Peter G. Pitsakis

Hospital-acquired Infection with Vancomycin-resistant Enterococcus faecium Transmitted by Electronic Thermometers

OBJECTIVES To describe an epidemic of vancomycin-resistant Enterococcus faecium causing bacteremia and bacteriuria, to identify the source of infection, to delineate risk factors associated with acquisition of the organism, and to determine antibiotic sensitivities for the organism. DESIGN Investigation of an epidemic, including a case-control study. SETTING Medical-surgical intensive care unit and ward in a university medical center. PATIENTS Nine patients infected or colonized with vancomycin-resistant Enterococcus faecium and 20 noninfected controls. MEASUREMENTS Clinical data, environmental surveillance cultures, and in-vitro microbiologic studies. RESULTS Colonization or infection by vancomycin-resistant E. faecium was associated with an increased duration of treatment with ceftazidime, 13.2 compared with 4.6 days, and a greater number of nonisolated days of hospitalization in the intensive care unit, 19.9 compared with 6.4 days for infected and noninfected patients, respectively (P less than 0.05). Environmental surveillance cultures recovered the organism repeatedly from the rectal probe handles of three electronic thermometers used exclusively on nonisolated patients in the intensive care unit. Restriction endonuclease analysis of plasmid DNA showed that all clinical and environmental isolates were identical. Infection control measures, including isolation of colonized or infected patients and removal of the rectal thermometer probes suspected to be responsible for transmission, resulted in termination of the outbreak. In-vitro, time-kill studies showed that the combination of ciprofloxacin, rifampin, and gentamicin resulted in bactericidal activity against the organism. CONCLUSIONS This nosocomial outbreak of infection due to a highly vancomycin-resistant strain of Enterococcus is the first epidemic in which an electronic thermometer has been implicated as the vehicle of transmission for an infectious agent.

Does Asymptomatic Bacteriuria Predict Mortality and Does Antimicrobial Treatment Reduce Mortality in Elderly Ambulatory Women

