Outbreak of Vancomycin-Susceptible Enterococcus faecium Containing the Wild-Type vanA Gene

Accurate detection of vancomycin-resistant enterococci (VRE) is essential in preventing transmission in health care settings. Chromogenic media are widely used for screening VRE because of fast turnaround times (TAT) and high sensitivity. We report an outbreak of Enterococcus faecium bearing vanA yet susceptible to vancomycin (vancomycin-variable Enterococcus [VVE]). Between October 2009 to March 2011, clinical and screening specimens (n = 14,747) were screened for VRE using VRE-selective medium and/or PCR. VVE isolates were genotyped to determine relatedness. Plasmids from these isolates were characterized by sequencing. Overall, 52 VVE isolates were identified, comprising 15% of all VRE isolates identified. Isolates demonstrated growth on Brilliance VRE agar (Oxoid) at 24 h of incubation but did not grow on brain heart infusion agar with 6 μg/ml vancomycin (Oxoid) or bile esculin azide agar with 6 μg/ml vancomycin (Oxoid) and were susceptible to vancomycin. Genotyping of 20 randomly selected VVE isolates revealed that 15/20 were identical, while 5 were highly related. PCR of the VVE transposon confirmed the presence of vanHAXY gene cluster; however, vanS (sensor) and vanR (regulator) genes were absent. The outbreak was controlled through routine infection control measures. We report an emergence of a fit strain of E. faecium containing vanA yet susceptible to vancomycin. Whether this new strain represents VRE has yet to be determined; however, unique testing procedures are required for reliable identification of VVE.     

Vancomycin-Variable Enterococcal Bacteremia

Vancomycin-variable enterococcus (VVE) is an emerging pathogen. VVE isolates initially appear phenotypically susceptible to vancomycin but possesses the vanA gene and can develop in vitro and in vivo resistance to vancomycin. We report a case of VVE bacteremia and describe how VVE poses diagnostic and therapeutic dilemmas.     

Vancomycin-resistant Enterococcus faecium and the emergence of new sequence types associated with hospital infection

Enterococcus faecium is a major species in infections by vancomycin-resistant enterococci (VRE). New variants of the pathogen have emerged and become dominant in healthcare settings. Two such examples, vanB ST796 and vanA ST1421 sequence types, originally arose in Australia and proceeded to cause VRE outbreaks in other countries. Of concern is the detection in Europe of vancomycin variable enterococci (VVE) belonging to ST1421 that exhibit a vancomycin-susceptible phenotype but can revert to resistant in the presence of vancomycin. The recent application of genome sequencing for increasing our understanding of the evolution and spread of VRE is also explored here.     

Comparison of antimicrobial resistance patterns in enterococci from intensive and free range chickens in Australia

Resistance to antimicrobials in enterococci from poultry has been found throughout the world and is generally recognized as associated with antimicrobial use. This study was conducted to evaluate the phenotypic and genotypic profile of enterococcal isolates of intensive (indoor) and free range chickens from 2008/09 and 2000 in order to determine the patterns of antimicrobial resistance associated with different management systems. The minimum inhibitory concentrations in faecal enterococci isolates were determined by agar dilution. Resistance to bacitracin, ceftiofur, erythromycin, lincomycin, tylosin and tetracycline was more common among meat chickens (free range and intensive) than free range egg layers (P<0.05). Isolates were evaluated by polymerase chain reaction for bacitracin (bcrR), tylosin (ermB), tetracycline (tet(L), tet(M), tet(O), tet(S), and tet(K)), gentamicin (aac6-aph2), vancomycin (vanC and vanC2), ampicillin (pbp5) and integrase (int) genes. Resistance to bacitracin, erythromycin and tetracycline were found to be correlated with the presence of bcrR, ermB, and tet genes in most of the isolates collected from meat chickens. Most bacteria encoding ermB gene were found to express cross-resistance to erythromycin, tylosin and lincomycin. No significant difference was found in these resistance genes between isolates sampled in 2000 and 2008/09 (P<0.5). Unlike the enterococcal strains sampled in 2000, the 2008/09 isolates were found to be susceptible to vancomycin and virginiamycin. This study provides evidence that, despite strict regulation imposed on antibiotic usage in poultry farming in Australia, antimicrobial resistance is present in intensively raised and free range meat chickens.     

