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M J Zervos

Publications and source records attributed to M J Zervos.

At least 19 recordsLinked to original sources
PubMed1997

A novel gentamicin resistance gene in Enterococcus.

Enterococcus gallinarum SF9117 is a veterinary isolate for which the MIC of gentamicin is 256 micrograms/ml. Time-kill studies with a combination of ampicillin plus gentamicin failed to show synergism against SF9117. A probe representing aac(6')-aph(2") did not hybridize to DNA from SF9117. A 3.2-kb fragment from plasmid pYN134 of SF9117 was cloned and conferred resistance to gentamicin in Escherichia coli DH5 alpha. Nucleotide sequence analysis revealed the presence of a 918-bp open reading frame whose deduced amino acid sequence had a region with homology to the C-terminal domain of the bifunctional enzyme AAC(6')-APH(2"). The gene is designated aph(2")-Ic, and its observed phosphotransferase activity is provisionally designated APH(2")-Ic. An intragenic probe hybridized to the genomic DNA from an Enterococcus faecium isolate from the peritoneal fluid of one patient and to the plasmid DNA of an Enterococcus faecalis isolate from the blood of another patient. An enterococcal isolate containing this novel resistance gene might not be readily detected in clinical laboratories that use gentamicin at 500 or 2,000 micrograms/ml for screening for high-level resistance.

Amino Acid Sequence↗
PubMed1997

The effect of Tn916 insertions on contour-clamped homogeneous electrophoresis patterns of Enterococcus faecalis.

Contour-clamped homogeneous gel electrophoresis has increasingly been used and has generally been considered the method of choice for the delineation of enterococcial strains. It has been suggested that the contour-clamped homogeneous electric field (CHEF) electrophoresis digestion patterns of genomic DNA indicate the relatedness of strains when SmaI patterns differ by six or fewer bands. To evaluate the potential reasons for the diversity of bands among clonally related isolates, we studied plasmid-free Enterococcus faecalis FA2-2 and derivatives with transposon Tn916 (encoding for tetracycline resistance) insertions on the chromosome. We obtained derivatives with seven different Tn916 insertion sites and up to two copies of Tn916 on the chromosome, resulting in differences of one to seven bands by CHEF electrophoresis; eight different patterns were observed. With Tn916 insertions, there was either (i) loss of a band(s) with the generation of a new band(s), (ii) the generation of a new band(s) only, or (iii) the loss of a band(s) with no new visible band(s). These results indicate that strains can have up to seven different SmaI bands by CHEF electrophoresis and still be closely related.

Bacterial Typing Techniques↗
PubMed1996

Comparative in vitro activity of quinupristin/dalfopristin against multidrug resistant Enterococcus faecium.

The in vitro susceptibilities of 82 strains of vancomycin resistant Enterococcus faecium (VREF), (49 vanA and 33 vanB) from over 13 hospitals in Europe and United States were studied. The MIC for several antibiotics showed high levels of resistance to vancomycin, ampicillin, gentamicin, and imipenem. All VREF strains were highly susceptible to quinupristin/dalfopristin with a MIC 90% of 0.5 microgram/ml for both vanA and vanB phenotypes. Time-kill and synergy studies of VREF for quinupristin/dalfopristin alone and quinupristin/dalfopristin in combination with several antibiotics (ampicillin, gentamicin, ciprofloxacin, rifampin and novobiocin) did not show bactericidal activity. In induction experiments using SF6550, (VREF, a vanA strain), quinupristin/dalforpristin showed a delay in the expression of vancomycin resistance by 2.5 hours. The results of this study show quinupristin/dalfopristin to have excellent in vitro activity versus multiple resistant E. faecium.

Anti-Bacterial Agents↗
PubMed1996

Control of endemic glycopeptide-resistant enterococci.

OBJECTIVE: To evaluate the epidemiology of, and control measures for, vancomycin-resistant Enterococcus (VRE) in a renal unit. DESIGN: A 3-month, prospective, prevalence culture survey of patients on a 24-bed renal unit. SETTING: A 975-bed community teaching hospital. PATIENTS: Patients admitted to the renal unit over a 3-month period. Patients identified with VRE were each matched with four patients without VRE isolated over the study period. INTERVENTIONS/CONTROL MEASURES: Resistant-organism barrier precautions. To eradicate carriage of VRE, two patients with VRE stool colonization were treated with 5 days of oral doxycycline (100 mg twice per day) and rifampin (300 mg/day). RESULTS: Seven patients with VRE (8 isolates) were identified. Five isolates were Enterococcus faecium (vancomycin MIC = 16 to 256 micrograms/mL), two were Enterococcus faecalis (MICs = 16 and 124 micrograms/mL), and one was Enterococcus gallinarum (MIC = 8.0 micrograms/mL). Eradication of carriage with VRE was accomplished in two patients treated with doxycycline and rifampin. In the final 30 days of the culture survey and at 9 months, there were no further patients with VRE identified. CONCLUSIONS: Resistant-organism precautions and elimination of patient carriage may be useful measures for controlling the spread of low-prevalence endemic vancomycin-resistant Enterococcus.

