Antiseptic susceptibility and distribution of antiseptic-resistance genes in methicillin-resistant Staphylococcus aureus

Dynamics underlie the drug recognition mechanism by the efflux transporter EmrE

The multidrug efflux transporter EmrE from Escherichia coli requires anionic residues in the substrate binding pocket for coupling drug transport with the proton motive force. Here, we show how protonation of a single membrane embedded glutamate residue (Glu14) within the homodimer of EmrE modulates the structure and dynamics in an allosteric manner using NMR spectroscopy. The structure of EmrE in the Glu14 protonated state displays a partially occluded conformation that is inaccessible for drug binding by the presence of aromatic residues in the binding pocket. Deprotonation of a single Glu14 residue in one monomer induces an equilibrium shift toward the open state by altering its side chain position and that of a nearby tryptophan residue. This structural change promotes an open conformation that facilitates drug binding through a conformational selection mechanism and increases the binding affinity by approximately 2000-fold. The prevalence of proton-coupled exchange in efflux systems suggests a mechanism that may be shared in other antiporters where acid/base chemistry modulates access of drugs to the substrate binding pocket.

Molecular distribution of biocide resistance genes and susceptibility to biocides among vancomycin resistant Staphylococcus aureus (VRSA) isolates from intensive care unit (ICU) of cardiac hospital- A first report from Pakistan

Background

The study was conducted with the aim to investigate the VRSA isolates in terms of their susceptibility to routinely used biocides influenced by the co-occurrence of biocide resistant gene (BRGs) and efflux pumps genes.

Methodology

Frequently touched surfaces within intensive care unit (ICU) of cardiac hospital were classified into three primary sites i.e., structure, machines and miscellaneous. Over a period of six months (January 2021 to July 2021) twenty three swabs samples were collected from these sites. Subsequently, these samples underwent both phenotypic and molecular methods for VRSA isolation and identification. Susceptibility and efficacy testing of biocides (benzalkonium chloride (BAC), cetrimide (CET) and chlorhexidine gluconate (CHG)) were evaluated using microdilution broth and suspension method. Furthermore, specific primers were used for singleplex PCR targeting BRGs (cepA, qacA, and qacE) and efflux pump (norA, norB, norC, sepA, mepA and mdeA) associated genes.

Results

We found that 72.2 % S. aureus demonstrate the presence of vanA or vanB genes with no significant difference among three sites (p > 0.05). cepA is the most dominant BRGs followed by qacA and qacE from structure site as compared to other sites (p < 0.05). BAC showed reduced biocide susceptibility and MIC50. There was no significant difference between presence or absence of BRGs and high MIC values of VRSA isolates from all three sites. However, efflux pump genes (EFPGs) particularly norA and norA + sepA had a significant association with BRGs and reduced biocide.

Conclusion

BAC is the most effective disinfectant against VRSA. Proper and controlled use of BAC is required to overcome the VRSA contamination. We recommend continuous monitoring of the BRGs prevalence for better prevention of microorganism dissemination and infection control in hospitals.

Impact of clonal lineages on susceptibility of Staphylococcus lugdunensis to chlorhexidine digluconate and chloride benzalkonium

BACKGROUND

Little is known about susceptibility of Staphylococcus lugdunensis to antiseptics. The objective of this study was to evaluate, at the molecular and phenotypic level, the susceptibility of 49 clinical S. lugdunensis strains (belonging to the seven clonal complexes [CCs] defined by multilocus sequence typing) to two antiseptics frequently used in healthcare settings (chlorhexidine digluconate [CHX] and chloride benzalkonium [BAC]).

RESULTS

The minimum inhibitory concentrations (MICs), by broth microdilution method, varied for BAC from 0.25 mg/L to 8 mg/L (MIC50 = 1 mg/L, MIC90 = 2 mg/L) and for CHX from 0.5 mg/L to 2 mg/L (MIC50 = 1 mg/L, MIC90 = 2 mg/L). The BAC and CHX minimum bactericidal concentrations (MBCs) varied from 2 mg/L to 8 mg/L (MBC50 = 4 mg/L, MBC90 = 8 mg/L) and from 2 mg/L to 4 mg/L (MBC50 and MBC90 = 4 mg/L), respectively. A reduced susceptibility to CHX (MIC = 2 mg/L) was observed for 12.2% of the strains and that to BAC (MIC ≥ 4 mg/L) for 4.1%. The norA resistance gene was detected in all the 49 isolates, whereas the qacA gene was rarely encountered (two strains; 4.1%). The qacC, qacG, qacH, and qacJ genes were not detected. The two strains harboring the qacA gene had reduced susceptibility to both antiseptics and belonged to CC3.

CONCLUSION

The norA gene was detected in all the strains, suggesting that it could belong to the core genome of S. lugdunensis. S. lugdunensis is highly susceptible to both antiseptics tested. Reduced susceptibility to BAC and CHX was a rare phenomenon. Of note, a tendency to higher MICs of BAC was detected for CC3 isolates. These results should be confirmed on a larger collection of strains.

Mechanisms of emerging resistance associated with non-antibiotic antimicrobial agents: a state-of-the-art review

Although the development of resistance by microorganisms to antimicrobial drugs has been recognized as a global public health concern, the contribution of various non-antibiotic antimicrobial agents to the development of antimicrobial resistance (AMR) remains largely neglected. The present review discusses various chemical substances and factors other than typical antibiotics, such as preservatives, disinfectants, biocides, heavy metals and improper chemical sterilization that contribute to the development of AMR. Furthermore, it encompasses the mechanisms like co-resistance and co-selection, horizontal gene transfer, changes in the composition and permeability of cell membrane, efflux pumps, transposons, biofilm formation and enzymatic degradation of antimicrobial chemicals which underlie the development of resistance to various non-antibiotic antimicrobial agents. In addition, the review addresses the resistance-associated changes that develops in microorganisms due to these agents, which ultimately contribute to the development of resistance to antibiotics. In order to prevent the indiscriminate use of chemical substances and create novel therapeutic agents to halt resistance development, a more holistic scientific approach might provide diversified views on crucial factors contributing to the persistence and spread of AMR. The review illustrates the common and less explored mechanisms contributing directly or indirectly to the development of AMR by non-antimicrobial agents that are commonly used.

Association of qacA/B and smr Carriage with Staphylococcus aureus Survival following Exposure to Antiseptics in an Ex Vivo Venous Catheter Disinfection Model

Many health care centers have reported an association between Staphylococcus aureus isolates bearing efflux pump genes and an elevated MIC/minimal bactericidal concentration (MBC) to chlorhexidine gluconate (CHG) and other antiseptics. The significance of these organisms is uncertain, given that their MIC/MBC is typically far lower than the CHG concentration in most commercial preparations. We sought to evaluate the relationship between carriage of the efflux pump genes qacA/B and smr in S. aureus and the efficacy of CHG-based antisepsis in a venous catheter disinfection model. S. aureus isolates with and without smr and/or qacA/B were utilized. The CHG MICs were determined. Venous catheter hubs were inoculated and exposed to CHG, isopropanol, and CHG-isopropanol combinations. The microbiocidal effect was calculated as the percent reduction in CFU following exposure to the antiseptic relative to the control. The qacA/B- and smr-positive isolates had modest elevations in the CHG MIC90 compared to the qacA/B- and smr-negative isolates (0.125 mcg/ml vs. 0.06 mcg/ml, respectively). However, the CHG microbiocidal effect was significantly lower for qacA/B- and/or smr-positive strains than for susceptible isolates, even when the isolates were exposed to CHG concentrations up to 400 μg/mL (0.04%); this finding was most notable for isolates bearing both qacA/B and smr (89.3% versus 99.9% for the qacA/B- and smr-negative isolates; P = 0.04). Reductions in the median microbiocidal effect were also observed when these qacA/B- and smr-positive isolates were exposed to a solution of 400 μg/mL (0.04%) CHG and 70% isopropanol (89.5% versus 100% for the qacA/B- and smr-negative isolates; P = 0.002). qacA/B- and smr-positive S. aureus isolates have a survival advantage in the presence of CHG concentrations exceeding the MIC. These data suggest that traditional MIC/MBC testing may underestimate the ability of these organisms to resist the effects of CHG. IMPORTANCE Antiseptic agents, including chlorhexidine gluconate (CHG), are commonly utilized in the health care environment to reduce rates of health care-associated infections. A number of efflux pump genes, including smr and qacA/B, have been reported in Staphylococcus aureus isolates that are associated with higher MICs and minimum bactericidal concentrations (MBCs) to CHG. Several health care centers have reported an increase in the prevalence of these S. aureus strains following an escalation of CHG use in the hospital environment. The clinical significance of these organisms, however, is uncertain, given that the CHG MIC/MBC is far below the concentration in commercial preparations. We present the results of a novel surface disinfection assay utilizing venous catheter hubs. We found that qacA/B-positive and smr-positive S. aureus isolates resist killing by CHG at concentrations far exceeding the MIC/MBC in our model. These findings highlight that traditional MIC/MBC testing is insufficient to evaluate susceptibility to antimicrobials acting on medical devices.

