In vitro activity and selection of disk content for disk diffusion susceptibility tests with trovafloxacin.

The activity of the new fluoroquinolone trovafloxacin (CP-99,219) was compared with that of ciprofloxacin and ofloxacin against 517 bacterial isolates representing 50 different species. Against members of the family Enterobacteriaceae, all three drugs showed good in vitro activity. Against most anaerobic bacteria, Staphylococcus, Streptococcus, and Enterococcus species, trovafloxacin was four- to sixteenfold more active than ciprofloxacin. For disk diffusion testing, 10 micrograms trovafloxacin disks gave satisfactory results. Tentative criteria are proposed for use during clinical studies.

Comparison of three methods for recovery of yeasts from hands of health-care workers.

This study compared three methods for the detection of yeasts on the hands of 30 nurses: (i) direct finger impressions on inhibitory mold agar plates, (ii) bag washes in brain heart infusion broth, and (iii) bag washes in brain heart infusion broth supplemented with gentamicin and vancomycin. The antimicrobial agent-supplemented bag wash method identified the greatest number of yeast carriers and yielded the most yeast isolates, especially non-C. albicans Candida spp.

Tentative interpretive criteria and quality control parameters for in-vitro susceptibility testing of Neisseria gonorrhoeae to two fluoroquinolones (PD 131628 and grepafloxacin (OPC 17116)).

The susceptibility of Neisseria gonorrhoeae to PD 131628 and grepafloxacin (OPC 17116) was evaluated by agar dilution and disc diffusion methods. A tentative susceptibility category for both fluoroquinolones included strains for which the MICs are < or = 0.06 mg/L and the zones of inhibition are > or = 38 mm for PD 131628 and > or = 37 mm for grepafloxacin. Quality control studies with N. gonorrhoeae ATCC 49226 suggested that agar dilution MIC limits were 0.002-0.008 mg/L and 0.004-0.03 mg/L for PD 131628 and grepafloxacin, respectively. The zone size limits were 50-58 mm for PD 131628 and 44-52 mm for grepafloxacin.

Laboratory-associated infections and biosafety.

An estimated 500,000 laboratory workers in the United States are at risk of exposure to infectious agents that cause disease ranging from inapparent to life-threatening infections, but the precise risk to a given worker unknown. The emergence of human immunodeficiency virus and hantavirus, the continuing problem of hepatitis B virus, and the reemergence of Mycobacterium tuberculosis have renewed interest in biosafety for the employees of laboratories and health care facilities. This review examines the history, the causes, and the methods for prevention of laboratory-associated infections. The initial step in a biosafety program is the assessment of risk to the employee. Risk assessment guidelines include the pathogenicity of the infectious agent, the method of transmission, worker-related risk factors, the source and route of infection, and the design of the laboratory facility. Strategies for the prevention and management of laboratory-associated infections are based on the containment of the infectious agent by physical separation from the laboratory worker and the environment, employee education about the occupational risks, and availability of an employee health program. Adherence to the biosafety guidelines mandated or proposed by various governmental and accrediting agencies reduces the risk of an occupational exposure to infectious agents handled in the workplace.

Antibacterial activity of WY-49605 compared with those of six other oral agents and selection of disk content for disk diffusion susceptibility testing.

The in vitro antimicrobial activity of an oral penem, WY-49605, was compared with those of six other oral antimicrobial agents against 598 bacterial isolates representing 51 different species. WY-49605 exhibited good activity against most gram-positive bacteria and members of the family Enterobacteriaceae. It had little activity against nonfermenting gram-negative bacilli, Enterobacter spp., Serratia spp., enterococci, Staphylococcus haemolyticus, and methicillin-resistant Staphylococcus aureus. Its activity was unaffected by the beta-lactamases of Neisseria gonorrhoeae, Haemophilus influenzae, and staphylococci. Disk diffusion susceptibility tests were performed with 5-, 10-, 15-, and 30-micrograms WY-49605 disks. The 5-micrograms disk is recommended, with tentative breakpoints of > or = 16 mm for susceptibility (MIC, < or = 2.0 microgram/ml) and < or = 12 mm for resistance (MIC, > or = 8.0 micrograms/ml).

