Rapid increase in the prevalence of antimicrobial drug resistance among enterococcal blood isolates in southern Israel

Genetic diversity of enterococci harboring the high-level gentamicin resistance gene aac(6')-Ie-aph(2'')-Ia or aph(2'')-Ie in a Japanese hospital

Prevalence of high-level gentamicin resistance genes aac(6')-Ie-aph(2'')-Ia and aph(2'')-Ie, which encode distinct aminoglycoside-modifying enzymes, was analyzed for a total of 1128 clinical isolates of enterococci obtained in a Japanese hospital during a period between 1997 and 2007. The aac(6')-Ie-aph(2'')-Ia was detected in 40.1%, 12.9%, and 3.6% of Enterococcus faecalis, E. faecium, and other enterococcal species, respectively, and aph(2'')-Ie was detected in 3.3% of E. faecium. During the study period, detection rate of aac(6')-Ie-aph(2'')-Ia in E. faecium increased from 4% (1997-1998) to 28% (2006-2007), whereas generally constant in E. faecalis. By the analysis of IS256-flanking patterns of aac(6')-Ie-aph(2'')-Ia, truncated forms of Tn5281 lacking IS256 at the 3'-end, 5'-end, and both ends of aac(6')-Ie-aph(2'')-Ia were identified in 4.6%, 32.4%, and 34.2% of E. faecalis strains, respectively, while the composite Tn5281-like element with IS256 at both sides was detected in 28.7% of the strains. A truncated form of Tn5281 lacking IS256 at the 5'-end was predominant in other enterococcal species. Among 14 E. faecalis and 10 E. faecium strains harboring aac(6')-Ie-aph(2'')-Ia, 8 and 6 different sequence types (STs) were identified by multilocus sequence typing, respectively. Some E. faecalis STs (ST4, ST16, ST64, and ST223) were found in more than one strain, and ST4 and ST64 were associated with different IS256-flanking patterns. STs of five among six E. faecium strains with aac(6')-Ie-aph(2'')-Ia (ST78, ST203, and ST418) belonged to the clonal complex (CC)17, which is known as globally emerging lineage of vancomycin- or ampicillin-resistant E. faecium clones. E. faecium strains with aph(2'')-Ie were classified into newly assigned STs, ST426, and its single locus variant ST427, which also belonged to CC17. Therefore, it was suggested that E. faecium of CC17 is prone to acquire high-level gentamicin resistance genes, and aph(2'')-Ie is distributed to specific E. faecium clones that are distinct from those having aac(6')-Ie-aph(2'')-Ia.

Acquisition of vancomycin-resistant enterococci in internal medicine wards

BACKGROUND

Our institution experienced an increase in the frequency of vancomycin-resistant enterococci (VRE) clinical isolates, which rose 5-fold from 2004 to 2005. We sought to measure the prevalence of VRE carriage among medical inpatients in a tertiary hospital in Jerusalem and estimate the rate of acquisition during hospitalization.

METHODS

During 2006, we performed 3 cross-sectional surveys, including 1039 patients, representing 3 phases of hospitalization: admission, hospital stay, and discharge. Perianal/stool samples were cultured for VRE.

RESULTS

VRE carriage was 3.8% (95% confidence interval [CI] = 1.8% to 6.9%) on admission, 15% (95% CI = 9% to 23%) at discharge, and 32% (95% CI = 24% to 40%) among inpatients. Among inpatient carriers, 60% of the isolates represented a single strain. Recent previous hospitalization was the most significant predictor for identifying carriers on admission.

CONCLUSIONS

Our study demonstrates that substantial VRE transmission occurred during hospitalization. Identification of carriers on admission should supplement effective application of infection control methods in attempting to decrease VRE nosocomial spread and burden.

Antimicrobial resistance of enterococci in Turkey

Susceptibility to ampicillin, penicillin, vancomycin and teicoplanin, high-level resistance to aminoglycosides (gentamicin and streptomycin) and beta-lactamase production were investigated among 264 consecutive clinical enterococcal isolates in Turkey. Disc diffusion test was used to detect resistance to ampicillin, penicillin, vancomycin and teicoplanin. High-level resistance to aminoglycosides was determined both by standard agar screening and by disc diffusion methods. The values of minimum inhibitory concentration (MIC) of each isolate for ampicillin, vancomycin and teicoplanin were determined by the microbroth dilution technique. The isolates were found to consist of Enterococcus faecalis (78%), Enterococcus faecium (9%) and Enterococcus spp. (12%). In all strains, the penicillin and ampicillin resistance ratios were 27% and 26%, respectively. Enterococcus faecalis was more susceptible to penicillin and ampicillin than the other strains. None of the strains were resistant to glycopeptides. High-level aminoglycoside resistance was found in 16% E. faecalis and 88% E. faecium for gentamicin, and 35% and 44%, respectively, for streptomycin. There were no differences between the two methods used to determine the aminoglycoside resistance rates in the enterococcal isolates. No beta-lactamase-producing isolates were detected in either species. In conclusion, to determine the resistance of enterococci to the penicillin group of drugs by the disc diffusion method, both penicillin and ampicillin discs should be evaluated. In serious enterococcal infections, before starting combined therapy, high-level aminoglycoside resistance should be investigated.

