Antibiotic-resistant enterococci

Comparative analysis of the oral microbiota between iron-deficiency anaemia (IDA) patients and healthy individuals by high-throughput sequencing

Background

The relationship between oral microbiota and IE (infective endocarditis) is well established. Opportunistic pathogens in normal oral flora enter the bloodstream through daily oral cleaning or invasive dental procedures, leading to the occurrence of infective endocarditis. An in vitro iron-deficient condition leads to a drastic community shift in oral microbiota with increasing proportions of taxa related to infective endocarditis. To investigate the relationship among insufficient iron supply, oral microbiota and the risk of IE and to conduct a population amplification study, iron-deficiency anaemia is used as an in vivo model.

Methods

This cross-sectional study enrolled 24 primary iron-deficiency anemia (IDA) patients from 2015.6 to 2016.6 from the hematology department of West China Hospital, Sichuan University, and 24 healthy controls. High-throughput sequencing compared the dental plaque microbiota of 24 IDA (iron-deficiency anaemia) patients and 24 healthy controls.

Results

Sequences were classified into 12 phyla, 28 classes, 50 orders, 161 genera and 497 OTUs (the IDA and control groups shared the same 384 OTUs). Iron deficiency leads to lower internal diversity in the oral flora. The abundances of genera Corynebacterium, Neisseria, Cardiobacterium, Capnocytophaga, and Aggregatibacter were significantly higher in healthy controls, while genera Lactococcus, Enterococcus, Lactobacillus, Pseudomonas and Moraxella showed higher proportions in the IDA group (P < 0.05). The relative abundances of genera Lactococcus, Enterococcus, Pseudomonas and Moraxella were significantly negatively correlated with the concentration of serum ferritin (P < 0.05).

Conclusions

Without an increase of oral streptococci, the main pathogen of IE, it is difficult to determine whether IDA can increase the risk of IE. However, the iron-deficient condition did lead to changes in the oral microbiota community structure. The genera that showed higher proportions in the IDA group were frequently reported as antibiotic-resistant. As antibiotics are commonly recommended to prevent IE before dental procedures, this study offers new ideas of personalized prevention of IE.

Outbreak of infection with high-level gentamicin-resistant Enterococcus faecalis (HLGRE) in a Norwegian hospital

OBJECTIVES

To examine and characterize a suspected outbreak of high-level gentamicin-resistant Enterococcus (HLGRE) infection.

METHODS

Eighty-nine patients with clinical infection diagnosed during hospital stay or within 30 days after discharge in the period from June 1995 to 31 December 1999 were included in the study. One control patient was assigned for each HLGRE patient according to localization in the hospital (same ward), time of admission (+/-3 months), and age (+/-10 years). Unadjusted risk analysis and multivariate logistic regression analysis were performed. Sixty-nine HLGRE strains were subjected to PCR amplification of the genes coding for aminoglycoside-3'-O-phosphoryltransferase-III (APH(3')-III) and aminoglycoside-6'-N-acetyltransferase/2"-O-phosphoryltransferase-III (AAC(6')/APH(2")).

RESULTS

The gene aacA/aphD, associated with HLGRE, was detected by PCR in all isolates, and the gene aphA3, associated with high-level streptomycin, kanamycin and amikacin resistance, was detected in 56 of the 69 isolates. None of the 69 isolates was resistant to glycopeptides or ampicillin. Resistance to ciprofloxacin was found in 57 (82.6%). Pulsed-field gel electrophoresis analysis revealed 12 different genotypes, among which two major clusters dominated.

CONCLUSIONS

Both clonal expansion and the emergence of unique strains contributed to the increased number of infections caused by HLGRE. Urinary catheterization, duration of hospital stay and antibiotic therapy were significant risk factors for HLGRE infection.