Prosthetic valve endocarditis caused by Corynebacterium afermentans subsp. lipophilum (CDC coryneform group ANF-1).

Corynebacteria are important causes of endocarditis in individuals with valvular prostheses. We report the first published case of prosthetic valve endocarditis caused by the newly defined species Corynebacterium afermentans subsp. lipophilum (former CDC coryneform group ANF-1). The isolate was recovered from a perivalvular abscess specimen and 5 of 15 Bactec blood cultures after 7 to 15 days of incubation. The isolation, identification, and susceptibility testing of Corynebacterium species are discussed.

Tentative criteria for determining the in vitro susceptibilities of Haemophilus influenzae, including quality control parameters, to two fluoroquinolones (grepafloxacin and PD 131628).

Grepafloxacin (OPC 17116) and PD 131628 were evaluated against 150 Haemophilus influenzae isolates to propose susceptibility testing criteria for both broth dilution and disk diffusion procedures using haemophilus test medium. Grepafloxacin-susceptible isolates are defined as those for which minimum inhibitory concentrations (MICs) are < or = 0.06 micrograms/ml and zones of inhibition are > or = 27 mm. PD 131628-susceptible strains of H. influenzae included those that exhibited MICs < or = 0.03 micrograms/ml, and the zones were > or = 32 mm. All MICs were well below concentrations that can be achieved in the blood and tissues of patients treated with either study drug. Criteria for defining a resistant category cannot be determined until strains with elevated MICs are available for study. The proposed quality control guidelines for H. influenzae ATCC 49247 and the disk test are 32-39 mm in diameter for grepafloxacin and 34-42 mm for PD 131628. The preliminary broth microdilution MIC control limits for this strain are 0.002-0.016 micrograms/ml for grepafloxacin and 0.002-0.008 micrograms/ml for PD 131628.

Comparison of broth macrodilution, broth microdilution, and E test antifungal susceptibility tests for fluconazole.

A comparison of the E test, the broth microdilution test, and the reference broth macrodilution susceptibility test of the National Committee for Clinical Laboratory Standards for fluconazole susceptibility testing was performed with 238 clinical isolates of Candida species and Torulopsis (Candida) glabrata. An 80% inhibition endpoint MIC was determined by the reference broth macrodilution method after 48 h of incubation. The MICs obtained by the two study methods were read after 24 and 48 h of incubation. Overall, excellent agreement within 2 doubling dilutions was obtained between the broth microdilution and the broth macrodilution methods for the combined results for all species at both 24 h (93%) and 48 h (94%). The correlation of 24-h MIC endpoints between the E test and the broth macrodilution methods was 37% for T. glabrata, 56% for Candida tropicalis, 93% for Candida albicans, and 90% for other Candida species. The percent agreement at 48 h ranged from 34% for T. glabrata to 97% for Candida species other than C. albicans and C. tropicalis. These initial results support the further evaluation of the E test as an alternative method for fluconazole susceptibility testing of Candida species.

High frequency of yeast carriage on hands of hospital personnel.

The hands of 36 nurses and 21 nonnursing hospital employees were tested by culture with a modification of the broth wash technique. Seventy-five percent of the nurses and 81% of the nonnurses were found to harbor yeasts on their hands; 58% of nurses and 38% of nonnurses were carrying Candida spp.

Comparison of BACTEC Plus 26 and 27 media with and without fastidious organism supplement with conventional methods for culture of sterile body fluids.

We compared the BACTEC Plus 26/27 culture system (Becton Dickinson Diagnostic Instrument Systems, Sparks, Md.) with and without fastidious organism supplement with conventional centrifugation preparation and plating for the recovery and speed of detection of microorganisms. A total of 1,101 sterile body fluid specimens were collected and processed at five hospital laboratories, yielding 234 (21%) positive cultures. Of the 176 isolates considered clinically significant, 133 (76%) were recovered by both the BACTEC system and conventional culture, while 28 (16% [P < 0.005]) were recovered by BACTEC only and 11 (6%) were recovered by conventional culture alone. There were no statistically significant differences in the speed of detection of microbial growth. It was found that BACTEC, with or without the addition of fastidious organism supplement, exhibited improved sensitivity for the recovery of microorganisms, including fastidious bacteria.

