Increasing tolerance of hospital Enterococcus faecium to handwash alcohols.

Alcohol-based disinfectants and particularly hand rubs are a key way to control hospital infections worldwide. Such disinfectants restrict transmission of pathogens, such as multidrug-resistant Staphylococcus aureus and Enterococcus faecium Despite this success, health care infections caused by E. faecium are increasing. We tested alcohol tolerance of 139 hospital isolates of E. faecium obtained between 1997 and 2015 and found that E. faecium isolates after 2010 were 10-fold more tolerant to killing by alcohol than were older isolates. Using a mouse gut colonization model of E. faecium transmission, we showed that alcohol-tolerant E. faecium resisted standard 70% isopropanol surface disinfection, resulting in greater mouse gut colonization compared to alcohol-sensitive E. faecium We next looked for bacterial genomic signatures of adaptation. Alcohol-tolerant E. faecium accumulated mutations in genes involved in carbohydrate uptake and metabolism. Mutagenesis confirmed the roles of these genes in the tolerance of E. faecium to isopropanol. These findings suggest that bacterial adaptation is complicating infection control recommendations, necessitating additional procedures to prevent E. faecium from spreading in hospital settings.

Vancomycin-resistant Enterococcus faecium sequence type 796 - rapid international dissemination of a new epidemic clone.

Background: Vancomycin-resistant Enterococcus faecium (VRE) is a leading cause of hospital-acquired infections. New, presumably better-adapted strains of VRE appear unpredictably; it is uncertain how they spread despite improved infection control. We aimed to investigate the relatedness of a novel sequence type (ST) of vanB E. faecium - ST796 - very near its time of origin from hospitals in three Australian states and New Zealand. Methods: Following near-simultaneous outbreaks of ST796 in multiple institutions, we gathered then tested colonization and bloodstream infection isolates' antimicrobial resistance (AMR) phenotypes, and phylogenomic relationships using whole genome sequencing (WGS). Patient meta-data was explored to trace the spread of ST796. Results: A novel clone of vanB E. faecium (ST796) was first detected at one Australian hospital in late 2011, then in two New Zealand hospitals linked by inter-hospital transfers from separate Melbourne hospitals. ST796 also appeared in hospitals in South Australia and New South Wales and was responsible for at least one major colonization outbreak in a Neonatal Intensive Care Unit without identifiable links between centers. No exceptional AMR was detected in the isolates. While WGS analysis showed very limited diversity at the core genome, consistent with recent emergence of the clone, clustering by institution was observed. Conclusions: Evolution of new E. faecium clones, followed by recognized or unrecognized movement of colonized individuals then rapid intra-institutional cross-transmission best explain the multi-center, multistate and international outbreak we observed.

Superbugs in the supermarket? Assessing the rate of contamination with third-generation cephalosporin-resistant gram-negative bacteria in fresh Australian pork and chicken.

Background: Antibiotic misuse in food-producing animals is potentially associated with human acquisition of multidrug-resistant (MDR; resistance to ≥ 3 drug classes) bacteria via the food chain. We aimed to determine if MDR Gram-negative (GNB) organisms are present in fresh Australian chicken and pork products. Methods: We sampled raw, chicken drumsticks (CD) and pork ribs (PR) from 30 local supermarkets/butchers across Melbourne on two occasions. Specimens were sub-cultured onto selective media for third-generation cephalosporin-resistant (3GCR) GNBs, with species identification and antibiotic susceptibility determined for all unique colonies. Isolates were assessed by PCR for SHV, TEM, CTX-M, AmpC and carbapenemase genes (encoding IMP, VIM, KPC, OXA-48, NDM). Results: From 120 specimens (60 CD, 60 PR), 112 (93%) grew a 3GCR-GNB (n = 164 isolates; 86 CD, 78 PR); common species were Acinetobacter baumannii (37%), Pseudomonas aeruginosa (13%) and Serratia fonticola (12%), but only one E. coli isolate. Fifty-nine (36%) had evidence of 3GCR alone, 93/163 (57%) displayed 3GCR plus resistance to one additional antibiotic class, and 9/163 (6%) were 3GCR plus resistance to two additional classes. Of 158 DNA specimens, all were negative for ESBL/carbapenemase genes, except 23 (15%) which were positive for AmpC, with 22/23 considered to be inherently chromosomal, but the sole E. coli isolate contained a plasmid-mediated CMY-2 AmpC. Conclusions: We found low rates of MDR-GNBs in Australian chicken and pork meat, but potential 3GCR-GNBs are common (93% specimens). Testing programs that only assess for E. coli are likely to severely underestimate the diversity of 3GCR organisms in fresh meat.

