Outbreak of severe Pseudomonas aeruginosa infections caused by a contaminated drain in a whirlpool bathtub.

During a 14-month period, 7 patients with hematological malignancies acquired serious infections caused by a single strain of multiply resistant Pseudomonas aeruginosa. A case-control study, culture surveys, and pulsed-field gel electrophoresis implicated a whirlpool bathtub on the unit as the reservoir. All case patients and 32% of control patients used this bathtub (P=.003). The epidemic strain was found only in cultures of samples taken from the bathtub. The drain of the whirlpool bathtub, which was contaminated with the epidemic strain, closed approximately 2.54 cm below the drain's strainer. Water from the faucet, which was not contaminated, became contaminated with P. aeruginosa from the drain when the tub was filled. The design of the drain allowed the epidemic strain to be transmitted to immunocompromised patients who used the whirlpool bathtub. Such tubs are used in many hospitals, and they may be an unrecognized source of nosocomial infections. This potential source of infection could be eliminated by using whirlpool bathtubs with drains that seal at the top.

Colony morphology of Candida spp. as a guide to species identification.

The presence of colony projections, often referred to as "feet," have typically been considered a characteristic of Candida albicans. In the current study that examined the colony morphology of numerous different species of Candida, several clinical isolates of Candida tropicalis and Candida krusei were also noted to produce "feet." The medium and growth conditions under which colony projections were produced by these species were characterized.

A cluster of serious Escherichia coli infections in a neonatal intensive-care unit.

A cluster of serious Escherichia coli infections was identified among patients in a neonatal intensive-care unit. Infection control staff identified the outbreak because they realized that E coli rarely caused infections in this unit. Pulsed-field gel electrophoresis confirmed that one strain of E coli was transmitted among patients.

Vitek GPS card susceptibility testing accuracy using direct inoculation from BACTEC 9240 blood culture bottles.

The emergent need for antimicrobial susceptibility testing (AST) data for the therapy of bacteremic patients has led to the development of rapid methods and local procedure modification of some commercial AST products such as the direct inoculation from blood culture systems. We compared the Vitek GPS card results using direct and standardized inoculation with a reference broth microdilution method for 112 consecutive staphylococcal bloodstream infections (seven drugs). Among the 28 Staphylococcus aureus strains, 0%-3.6% total error/drug was observed with both Vitek inoculation procedures. However, the only oxacillin-resistant strain was not detected (100% true very-major error). For 84 coagulase-negative staphylococci (CNS), the direct inoculation procedure had an 11.9% very-major error rate for oxacillin, ampicillin-sulbactam, and cephalothin, plus 4.8% very-major error rate for ciprofloxacin and trimethoprim-sulfamethoxazole (total error rate 4.8%-16.7% for five of seven drugs compared). The Vitek direct inoculation procedure routinely missed 20.4% of oxacillin-resistant CNS strains. The use of Vitek direct inoculation procedures for staphylococcal bloodstream infection isolates (from BACTEC 9240 cultures) produced serious false-susceptible results; this procedure should be avoided in favor of routine package insert-recommended Vitek procedures or other reference-quality overnight incubation susceptibility tests.

Quality control guidelines for National Committee for Clinical Laboratory Standards recommended broth macrodilution testing of amphotericin B, fluconazole, and flucytosine.

Amphotericin B, fluconazole, and flucytosine (5FC) were tested in a multilaboratory study to establish quality control (QC) guidelines for yeast antifungal susceptibility testing. Ten candidate QC strains were tested in accordance with National Committee for Clinical Laboratory Standards M27-P guidelines against the three antifungal agents in each of six laboratories. Each laboratory was assigned a unique lot of RPMI 1640 broth medium as well as a lot of RPMI 1640 common to all of the laboratories. The candidate QC strains were tested 20 times each against the three antifungal agents in both unique and common lots of RPMI 1640. A minimum of 220 MICs per drug per organism were generated during the study. Overall, 95% of the MICs of amphotericin B, fluconazole, and 5FC fell within the desired 3 log2-dilution range (mode +/- 1 log2 dilution). Excellent performance with all three drugs was observed for Candida parapsilosis ATCC 22019 and C. krusei ATCC 6258. With these strains, on-scale 3 log2-dilution ranges encompassing 96 to 99% of the MICs of all three drugs were established. These two strains are recommended for QC testing of amphotericin B, fluconazole, and 5FC. Reference ranges were also established for an additional four strains for use in method development and for training. Four strains failed to perform adequately for recommendation as either QC or reference strains.