Necrotizing pneumonia caused by mixed infection with Actinobacillus actinomycetemcomitans and Actinomyces israelii: case report and review.

Actinobacillus actinomycetemcomitans is an important cause of human pulmonary infections, either alone or with Actinomyces species. It may be critical to isolate Actinobacillus in patients with pulmonary infection for selection of an effective antimicrobial regimen. Clindamycin has superseded penicillin as the sole antimicrobial drug for anaerobic bacterial necrotizing pneumonia and abscess. In the case presented herein, therapy with clindamycin failed to halt worsening necrotizing pneumonia or to prevent hematogenous dissemination. After clindamycin-resistant A. actinomycetemcomitans in addition to Actinomyces israelii were isolated, the patient was treated with penicillin, ciprofloxacin, and cefazolin and was ultimately cured.

Evaluation of two commercial systems for identification of coagulase-negative staphylococci to species level.

Bloodstream (224) and urine (nine) isolates of coagulase-negative staphylococci (CNS) were evaluated using MicroScan Pos ID and Rapid Pos ID panels. A modification of the conventional method of Kloos and Schleifer served as the reference method. The isolates were selected to include a broad range of CNS species, including 44 S. epidermidis, 50 S. hominis, 39 S. warneri, 33 S. capitis, 21 S. haemolyticus, 12 S. simulans, 11 S. saprophyticus, six S. cohnii, five S. lugdunensis, three S. xylosus, four S. auricularis, two S. schleiferi, two S. intermedius, and one S. sciuri. The Pos ID panel had an overall rate of agreement (correct plus probably correct) with the reference method of 79%, including 95% for S. epidermidis, 95% for S. haemolyticus, 64% for S. hominis, 67% for S. simulans, 79% for S. warneri, and 100% for S. saprophyticus. The Rapid Pos ID panel had an overall rate of agreement (correct plus probably correct) of 76%, including 91% for S. epidermidis, 90% for S. haemolyticus, 64% for S. hominis, 58% for S. simulans, 77% for S. warneri, and 100% for S. saprophyticus. Both systems are acceptable for the identification of the clinically significant species S. haemolyticus, S. saprophyticus, and S. epidermidis, but are less reliable for the infrequently isolated species of CNS.

Comparison of the Septi-Chek AFB and BACTEC systems and conventional culture for recovery of mycobacteria.

The performance of the Septi-Chek AFB system was compared with that of the BACTEC radiometric system and that of Lowenstein-Jensen agar slants (LJ) for detection of mycobacteria in clinical specimens. A total of 642 specimens were cultured; 61 (9.5%) yielded mycobacteria. Mycobacterium tuberculosis (34 isolates) and Mycobacterium avium complex (25 isolates) were the predominant species isolated. Of the 61 culture-positive specimens, 30 were smear positive and 31 were smear negative. Overall, 95% of the positive specimens were detected by Septi-Chek and BACTEC (100% of M. tuberculosis isolates) and 75% by LJ (82% of M. tuberculosis isolates). The mean times to detection were 15 days for BACTEC, 23 days for Septi-Chek, and 27 days for LJ. Of the 30 smear-positive specimens, 100% were recovered by Septi-Chek and BACTEC and 90% were recovered by LJ. Of the 31 smear-negative specimens, 90% were detected by Septi-Chek and BACTEC and 61% were detected by LJ. The Septi-Chek and BACTEC systems are superior to the conventional (LJ) mycobacterial culture method. Although Septi-Chek requires more time for the detection of mycobacteria than BACTEC, it is comparable in terms of overall recovery.

Sensitivity of surveillance cultures for the detection of methicillin-resistant Staphylococcus aureus in a nursing-home-care unit.