Genetic characterization of vancomycin‐resistant enterococci isolates from wild rabbits

The presence of van A‐containing E. faecium isolates was demonstrated in three of 77 faecal samples (3.9%) of wild rabbits recovered in Portugal. Enterococcal strains with intrinsic vancomycin resistance (van C‐1 or van C‐2/3 gene) were found in five (6.5%) and three (3.9%) faecal samples, respectively. The mechanisms of resistance for other antibiotics were studied in these vancomycin‐resistant isolates. All van A strains showed resistance for tetracycline [with the presence of tet (L) gene, associated or not with tet (M) gene] and for erythromycin [with the presence of the erm (B) gene]. Two isolates were resistant to ciprofloxacin and one to ampicillin. Two van C‐1 strains and one van C‐2/3 strain were tetracycline resistant [containing the tet (M) gene associated with tet (L) gene] and erythromycin resistant [with erm (B) gene]. Two van C‐1 and two van C‐2/3 strains were also ciprofloxacin resistant and one van C‐1 strain was, additionally, resistant to quinupristin‐dalfopristin. The two remaining isolates (van C‐1, van C‐2/3) did not show resistance for any additional antibiotic. The intestinal tract of wild rabbits could be a reservoir of van A‐containing enterococci. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Evaluation of vancomycin MIC creep in methicillin-resistant Staphylococcus aureus infections—a systematic review and meta-analysis

ObjectivesVancomycin is currently the primary option treatment for methicillin-resistant Staphylococcus aureus (MRSA). However, an increasing number of MRSA isolates with high MICs, within the susceptible range (vancomycin MIC creep), are being reported worldwide. Resorting to a meta-analysis approach, this study aims to assess the evidence of vancomycin MIC creep.MethodsWe searched for studies in the PubMed database. The inclusion criteria for study eligibility included the possibility of retrieving the reported data values of vancomycin MIC and information concerning the applied MIC methodology.ResultsThe mean values of vancomycin MICs, of all 29 234 S. aureus isolates reported in the 55 studies included in the meta-analysis, were 1.23 mg/L (95% CI 1.13–1.33) and 1.20 mg/L (95% CI 1.13–1.28) determined by Etest and broth microdilution method, respectively. No significant differences were observed between these two methodologies. We found negative correlation between pooled mean/pooled proportion and time strata.ConclusionsWe have found no evidence of the MIC creep phenomenon.     

Nationwide surveillance of antimicrobial resistance in invasive isolates of Streptococcus pneumoniae in Taiwan from 2017 to 2019

Background/purposeStreptococcus pneumoniae causes pneumonia and other invasive diseases, and is a leading cause of mortality in the elderly population. The present study aimed to provide current antimicrobial resistance and epidemiological profiles of S. pneumoniae infections in Taiwan.MethodsA total of 252 nonduplicate S. pneumoniae isolates were collected from patients admitted to 16 hospitals in Taiwan between January 2017 and December 2019, and were analyzed. The minimum inhibitory concentration of antibiotics was determined using the Vitek 2 automated system for antimicrobial susceptibility testing. Furthermore, epidemiological profiles of S. pneumoniae infections were analyzed.ResultsAmong the strains analyzed, 88% were recognized as invasive pneumococcal strains. According to the Clinical and Laboratory Standards Institute criteria for non-meningitis, the prevalence of penicillin-non-susceptible S. pneumoniae demonstrated a declining trend from 43.6% in 2017 to 17.2% in 2019. However, the rate of penicillin-non-susceptible S. pneumoniae was 85.7% based on the criteria for meningitis. Furthermore, the prevalence of ceftriaxone-non-susceptible S. pneumoniae was 62.7% based on the criteria for meningitis. Isolates demonstrated higher susceptibility toward doripenem and ertapenem than toward meropenem and imipenem. An increased rate of non-susceptibility toward levofloxacin was observed in southern Taiwan (15.1%) and elderly patients (≥65 years; 11.4%). Most isolates were susceptible to vancomycin and linezolid.ConclusionEmpirical treatment with ceftriaxone monotherapy for pneumococcal meningitis should be carefully monitored owing to its high non-susceptibility rate. The susceptibility rates of most isolates to penicillin (used for treating non-meningitis pneumococcal diseases), carbapenems (ertapenem and doripenem), respiratory quinolones (moxifloxacin and levofloxacin), vancomycin, and linezolid suggested the potential of these antibiotics in treating pneumococcal diseases in Taiwan.     

