Characterization of heteroresistance to fluconazole among clinical isolates of Cryptococcus neoformans.

Strains of Cryptococcus neoformans expressing heteroresistance to fluconazole have been described previously. The present study was conducted to investigate the prevalence of heteroresistance among clinical isolates of C. neoformans and to characterize the heteroresistant phenotypes. A total of 107 clinical isolates of C. neoformans for which the MICs of fluconazole ranged from 0.25 to 32 microg/ml were selected. The isolates were chosen to represent a broad geographic distribution. Of the 107 C. neoformans isolates tested, 4 grew on medium containing fluconazole at concentrations that were four to eight times higher than the MICs for each strain. A fifth isolate, for which the fluconazole MIC was 32 microg/ml, grew on agar with 64 microg of fluconazole per ml. These five isolates (4.7% of the total number) were confirmed to exhibit heteroresistant compositions by population analysis. The degree and frequency of resistance varied among the isolates. Stepwise selection by exposure to fluconazole resulted in subclones of all five strains for which the fluconazole MIC was >64 microg/ml. Subclones of three strains demonstrated a homogeneous population of resistant cells on medium containing 64 microg of fluconazole/ml. The resistance was sensitive to incubation temperature, that is, heteroresistance was demonstrable only at 30 degrees C by agar-based tests, and was reversible through serial transfers on fluconazole-free medium over a period of 8 days. These results suggest that the fluconazole-heteroresistant phenotype of C. neoformans exists in a significant proportion of clinical isolates and that fluconazole resistance can be developed by selection from heteroresistant clones and induction by exposure to fluconazole.

Identification of Candida dubliniensis based on temperature and utilization of xylose and alpha-methyl-D-glucoside as determined with the API 20C AUX and vitek YBC systems.

To have a better understanding of the role of Candida dubliniensis in clinical infections, it is essential that microbiology laboratories can identify this species rapidly and accurately in clinical specimens. C. dubliniensis has been reported to lack the ability to utilize xylose (XYL) and alpha-methyl-D-glucoside (MDG) and to grow poorly or not at all at 45 degrees C, whereas Candida albicans isolates utilize XYL and MDG and usually grow well at 45 degrees C. We tested 66 isolates of C. dubliniensis and 100 isolates of C. albicans with both the API 20C AUX and Vitek YBC systems to evaluate the ability of the XYL and MDG tests contained within each of these systems to distinguish between the two species. The ability to grow at 45 degrees C was also examined. None of the C. dubliniensis isolates grew at 45 degrees C, and 23 of 100 C. albicans isolates (23%) exhibited poor or no growth at 45 degrees C. The XYL and MDG tests contained within the API 20C AUX system were both negative for all 66 C. dubliniensis isolates and were positive for 98 (XYL) and 56 (MDG) of the 100 C. albicans isolates. With the Vitek system, 64 of 66 C. dubliniensis isolates (97.0%) were XYL negative and 63 (95.0%) were MDG negative. Conversely, 96 of 100 C. albicans isolates (96.0%) were XYL positive and 100 (100.0%) were MDG positive with the Vitek system. Clinical microbiology laboratories could use lack of growth at 45 degrees C and a negative XYL test with either the API 20C AUX or Vitek yeast identification system to provide a presumptive identification of C. dubliniensis. A negative MDG test result with either system would also be helpful but may misclassify C. albicans as C. dubliniensis, especially when the API 20C AUX system is used.

Molecular epidemiology of an outbreak of meningococcal disease in a university community.

Over a 2-month period, five cases of serogroup C meningococcal disease occurred in Iowa City, Iowa. Two patients were unacquainted university students who had independently visited another university with endemic meningococcal disease. Isolates from these patients had DNA fingerprints identical to those of the isolates responsible for infections on the other campus. Three cases for which the patients' isolates had a different DNA fingerprint were linked to visiting a local tavern. To disrupt the outbreak, the University of Iowa offered free meningococcal vaccine to all students. This report demonstrates that outbreaks of meningococcal disease may be due to more than one circulating strain and illustrates the utility of pulsed-field gel electrophoresis in defining the molecular epidemiology of meningococcal infections.

An experimental model for study of Candida survival and transmission in human volunteers.

In order to determine the potential for cross-transmission of Candida spp. between health-care workers and patients, the survival of clinical isolates of five species of Candida on the palms of human volunteers was tested. One hundred microliters of a McFarland 1.0 density suspension (5 x 10(5) cfu) from an overnight culture of Candida albicans, Candida krusei, Candida parapsilosis, Candida tropicalis and Candida glabrata was used as inoculum. The degree of hydrophobicity of the different Candida species was also tested and did not influence the survival. The half-lives were brief, being 9.5, 12.4, 7.4, 12.8, 9.6 min for Candida albicans, Candida krusei, Candida glabrata, Candida parapsilosis, and Candida tropicalis, respectively, but at 45 min 2.6 x 10(3) to 3 x 10(4) organisms remained on the hands. Survival of Candida albicans for as long as 24 h on inanimate surfaces was observed. Transmission from one hand to a second hand occurred in 69% of the experiments and from the first to a third hand in 38%. Transmission to and from inanimate surfaces was successful in most of the experiments (90%). This experimental model aids in the biological study of Candida spp. and suggests some of the potential mechanisms of transmission.

