cattle herds (qacA/B, smr, qacG, and qacJ) and in 10% of the goat herds (qacA/B and smr). Further examination of 42 QAC-resistant bovine and caprine isolates revealed the following genes: qacA/B (12 isolates) was present in four different species of coagulase-negative staphylococci (CoNS), smr (27 isolates) was detected in eight different CoNS species and in Staphylococcus aureus on a previously reported plasmid (pNVH99), qacG (two isolates) was detected on two plasmids (pST94-like) in Staphylococcus cohnii and Staphylococcus warneri, and qacJ (two isolates) was found in Staphylococcus hominis and Staphylococcus delphini on a plasmid (pNVH01) previously found in equine staphylococci. Isolation of indistinguishable pulsed-field gel electrophoresis (PFGE) CoNS types from tank milk and mammary quarter milk samples in a dairy cattle herd suggested that these QAC-resistant staphylococci were of intramammary origin. Indistinguishable or closely related PFGE types of bovine QAC-resistant CoNS were observed in different herds. One particular bovine S. warneri PFGE type was isolated repeatedly from samples collected during a 30-month period in a herd, showing long-term persistence. In conclusion, it seems that the widespread distribution of staphylococci carrying QAC resistance genes in Norwegian dairy cattle and goat herds is the result of both the intra- and interspecies spread of QAC resistance plasmids and the clonal spread of QAC-resistant strains.     

Disinfectant and antibiotic resistance of lactic acid bacteria isolated from the food industry

Quaternary ammonium compounds (QACs) are widely used as disinfectant in medical and food environments. There is a growing concern about the increasing incidence of disinfectant-resistant microorganisms from food. Disinfectant-resistant lactic acid bacteria (LAB) may survive disinfection and cause spoilage problems. Moreover, resistant LAB may potentially act as a reservoir for resistance genes. A total number of 320 LAB from food industry and meat were screened for resistance to the QAC benzalkonium chloride (BC). Out of 320 strains, five strains (1.5%) were considered to be resistant and 56 (17.5%) were tolerant to BC. The resistant strains were isolated from food processing equipment after disinfection. The resistant, tolerant, and some sensitive control bacteria were examined for susceptibility to 18 different antibiotics, disinfectants, and dyes using disc agar diffusion test and microdilution method. Little systematic cross-resistance between BC and any of the antimicrobial agents tested were detected except for gentamycin and chlorhexidine. A BC-tolerant strain was much easier to adapt to higher levels of BC as compared to a BC-sensitive strain. No known gram-positive QAC resistance genes (qacA/B, qacC, qacG, and qacH) were detected in the BC-resistant strains. Identification to species level of the BC-resistant isolates was carried out by comparative analysis of 16S-rDNA sequencing. In conclusion, resistance to BC is not frequent in LAB isolated from food and food environments. Resistance may occur after exposure to BC. The BC resistant isolates showed no cross-resistance with other antimicrobial compounds, except for gentamycin and chlorhexidine. Nevertheless, BC-resistant LAB may be isolated after disinfection and may contribute to the dissemination of resistance.     

Analysis on distribution and genomic diversity of high-level antiseptic resistance genes qacA and qacB in human clinical isolates of Staphylococcus aureus

High-level antiseptic resistance of Staphylococcus aureus is mediated by multidrug efflux pumps encoded by qacA and qacB genes. We investigated distribution and genomic diversity of these antiseptic resistance genes in a total of 522 clinical strains of S. aureus isolated recently in a Japanese hospital. The qacA/B gene was detected in 32.6% of methicillin-resistant S. aureus (MRSA) and 7.5% of methicillin-susceptible S. aureus (MSSA), whereas the low-level resistance gene smr, which was examined simultaneously, was detected at lower frequencies in both MRSA (3.3%) and MSSA (5.9%). Epidemiologic typing of S. aureus isolates suggested that higher prevalence of qacA/B in MRSA may be due to spread of a single predominant MRSA strain carrying qacA/B in the hospital. Restriction fragment length polymorphism (RFLP) analysis indicated higher prevalence of the qacB-type gene (59.3%) than the qacA-type gene (40.7%) among the qacA/B genes detected. Nucleotide sequencing analysis revealed the presence of two genetic variants in qacA (V1 and V2) and four variants in qacB (V1-V4) that differ from the qacA prototype in pSK1 by 1-5 nucleotides and 7-9 nucleotides, respectively. Although most strains with qacA-V1, qacA-V2, qacB-V3, and qacB-V4 showed high-level resistance to ethidium bromide (EB)(MIC > 100 microg/ml), all of the S. aureus isolates carrying qacB-V1 and qacB-V2 showed lower MICs of EB and some monovalent cationic antiseptic substances. By analysis of the genomic organization of the qacA/B downstream region, divergent forms of this region rearranged with an insertion of IS256 or IS257 were found primarily for qacB. The downstream region of qacA-V1 was suggested to be an evolutionary origin for other divergent forms. These findings indicated that both qacA and qacB are prevalent in recent clinical isolates, especially in MRSA, and these genes consist of variable genetic variants that may be responsible for different resistance levels against antiseptic substances.     