Treatment of vancomycin-resistant Enterococcus faecium infections with quinupristin/dalfopristin

Clinicians caring for patients with vancomycin-resistant Enterococcus faecium (VREF) infections face severe constraints in the selection of treatment. Quinupristin/dalfopristin (Synercid) is active in vitro against VREF, with a MIC(90) of 1.0 microg/mL. We investigated the clinical efficacy and safety of this agent in a multicenter, prospective, noncomparative, emergency-use study of 396 patients. Patients were included if they had signs and symptoms of active infection, including bacteremia of unknown origin, intra-abdominal infection, and skin and skin-structure infection, with no alternative antibiotic therapy available. The mean duration of treatment was 20 days (range, 4-40 days). The clinical response rate was 68.8% in the evaluable subset, and the overall response rate was 65.6%. The most common adverse events related to quinupristin/dalfopristin were arthralgias and myalgias. Related laboratory abnormalities were rare. In this severely ill patient population, quinupristin/dalfopristin was efficacious and demonstrated an acceptable safety profile in the treatment of VREF infection.

Identification of plant-associated enterococci

AIMS

Enterococcus isolates from forage grass were subjected to taxonomical investigations and tested for antibiotic resistance.

METHODS AND RESULTS

The identification procedure included phenotypic characterizations, restriction analyses of polymerase chain reaction-amplified 16S rDNA, whole-cell protein profile analyses and 16S rDNA sequence analyses. Agar diffusion tests were performed to detect antibiotic resistance.

CONCLUSION

The isolates were identified as belonging to the species Enterococcus faecium, Ent. mundtii, Ent. casseliflavus, Ent. faecalis and Ent. sulfureus. However, the majority of isolates differed distinctly in their restriction patterns from those of known species. They formed a group of a homogeneous 16S rDNA genotype (VI). The 16S rDNA sequence of a representative isolate revealed the closest relationship to the species Ent. faecalis (similarity of 97.4%). All isolates were sensitive to vancomycin, but almost all were resistant to gentamycin and streptomycin.

SIGNIFICANCE AND IMPACT OF THE STUDY

The taxonomical investigations suggest that the isolates of the 16S rDNA genotype VI represent a new plant-associated Enterococcus species.

Isolation and characterization of glycopeptide-resistant enterococci from hospitalized patients over a 30-month period

In February 1996, a Hospital Infection Control Practices Advisory Committee-style screening program was commenced to isolate and subsequently characterize glycopeptide-resistant enterococci (GRE) from patients at a hospital trust in Glasgow, Scotland. Over the next 30 months, GRE were isolated from 154 patients. GRE were isolated from patients in traditionally high-risk areas such as the renal unit and intensive care unit and also in areas considered to be lower risk, including medical wards and associated long-stay geriatric hospitals. The majority (90%) of isolates were Enterococcus faecium vanB. The remaining isolates consisted of seven E. faecalis (vanA), three E. gallinarum (vanC), and a further six E. faecium (five vanA, one both vanA and vanB) isolates. Analysis of SmaI-digested DNA by pulsed-field gel electrophoresis revealed that 34 of 40 (85%) VanB E. faecium isolates were identical or closely related, while 11 of 13 (85%) VanA GRE were distinct. High-level aminoglycoside resistance was seen in less than 8% of isolates. VanB E. faecium isolates were almost uniformly resistant to ampicillin and tetracycline. In this study, GRE have been isolated over a prolonged period from a broad range of patients. Glycopeptide resistance within the study hospital trust appeared to be mainly due to the clonal dissemination of a single strain of E. faecium VanB.

Morphologic changes correlating to different sensitivities of Escherichia coli and enterococcus faecalis to Nd:YAG laser irradiation through dentin

BACKGROUND AND OBJECTIVE

Previous studies demonstrated the disinfecting potential of Nd:YAG laser irradiation on the root canal system from an overall quantitative viewpoint. The aim of this study was to evaluate the specific effect of irradiation through dentin on gram-negative and gram-positive bacteria with regard to their cell structure.