Staphylococcus aureus from Subclinical Cases of Mastitis in Dairy Cattle in Poland, What Are They Hiding? Antibiotic Resistance and Virulence Profile

Bovine mastitis is a common disease worldwide, and staphylococci are one of the most important etiological factors of this disease. Staphylococcus aureus show adaptability to new conditions, by which monitoring their virulence and antibiotic resistance mechanisms is extremely important, as it can lead to the development of new therapies and prevention programs. In this study, we analyzed Staphylococcus aureus (n = 28) obtained from dairy cattle with subclinical mastitis in Poland. The sensitivity of the isolated strains to antibiotics were confirmed by the disc diffusion method. Additionally, minimum inhibitory concentration values were determined for vancomycin, cefoxitin and oxacillin. Genotyping was performed by two methods: PCR melting profile and MLVF-PCR (multiple-locus variable-number tandem-repeat fingerprinting). Furthermore, the presence of antibiotic resistance and virulence genes were checked using PCR reactions. The analyzed strains showed the greatest resistance to penicillin (57%), oxytetracycline (25%) and tetracycline (18%). Among the analyzed staphylococci, the presence of 9 of 15 selected virulence-related genes was confirmed, of which the icaD, clfB and sea genes were confirmed in all staphylococci. Biofilm was observed in the great majority of the analyzed bacteria (at least 70%). In the case of genotyping among the analyzed staphylococci (combined analysis of results from two methods), 14 patterns were distinguished, of which type 2 was the dominant one (n = 10). This study provides new data that highlights the importance of the dominance of biofilm over antibiotic resistance among the analyzed strains.

[Antimicrobial Resistance and Infection Control for Gram-positive Bacteria]

Antimicrobial resistance (AMR) is a serious problem worldwide. We searched for the AMR determinants of various bacteria isolated from clinical settings and studied their resistance mechanisms and molecular epidemiology. This review focuses on the AMR of Staphylococcus aureus, a major gram-positive pathogen, which has the ability to acquire resistance to antimicrobials. The resistance factors of S. aureus are frequently found on mobile elements, including plasmids and transposons. We determined the complete DNA sequence of the tetracycline-resistance plasmid and found that the inducible expression of tetK in S. aureus was regulated by a post-transcriptional attenuation mechanism. Furthermore, outbreaks of methicillin-resistant S. aureus (MRSA) in hospitals and communities have led us to study infection controls, including the antiseptic susceptibility evaluation and molecular epidemiology of MRSA. Various antiseptic resistance determinants, such as qacA/B and smr, were identified on plasmids and characterized. We demonstrated that the plasmid-mediated efflux pump QacB variant QacIII confers fluoroquinolone efflux ability to S. aureus. Studies on MRSA epidemiology had shown that community-acquired MRSA (CA-MRSA) was disseminated into hospitals and that an increased use of alcohol-based rubs could reduce the incidence of MRSA infections in such institutions. Additionally, the study of CA-MRSA collected from communities and hospitals showed an increase in Panton-Valentine leucocidin (PVL)-positive CA-MRSA, causing severe skin and soft tissue infections. Moreover, various PVL-positive CA-MRSA clones have disseminated in Japan, whereas the USA300 LV/J clone evolved in that country. Our study provides important information regarding MRSA infection control.

Evidence for the Dissemination to Humans of Methicillin-Resistant Staphylococcus aureus ST398 through the Pork Production Chain: A Study in a Portuguese Slaughterhouse

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) ST398 was recovered from infections in humans exposed to animals, raising public health concerns. However, contact with food producing chain as a means of transmission of LA-MRSA to humans remains poorly understood. We aimed to assess if pork production chain is a source of MRSA ST398 for human colonization and infection. MRSA from live pigs, meat, the environment, and slaughterhouse workers were analyzed by Pulsed-Field Gel Electrophoresis (PFGE), spa, MLST typing, SNPs and for antibiotic resistance and virulence gene profiles. We compared core and accessory genomes of MRSA ST398 isolated from slaughterhouse and hospital. We detected MRSA ST398 (t011, t108, t1451) along the entire pork production chain (live pigs: 60%; equipment: 38%; meat: 23%) and in workers (40%). All MRSA ST398 were multidrug resistant, and the majority carried genes encoding biocide resistance and enterotoxins. We found 23 cross-transmission events between live pigs, meat, and workers (6–55 SNPs). MRSA ST398 from infection and slaughterhouse environment belonged to the same clonal type (ST398, t011, SCCmec V), but differed in 321–378 SNPs. Pork production chain can be a source of MRSA ST398 for colonization of human slaughterhouse workers, which can represent a risk of subsequent meat contamination and human infection.

Prevalence of mupirocin and chlorhexidine resistance among methicillin-resistant coagulase-negative staphylococci isolated during methicillin-resistant Staphylococcus aureus decolonization strategies

BACKGROUND

The widespread of methicillin-resistant Staphylococcus aureus (MRSA) antimicrobial decolonization in the clinical setting may lead to an increase in the prevalence of multiresistance to coagulase-negative staphylococci (CoNS) owing to their selection. This study aimed to investigate the impact of MRSA decolonization strategies, using mupirocin and chlorhexidine, on their CoNS susceptibility.

METHODS

A total of 312 CoNS isolates were collected before starting the decolonization protocols "baseline strains" (BLS) group, 330 isolates were collected after application of the targeted decolonization protocol "targeted decolonization strains" group, and 355 isolates were collected after application of the universal decolonization protocol "universal decolonization strains" group. Methicillin-resistant CoNS (MR-CoNS) were identified and tested for mupirocin and chlorhexidine susceptibilities. Heptaplex polymerase chain reaction assay was applied for simultaneous screening for chlorhexidine (CHX-R) and mupirocin resistance (Mu-R) genes.

RESULTS

Mu-R prevalence of MR-CoNS among the BLS group was considered moderate (9.1%); however, CHX-R in the BLS group was 5.8%, the rate of which significantly increased among the universal decolonization strains group.

DISCUSSION

Both MRSA decolonization strategies have an additional benefit in reducing the prevalence of MR-CoNS. The prevalence Mu-R rate didn't change significantly during either of the MRSA decolonization practices that may be due to the local nature of mupirocin application on the nasal mucosa only. In contrast CHX-R that was found to be significantly higher among the UDS group.

CONCLUSIONS

Our findings indicate that both MRSA decolonization strategies have an additional benefit in reducing the prevalence of MR-CoNS. Although the universal MRSA decolonization has superior efficacy in decolonization of CoNS, it may increase the risk of selecting CHX-R and Mu-R. In addition, other potential resistance genes should be studied.

Genetic resistance determinants to fusidic acid and chlorhexidine in variably susceptible staphylococci from dogs

BACKGROUND

Concern exists that frequent use of topically-applied fusidic acid (FA) and chlorhexidine (CHX) for canine pyoderma is driving clinically relevant resistance, despite rare description of FA and CHX genetic resistance determinants in canine-derived staphylococci. This study aimed to determine minimum inhibitory concentrations (MICs) and investigate presence of putative resistance determinants for FA and CHX in canine-derived methicillin-resistant (MR) and -susceptible (MS) staphylococci. Plasmid-mediated resistance genes (fusB, fusC, fusD, qacA/B, smr; PCR) and MICs (agar dilution) of FA and CHX were investigated in 578 staphylococci (50 MR S. aureus [SA], 50 MSSA, 259 MR S. pseudintermedius [SP], 219 MSSP) from Finland, U.S.A., North (NUK) and South-East U.K. (SEUK) and Germany. In all isolates with FA MIC ≥64 mg/L (n = 27) fusA and fusE were amplified and sequenced.

