Antimicrobial susceptibility patterns of enterococci causing infections in Europe. The European VRE Study Group

Clinical Features and Genomic Epidemiology of Bloodstream Infections due to Enterococcal Species Other Than Enterococcus faecalis or E. faecium in Patients With Cancer

Background

Non-Enterococcus faecium, non-E. faecalis (NFF) enterococci are a heterogeneous group of clinically pathogenic enterococci that include species with intrinsic low-level vancomycin resistance. Patients with cancer are at increased risk for bacteremia with NFF enterococci, but their clinical and molecular epidemiology have not been extensively described.

Methods

We conducted a retrospective review of all patients (n = 70) with NFF bacteremia from 2016 to 2022 at a major cancer center. The main outcomes assessed were 30-day mortality, microbiological failure (positive blood cultures for ≥4 days), and recurrence of bacteremia (positive blood culture <14 days after clearance). Whole-genome sequencing was performed on all available NFF (n = 65).

Results

Patients with hematological malignancies made up 56% of the cohort (77% had leukemia). The majority of solid malignancies (87%) were gastrointestinal in origin. The majority of infections (83%) originated from an intra-abdominal source. The most common NFF species were E. gallinarum (50%) and E. casseliflavus (30%). Most (61%) patients received combination therapy. Bacteremia recurred in 4.3% of patients, there was a 30-day mortality of 23%, and 4.3% had microbiological failure. E. gallinarum and E. casseliflavus isolates were genetically diverse with no spatiotemporal clustering to suggest a single strain. Frequencies of ampicillin resistance (4.3%) and daptomycin resistance (1.9%) were low. Patients with hematologic malignancy had infections with NFF enterococci that harbored more resistance genes than patients with solid malignancy (P = .005).

Conclusions

NFF bacteremia is caused by a heterogeneous population of isolates and is associated with significant mortality. Hematological malignancy is an important risk factor for infection with NFF resistant to multiple antibiotics.

Antimicrobial resistance of Escherichia coli, Enterobacter spp., Klebsiella pneumoniae and Enterococcus spp. isolated from the feces of giant panda

Background

Escherichia coli, Enterobacter spp., Klebsiella pneumoniae and Enterococcus spp., common gut bacteria in giant pandas, include opportunistic pathogens. The giant panda is an endangered species, classified as vulnerable by the World Wildlife Foundation. Continuous monitoring for the emergence of antimicrobial resistance (AMR) among bacterial isolates from giant pandas is vital not only for their protection but also for public health.

Results

A total of 166 E. coli, 68 Enterobacter spp., 116 K. pneumoniae and 117 Enterococcus spp. isolates were collected from fecal samples of 166 giant pandas. In the antimicrobial susceptibility tests, 144 E. coli isolates, 66 Enterobacter spp. isolates, 110 K. pneumoniae isolates and 43 Enterococcus spp. isolates were resistant to at least one antimicrobial. The resistant isolates carried antimicrobial resistance genes (ARGs), including sul3, bla_TEM, bla_SHV and tetA. The differences in the prevalence of the bla types implied that the genetic basis for β-lactam resistance among the E. coli, Enterobacter spp. and K. pneumoniae isolates was different. The strain K. pneumoniae K85 that was resistant to sixteen antimicrobials was selected for whole genome sequencing. The genome contained Col440I, IncFIB_K and IncFII_K plasmids and altogether 258 ARGs were predicted in the genome; 179 of the predicted ARGs were efflux pump genes. The genetic environment of the β-lactamase genes bla_CTX-M-3 and bla_TEM-1 in the K. pneumoniae K85 genome was relatively similar to those in other sequenced K. pneumoniae genomes. In comparing the giant panda age groups, the differences in the resistance rates among E. coli, K. pneumoniae and Enterobacter spp. isolates suggested that the infections in giant pandas of different age should be treated differently.

Conclusions

Antimicrobial resistance was prevalent in the bacterial isolates from the giant pandas, implying that the gut bacteria may pose serious health risks for captive giant pandas. The resistance genes in the genome of K. pneumoniae K85 were associated with insertion sequences and integron-integrase genes, implying a potential for the further spread of the antimicrobial resistance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02514-0.

Successful treatment of aortic valve endocarditis caused by Enterococcus casseliflavus: a case report

Background

Enterococcus casseliflavus is rarely isolated from human specimens. To the best of our knowledge, there are no reports on its detailed treatment course and prognosis. Here, we present the first known case of E. casseliflavus endocarditis with a detailed treatment course.

Case presentation

An 86-year-old Japanese woman was transferred to the emergency department with dyspnoea, wheezing, and lumbago. Her medical history included hypertension, chronic kidney disease, idiopathic interstitial pneumonia, and rectal carcinoma. Physical examination revealed expiratory wheezes and a diastolic murmur (Levine 2/6) at the 4th right sternal border. Chest radiography revealed bilateral interstitial opacities and slight cardiac dilatation. Transthoracic echocardiography demonstrated the presence of mobile vegetation with perforation, prolapse, and regurgitation of the aortic valve. With a suspicion of infective endocarditis, we started administering intravenous ampicillin/sulbactam. Thereafter, blood cultures identified E. casseliflavus through matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. The antimicrobial treatment was then switched to ampicillin plus gentamicin. The patient underwent aortic valve replacement on the thirteenth hospital day. She was administered intravenous ampicillin and gentamicin for 6 weeks. The patient was discharged 8 weeks after admission.

Conclusions

Our case demonstrated that E. casseliflavus could cause infective endocarditis, which can be successfully treated with a 6-week regimen of ampicillin and gentamicin in combination with proper surgical treatment.

Biotyping and Antimicrobial Susceptibility of Enterococcus faecalis and E. faecium Isolated from Urine and Stool Samples

Background: Enterococci are one of the opportunistic pathogenic microorganisms that can cause significant problems for human and animal health. Enterococcus faecium seems to be more resistant to antibiotics than E. faecalis. It is thought that pathogenic E. faecium can develop antibiotic resistance very quickly, and the ability to transfer this feature is considered to be an important health risk. Objectives: This study aimed to determine the prevalence, biotypes, and in vitro antimicrobial susceptibility of E. faecalis and E. faecium strains isolated from 267 routine urine and stool samples that were brought to the microbiology laboratory of Regional Training and Research Hospital of Van, with permission of the patients. Methods: In the present study, enterococci using species-specific primers to examine E. faecalis and E. faecium multiplex PCR technique was applied. Biotyping of the isolates was used to identify them as E. faecalis and E. faecium by molecular techniques, and antibiotic susceptibility of all samples was examined, as well. Results: The isolates were identified by multiplex PCR using species-specific primers for E. faecalis and E. faecium. Biotyping based on 13 biochemical tests showed that 72.5%, 12.5%, and 15% of E. faecalis strains were of biotypes I, II, and III, respectively, whereas E. faecium strains could be divided into biotype I (10%), biotype II (12.5%), biotype III (27.5%), and biotype IV (50%). Additionally, all E. faecalis strains were found to be susceptible to penicillin G and imipenem. On the other hand, 95% of the E. faecalis strains were found to be resistant to clindamycin, 77.5% to tetracycline and trimethoprim/sulfamethoxazole, 42.5% to erythromycin, 32.5% to gentamicin, and 17.5% to ciprofloxacin. Of E. faecium strains, 37.5% were found to be resistant to clindamycin, 32.5% to penicillin G, 27.5% to erythromycin and imipenem, 20% to ciprofloxacin, 17.5% to tetracycline and trimethoprim/sulfamethoxazole, 15% to gentamicin, and 5% to vancomycin. Conclusions: In conclusion, the identification of E. faecalis and E. faecium strains by PCR is reliable and faster than biochemical tests. Additionally, the results of antimicrobial susceptibility tests may provide important contributions to the clinical approach.