STUDY DESIGN/MATERIALS AND METHODS

Sterile dentin samples of standardized size were divided into two sets of four groups with eight samples each. The first set was inoculated with Escherichia coli as the gram-negative test strain, the second set was inoculated with Enterococcus faecalis, which served as the gram-positive test organism. The samples were then irradiated on the bacteria-free side in contact mode under constant scanning movement at an angle of 10 degrees by use of the fiber optic of the Nd:YAG laser. Upon laser treatment they were critical point dried and subjected to SEM investigation. Another two sets of samples were prepared and irradiated in the same manner and evaluated by standard microbiological procedures to verify whether the observed morphologic alterations correlated to cell death.

RESULTS

SEM investigations revealed damage pattens that increased with the amount of energy applied. Whereas the gram-negative test organism showed immediate structural injury, the gram-positive test organism required repeated application of irradiation. The microbiological examination showed reduction of both bacterial strains, yet to different extents.

CONCLUSION

Our study demonstrates the different morphologic impact of Nd:YAG laser irradiation through dentin on representatives of the two main groups of bacteria. It shows that the construction of the cell wall is crucial for their individual sensitivity to laser treatment.

First confirmed case of a vancomycin-resistant Enterococcus faecium with vanA phenotype from Brazil: isolation from a meningitis case in São Paulo

The importance of enterococci as a nosocomial etiologic agent is well documented; however, enterococci are also capable of causing a variety of community-acquired infections. Vancomycin resistance in a clinical Enterococcus isolate was first reported in 1986, and since then vancomycin-resistant enterococci (VRE) have been reported world-wide. This report describes a case of E. faecium with the VanA phenotype, isolated from meningitis in Sao Paulo, Brazil. Two E. faecium strains were isolated. One strain showed VanA phenotype, and the molecular characterization of the VanA gene was confirmed by polymerase chain reaction. The other strain was susceptible to vancomycin and teicoplanin. The authors would like to call the attention of the scientific community to this first identification of a VRE case in Sao Paulo, Brazil.

Mopping up hospital infection

Hospital cleaning is a neglected component of infection control. In the UK, financial constraints have forced managers to re-evaluate domestic services and general cleaning has been reduced to the bare minimum. Services have been contracted out in some hospitals, which has further lowered standards of hygiene. Control of infection personnel believe that cleaning is important in preventing hospital-acquired infections but they do not manage domestic budgets and have failed to stop their erosion. It is difficult to defend high levels of hygiene when there is little scientific evidence to support cleaning practices. This review examines the common micro-organisms associated with hospital-acquired infection and their ability to survive in the hospital environment. It also describes studies which suggest that comprehensive cleaning disrupts the chain of infection between these organisms and patients. It is likely that restoring hygienic standards in hospitals would be a cost-effective method of controlling hospital-acquired infection. Furthermore, good cleaning is achievable whereas the enforcement of hand washing and good antibiotic prescribing are not.

Isolation and molecular characterization of vancomycin-resistant Enterococcus faecium in Malaysia

Nineteen strains of vancomycin-resistant Enterococcus faecium isolated from 10 of 75 (13.3%) tenderloin beef samples were examined for resistance to selected antibiotics, presence of plasmids, and genetic diversity by random amplification of polymorphic DNA analysis. All strains showed multiple resistant to the antibiotics tested. Multiple antibiotic indexing of the vancomycin-resistant E. faecium strains showed that all (100%) originated from high risk contamination environments where antibiotics were often used. Plasmids ranging in size from 1.5 to 36 megadalton were detected in 15 of 19 (79%) strains. Thus, three plasmid profiles and eight antibiotypes were observed among the E. faecium strains. A high degree of polymorphism was obtained by combining the results of the two primers used; with the 19 E. faecium strains being differentiated into 19 RAPD-types. These preliminary results suggest that RAPD-PCR has application for epidemiologic studies and that resistance patterns and plasmid profiling could be used as an adjunct to RAPD for the typing of E. faecium in the study area.