RESULTS

FA resistance determinants (fusA mutations n = 24, fusB n = 2, fusC n = 36) were found in isolates from all countries bar U.S.A. and correlated with higher MICs (≥1 mg/L), although 4 SP isolates had MICs of 0.06 mg/L despite carrying fusC. CHX MICs did not correlate with qacA/B (n = 2) and smr (n = 5), which were found in SEUK SA, and SP from NUK and U.S.A.

CONCLUSIONS

Increased FA MICs were frequently associated with fusA mutations and fusC, and this is the first account of fusB in SP. Despite novel description of qacA/B in SP, gene presence did not correlate with CHX MIC. Selection pressure from clinical use might increase prevalence of these genetic determinants, but clinical significance remains uncertain in relation to high skin concentrations achieved by topical therapy.

Staphylococcus aureus nasal decolonization strategies: a review

Introduction: Staphylococcus aureus (S. aureus) infections are associated with increased morbidity, mortality and health-care costs. Persistent nasal carriage of S. aureus found in 10-30% of the general population, constitutes a risk factor for these infections. Nasal decolonization is one of the used strategies to prevent this risk in some situations. Areas covered: Mupirocin nasal ointment has been used for the nasal decolonization and prevention of staphylococcal infections in various settings like surgeries. However, rising rates of resistance to mupirocin require the development of new decolonization agents. In this review, we will discuss mupirocin, its origins, studies that proved its efficacy and the associated resistance, as well as other decolonization agents under investigation. Expert opinion: As some limitations exist to mupirocin use, further research for alternatives is encouraged. Some old approved antiseptics (chlorhexidine, povidone-iodine) or antibiotics (rifampicin, bacitracin) have been investigated for their efficacy in this indication. Other new agents (tea tree oil, retapamulin, LTX-109, XF-73, phages, lysostaphin, squalamine analogues, etc.) are being studied. Some of them are still in preclinical phases, and others have reached clinical trials, but further research is needed. Special interest should be given to single dose decolonization strategies and to molecules that do not select resistant strains.

Decreased Prevalence of qacA-Positive Methicillin-Resistant Staphylococcus aureus in Hospitalized Patients in Tokyo, Japan

Presence of methicillin-resistant Staphylococcus aureus (MRSA) strains carrying plasmid-borne multidrug efflux pump-encoding gene, qacA/B, is a serious issue for infection control in hospitals, because they can survive hand hygiene. The qacA/B genes are divided into five subtypes: qacA, qacBI, qacBII, qacBIII, and qacBIV. The aim of this study was to investigate the prevalence and risk factors of hospitalized patients infected by respective qacA/B-positive MRSA strains between 2010 and 2016 in Tokyo, Japan. Of the 600 total MRSA strains observed, the qacA/B-positive strains constituted 19.8% (199 isolates), of which 56.8% (113 isolates), 28.6% (57 isolates), and 14.6% (29 isolates) were classified as qacA, qacBIII, and qacBII-positive strains, respectively. The prevalence of qacA-positive MRSA strains significantly decreased from July 2010 to June 2011 (34.0%) to July 2015 to May 2016 (5.3%) (p < 0.05). When staphylococcal cassette chromosome (SCC)mec types of the respective qacA/B-positive strains were determined, 81.4% of the qacA-positive strains were classified into SCCmec type II, which has recently been decreasing in hospital-acquired MRSA in Japan. Risk factor analysis showed that there were no specific clinical departments associated with the presence of qacA-positive strains. Our findings suggest that change in the MRSA clonal lineages impact to decrease the prevalence of qacA-positive strains in Japanese hospitals.

Clinical and Molecular Characteristics of qacA- and qacB-Positive Methicillin-Resistant Staphylococcus aureus Causing Bloodstream Infections

The increasing use of chlorhexidine for methicillin-resistant Staphylococcus aureus (MRSA) decolonization has raised concerns about the emergence of resistance to these agents. However, the clinical significance of MRSA positive for the qacA and qacB chlorhexidine tolerance genes has not been established. We investigated the clinical features and predictive factors of MRSA bloodstream infection (BSI) isolates, caused by qacA- and qacB-positive MRSA, from 2010 to 2016 at a tertiary hospital in South Korea. A total of 246 MRSA BSI isolates were included; 71 (28.9%) isolates carried qacA/B The annual frequency of qacA- and qacB-positive MRSA bacteremia did not change significantly over the study period. Patients infected with qacA- and qacB-positive MRSA had common risk factors for health care-associated infections, including prior antibiotic use, central venous catheterization in situ, intensive care unit-acquired bacteremia, and nosocomial infection. The qacA- and qacB-positive isolates were also associated with an increasing chlorhexidine MIC and resistance to non-β-lactam antibiotics. The qacA- and qacB-positive isolates were more likely to belong to sequence type 5 (ST5), which is a common health care-associated MRSA strain in South Korea. In multivariable analyses, qacA- and qacB-positive MRSA isolates were found to be associated with agr dysfunction (adjusted odds ratio [aOR], 6.45; 95% confidence interval [CI], 2.59 to 16.10), ST5 MRSA strain (aOR, 4.96; 95% CI, 1.85 to 13.26), nosocomial infection (aOR, 4.88; 95% CI, 2.20 to 10.83), and antibiotic use within the previous 3 months (aOR, 2.59; 95% CI, 1.20 to 5.59). These findings suggest that the microbiological features of qacA and qacB carriage provide a selective advantage for specific MRSA strains in hospital environments.

Chlorhexidine and octenidine use, carriage of qac genes, and reduced antiseptic susceptibility in methicillin-resistant Staphylococcus aureus isolates from a healthcare network

OBJECTIVES

With the widespread use of antiseptics in healthcare facilities for the prevention of methicillin-resistant Staphylococcus aureus (MRSA) transmission, there are concerns for antiseptic tolerance and resistance. We sought to understand the use of chlorhexidine and octenidine, carriage of qac genes, and reduced antiseptic susceptibilities.

METHODS

A serial cross-sectional study was conducted in an acute care hospital and three extended-care facilities of a healthcare network in June-July, 2014-2016. Two of the extended-care facilities were exposed to intranasal octenidine and universal daily chlorhexidine/octenidine bathing. The minimum inhibitory concentration (MIC) levels and qac genes were determined by broth microdilution tests and whole genome sequencing respectively. Multivariable logistic regression was used to assess for the independent associations between antiseptic exposures, qac genes, and reduced antiseptic susceptibilities.

RESULTS

A total of 878 MRSA isolates were obtained. There were associations between qacA/B carriage and chlorhexidine (adjusted odds ratio (aOR) 7.80; 95% confidence interval (CI) 3.25-18.71) and octenidine (aOR 11.79; 95% CI 5.14-27.04) exposures. Chlorhexidine exposure was associated with reduced chlorhexidine susceptibility (MIC ≥4 mg/L) (aOR 3.15; 95% CI 1.14-8.74). Carriage of qacA/B (aOR 10.65; 95% CI 4.14-27.40) or qacC (aOR 2.55; 95% CI 1.22-5.32) had an association with reduced chlorhexidine susceptibility; while MRSA sequence type modified the association. However, we found no direct association between (i) antiseptics use and qacC carriage, (ii) octenidine exposure and reduced susceptibility, and (iii) reduced octenidine susceptibility and qacA/B or qacC carriage.

CONCLUSIONS

Antiseptic exposures were associated with carriage of qac genes. Chlorhexidine exposure was associated with reduced chlorhexidine susceptibility, requiring continued surveillance for the emergence of resistance.

Development of a real-time assay to determine the frequency of qac genes in methicillin resistant Staphylococcus aureus

PURPOSE

The emergence of antiseptic resistance and/or antiseptic-resistance genes in methicillin-resistant Staphylococcus aureus (MRSA) may result in failure of decolonization treatments. Plasmid-encoded efflux pump genes qacA/B and qacC (smr) confer tolerance to chlorhexidine and quaternary ammonium compounds. The objective of this study was to develop and validate a multiplex real time-PCR assay for detection of antiseptic-resistance genes, apply the assay on 200 MRSA isolates and explore if carriage of these genes was associated with resistance to topical antibiotics.