Evolutionary origins of the emergent ST796 clone of vancomycin resistant Enterococcus faecium.

From early 2012, a novel clone of vancomycin resistant Enterococcus faecium (assigned the multi locus sequence type ST796) was simultaneously isolated from geographically separate hospitals in south eastern Australia and New Zealand. Here we describe the complete genome sequence of Ef_aus0233, a representative ST796 E. faecium isolate. We used PacBio single molecule real-time sequencing to establish a high quality, fully assembled genome comprising a circular chromosome of 2,888,087 bp and five plasmids. Comparison of Ef_aus0233 to other E. faecium genomes shows Ef_aus0233 is a member of the epidemic hospital-adapted lineage and has evolved from an ST555-like ancestral progenitor by the accumulation or modification of five mosaic plasmids and five putative prophage, acquisition of two cryptic genomic islands, accrued chromosomal single nucleotide polymorphisms and a 80 kb region of recombination, also gaining Tn1549 and Tn916, transposons conferring resistance to vancomycin and tetracycline respectively. The genomic dissection of this new clone presented here underscores the propensity of the hospital E. faecium lineage to change, presumably in response to the specific conditions of hospital and healthcare environments.

High-resolution melting genotyping of Enterococcus faecium based on multilocus sequence typing derived single nucleotide polymorphisms.

We have developed a single nucleotide polymorphism (SNP) nucleated high-resolution melting (HRM) technique to genotype Enterococcus faecium. Eight SNPs were derived from the E. faecium multilocus sequence typing (MLST) database and amplified fragments containing these SNPs were interrogated by HRM. We tested the HRM genotyping scheme on 85 E. faecium bloodstream isolates and compared the results with MLST, pulsed-field gel electrophoresis (PFGE) and an allele specific real-time PCR (AS kinetic PCR) SNP typing method. In silico analysis based on predicted HRM curves according to the G+C content of each fragment for all 567 sequence types (STs) in the MLST database together with empiric data from the 85 isolates demonstrated that HRM analysis resolves E. faecium into 231 "melting types" (MelTs) and provides a Simpson's Index of Diversity (D) of 0.991 with respect to MLST. This is a significant improvement on the AS kinetic PCR SNP typing scheme that resolves 61 SNP types with D of 0.95. The MelTs were concordant with the known ST of the isolates. For the 85 isolates, there were 13 PFGE patterns, 17 STs, 14 MelTs and eight SNP types. There was excellent concordance between PFGE, MLST and MelTs with Adjusted Rand Indices of PFGE to MelT 0.936 and ST to MelT 0.973. In conclusion, this HRM based method appears rapid and reproducible. The results are concordant with MLST and the MLST based population structure.

Evaluation of the Xpert™ MRSA/SA Blood Culture assay for the detection of Staphylococcus aureus including strains with reduced vancomycin susceptibility from blood culture specimens.

The Xpert MRSA/SA Blood Culture (BC) assay (Cepheid, Sunnyvale, CA) was prospectively compared to culture and found to have excellent specificity for both Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) in BC specimens with a sensitivity of 75% (3/4) and 100% (17/17), respectively. Among 28 heterogeneous vancomycin-intermediate S. aureus (hVISA)/VISA spiked BCs, the assay correctly identified 84.6% VISA and 80% hVISA isolates as MRSA.

A sustained hospital outbreak of vancomycin-resistant Enterococcus faecium bacteremia due to emergence of vanB E. faecium sequence type 203.

