Incidence of hemolysin, gelatinase, and aggregation substance among enterococci isolated from patients with endocarditis and other infections and from feces of hospitalized and community-based persons

The presence of hemolysin, gelatinase, and aggregation substance (by use of a probe known to hybridize to most pheromone-responsive plasmids) was determined in 192 isolates of Enterococcus faecalis from patients with endocarditis or other infections and fecal isolates from hospitalized patients or healthy volunteers, and in 86 non-E. faecalis isolates. Hemolysin was more common in nonendocarditis clinical isolates and in hospital fecal isolates (37% and 31%, respectively) than among endocarditis and community fecal isolates (16% and 20%, respectively). Gelatinase and aggregation substance, respectively, were found in 54% and 52% of isolates from endocarditis, in 58% and 72% of isolates from other infections, in 62% and 56% of hospital fecal isolates, and in 27% and 30% of fecal isolates from healthy volunteers. All 86 non-E. faecalis enterococcal isolates were negative for these traits. The absence of hemolysin, gelatinase, or the aggregation substance gene in > 45% of endocarditis E. faecalis isolates suggests that while these traits may play a role in virulence, other properties are also important.

Bacterial urinary tract infections in diabetes

Bacterial UTIs are a common problem in patients with diabetes mellitus. Bacteriuria is more common in diabetic women than in non-diabetics owing to a combination of host and local risk factors. Upper tract disease is also more common in this group. Diabetics are at higher risk for intrarenal abscess, with a spectrum of disease ranging from acute focal bacterial pyelonephritis to renal corticomedullary abscess to the renal carbuncle. A number of uncommon complicated UTIs, such as emphysematous pyelonephritis and emphysematous pyelitis, occur more frequently in diabetics. Because of the frequency and severity of UTI in diabetics, prompt diagnosis and early therapy is warranted.

The evolving epidemiology of methicillin-resistant Staphylococcus aureus at a university hospital

OBJECTIVE

To describe the epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) at a university hospital during a 14-month period.

DESIGN

Prospective laboratory-based surveillance for MRSA with descriptive epidemiology based on medical chart review and characterization of strains by DNA typing, using pulsed-field gel electrophoresis (PFGE).

SETTING

An 850-bed tertiary care university hospital.

PATIENTS

Patients with clinical isolates of MRSA.

MAIN OUTCOME MEASURE

Determination whether MRSA isolates were community- or hospital-related.

RESULTS

Among 87 patients with MRSA, 36 (41%) had community-acquired infections. Community acquisition was associated with recent hospitalization, previous antibiotic therapy, nursing home residence, and intravenous drug use. Greater than 3 months had elapsed from the time of discharge for 13 (62%) of the 21 patients with community-acquired isolates hospitalized within the last year. Eight patients (22%) with community-acquired MRSA had no discernible risk factors. PFGE allowed differentiation of 35 distinct whole-cell DNA patterns; heterogeneity was seen among both nosocomial and community-acquired isolates, with few instances of cross-transmission.

CONCLUSIONS

Our data suggest an increase in community acquisition of MRSA. PFGE demonstrated heterogeneity of MRSA isolates from both the community and the hospital setting.

Mupirocin resistance among consecutive isolates of oxacillin-resistant and borderline oxacillin-resistant Staphylococcus aureus at a university hospital

Mupirocin resistance was determined in consecutive oxacillin-resistant and borderline oxacillin-resistant Staphylococcus aureus clinical isolates collected over 14 months at a university hospital during 1991 and 1992. Twenty of 86 (23%) oxacillin-resistant and borderline oxacillin-resistant S. aureus isolates were mupirocin resistant; 80% were high-level resistant. Prior mupirocin use was a significant risk factor (relative risk, 6.08; 95% confidence interval, 3.7 to 9.99). Seven of 20 resistant isolates were distinct strains, as determined by pulsed-field gel electrophoresis typing. Two instances of clonal dissemination of a single strain occurred, but several other distinct mupirocin-resistant strains were documented. Mupirocin resistance was unexpectedly common among these isolates.