METHODOLOGY

A SYBR-Green based multiplex real time-PCR assay was developed to detect qacA/B, qacC, and mecA (internal control) simultaneously. The multiplex assay was compared against conventional single-plex PCR followed by agarose gel electrophoresis, using DNA from the first 73 MRSA isolates, followed by multiplex testing of the remaining 127 MRSA isolates. All 200 MRSA isolates were tested for susceptibility to mupirocin, retapamulin, neomycin, bacitracin and octenidine. The genetic diversity of the isolates was investigated by spa-typing.

RESULTS

The concordance between multiplex and conventional PCR, in assignments of qacA/B and qacC status were 99%(72/73) and 100%(73/73) respectively. Among 200 MRSA isolates, 48(24%) and 44(23%) were found to harbour qacA/B and qacC genes, respectively. These isolates remained susceptible to many common decolonization agents, except mupirocin. The predominant spa-types were t020 and t1081 (41 and 32 isolates respectively).

CONCLUSION

The real-time assay performed acceptably for the detection of qac genes. A high prevalence of antiseptic-resistance genes were detected in the MRSA isolates in our population and appeared to be associated with spa-type t1081.

Surgical hand antisepsis: experimental study

Purpose

Nosocomial infections account for one of the most serious complications in hospitalized patients around the world. Surgical site infections have significant economic implications, and surgical antisepsis plays an important role in such processes.

Methods

With prior approval by the Institutional Review Board and informed consent, 10 volunteers were randomly assigned to 3 protocols on hand antisepsis: protocol A (chloroxylenol 3%), protocol B (benzalkonium chloride at 1%), and protocol C (ethyl alcohol 61%, 1% chlorhexidine gluconate). Smears from both hands were cultured after each hand pro tocol (t0) and at the end of suturing (t1). Colony forming units were counted (CFUs on blood agar dishes) with digital counting software (Open CFU). Friedman test was used to compare the mean values among the groups, and a Bonferroni correction was made to determine the dissimilar group, with a P = 0.015.

Results

At t0 for protocol A the CFU count was 82.8 ± 1.3; protocol B was 9.7 ± 30; protocol C was 0.1 ± 0.3 (P < 0.001). At t1 for protocol A the CFU was 80.7 ± 89.4; protocol B was 7.5 ± 32; protocol C was 0.0 ± 0.0 (P < 0.001). No adverse events were present among the subjects.

Conclusion

Ethyl alcohol at 61% with 1% chlorhexidine gluconate showed higher efficacy than the traditional washing antiseptics.

Inhibitory effects of silybin on the efflux pump of methicillin‑resistant Staphylococcus aureus

Bacterial multidrug resistance efflux systems serve an important role in antimicrobial resistance. Thus, identifying novel and effective efflux pump inhibitors that are safe with no adverse side effects is urgently required. Silybin is a flavonolignan component of the extract from the milk thistle seed. To order to investigate the mechanism by which silybin inhibits the efflux system of methicillin-resistant Staphylococcus aureus (MRSA), antimicrobial susceptibility testing and the double-plate method were used to evaluate the effect of silybin on MRSA41577. The ability of silybin to inhibit the efflux of ciprofloxacin from MRSA was evaluated by performing a fluorescence assay. Reverse transcription-quantitative polymerase chain reaction analysis revealed that silybin reduced the expression of the quinolone resistance protein NorA (norA) and quaternary ammonium resistance proteins A/B (qacA/B) efflux genes in MRSA. This suggested that silybin may effectively inhibit the efflux system of MRSA41577. Compared with the control, MRSA41577 treated with silybin for 16 h exhibited a 36 and 49% reduction in the expression of norA and qacA/B, respectively. Inhibition of the expression of these genes by silybin restored the sensitivity of MRSA41577 to antibiotics, indicating that efflux pump inhibitors, which act by inhibiting the efflux system of MRSA, may disrupt the MRSA resistance to antibiotics, rendering the bacteria sensitive to these drugs.

Frequency of antiseptic resistance genes in clinical staphycocci and enterococci isolates in Turkey

Background

Disinfectants and antiseptics are biocides widely used in hospitals to prevent spread of pathogens. It has been reported that antiseptic resistance genes, qac’s, caused tolerance to a variety of biocidal agents, such as benzalkonium chloride (BAC) and chlorhexidine digluconate (CHDG) in Staphylococcus spp. isolates. We aimed to search the frequency of antiseptic resistance genes in clinical Staphylococcus spp. and Enterococcus spp. isolates to investigate the possible association with antiseptic tolerance and antibiotic resistance.

Methods

Antiseptic resistance genes (qacA/B, smr, qacG, qacH, and qacJ) isolated from Gram-positive cocci (69 Staphylococcus spp. and 69 Enterococcus spp.) were analyzed by PCR method. The minimum inhibitory concentrations (MICs) of BAC and CHDG were determined by agar dilution method, whereas antibiotic susceptibility was analyzed by disk diffusion method according to Clinical and Laboratory Standards Institute (CLSI) criteria.

Results

The frequency of antiseptic resistance genes was found to be high (49/69; 71.0%) in our clinical staphylococci isolates but absent (0/69; 0%) in enterococci isolates. The frequency of qacA/B and smr genes was higher (25/40; 62.5% and 7/40; 17.5%, respectively) in coagulase negative staphylococci (CNS) when compared to Staphylococcus aureus strains (3/29; 10.3%, and 4/29; 13.8%, respectively). In contrast, the frequency of qacG and qacJ genes was higher (11/29; 37.9% and 8/29; 27.5%, respectively) in S. aureus than those of CNS (5/40; 12.5%, 10/40; 25.0%) strains. qacH was not identified in none of the strains. We found an association between presence of antiseptic resistance genes and increased MIC values of BAC (>4 μg/mL) in staphylococci and it was found to be statistically statistically significant (p < 0.01). We also showed that MICs of BAC and CHDG of vancomycin-resistant enterococci (VRE) isolates were significantly higher than those of vancomycin-susceptible enterococci (VSE) isolates (p < 0.01).

Conclusions

For our knowledge, our study is the first to investigate antiseptic resistance genes in enterococci and also qacG, qacH, and qacJ genes in staphylococci isolates in Turkey. Further studies are needed to revise the biocide policy and to support infection control programs to avoid the development of new resistance mechanisms.

Impact of Health Care Exposure on Genotypic Antiseptic Tolerance in Staphylococcus aureus Infections in a Pediatric Population

Staphylococcus aureus possessing either the smr gene or the qacA/B genes is associated with decreased susceptibility to chlorhexidine gluconate (CHG) and other antiseptics. Previous studies of antiseptic-tolerant staphylococci have focused largely on high-risk populations, and the exact role of health care exposure in the acquisition of these organisms is unclear. We sought to describe the risk factors and features of infection caused by antiseptic-tolerant S. aureus in a general pediatric population. Isolates were selected from an ongoing S. aureus surveillance study. Every third sequential isolate in the year 2014 was selected for inclusion. All isolates underwent PCR for the genes qacA/B and smr Medical records were reviewed. Five hundred six isolates were included in the study, with 377 (74.3%) being community acquired. One hundred (19.8%) isolates were smr positive and 79 (15.6%) qacA/B positive. In univariable analyses, the presence of either gene was associated with underlying medical conditions, nosocomial acquisition, recent hospitalization, central venous lines, and CHG exposure. In multivariable analyses, only differences between patients with chronic medical conditions (odds ratio [OR] = 1.72; 95% confidence interval [CI], 1.22 to 2.64) and nosocomial acquisition (OR = 2.48; 95% CI, 1.16 to 8.17) remained statistically significant. Among patients without risk factors, 27.9% had infection with an antiseptic-tolerant isolate. smr- or qacA/B-positive S. aureus isolates are common in children and are independently associated with nosocomial acquisition and underlying medical conditions. These findings imply a role for the health care environment in acquisition of these organisms. However, genotypic antiseptic tolerance was seen in >25% of healthy children with an S. aureus infection, indicating that these organism are prevalent in the community as well.