Selection of candidate quality control isolates and tentative quality control ranges for in vitro susceptibility testing of yeast isolates by National Committee for Clinical Laboratory Standards proposed standard methods.

The National Committee for Clinical Laboratory Standards has developed a proposed standard method for in vitro antifungal susceptibility testing of yeast isolates (National Committee for Clinical Laboratory Standards, document M27-P, 1992). In order for antifungal testing by the M27-P method to be accepted, reliable quality control (QC) performance criteria must be developed. In the present study, five laboratories tested 10 candidate QC strains 20 times each against three antifungal agents: amphotericin B, fluconazole, and 5-fluorocytosine. All sites conformed to the M27-P standards and used a common lot of tube dilution reagents and RPMI 1640 broth medium. Overall, 98% of MIC results with amphotericin B, 95% with fluconazole, and 92% with 5-fluorocytosine fell within the desired 3-log2 dilution range (mode +/- 1 log2 dilution). Excellent performance with all three antifungal agents was observed for six strains: Candida albicans ATCC 90028, Candida parapsilosis ATCC 90018, C. parapsilosis ATCC 22019, Candida krusei ATCC 6258, Candida tropicalis ATCC 750, and Saccharomyces cerevisiae ATCC 9763. With these strains, 3-log2 dilution ranges encompassing 94 to 100% of MICs for all three drugs were established. Additional studies with multiple lots of RPMI 1640 test medium will be required to establish definitive QC ranges.

Antifungal activity of a new triazole, D0870, compared with four other antifungal agents tested against clinical isolates of Candida and Torulopsis glabrata.

D0870 is a new triazole agent with potent, broad-spectrum antifungal activity. We investigated the in vitro activity of D0870, fluconazole, itraconazole, amphotericin B, and 5-fluorocytosine (5FC) against 319 clinical isolates of Candida spp. and Torulopsis glabrata. In vitro susceptibility testing was performed using a microdilution broth method performed according to NCCLS guidelines. D0870 was very active (MIC90 of 0.12 microgram/ml and 0.5 microgram/ml at 24 and 48 h incubation, respectively) against all of the yeast isolates. D0870 was 2- to 32-fold more active than amphotericin B and 2- to 8500-fold more active than 5FC. By comparison with the other triazoles, D0870 was generally 2- to 16-fold more active than itraconazole and > or = 16-fold more active than fluconazole. More than half (53%) of C. albicans isolates with elevated fluconazole and itraconazole MICs (> or = 128 micrograms/ml and > 8.0 micrograms/ml, respectively) were inhibited by < or = 1.0 microgram/ml of D0870. Based on these studies, D0870 has promising antifungal activity and warrants further in vitro and in vivo investigation.

Multicenter comparison of a colorimetric microdilution broth method with the reference macrodilution method for in vitro susceptibility testing of yeast isolates.

This multicenter study was performed to compare a colorimetric microdilution method with the NCCLS M27-P reference macrodilution method for the testing of yeast isolates against amphotericin B, fluconazole, and 5-fluorocytosine (5FC). Testing was performed on ten yeast isolates in five independent laboratories. All sites tested each isolate a total of 20 times with both methods. MICs were read after 48 h incubation. The macrodilution MIC reference range was defined as the modal MIC +/- 1-log2 dilution for each organism-antifungal agent combination. Agreement between the M27-P reference range results and the microdilution MICs was 86% with amphotericin B, 90% with fluconazole, and 93% with 5FC. Based on these data, it is apparent that new approaches, such as the colorimetric microdilution method, will provide MIC values comparable to the M27-P macrodilution method in a format that is more practical for use in a busy clinical laboratory.

Effects of blood medium supplements on activities of newer cephalosporins tested against enterococci.