Adult↗
PubMed1996

DNA analysis in the study of fungal infections in the immunocompromised host.

Fungal infections, most of which are caused by the Candida species, are an increasing problem in the immunocompromised host. The clinical manifestations of Candida infections include disseminated candidiasis, oral and esophageal infections, focal hepatic infections, peritoneal urinary tract infections, and wound infections. DNA methods, which include pulse field electrophoresis and restriction enzyme analysis of genomic DNA, have been used to increase understanding of the epidemiology of these infections. These techniques have shown that most Candida infections are endogenous or acquired from one's own flora. Recent outbreaks have provided evidence for exogenous acquisition of some isolates. Better methods for differentiation of colonization versus infection and identifying infection in the absence of positive cultures are under investigation.

Adult↗
PubMed1995

Controlling vancomycin-resistant enterococci.

After controlling an epidemic of vanB-type vancomycin-resistant Enterococcus faecium (VRE), we contained a subsequent vanA E faecium outbreak by using prospective laboratory-based surveillance, placing patients with VRE in private rooms, requiring the use of both gowns and gloves by all personnel entering the patients' rooms, and conducting prevalence surveys of patients on affected wards.

Anti-Bacterial Agents↗
PubMed1995

Characterization of antimicrobial resistance in enterococci of animal origin.

Among 97 enterococci cultured from animals, gentamicin MICs were > or = 2,000 micrograms/ml for 9 isolates and between 250 and 1,024 micrograms/ml for 6 isolates. For two isolates tested (gentamicin MICs, 256 and 512 micrograms/ml, respectively), there was no in vitro synergy with penicillin plus gentamicin, resistance was transferable, and there was no hybridization with a probe specific for 6'-aminoglycoside acetyltransferase-2"-aminoglycoside phosphotransferase. The results of the study indicate the presence of a unique gentamicin resistance genotype in enterococci of animal origin.

Animals↗
PubMed1995

DNA hybridization and contour-clamped homogeneous electric field electrophoresis for identification of enterococci to the species level.

In this study, 113 Enterococcus faecium, 37 Enterococcus faecalis, 24 Enterococcus gallinarum, 15 Enterococcus raffinosus, and 13 Enterococcus casseliflavus clinical isolates and American Type Culture Collection (ATCC) strains were evaluated by contour-clamped homogeneous electric field electrophoresis. Thirty-one of the E. faecium, 22 of the E. faecalis, 24 of the E. gallinarum, 15 of the E. raffinosus, and 13 of the E. casseliflavus isolates were also evaluated by DNA-DNA hybridization. Genomic DNAs from type strains E. faecalis ATCC 19433, E. faecium ATCC 19434, E. gallinarum ATCC 49573, E. raffinosus ATCC 49427, and E. casseliflavus ATCC 25788 were labeled with biotin for use as probes. E. faecalis differed from all other species in always having a largest fragment of > 400 kb. E. gallinarum was different from all other species in having all SmaI fragments of < 200 kb. Biotin-labeled probes showed a high degree of hybridization with genomic DNA from the same species and a low degree of hybridization when hybridized to genomic DNA from different species for all isolates tested except for four isolates identified as E. faecium by conventional biochemical methods. The DNA from these four isolates hybridized strongly to DNA from E. gallinarum ATCC 49573 and weakly to E. faecium ATCC 19434 DNA and had all SmaI fragments of < 200 kb in size. These data suggest that these isolates are nonmotile E. gallinarum. DNA from each ATCC type strain hybridized strongly with itself and had only a low degree of hybridization with DNA from other ATCC type strains tested. These results suggest that contour-clamped homogeneous electric field electrophoresis patterns and DNA-DNA hybridization with biotin-labeled probes may be of use for species differentiation of some enterococci.

Blotting, Southern↗
PubMed1995

Comparison of field inversion gel electrophoresis with contour-clamped homogeneous electric field electrophoresis as a typing method for Enterococcus faecium.

Direct comparisons between contour-clamped homogeneous electric field (CHEF) electrophoresis and field inversion gel electrophoresis (FIGE) to determine the epidemiology of antibiotic-resistant enterococci have not been previously published. Fifty non-beta-lactamase-producing, ampicillin-resistant Enterococcus faecium isolates and 10 vancomycin-resistant E. faecium strains collected from multiple centers were analyzed in a blinded fashion by CHEF electrophoresis and FIGE after digestion with SmaI. Isolates were considered clonally related if there was a difference of three of fewer bands between electrophoretic patterns. Agreement between CHEF electrophoresis and FIGE was seen for 12 of 13 identified groups of ampicillin-resistant E. faecium and 7 of 7 groups of vancomycin-resistant E. faecium. The lone discordance was accounted for by a fourth band difference between two strains recognized near 350 kb by CHEF electrophoresis but not by FIGE, placing them into different clonal groups. Better band separation was noted in the 50- to 200-kb range for FIGE, while CHEF electrophoresis revealed better resolution over 250 kb more reliably, including detection of some bands not seen on FIGE. Molecular epidemiologic investigations of E. faecium by either technique should provide comparable results.