First detection of the antiseptic resistance gene qacA/B in Enterococcus faecalis

Resistance to disinfectants is well investigated in staphylococci and pseudomonads but nearly unexplored in bacteria of the genus Enterococcus, despite their rising significance as nosocomial pathogens. In this study, Enterococcus faecalis (n=585) from blood (n=42) and stool (n=109) of hospitalized humans, from faeces of farm animals (n=226), and from food (milk and dairy products, n=96; meat and meat products, n=112) were screened for the presence of qac-genes (qacA, qacB, qacC, smr [qacC+qacD], qacEΔ1, qacG, qacH, qacJ) via PCR. The isolates' susceptibility to a quaternary ammonium compound (didecyldimethylammoniumchloride, DDAC) and antibiotics was assessed by microdilution. Four E. faecalis strains were positive for qac-genes: qacA/B was found in one isolate from cattle and one isolate from human blood; smr (qacC+qacD) was detected in one isolate from human stool and in one isolate from cheese ("Camembert"). The sequences of the qacA/B-amplicons differed in two basepairs. DDAC had an elevated minimum inhibitory concentration (MIC) of 2.45-3.5 mg/L in one qacA/B-positive strain from human blood, whereas the other qac-gene carriers had wild-type MIC-values for DDAC (1.05 mg/L). This is the first detection of qacA/B in the genus Enterococcus.     

Persistence of multidrug-resistant Staphylococcus haemolyticus in an animal veterinary teaching hospital clinic

In the recent decades, coagulase-negative staphylococci (CNS) have emerged as important nosocomial pathogens with the ability to develop resistance to antibiotics and disinfectants. Multidrug-resistant CNS are currently a common finding in hospital settings and hospitalized patients. Little is known about the occurrence and persistence of multidrug-resistant CNS in animal clinics. A survey of the environmental bacterial flora in a small animal clinic showed a predominance of bacterial species commonly isolated from skin and feces of warm-blooded animals and the environment. At samplings separated by 3 years, multidrug-resistant Staphylococcus haemolyticus was isolated from the floor of four separate animal cages and from a cat's postoperative wound infection. Pulsed-field electrophoresis, multilocus enzyme typing, susceptibility testing, and genotypic characterization suggested that the multidrug-resistant S. haemolyticus isolates belonged to an epidemiological clone. All isolates harbored a chromosomal copy of the mecA gene, a 45-kb plasmid harboring the blaZ and qacA/B determinants, and all except one isolate carried multiple plasmids in the size range 1-22 kb, of which those <5 kb encoded resistance to tetracycline (tetK), macrolides (ermB), and chloramphenicol (cat). One isolate carried a chromosomal copy of the bifunctional gene aacA-aphD conferring resistance to gentamicin. The isolate that was deficient of small plasmids had reverted to a macrolide and chloramphenicol-susceptible phenotype, but had retained its tetracycline resistance due to IS257-mediated integration of the tetK plasmid into the mec region of the chromosome. This finding illustrates bacterial intracellular mobility of resistance genes in natural environments, and highlights the role of insertion sequences in the evolution of multidrug resistance islands on the bacterial chromosome.     