Detecting Staphylococcus aureus Virulence and Resistance Genes: a Comparison of Whole-Genome Sequencing and DNA Microarray Technology

Staphylococcus aureusis a major bacterial pathogen causing a variety of diseases ranging from wound infections to severe bacteremia or intoxications. Besides host factors, the course and severity of disease is also widely dependent on the genotype of the bacterium. Whole-genome sequencing (WGS), followed by bioinformatic sequence analysis, is currently the most extensive genotyping method available. To identify clinically relevant staphylococcal virulence and resistance genes in WGS data, we developed anin silicotyping scheme for the software SeqSphere(+)(Ridom GmbH, Münster, Germany). The implemented target genes (n= 182) correspond to those queried by the IdentibacS. aureusGenotyping DNA microarray (Alere Technologies, Jena, Germany). Thein silicoscheme was evaluated by comparing the typing results of microarray and of WGS for 154 humanS. aureusisolates. A total of 96.8% (n= 27,119) of all typing results were equally identified with microarray and WGS (40.6% present and 56.2% absent). Discrepancies (3.2% in total) were caused by WGS errors (1.7%), microarray hybridization failures (1.3%), wrong prediction of ambiguous microarray results (0.1%), or unknown causes (0.1%). Superior to the microarray, WGS enabled the distinction of allelic variants, which may be essential for the prediction of bacterial virulence and resistance phenotypes. Multilocus sequence typing clonal complexes and staphylococcal cassette chromosomemecelement types inferred from microarray hybridization patterns were equally determined by WGS. In conclusion, WGS may substitute array-based methods due to its universal methodology, open and expandable nature, and rapid parallel analysis capacity for different characteristics in once-generated sequences.

Clinical and Molecular Features of Decreased Chlorhexidine Susceptibility among Nosocomial Staphylococcus aureus Isolates at Texas Children's Hospital

One of the strategies utilized to decrease infections in the hospital setting relies on topical antimicrobials and antiseptics. While their use is beneficial, concerns arise over the potential to develop resistance or tolerance to these agents. We examined nosocomial Staphylococcus aureus isolates from 2007 to 2013 for the presence of genes associated with tolerance to chlorhexidine. Isolates and patients were identified from an S. aureus surveillance study at Texas Children's Hospital. Nosocomial S. aureus isolates (those causing infection at ≥72 h of hospitalization) were identified and underwent PCR for the qacA or qacB (qacA/B) and smr genes associated with elevated minimum bactericidal concentrations of chlorhexidine. Molecular typing with pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and agr typing and a review of the medical record were performed. Two hundred forty-seven nosocomial S. aureus infections were identified. Overall, 111 isolates carried one or both genes (44.9%); 33.1% were positive for smr, 22.7% were positive for qacA/B, and 10.9% of the isolates possessed both genes. The smr-positive isolates were more often resistant to methicillin, ciprofloxacin, and/or clindamycin. The isolates positive for qacA/B were more often associated with indwelling central venous catheters and a vancomycin MIC of ≥2 μg/ml. Isolates carrying either smr or qacA/B were associated with a diagnosis of bacteremia. The smr-positive isolates more often belonged to sequence type 8 (ST8) than the isolates that were positive for qacA/B. Mupirocin resistance was detected in 2.8% of the isolates. Antiseptic-tolerant S. aureus strains are common in our children's hospital and are associated with decreased susceptibility to other systemic antimicrobials and with bloodstream infections. Further work is needed to understand the implications that these organisms have on the hospital environment and antiseptic use in the future.

Chlorhexidine and mupirocin susceptibilities in methicillin-resistant Staphylococcus aureus isolates from bacteraemia and nasal colonisation

Chlorhexidine and mupirocin have been increasingly used in healthcare facilities to eradicate methicillin-resistant Staphylococcus aureus (MRSA) carriage. The aim of this study was to determine the prevalence and mechanisms of chlorhexidine and mupirocin resistance in MRSA from invasive infections and colonisation. MRSA isolates obtained from blood and nasal samples between 2012 and 2014 were analysed. Susceptibility to mupirocin was determined by disk diffusion and Etest and susceptibility to chlorhexidine by broth microdilution. The presence of mupA and qac (A/B and C) genes was investigated by PCR. Molecular typing was performed in high-level mupirocin-resistant (HLMR) isolates. Mupirocin resistance was identified in 15.6% of blood isolates (10.9% HLMR) and 15.1% of nasal isolates (12.0% HLMR). Presence of the mupA gene was confirmed in all HLMR isolates. For blood isolates, chlorhexidine minimum inhibitory concentrations (MICs) ranged from ≤0.125 to 4mg/L and minimum bactericidal concentrations (MBCs) from ≤0.125 to 8mg/L. In nasal isolates, chlorhexidine MICs and MBCs ranged from ≤0.125 to 2mg/L. The qacA/B gene was detected in 2.2% of MRSA isolates (chlorhexidine MIC range 0.25-2mg/L) and the qacC gene in 8.2% (chlorhexidine MIC range ≤0.125-1mg/L). The prevalence of qacC was 18.9% in HLMR isolates and 3.6% in mupirocin-susceptible isolates (P=0.009). Most of the HLMR isolates (97.1%) belonged to ST125 clone. These results suggest that chlorhexidine has a higher potential to prevent infections caused by MRSA. In contrast, mupirocin treatment should be used cautiously to avoid the spread of HLMR MRSA.

High Prevalence of Biocide Resistance Determinants in Staphylococcus aureus Isolates from Three African Countries

We assessed the prevalence of six biocide resistance genes among 82 methicillin-resistant Staphylococcus aureus (MRSA) and 219 methicillin-susceptible S. aureus (MSSA) isolates from three African countries; the prevalence was very high for sepA (95.3%), mepA (89.4%), and norA (86.4%), intermediate for lmrS (60.8%) and qacAB (40.5%), and low for smr (3.7%). A significant association between biocide resistance genes and antibiotic resistance was observed, and a new cutoff MIC of ≥1 mg/liter for chlorhexidine nonsusceptibility was defined.

Characterization of Staphylococcus aureus infections in children with Down syndrome

Staphylococcus aureus infections in the Down syndrome (DS) population have not been well characterized. This study determined clinical and molecular characteristics of S. aureus infections in children with DS followed at Texas Children's Hospital (TCH), from 2001 to 2011. Patients were retrospectively identified from an ongoing S. aureus surveillance study. Medical records were reviewed. Isolates were characterized by antimicrobial susceptibility, pulsed-field gel electrophoresis patterns, and detection of PVL genes (pvl), mupA (high-level mupirocin resistance gene), smr (chlorhexidine resistance conferring gene), and Staphylococcal Chromosomal Cassette mec (SCCmec) type. Twenty-six patients with DS had a total of 34 S. aureus infections (8 recurrent); 61% were MRSA. DS patients represented 16.8 per 10,000 community onset S. aureus infections seen at TCH. Among 26 initial infections 17 were skin and soft tissue (SSTI), 7 were outer or middle ear and 2 were invasive infections. Seventeen patients were hospitalized. Thirteen (65%) of 20 available isolates were USA300, 14 were pvl+, 5 were mupA+, and 8 were smr+. Five of 8 (63%) recurrent infections were ear infections. All 4 recurrent ear isolates available for study were smr+, ciprofloxacin non-susceptible and treated with ciprofloxacin otic drops. S. aureus infections among patients with DS were similar in presentation to other patient groups, except for a greater proportion being associated with ear infections. Seventy percent of ear fluid isolates carried antiseptic and fluoroquinolone resistance genes. A study of a greater number of DS patients is warranted to further explore these findings.

Recurrent Methicillin-Resistant Staphylococcus aureus Cutaneous Abscesses and Selection of Reduced Chlorhexidine Susceptibility during Chlorhexidine Use

We describe the selection of reduced chlorhexidine susceptibility during chlorhexidine use in a patient with two episodes of cutaneous USA300 methicillin-resistant Staphylococcus aureus abscess. The second clinical isolate harbors a novel plasmid that encodes the QacA efflux pump. Greater use of chlorhexidine for disease prevention warrants surveillance for resistance.

Investigating the mobilome in clinically important lineages of Enterococcus faecium and Enterococcus faecalis

BACKGROUND

The success of Enterococcus faecium and E. faecalis evolving as multi-resistant nosocomial pathogens is associated with their ability to acquire and share adaptive traits, including antimicrobial resistance genes encoded by mobile genetic elements (MGEs). Here, we investigate this mobilome in successful hospital associated genetic lineages, E. faecium sequence type (ST)17 (n=10) and ST78 (n=10), E. faecalis ST6 (n=10) and ST40 (n=10) by DNA microarray analyses.