Ampicillin Resistance↗
PubMed1995

Nosocomial candidiasis: epidemiology and drug resistance.

The epidemiology of nosocomial Candida is complex. Molecular DNA analysis has provided useful information in the study of nosocomial infection. The most important inpatient hospital reservoir is colonized patients. Most patients are infected with strains they harbor. Findings from recent studies suggest that some nosocomial Candida colonization is the result of exogenous acquisition. Hospital personnel and the inanimate hospital environment may serve as reservoirs, reservoir and they may be sources of acquired strains. The mechanism by which patients acquire Candida remains unproven, but most authors agree that indirect contact transmission is the most likely route for exogenous nosocomial acquisition of strains. Environmental surfaces in contact with healthcare workers and/or patients should also be considered a source of some Candida organisms when infection control measures are designed. Antifungal drug resistance has not been responsible for the spread of isolates. Further prospective studies using DNA typing methods for analysis of cultures using control strains are needed to define more clearly the patient and hospital reservoirs of infection and the modes of transfer. With increasing knowledge of the epidemiology of nosocomial Candida, novel control strategies are needed.

Candida↗
PubMed1995

Invasive Candida guilliermondii infection: in vitro susceptibility studies and molecular analysis.

Candida guilliermondii is rarely isolated from humans. We describe a case of disseminated C. guilliermondii with associated purulent pericarditis, despite high-dose amphotericin B (AmB), in a 19-year-old female with aplastic anemia who underwent BMT. In vitro susceptibility studies of the 13 clinical isolates, two control strains and one environmental isolate revealed a minimum inhibitory concentration (MIC) range of (0.19-1.56 micrograms/ml) for AmB and (1.25-10 micrograms/ml) for fluconazole. Pulsed-field gradient gel electrophoresis was performed to evaluate possible similarities between strains. This case is significant for several reasons, the high degree and prolonged duration of fungemia despite high-dose AmB and concomitant flucytosine, the change in in vitro susceptibility during therapy, the initial misidentification of the yeast isolate, and the invasiveness of the organism. The poor response to therapy may have been due to the severe and sustained neutropenia and the high MICs of C. guilliermondii to AmB.

Adult↗
PubMed1994

Randomized comparative trial with ampicillin/sulbactam versus cefamandole in the therapy of community acquired pneumonia.

In a randomized prospective study ampicillin/sulbactam and cefamandole were compared in the therapy of patients hospitalized with community acquired pneumonia. Patients receiving ampicillin/sulbactam (n = 37) and cefamandole (n = 38) were similar with respect to age (mean age 70 vs. 76 years respectively), clinical characteristics, severity of illness and underlying disease. Pathogens isolated from patients in the cefamandole and ampicillin/sulbactam group, respectively, were Streptococcus pneumoniae (7 vs. 7 patients), Haemophilus parainfluenzae (7 vs. 6 patients), Haemophilus influenzae (5 vs. 5 patients), Staphylococcus aureus (5 vs. 4 patients), Escherichia coli (4 vs. 4 patients), Klebsiella pneumoniae (3 vs. 3 patients), Enterobacter spp. (2 vs. 3 patients), Moraxella catarrhalis (1 vs. 2 patients), and organisms of the oral flora (4 vs. 3 patients). The rate of resistance to penicillin was 80%, to clindamycin 76%, to erythromycin 45%, to ampicillin 43%, and to cefazolin 18%. Overall successful treatment rates of 81% for cefamandole and 97% for ampicillin/sulbactam (p = 0.05) were observed. Both cefamandole and ampicillin/sulbactam were shown to be effective agents for therapy of community acquired pneumonia; however ampicillin/sulbactam demonstrated superior overall clinical efficacy.

Adult↗
PubMed1994

IS6770, an enterococcal insertion-like sequence useful for determining the clonal relationship of clinical enterococcal isolates.

Enterococci expressing resistance to antimicrobial agents are increasingly important nosocomial pathogens. Effective strategies to prevent or abort outbreaks of resistant enterococcal infection will rely on an accurate understanding of the mechanisms by which these organisms spread. A 1065-bp insertion-like sequence (IS6770) is present in varying copy numbers in > 90% of enterococcal strains thus far examined. Hybridization patterns resulting from hybridization of enterococcal genomic DNA with an internal IS6770 probe vary considerably between unrelated strains and correlate well with results of pulsed-field gel electrophoresis and field-inversion gel electrophoresis in identifying clonal relationships among enterococcal isolates. IS6770 analysis of several outbreaks of resistant enterococci has confirmed the spread of single resistant clones rather than the emergence of resistance within the resident flora. These results suggest that IS6770 hybridization will be a useful tool for tracing the epidemiology of nosocomial enterococcal infections.

Amino Acid Sequence↗