Urban and agricultural soils in Southern California are a reservoir of carbapenem-resistant bacteria

Carbapenems are last‐resort β‐lactam antibiotics used in healthcare facilities to treat multidrug‐resistant infections. Thus, most studies on identifying and characterizing carbapenem‐resistant bacteria (CRB) have focused on clinical settings. Relatively, little is still known about the distribution and characteristics of CRBs in the environment, and the role of soil as a potential reservoir of CRB in the United States remains unknown. Here, we have surveyed 11 soil samples from 9 different urban or agricultural locations in the Los Angeles–Southern California area to determine the prevalence and characteristics of CRB in these soils. All samples tested contained CRB with a frequency of <10 to 1.3 × 10⁴ cfu per gram of soil, with most agricultural soil samples having a much higher relative frequency of CRB than urban soil samples. Identification and characterization of 40 CRB from these soil samples revealed that most of them were members of the genera Cupriavidus, Pseudomonas, and Stenotrophomonas. Other less prevalent genera identified among our isolated CRB, especially from agricultural soils, included the genera Enterococcus, Bradyrhizobium, Achromobacter, and Planomicrobium. Interestingly, all of these carbapenem‐resistant isolates were also intermediate or resistant to at least 1 noncarbapenem antibiotic. Further characterization of our isolated CRB revealed that 11 Stenotrophomonas, 3 Pseudomonas, 1 Enterococcus, and 1 Bradyrhizobium isolates were carbapenemase producers. Our findings show for the first time that both urban and agricultural soils in Southern California are an underappreciated reservoir of bacteria resistant to carbapenems and other antibiotics, including carbapenemase‐producing CRB.

Antibiotic Resistance and Virulence Traits in Vancomycin-Resistant Enterococci (VRE) and Extended-Spectrum β-Lactamase/AmpC-producing (ESBL/AmpC) Enterobacteriaceae from Humans and Pets

BACKGROUND

We investigated the virulence factors, genes, antibiotic resistance patterns, and genotypes (VRE and ESBL/AmpC) production in Enterococci and Enterobacteriaceae strains isolated from fecal samples of humans, dogs, and cats.

METHODS

A total of 100 fecal samples from 50 humans, 25 dogs, and 25 cats were used in the study. MICs of nine antimicrobials were determined using the broth microdilution method. Polymerase chain reaction was used for the detection of genes responsible for antibiotic resistance (VRE and ESBL/AmpC) and virulence genes both in Enterococcus species, such as cytolysin (cylA, cylB, cylM), aggregation substance (agg), gelatinase (gelE), enterococcal surface protein (esp), cell wall adhesins (efaAfs and efaAfm), and in Enterobacteriaceae, such as cytolysin (hemolysin) and gelatinase production (afa, cdt, cnf1, hlyA, iutA, papC, sfa).

RESULTS

Enterococcus faecium was the most prevalent species in humans and cats, whereas Enterococcus faecalis was the species isolated in the remaining samples. A total of 200 Enterobacteriaceae strains were also detected, mainly from humans, and Escherichia coli was the most frequently isolated species in all types of samples. In the Enterococcus spp, the highest percentages of resistance for ampicillin, amoxicillin/clavulanate, erythromycin, tetracycline, ciprofloxacin, teicoplanin, and vancomycin were detected in cat isolates (41.6%, 52.8%, 38.9%, 23.6%, 62.5%, 20.8%, and 23.6% respectively), and in E. coli, a higher rate of resistance to cefotaxime and ceftazidime emerged in cat and dog samples, if compared with humans (75.4% and 66.0%, 80.0% and 71.4%, and 32.0% and 27.2%, respectively). Regarding the total number of enterococci, 5% and 3.4% of the strains were vancomycin and teicoplanin resistant, and the vancomycin resistance (van A) gene has been detected in all samples by PCR amplification. All the Enterobacteriaceae strains were confirmed as ESBL producers by PCR and sequencing, and the most frequent ESBL genes in E.coli strains from humans and pet samples were blaCTX-M-1 and blaCTX-M-15.

CONCLUSIONS

Our results provide evidence that one or more virulence factors were present in both genera, underlining again the ability of pet strains to act as pathogens.

High Level Aminoglycoside Resistance And Distribution Of The Resistance Genes In Enterococcus faecalis And Enterococcus faecium From Teaching Hospital In Malaysia

Background

Enterococcus faecium and Enterococcus faecalis are among the predominant species causing hospital-acquired infections. Currently, enterococcal infections are treated using combination therapy of an aminoglycoside with cell-wall active agents, which led to high level aminoglycoside resistance (HLAR) and vancomycin resistance (VRE) among enterococci. The aim of this study was to determine the prevalence of HLAR and the distribution of the resistance genes among clinical E. faecalis and E. faecium isolates in Malaysia.

Materials and methods

Seventy-five enterococci isolates recovered from different clinical sources were re-identified by subculturing on selective medium, Gram staining, biochemical profiling (API 20 Strep), and 16s rRNA sequencing. Antimicrobial susceptibility testing (AST) was performed using Kirby-Bauer disc diffusion, E-test, and broth microdilution methods. PCR amplification was used to detect the presence of aminoglycoside modifying enzyme (AME) genes [aac(6')-Ie-aph(2")-Ia, aph(2")-Ib, aph(2")-Ic, aph(2")-Id, aph(3')-IIIa]. Descriptive data analysis was used to analyze the antibiotic susceptibility profiles and the distribution of HLAR genes.

Results

The majority of the isolates recovered from the clinical samples are E. faecalis (66.7%), with the highest recovery from the pus. The prevalence of HLGR (51%) is higher when compared to HLSR (45-49%). Analysis of the resistance genes showed that bifunctional genes aac(6')-Ie-aph(2")-Ia and aph(3')-IIIa contributed to the HLAR E. faecalis and E. faecium. The other AME genes [aph(2")-Ib, aph(2")-Ic, aph(2")-Id] were not detected in this study.

Conclusion

This study provides the first prevalence data on HLAR and the distribution of the AME genes among E. faecalis and E. faecium isolates from Malaysia. These highlight the need for continued antibiotic surveillance to minimize its emergence and further dissemination.