RESULTS

The hybridization patterns of 272 representative targets including plasmid backbones (n=85), transposable elements (n=85), resistance determinants (n=67), prophages (n=29) and clustered regularly interspaced short palindromic repeats (CRISPR)-cas sequences (n=6) separated the strains according to species, and for E. faecalis also according to STs. RCR-, Rep_3-, RepA_N- and Inc18-family plasmids were highly prevalent and with the exception of Rep_3, evenly distributed between the species. There was a considerable difference in the replicon profile, with rep 17/pRUM , rep 2/pRE25 , rep 14/EFNP1 and rep 20/pLG1 dominating in E. faecium and rep 9/pCF10 , rep 2/pRE25 and rep 7 in E. faecalis strains. We observed an overall high correlation between the presence and absence of genes coding for resistance towards antibiotics, metals, biocides and their corresponding MGEs as well as their phenotypic antimicrobial susceptibility pattern. Although most IS families were represented in both E. faecalis and E. faecium, specific IS elements within these families were distributed in only one species. The prevalence of IS256-, IS3-, ISL3-, IS200/IS605-, IS110-, IS982- and IS4-transposases was significantly higher in E. faecium than E. faecalis, and that of IS110-, IS982- and IS1182-transposases in E. faecalis ST6 compared to ST40. Notably, the transposases of IS981, ISEfm1 and IS1678 that have only been reported in few enterococcal isolates were well represented in the E. faecium strains. E. faecalis ST40 strains harboured possible functional CRISPR-Cas systems, and still resistance and prophage sequences were generally well represented.

CONCLUSIONS

The targeted MGEs were highly prevalent among the selected STs, underlining their potential importance in the evolution of hospital-adapted lineages of enterococci. Although the propensity of inter-species horizontal gene transfer (HGT) must be emphasized, the considerable species-specificity of these MGEs indicates a separate vertical evolution of MGEs within each species, and for E. faecalis within each ST.

Photodynamic antimicrobial polymers for infection control

Hospital-acquired infections pose both a major risk to patient wellbeing and an economic burden on global healthcare systems, with the problem compounded by the emergence of multidrug resistant and biocide tolerant bacterial pathogens. Many inanimate surfaces can act as a reservoir for infection, and adequate disinfection is difficult to achieve and requires direct intervention. In this study we demonstrate the preparation and performance of materials with inherent photodynamic, surface-active, persistent antimicrobial properties through the incorporation of photosensitizers into high density poly(ethylene) (HDPE) using hot-melt extrusion, which require no external intervention except a source of visible light. Our aim is to prevent bacterial adherence to these surfaces and eliminate them as reservoirs of nosocomial pathogens, thus presenting a valuable advance in infection control. A two-layer system with one layer comprising photosensitizer-incorporated HDPE, and one layer comprising HDPE alone is also described to demonstrate the versatility of our approach. The photosensitizer-incorporated materials are capable of reducing the adherence of viable bacteria by up to 3.62 Log colony forming units (CFU) per square centimeter of material surface for methicillin resistant Staphylococcus aureus (MRSA), and by up to 1.51 Log CFU/cm² for Escherichia coli. Potential applications for the technology are in antimicrobial coatings for, or materials comprising objects, such as tubing, collection bags, handrails, finger-plates on hospital doors, or medical equipment found in the healthcare setting.

Novel insight into antimicrobial resistance and sensitivity phenotypes associated to qac and norA genotypes in Staphylococcus aureus

Staphylococcus aureus strains harboring QacA, QacB, QacC, QacG transporters and norA promoter up-regulating mutations were characterized by phenotype microarray (PM), standard methods for susceptibility testing, and ethidium bromide efflux assays, in order to increase knowledge on phenotypes associated to efflux pumps and their substrates. PM data and standard susceptibility testing lead to the identification of new potential efflux targets, such as guanidine hydrochloride or 8-hydroxyquinoline for QacA and QacC pumps, respectively. The identification of compounds to which the presence of efflux pumps induced increased susceptibility opens new perspectives for potential adjunct anti-resistance treatment (i.e. strains bearing QacB transporters showed increased susceptibility to thioridazine, amitriptyline and orphenadrine). Although the tested isolates were characterized by high degree of heterogeneity, a hallmark of clinical isolates, direct ethidium bromide efflux assays were effective in highlighting differences in efflux efficiency among strains. These data add to characterization of substrate specificity in the different classes of staphylococcal multidrug efflux systems conferring specific substrate profiles and efflux features to each of them.

Relationship between the resistance genes to quaternary ammonium compounds and antibiotic resistance in staphylococci isolated from surgical site infections

BACKGROUND

We aimed to investigate the prevalence of disinfectant resistance genes (qacA/qacB,qacC) and the aminoglycosides resistance genes [(aac(6')aph(2''),aph(3')-IIIa,ant(4')-Ia)] in both S. aureus and coagulase-negative staphylococcal strains (CoNS) isolated from surgical site infections.

MATERIAL AND METHODS

Totally, 130 staphylococcal strains isolated from surgical site infections between January 2012 and February 2013 were included in the study. The PCR technique was employed to verify any presence of methicillin resistance gene (mecA), aminoglycoside resistance genes [(aac(6')/aph (2''), aph(3)-III a ant (4')-1a)], and disinfectant resistance genes (qacA/qacB,qacC) in staphylococci.

RESULTS

MecA gene was determined in 58 (44.6%) of 130 staphylococcal isolates. A total of 28 (73.7%) of 38 S. aureus isolates were found to be positive for the mecA gene, and 4 (12.9%) of 31 isolates sensitive to amikacin were sensitive to methicillin. Eighteen (47.4%) of 38 amikacin-resistant S. aureus isolates were found to be positive for qacA/qacB genes and 11 (8.9%) of them were positive for qacC gene. Both mecA and qacA/qacB genes were found to be positive at the same time in 19 amikacin-resistant S. aureus strains. Seven (18.4%) S. aureus isolates were determined to be positive for qacA/qacB and qacC genes. Frequency of qacA/B genes was found to be 47.4% among amikacin-resistant S. aureus strains, while qacC gene was found to be 28.9% (p<0.05). The ratio of qacA/B and qacC genes in CoNS was found to be 37.9% and 20.7%, respectively (p<0.05).

CONCLUSIONS

Quaternary ammonium resistance genes were found to be positive at a remarkable ratio in the staphylococcal isolates from surgical wounds. Especially, the high rates of aminoglycosides and methicillin-resistance gene was remarkable in S. aureus isolates. Quaternary ammonium resistance genes were found to be positive.

Decreased susceptibilities to Retapamulin, Mupirocin, and Chlorhexidine among Staphylococcus aureus isolates causing skin and soft tissue infections in otherwise healthy children

Topical antimicrobial and antiseptic agents are commonly used in the management of minor skin and soft tissue infections (SSTIs). Resistance to mupirocin has been documented in Staphylococcus aureus isolates causing SSTIs. Data are limited, however, on the prevalence of retapamulin resistance or tolerance to antiseptics. We sought to determine the prevalence of decreased susceptibility to retapamulin and mupirocin as well as the potential for decreased chlorhexidine susceptibility of S. aureus isolates from SSTIs in children. Two hundred isolates from patients with a single SSTI and 200 isolates from patients with ≥3 previous episodes from the years 2010 to 2012 were selected from an S. aureus surveillance study. Screening for retapamulin resistance was performed by the broth macrodilution method; mupirocin MICs were determined by Etest. PCR was performed for the presence of the smr gene associated with elevated MICs/minimum bactericidal concentrations (MBCs) to chlorhexidine. Among the isolates screened, 38 isolates (9.5%) exhibited retapamulin resistance, of which 22 (57.9%) were methicillin-resistant S. aureus (MRSA). Two isolates (0.5%) displayed cross-resistance to retapamulin and linezolid. Thirty-nine isolates (9.8%) were found to have mupirocin resistance. smr-positive S. aureus accounted for 14% of isolates. The proportion of smr-positive organisms increased during the study (P = 0.005). The prevalence of in vitro resistance to topical antimicrobials among S. aureus isolates causing SSTI in healthy children in our community is almost 10%. Retapamulin resistance was associated with cross-resistance to linezolid in 0.5% of isolates. In addition, there was an increase in the proportion of smr-positive isolates. Further research including clinical correlations with these findings is warranted.