An interprovincial external quality assessment of the ability of Canadian laboratories to detect the vancomycin and penicillin resistance of Enterococcus faecium D366

OBJECTIVE: To evaluate the ability of Canadian laboratories to identify enterococci and detect low-level resistance to penicillin, ampicillin and vancomycin in five provinces and two territories by two external quality assessment schemes. METHODS: Enterococcus faecium, strain D366, with minimum inhibitory concentrations for vancomycin and penicillin of 32 and 16 mg/L respectively, was distributed during a routine proficiency survey. Laboratories were required to culture and identify the isolate and to test antimicrobial susceptibility. Participants were assessed against consensus reference values. RESULTS: Three hundred and sixty-four hospital, commercial and public-health laboratories participated, using their established procedures for patient samples. The isolate was identified to the species level by 222 (61%) laboratories and to the genus level by a further 98 participants. Forty-four failed to meet the expected standard. Vancomycin resistance was detected by 94%. Those reporting a falsely susceptible result used disk diffusion testing. Penicillin resistance was noted by 250 of 258 laboratories reporting on this agent. An incorrect ampicillin-susceptible finding was reported by 62 of 147 laboratories using automated microdilution or agar dilution methods. CONCLUSIONS: Most laboratories identified the isolate to an appropriate level. Detection of low-level vancomycin and penicillin resistance was achieved by the majority. Ampicillin resistance was less readily detected.

Enterococcal bacteremia in children: a review of seventy-five episodes in a pediatric hospital

BACKGROUND

Enterococcal bacteremia is being increasingly reported. Although there have been a number of recent studies of enterococcal bacteremia in adults, there are few studies involving children. We carried out a prospective study to determine the epidemiologic, clinical and laboratory characteristics of such bacteremia in children.

METHODS

Clinical and microbiologic data were recorded prospectively for all episodes of enterococcal bacteremia occurring during a 3-year period between January 1, 1995, and December 31, 1997.

RESULTS

Seventy-five episodes of enterococcal bacteremia occurring in children at our institution during a 3-year period were prospectively analyzed. Serious underlying disease was present in 67 (89.3%) episodes, and in 48 (64.%) episodes patients had received antibiotics during the 2 weeks preceding enterococcal bacteremia. Forty-seven (62.7%) episodes were nosocomial in origin and 26 (34.7%) were polymicrobial. Fifty (66.7%) episodes occurred in children 1 year old or less. A source of bacteremia was identified in 33 (44%) episodes, intravascular device being the most common identifiable source. Of the 73 isolates identified to species level, there were 36 Enterococcus faecium, 36 Enterococcus faecalis and one Enterococcus avium. In 60 (80%) episodes appropriate anti-enterococcal therapy was given. The overall mortality rate was 7.5%. Four clinical patterns of infection were identified: self-limited bacteremia, 16.0%; low grade sepsis with a favorable outcome after specific therapy, 65.3%; severe and prolonged infection associated with a high mortality rate, 14.7%; and fulminant neonatal sepsis in previously healthy babies, 4.0%.

CONCLUSION

Enterococcal bacteremia in children comprises a heterogeneous group. Bacteremias that are mild and self-limited and respond promptly to antibiotic therapy appear to be more common in children.

Vancomycin-resistant Enterococcus faecium in a Veterans Affairs Medical Center: association with antibiotic usage

BACKGROUND

Colonization and infection with vancomycin-resistant Enterococcus faecium (VREF) has been associated with the use of vancomycin and other antibiotics in individual patients. The objective of this study was to determine the association of VREF with the aggregate usage of antibiotics on nursing units in a hospital.

METHODS

This was a retrospective correlation study. A usage ratio was calculated for each parenteral antibiotic on each nursing unit as the per-bed usage by weight of that antibiotic divided by its average usage throughout the hospital. An average usage ratio (AUR) for each nursing unit was calculated as the mean of usage ratios of individual antibiotics. The AUR was used to compare the usage of antibiotics among nursing units in the hospital. The incidence of VREF infections on individual nursing units in a Veterans Affairs Medical Center was correlated with the usage of parenteral antibiotics separately and in aggregate in univariate and multivariate regression analyses.