Characterization of Enterococcus faecium isolates and first report of vanB phenotype–vanA genotype incongruence in the Middle East

We aimed to characterize the vancomycin genotype/phenotype, carriage of putative virulence genes, and genetic relatedness of Enterococcus faecium isolates in Saudi Arabia. E. faecium isolated from inpatients at our medical center were studied. Sensitivity to ampicillin, linezolid, teicoplanin, quinupristin/dalfopristin, tetracycline, and ciprofloxacin was determined. The presence of van genes and virulence genes for aggregation substance (Asa-1), enterococcal surface proteins (esp), cytolysin (cylA, cylL, cylM), gelatinase (gelE), E. faecium endocarditis antigen (EfaA _fm ), hyaluronidase (hyl), and collagen adhesion (Ace) was assessed. Genetic relatedness was determined by pulsed-field gel electrophoresis (PFGE). Twenty-nine E. faecium isolates were obtained and the majority of isolates (n/N?=?22/29) were from stool specimens. PFGE analysis identified eight pulsotypes (A–H) based on 80?% similarities. Isolates were represented in five major pulsotypes: type A (n?=?5), type B (n?=?3), type D (n?=?6), type E (n?=?5), and type F (n?=?7). All isolates were vanA gene-positive. Thirteen isolates had vanA⁺/vanB⁺ genotype. Of these, ten exhibited a vanB phenotype and three had a vanA phenotype. Eight isolates with vanA⁺/vanB^? genotype exhibited vanB phenotype. Six of these eight isolates belonged to the same pulsotype. All isolates were positive for gelE, esp, and EfaA _fm genes. Five were CylA-positive and 24 had the hyl genes. Of the eight isolates harboring a combination of gelE, esp, EfaA _fm , and hyl genes, five showed vanB phenotype–vanA genotype incongruence. This is the first report of vanB phenotype–vanA genotype incongruent E. faecium in the Middle East region. Molecular typing indicates clonal spread and high occurrence of virulence genes, especially esp genes, associated with epidemic clones.     

Vancomycin‐resistant Enterococcus spp.: validation of susceptibility testing and in vitro activity of vancomycin,linezolid, tigecycline and daptomycin

Rathe M, Kristensen L, Ellermann‐Eriksen S, Thomsen MK, Schumacher H. Vancomycin‐resistant Enterococcus spp.: validation of susceptibility testing and in vitro activity of vancomycin, linezolid, tigecycline and daptomycin. APMIS 2010; 118: 66–73. Vancomycin‐resistant enterococci (VRE) have emerged to become a significant nosocomial pathogen. However, detection may be challenging and treatment possibilities are limited. Reports of resistance to linezolide, daptomycin and tigecycline underline the need for reliable susceptibility testing with respect to these compounds. We evaluated the in vitro activity of vancomycin, linezolid, daptomycin and tigecycline against a panel of VRE and vancomycin‐susceptible enterococci by broth microdilution (BMD). Etest for determination of minimum inhibitory concentration of these four antibiotics and two disc diffusion assays for detecting VRE and for susceptibility testing against tigecycline and linezolid were evaluated. Before susceptibility testing, all isolates were classified by polymerase chain reaction as vanA or vanB gene positive or vanA/B gene negative. Linezolid, daptomycin and tigecycline had excellent in vitro activity towards all isolates. For daptomycin and tigecycline, the overall agreement between BMD and Etest was suboptimal. For both disc diffusion assays, use of current break points was inadequate to detect vancomycin resistance for isolates carrying the vanB gene. Inspection of the inhibition zone for a diffuse edge, as recommended, accurately predicted presence of the vanB gene.     