Genetic determinants of antimicrobial resistance in Gram positive bacteria from organic foods

Bacterial biocide resistance is becoming a matter of concern. In the present study, a collection of biocide-resistant, Gram-positive bacteria from organic foods (including 11 isolates from genus Bacillus, 25 from Enterococcus and 10 from Staphylococcus) were analyzed for genes associated to biocide resistance efflux pumps and antibiotic resistance. The only qac-genes detected were qacA/B (one Bacillus cereus isolate) and smr (one B. cereus and two Staphylococcus saprophyticus isolates). Efflux pump genes efrA and efrB genes were detected in Staphylococcus (60% of isolates), Bacillus (54.54%) and Enterococcus (24%); sugE was detected in Enterococcus (20%) and in one Bacillus licheniformis; mepA was detected in Staphylococcus (60%) and in one Enterococcus isolate (which also carried mdeA), and norE gene was detected only in one Enterococcus faecium and one S. saprophyticus isolate. An amplicon for acrB efflux pump was detected in all but one isolate. When minimal inhibitory concentrations (MICs) were determined, it was found that the addition of reserpine reduced the MICs by eight fold for most of the biocides and isolates, corroborating the role of efflux pumps in biocide resistance. Erythromycin resistance gene ermB was detected in 90% of Bacillus isolates, and in one Staphylococcus, while ereA was detected only in one Bacillus and one Staphyloccus, and ereB only in one Staphylococcus. The ATP-dependent msrA gene (which confers resistance to macrolides, lincosamides and type B streptogramins) was detected in 60% of Bacillus isolates and in all staphylococci, which in addition carried msrB. The lincosamide and streptogramin A resistance gene lsa was detected in Staphylococcus (40%), Bacillus (27.27%) and Enterococcus (8%) isolates. The aminoglycoside resistance determinant aph (3_)-IIIa was detected in Staphylococcus (40%) and Bacillus (one isolate), aph(2_)-1d in Bacillus (27.27%) and Enterococcus (8%), aph(2_)-Ib in Bacillus (one isolate), and the bifunctional aac(6_)1e-aph(2_)-Ia in Staphylococcus (20%), Enterococcus (8%) and Bacillus (one isolate). Chloramphenicol resistance cat gene was detected in Enterococcus (8%) and Staphylococcus (20%), and blaZ only in Staphylococcus (20%). All other antibiotic or biocide resistance genes investigated were not detected in any isolate. Isolates carrying multiple biocide and antibiotic determinants were frequent among Bacillus (36.36%) and Staphylococcus (50%), but not Enterococcus. These results suggest that biocide and antibiotic determinants may be co-selected.

Staphylococcus aureus Infections in Children With Congenital Heart Disease

BACKGROUND

Congenital heart disease (CHD) is the most common risk factor for infective endocarditis (IE) in children. Staphylococcus aureus is among the most common organisms to cause IE, yet there are little data describing the risk factors for invasive S aureus disease in children with CHD. We examined the epidemiology of S aureus infections in children with CHD.

METHODS

Patients with a history of CHD and S aureus infection were identified from a surveillance study of S aureus infections at Texas Children's Hospital. Clinical and laboratory data from medical records were reviewed. All isolates were screened for the presence of the antiseptic tolerance gene qacA/B. Dichotomous variables were compared with Fisher's exact test and continuous variables with Mann-Whitney U tests, and two-tailed P values of <.05 were considered significant.

RESULTS

Two hundred forty-eight S aureus infections developed in 216 patients with CHD. Methicillin resistance was seen in 53.6% of isolates. Surgical site infections accounted for 28.2% of cases and bacteremia accounted for 20.4% of cases. Bacteremia was associated with IE in 29.5% of the episodes. Infective endocarditis was more often associated with prolonged bacteremia, thrombocytopenia, and a higher C-reactive protein (CRP) compared with uncomplicated bacteremia. The qacA/B gene was found in 16.9% of isolates and was associated with bacteremia and prolonged hospitalization.

CONCLUSIONS

Staphylococcus aureus is an important cause of morbidity among children with CHD. Infective endocarditis was common with S aureus bacteremia in this population; in addition, prolonged bacteremia, thrombocytopenia, and CRP >10 mg/dL may serve as diagnostic adjuncts for IE. qacA/B-positive isolates are associated with adverse clinical outcomes.

Staphylococcus aureus infections in pediatric oncology patients: high rates of antimicrobial resistance, antiseptic tolerance and complications

BACKGROUND

: Patients with malignancies represent a population at high risk for drug-resistant infections. We sought to determine the clinical spectrum and molecular epidemiology of Staphylococcus aureus infections in pediatric oncology patients followed at Texas Children's Hospital (Houston, TX). Furthermore, we determined the prevalence of the chlorhexidine resistance gene qacA/B from isolates in this unique population.

METHODS

: Patients with a history of malignancy and a culture-proven S. aureus infection were identified from 2001 to 2011. Antibiotic susceptibility, pulsed-field gel electrophoresis and detection of qacA/B by polymerase chain reaction were performed on all isolates. Medical records for all patients were reviewed.

RESULTS

: During the study period, 213 isolates were identified from 179 patients with malignancies. Thirty-one percent of the isolates were methicillin-resistant S. aureus. The most common infectious diagnosis was bacteremia (85/213 [39.9%], with 72/85 [84.7%] being catheter-associated). Thirteen patients with bacteremia were found to have pulmonary nodules at the time of presentation; only S. aureus was found in tissue in 5 of the 6 patients who underwent lung biopsy. After 2007, 18.2% of isolates were qacA/B positive with a steady increase in prevalence every year (χ for trend P = 0.04).

CONCLUSIONS

: S. aureus is a significant cause of morbidity and mortality in pediatric oncology patients at Texas Children's Hospital. In addition to the more well-known clinical manifestations, this pathogen can also be associated with pulmonary nodules. Furthermore, the prevalence of S. aureus isolates carrying antiseptic resistance genes increased in this population. Additional clinical and molecular studies and surveillance among pediatric oncology patients are warranted to further explore these findings.

Biocide tolerance in bacteria

Biocides have been employed for centuries, so today a wide range of compounds showing different levels of antimicrobial activity have become available. At the present time, understanding the mechanisms of action of biocides has also become an important issue with the emergence of bacterial tolerance to biocides and the suggestion that biocide and antibiotic resistance in bacteria might be linked. While most of the mechanisms providing antibiotic resistance are agent specific, providing resistance to a single antimicrobial or class of antimicrobial, there are currently numerous examples of efflux systems that accommodate and, thus, provide tolerance to a broad range of structurally unrelated antimicrobials, both antibiotics and biocides. If biocide tolerance becomes increasingly common and it is linked to antibiotic resistance, not only resistant (even multi-resistant) bacteria could be passed along the food chain, but also there are resistance determinants that can spread and lead to the emergence of new resistant microorganisms, which can only be detected and monitored when the building blocks of resistance traits are understood on the molecular level. This review summarizes the main advances reached in understanding the mechanism of action of biocides, the mechanisms of bacterial resistance to both biocides and antibiotics, and the incidence of biocide tolerance in bacteria of concern to human health and the food industry.

Presence of antiseptic resistance genes in porcine methicillin-resistant Staphylococcus aureus

Numerous studies have documented the presence of methicillin-resistant Staphylococcus aureus (MRSA) in meat-producing animals, which has led to concern about its spread into the community. Disinfectants play an important role in reduction of contamination in both animal husbandry and food-preparation, helping control spread of organisms from foodstuffs, including raw meat. Plasmid-borne antiseptic resistance (AR) genes increasing tolerance to several disinfectants have been reported in S. aureus of human origin (qacA/B and smr) and from bovine, equine, and caprine staphylococcal isolates (qacG, qacH, and qacJ). This study investigated the presence of AR genes in porcine MRSA isolates. Plasmid DNA from 100 MRSA ST9 strains isolated from pig carcasses was amplified for the presence of AR genes. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) to benzalkonium chloride (BC) and chlorhexidine gluconate (CHX) were determined in AR gene-positive isolates. qacG was present in 45 strains, eight of which also harbored smr. No strains carried qacA/B, qacH or qacJ. Presence of smr increased MICs to both BC and CHX and MBCs of CHX, but qacG presence only resulted in elevated MBC for CHX. This is the first report of AR genes from a porcine source. AR gene positivity has previously been associated with methicillin resistance and AR gene presence in these strains may increase their ability to persist in the environment. Improved implementation of hygiene measures during transportation and pre- and post-slaughter should be considered to prevent spread in the community.