High-level aminoglycoside resistance and distribution of aminoglycoside resistance genes among Enterococcus spp. clinical isolates in Tehran, Iran

OBJECTIVES

Enterococci have gained attention during the past decade as important nosocomial pathogens. Their increasing prevalence has been paralleled by the occurrence of multidrug-resistant and high-level aminoglycoside-resistant strains. This study isolated Enterococcus spp. from hospital samples and determined their antibiotic resistance profile, focusing on aminoglycosides, and associated resistance mechanisms.

METHODS

A total of 195 enterococci from hospital samples in Tehran were studied. Isolates were identified by biochemical reactions. Antimicrobial resistance was determined by disk diffusion. The vancomycin MIC for vancomycin-resistant isolates was determined by agar dilution. Detection of aminoglycoside resistance genes and intI1 and intI2 gene was performed by PCR.

RESULTS

The majority of isolates were Enterococcus faecalis (65.1%), followed by Enterococcus faecium (31.8%), Enterococcus gallinarum (2.6%) and Enterococcus solitarius (0.5%). According to antibiogram results, 42.1% of isolates were high-level gentamicin-resistant (HLGR) and 40.5% were high-level streptomycin-resistant (HLSR). There was a high prevalence of aac(6')-Ie-aph(2")-Ia (96.3%) among HLGR isolates. ant(6)-Ia and aadA were identified in 93.7% and 64.6% of HLSR isolates, respectively. aph(2'')-Ic was detected in 7 isolates (3.6%) and aph(2'')-Ib in only 4 isolates (2.1%); no isolates harboured aph(2'')-Id, intI1 or intI2.

CONCLUSION

Multidrug resistance was higher among HLGR and HLSR isolates compared with non-HLGR and non-HLSR isolates, which may result in limited treatment options. More than 50% of isolates were susceptible to aminoglycosides, thus correct identification in clinical laboratories and administration of these antibiotics can result in decreased used of antibiotics such as vancomycin and linezolid and help to reduce the emergence of resistance to these drugs.

High Prevalence of the aac(6')-Ie-aph(2'')-Ia Gene in Hospital Isolates of Enterococcus faecalis Co-Resistant to Gentamicin and Penicillin

Objectives: This study aimed to characterize the molecular mechanism of resistance to gentamicin among penicillin-resistant, ampicillin-susceptible Enterococcus faecalis (PRASEF) isolates by investigating the presence of the aac(6')-Ie-aph(2'')-Ia gene. The co-resistance to antimicrobials of other classes was also evaluated. Results: Among the 151 isolates evaluated, 70 were PRASEF and 81 were penicillin-susceptible and ampicillin-susceptible E. faecalis (PSASEF). No β-lactamase producing isolate was detected. Eighty-three (55.0%) and 35 (23.2%) out of the 151 E. faecalis isolates showed high-level gentamicin resistance (HLGR) and high-level streptomycin resistance (HLSR) phenotypes. However, a significantly higher rate of PRASEF (88.6%) showed HLGR phenotype in comparison with PSASEF (23.5%) (p < 0.01). Conversely, a significantly lower rate of PRASEF (14.3%) showing HLSR was observed in comparison with PSASEF (30.9%) (p = 0.02). The prevalence of isolates displaying multidrug resistance (MDR) phenotype was significantly higher (p < 0.01) in the group of PRASEF (81.4%) than in PSASEF (18.6%). The majority of PSASEF (61.9%) and PRASEF (90.3%) isolates showing HLGR phenotype was harboring the aac(6')-Ie-aph(2'')-Ia gene, which encodes a bifunctional enzyme that inactivates all aminoglycosides except streptomycin. Conclusion: The aac(6')-Ie-aph(2'')-Ia gene was prevalent among the Brazilian PRASEF isolates that usually exhibit co-resistance to gentamicin and to multiple other drugs.

Antimicrobial Resistance of Enterococcus Faecium Isolated from the Urinary System Of Dogs

The purpose of the present study was to determine the antimicrobial susceptibility of vancomycin-resistant and Enterococcus faecium strains isolated from urine samples of dogs. A total of 22 Enterococcus sp. samples were isolated and identified from 100 urine samples collected by cystocentesis from dogs of both sexes. The identification with species specific primers for multiplex PCR revealed that all 22 isolates (100%) belonged to E. faecium. Vancomycin resistance was found in 10 (45%) samples of E. faecium strains with PCR study by vanA and vanB primers.

High level aminoglycoside resistant enterococci in hospital-acquired urinary tract infections in Mansoura, Egypt

Introduction

Resistance to different antimicrobial agents is increasing in enterococci and effective treatment represents a major health concern. The aim of this study was to determine the antimicrobial resistance patterns and the frequency of high level aminoglycoside resistance (HLAR) among enterococci.

Methods

A total of 80 enterococcal isolates, (73 Enterococcus faecalis, 7 Enterococcus faecium) were collected from patients with hospital acquired urinary tract infections (UTI) at Mansoura University hospitals in Egypt. Antimicrobial susceptibility testing was performed via the disc diffusion method. PCR was used for identification of species and detection of aminoglycoside-modifying enzymes genes (AME).

Results

All enterococcal isolates were sensitive to vancomycin and linezolid. Fifty-three isolates exhibited HLAR. Our results show that HLAR was mediated by the presence of multiple AMEs genes. The aac(6')-Ie-aph(2')-Ia gene was associated with aph(3')-IIIa and ant(6)-Ia gene in 69% of HLAR isolates.

Conclusion

This study showed that enterococci isolated from hospital acquired UTI were resistant to multiple antibiotics. Furthermore, the frequency of high level gentamicin resistance (HLGR) was higher than high level of streptomycin resistance (HLSR). The most common AME genes were aph(3')-IIIa and ant(6)-Ia followed by aac(6')-Ie-aph(2')-Ia.

In Vivo and In Vitro Effects of a ClpP-Activating Antibiotic against Vancomycin-Resistant Enterococci

Antibiotics with novel bactericidal mechanisms of action are urgently needed. The antibiotic acyldepsipeptide 4 (ADEP4) activates the ClpP protease and causes cells to self-digest. The effects of ADEP4 and ClpP activation have not been characterized sufficiently for the enterococci, which are important pathogens known for high levels of acquired and intrinsic antibiotic resistance. In the present study, ADEP4 was found to be potently active against both Enterococcus faecalis and Enterococcus faecium, with MIC₉₀s of 0.016 μg/ml and 0.031 μg/ml, respectively. ClpP purified from E. faecium was found to bind ADEP4 in a surface plasmon resonance analysis, and ClpP activation by ADEP4 was demonstrated biochemically with a β-casein digestion assay. In addition, E. faecium ClpP was crystallized in the presence of ADEP4, revealing ADEP4 binding to ClpP in the activated state. These results confirm that the anti-enterococcal activity of ADEP4 occurs through ClpP activation. In killing curve assays, ADEP4 was found to be bactericidal against stationary-phase vancomycin-resistant E. faecalis (VRE) strain V583, and resistance development was prevented when ADEP4 was combined with multiple classes of approved antibiotics. ADEP4 in combination with partnering antibiotics also eradicated mature VRE biofilms within 72 h of treatment. Biofilm killing with ADEP4 antibiotic combinations was superior to that with the clinically used combinations ampicillin-gentamicin and ampicillin-daptomycin. In a murine peritoneal septicemia model, ADEP4 alone was as effective as ampicillin. ADEP4 coadministered with ampicillin was significantly more effective than either drug alone. These data suggest that ClpP-activating antibiotics may be useful for treating enterococcal infections.