Dalbavancin exposure in vitro selects for dalbavancin-non-susceptible and vancomycin-intermediate strains of methicillin-resistant Staphylococcus aureus

ObjectivesDalbavancin is a lipoglycopeptide active against methicillin-resistant Staphylococcus aureus (MRSA). Its long half-life (8.5–16 days) allows for once-weekly or single-dose treatments but could prolong the mutant selection window, promoting resistance and cross-resistance to related antimicrobials such as vancomycin. The objective of this study was to evaluate the capacity of post-distributional pharmacokinetic exposures of dalbavancin to select for resistance and cross-resistance in MRSA.MethodsWe simulated average, post-distributional exposures of single-dose (1500 mg) dalbavancin (fCmax 9.9 μg/mL, β-elimination t_1/2 204 h) in an in vitro pharmacokinetic/pharmacodynamic (PK/PD) model for 28 days (672 h) against five MRSA strains and one methicillin-susceptible strain (MSSA). Samples were collected at least daily, and surviving colonies were enumerated and screened for resistance on drug-free and dalbavancin-supplemented medium respectively. Isolates from resistance screening plates were subjected to whole-genome sequencing (WGS) and susceptibly testing against dalbavancin, vancomycin, daptomycin, and six β-lactams with varying penicillin-binding protein (PBP) affinities.ResultsDalbavancin was bactericidal against most strains for days 1–4 before regrowth of less susceptible subpopulations occurred. Isolates with eight-fold increases in dalbavancin MIC were detected as early as day 4 but increased 64–128-fold in all models by day 28. Vancomycin and daptomycin MICs increased 4–16-fold, exceeding the susceptibly breakpoints for both antibiotics; β-lactam MICs generally decreased by two-to eight-fold, suggesting a dalbavancin–β-lactam seesaw effect, but increased by eight-fold or more in certain isolates. Resistant isolates carried mutations in a variety of genes, most commonly walKR, apt, stp1, and atl.ConclusionsIn our in vitro system, post-distributional dalbavancin exposures selected for stable mutants with reduced susceptibility to dalbavancin, vancomycin, and daptomycin, and generally increased susceptibility to β-lactams in all strains of MRSA tested. The clinical significance of these findings remains unclear, but created an opportunity to genotype a unique collection of dalbavancin-resistant strains for the first time. Mutations involved genes previously associated with vancomycin intermediate susceptibility and daptomycin non-susceptibility, most commonly walKR-associated genes.     

Emergence of dalbavancin non-susceptible,vancomycin-intermediate Staphylococcus aureus (VISA) after treatment of MRSA central line-associated bloodstream infection with a dalbavancin- and vancomycin-containing regimen

ObjectivesDalbavancin is a long-acting lipoglycopeptide with activity against gram-positives, including methicillin-resistant Staphylococcus aureus (MRSA). The potential for lipoglycopeptides, with half-lives greater than 1 week, to select for resistance is unknown. Here we explore a case of MRSA central line-associated bloodstream infection in which dalbavancin and vancomycin non-susceptibility emerged in a urine isolate collected after the patient was treated with vancomycin and dalbavancin sequentially.MethodsIsolates from blood and urine underwent susceptibility testing, and whole genome sequencing (WGS). The blood isolate was subjected to successive passage in vitro in the presence of escalating dalbavancin concentrations and the emergent isolate was subjected to repeat susceptibility testing and WGS.ResultsThe blood isolate was fully susceptible to vancomycin; however, MICs of the urine isolate to dalbavancin, vancomycin, telavancin, and daptomycin were at least fourfold higher than the blood-derived strain. Both strains were indistinguishable by spa and variable number tandem repeat (VNTR) typing, and WGS revealed only seven variants, indicating clonality. Four variants affected genes, including a 3bp in-frame deletion in yvqF, a gene which has been implicated in glycopeptide resistance. Vancomycin and dalbavancin non-susceptibility emerged in the blood isolate after successive passage in vitro in the presence of dalbavancin, and WGS identified a single non-synonymous variant in yvqF.ConclusionsThis is the first case in which VISA has emerged in the context of a dalbavancin-containing regimen. The selection for cross-resistance to vancomycin in vitro by dalbavancin exposure alone is troubling. Clinicians should be aware of the possibility for emergence of dalbavancin non-susceptibility and glycopeptide cross-resistance arising following therapy.     