Differentiation of distribution systems, source water, and clinical coliforms by DNA analysis

During a 2-week period, Enterobacter cloacae was isolated from throughout the water distribution system in New Haven County, Connecticut. There was no forewarning of this event and no apparent reasons for it. Several epidemiologic and public health questions required rapid answers. Were these E. cloacae isolates the result of treatment failure and breakthrough or was regrowth occurring within the system? Did the E. cloacae isolates represent a health threat and were they causing infection? Pulsed-field gel electrophoresis utilizing whole-cell DNA digestion with restriction endonuclease SpeI permitted the rapid generation of specific information to answer these questions. Gel bands were stained with ethidium bromide and photographed with UV illumination. Homogeneity among isolates was confirmed by repeat digestion with XbaI. From each of the water distribution isolates, a single pattern of restriction endonuclease fragments was generated, indicating that only one clone of E. cloacae was in the distribution system. There was no homogeneity between source and distribution water E. cloacae isolates. Moreover, E. cloacae clinical isolates from patients from New Haven area hospitals showed no identity with E. cloacae isolated from the distribution system. Therefore, pulsed-field gel electrophoresis DNA analysis demonstrated that the E. cloacae from the distribution system was the result of a regrowth bloom within the system and not the result of treatment failure and that this clone was not causing a public health risk.

An outbreak of mupirocin-resistant Staphylococcus aureus on a dermatology ward associated with an environmental reservoir

OBJECTIVE

To investigate a cluster of mupirocin-resistant Staphylococcus aureus on a dermatology ward.

DESIGN

An outbreak of mupirocin-resistant S aureus was noted on the dermatology ward during a prospective epidemiologic study of methicillin-resistant S aureus (MRSA) and borderline methicillin-susceptible S aureus (BMSSA). Pulsed-field gel electrophoresis (PFGE) of whole-cell DNA digested with Sma I was used as a marker of strain identity.

SETTING AND PATIENTS

An 850-bed university hospital with a 12-bed inpatient dermatology ward. Most patients have severe, exfoliating dermatologic disorders.

RESULTS

MRSA or BMSSA were isolated from 13 patients on the dermatology ward over a 14-month period. Eleven of these isolates (84.6%) were mupirocin-resistant. Nine isolates were present on admission (81.8%); 8 of these patients had been hospitalized on the same ward within the last two months. Nasal and hand cultures from 36 personnel were negative for mupirocin-resistant MRSA or BMSSA. Extensive environmental culturing revealed that a blood pressure cuff and the patients' communal shower were positive for mupirocin-resistant BMSSA. PFGE of all mupirocin-resistant isolates demonstrated that the nine patients and both environmental sources had identical DNA typing patterns.

INTERVENTIONS

Changing of blood pressure cuffs between patients and more stringent cleaning of communal areas was initiated. Repeat environmental cultures were negative.

CONCLUSIONS

S aureus is not usually associated with an environmental reservoir; however, these patients all had severe desquamation, which may have prolonged environmental contamination.

Epidemiological typing of Moraxella catarrhalis by using DNA probes

Small-fragment restriction enzyme analysis and DNA-DNA hybridization were used to compare 60 strains of Moraxella catarrhalis isolated from various geographic locations. Restriction enzyme analysis with HaeIII resulted in 46 different patterns, 7 of which were shared by more than one isolate. Hybridizations with two DNA probes resulted in 18 different patterns, 11 of which were shared by more than one isolate. Strains with the same restriction enzyme pattern always had the same hybridization pattern. However, of the 50 strains that shared the 11 hybridization patterns, 39 could be further differentiated by restriction enzyme analysis. We found that hybridization is a method that is specific for the epidemiological typing of M. catarrhalis, but because of limited sensitivity, combination with small-fragment restriction enzyme analysis may be necessary to better determine the relatedness of strains.

Enterobacter taylorae, a new opportunistic pathogen: report of four cases

Severe nosocomial infections due to Enterobacter taylorae (formerly known as CDC Enteric Group 19) are described in four patients. Unlike most members of the Enterobacter genus, the isolates were not susceptible to penicillins or cephalosporins. Restriction endonuclease analysis of E. taylorae DNA obtained from three patients identified two distinct strains. One strain was found in two patients, suggesting a common source which we were not able to identify. We postulate that in patients harboring E. taylorae, the combination of cephalosporin therapy and instrumentation enables this organism to become an opportunistic pathogen.