Microbiological and epidemiological studies of Enterococcus faecium resistant to amoxycillin in a university hospital in eastern France

Over 3 years, during six 1-month periods of surveillance, 69 cases of Enterococcus faecium colonisation or infection were detected in a university hospital in eastern France. Thirty-two cases involved strains resistant to amoxycillin (crude incidence of 0.21/1000 patient-days). The risk of infection with E. faecium was higher if the patient was hospitalised in a haematology ward and/or treated with cephalosporins. Amoxycillin-resistant isolates (AmRE) were isolated from different wards and time periods, and none of the characteristics studied were associated significantly with amoxycillin resistance. Amoxycillin-sensitive and -resistant isolates were characterised by pulsed-field gel electrophoresis. Three epidemic patterns were identified which contained 87.5% (28/32) of the AmRE isolates, indicating that clonal spread was responsible, at least partially, for the high incidence of AmRE in this hospital.

Vancomycin-resistant Enterococcus faecalis colonization during recovery from Neisseria meningitidis cerebrospinal meningitis. Case report

A 19-year-old man had been admitted to the Hospital because of septic shock and large scale suffusions all over the body. The pathogen had proved to be Neisseria meningitidis serogroup C. In his stabilization period two superinfectious attacks arose. One of them was a bacteremia, caused by a vancomycin-sensitive Enterococcus faecium. The second was a wound infection in his deep colliquating necrotised tissue of the heel. Vancomycin-resistant Enterococcus faecalis (VREF) was isolated from this lesion with some Gram-negative opportunistic pathogens. The strain contained the vanA gene. After systemic and topical treatment, furthermore plastic surgical interventions the patient recovered. This is the second report on VREF from Hungary colonizing/infecting a patient with an underlying disease.

A comparison of high-level aminoglycoside resistance in vancomycin-sensitive and vancomycin-resistant Enterococcus species

The aim of this study was to investigate whether there was a significant difference in high-level aminoglycoside resistance (HLAR) between vancomycin-sensitive enterococci (VSE) and vancomycin-resistant enterococci (VRE). Vancomycin resistance was determined in 116 Enterococcus isolates using brain-heart infusion agar containing 6 micrograms/ml vancomycin. HLAR was determined by both standard agar screening and disk diffusion methods. Streptomycin and gentamicin were used as predictors of HLAR. Vancomycin resistance and HLAR were found in 17 (14.7%) and 41 (35.3%) of the Enterococcus strains, respectively. HLAR was found in 11 of 17 VRE and 30 of 98 VSE strains. HLAR in VRE strains was significantly higher than in VSE. More enterococcal strains were found to be resistant to both gentamicin and streptomycin (29) than to gentamicin (one) or streptomycin (11) alone. The HLAR rate in VRE was two-fold higher than in VSE. The synergistic bactericidal effect of aminoglycosides and beta-lactam or glycopeptide antibiotics is lost if there is high-level resistance to aminoglycosides.

Evaluation of a biochemical test scheme for identifying clinical isolates of Enterococcus faecalis and Enterococcus faecium

AIMS

To evaluate the full test scheme of Facklam and Sahm (1995) for the identification of clinical enterococcal isolates to genus and species level.

METHODS AND RESULTS

Fifty-nine clinical isolates, previously provisionally classed as enterococci on the basis of just four biochemical tests of Facklam and Sahm and one other test, were subjected to genus and species identification using the full identification scheme of Facklam and Sahm; 98% of these strains were confirmed to be enterococci and of these, 69% were identified as Enterococcus faecalis and 31% as Enterococcus faecium. Six tests in the scheme (out of 24) gave anomalous or unreliable results for some strains, and two gave unexpected results for the majority of strains presumptively identified as Ent. faecium.

CONCLUSIONS

Nine (out of 12) genus tests and nine (out of 12) species tests from the Facklam and Sahm scheme were reliable. Testing for the presence of the Lancefield antigen D was also useful. The majority of presumptive Ent. faecium strains gave different results for the sorbitol and raffinose tests from that expected.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study indicates the level of reliability for each of the tests in a current enterococcal identification scheme for differentiating clinical isolates, and showed that two tests gave consistently different test results from those expected for Ent. faecium.