Clinical management of non-faecium non-faecalis vancomycin-resistant enterococci infection. Focus on Enterococcus gallinarum and Enterococcus casseliflavus/flavescens

Enterococcus gallinarum and Enterococcus casseliflavus/flavescens are enterococci intrinsically resistant to vancomycin belonging to the E. gallinarum group. They are responsible mainly for healthcare-associated infections, in particular bloodstream, urinary tract and surgical wound infections. Diseases due to these bacteria are significantly increasing worldwide, as they are prone to cause infection in patients with concurrent hepatobiliary or oncohematological disorders. Along with their distinguishing vancomycin resistance, due to a chromosomally-encoded VanC operon, their additional intrinsic resistance to many antibiotics other than glycopeptides limits the therapeutic choices. In addition, their intrinsic vancomycin resistance, unlike the vancomycin resistance of Enterococcus faecalis and Enterococcus faecium caused by transmissible plasmids, poses different infection control issues. We focused on the therapeutic and infection control issues of clinical syndromes caused by E. gallinarum and E. casseliflavus/flavescens. We propose therapeutic algorithms on bloodstream infections, endocarditis, central nervous system infections, endophthalmitis and urinary tract infections. The implementation of infection control measures in cases of E. gallinarum and E. casseliflavus/flavescens infection or colonization should be evaluated on a case-by-case basis, especially for epidemic outbreaks or for isolates supposed to harbor a potential transmissible vancomycin-resistance phenotype.

Characterization of Multi-Drug Resistant Enterococcus faecalis Isolated from Cephalic Recording Chambers in Research Macaques (Macaca spp.)

Nonhuman primates are commonly used for cognitive neuroscience research and often surgically implanted with cephalic recording chambers for electrophysiological recording. Aerobic bacterial cultures from 25 macaques identified 72 bacterial isolates, including 15 Enterococcus faecalis isolates. The E. faecalis isolates displayed multi-drug resistant phenotypes, with resistance to ciprofloxacin, enrofloxacin, trimethoprim-sulfamethoxazole, tetracycline, chloramphenicol, bacitracin, and erythromycin, as well as high-level aminoglycoside resistance. Multi-locus sequence typing showed that most belonged to two E. faecalis sequence types (ST): ST 4 and ST 55. The genomes of three representative isolates were sequenced to identify genes encoding antimicrobial resistances and other traits. Antimicrobial resistance genes identified included aac(6’)-aph(2”), aph(3’)-III, str, ant(6)-Ia, tetM, tetS, tetL, ermB, bcrABR, cat, and dfrG, and polymorphisms in parC (S80I) and gyrA (S83I) were observed. These isolates also harbored virulence factors including the cytolysin toxin genes in ST 4 isolates, as well as multiple biofilm-associated genes (esp, agg, ace, SrtA, gelE, ebpABC), hyaluronidases (hylA, hylB), and other survival genes (ElrA, tpx). Crystal violet biofilm assays confirmed that ST 4 isolates produced more biofilm than ST 55 isolates. The abundance of antimicrobial resistance and virulence factor genes in the ST 4 isolates likely relates to the loss of CRISPR-cas. This macaque colony represents a unique model for studying E. faecalis infection associated with indwelling devices, and provides an opportunity to understand the basis of persistence of this pathogen in a healthcare setting.

Chromosomally and Extrachromosomally Mediated High-Level Gentamicin Resistance in Streptococcus agalactiae

Streptococcus agalactiae (group B Streptococcus [GBS]) is a leading cause of sepsis in neonates. The rate of invasive GBS disease in nonpregnant adults also continues to climb. Aminoglycosides alone have little or no effect on GBS, but synergistic killing with penicillin has been shown in vitro. High-level gentamicin resistance (HLGR) in GBS isolates, however, leads to the loss of a synergistic effect. We therefore performed a multicenter study to determine the frequency of HLGR GBS isolates and to elucidate the molecular mechanisms leading to gentamicin resistance. From eight centers in four countries, 1,128 invasive and colonizing GBS isolates were pooled and investigated for the presence of HLGR. We identified two strains that displayed HLGR (BSU1203 and BSU452), both of which carried the aacA-aphD gene, typically conferring HLGR. However, only one strain (BSU1203) also carried the previously described chromosomal gentamicin resistance transposon designated Tn3706. For the other strain (BSU452), plasmid purification and subsequent DNA sequencing resulted in the detection of plasmid pIP501 carrying a remnant of a Tn3 family transposon. Its ability to confer HLGR was proven by transfer into an Enterococcus faecalis isolate. Conversely, loss of HLGR was documented after curing both GBS BSU452 and the transformed E. faecalis strain from the plasmid. This is the first report showing plasmid-mediated HLGR in GBS. Thus, in our clinical GBS isolates, HLGR is mediated both chromosomally and extrachromosomally.

Characterization of aminoglycoside resistance and virulence genes among Enterococcus spp. isolated from a hospital in China

This study investigated the aminoglycoside resistance phenotypes and genotypes, as well as the prevalence of virulence genes, in Enterococcus species isolated from clinical patients in China. A total of 160 enterococcal isolates from various clinical samples collected from September 2013 to July 2014 were identified to the species level using the VITEK-2 COMPACT system. The antimicrobial susceptibilities of the identified Enterococcus strains were determined by the Kirby-Bauer (K-B) disc diffusion method. PCR-based assays were used to detect the aminoglycoside resistance and virulence genes in all enterococcal isolates. Of 160 Enterococcus isolates, 105 were identified as E. faecium, 35 as E. faecalis, and 20 isolates were classified as “other” Enterococcus species. High-level aminoglycoside resistance (HLAR) for gentamicin, streptomycin, and both antibiotics was identified in 58.8, 50, and 34.4% of strains, respectively. The most common virulence gene (50.6% of isolates) was efaA, followed by asa1 (28.8%). The most prevalent aminoglycoside resistance genes were aac(6')-Ie-aph(2''), aph(2')-Id, aph(3')-IIIa, and ant(6')-Ia, present in 49.4%, 1.3%, 48.8% and 31.3% of strains, respectively. Overall, E. faecium and E. faecalis were most frequently associated with hospital-acquired enterococcal infections in Zhejiang Province. All aminoglycoside resistance genes, except aph(2'')-Id, were significantly more prevalent in HLAR strains than amongst high level aminoglycoside susceptible (HLAS) strains, while there was no significant difference between HLAR and HLAS strains in regard to the prevalence of virulence genes, apart from esp, therefore, measures should be taken to manage infections caused by multi-drug resistant Enterococcus species.

Outcomes for and Risk Factors Associated With Vancomycin-ResistantEnterococcus faecalisand Vancomycin-ResistantEnterococcus faeciumBacteremia in Cancer Patients

Objective.