Serum trough level as a postmarketing quality measure of generic vancomycin products

BackgroundThe vancomycin trough level (VTL) is the most widely used pharmacokinetic parameter for monitoring its clinical efficacy. Whether the VTL is affected in patients receiving different vancomycin products has not previously been determined.MethodsFrom 2005 to 2015, five vancomycin products, including the innovator (designated as VAN-Lilly) and four generic versions (designated as VAN-A, VAN-B, VAN-C and VAN-D), were sequentially used in a teaching hospital. The initial VTLs were compared between patients who received different vancomycin products after propensity score (PS) weighting and matching for clinical covariates.ResultsAmong 8735 patients with initial VTL levels available for analysis, a significant association was identified between the VTL and different vancomycin products in children aged 1 month to 12 years (P < 0.0001). The PS weighting analysis in the paediatric group disclosed children on VAN-C had higher VTL compared to those on other four products (P = 0.0008). PS matching analysis revealed that children who received VAN-C had significantly higher VTLs than those who received VAN-Lily (P = 0.0001), VAN-A (P = 0.0008), VAN-B (P = 0.0002) or VAN-D (P = 0.0015). Furthermore, the coefficient of variation of the VTL was much greater in patients who received VAN-C than in those who received the other four versions, suggesting an unstable quality of this product.ConclusionA generic version of vancomycin generated significantly higher concentrations and greater variation of VTLs than the innovator and other generic vancomycin products in children. The VTL can serve as an indicator to monitor the quality of vancomycin products after marketing.     

Characterisation and transferability of antibiotic resistance genes from lactic acid bacteria isolated from Irish pork and beef abattoirs

Lactic acid bacteria isolated from Irish pork and beef abattoirs were analysed for their susceptibility to antimicrobials. Thirty-seven isolates (12 enterococci, 10 lactobacilli, 8 streptococci, 3 lactococci, 2 Leuconostoc, and 2 pediococci) were examined for phenotypic resistance using the E-test and their minimum inhibitory concentration to a panel of six antibiotics (ampicillin, chloramphenicol, erythromycin, streptomycin, tetracycline, and vancomycin) was recorded. The corresponding genetic determinants responsible were characterised by PCR. Also, the transferability of these resistance markers was assessed in filter mating assays. Of the 37 isolates, 33 were found to be resistant to one or more antibiotics. All strains were susceptible to ampicillin and chloramphenicol. The erm(B) and msrA/B genes were detected among the 11 erythromycin-resistant strains of enterococci, lactobacilli, and streptococci. Two tetracycline-resistant strains, Lactobacillus plantarum and Leuconostoc mesenteroides spp., contained tet(M) and tet(S) genes respectively. Intrinsic streptomycin resistance was observed in lactobacilli, streptococci, lactococci and Leuconostoc species; none of the common genetic determinants (strA, strB, aadA, aadE) were identified. Four of 10 strains of Enterococcus faecium were resistant to vancomycin; however, no corresponding genetic determinants for this phenotype were identified. Enterococcus faecalis strains were susceptible to vancomycin. L. plantarum, L. mesenteroides and Pediococcus pentosaceus were intrinsically resistant to vancomycin. Transfer of antibiotic resistance determinants was demonstrated in one strain, wherein the tet(M) gene of L. plantarum (23) isolated from a pork abattoir was transferred to Lactococcus lactis BU-2-60 and to E. faecalis JH2-2. This study identified the presence of antibiotic resistance markers in Irish meat isolates and, in one example, resistance was conjugally transferred to other LAB strains.     

Effects of intra-articular D-amino acids combined with systemic vancomycin on an experimental Staphylococcus aureus-induced periprosthetic joint infection

BackgroundThe D-isoforms of amino acids (D-AAs) exhibit anti-biofilm potential against a diverse range of bacterial species in vitro, while its role in vivo remains unclear. The aim of this study was to investigate the effects of a combination of D-AAs and vancomycin on a PJI rat model.MethodsEight-week-old male SD rats were randomized to the control group, sham group, vancomycin group, D-AAs–vancomycin group. After treatment for 6 weeks, we analysed the levels of inflammatory factors in serum, behavioural change, imaging manifestations. The anti-biofilm ability of D-AAs was detected by crystal violet staining and scanning electron microscope observation, and its ability to assist antibiotics in killing bacteria was assessed by culture of bacteria. Additionally, micro-CT and histological analysis were used to evaluate the impact of D-AAs combined with vancomycin on the bone remodelling around the prosthesis.ResultsThe group treated with a D-AAs–vancomycin combination sustained normal weight gain and exhibited reduced the serum levels of α2M, IL-1β, IL-6, IL-10, TNF-α and PGE2. Moreover, treated with D-AAs in combination with vancomycin improved the weight-bearing activity performance, increased the sizes and widths of distal femurs, and improved Rissing scale scoring. In particular, treatment using D-AAs enhanced the ability of vancomycin to eradicate Staphylococcus aureus, as demonstrated by the dispersion of existing biofilms and the inhibition of biofilm formation that occurred in a concentration-dependent manner. This treatment combination also resulted in a reduction in bacterial burden with in the soft tissues, bones, and implants. Furthermore, D-AAs–vancomycin combination treatment attenuated abnormal bone remodelling around the implant, as evidenced by an observed increase in BMD, BV/TV, and Tb.Th and the presence of reduced Trap⁺ osteoclasts and elevated osterix⁺ osteo-progenitors.ConclusionsCombining D-AAs with vancomycin provides an effective therapeutic strategy for the treatment of PJI by promoting biofilm dispersion to enhance antimicrobial activity.     