Comparison of genes involved in penicillin resistance in staphylococci of bovine origin

Ten penicillin-resistant and -susceptible staphylococci, isolated from bovine mastitis milk, were studied for the presence of genes that are, or may be, involved in resistance against penicillin. The repressor (blaI), antirepressor (blaR1), and structural (blaZ) genes of the beta-lactamase-operon were found to be closely linked in all penicillin-resistant strains. The beta-lactamase gene cluster was more commonly located on chromosomal rather than plasmid DNA in the strains studied. The transposase (p480) gene, which has been identified in the Staphylococcus aureus beta-lactamase transposon Tn552, was found in only one single penicillin-resistant S. aureus strain. The other penicillin-resistant S. aureus isolates contained IS1181 in close location with the beta-lactamase gene cluster. In only one S. haemolyticus isolate was the beta-lactamase gene cluster found in close association with IS257. Penicillin-resistant S. aureus strains, which were additionally resistant to tetracycline, contained IS257 in close association with the tetracycline resistance gene (tetK). Sequence analysis of blaI, blaR1, and blaZ in two penicillin-resistant S. aureus strains revealed 94-96% sequence homology with bla in staphylococci of human origin. The results indicate a predominance of class I bla transposons rather than Tn3 family class II transposons in the isolates used in this study.     

Common antibiotic resistance plasmids in Staphylococcus aureus and Staphylococcus epidermidis from human and canine infections

The plasmids of a multiresistant "canine" Staphylococcus epidermidis-culture were investigated. Two small plasmids, the 4.55 kB chloramphenicol resistance (CmR-) plasmid pSC4 and the 4.45 kB tetracycline resistance (TetR-) plasmid pST 3 could be isolated. Detailed restriction maps of pSC 4 and pST 3 were constructed by double restriction endonuclease digests. The restriction maps revealed extensive structural homologies between pSC 4 from "canine" S. epidermidis and the CmR-plasmid pC 221 from "human" S. aureus as well as between pST 3 from "canine" S. epidermidis and the TetR-plasmid pT 181 from "human" S. aureus. These data suggested that an exchange of small plasmids between S. epidermidis and S. aureus might be possible.     

Plasmid-Borne smr Gene Causes Resistance to Quaternary Ammonium Compounds in Bovine Staphylococcus aureus

Resistance to quaternary ammonium compounds (QAC) in staphylococci is common in hospital environments and has been described in the food industry. Little is known about staphylococcal QAC resistance associated with animal disease, although such disinfectants are widely used in veterinary medicine. In order to investigate the occurrence of QAC resistance in staphylococci isolated from QAC-exposed animals, 32 penicillin- and tetracycline-resistant and 23 penicillin- and tetracycline-susceptible Staphylococcus aureus isolates collected from milk from cows with mastitis during a 4-year period were selected for QAC susceptibility studies and genetic characterization. The isolates originated from four different herds that used a common pasture with a joint milking parlor in the summer. During the pasture season, a teat cream containing the QAC cetyltrimethylammonium bromide had been used daily for more than 10 years for mastitis control. Three of the penicillin- and tetracycline-resistant isolates, which were recovered from three different cows during a 20-month period, were resistant to QAC. Plasmid analysis, PCR, and DNA sequencing revealed a novel plasmid of 2,239 bp containing the smr gene. The plasmid, designated pNVH99, has similarities to small, smr-containing staphylococcal plasmids previously found in human and food isolates. pNVH99 is a new member of the pC194 family of rolling-circle replication plasmids. The three QAC-resistant isolates, as well as 28 of the 29 remaining penicillin- and tetracycline-resistant isolates, were indistinguishable by pulsed-field gel electrophoresis. The study indicates that the occurrence and spread of QAC-resistant S. aureus among dairy cows may be a problem that needs further investigation.     

Intra- and inter-species mobilisation of non-conjugative plasmids in staphylococci.

The ability of Staphylococcus aureus conjugative plasmids to mobilise non-conjugative resistance plasmids from clinical isolates of S. aureus and S. epidermidis was studied. Plasmids which could not be transferred by transduction or mixed-culture transfer were transferred from phage-typable and non-typable S. aureus and from S. epidermidis. Plasmids encoding single resistance determinants were transferred by mobilisation whereas multiple-resistance plasmids were transferred as co-integrates between the conjugative and non-conjugative plasmids. This study demonstrates that mobilisation is a useful tool for the transfer and study of staphylococcal plasmids and illustrates how antibiotic resistance could be transferred between staphylococci in vivo.     

An epidemiological assessment of coagulase-negative staphylococci from an intensive care unit.