Vancomycin-resistant enterococci (VRE) are a major cause of nosocomial infection. We sought to compare vancomycin-resistant (VR)Enterococcus faecalisbacteremia and VREnterococcus faeciumbacteremia in cancer patients with respect to risk factors, clinical presentation, microbiological characteristics, antimicrobial therapy, and outcomes.

Methods.

We identified 210 cancer patients with VRE bacteremia who had been treated between January 1996 and December 2004; 16 of these 210 had VRE. faecalisbacteremia and were matched with 32 patients with VRE. faeciumbacteremia and 32 control patients. A retrospective review of medical records was conducted.

Results.

Logistic regression analysis showed that, compared with VRE. faecalisbacteremia, VRE. faeciumbacteremia was associated with a worse clinical response to therapy (odds ratio [OR], 0.3 [95% confidence interval (CI), 0.07-0.98];P= .046) and a higher overall mortality rate (OR, 8.3 [95% CI, 1.9-35.3];P= .004), but the VRE-related mortality rate did not show a statistically significant difference (OR, 6.8 [95% CI, 0.7-61.8];P= .09). Compared with control patients, patients with VRE. faecalisbacteremia were more likely to have received an aminoglycoside in the 30 days before the onset of bacteremia (OR, 5.8 [95% CI, 1.2-27.6];P= .03), whereas patients with VRE. faeciumbacteremia were more likely to have received a carbapenem in the 30 days before the onset of bacteremia (OR, 11.7 [95% CI, 3.6-38.6];P<.001). In a multivariate model that compared patients with VRE. faeciumbacteremia and control patients, predictors of mortality included acute renal failure on presentation (OR, 15.1 [95% CI, 2.3-99.2];P= .004) and VRE. faeciumbacteremia (OR, 11 [95% CI, 2.7-45.1];P<.001). No difference in outcomes was found between patients with VRE. faecalisbacteremia and control patients.

Conclusions.

VRE. faeciumbacteremia in cancer patients was associated with a poorer outcome than was VRE. faecalisbacteremia. Recent receipt of carbapenem therapy was an independent risk factor for VRE. faeciumbacteremia, and recent receipt of aminoglycoside therapy was independent risk factor forE. faecalisbacteremia.

In vitro efficacy of antibiotic beads in treating abdominal vascular graft infections

OBJECTIVE

Abdominal aortic vascular graft infection often involves several different organisms. Antibiotic polymethyl methacrylate (PMMA) beads may be effective in controlling infection after débridement, but bacterial species identification and antibiotic susceptibility are often not available at the time of operation, generating a need for a broad-spectrum drug combination for empirical use. We sought to determine an effective antibiotic in PMMA beads for use in abdominal vascular graft infection.

METHODS

PMMA beads were impregnated with combinations of antibiotics, consisting of daptomycin, tobramycin, and meropenem. Antibiotics were selected on the basis of activity spectrum and heat stability. Beads were placed on separate agar plates with vancomycin-resistant Enterococcus faecalis, Klebsiella pneumoniae, Staphylococcus epidermidis, and methicillin-resistant Staphylococcus aureus. Antibiotic inhibition was recorded by use of a modified agar-based disk-diffusion method.

RESULTS

Daptomycin alone was not active against K. pneumoniae (average = 0 mm). Tobramycin alone was not active against vancomycin-resistant E. faecalis, K. pneumoniae, or methicillin-resistant S. aureus. Tobramycin and daptomycin in combination had moderate broad-spectrum activity with 8- to 14-mm mean inhibition halos. Meropenem showed strong activity against all tested organisms with >15-mm mean inhibition halos. The addition of daptomycin to meropenem provided improved coverage of gram-positive organisms. The presence of tobramycin reduced the efficacy of meropenem.

CONCLUSIONS

Antibiotic PMMA beads containing 10% meropenem with 2.5% daptomycin had excellent in vitro activity against typical bacterial species associated with abdominal vascular graft infections. The addition of antibiotic beads may be a useful adjunct in managing such cases. Further studies are required to determine efficacy in clinical practice.

Characterization of Enterococcus faecium with macrolide resistance and reduced susceptibility to quinupristin/dalfopristin in a Japanese hospital: detection of extensive diversity in erm(B)-regulator regions

Cross-resistance to macrolide, lincosamide, and streptogramin B (MLSB) antibiotics is mainly mediated by the erm (erythromycin ribosome methylation) genes that encode 23S rRNA methylases in enterococi, and various mechanisms are involved in the streptogramin B resistance. Prevalence of MLSB resistance and its genetic mechanisms were analyzed for a total of 159 strains of Enterococcus faecium isolated from clinical specimens in a university hospital in Japan from 1997 to 2006. Resistance to erythromycin (EM) and clindamycin was detected in 88.1% and 89.9% of all the strains examined, respectively, and expression of resistance was totally constitutive. Although none of the strain was resistant to quinupristin/dalfopristin (Q/D), 28 strains (17.6%) showed intermediate resistance to Q/D (MIC: 2 μg/ml). The erm(B) gene was detected in 139 strains (87.4%), and msrC was found in all the strains examined, whereas no other known MLSB resistance genes were identified. The erm(B) regulator region (RR) containing a coding region of the leader peptide was classified into 13 genetic variations (L1-L3, M, S1-S7, D, and R genotypes) in 56 strains. However, no relatedness was identified between the erm(B) RR genotype and EM resistance, or reduced susceptibility to Q/D, although most of Q/D-intermediate strains were assigned to the L1, L2, and S1 genotypes. Q/D-intermediate strains were classified into five multiple-locus variable-number tandem-repeat analysis (MLVA) types, including four types of clonal complex (CC)-C1, five sequence types (STs), including four STs of CC-17, and several resistance gene/virulence factor profiles. The present study revealed the occurrence of Q/D-intermediate E. faecium, which are composed of heterogeneous strains in Japan, and more genetic diversity in the erm(B) RRs than those reported previously.

Enterococcus faecalis clones in poultry and in humans with urinary tract infections, Vietnam

Transmission routes and reservoirs need to be elucidated.

Enterococcus spp. as pathogens have increased, but the sources of infection often remain unclear. To investigate whether poultry might be a reservoir for E. faecalis–associated urinary tract infections (UTIs) in humans, we characterized E. faecalis isolates from patients in Vietnam with UTIs during January 2008–January 2010 and poultry living in close contact with them by multilocus sequence typing (MLST), pulsed-field gel electrophoresis, analysis of antimicrobial drug susceptibility patterns, and sequencing of virulence genes. In 7 (23%) of 31 UTI cases, we detected identical MLST, indistinguishable or closely related pulsed-field gel electrophoresis patterns, and similar antimicrobial drug susceptibility patterns. Isolates from urine and poultry showed identical virulence gene profiles, except for 1 variation, and individual genes showed identical sequences. The homology of isolates from urine and poultry further indicates the zoonotic potential and global spread of E. faecalis sequence type 16, which recently was reported in humans with endocarditis and in pigs in Denmark.