BACKGROUND: A significant increase in the rate of vancomycin-resistant Enterococcus faecium (VREfm) bacteremia at our health service, despite improved infection control, prompted us to investigate the cause. METHODS: E. faecium bacteremia (including VREfm) over a 12-year period (1998-2009) was investigated using multilocus sequence typing, antibiotic and antiseptic susceptibility profiles, optical mapping, and whole genome sequencing of historical and recent isolates. RESULTS: For 10 years, the rate of bacteremia due to vanB VREfm remained stable and sequence type (ST) 17 was predominant. In 2005, ST203 vancomycin-susceptible E. faecium first appeared at our institution, and from March 2007, coinciding with the appearance of a vanB VREfm ST203, the rate of VRE bacteremia has increased exponentially. Although we found no difference in antiseptic susceptibility or presence of genes encoding putative virulence determinants (esp(Efm), hyl(Efm), and fms genes), comparative genomics revealed almost 500 kb of unique sequence when an ST17 and an ST203 VREfm isolate were compared, suggesting that other genomic factors are responsible for the apparent success of E. faecium. CONCLUSIONS: The application of multilocus sequence typing has uncovered the emergence of an epidemic clone of E. faecium ST203 that appears to have acquired the vanB locus and has caused a sustained outbreak of VRE bacteremia.

Staphylococcus aureus bacteraemia as a quality indicator for hospital infection control.

OBJECTIVE: To evaluate the practicality and effectiveness of a new program that made health care-associated Staphylococcus aureus bacteraemia (SAB) a quality indicator at Austin Health. DESIGN AND SETTING: Roll-out of the program over 9 months and review over 27 months from January 2006. Every episode of SAB at Austin Health was promptly reviewed, and classified as community- or health care-associated and as inpatient- or non-inpatient-related. Feedback was provided to treating clinicians for every SAB episode considered potentially preventable, and education-based interventions were introduced where appropriate. MAIN OUTCOME MEASURE: Episodes of SAB associated with health care at Austin Health per 1000 separations (hospital discharges) per month. RESULTS: We identified 131 episodes of health care-associated SAB, of which 90 (68.7%) were caused by methicillin-susceptible S. aureus, 96 (73.3%) occurred in inpatients, and 65 (49.6%) were associated with a vascular access device. The health care-associated SAB rate was 1.1 per 1000 separations in the first 9 months, and fell by 55% to 0.51 per 1000 separations in the subsequent 18 months. We estimated that there were 80 fewer SAB episodes (95% CI, 20-140) than expected had the initial rate remained unchanged, a national saving of $1.75 million to Austin Health over 27 months. About 16 hours per month of clinical nurse consultant time was required to maintain the program, representing a 0.1 equivalent full-time position, or a cost of $7000-$9000 per year. CONCLUSION: Introducing a structured program to investigate all health care-associated SABs, rather than only infections with methicillin-resistant S. aureus, revealed a large under-recognised burden of potentially preventable infections. The program was simple and low-cost, and the rate of health care-associated SAB has fallen significantly since its introduction.

Concurrent analysis of nose and groin swab specimens by the IDI-MRSA PCR assay is comparable to analysis by individual-specimen PCR and routine culture assays for detection of colonization by methicillin-resistant Staphylococcus aureus.

The IDI-MRSA assay (Infectio Diagnostic, Inc., Sainte-Foy, Quebec, Canada) with the Smart Cycler II rapid DNA amplification system (Cepheid, Sunnyvale, CA) appears to be sensitive and specific for the rapid detection of nasal colonization by methicillin-resistant Staphylococcus aureus (MRSA). We assessed the sensitivity and specificity of this assay under conditions in which both the nose and cutaneous groin specimens were analyzed together and compared the accuracy of this PCR approach to that when these specimens were tested separately and by culture assays in an inpatient population with known high rates (12 to 15%) of MRSA colonization. Of 211 patients screened, 192 had results assessable by all three methods (agar-broth culture, separate nose and groin IDI-MRSA assay, and combined nose-groin IDI-MRSA assay), with MRSA carriage noted in 31/192 (16.1%), 41/192 (21.4%), and 36/192 (18.8%) patients by each method, respectively. Compared to agar culture results, the sensitivity and specificity of the combined nose-groin IDI-MRSA assay were 88.0% and 91.6%, respectively, whereas when each specimen was processed separately, the sensitivities were 90.0% (nose) and 83.3% (groin) and the specificities were 91.7% (nose) and 90.2% (groin). IDI-MRSA assay of a combined nose-groin specimen appears to have an accuracy similar to that of the current recommended PCR protocol, providing results in a clinically useful time frame, and may represent a more cost-effective approach to using this assay for screening for MRSA colonization.

Risk of environmental and healthcare worker contamination with vancomycin-resistant enterococci during outpatient procedures and hemodialysis.