Asymptomatic bacteriuria, a common problem of the elderly, has been associated with increased mortality in the elderly [1-4], although not all studies have confirmed this finding [5-9]. To reconcile these conflicting results, we did a longitudinal study of urinary tract infection in ambulatory elderly women to evaluate the putative relation between asymptomatic bacteriuria and mortality. We considered resolution of this issue to be important because of the implications for clinical practice. If asymptomatic bacteriuria were shown to be an independent risk factor for mortality and if it could also be shown that eradication of the infection by antimicrobial therapy decreased the risk for death, then screening and antimicrobial treatment of elderly ambulatory women with asymptomatic bacteriuria might be warranted and the cost of identifying and treating such infections might be justified. Conversely, failure to confirm a relation would support the view that programs to screen for bacteriuria would not be justified if their goal was to enhance survival. This report summarizes the findings of our 9-year study to determine whether asymptomatic bacteriuria in elderly ambulatory women is a marker of increased mortality and, if so, whether it is because of an association with other determinants of mortality or because asymptomatic bacteriuria is itself an independent cause, the removal of which might improve longevity. The components of the study were a longitudinal study in elderly ambulatory women to compare mortality in those with and without asymptomatic bacteriuria and a double-blind, controlled clinical trial in which antimicrobial therapy was administered for asymptomatic bacteriuria to assess whether treatment decreases mortality. Methods Participant enrollment and the participating institutions have been described previously [10, 11]. Elderly ambulatory residents of the Philadelphia Geriatric Center and of 21 continuing care retirement communities in the greater Philadelphia metropolitan area who gave informed consent were enrolled in this long-term study of urinary tract infection in the elderly. Enrollment continued throughout the course of the study. Philadelphia Geriatric Center houses about 1000 residents who primarily are Jewish; incomes are higher than the maximum Social Security payment; and congregate living is provided either in an apartment house or in a nursing home. In contrast, the continuing care retirement communities are smaller (bed size range, 108 to 675); incomes are higher; residents are primarily not Jewish; and a higher proportion of residents are fully independent. All female residents were eligible to participate except those with indwelling catheters or those incapable of providing midstream clean-catch urine specimens for culture. Specimens were obtained on enrollment and every 6 months thereafter. The protocol was approved by the appropriate institutional review boards, and informed consent was obtained from the participants or their surrogates. Table 1 shows the study periods and chronology of important study events. Throughout the study, urine cultures were obtained at about 6-month intervals. An observational study to compare mortality of bacteriuric and nonbacteriuric volunteers regardless of treatment status was begun in January 1983 and ended in February 1992. Initially, residents with asymptomatic bacteriuria were identified and followed, but treatment was not given. However, on 10 October 1983, a controlled clinical trial was begun to evaluate whether antimicrobial therapy for asymptomatic bacteriuria decreased mortality; every bacteriuric study participant identified after this date was enrolled in the trial. Mortality among residents who were treated with antimicrobial agents for asymptomatic bacteriuria each time it was present was compared with the mortality of those who received no therapy for their episodes of bacteriuria. At enrollment, participants were assigned to the treatment group or to the control group based on the last digit of an identification number unrelated to the conduct of the study. Urine cultures were read by personnel blinded to the study group assignment. When asymptomatic bacteriuria was identified, participants with even numbers were given antimicrobial therapy according to a defined protocol (see below); those with odd numbers served as controls. From 10 October 1983 to 10 December 1987, controls were given no therapy. Thereafter, on the advice of external consultants, the protocol was changed so that participants not assigned to the active treatment group were given placebo pills in place of no treatment. The placebo pills were identical in appearance to each of the antimicrobial agents used. Thus, after 10 December 1987, volunteers with asymptomatic bacteriuria were given therapy in either the form of antimicrobics or placebo after a new consent was obtained; the volunteers and clinical personnel did not know study group assignments. Table 1. Study Design and Enrollment The methods for collecting first-morning urine and for processing the specimens in our research microbiology laboratory have been previously described [10, 11]. Participants were considered to have asymptomatic bacteriuria on a survey if two urine specimens were culture-positive (105 colony-forming units or more per mL of urine) for the same organism within 2 weeks. From 10 October 1983 through 10 December 1987, residents with asymptomatic bacteriuria who were assigned to receive antimicrobial treatment were given short-course therapy (single dose or 3 days) as follows: trimethoprim, 200 mg in one dose; trimethoprim-sulfamethoxazole, 1 double-strength tablet; cefaclor, 500 mg three times a day for 3 days; amoxicillin, 250 mg three times a day for 3 days; carbenicillin indanyl sodium, four times a day for 3 days; or macrodantin, 100 mg twice a day for 3 days, depending on susceptibility of the infecting organism and history of drug allergy. Participants were considered cured if test-of-cure cultures contained less than 104 colony-forming units/mL of the infecting organism on cultures obtained 5 to 10 days after antimicrobial treatment or placebo or on cultures obtained on the next survey in those receiving no therapy. When positive for the same organism, patients were retreated for 14 days with test-of-cure culture afterward. If the organism differed, reinfection was diagnosed and a single dose or 3-day therapy was used; treatment failures were treated as defined above. Test-of-cure cultures were obtained again after therapy and, if positive for the same organism, participants were treated for 14 days. No treatment was given after failure of a 14-day course or two reinfections after short courses. Controls received no therapy during this period. After 10 December 1987, culture-positive patients were assigned to antimicrobial treatment or placebo. Single-dose therapy was given with trimethoprim, 200 mg, or norfloxacin, 400 mg, depending on the susceptibility of the organism; the same drugs (trimethoprim, 100 mg twice daily, and norfloxacin, 400 mg twice daily) were used for 14 days of therapy in patients failing single-dose therapy. Single-dose therapy was used for reinfection. The placebo pills and regimen given to a placebo recipient matched the regimen administered to the participant in the active treatment group who was treated most recently (for example, if the active treatment participant received short-course trimethoprim followed by 14 days of trimethoprim, the next placebo participant received short-course trimethoprim placebo followed by 14 days of trimethoprim placebo). Symptomatic infections were managed by the participants personal physician or by physicians associated with the facility in which the patient lived. Reports were received on an annual or semiannual basis from the participating institutions that detailed changes in their census. All deaths were noted, and registry coordinators reviewed available documents to confirm each death. After 1 September 1987, detailed functional and mental status assessments were done when persons were newly enrolled into the study or were seen for an annual follow-up visit using techniques previously described [11, 12]. Self-care activities of daily living were assessed by a modification of the Multilevel Assessment Instrument [13], and mental status was assessed using a modified version of the Kahn and Goldfarb questionnaire [14]. A subjective measure of global health status (scale, 1 to 4) was based on responses to the question: How do you rate your health: excellent (score 1), good, fair, and bad or poor (score 4)? Diagnoses recorded in the persons medical record were extracted and provided a more objective measure of health status; they were coded according to the ICD-9-CM three-digit codes [15]. The Geriatric Depression Scale [16] was used to assess depressive symptoms, and walking ability was assessed on a scale of 1 (specialized help needed) to 3 (help not needed) [11]. Statistical Analysis Observational Study These analyses compared residents with asymptomatic bacteriuria with residents who did not have asymptomatic bacteriuria on any of the urine culture surveys done during the period of their participation. For the purposes of the survival analyses in the observational study, the results of urine cultures were considered a time-dependent covariate. Accordingly, participants were considered in the ever-positive group once asymptomatic bacteriuria was identified, and all subsequent time on study was contributed to the group with positive cultures regardless of urine culture results on subsequent surveys. Persons entering the study with a negative urine culture were considered in the never-positive group until asymptomatic bacteriuria was identified. Thus, a person who entered the study with negative cultures and who later became culture-positive would have contributed person-time to the follow-up of those in the categ