This comparative study determined the effect of blood on the antienterococcal activities of the newer cephalosporins. Standardized disk diffusion susceptibility tests were performed with 57 strains of enterococci (30 Enterococcus faecalis strains) on Mueller-Hinton agar with and without 5% sheep blood supplementation. Twelve cephalosporins representing five different structural groups (based on the 7-alpha position substitution) were tested. The greatest frequency of activity enhancement by blood was observed with cefdaloxime and cefdinir (7-alpha hydroxyimino group) against E. faecalis. Cephalosporins with a 7-alpha methoxyimino group (cefpodoxime, cefepime, and cefpirome) had marked increases in zone diameters (3 to > 9 mm) when tested with the blood supplement. Cephems with 7-alpha amino or carboxy substitutions did not demonstrate any enhanced activity. Awareness of this phenomenon is important for the interpretation and accuracy of cephalosporin susceptibility testing.

Species identification and determination of high-level aminoglycoside resistance among enterococci. Comparison study of sterile body fluid isolates, 1985-1991.

Enterococcus spp. have become the third most common cause of nosocomial infections. High-level aminoglycoside resistance (HLR), an important clinical concern, has been associated with some species of the enterococci. We evaluated the Vitek and API 20S systems for species identification and the Vitek for the detection of HLR. Enterococci from nosocomial infections (208 strains) at the University of Iowa Hospital (1985-1991) were tested by Vitek, API 20S, and reference methods. The error rate for species identification was 6.7% for the API 20S and 5.8% for the Vitek Gram-positive identification (GPI) cards. Both systems tended to incorrectly identify other enterococcal species as Enterococcus faecium. HLR was found in Enterococcus faecalis and E. faecium isolates only. The highest rates of HLR to streptomycin alone (17.9%) and with gentamicin (13.5%) was observed among E. faecalis strains, and to gentamicin alone (7.3%) was found among E. faecium isolates. No apparent differences in HLR rates were found from year-to-year over the 7-year enterococcus sample interval. Susceptibility errors for Vitek were among the streptomycin tests only. Our results demonstrated acceptable performance by the Vitek cards for enterococcal species identification and the detection of HLR. API 20S also provided an acceptable ability to speciate the enterococci within its data base, however, both systems must be improved by adding other clinical important Enterococcus species.

Value of the Hybritech ICON Candida Assay in the diagnosis of invasive candidiasis in high-risk patients.

A total of 314 sera from 114 patients at risk for invasive candidiasis were analyzed for the presence of antigenemia using the Hybritech enzyme immunoassay (EIA) for detection of Candida mannan in serum (ICON Candida Assay, Hybritech Inc., San Diego, CA). Fourteen patients (12%) had invasive candidiasis documented by positive blood cultures, deep biopsy culture, and histopathology or autopsy, and five patients had probable invasive candidiasis based on a single positive blood culture and no additional signs of candidiasis. Nine patients had candiduria, 43 patients had mucous membrane colonization, 25 patients were not colonized but received empiric amphotericin B, and 18 patients were not colonized and not treated with amphotericin B. All sera were enzymatically extracted, heat treated, and reacted in a solid-phase sandwich EIA. Test results were read visually and with the ICON reader. The sensitivity and specificity of the mannan EIA in detection of documented invasive candidiasis was 86% and 92%, respectively. The positive predictive value was 60% and the negative predictive value was 98%. Among all patients with invasive candidiasis (documented plus probable), the sensitivity was 68%, the positive predictive value 62%, and the negative predictive value 94%. Specimens were positive within 3 days of the first positive culture in 11 (79%) of 14 patients with documented invasive candidiasis.

Diagnosis of disseminated candidiasis in hospitalized patients using the Cand-Tec latex agglutination assay.

A total of 1,303 sera from 202 patients at risk for disseminated candidiasis were analyzed for the presence of Candida antigen using a commercially available latex agglutination test (Cand-Tec). Twenty-three patients had disseminated candidiasis documented by positive blood cultures, deep biopsy culture and histopathology or autopsy. Six patients had transient candidemia, 15 patients had candiduria, 62 patients were not colonized yet treated empirically with amphotericin B, and 46 patients were not colonized and not treated with amphotericin B. The sensitivity and specificity of the Candida antigen test for the diagnosis of disseminated candidiasis was 87% and 36% (threshold titer of greater than or equal to 1:2), 70% and 60% (greater than or equal to 1:4), and 30% and 85% (greater than or equal to 1:8), respectively. In contrast to previous studies we were unable to demonstrate a prognostic role for the Candida antigen test in patients with documented disseminated candidiasis. The lack of sensitivity and specificity of the Cand-Tec Candida antigen test precludes its use in the diagnosis of disseminated candidiasis.