This study compared the sensitivity of nasal culture alone versus multiple-site cultures and single versus duplicate sampling for the detection of methicillin-resistant Staphylococcus aureus (MRSA)-colonized individuals in a nursing-home population. Repeat culture of 68 specimens collected from 35 colonized subjects yielded identical results for 57 specimens, (84%), and 89% of the colonized residents (31 of 35) were identified by the first culture of multiple sites. A single nares culture detected 27 (77%) of 35 (first screen) and 29 (83%) of 35 (second screen) residents colonized with MRSA at any site. The most cost-effective screening would consist of a nasal culture only or combined with a gastrostomy tube site, if applicable. To identify all colonized individuals, however, it would be necessary to culture more than one specimen from multiple sites on each resident.

Antimicrobial therapy for methicillin-resistant Staphylococcus aureus colonization in residents and staff of a Veterans Affairs nursing home care unit.

OBJECTIVE: To evaluate the effect of antimicrobial therapy on patients and staff colonized with methicillin-resistant Staphylococcus aureus (MRSA) in a skilled nursing facility and to assess the role of the environment as a potential reservoir for MRSA in the nursing home setting. DESIGN: As part of a comprehensive program to control an MRSA outbreak in a nursing home, patients and staff colonized with MRSA received 1 of 3 antimicrobial decolonization regimens depending upon the site and extent of colonization. Followup cultures were performed during therapy and on days 2, 7, 14, and 30 following the completion of therapy. Cultures of the patients' inanimate environment (pajamas, sheet, and floor) were obtained during and after therapy. Antimicrobial susceptibility tests were performed on 54 MRSA isolates obtained before and 44 MRSA isolates recovered after therapy. SETTING: A 120-bed Veterans Affairs nursing home care unit. PARTICIPANTS: Thirty-six patients and 7 staff nurses colonized with MRSA at 1 or more sites. INTERVENTION: Decolonization therapy with rifampin, trimethoprim-sulfamethoxazole, and clindamycin used alone or in various combinations for 5 or 10 days in conjunction with other infection control measures employed to combat the MRSA outbreak. RESULTS: Twenty (56%) of the 36 NHCU patients were either persistently colonized or became recolonized with MRSA during the 30-day followup period. Positive cultures on day 3 during therapy frequently identified patients who subsequently exhibited persistent or recurrent colonization. Before therapy, 92% of MRSA isolates were susceptible to rifampin, whereas only 43% of the isolates obtained after therapy were susceptible. Sixteen (80%) of 20 patients with persistent or recurrent colonization had rifampin-resistant strains of MRSA isolated after therapy. Twenty-three (18%) of 125 environmental cultures obtained during and after therapy from patients who exhibited persistent or recurrent colonization were positive for MRSA, in contrast to 9 (8%) of 107 from patients who were successfully decolonized. CONCLUSIONS: The decolonization component of the outbreak control program was judged to be ineffective and potentially hazardous because colonization persisted or recurred in more than half of the patients, and substantial antimicrobial resistance was noted in MRSA stains isolated after therapy. Resistance, especially to rifampin, and possibly re-acquisition of MRSA from other human or environmental sources were 2 factors that appeared to impede the decolonization effort.

Necrotizing tracheitis caused by Corynebacterium pseudodiphtheriticum: unique case and review.

The occasional pathogenicity of nondiphtheria corynebacteria in both immunocompetent and immunocompromised individuals is now well established. Previously described sites of infection include heart valves, wounds, urinary tract, and lungs. This report of necrotizing tracheitis caused by Corynebacterium pseudodiphtheriticum illustrates the widening spectrum of infections caused by these organisms. A 54-year-old man developed respiratory distress and symptoms of upper airway obstruction unresponsive to inhaled bronchodilators, systemic corticosteroids, or intravenous erythromycin. A spirometry flow-volume loop demonstrated fixed upper airway obstruction. Fiberoptic bronchoscopic examination revealed a circumferential inflammatory process partially occluding the tracheal lumen. Gram staining revealed gram-positive rods typical of corynebacteria, and cultures of tracheal tissue yielded C. pseudodiphtheriticum resistant to erythromycin and clindamycin. There was no clinical or laboratory evidence for exotoxin or cell-associated toxins. Treatment with intravenous penicillin resulted in resolution of the inflammatory process and eradication of the organisms, as assessed by subsequent cultures.