High-Level Penicillin Resistance among Isolates of Enterococci: Implications for Treatment of Enterococcal Infections

STUDY OBJECTIVE To determine the extent and clinical significance of high-level penicillin-resistant Enterococcus faecium at our institution. DESIGN Surveillance of clinical enterococcal isolates, in-vitro susceptibility and timed survival studies, and determination of antibiotic efficacy in an experimental model of enterococcal endocarditis. MEASUREMENTS AND MAIN RESULTS For a 6-month period, 14% of enterococcal isolates (30 of 212) were identified as E. faecium. One third of the isolates were highly resistant to penicillin G (minimum inhibitory concentration [MIC], greater than or equal to 200 micrograms/mL) but did not produce beta-lactamase. The findings from in-vitro survival studies showed that this high-level resistance resulted in the loss of bactericidal activity normally observed when an aminoglycoside antibiotic agent is combined with penicillin. An experimental rat model of endocarditis provided in-vivo data that confirmed our in-vitro observations. After the rats received therapy for 72 hours, penicillin G either alone or in combination with gentamicin did not significantly decrease the numbers of enterococci in vegetations on heart valves compared with untreated controls (P = 0.62 and P = 0.58, respectively). CONCLUSIONS Enterococcus faecium accounts for a notable proportion of clinical enterococcal isolates. Many strains from patients at our institution, as well as from patients at other institutions throughout the country, are highly resistant to penicillin. Because high-level penicillin resistance has important therapeutic implications, periodic surveillance and MIC testing of significant enterococcal isolates, especially E. faecium, are suggested.

Epidemiology of Asymptomatic Bacteriuria in Elderly Women

We studied asymptomatic bacteriuria in elderly ambulatory women residents without indwelling catheters in self‐contained apartment houses at the Philadelphia Geriatric Center (PGC), in the nursing home at PGC, and in several life‐care communities (LCC). Subjects were studied every 6 months from January 1983 through January 1989, and since enrollment was continuous some participated in more surveys than others. PGC residents were middle class and lived either in a self care apartment house (CL) or nursing home (NH); LCC residents were middle or upper class. Antimicrobial therapy for asymptomatic bacteriuria was not given by the study team.

Pyuria and Asymptomatic Bacteriuria in Elderly Ambulatory Women

Excerpt Bacteriuria is common in elderly persons (1-4) and is usually asymptomatic (5). In the absence of symptoms, pyuria is the only readily available way to differentiate urinary infection with ...