RESULTS

The AUR was strongly and positively correlated with the recovery of VREF on individual nursing units. By univariate analyses, increasing use of each antibiotic tested was associated with isolation of VREF but only clindamycin remained significant in the multivariate model. However, usage of various antibiotics was highly interrelated, and only clindamycin usage was significantly correlated with usage of all other antibiotics studied. Intensive care and acute care units and units with fewer patient beds were more likely to have patients with VREF infection than were subacute care units (p < 0.003) or larger units (p < 0.01).

CONCLUSIONS

VREF infections were associated with greater aggregate antibiotic use on nursing units. Determination of antibiotic usage ratios may provide a convenient and useful tool for examining the association of antibiotic usage with other nosocomial infections.

Counting the cost: hospital versus home central venous catheter survival

We compared catheter survival and sepsis rates in a tertiary paediatric gastroenterology centre with those at home in the same patients. We examined whether there were differences in the safety in the two locations, and estimated the financial and opportunity cost implications of any difference. We used survival analysis to analyse differences. Surgical records were audited to determine venous access workload, and to estimate cost implications. Twenty patients with chronic intestinal failure but stable parenteral nutrition requirements, ranging from 0.04-15.83 years of age were studied. The duration of line survival and sepsis-free intervals and rates of re-operation for venous access were determined to estimate morbidity and costs. The study encompassed 28 patient-years in hospital and 48 patient-years at home. There was a significant reduction in the rate of sepsis at home compared with hospital (Z = 4.30, P < 0.00001), and a similar improvement in line survival (Z = 4.36, P < 0.00001). Line insertions accounted for 21% of minor surgery in our hospital, one third being reinsertions. We conclude that central venous catheter sepsis rates are greatly improved at home. If home results could be achieved in the hospital setting, considerable cost savings would be made.

Surveillance of infections in hospital: agents and antibiotic-resistance

The surveillance system for Hospital Acquired Infections (HAI) implemented in the S. Eugenio hospital of Rome allows to monitor the distribution of the micro-organisms by service and their resistance to antibiotics. It is based upon the data collected by the Central Analysis Laboratory of the hospital. The data of four high-risk departments (Surgical service, Intensive Care Unit, Haematology, Burn Unit) are reported. In the period October 1992-September 1993, 3909 samples have been analyzed; 1603 (43.1%) were found positive to the microbiologic analysis. The results of the antibiotic resistance concerning four micro-organisms, agents of HAI are reported and discussed. Surveillance systems are necessary to limit the frequency of HAI.

Epidemiology of an outbreak due to glycopeptide-resistant Enterococcus faecium on a leukaemia unit

The clinical and molecular epidemiology of two clusters of colonization and infection of patients by glycopeptide-resistant enterococci (GRE) on a leukaemia and bone marrow transplantation unit was studied over a two-and-a half-year period. Thirty-five patients became colonized, of whom six developed clinical infections. Of the 53 isolates of GRE, 49 were Enterococcus faecium, multiply-resistant to vancomycin and ampicillin. DNA fingerprinting of 48 E. faecium isolates by pulsed-field gel electrophoresis identified six DNA types. One strain of VanB phenotype E. faecium predominated during the initial outbreak, and an unrelated strain of the VanA phenotype was present in a second cluster. Environmental and patient isolates of E. faecium were indistinguishable by DNA typing. The VanA phenotype enterococci probably arose by transfer from the renal ward at a nearby hospital, and a patient with persistent diarrhoea may have contributed to contamination and cross-infection. GRE may cause significant infections in immunocompromised patients, and are readily transmitted between them. GRE were controlled, but not eradicated on the unit; infection control measures included improved environmental cleaning and modification of antibiotic use. In order to control GRE, it is necessary to educate healthcare workers and implement the traditional, effective values of good personal hygiene and environmental cleanliness.