Long-term efficacy of intranasal mupirocin ointment. A prospective cohort study of Staphylococcus aureus carriage.

BACKGROUND: We investigated the long-term effect of a single 5-day application of intranasal mupirocin calcium ointment on Staphylococcus aureus nasal and hand colonization. The subjects were 68 healthy volunteers who were health care workers with stable S aureus nasal carriage and who had participated in a randomized, double-blind placebo-controlled clinical trial of intranasal mupirocin ointment. METHODS: A 1-year prospective cohort study of S aureus nasal carriers after treatment with active drug or placebo was performed. Cultures were obtained from all subjects 6 and 12 months after therapy. All subjects returned for the 6-month visit; 63 (93%) were examined at 1 year. The major outcome measure was the relative proportion of any S aureus cultured at either site at 6 and 12 months. The S aureus isolates were typed by restriction endonuclease analysis of plasmid DNA and by antibiotic susceptibility tests; the similarity of nasal and hand isolate "fingerprints" was compared. RESULTS: At 6 months, nasal carriage was 48% in the treatment group vs 72% in controls (relative risk, 0.68; 95% confidence interval, 0.45 to 1.02; P = .054); at 1 year, nasal carriage was 53% vs 76%, respectively (relative risk, 0.70; 95% confidence interval, 0.48 to 1.02; P = .056). Hand carriage at 6 months was significantly reduced among mupirocin recipients relative to controls (15% and 48%; P = .04, adjusted for the baseline rate of hand carriage). Thirty-six percent of treated subjects were recolonized in the nares with a new strain at 1 year, whereas 34% had reisolation of the original strain after initially negative posttherapy cultures. During the year of follow-up, hand carriage was observed at least once in two thirds of the subjects. Nearly all of the hand isolates (87%) exactly matched the subjects' coincident nasal plasmid fingerprint and antibiogram type. CONCLUSIONS: A single brief treatment course of intranasal mupirocin was effective in reducing nasal S aureus carriage for up to 1 year. When S aureus was recovered after nasal decolonization, the new isolate was as likely to represent colonization with a new strain as reisolation of the original strain. Staphylococcus aureus hand carriage was significantly decreased 6 months after therapy, further implicating the nares as the primary reservoir site for hand carriage.

Post-antibiotic effect of FK-037 and biapenem tested against five bacterial species.

The in-vitro post-antibiotic effect (PAE) was determined for two newer beta-lactams, FK-037 (a cephalosporin) and biapenem (a carbapenem). Our PAE results for these drugs were consistent with what has been reported previously for similar beta-lactams, e.g. Gram-positive organisms had measurable effects (0.4-2.2 hours), while Gram-negatives had variable results (0.0 to 1.4 hours). Even though the PAE test conditions generally coincided with achievable clinical levels for most organisms tested (< or = 4 mg/L for biapenem and < or = 8 mg/L for FK-037), the marginal or species dependent, short PAE values support the selection of multiple daily doses (two-to-four) based on conventional pharmacokinetic parameters such as the Cmax, AUC, and serum elimination half-life.

Postantibiotic effect of DU-6859a and levofloxacin as compared with ofloxacin.

The postantibiotic effect (PAE) was determined for two of the newer fluoroquinolones: DU-6859a and levofloxacin. All drugs (including ofloxacin control) had good PAE activity against Escherichia coli and Staphylococcus aureus. Only DU-6859a had PAE test conditions (< or = 0.5 mu/ml) that coincided with achievable clinical concentrations for all organisms tested. These data indicate that levofloxacin, like ofloxacin (PAEs, 1.0-2.9 h), could be administered once or twice daily and that the dosing of DU-6859a (PAEs, 1.6-2.4 h) might be extended to once every 24 h because of its documented PAE and its potency advantages as compared with levofloxacin and ofloxacin.

Comparative efficacy of alternative hand-washing agents in reducing nosocomial infections in intensive care units.