[Risk factors and prevention of the acquisition and transmission of glycopeptide resistant enterococci]

We reviewed the literature concerning the role of antibiotic use as a risk factor for glycopeptide-resistant enterococci (VRE) infection/colonisation, to enable us to develop measures for preventing the acquisition and transmission of VRE. We found that the length of stay, the number of stays in hospital and the transfer of patients between hospitals and units were all risk factors for acquiring VRE infection. However, analysis of group and individual data showed that there was also a clear link between vancomycin and third-generation cephalosporin use and the prevalence of VRE colonisation/infection. Evidence for this link was provided by the consistent association and dose-effect relationship observed, and from the frequently consistent variations observed over time. However, it is difficult to give precise recommendations because very few studies have investigated both intrinsic bacterial factors making specific strains more epidemic and the precise characteristics of the conditions determining antibiotic selection pressure. In the absence of this information, and maintaining the prevention measures against cross-contamination which remain a priority, these results suggest that programs aimed at improving the prescription of antibiotics should be initiated in hospitals.

Antimicrobial resistance of Enterococci in Lebanon

There is little information on the types of Enterococcus spp and their antibiotic resistance patterns in Lebanon. One hundred and fifty-three consecutive clinical enterococcal isolates collected between 1998 and 1999 were tested against 11 antimicrobial agents using disk diffusion and the Etest. The isolates were identified by conventional methods and API-Strep and were found to consist of Enterococcus faecalis (72.5%), Enterococcus faecium (22.9%), Enterococcus avium (3.2%) and Enterococcus gallinarum (1.3%). The percent of resistant strains of E. faecalis and E. faecium respectively were, ampicillin 0.9 and 14%, erythromycin 59% and 40%, tetracycline 72% and 34%, chloramphenicol 32 and 11%, rifampin 36% and 57%, ciprofloxacin, 23% and 34%, norfloxacin 22 and 8%. High level aminoglycoside (HLA) resistance was found in 19% E. faecalis and 9% E. faecium for gentamicin and 36% and 26% for streptomycin. Excellent correlation was observed between the high level disk tests and the Etest in the detection of HLA resistance but not with the regular disks. None of the isolates showed resistance to vancomycin or teicoplanin except for one E. gallinarum isolate which showed intermediate resistance (MIC 16 mg/l) to vancomycin. These variable antimicrobial rates of resistance suggest a surveillance programme for antimicrobial resistance in this country would be helpful to help control infection, guide empirical antibiotic therapy and implement a policy of antibiotic usage.

Evaluation of chlorhexidine and povidone iodine activity against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis using a surface test

Most published studies of the activity of biocides against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) have been based on suspension tests. This study was undertaken to provide information on the effect of chlorhexidine and povidone iodine on bacteria dried on to surfaces, a situation in which biocide activity is known to be reduced. The inactivation of MRSA (10 strains), methicillin-sensitive Staphylococcus aureus (MSSA, 10 strains), VRE (nine strains) and vancomycin-sensitive Enterococcus faecalis (VSE, 10 strains) by 0.5% aqueous chlorhexidine gluconate or 10% povidone iodine was evaluated by applying the European surface test method. Povidone iodine was equally active against resistant and sensitive strains of both species with microbicidal effects (ME), i.e. the log(10)concentration of micro-organisms compared with controls treated with distilled water, after 1.5 min of 3.14 and 3.49 for VRE and VSE respectively, and 3.47 and 3.78 for MRSA and MSSA. Chlorhexidine was equally active against VRE and VSE (ME 3.37 vs. 3. 56 after 7 min, respectively), but was significantly less active against MRSA as opposed to MSSA (ME 3.07 vs. 3.83 after 10 min, P= 0. 017).

Epidemiology of glycopeptide-resistant enterococci colonizing high-risk patients in hospitals in Johannesburg, Republic of South Africa

Recent cases of infections caused by glycopeptide-resistant enterococci (GRE) have highlighted the emergence of these organisms in the Republic of South Africa. During May 1998 we conducted a prevalence study in four hospitals in Johannesburg and obtained 184 rectal swabs from patients identified as being at high risk for GRE colonization. Twenty enterococcal isolates showing various glycopeptide resistance genotypes were recovered: 3 Enterococcus faecium vanA isolates, 10 E. faecium vanB isolates, 6 E. gallinarum vanC1 isolates, and 1 E. avium vanA isolate. Macrorestriction analysis was used to demonstrate the clonal spread of GRE strains within hospitals. Evidence also demonstrated the likely persistence of the original E. faecium vanA isolate associated with the first confirmed death contributed to by GRE infection in South Africa in March 1997.