Biomedical subjects
Publications and source records attributed to M J Zervos.
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.
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.
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.
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.
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 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.
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.
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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.
Ten women with recurrent vulvovaginal candidiasis (RVVC) due to Candida albicans were followed for a mean of 35.3 months, and 81 vaginal isolates were evaluated by pulsed-field gel electrophoresis for strain delineation. The initial strain of C. albicans isolated was unique to each patient; in addition, in 8 women, only 1 strain type of C. albicans was identified throughout follow-up. In 1 patient, 3 strains of C. albicans were identified over a 27-month period and in another, 2 strains were recovered over a 30-month period. Two pairs of women shared identical strains of C. albicans. These results confirm the enormous diversity of strain types of C. albicans and demonstrate the persistence of colonization with the same strain over prolonged periods despite therapy. Results also support the concept of recurrent vaginitis being due to vaginal relapse or endogenous reinfection with the identical strain.
Enterococcus faecalis SF350 is a clinical isolate from Winnipeg, Canada, with high-level (MIC > 2,000 micrograms/ml) gentamicin resistance. The genetic determinant for gentamicin resistance was located on the chromosome of SF350 and could be mobilized by a coresident conjugative plasmid, pYN120. Genetic and physical analyses showed that the gentamicin resistance determinant was located on a 27-kb transposable element which was designated Tn924.
Enterococcus faecium strains resistant to ampicillin, high levels of gentamicin, and vancomycin but susceptible to teicoplanin (vanB class vancomycin resistance) were recovered from 37 patients during an outbreak involving a 250-bed university-affiliated hospital. Three isolates with vancomycin MICs ranging from 8 to 256 micrograms/ml all hybridized with a vanB probe. Restriction endonuclease analysis of chromosomal and plasmid DNA suggested that all isolates tested were derived from a single clone. Vancomycin resistance was shown to be transferable. Risk factors for acquiring the epidemic strain included proximity to another case patient (P, 0.0005) and exposure to a nurse who cared for another case patient (P, 0.007). Contamination of the environment by the epidemic strain occurred significantly more often when case patients had diarrhea (P, 0.001). Placing patients in private rooms and requiring the use of gowns as well as gloves by personnel controlled the outbreak. These findings suggest that multidrug-resistant E. faecium strains with transferable vanB class vancomycin resistance will emerge as important nosocomial pathogens. Because extensive environmental contamination may occur when affected patients develop diarrhea, barrier precautions, including the use of both gowns and gloves, should be implemented as soon as these pathogens are encountered.
Enterococcal nosocomial infections are becoming more common. Their multiple resistance mechanisms to various antibiotics pose serious therapeutic problems. Despite 40 years of intense development of antimicrobial agents, no agent surpasses the synergistic effects of a combination of a penicillin or vancomycin plus an aminoglycoside for treatment of enterococcal infections. New agents that have bactericidal activity against enterococci are needed as the incidence of resistant strains increases.
OBJECTIVE: The purpose of this study was to determine aspects of the epidemiology of nosocomial infection due to Candida parapsilosis. Candida species are important nosocomial pathogens; however, little epidemiologic information is available. PATIENTS AND METHODS: We prospectively cultured specimens from 98 patients admitted to the bone marrow transplant unit and a medicine intensive care unit (ICU) of a tertiary care hospital. Specimens from hands of personnel and environmental surfaces were also cultured. Environmental cultures were done before patients were admitted to a studied unit. Restriction enzyme analysis (REA) of chromosomal DNA was used as a typing system to determine the relatedness of strains. RESULTS: C. parapsilosis was identified from five patients, six hand cultures from four hospital staff, and two environmental surfaces. All five patients had negative initial cultures and acquired C. parapsilosis after admission to the study unit. There were no significant differences between patients and control subjects in age, underlying disease, immunosuppressive therapy, and instrumentation. The duration of antibiotic therapy (median: 32.8 versus 11.8 days, p = 0.05) and the duration in the unit (means: 30.1 versus 16.1 days, p = 0.048) was longer in patients than in controls. No common source was identified. REA revealed three strain types; however, one strain type was identical in four patients, three staff members, and two environmental surfaces. CONCLUSION: These results suggest exogenous acquisition of C. parapsilosis. Based upon isolation of identical patient strains of C. parapsilosis from inanimate surfaces before patients were admitted to a study unit, there is evidence that the organism may have been acquired from the hospital environment. The principal mechanism of transmission was probably indirect contact via the hands of hospital personnel.
Vaginitis due to Saccharomyces species is extremely rare. Nine patients with 20 vaginal isolates of Saccharomyces cerevisiae who presented with either asymptomatic vaginal colonization or symptomatic vaginitis indistinguishable from that caused by Candida albicans are described. All patients had a history of chronic or recurrent vaginitis, and all but two had systemic or local predisposing factors. In vitro tests of antimycotic sensitivity revealed reduced susceptibility of S. cerevisiae to the majority of available azole agents, with outright resistance to fluconazole. In accordance with these findings, the clinical response to conventional topical and oral antimycotic drugs was frequently suboptimal and incomplete. Electrophoretic karyotyping of strains revealed several distinct types of S. cerevisiae; this information permitted both longitudinal follow-up and differentiation of relapse from reinfection. In three patients with recurrent vaginitis, a unique epidemiological relationship was documented between S. cerevisiae and Torulopsis glabrata, another unusual and resistant vaginal pathogen. Isolation of S. cerevisiae from the vagina of symptomatic patients should not be ignored; treatment of vaginal infection with this yeast requires selected, often prolonged therapy.
To evaluate the mechanism and risk factors associated with the nosocomial acquisition of Candida albicans, a 10-month prospective study was conducted in a 24-bed bone marrow transplant unit and an 8-bed medical intensive care unit of a university hospital. A total of 98 patients had samples taken on admission and during hospitalization for culture. Samples from hands of hospital personnel and environmental surfaces were also cultured. C. albicans was isolated from 52 patients, and each patient was matched with a control. Fourteen patients acquired C. albicans after admission to the study. Prior antibiotics and length of time spent in the unit were more common in patients with new acquisition of C. albicans than in controls (92% vs. 64% and 32.5 vs. 13.0 days, respectively). Restriction enzyme analysis revealed 32 strain types; 4 were common to 30 patients and 10 environmental surfaces. Identical strains of C. albicans from patients who were geographically and temporally associated suggests the exogenous nosocomial acquisition of C. albicans through indirect patient contact.
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Sparfloxacin and clinafloxacin alone and in combination with gentamicin, were evaluated for the treatment of experimental endocarditis in rabbits caused by ampicillin-resistant enterococci. Clinafloxacin was tested against Enterococcus faecalis strain WH245, a beta-lactamase producer lacking high-level gentamicin resistance (MIC 12.5 mg/L). Sparfloxacin was tested against Enterococcus faecium strain SF2149 a non-producer of beta-lactamase (ampicillin MIC 400 mg/L, gentamicin MIC 12.5 mg/L). For strain WH245, clinafloxacin alone significantly reduced enterococcal counts in vegetations (7.7 log10 cfu/g) and for strain SF2149, sparfloxacin significantly reduced counts (7.0 log10 cfu/g) compared with untreated controls (WH245, 8.8 log10 cfu/g and SF2149, 9.3 log10 cfu) or treatment with ampicillin plus gentamicin (WH245, 9.7 log10 cfu/g). The addition of gentamicin resulted in no further reduction of bacterial counts in vegetations but resulted in an increase in sterilization of blood for strain SF2149. These results suggest that sparfloxacin and clinafloxacin and may prove useful in the therapy of infections due to ampicillin-resistant enterococci.