Biofilm Synthesis and other Virulence Factors in Multidrug-Resistant Uropathogenic enterococci Isolated in Northern India

Purpose: Enterococci express high degree of resistance towards wide range of antibiotics. Production of biofilm and many virulence factors along with drug resistance makes it difficult to eradicate the infection from urinary tract. The present study detected the expression of such factors including biofilm production by multidrug-resistant (MDR) enterococci. Materials and Methods: Drug susceptibility of 103 uropathogenic enterococci was performed followed by estimation of minimum inhibitory concentration of high-level gentamicin and vancomycin by microbroth dilution method. Vancomycin-resistant genes were detected by multiplex polymerase chain reaction. Production of virulence factors such as haemagglutination, caseinase, lipase, gelatinase, haemolysin and β-lactamase was detected by phenotypic methods in MDR strains. Biofilm production was detected by calcofluor-white fluorescence staining and semi-quantitative adherence assay. Results: 45% and 18.4% of the isolates were high-level gentamicin-resistant and vancomycin-resistant enterococci (VRE), respectively. vanA gene was detected in 14 and vanB gene in 5 strains. Biofilm, caseinase and gelatinase were the most expressed virulence factor. Expression of caseinase, gelatinase and lipase was significantly higher in Enterococcus faecalis (P < 0.05). Expression of haemagglutination, gelatinase and haemolysin among the vancomycin-resistant isolates was significantly higher (P < 0.05). Conclusion: VanA and vanB are the prevalent genotypes responsible for vancomycin resistance. The high prevalence of MDR enterococcal strains producing biofilm and virulence determinants raises concern. asa1, hyl, esp, gelE, cyl and other genes are known to express these factors and contribute to biofilm formation. Most uropathogenic enterococci expressed biofilm at moderate level and can be detected effectively by calcofluor-white staining. No correlation was noted between vancomycin resistance and biofilm production.     

Vancomycin Resistance: Status Quo and Quo Vadis

 The prevalence of vancomycin resistance is steadily rising among clinical isolates of Enterococcus spp., thereby limiting the treatment options for infections caused by vancomycin-resistant enterococci. The precise nature of the glycopeptide resistance genes has been elucidated, and many studies on gene reservoirs and strain-versus-resistance-gene epidemiology have been performed. The prevalence of vancomycin-resistant enterococci in various clinical and environmental settings in relation to nosocomial and veterinary applications of antimicrobial glycopeptides is discussed in detail in this review. Novel molecular tools for the identification of vancomycin-resistant enterococci genomes or the various resistance genes have been applied in order to expand current insight into the overall epidemiology of the resistance trait itself. The risk of the spread of vancomycin resistance to other bacterial species was recently underscored by the emergence of staphylococci showing clinical resistance to vancomycin. The topics mentioned above are elaborated on and discussed in light of the increasing medical concern on the future detection of microbial infections beyond chemotherapeutic cure.     

Molecular characteristics of vancomycin-resistant Enterococcus faecium from a tertiary care hospital in Chengdu,China