In vitro postantibiotic effect of daptomycin (LY146032) against Enterococcus faecalis and methicillin-susceptible and methicillin-resistant Staphylococcus aureus strains.

The suppression of bacterial growth that persists after brief exposure to antimicrobial agents has been termed the postantibiotic effect (PAE). This pharmacodynamic interaction varies for each microorganism-antimicrobial agent combination. Daptomycin (LY146032) is a new lipopeptide antibiotic with activity against gram-positive organisms. We studied the in vitro bactericidal activities and PAEs of the following drugs: daptomycin compared with penicillin G and vancomycin, without and with gentamicin against Enterococcus faecalis strains; daptomycin compared with nafcillin and vancomycin against methicillin-susceptible Staphylococcus aureus strains; and daptomycin compared with vancomycin against methicillin-resistant S. aureus strains. Daptomycin, alone and when used in combination with gentamicin, exhibited greater bactericidal activity and in general produced a longer PAE than standard effective regimens against the organism strains studied.

In vitro activity of RP 59500 (quinupristin/dalfopristin) against antibiotic-resistant strains of Streptococcus pneumoniae and Enterococci☆

The activity of RP 59500 (quinupristin/dalfopristin) was evaluated in vitro against antibiotic-resistant strains of Streptococcus pneumoniae (N = 15) and Enterococcus spp. (N = 43). By broth dilution MIC tests RP 59500 was highly active against penicillin-resistant S. pneumoniae and vancomycin-resistant Enterococcus faecium, but showed poor activity against E. faecalis. In time-kill studies the drug was rapidly bactericidal against S. pneumoniae but failed to kill most enterococci, even in the presence of gentamicin or human serum.

Does Treatment of Asymptomatic Bacteriuria in Older Ambulatory Women Reduce Subsequent Symptoms of Urinary Tract Infection

OBJECTIVE: To determine whether treatment of asymptomatic bacteriuria in older ambulatory women affects the subsequent development of symptoms of urinary tract infection.

Antibiotic treatment of experimental endocarditis due to vancomycin- and ampicillin-resistant Enterococcus faecium.

We compared ciprofloxacin, rifampin, and gentamicin treatments, alone and in combination, for 5 days in the therapy of experimental aortic valve endocarditis in rats caused by a clinical isolate of vancomycin-resistant Enterococcus faecium. The MICs and MBCs of vancomycin, ciprofloxacin, rifampin, and gentamicin were 250 and > 1,000, 3.1 and 6.3, 0.098 and 1.6, and 12.5 and > 50 micrograms/ml, respectively. Infected rats were sacrificed after completing 5 days of therapy. Additional rats within each treatment group were followed for 5 days beyond the last dose of antibiotic therapy. Although survivals in the different groups were not significantly different after 5 days of therapy, survival was significantly better 5 days beyond the last dose of antibiotic therapy in rats treated with rifampin-containing regimens. The combination of ciprofloxacin and gentamicin was bactericidal in vitro and in vegetations from rats with enterococcal endocarditis. Rifampin alone was similarly bactericidal in vivo, but it was not significantly better than rifampin in combination with other antibiotics. Subpopulations resistant to rifampin, but not ciprofloxacin, were detected in the inoculum and in most vegetations during therapy. However, the combination of ciprofloxacin plus both gentamicin and rifampin reduced both the rifampin-susceptible and -resistant population in vegetations of 9 of 10 animals below the level of detection after 5 days of therapy. Nevertheless, a residual enterococcal population apparently remained in numbers of < 2 log10 CFU/g after 5 days of therapy, which resulted in relapse. Perhaps a longer course of therapy would have eliminated this residual population and improved efficacy. Images

Bactericidal activity of ramoplanin against antibiotic-resistant enterococci.

Ramoplanin, a new lipoglycodepsipeptide antibiotic, was uniformly active against 65 strains of enterococci, including strains highly resistant to vancomycin, penicillin G, and gentamicin. MBCs were usually within a fourfold dilution of the MICs. In time-kill studies, ramoplanin alone demonstrated dose-dependent bactericidal activity against enterococcal strains that resisted killing by vancomycin or penicillin in combination with gentamicin.