Chlorhexidine gluconate reduces transmission of methicillin-resistant Staphylococcus aureus USA300 among Marine recruits

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) pulsed-field type (PFT) USA300 causes skin and soft tissue infections in military recruits and invasive disease in hospitals. Chlorhexidine gluconate (CHG) is used to reduce MRSA colonization and infection. The impact of CHG on the molecular epidemiology of MRSA is not known.

OBJECTIVE

To evaluate the impact of 2% CHG-impregnated cloths on the molecular epidemiology of MRSA colonization.

DESIGN

Cluster-randomized, double-blind, controlled trial.

SETTING

Marine Officer Candidate School, Quantico, Virginia, in 2007.

PARTICIPANTS

Military recruits.

INTERVENTION

Thrice-weekly application of CHG-impregnated or control (Comfort Bath; Sage) cloths over the entire body.

MEASUREMENTS

Baseline and serial (every 2 weeks) nasal and/or axillary swab samples were assessed for MRSA colonization. Molecular analysis was performed with pulsed-field gel electrophoresis.

RESULTS

During training, 77 subjects (4.9%) acquired MRSA, 26 (3.3%) in the CHG group and 51 (6.5%) in the control group (P=.004). When analyzed for PFT, 24 subjects (3.1%) in the control group but only 6 subjects (0.8%) in the CHG group (P=.001) had USA300. Of the 167 colonizing isolates recovered from 77 subjects, 99 were recovered from the control group, including USA300 (40.4%), USA800 (38.4%), USA1000 (12.1%), and USA100 (6.1%), and 68 were recovered from the CHG group, including USA800 (51.5%), USA100 (23.5%), and USA300 (13.2%).

CONCLUSIONS

CHG decreased the transmission of MRSA--more specifically, USA300--among military recruits. In addition, USA300 and USA800 outcompeted other MRSA PFTs at incident colonization. Future studies should evaluate the broad-based use of CHG to decrease transmission of USA300 in hospital settings.

Emergence of resistance to antibacterial agents: the role of quaternary ammonium compounds--a critical review

Quaternary ammonium compounds (QACs) are widely distributed in hospitals, industry and cosmetics. Little attention has been focused on the potential impact of QACs on the emergence of antibiotic resistance in patients and the environment. To assess this issue, we conducted a literature review on QAC chemical structure, fields of application, mechanism of action, susceptibility testing, prevalence, and co- or cross-resistance to antibiotics. Special attention was paid to the effects of QACs on microflora; in particular, the issue of the potential of QACs for applying selective pressure on multiple-antibiotic-resistant organisms was raised. It was found that there is a lack of standardised procedures for interpreting susceptibility test results. QACs have different impacts on the minimum inhibitory concentrations of antibacterials depending on the antibacterial compound investigated, the resistance genes involved, the measuring methodology and the interpretative criteria. The unmet needs for adequate detection of reduced susceptibility to QACs and antibiotics include (i) a consensus definition for resistance, (ii) epidemiological cut-off values and (iii) clinical resistance breakpoints. This review advocates the design of international guidelines for QAC use.

Comparative study with two different enrichments in the culture media used in the disinfectant efficacy assay

Recent changes in Brazilian legislation for commercial disinfectants have been published due to the recent epidemic of nosocomial infections caused by rapidly growing mycobacteria (RGM) in many states of Brazil over the last 8years. One of these documents requires that all the manufacturers provide evidence of efficacy of sterilizing and disinfectant products, used for semi critical medical devices, against the Mycobacterium bovis BCG Moreau and Mycobacterium abscessus subsp. bolletii INCQS 00594 strains by using the Confirmative in vitro Test for Determining Tuberculocidal Activity of Disinfectants recommended by the Association of Official Analytical Chemists. These changes have caused additional costs and increased problems for importation of enrichment products at national laboratories where disinfectant efficacy assay service is performed. Middlebrook ADC Enrichment (ADC) is provided by a unique manufacturer and used in the official protocol. The aim of the present study was to evaluate an alternative in house low-cost enrichment composed of fetal bovine serum and glucose (FBSG) with ADC for performance of disinfectant efficacy assay against mycobacteria. After obtaining the growth curves for M. abscessus ATCC 19977, M. abscessus subsp. bolletii INCQS 00594, Mycobacterium chelonae ATCC 35752, and Mycobacterium fortuitum ATCC 6841 by using ADC enrichment and FBSG in Kirchners and 7H9 culture media. Through statistical analysis via the Kruskal-Wallis test on the evaluation of microorganism growth rate, it was observed that there was no inhibition of RGM growth by any of the enrichments used. These results suggest that low-cost enrichment FBSG may be used as a potential substitute of ADC for composition of media for mycobacterial growth, including in disinfectant tests.

Detection of macrolide and disinfectant resistance genes in clinical Staphylococcus aureus and coagulase-negative staphylococci

Background

Staphylococcus aureus and Coagulase-negative staphylococci (CoNS) are a major source of infections associated with indwelling medical devices. Many antiseptic agents are used in hygienic handwash to prevent nosocomial infections by Staphylococci. Our aim was to determine the antibiotic susceptibility and resistance to quaternary ammonium compound of 46 S. aureus strains and 71 CoNS.

Methods

S. aureus (n = 46) isolated from auricular infection and CoNS (n = 71), 22 of the strains isolated from dialysis fluids and 49 of the strains isolated from needles cultures were investigated. Erythromycin resistance genes (ermA, ermB, ermC, msrA and mef) were analysed by multiplex PCR and disinfectant-resistant genes (qacA, qacB, and qacC) were studied by PCR-RFLP.

Results

The frequency of erythromycin resistance genes in S. aureus was: ermA+ 7.7%, ermB+ 13.7%, ermC+ 6% and msrA+ 10.2%. In addition, the number of positive isolates in CoNS was respectively ermA+ (9.4%), ermB+ (11.1%), ermC+ (27.4%), and msrA+ (41%). The MIC analyses revealed that 88 isolates (74%) were resistant to quaternary ammonium compound-based disinfectant benzalkonium chloride (BC). 56% of the BC-resistant staphylococcus isolates have at least one of the three resistant disinfectants genes (qacA, qacB and qacC). Nine strains (7.7%) among the CoNS species and two S. aureus strains (2%) harboured the three-qac genes. In addition, the qacC were detected in 41 strains.

Conclusions

Multi-resistant strains towards macrolide and disinfectant were recorded. The investigation of antibiotics and antiseptic-resistant CoNS may provide crucial information on the control of nosocomial infections.

Detection of qacA/B in clinical isolates of methicillin-resistant Staphylococcus aureus from a regional healthcare network in the eastern United States

We describe the clinical, microbiologic, and molecular features of the first series of qacA/B-containing strains of methicillin-resistant Staphylococcus aureus from infected US patients. All qac-carrying strains were clonally diverse, and qacA strains exhibited increased tolerance to chlorhexidine as measured by minimum inhibitory concentrations, minimum bactericidal concentrations, and postexposure colony counts.

Distribution of antiseptic resistance genes qacA, qacB, and smr in methicillin-resistant Staphylococcus aureus isolated in Toronto, Canada, from 2005 to 2009

Decreased susceptibility to chlorhexidine gluconate (CHDN) in methicillin-resistant Staphylococcus aureus (MRSA) is associated with the qacA, qacB, and smr genes, encoding efflux pumps. A total of 334 MRSA isolates were collected from two Canadian intensive care units between 2005 and 2009. We identified the qacAB genes in 7 strains (2%; 2 qacA genes and 5 qacB genes) and the smr gene in 23 (7%) strains. CHDN minimal bactericidal concentrations were slightly higher for strains harboring smr genes.