The aim of this study was to characterize vancomycin-resistant Enterococcus faecium (VREfm) isolates phenotypically and molecularly, and investigate associations between the virulence factors enterococcal surface protein (esp), hyaluronidase (hyl), and collagen adhesin (acm) and colonization/infection. A total of 126 E. faecium [66 VREfm and 60 vancomycin-susceptible (VSEfm)] were collected in West China Hospital. Nine E. faecium isolates (7 VREfm and 2 VSEfm) were selected at random for comparative study in a large region from China. Minimum inhibitory concentrations (MICs) were measured by Etest and agar dilution, vancomycin resistance genes (vanA, vanB, and vanC) and virulence genes (esp, acm, and hyl) were detected by polymerase chain reaction (PCR). Thirty-four VREfm underwent repetitive sequence-based PCR (rep-PCR) and multi-locus sequence typing (MLST). One linezolid-resistant isolate (MIC?=?8 μg/ml) was found; none were tigecycline resistant. All 73 VREfm (28 infective strains and 45 intestinal colonizers) had the vanA gene and VanA phenotype. Positivity for esp, hyl, and acm in VREfm was 79.5, 46.6, and 86.3 %, respectively, which was higher than in VSEfm (54.8, 27.4, and 56.5 %, respectively). Among VSEfm, positivity for acm in isolates from pleural or cerebrospinal fluid (84.6 %) was higher than that from blood (32.4 %). There were 11 rep-PCR types (similarity >95 %) and MLST revealed nine sequence types (STs) among the selected isolates. Most VREfm and all VSEfm belonged to clonal complex 17. A new ST was found, with allele sequence (15, 1, 38, 1, 1, 1, 1). In China, most VREfm seem to belong to the classical nosocomial CC17 clone, and many of them have acquired virulence genes, further strengthening a hospital-adapted type.     

Clostridium innocuum is a vancomycin-resistant pathogen that may cause antibiotic-associated diarrhoea

ObjectivesClostridium innocuum can cause extraintestinal infection in patients with underlying diseases. The role of C. innocuum in antibiotic-associated diarrhoea (AAD) remains unknown.MethodsClinical information of 103 patients from whom C. innocuum was isolated was reviewed. We carried out cellular and animal experiments to examine the pathogenic potential of C. innocuum in AAD.ResultsEighty-eight per cent (91/103) of the 103 patients received antibiotics within 2 weeks of diarrhoea onset. Patients were further classified into two groups, severe colitis and diarrhoea, according to clinical severity level. The mortality rate was 13.6% (14/103) among the patients from whom C. innocuum was isolated. The lowest concentrations at which 90% of the isolates were inhibited for metronidazole and vancomycin were 0.5 and 16 mg/L, respectively. All isolates tested were susceptible to metronidazole but resistant to vancomycin. Nineteen randomly selected isolates (ten from severe colitis group, nine from diarrhoea group) were subjected to further in vitro cellular examinations. The level of cytotoxicity to Vero cells was significantly higher in isolates from the severe colitis group at both 24 and 48 hours after inoculation (24 and 48 hours, p 0.042 and 0.033, respectively). We observed apoptotic changes that subsequently led to cell death in C. innocuum–infected Vero cells. Tissue damages, necrotic changes and oedema were observed in the mouse ileal loop infected by C. innocuum.ConclusionsVancomycin-resistant C. innocuum may play a potential role as a causative agent of AAD. The clinical manifestations of AAD caused by C. innocuum were diarrhoea or severe colitis, including pseudomembranous colitis.     

How I manage a patient with MRSA bacteraemia

BackgroundStaphylococcus aureus bloodstream infections are common and associated with a high mortality of 15–25%. Methicillin-resistant S. aureus (MRSA) bloodstream infection accounts for 10–40% of cases, and has an even higher mortality. Despite being the ‘bread and butter’ of clinical infectious diseases practice, robust evidence to guide optimal management is often lacking and there is wide variation in practice.ObjectivesTo provide a real-world example of a case of MRSA bacteraemia and the thought processes of the authors as key management decision points are reached.SourcesThe discussion is based on recent literature searches of relevant topics. In making recommendations, randomized clinical trial data have been prioritized and highlighted, and where these are not available recommendations are based on the experience and opinions of the authors.ContentFor a patient with MRSA bacteraemia and a primary bone and joint infection the following points are discussed: empirical antibiotic choice for suspected S. aureus bacteraemia; directed antibiotic choice for MRSA; monitoring and dosing of vancomycin; the role of combination therapy when bacteraemia is persistent; and the duration of therapy and role of switching to oral antibiotics.ImplicationsWhile broad principles of aggressive source control and appropriate choice and duration of antibiotics are important, the heterogeneity of S. aureus bacteraemia means that a tailored rather than algorithmic approach to management is often required. Further randomized controlled trials are needed to strengthen the evidence base for the management of MRSA bacteraemia.