Antibiotic use in animal feed and its impact on human healt

Antibiotic resistance in bacteria that cause disease in man is an issue of major concern. Although misuse of antibiotics in human medicine is the principal cause of the problem, antibiotic-resistant bacteria originating in animals are contributory factors, with some types of resistance in some species of bacteria. Antibiotics are added to animal feeds to treat and prevent infections and to improve growth and production. Until recently, the major concerns about incorporation of antibiotics in animal feeds related to antibiotic residues in products from treated animals. Although, in 1969, the Swann (1969) report drew attention to the potential for antibiotic-resistant bacteria to spread from treated animals via the food chain, there was little response until the detection of vancomycin-resistant enterococci in animals fed a related glycopeptide, avoparcin. Subsequently, attention started to focus on the issue and other examples of transfer of resistant bacteria through the food chain, such as enterococci resistant to quinupristin-dalfopristin or to everninomicin, fluoroquinolone-resistant campylobacters and multiresistant Escherichia coli, and salmonella such as Salmonella typhimurium DT104. Reviews and committees in many countries have highlighted the need for better control of licensing of antibiotics, and codes for prudent use of antibiotics by veterinary practitioners and farmers. The continued use of antibiotic growth promoters has been questioned and there is a need to ensure that antibiotics important in human medicine are not used therapeutically or prophylactically in animals.

Gilthead seabream (Sparus aurata) carrying antibiotic resistant enterococci. A potential bioindicator of marine contamination?

Antibiotic resistance in bacteria is a growing problem that is not only restricted to the clinical setting but also to other environments such as marine species that harbor antibiotic resistant bacteria and therefore may serve as reservoirs for antibiotic-resistance genetic determinants. The aim of this study was to evaluate antibiotic resistance phenotypes in enterococci isolated from fecal samples of gilthead seabream and the associated mechanisms of resistance. A collection of 118 samples were analyzed and 73 enterococci were recovered. The strains showed high percentages of resistance to erythromycin and tetracycline (58.9% and 17.8%, respectively). Lower level of resistance (<13%) was detected for quinupristin-dalfopristin, ampicillin, high-level-gentamicin, high-level-streptomycin, high-level-kanamycin, ciprofloxacin and chloramphenicol. The erm(B), tet(L) or tet(M), aac(6')-aph(2″) and aph(3')-IIIa genes were shown in isolates resistant to erythromycin, tetracycline, high-level gentamicin and high-level kanamycin, respectively. Antibiotic resistance in natural microbiota is becoming a concern of human and environmental health.

Prevalence of the erm(T) gene in clinical isolates of erythromycin-resistant group D Streptococcus and Enterococcus

Among 48 erythromycin-resistant group D streptococci (GDS), 36 had the erm(T) resistance gene. erm(T) was also found in 4 of 31 erythromycin-resistant Enterococcus faecium isolates. This is the first report of the erm(T) gene in U.S. GDS isolates and the first report of the erm(T) gene in enterococci.

Prevalence and Mechanism of Resistance against Macrolides, Lincosamides, and Streptogramins amongEnterococcus faeciumIsolates from Food-Producing Animals and Hospital Patients in Belgium

The prevalence of acquired resistance to streptogramins, macrolides, and lincosamides and the genetic background of this resistance was investigated in Enterococcus faecium strains isolated from food-producing animals and hospital patients 4-5 years after the ban of streptogramins as growth promoters. The minimum inhibitory concentrations (MICs) of quinupristin/dalfopristin (Q/D), virginiamycin M1 (virgM1), erythromycin (ery), tylosin (tyl), and lincomycin (lin) were determined by the agar dilution method for E. faecium isolates derived from pigs (80), broilers (45), and hospitalized patients (103). Resistance or susceptibility was interpreted using a microbiological criterion and breakpoints recommended by the Clinical Laboratory Standards Institute (CLSI), if available. The isolates were also screened by PCR for erm(B), lnu(A), lnu(B), mef(A/E), vat(D), vat(E), vga(A), vga(B), and vgb(A) genes. Acquired resistance to Q/D, virgM1, ery, tyl, and lin was detected in 34%, 96%, 46%, 46%, and 69% of the porcine strains, respectively. For broiler strains this was 15% (Q/D), 98% (virgM1), 69% (ery), 71% (tyl), and 89% (lin) and for human strains 23% (Q/D), 65% (virgM1), 54% (ery), 52% (tyl), and 60% (lin). Strains showing cross-resistance against macrolides and lincosamides almost always carried the erm(B) gene. This gene was present in 64% of the Q/D-resistant isolates. Only in two human and three broiler Q/D- and virgM1-resistant isolates, a combination of the erm(B) and vat(D) or vat(E) genes was found. The genetic background of resistance could not be determined in the other Q/D- or virgM1-resistant strains. This study demonstrates that streptogramin resistance is frequently present in strains from hospitalized patients and food-producing animals, but the genetic basis hitherto mostly remains obscure.

Daptomycin antimicrobial activity tested against methicillin-resistant staphylococci and vancomycin-resistant enterococci isolated in European medical centers (2005)

BACKGROUND

Daptomycin is a cyclic lipopeptide with potent activity and broad spectrum against Gram-positive bacteria currently used for the treatment of complicated skin and skin structure infections and bacteremia, including right sided endocarditis. We evaluated the in vitro activity of this compound and selected comparator agents tested against clinical strains of staphylococci and enterococci collected in European medical centers in 2005.

METHODS

A total of 4,640 strains from 23 medical centers located in 10 European countries, Turkey and Israel (SENTRY Program platform) were tested for susceptibility by reference broth microdilution methods according to Clinical and Laboratory Standards Institute guidelines and interpretative criteria. Mueller-Hinton broth was supplemented to 50 mg/L Ca++ for testing daptomycin. Results for oxacillin (methicillin)-resistant staphylococci and vancomycin-resistant enterococci were analyzed separately.

RESULTS

Oxacillin resistance rates among Staphylococcus aureus varied from 2.1% in Sweden to 42.5% in the United Kingdom (UK) and 54.7% in Ireland (29.1% overall), while vancomycin resistance rates varied from 0.0% in France, Sweden and Switzerland to 66.7% in the UK and 71.4% in Ireland among Enterococcus faecium (17.9% overall). All S. aureus strains were inhibited at daptomycin MIC of 1 mg/L (MIC50/90, 0.25/0.5 mg/L; 100.0% susceptible) and only one coagulase-negative staphylococci strain (0.1%) showed an elevated (>1 mg/L) daptomycin MIC value (4 mg/L). Among E. faecalis (MIC50/90, 0.5/1 mg/L; 100% susceptible) the highest daptomycin MIC value was 2 mg/L; while among E. faecium (MIC50/90, 2/4 mg/L; 100% susceptible) the highest MIC result was 4 mg/L.

CONCLUSION

Daptomycin showed excellent in vitro activity against staphylococci and enterococci collected in European medical centers in 2005 and resistance to oxacillin, vancomycin or quinupristin/dalfopristin did not compromise its activity overall against these pathogens. Based on these results and those of previous publications, daptomycin appears to be an excellent therapeutic option for serious infections caused by oxacillin-resistant staphylococci and vancomycin-resistant enterococci in Europe.