BACKGROUND: Effective hand-washing can prevent nosocomial infections, particularly in high-risk areas of the hospital. There are few clinical studies of the efficacy of specific hand-cleansing agents in preventing the transmission of pathogens from health care workers to patients. METHODS: For eight months, we conducted a prospective multiple-crossover trial involving 1894 adult patients in three intensive care units (ICUs). In a given month, the ICU used a hand-washing system involving either chlorhexidine, a broad-spectrum antimicrobial agent, or 60 percent isopropyl alcohol with the optional use of a nonmedicated soap; in alternate months the other system was used. Rates of nosocomial infection and hand-washing compliance were monitored prospectively. RESULTS: When chlorhexidine was used, there were 152 nosocomial infections, as compared with 202 when the combination of alcohol and soap was used (adjusted incidence-density ratio [IDR], 0.73; 95 percent confidence interval, 0.59 to 0.90). The largest reduction with chlorhexidine was in gastrointestinal infections (IDR, 0.19; 95 percent confidence interval, 0.05 to 0.64). When chlorhexidine was available, the rates of nosocomial infection declined in each of the ICUs, and health care workers washed their hands more often than when alcohol and soap were used (relative risk, 1.28; 95 percent confidence interval, 1.02 to 1.60). The total volume of alcohol and soap used was 46 percent that of chlorhexidine (P less than 0.001). CONCLUSIONS: A hand-disinfection system using an antimicrobial agent (chlorhexidine) reduces the rate of nosocomial infections more effectively than one using alcohol and soap. The improvement may be explained at least in part by better compliance with hand-washing instructions when chlorhexidine was used.

Elimination of coincident Staphylococcus aureus nasal and hand carriage with intranasal application of mupirocin calcium ointment.

OBJECTIVE: To determine the safety and efficacy of mupirocin calcium ointment in the elimination of Staphylococcus aureus nasal and hand carriage in healthy persons. DESIGN: A double-blind, placebo-controlled, randomized trial. SETTING: Clinical research unit of a tertiary medical center. SUBJECTS: Health care workers with stable S. aureus nasal carriage. INTERVENTIONS: Subjects (n = 68) were randomly assigned to receive either mupirocin or placebo intranasally twice daily for 5 days. MEASUREMENTS AND MAIN RESULTS: Cultures of the hands and nares were obtained at baseline and 72 hours after therapy. The nares were also cultured 1, 2, 4, and 12 weeks after therapy. Antimicrobial susceptibility testing and restriction endonuclease analysis of plasmid DNA were used to confirm strain identity. There were no serious side effects. Mupirocin decreased the frequency of S. aureus nasal carriage at each time interval: At 3 months, 71% of subjects receiving mupirocin remained free of nasal S. aureus compared with 18% of controls. This difference (53%; 95% CI; 26% to 80%) was significant (P less than 0.0001). Additionally, analysis of plasmid patterns showed that 79% of subjects in the mupirocin group were free of the initial colonizing strain at 3 months. The proportion of hand cultures positive for S. aureus in the mupirocin group after therapy was lower than in the placebo group (2.9% compared with 57.6%). This difference (53%; 95 CI, 30% to 80%) was significant, after adjustment for the frequency of hand carriage at baseline (P less than 0.0001). CONCLUSIONS: When applied intranasally for 5 days, mupirocin calcium ointment is safe and effective in eliminating S. aureus nasal carriage in healthy persons for up to 3 months and appears to have a corresponding effect on hand carriage at 72 hours after therapy.

Removal of nosocomial pathogens from the contaminated glove. Implications for glove reuse and handwashing.

STUDY OBJECTIVE: To evaluate the effectiveness of three different types of handcleansing agents in decontaminating gloved hands that were inoculated with a series of four nosocomial pathogens. DESIGN: A controlled, experimental trial. SETTING: Tertiary care referral center. PATIENTS OR OTHER PARTICIPANTS: Five healthy volunteers participated in all portions of the study. INTERVENTIONS: A standard concentration of one of four representative nosocomial pathogens was placed on the gloved hand, spread, and allowed to dry. One of three different handcleansing agents--a nonmedicated soap, a 60% isopropyl alcohol preparation, or 4% chlorhexidine gluconate--was used to cleanse the gloves, which were cultured using a broth-bag technique. The gloves were then removed and the hands were cultured in a similar manner. MEASUREMENTS AND MAIN RESULTS: The handwashing agents reduced the median log10 counts of organisms to 2.1 to 3.9 after an inoculation of 10(7) colony forming units. The proportion of positive glove cultures for Staphylococcus aureus, 8% to 100%; Serratia marcescens, 16% to 100%; and Candida albicans, 4% to 60% varied greatly after use of the different handcleansers (P less than 0.001), and varied considerably for Pseudomonas aeruginosa, 20% to 48% (P = 0.085). After the gloves were removed, the differences among the observed proportions of hands contaminated with the test organisms varied from 5% to 50%, depending on the handcleansing agent used (P less than 0.001). CONCLUSIONS: In the era of universal precautions these data suggest that it may not be prudent to wash and reuse gloves between patients. Further, handwashing is strongly encouraged after removal of gloves.