Evaluation of commercial vancomycin agar screen plates for detection of vancomycin-resistant enterococci

Brain heart infusion-6-micrograms/ml vancomycin agar plates obtained from five commercial sources (B-D Microbiology Systems, Carr-Scarborough Microbiologicals, MicroBio Products, PML Microbiologicals, and REMEL) were evaluated with 714 enterococci for detection of vancomycin resistance. All 465 (100%) vancomycin-resistant enterococci (MIC > or = 32 micrograms/ml) were detected by each manufacturer's agar screen plate, and each manufacturer's agar screen plate detected at least 99% of the 177 vancomycin-susceptible enterococci (MIC < or = 4 micrograms/ml). Detection of the 72 vancomycin-intermediate enterococci (MIC = 6 to 16 micrograms/ml) ranged from 94% for B-D Microbiology Systems to 99% for PML Microbiologicals.

Selective isolation of vancomycin-resistant enterococci

Broth formulations of two media selective for enterococci, Enterococcel, M-Enterococcosel broths were supplemented with 6 micrograms of vancomycin per ml and evaluated for isolation of vancomycin-resistant enterococci (VRE). Each broth was challenged with various concentrations of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and vancomycin-susceptible and vancomycin-resistant enterococci and with 193 perianal specimens obtained from patients at risk in our institution for VRE colonization. Both the Enterococcosel and M-Enterococcus broths with vancomycin detected as few as 1 to 9 CFU of VRE while inhibiting growth of the other organisms tested. Enterococcus faecium organisms (MIC, > 256 micrograms/ml) were recovered from 66 perianal swab cultures in the enterococcosel-vancomycin broth, and VRE were recovered from 62 perianal swab cultures in the M-Enterococcus-vancomycin broth. Enterococcosel-vancomycin broth detected VRE in perianal specimens 48 h earlier than did M-Enterococcus-vancomycin broth. Enterococcosel broth with 6 micrograms of vancomycin per ml can be used for the rapid and selective isolation of VRE from surveillance specimens.

Selective medium for screening for vancomycin-resistant enterococci in faeces

Infections caused by vancomycin-resistant enterococci (VRE) are becoming increasingly prevalent throughout the world. Control measures include detection and isolation of carriers of VRE. A selective medium to detect faecal carriage of VRE is described. The medium has a high productivity ratio (90.4%) for VRE with VanA resistance phenotype, a moderate productivity ratio (79.2%) for VRE with VanB resistance phenotype, and a relatively low productivity ratio (65.5%) for VRE with VanC resistance phenotype. There was no breakthrough of vancomycin-susceptible enterococci. The medium selected the growth of all three types of VRE, which were used to spike faecal specimens. In a limited clinical trial, six faecal specimens of carriers and contacts were screened using the selective medium. Vancomycin-resistant enterococci (Enterococcus faecalis, VanA phenotype) were detected in four of the specimens. In all four specimens the growth of VRE was nearly pure and easily identifiable.

Current perspectives on glycopeptide resistance

In the last 5 years, clinical isolates of gram-positive bacteria with intrinsic or acquired resistance to glycopeptide antibiotics have been encountered increasingly. In many of these isolates, resistance arises from an alteration of the antibiotic target site, with the terminal D-alanyl-D-alanine moiety of peptidoglycan precursors being replaced by groups that do not bind glycopeptides. Although the criteria for defining resistance have been revised frequently, the reliable detection of low-level glycopeptide resistance remains problematic and is influenced by the method chosen. Glycopeptide-resistant enterococci have emerged as a particular problem in hospitals, where in addition to sporadic cases, clusters of infections with evidence of interpatient spread have occurred. Studies using molecular typing methods have implicated colonization of patients, staff carriage, and environmental contamination in the dissemination of these bacteria. Choice of antimicrobial therapy for infections caused by glycopeptide-resistant bacteria may be complicated by resistance to other antibiotics. Severe therapeutic difficulties are being encountered among patients infected with enterococci, with some infections being untreatable with currently available antibiotics.