Detection of an unusual combination of four resistance markers among coagulase-negative staphylococci (CNS) isolated in the same intensive care unit led to the undertaking of an epidemiological assessment. Seventeen CNS isolates from the same unit and 38 epidemiologically unrelated Staphylococcus epidermidis isolates were typed by eight methods, including analysis of immunoblot patterns and hybridisation patterns (HP) obtained with three probes. The probes comprised plasmids carrying the genes encoding 16S rRNA (pBA2), aacA-aphD (pSF815A), and aacA-aphD with part of IS256 (pIP1307). Immunoblot patterns and HP with pIP1307 indicated that 14 of the 17 CNS isolates from the same unit resulted from the spread of an epidemic strain.     

The product of the qacC gene of Staphylococcus epidermidis CH mediates resistance to beta-lactam antibiotics in gram-positive and gram-negative bacteria

We have characterized a natural isolate of Staphylococcus epidermidis resistant to heavy metals that carries a small 2391-bp plasmid, pSepCH, encoding the qacC gene. The S. epidermidis qacC gene confers resistance to a number of beta-lactam antibiotics and to ethidium bromide in its natural host and in Escherichia coli K12 and Salmonella enterica sv. Typhimurium. This is the first communication of a small multidrug resistance (SMR) pump involved in resistance to beta-lactam antibiotics. Experiments using tolC, ompW and ompD mutant strains of S. Typhimurium demonstrated that the beta-lactam antibiotic resistance conferred by this pump does not depend on these outer membrane proteins.     

Multiple antibiotic resistance in Staphylococcus aureus and Staphylococcus epidermidis: plasmids in strains associated with nosocomial infection

The plasmid DNA profiles were compared to phenotypically-similar, antibiotic-resistant strains of Staphylococcus aureus and Staphylococcus epidermidis associated with nosocomial infections in a Melbourne hospital. Whereas resistance to gentamicin, tobramycin and kanamycin was encoded by one of 3 plasmids [pSK1, 18 megadalton (Md); pSK4, 22 Md; pSK9, 17 Md] in S. aureus, no similar plasmids were detected in S. epidermidis. Mediated exclusively by the chromosome in S. aureus, tetracycline resistance was encoded either by the chromosome or by a 2.8 Md plasmid in strains of S. epidermidis. The inability to detect common resistance plasmids in strains of S. aureus and S. epidermidis recovered from this outbreak is in contrast to recent observations with staphylococci from other geographic areas; nevertheless, on the basis of restriction endonuclease analyses of 3 Md chloramphenicol resistance plasmids, it is suggested that a common gene pool does exist within isolates of S. aureus and S. epidermidis from Melbourne hospitals.     

Diversity of staphylococci exhibiting high-level resistance to mupirocin

Plasmids mediating high-level resistance to mupirocin (MIC greater than 1000 mg/L) in staphylococci from various sources were studied by restriction endonuclease cleavage. Several patterns were obtained but six plasmids isolated from various Staphylococcus aureus and S. epidermidis strains were indistinguishable. The diversity and spread of these plasmids is illustrated.     

The bacterial insertion sequence element IS256 occurs preferentially in nosocomial Staphylococcus epidermidis isolates: association with biofilm formation and resistance to aminoglycosides

Staphylococcus epidermidis is a normal constituent of the healthy human microflora, but it is also the most common cause of nosocomial infections associated with the use of indwelling medical devices. Isolates from device-associated infections are known for their pronounced phenotypic and genetic variability, and in this study we searched for factors that might contribute to this flexibility. We show that mutator phenotypes, which exhibit elevated spontaneous mutation rates, are rare among both pathogenic and commensal S. epidermidis strains. However, the study revealed that, in contrast to those of commensal strains, the genomes of clinical S. epidermidis strains carry multiple copies of the insertion sequence IS256, while other typical staphylococcal insertion sequences, such as IS257 and IS1272, are distributed equally among saprophytic and clinical isolates. Moreover, detection of IS256 was found to be associated with biofilm formation and the presence of the icaADBC operon as well as with gentamicin and oxacillin resistance in the clinical strains. The data suggest that IS256 is a characteristic element in the genome of multiresistant nosocomial S. epidermidis isolates that might be involved in the flexibility and adaptation of the genome in clinical isolates.     