OBJECTIVE: To assess the risk of environmental and healthcare worker (HCW) contamination with vancomycin-resistant enterococci (VRE) during outpatient procedures performed on fecally continent patients currently colonized with VRE (cVRE) or previously colonized with VRE (pVRE). DESIGN: Observational study. SETTING: Outpatient consultation and radiology rooms and the hemodialysis unit in a university teaching hospital. PATIENTS: Fecally continent cVRE and pVRE patients. INTERVENTIONS: Both cVRE and pVRE patients attended standardized mock outpatient consultations and routine hemodialysis sessions in an area that had been thoroughly cleaned and microbiologically confirmed to be free of VRE contamination. After each session, the patient, environment, and participating HCW were tested for VRE contamination. RESULTS: Fourteen cVRE patients participated in 49 mock outpatient consultation sessions and radiology sessions or 26 actual hemodialysis sessions, and 7 pVRE patients participated in 28 outpatient consultation sessions. Sessions with cVRE patients had higher rates of contamination of the environment (chair cultures were positive for VRE in 36% of outpatient consultation sessions, 58% of hemodialysis sessions; couch cultures were positive in 48% of outpatient consultation sessions, 42% of radiology sessions, and 45% of hemodialysis sessions), contamination of HCW gowns (gown cultures were positive in 20% of outpatient consultation sessions, 4% of radiology sessions, and 30% of hemodialysis sessions), and contamination of patients' own hands (hand cultures were positive in 36% of outpatient consultation sessions, 25% of radiology sessions, and 54% of hemodialysis sessions). Overall, contamination rates associated with pVRE patients attendance at outpatient consultations were 12% of those noted for cVRE patients (odds ratio, 0.10; 95% confidence interval, 0.03-0.42; P = .001). CONCLUSIONS: Given the nature of the contamination risk posed by fecally continent cVRE patients undergoing outpatient procedures, infection control measures should focus on effective HCW and patient hand hygiene and chair and couch cleaning, to minimize transmission of VRE.

Efficacy of an alcohol/chlorhexidine hand hygiene program in a hospital with high rates of nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infection.

OBJECTIVE: To assess the effect of a multifaceted hand hygiene culture-change program on health care worker behaviour, and to reduce the burden of nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infections. DESIGN AND SETTING: Timetabled introduction of interventions (alcohol/chlorhexidine hand hygiene solution [ACHRS], improved cleaning of shared ward equipment, targeted patient decolonisation, comprehensive "culture change" package) to five clinical areas of a large university teaching hospital that had high levels of MRSA. MAIN OUTCOME MEASURES: Health care worker hand hygiene compliance; volume of ACHRS used; prevalence of patient and health care worker MRSA colonisation; environmental MRSA contamination; rates of clinical MRSA infection; and rates of laboratory detection of ESBL-producing Escherichia coli and Klebsiella spp. RESULTS: In study wards, health care worker hand hygiene compliance improved from a pre-intervention mean of 21% (95% CI, 20.3%-22.9%) to 42% (95% CI, 40.2%-43.8%) 12 months post-intervention (P < 0.001). ACHRS use increased from 5.7 to 28.6 L/1000 bed-days. No change was observed in patient MRSA colonisation or environmental colonisation/contamination, and, except in the intensive care unit, colonisation of health care workers was unchanged. Thirty-six months post-intervention, there had been significant reductions in hospital-wide rates of total clinical MRSA isolates (40% reduction; P < 0.001), patient-episodes of MRSA bacteraemia (57% reduction; P = 0.01), and clinical isolates of ESBL-producing E. coli and Klebsiella spp (90% reduction; P < 0.001). CONCLUSIONS: Introduction of ACHRS and a detailed culture-change program was effective in improving hand hygiene compliance and reducing nosocomial MRSA infections, despite high-level MRSA endemicity.

In-use efficacy of a chlorhexidine in alcohol surgical rub: a comparative study.