Use of primers selective for vancomycin resistance genes to determine van genotype in enterococci and to study gene organization in VanA isolates

Vancomycin resistance in enterococci is an emerging therapeutic problem. Resistance is not always detected by standard microbiological methods. Oligonucleotide primers for PCR were designed to target amplification of defined regions of genes of the vanA cluster, as well as vanB and vanC1. These primers correctly identified 30 vancomycin-resistant isolates tested (17 VanA, 7 VanB, and 6 Enterococcus gallinarum). No amplification was observed with Enterococcus casseliflavus or vancomycin-susceptible strains. Using PCR and Southern blotting, we found that all 17 VanA isolates had orf-1, orf-2, vanR, vanS, vanH, vanA, and vanY genes in the same sequence and that the intergenic distances in the vanR-vanA segments were the same. The described methods should be applicable to the rapid detection of the different vancomycin resistance genotypes in enterococci.

Use of cephalexin-aztreonam-arabinose agar for selective isolation of Enterococcus faecium

Cephalexin-aztreonam-arabinose agar (CAA), a new selective agar, was examined in comparison with nalidixic acid-colistin agar for the differentiation of Enterococcus faecium from other enterococci and the ability to isolate the organism from feces. Two hundred sixteen enterococcus isolates and a variety of gram-positive and gram-negative control strains were inoculated onto both media. All control strains of E. faecium were easily differentiated from Enterococcus faecalis and Enterococcus durans on the basis of arabinose fermentation on CAA. Differentiation of E. faecium from other enterococci or Streptococcus bovis was not possible on nalidixic acid-colistin agar. Increased isolation of E. faecium was demonstrated on CAA when both media were compared for the isolation of the organism from feces. CAA has been shown to possess excellent differential and selective features allowing the simple and effective isolation of E. faecium from heavily contaminated sites.

Molecular epidemiology of gastric colonization by Enterococcus faecalis in a surgical intensive care unit

We applied restriction endonuclease analysis of genomic DNA using pulsed field gel electrophoresis (PFGE) to study gastric colonization with Enterococcus faecalis among patients hospitalized in the surgical intensive care unit (SICU). Isolates were obtained by culturing prospectively the gastric contents of 140 patients in the SICU. In addition, cultures of respiratory specimens were obtained daily and cultures of blood, normally sterile body fluids, wounds, and urine were obtained when indicated clinically. A total of 177 isolates were obtained from 45 patients. Concentrations of E. faecalis in gastric fluid ranged from 1 x 10(2) colony forming units (CFU)/ml to greater than 5 x 10(7) CFU/ml (mean 8.0 x 10(6) CFU/ml). Overall, 33 different DNA types were identified by PEGE. In examining strain variation among isolates obtained from multiple anatomic sites over time, we found that the same DNA type was recovered from gastric aspirates, sputum, and wounds in a given patient and that these strains were carried over time. In general, given individuals were colonized with their own unique DNA type; however, one DNA type (type C) was shared by 11 different patients, and seven DNA types were shared by two individuals each. These results demonstrate the potential importance of gastric colonization as a reservoir for nosocomial strains of E. faecalis in an SICU setting.

Nosocomial infection due to enterococci attributed to a fluidized microsphere bed. The value of pyrolysis mass spectrometry

The potential of fluidised microsphere beds as sources of nosocomial Enterococcal infection was investigated with the help of pyrolysis mass spectrometry. Isolates from clinical specimens collected from two patients who were nursed sequentially on a fluidized microsphere bed were compared with similar isolates cultured from the microspheres before and after decontamination. Pyrolysis mass spectrometry confirmed that nosocomial spread had indeed occurred and that the existing decontamination process was inadequate. Recommendations for improvements to this decontamination process appear to have prevented further cases.