Molecular characterization of highly gentamicin-resistant Enterococcus faecalis isolates lacking high-level streptomycin resistance

Antimicrobial susceptibilities and DNA contents were analyzed for six clinical isolates of Enterococcus faecalis that had high-level resistance to gentamicin (MIC > 2,000 micrograms/ml) but not streptomycin and were obtained from patients in diverse geographic areas. Contour-clamped homogeneous electric field electrophoresis of genomic DNA showed all isolates to be different strains. Gentamicin resistance was transferred from four isolates to plasmid-free enterococcal recipients in filter matings. Restriction enzyme analysis of transconjugants showed distinct gentamicin resistance plasmids. A probe specific for the gentamicin resistance determinant hybridized to the plasmids of four isolates and to the chromosomes of two isolates. These findings suggest that clonal dissemination is not responsible for the spread of these resistant strains, that resistance determinants occur on different plasmids as well as on the chromosome of E. faecalis, and that the genetic determinants of resistance are related.

Pseudoepidemic of Nocardia asteroides associated with a mycobacterial culture system

Nocardia isolations increased from 0.7 to 11.7/1,000 acid-fast bacillus and mycological cultures (P less than 0.000001). Only three isolations from one patient represented infection. Pseudoepidemic strain identity was confirmed by DNA fingerprinting; the isolate causing infection was distinct. The end of the pseudoepidemic was associated with changing the needle sterilizer and prolonging needle sterilization time on the BACTEC 460 machine. To our knowledge, this is the first reported Nocardia asteroides pseudoepidemic.

The pre-travel medical evaluation: the traveler with chronic illness and the geriatric traveler

The pre-travel medical evaluation of elderly patients and patients with chronic illness requires special assessment and advice. Screening and special precautions are reviewed for traveling patients with respiratory disease, cardiac disease, sinusitis, diabetes mellitus, HIV infection, and other chronic medical conditions. Current guidelines for empiric therapy and prophylaxis of travelers' diarrhea are reviewed, with emphasis on concerns in geriatric or chronically ill travelers. Special considerations such as potential drug-drug interactions and insurance coverage are also discussed.

Time-kill kinetic studies of ampicillin/sulbactam for beta-lactamase-producing enterococci

beta-Lactamase-producing (Bla+) enterococci have now been reported from several geographic areas. Most of these strains also demonstrate high-level aminoglycoside resistance, making therapy of serious infections due to Bla+ enterococci difficult. Using time-kill kinetic studies, we evaluated the activity of ampicillin-sulbactam (Am/SB) against five clinical Bla+ Enterococcus faecalis isolates from three geographically distinct areas. Am at fourfold minimum inhibitory concentrations (MIC) concentrations did not achieve bactericidal activity as determined by time-kill kinetic studies. Am/SB achieved 99.9% reduction in growth at 24 hr at twofold MIC concentrations without an aminoglycoside in four of five strains. SB alone had little independent activity against any of the strains, but synergy of killing was achieved in all five strains with a combination of Am + SB. No synergy was shown in a Bla- control strain. Am/SB may be useful for serious infections due to Bla+ enterococci.

Epidemiology of an endemic strain of beta-lactamase-producing Enterococcus faecalis

Three previously reported beta-lactamase-producing (Bla+) enterococci with distinct but related antibiotic resistance phenotypes, plasmid profiles, and plasmid restriction endonuclease digestion patterns were isolated at the West Haven Veterans Administration Medical Center in Connecticut (WH245, WH257, WH571) in July 1986 and March 1987. In this study, we analyzed the whole-cell DNA of these isolates by using pulsed-field gel electrophoresis of large chromosomal fragments generated by SmaI digestion. The three West Haven isolates showed very similar chromosomal restriction endonuclease digestion patterns; these patterns were distinct from those of Bla+ and Bla- enterococci from other geographic areas and from those of other West Haven enterococci, suggesting an endemic Bla+ strain at this institution. Clinical information regarding these isolates suggests that exposure to the genitourinary clinic, obstructive urinary tract disease, and frequent antibiotic therapy may have been common risk factors for acquisition of this endemic strain.

Association of contaminated gloves with transmission of Acinetobacter calcoaceticus var. anitratus in an intensive care unit

PURPOSE

Acinetobacter calcoaceticus var. anitratus is an important nosocomial pathogen that has been associated with environmental reservoirs. An increased isolation rate of A. anitratus in our intensive care units (ICUs), from 0.03% (two of 7,800) to 0.5% (seven of 1,300) (p less than 0.00003), prompted an investigation.