Evaluation of the in vitro activity of daptomycin against 19615 clinical isolates of Gram-positive cocci collected in North American hospitals (2002-2005)

We evaluated the antimicrobial activity of daptomycin against 19,615 clinical strains consecutively collected by numerous centers located across the United States and Canada (2002-2005). Daptomycin was very active against all indicated species (>99% susceptible), with the highest MIC results being 2, 8, 0.5, and 1 microg/mL for staphylococci, enterococci, beta-hemolytic streptococci, and viridans group streptococci, respectively, and no significant loss in potency was observed over the period studied.

Assessment of RAISUS, a novel system for identification and antimicrobial susceptibility testing for enterococci

RAISUS, a system developed by Nissui Pharmaceutical (Tokyo, Japan), is a novel fully automated system for rapid identification and antimicrobial susceptibility testing. The aim of this study was to compare RAISUS with VITEK systems and microdilution tests based on the National Committee for Clinical Laboratory Standards, with regard to the identification and susceptibility of 64 enterococci. The agreement rate between RAISUS and VITEK was 98.4% (63/64) for bacterial identification. One strain was identified as E. faecalis by RAISUS, but as E. faecium by VITEK. Regarding susceptibility tests, the range of essential agreement and agreement in clinical categories for RAISUS and VITEK ranged from 70.3% to 95.3% and from 68.8% to 96.9%, respectively. Results of antimicrobial susceptibility testing for vancomycin (VAN) showed very major, major, and minor errors in 0%, 3.1% (2/64), and 0%, respectively. RAISUS could provide reports of detection of VAN-resistant enterococci (VRE) within 5 h by using fluorogenic substances and redox. In conclusion, RAISUS could be useful in a clinical setting because it allows rapid identification of enterococci and the potential ability to detect VRE more promptly than the VITEK system.

Antimicrobial resistance and the mechanisms implicated in faecal enterococci from healthy humans, poultry and pets in Portugal

Antimicrobial resistance and the mechanisms implicated were studied in 440 enterococci (227 Enterococcus faecium, 177 Enterococcus faecalis, 32 Enterococcus hirae and 4 Enterococcus durans) recovered from 220 faecal samples of healthy humans, poultry and pets in Portugal. Higher levels of resistance were detected for ampicillin, tetracycline, erythromycin and chloramphenicol in poultry isolates (10.5%, 97%, 87.5% and 16%, respectively) compared with human isolates (0%, 26%, 31.5% and 5%, respectively); intermediate levels of resistance for these antibiotics were found in pet isolates. Thirty-three per cent of the E. faecium isolates of poultry origin showed quinupristin/dalfopristin resistance. High-level resistance to gentamicin or streptomycin was detected in 1-7% of isolates in our series of enterococci. The aac(6')-aph(2''), aph(3')-IIIa, erm(B) and tet(M) genes were demonstrated in most of the gentamicin-, kanamycin-, erythromycin- and tetracycline-resistant isolates, respectively. The vat(E) gene was found in 39% of the quinupristin/dalfopristin-resistant E. faecium isolates of poultry origin.

Vancomycin-resistant enterococci: consequences for therapy and infection control

Vancomycin-resistant enterococci (VRE) have emerged as important nosocomial pathogens, initially in the USA, but now also in Europe, where hospital outbreaks are being reported with increasing frequency, although the incidence of VRE infections remains extremely low in most European countries. The recently demonstrated in-human transmission of vancomycin resistance from VRE to methicillin-resistant Staphylococcus aureus (MRSA) in two American patients underscores the potential danger of a coexisting reservoir of both pathogens. As MRSA is already endemic in many European hospital settings, prevention of endemicity with VRE seems relevant, but should be balanced against the costs associated with the implementation of effective strategies. The presence of a large community reservoir of VRE in Europe could hamper the feasibility of infection control strategies. Although the prevalence of colonisation amongst healthy subjects has apparently decreased after the ban on avoparcin use in the agricultural industry, a large proportion of admitted patients are still potential sources of VRE transmission. With no risk profile available to identify these carriers, effective screening, followed by barrier precautions for carriers, seems to be impossible. Recent studies, however, have suggested that hospital outbreaks are almost exclusively caused by specific genogroups of VRE that can be characterised phenotypically and genotypically (e.g., co-resistance to ampicillin and the presence of the variant esp gene). Based on our own experience, we propose that VRE infection control programmes should be restricted to patients colonised with these VRE strains. If such a strain is cultured from a clinical sample, surveillance amongst contact patients is recommended and barrier precautions should be implemented in the case of documented spread.

Effect of Avilamycin Fed to Chickens onE. faeciumCounts and on the Selection of Avilamycin-ResistantE. faeciumPopulations

This study was conducted to investigate the effect of avilamycin used as a growth promoter on the number of E. faecium and on avilamycin-resistant E. faecium in the intestines of broilers over time. Avilamycin was added at 13.6 ppm to the feed of chickens during 28 days or during a typical growth period of 42 days; a nonmedicated group was included. Three hundred twenty-four Ross broiler chickens were equally distributed over the different groups in a treatment trial and kept in three isolation rooms. In each room, two replicates of the three experimental groups were kept in separate pens. At various time points, samples from different intestinal compartments or the feces were serially diluted and plated on avilamycin-supplemented and on unsupplemented Slanetz and Bartley (SL) media, and E. faecium counts were recorded. Only in the feces and only on the last sampling day was a significant decrease noted in the E. faecium counts in chickens treated with avilamycin for 42 days. Intermediate resistant (MIC 4-8 microg/ml) and resistant strains (MIC>or=16 microg/ml) were isolated from all groups, and there was a rise in prevalence over time. Pulsed-field gel electrophoresis profiles of these strains indicated clonal spread from one pen to another within the same room. The ratio between the counts of E. faecium isolated on antibiotic-supplemented to unsupplemented plates was significantly higher at the end of the trial in the feces samples from the group fed avilamycin for 42 days compared to the other groups, indicating a selective effect of avilamycin.

Enterococci spp. isolated from Cuba: species frequency of occurrence and antimicrobial susceptibility profile

This study investigated the species distribution and antimicrobial resistance among 99 enterococci isolated from hospitalized patients in 12 hospitals in Cuba from October 2000 to September 2001. Species identification was performed by WIDER Automatic System (Francisco Soria Melguizo, Madrid, Spain), and the susceptibility testing was performed by disk diffusion, agar dilution, and E-test methods. Enterococcus faecalis was the most prevalent (85%) species, followed by E. faecium (10%), E. gallinarum (2%), E. casseliflavus (2%), and E. durans-hirae (1%). A higher percentage of resistance to ampicillin (50%), fosfomycin (40%), ciprofloxacin (30%), norfloxacin (20%), and tetracycline (90%) was detected in E. faecium isolates, whereas E. faecalis strains showed higher rates of resistance to erythromycin (52.4%), chloramphenicol (34.5%), rifampicin (62.5%), moxifloxacin (3%), and nitrofurantoin (2.4%). Resistance to glycopeptide was detected in E. faecalis (1.2%) and E. faecium (10%). Thirty-one E. faecalis (37%) and 3 E. faecium (30%) showed a high-level resistance to gentamicin. The results of this work will be very helpful to guide empirical antimicrobial therapy and the implementation of infection control measures in Cuban hospitals.