Enterococcal bacteraemia: a prospective study of 125 episodes

One hundred and twenty-five episodes of enterococcal bacteraemia occurring over a 50-month period were studied prospectively. Enterococcus faecium was the commonest species, accounting for 76 (59.8%) of the 127 isolates. Overall, 33.1% of isolates were resistant to ampicillin and one isolate (0.8%) to vancomycin; high-level gentamicin resistance was detected in 4.3% of 93 isolates tested. The percentage of nosocomial episodes was 70.4, and 95.2% of the patients had significant underlying illness. Central venous catheters (CVCs) were the commonest source of infection. Eighty-four per cent of episodes were ultimately treated with appropriate antibiotics. The overall mortality rate was 17.6%, and that directly attributable to infection was 8.0%. An increased mortality rate was observed in intensive care and neonatal unit patients, and in patients who had received antimicrobial therapy in the 2 weeks prior to enterococcemia. CVC-related infections were associated with a reduced mortality. No other clinical or microbiological factors were found to influence outcome.

Impact of the agar medium and disc type on disc diffusion susceptibility testing against teicoplanin and vancomycin

Susceptibility to teicoplanin and vancomycin was assessed by three disc types: two commercially available discs (NeoSensitabs and PDM disc (30 micrograms)) and one locally prepared 30 micrograms disc (SS disc) on four different medium types: Mueller-Hinton agar (MH medium), MH medium and PDM agar II supplemented with 5% horse blood (HMB medium and PDM medium, respectively), and Danish blood agar (DBA medium). Two previously studied groups of Gram-positive bacteria were tested: group B (N = 75) comprised miscellaneous cocci, and group C (N = 59) mostly rods. With NeoSensitabs, mean zone diameters were larger than with PDM and SS discs on all medium types, and mean zone diameters were larger on DBA medium than on MHB and PDM medium with all disc types. The impact of the medium type on the zone diameter was evaluated for 121 strains growing on MHB medium, PDM medium, and DBA medium. Bacterial groups B and C each divided into three MIC groups were analysed separately. We compared mean zone diameters for each specific group with the average zone diameter, i.e. the mean value for all zone diameters obtained. The smallest deviations from the average zone diameters were observed on PDM medium for both teicoplanin and vancomycin. Thirty-seven percent of strains failed to grow on MH medium, but supplementation of MH medium with horse blood significantly reduced the zone diameter for group B strains both for teicoplanin and vancomycin. Poor predictability of MIC from the zone diameter was found especially for strains with MICs < or = 1 microgram/ml. The medium type hardly affected the results of regression analysis. In contrast, the medium type markedly affected the results of error-rate bounded analysis. No errors were recorded with the SS disc on MHB medium for either teicoplanin or vancomycin, but no strains with MICs of vancomycin within the intermediate group could be correctly classified on DBA medium.

The emergence of vancomycin resistance in renal dialysis

Intraperitoneal vancomycin is used in the treatment of peritonitis in patients undergoing continuous ambulatory peritoneal dialysis (CAPD). We describe the emergence of low-level glycopeptide-resistance in five Gram-positive species over a one-year period. Isolation of these organisms was associated with vancomycin treatment failure in four patients who had had numerous episodes of peritonitis. Clinicians and microbiologists should be aware that repeated administration of glycopeptides to such patients might lead to the emergence of organisms resistant to these antibiotics.

Environmental strains of Enterococcus faecium with inducible high-level resistance to glycopeptides

High-level resistance to glycopeptides in Enterococcus faecium is associated with an inducible 39-kDa cytoplasmic membrane protein. The present paper shows that such glycopeptide-resistant E. faecium strains can not only be isolated in a definite clinical setting but also from waste water of sewage treatment plants. Nearer characterization of these and of clinical isolates by resistance pattern, biotyping, and genotyping (DNA-fingerprinting with pulsed-field gel electrophoresis) has shown that different glycopeptide-resistant E. faecium strains have been isolated from clinical sources and from waste water.