PATIENTS, METHODS, AND RESULTS

Ten patients were admitted to the surgical ICU and nine to the medical ICU during the outbreak period (late December 1987 to January 1988). Controls were all patients on the units who were not infected or colonized with the transmitted strain of A. anitratus. Three patients had A. anitratus pneumonia. A throat culture prevalence survey demonstrated three patients colonized with A. anitratus. Cases were placed in a cohort and symptomatic cases treated. An epidemiologic investigation was conducted to identify reservoirs and modes of transmission. Latex gloves were being used for universal precautions without routine changing of gloves between patients. Environmental sources culture-positive for A. antitratus included a small volume medication nebulizer and gloves in use for patient care. Plasmid typing showed that plasmid profiles of isolates from two symptomatic patients, two colonized patients, the nebulizer, and the gloves were identical. Other A. anitratus ICU isolates had distinct plasmid profiles. All patients with the transmitted strain had been in the surgical ICU. The need for changing gloves between patients and contaminated body sites was reinforced.

CONCLUSION

Gloves, used incorrectly for universal precautions, may potentially transmit A. anitratus.

Reliability of performance measurements obtained using the stability testing and rehabilitation station (STARStation)

The purpose of this study was to determine within- and between-day reliability of measurements of nondisabled subjects for the variables of force and velocity when a balance board (STARStation) was positioned at heights of 4.5 and 7.5 cm from the supporting surface. Twenty-four nondisabled subjects each completed six trials of board rotation at a self-selected velocity. Each trial consisted of 10 revolutions in a clockwise direction. Measurements were repeated within the same day for a second board position, and all tests were completed again on a second day. Descriptive statistics were computed for force and velocity, and intraclass correlation coefficients (ICCs) were calculated. Data were submitted to analyses of variance and follow-up tests. Results showed slight differences between the first three and last three trials. Intraclass correlation coefficients for within-subject reliability for the independent variable day ranged from .72 to .81, and ICCs for within-day reliability for the independent variable trial ranged from .46 to .81. Clinicians using such protocols should be aware of differences within and between days and recognize that measurements will be influenced by the number of trials completed.

Evidence for clonal spread of a single strain of beta-lactamase-producing Enterococcus (Streptococcus) faecalis to six hospitals in five states

Beta-lactamase-producing (Bla+) enterococci have been reported in three state and two countries. Pulsed-field gel electrophoresis was used to compare 14 Bla+ Enterococcus (Streptococcus) faecalis isolated from hospitalized patients in seven states and three continents. The restriction endonuclease digestion patterns of isolates from Connecticut, Massachusetts, Lebanon, and Argentina were all markedly different, indicating that these were different strains. However, isolates from Delaware, Texas, Pennsylvania (Philadelphia and Pittsburgh), Florida, and Virginia were similar, indicating that these isolates were derivatives of a single strain. This conclusion was supported by hybridization using individual fragments as probes. Spread of Bla+ enterococci within the hospital setting was also demonstrated. These findings illustrate the value of pulsed-field gel electrophoresis for epidemiologic analyses and support the importance of identifying and containing organisms with new resistance properties in an effort to decrease their transmission to and from, as well as within, hospitals.

The effect of chloroquine prophylaxis on yellow fever vaccine antibody response: comparison of plaque reduction neutralization test and enzyme-linked immunosorbent assay

Weekly oral chloroquine prophylaxis for malaria has been associated with impaired antibody response to intradermal rabies vaccination. Experimental data indicate that chloroquine may inhibit yellow fever virus in vitro, yet there has been no clinical evidence to suggest that antibody response to yellow fever vaccine is impaired by concomitant oral administration of chloroquine. A prospective trial was undertaken to evaluate the antibody response to yellow fever 17D vaccine (Connaught Laboratories) of volunteers who were randomized to taking either chloroquine or no drug. Of fifty subjects, 28 were randomized to taking chloroquine, 22 were randomized to taking no drug. Yellow fever 17D vaccine was administered on day 0 and blood sampled on days 0, 14, 35 and 210. Chloroquine was administered weekly for four weeks. There was no significant difference in peak antibody titer by plaque reduction neutralization testing (PRNT) between the group that took chloroquine (mean log peak of reciprocal titer 1.43 +/- SD 0.60) with vaccine subcutaneously compared to vaccine-only group (mean log peak of reciprocal titer = 1.21 +/- 0.55). All fifty subjects seroconverted to yellow fever vaccine by day 210. ELISA testing was also performed on all subjects. The two tests showed good correlation (Spearman r = 0.675), although ELISA readings were positive by day 14 in significantly more subjects (p = .01). We conclude that routine anti-malarial doses of chloroquine do not affect antibody response to yellow fever 17D vaccine. ELISA testing, a less complex and less time-consuming test, correlates well with PRNT and is proposed for additional trials to measure yellow fever 17D vaccine response in flavivirus non-immune subjects.