Methicillin-resistant Staphylococcus aureus in extended-care facilities: experiences in a Veterans' Affairs nursing home and a review of the literature.

OBJECTIVES: To delineate the spread of methicillin-resistant Staphylococcus aureus (MRSA) in a nursing home care unit (NHCU), determine its consequences, and discuss this experience in the context of reports from other nursing homes. DESIGN: Observational and descriptive; routine and special surveillance for MRSA, including a facility-wide prevalence survey; characterization of MRSA isolates by disk diffusion and agar dilution susceptibility studies and restriction enzyme analysis of plasmid (REAP) DNA. SETTING AND PATIENTS: A 120-bed skilled nursing facility that is an integral part of the Veterans' Affairs Medical Center (VAMC), Portland, Oregon. The patients are predominantly elderly men with severe underlying diseases and functional impairments. RESULTS: An asymptomatic carrier brought MRSA into the NHCU in December 1987. During the next 15 months, 24 additional MRSA cases were detected. A prevalence survey conducted in March 1989 indicated that 39 (34%) of the 114 patients and 8 (7%) of the 117 employees were colonized or infected with MRSA. All strains were resistant to ciprofloxacin. REAP DNA indicated that 37 of 41 strains recovered in the March survey had identical patterns. Although 16 episodes of MRSA infection occurred in NHCU residents during 1988 through 1989, the outbreak had little effect on overall patterns of infectious morbidity and mortality in the facility. The outbreak, however, did result in an increased MRSA caseload at the medical center's acute-care division. CONCLUSIONS: During the last three years, MRSA colonization and infection have become common in the NHCU at the Portland VAMC; this experience parallels that reported by several nursing homes in other parts of the country.

Comparison of large volume culture to other methods for isolation of microorganisms from dialysate.

Patients on continuous ambulatory peritoneal dialysis (CAPD) who reside long distances from a CAPD center often use community medical laboratories to document and manage episodes of peritonitis. We examined the feasibility of using large volume cultures as an alternative to more costly and labor intensive methods and to enhance earlier recovery of microorganisms from these patients. Three methods of processing dialysate from patients on CAPD were compared: (a) inoculation of 400 mL dialysate into a transfer bag (Baxter Healthcare, Inc., Round Lake, IL) containing 100 mL of 5-fold concentrate of trypticase-soy broth: (b) inoculation of 5 mL into each of two Bactec bottles (Johnston Laboratories, Towson, MD): and (c) centrifugation of 50 mL and culture of the sediment without white cell lysis on plated media and two Bactec bottles. Of the 58 specimens cultured, 34 (59%) were positive by one or more methods. Antimicrobial activity was detected in 20/58 (34%) dialysates, which represent 54% of all no-growth cultures. Of the 34 culture-positive specimens, microorganisms were recovered on plated media in 22 (65%); by the centrifugation system in 32 (94%); by the routine Bactec system in 28 (82%); and by large volume culture in 30 (88%). The large volume culture system is an acceptable alternative to the more costly Bactec System and the labor intensive centrifugation method but does not significantly improve recovery of microorganisms.

Comparison of two commercial broth-culture systems for microbial detection in dialysates of patients on continuous ambulatory peritoneal dialysis.

The capability of two commercial systems was studied for microbial detection in dialysis effluents from patients on continuous ambulatory peritoneal dialysis (CAPD). Two methods of processing dialysate from patients on CAPD were compared: (a) direct inoculation of 10 ml of dialysate into a single bottle broth culture system (Signal; Oxoid, U.S.A., Columbia, Maryland) and 5 ml into each of two BACTEC blood culture bottles (Johnston Laboratories, Towson, Maryland); and (b) centrifugation of 50 ml of dialysate and culture of the sediment in an Oxoid bottle. Of the 196 specimens cultured, 99 (51%) yielded growth. Recovery rates of significant isolates were 95% for the BACTEC system, 89% for the Oxoid system, and 88% for the centrifugation-Oxoid system. Recovery of eight isolates from the Oxoid system was by subculture rather than a visual "signal." The Oxoid system is a practical, cost-effective, alternative culture method for effluents from CAPD patients in laboratories not having access to the BACTEC system.