Daptomycin in vitro susceptibility in European Gram-positive clinical isolates

The objective of this study was to determine the activity of daptomycin, a novel lipopeptide, against European Gram-positive isolates (n = 1539). The MIC(90)-values of daptomycin against Staphylococcus aureus isolates was 0.25 mg/L, against Enterococcus faecalis 4 mg/L, against Enterococcus faecium 8 mg/L, 0.25 mg/L against Staphylococcus epidermidis, and 0.25mg/L against Streptococcus pneumoniae. Daptomycin was equally potent against antibiotic-susceptible and resistant strains within a particular species. Based on a breakpoint of 1 mg/L for S. aureus and group A streptococci, all isolates tested were susceptible to daptomycin. Based on a breakpoint of 4 mg/L for vancomcyin-susceptible E. faecalis 99.7% of these isolates were susceptible to daptomycin.

Antimicrobial resistance of Enterococcus species isolated from produce

The purpose of this study was to characterize the antibiotic resistance profiles of Enterococcus species isolated from fresh produce harvested in the southwestern United States. Among the 185 Enterococcus isolates obtained, 97 (52%) were Enterococcus faecium, 38 (21%) were Enterococcus faecalis, and 50 (27%) were other Enterococcus species. Of human clinical importance, E. faecium strains had a much higher prevalence of resistance to ciprofloxacin, tetracycline, and nitrofurantoin than E. faecalis. E. faecalis strains had a low prevalence of resistance to antibiotics used to treat E. faecalis infections of both clinical and of agricultural relevance, excluding its intrinsic resistance patterns. Thirty-four percent of the isolates had multiple-drug-resistance patterns, excluding intrinsic resistance. Data on the prevalence and types of antibiotic resistance in Enterococcus species isolated from fresh produce may be used to describe baseline antibiotic susceptibility profiles associated with Enterococcus spp. isolated from the environment. The data collected may also help elucidate the role of foods in the transmission of antibiotic-resistant strains to human populations.

Detection of enterococcal surface protein gene (esp) and amplified fragment length polymorphism typing of glycopeptide-resistant Enterococcus faecium during its emergence in a Greek intensive care unit

The emergence of glycopeptide-resistant Enterococcus faecium (GREF) in a Greek intensive care unit was studied by amplified fragment length polymorphism analysis and esp gene detection. Three GREF clones harboring the esp gene were recovered from 17 out of 21 patients, indicating the dissemination of genetically homogenous and virulent strains of GREF.

Determination of antibiotic resistance and resistance plasmids of clinical Enterococcus species

To determine the antibiotic resistance pattern and resistance plasmids, we studied 23 antibiotic-resistant clinical isolates of Enterococcus spp. which caused infection in Bayindir-Ankara Hospital, Turkey. Biochemical and physiological identification tests were applied by the Vitek system and compared with the results of protein profiles by SDS-PAGE. From 23 isolates, 20 were identified as E. faecalis, 2 as E. faecium and 1 as E. gallinarum. Twenty four antibiotics belong to 10 different groups were used in susceptibility tests. Multiple antibiotic resistance was determined in 10 of 23 Enterococcus spp. Overall resistance to the used antibiotics was 47.3% and low level resistance was 16.6%. Among the isolates tested, 8.7% demonstrated high level gentamicin resistance, 17.4% demonstrated high level streptomycin resistance, and 43.5% demonstrated penicillin resistance. High level vancomycin resistant Enterococcus spp. rate was 34.8%, and 60.9% exhibited low level resistance to vancomycin and teicoplanin. They contain plasmids which varied in numbers between 1 and 11 and the plasmid sizes ranged from 2.08 to 56.15 kb. In curing experiments with acriflavine, two different plasmids were shown in different molecular sizes of 33.49 and 13.6 kb while the first determined glycopeptide and penicillin resistance, the second one determined either glycopeptide or penicillin resistance in two different E. faecalis strains. On the other hand, a 22.58 kb plasmid, determining kanamycin resistance, was detected in an E. faecium strain. After the curing experiments, an elimination of 37.17 and 44.47 kDa protein bands was shown in E. faecium EFA1 and E. faecalis EFA13 in SDS-PAGE, respectively. This survey indicates the increase of antibiotic-resistant enterococci, especially to vancomycin in our hospital isolates.

Streptogramin resistance among Enterococcus faecium isolated from production animals in Denmark in 1997

The genetic background for streptogramin resistance was examined in Enterococcus faecium isolated from pigs (n = 55) and broilers (n = 207) in 1997 in Denmark. Fifty-one percent and 67%, respectively, of the isolates were resistant to streptogramins. Among streptogramin-resistant E. faecium (SREF), the genetic background for streptogramin A resistance could be determined in 96% of the isolates from broilers, compared with 14% among SREF from pigs. For broiler isolates 89% of SREF contained the vat(E) gene and 10% the vat(D) gene. Three of these isolates contained both resistance genes. Among SREF from pigs two isolates contained the vat(E) gene and two others the vat(D) gene. The genetic background for streptogramin B was most often identified as the erm(B) gene encoding macrolide, lincosamide, and streptogramin B (MLSB) resistance. Among SREF, 84% and 86% of isolates from broilers and pigs, respectively, contained the erm(B). In SREF from broilers, the erm(B) gene was physically linked to the vat(E) gene in 62% of the vat(E)-positive isolates and 79% of the isolates containing vat(D). erm(A) was detected in two SREF of broiler origin. Both isolates also contained the erm(B) gene. No SREF contained the vgb(A) gene encoding streptogramin B resistance. On the basis of genetic characterization, streptogramin-resistant isolates from broiler were divided into subgroups, according to the presence of the streptogramin A genes, to determine possible co-resistance to antimicrobials, especially glycopeptides. Twenty-five percent of the SREF from broilers were glycopeptide resistant (MIC > 16 microg/ml). None of the isolates containing the streptogramin A gene vat(D) was resistant to glycopeptide, whereas isolates containing the vat(E) gene had a lower prevalence to glycopeptide resistance than the streptogramin-sensitive isolates.

Antimicrobial growth promoters used in animal feed: effects of less well known antibiotics on gram-positive bacteria

There are not many data available on antibiotics used solely in animals and almost exclusively for growth promotion. These products include bambermycin, avilamycin, efrotomycin, and the ionophore antibiotics (monensin, salinomycin, narasin, and lasalocid). Information is also scarce for bacitracin used only marginally in human and veterinary medicine and for streptogramin antibiotics. The mechanisms of action of and resistance mechanisms against these antibiotics are described. Special emphasis is given to the prevalence of resistance among gram-positive bacteria isolated from animals and humans. Since no susceptibility breakpoints are available for most of the antibiotics discussed, an alternative approach to the interpretation of MICs is presented. Also, some pharmacokinetic data and information on the influence of these products on the intestinal flora are presented.