Mycobacterium gordonae pseudoinfection associated with a contaminated antimicrobial solution

At Yale-New Haven Hospital, 46 specimens submitted for mycobacterial culture during an 8-week period in 1989 were positive for Mycobacterium gordonae, a nontuberculous acid-fast bacterium (AFB) of low pathogenicity. The specimens were submitted from 34 patients who came from various inpatient and outpatient services. Four patients were begun on antimycobacterial therapy on the basis of an AFB isolate which was later identified as M. gordonae. Isolation of M. gordonae was associated with use of the BACTEC TB system (BACTEC TB; Becton Dickinson Diagnostic Instrument Systems, Towson, Md.) and an antimicrobial solution, BACTEC PANTA PLUS (PANTA; Becton Dickinson Diagnostic Instrument Systems). The manufacturer reported that two lots (B9K1 and C9K1) of PANTA kits containing a single production lot (N8C1) of PANTA, which had been shipped to 173 laboratories, had been contaminated with M. gordonae. A survey of mycobacteriology laboratories in the United States revealed that, during April to July 1989, the M. gordonae isolation rate was 5.8/1,000 AFB specimens processed at laboratories that did not use BACTEC TB, 11.4/1,000 AFB specimens at laboratories that used BACTEC TB but not the implicated lot of PANTA, and 23.5/1,000 AFB specimens at laboratories that used BACTEC TB and the lot of implicated PANTA. Intrinsic contamination of PANTA was attributed to ineffective sterilization of water used in the manufacturing process and was not detected prior to product shipment because cultures for AFB were not part of the quality control regimen. This episode emphasizes that clinical laboratories can detect pseudoepidemics promptly if they are alert to abrupt increases in isolation rates, especially of unusual or generally nonpathogenic organisms.

Epidemiology of high-level gentamicin resistant enterococcal isolates from Zimbabwe

High-level gentamicin resistance (minimum inhibitory concentration of greater than or equal to 2,000 mcg/ml) in Enterococcus faecalis has not previously been reported in Africa to our knowledge. Eight of 28 (29%) rectal swab specimens obtained from hospitalized patients in Zimbabwe had gentamicin resistant enterococci. Previous exposure to penicillins or aminoglycosides were risk factors for colonization with these organisms. This study documents the presence of high-level gentamicin resistant enterococci in Africa and suggests that penicillin or aminoglycoside usage may select for gentamicin resistant enterococcal plasmids in Africa.

High-level gentamicin resistance in Enterococcus: microbiology, genetic basis, and epidemiology

Antibiotic resistance is an ever-increasing problem in enterococci. These bacteria are remarkable in their ability to acquire and disseminate antibiotic resistance genes by a variety of routes. Since first described in 1979, high-level resistance to gentamicin (MIC, greater than 2,000 micrograms/mL) has spread worldwide and has been responsible for serious infections. Resistance is plasmid-mediated and due to aminoglycoside-modifying enzymes. High-level gentamicin resistance indicates that there will be no synergistic bactericidal activity with penicillin-gentamicin combinations. The epidemiology of nosocomial enterococcal infections is remarkably similar to that of nosocomial infections caused by methicillin-resistant staphylococci and by multidrug-resistant gram-negative bacilli. The most likely way these resistant bacteria are spread among hospital patients is via transient carriage on the hands of hospital personnel. Patient-to-patient and interhospital transmission of strains has been reported recently. However, clonal dissemination is not the cause of the increased frequency of resistant strains, since gentamicin resistance appears in a variety of different conjugative and nonconjugative plasmids in Enterococcus.