Antibiotic multiresistance strictly associated with IS256 and ica genes in Staphylococcus epidermidis strains from implant orthopedic infections

In this study the presence both of the ica genes, encoding for biofilm exopolysaccharide production, and the insertion sequence IS256, a mobile element frequently associated to transposons, was investigated in relationship with the prevalence of antibiotic resistance among Staphylococcus epidermidis strains. The investigation was conducted on 70 clinical isolates derived from orthopedic implant infections. Among the clinical isolates investigated a dramatic high level of association was found between the presence of ica genes as well as of IS256 and multiple-resistance to all the antibiotics tested (oxacillin, penicillin, gentamicin, erythromycin, clindamycin, chloramphenicol, sulfamethoxazole + trimethoprim, ciprofloxacin, vancomycin). Noteworthy, a striking full association between the presence of IS256 and resistance to gentamicin was found, being none of the IS256-negative strain resistant to this antibiotic. This association is probably because of the link of the corresponding aminoglycoside-resistance genes, and IS256, often co-existing within the same staphylococcal transposon. In conclusion, in orthopedics, the presence of ica genes and that of IS256 in S. epidermidis genome should both be considered as informative markers of clinically relevant strains equipped with greatest and broadest resistance potential to survive to medical treatments.     

Characterisation of chloramphenicol resistance plasmids of Staphylococcus aureus and S. epidermidis by restriction enzyme mapping techniques

Chloramphenicol resistance (Cmr) plasmids pSK2 and pSK5 from Staphylococcus aureus and pSK102 and pSK103 from S. epidermidis have been characterised and detailed restriction endonuclease cleavage maps constructed. TaqI digestion profiles illustrated the identity of pSK5 and pSK102 and also revealed a high degree of similarity between these four Cmr plasmids from Australian staphylococci and three Cmr plasmids from S. aureus strains of geographically unrelated origin. DNA-DNA hybridisation indicated that the chloramphenicol acetyltransferase determinant carried by pSK5/pSK102 could be found on other structurally-distinct Cmr plasmids. The role of S. epidermidis as a reservoir for Cmr plasmids found in S. aureus is discussed.     

Use of a DNA microarray for simultaneous detection of antibiotic resistance genes among staphylococcal clinical isolates

We developed a multiplex asymmetric PCR (MAPCR)-based DNA microarray assay for characterization of the clinically relevant antibiotic resistance genes leading to penicillin, methicillin, aminoglycoside, macrolide, lincosamide, and streptogramin B (MLS(B)) resistance in staphylococci. The DNA-based assay involves detection of specific conserved regions of the mecA, blaZ (methicillin and penicillin resistance), aac(6')-Ie-aph(2') (aminoglycoside resistance), ermA and ermC genes (MLS(B) resistance), and the msrA gene (macrolide and streptogramin B resistance). The microarray uses a variable sequence region of the 16S rRNA gene to broadly differentiate between Staphylococcus aureus and other coagulase-negative staphylococci (CoNS). The performance of the microarray was validated with a total of 178 clinically important S. aureus and 237 CoNS isolates, with correlations of 100% for S. aureus to CoNS discrimination and more than 90% for antibiotic resistance between the genotypic analysis determined by the microarray and the phenotype determined by standard methods of species identification and susceptibility testing. The major discrepant results were 17 mecA-positive CoNS and 60 aac(6')-Ie-aph(2')-positive CoNS isolates measured by microarray that were susceptible to the corresponding antibiotics based on disk diffusion assay. Overall, this microarray-based assay offers a simultaneous, fast (< or =5 h), and accurate identification of antibiotic resistance genes from a single colony, as well as species classification. Our extensive validation of the microarray suggests that it may be a useful tool to complement phenotypic susceptibility testing in clinical laboratories and to survey the spread of antibiotic resistance determinants in epidemiological studies.     