BACKGROUND: Although full surgical scrubs are performed prior to each case on an operating list, optimum regimens for hand cleaning have yet to be determined, and in-use efficacy evaluations are very limited. METHODS: A crossover study was undertaken comparing a chlorhexidine in detergent/alcohol regimen with povidine-iodine detergent scrub, within an orthopaedic operating environment. Depending on the skin asepsis regimen used, five surgical team members scrubbed or rubbed prior to each case for a complete operating list. Bactericidal efficacy was measured using the 'glove-juice' technique before and after hand asepsis, and at the completion of each case. RESULTS: The chlorhexidine regimen caused substantial and sustained reductions in hand bacterial counts (>50-fold prior to case 1) during surgical cases. Application of alcoholic chlorhexidine prior to each subsequent case reduced bacterial counts to the same level as the original scrub. In contrast, the povidine-iodine scrub reduced counts <3-fold prior to the first case and <2-fold in subsequent cases. The chlorhexidine regimen also resulted in persistent bactericidal effects between cases, as counts prior to application of cases 2 and higher were significantly lower than prior to case 1 (>7-fold for case 2 vs case 1). CONCLUSIONS: The chlorhexidine regimen demonstrated excellent bactericidal efficacy throughout an operating list, and was superior to povidine-iodine scrubbing in all aspects. The alcoholic chlorhexidine regimen is simpler and should have wide surgical application.

Treatment outcomes for serious infections caused by methicillin-resistant Staphylococcus aureus with reduced vancomycin susceptibility.

Although infections caused by methicillin-resistant Staphylococcus aureus with reduced vancomycin susceptibility (SA-RVS) have been reported from a number of countries, including Australia, the optimal therapy is unknown. We reviewed the clinical features, therapy, and outcome of 25 patients with serious infections due to SA-RVS in Australia and New Zealand. Eight patients had endocarditis, 9 had bacteremia associated with deep-seated infection, 6 had osteomyelitis or septic arthritis, and 2 had empyema. All patients had received vancomycin before the isolation of SA-RVS, and glycopeptide treatment had failed for 19 patients (76%). Twenty-one patients subsequently received active treatment, which was effective for 16 patients (76%). Eighteen patients received linezolid, which was effective in 14 (78%), including 4 patients with endocarditis. Twelve patients received a combination of rifampicin and fusidic acid. Surgical intervention was required for 15 patients (60%). Antibiotic therapy, especially linezolid with or without rifampicin and fusidic acid, in conjunction with surgical debulking is effective therapy for the majority of patients with serious infections (including endocarditis) caused by SA-RVS.

Risk factors for new detection of vancomycin-resistant enterococci in acute-care hospitals that employ strict infection control procedures.

Accurate assessment of the risk factors for colonization with vancomycin-resistant enterococci (VRE) among high-risk patients is often confounded by nosocomial VRE transmission. We undertook a 15-month prospective cohort study of adults admitted to high-risk units (hematology, renal, transplant, and intensive care) in three teaching hospitals that used identical strict infection control and isolation procedures for VRE to minimize nosocomial spread. Rectal swab specimens for culture were regularly obtained, and the results were compared with patient demographic factors and antibiotic exposure data. Compliance with screening was defined as "optimal" (100% compliance) or "acceptable" (minor protocol violations were allowed, but a negative rectal swab specimen culture was required within 1 week of becoming colonized with VRE). Colonization with VRE was detected in 1.56% (66 of 4,215) of admissions (0.45% at admission and 0.83% after admission; the acquisition time was uncertain for 0.28%), representing 1.91% of patients. No patients developed infection with VRE. The subsequent rate of new acquisition of VRE was 1.4/1,000 patient days. Renal units had the highest rate (3.23/1,000 patient days; 95% confidence interval [CI], 1.54 to 6.77/1,000 patient days). vanB Enterococcus faecium was the most common species (71%), but other species included vanB Enterococcus faecalis (21%), vanA E. faecium (6%), and vanA E. faecalis (2%). The majority of isolates were nonclonal by pulsed-field gel electrophoresis analysis. Multivariate analysis of risk factors in patients with an acceptable screening suggested that being managed by a renal unit (hazard ratio [HR] compared to the results for patients managed in an intensive care unit, 4.6; 95% CI, 1.2 to 17.0 [P = 0.02]) and recent administration of either ticarcillin-clavulanic acid (HR, 3.6; 95% CI, 1.1 to 11.6 [P = 0.03]) or carbapenems (HR, 2.8; 95% CI, 1.0, 8.0 [P = 0.05]), but not vancomycin or broad-spectrum cephalosporins, were associated with acquisition of VRE. The relatively low rates of colonization with VRE, the polyclonal nature of most isolates, and the possible association with the use of broad-spectrum antibiotics are consistent with either the endogenous emergence of VRE or the amplification of previously undetectable colonization with VRE among high-risk patients managed under conditions in which the risk of nosocomial acquisition was minimized.