Detection of ica genes and slime production in a collection of Staphylococcus epidermidis strains from catheter-related infections in neutropenic patients

Slime production, principal virulence factor of Staphylococcus epidermidis associated with catheter-related infections is mediated by icaADBC operon wich expression is subject to phase variation. Reversible transposition of IS256 element into this operon is one of the most important mechanisms of biofilm phenotypic variation. Our study compared 28 S. epidermidis strains from catheter-related infection to 28 strains from nasal carriage concerning slime production on Congo red agar plate and ica genes and IS256 presence by PCR. ica operon was present among all slime-producing strains, and was absent among slime-negative strains. Only 79% of ica-positive strains were slime producers and no insertion of IS256 element was detected inside ica genes. A significative difference was found between catheter-related infections strains and commensal ones in terms of oxacillin (67,8 versus 35,7%) and ofloxacin resistance (75 versus 35,7%), slime production (64,2 versus 28,5%), phase variability (46,4 versus 7,1%) and ica genes presence (82,1 versus 35,7%). Our study demonstrates the role of ica genes, of phenotypic variability of slime production and antibiotic multiresistance as virulence factors of S. epidermidis associated with catheter-related infections; it confirms also the complexity and the diversity of regulation mechanisms implicated in biofilm formation.     

Presence of new mecA and mph(C) variants conferring antibiotic resistance in Staphylococcus spp. isolated from the skin of horses before and after clinic admission

Because of the frequency of multiple antibiotic resistance, Staphylococcus species often represent a challenge in incisional infections of horses undergoing colic surgery. To investigate the evolution of antibiotic resistance patterns before and after preventative peri- and postoperative penicillin treatment, staphylococci were isolated from skin and wound samples at different times during hospitalization. Most staphylococci were normal skin commensals and belonged to the common coagulase-negative group. In some cases they turned out to be opportunistic pathogens present in wound infections. MICs were determined for 12 antibiotics, and antibiotic resistance genes were detected by microarray. At hospital admission, horses harbored staphylococci that were susceptible to antibiotics or resistant to one group of drugs, mainly due to the presence of new variants of the methicillin and macrolide resistance genes mecA and mph(C), respectively. After 3 days, the percentage of Staphylococcus isolates displaying antibiotic resistance, as well as the number of resistance genes per isolate, increased moderately in hospitalized horses without surgery or penicillin treatment but dramatically in hospitalized horses after colic surgery as well as penicillin treatment. Staphylococcus species displaying multiple resistance were found to harbor mainly genes conferring resistance to beta-lactams (mecA and blaZ), aminoglycosides [str and aac(6')-Ie-aph(2')-Ia], and trimethoprim [dfr(A) and dfr(D)]. Additional genes conferring resistance to macrolides [mph(C), erm(C), and erm(B)], tetracycline [tet(K) and tet(M)], chloramphenicol [cat(pC221) and cat(pC223)], and streptothricin (sat4) appeared in several strains. Hospitalization and preventive penicillin use were shown to act as selection agents for multidrug-resistant commensal staphylococcal flora.     

Decreased susceptibility to chlorhexidine and prevalence of disinfectant resistance genes among clinical isolates of Staphylococcus epidermidis

Staphylococcus epidermidis is a versatile agent, being both a commensal and a nosocomial pathogen usually with an opportunistic role in association with implanted foreign body materials. Pre‐operative antiseptic preparation is an important strategy for reducing the risk of complications such as surgical site infection (SSI). Currently, the most widely used antiseptics are alcohols, quaternary ammonium compounds (QACs), and the bisbiguanide chlorhexidine. Occurrence of resistance to the latter agent has drawn increasing attention. The aim of this study was to investigate if decreased susceptibility to chlorhexidine among S. epidermidis was present in our setting, a Swedish university hospital. Staphylococcus epidermidis (n = 143), retrospectively collected, were obtained from prosthetic joint infections (PJI) (n = 61), post‐operative infections after cardiac surgery (n = 31), and the skin of the chest after routine disinfection prior to cardiac surgery (n = 27). In addition, 24 commensal isolates were included. Minimum inhibitory concentration (MIC) of chlorhexidine was determined on Mueller Hinton agar plates supplemented with serial dilutions of chlorhexidine. Five QAC resistance genes, qacA/B, smr, qacH, qacJ, and qacG, were detected using PCR. Decreased susceptibility to chlorhexidine was found in 54% of PJI isolates, 68% of cardiac isolates, 21% of commensal isolates, and 7% of skin isolates from cardiac patients, respectively. The qacA/B gene was present in 62/143 isolates (43%), smr in 8/143 (6%), and qacH in one isolate (0.7%). The qacA/B gene was found in 52% of PJI isolates, 61% of cardiac isolates, 25% of commensal isolates, and 19% of the skin isolates. In conclusion, decreased susceptibility to chlorhexidine, as well as QAC resistance genes, were prevalent among S. epidermidis isolates associated with deep SSIs.