Search PubMed⌕ Search

Biomedical subjects

M A Pfaller

Publications and source records attributed to M A Pfaller.

At least 343 records · Page 19Linked to original sources
PubMed1994

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.

Candida↗
PubMed1994

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.

Adult↗
PubMed1993

Recurrent epidemics caused by a single strain of erythromycin-resistant Staphylococcus aureus. The importance of molecular epidemiology.

OBJECTIVE--To compare the accuracy of clinical epidemiologic findings with results of molecular epidemiologic analysis in identifying the source of recurrent epidemics of erythromycin-resistant Staphylococcus aureus (ERSA) infections in a well-baby nursery. DESIGN--Epidemic investigations with retrospective and prospective microbiological surveillance. Staphylococcus aureus isolates were evaluated by plasmid analysis and genotyping. SETTING--A well-baby nursery in a 700-bed university teaching hospital with approximately 250 deliveries per month. PATIENTS--Newborn infants who developed ERSA infections during 1990 and 1991. INTERVENTION--Traditional infection control measures, including cohorting of infected infants and hand washing, were implemented. Personnel were cultured for nasal carriage of S aureus during both epidemics. Employees carrying ERSA were removed from the nursery and treated with mupirocin. RESULTS--In the first epidemic, 15 infants were infected with ERSA. A nursing assistant who cared for most of the infants was found to be a carrier of ERSA. She was removed from the nursery and the epidemic resolved. Fifteen months after the first epidemic ended, an epidemic that involved 11 infants began. The attending physician had a facial furuncle and was found to be a carrier of ERSA. The physician was treated and the epidemic resolved. Plasmid and genotyping showed the ERSA organisms from both epidemics were the same. The employee implicated in the first epidemic did not have the epidemic strain, but the physician who attended during both epidemics did. CONCLUSIONS--Traditional epidemic investigations may lead to false conclusions that can only be recognized with molecular epidemiologic techniques. For these techniques to be useful in the control of outbreaks, plasmid analysis and/or genotyping must be readily available.

Bacterial Typing Techniques↗
PubMed1993

In vitro activity of ceftriaxone and other cephalosporins against 602 clinical isolates of staphylococci from geographically diverse medical centers.

The in vitro activity of ceftriaxone and six additional antimicrobial agents (ceftizoxime, cefoperazone, cefuroxime, fleroxacin, ciprofloxacin, and trimethoprim/sulfamethoxazole) was assessed or 602 recent clinical isolates of staphylococci from six geographically distinct medical centers in North America. All seven antimicrobial agents were active (90-100% of strains susceptible) against oxacillin-susceptible (OS) strains of Staphylococcus aureus (OSSA) and coagulase-negative staphylococci (OSCNS) but had limited activity against oxacillin resistant (OR) staphylococci. Our assessment of the in vitro antistaphylococcal activity of ceftriaxone against contemporary isolates of Staphylococcus aureus and coagulase-negative staphylococci indicates that the activity versus OS staphylococci has not changed over the past decade despite widespread use of the drug. It appears that these agents will continue to be useful for empiric therapy in those centers in which OR strains are uncommon.

Academic Medical Centers↗
PubMed1993

Interpretive criteria and quality control parameters for determining bacterial susceptibility to fosfomycin tromethamine.

Studies with fosfomycin tromethamine disks containing 200 micrograms of fosfomycin and 50 micrograms of glucose-6-phosphate confirmed the following zone diameter criteria for the NCCLS method: < or = 12 mm for resistant (MIC > or = 256 micrograms/ml), 13-15 mm for intermediate (MIC 128 micrograms/ml) and > or = 16 mm for susceptible (MIC < or = 64 micrograms/ml). Additional studies defined acceptable MIC and zone diameter ranges for the following quality control strains: Escherichia coli ATCC 25922, MIC 0.5 to 4.0 micrograms/ml, zone diameter 23 to 29 mm; Staphylococcus aureus ATCC 25923, zone diameter 26 to 32 mm; Pseudomonas aeruginosa ATCC 27813, MIC 2.0 to 8.0 micrograms/ml; and Enterococcus faecalis, ATCC 29212, MIC 16 to 64 micrograms/ml.

Bacteria↗
PubMed1993

Comparison of fixed concentration and fixed ratio options for dilution susceptibility testing of gram-negative bacilli to ampicillin and ampicillin/sulbactam.

Ampicillin combined with sulbactam was tested at both fixed ratio (2:1 and 1:1) and fixed sulbactam concentrations (4 micrograms/ml, 8 micrograms/ml and 16 micrograms/ml) against 2440 consecutively isolated gram-negative bacilli. Sulbactam significantly enhanced the spectrum of ampicillin activity. Overall, at 8 micrograms/ml ampicillin inhibited 50% of the Enterobacteriaceae isolates, whereas 69% to 84% of the isolates were inhibited by the various sulbactam combinations. The widest spectrum of activity for ampicillin/sulbactam was achieved by testing at a fixed sulbactam concentration of 16 micrograms/ml, followed by the 1:1 ratio and the fixed 8 micrograms/ml (84%, 76% and 74% inhibited, respectively). The amount of sulbactam at the susceptible breakpoint concentrations of ampicillin markedly affected the percentage of susceptible strains. Combinations that include 8 micrograms/ml of sulbactam are suggested for consideration.

Ampicillin↗
PubMed1993

Haemophilus test medium versus Mueller-Hinton broth with lysed horse blood for antimicrobial susceptibility testing of four bacterial species.

Studies were undertaken to determine whether broth microdilution susceptibility tests could be standardized by using a single medium for testing fastidious respiratory pathogens. Mueller-Hinton broth with lysed horse blood and the broth version of Haemophilus Test Medium (HTM) were directly compared. Ten orally administered agents were found to give essentially identical results in both media but minor differences were noted. Because the test are easier to read when HTM broth is used, that medium is to be preferred for routine testing of Haemophilus influenzae, Streptococcus pneumoniae, Streptococcus pyogenes and Moraxella catarrhalis isolates by the microdilution procedure.

Anti-Bacterial Agents↗
PubMed1993

Antimicrobial activity and spectrum of rifaximin, a new topical rifamycin derivative.

Rifaximin, a rifamycin derivative, was evaluated in vitro to assess its spectrum and potency against a wide variety of bacteria, yeasts, viruses, and parasites. High concentrations of rifaximin were often used to reflect topically achieved levels since this compound is poorly absorbed by oral route. Like rifampin, rifaximin possessed best activity against Staphylococcus spp. (MIC50 < or = 0.015 microgram/ml), Streptococcus spp. (MIC50s, < or = 0.03-0.12 microgram/ml), Enterococcus spp. (MIC50s, 0.25-2 micrograms/ml), Bacillus cereus (MIC50, 0.06 microgram/ml), Moraxella catarrhalis (MIC50, < or = 0.03 microgram/ml), and Haemophilus influenzae (MIC50, 0.25 microgram/ml). Rifaximin demonstrated potential use as a topical agent for bacterial vaginosis by inhibiting Bacteroides bivius-disiens, Gardnerella vaginalis, Lactobacillus spp., and Mobiluncus spp. strains (all MICs < or = 1 microgram/ml). Strains of Haemophilus ducreyi and Neisseria gonorrhoeae (MIC50s, 0.25 microgram/ml) were also inhibited. However, some organisms associated with genital tract infections were rifaximin resistant, for example, Candida spp., herpes virus, mycoplasmas, Trichomonas vaginalis, and Ureaplasma urealyticum. Clinical trials appear warranted using rifaximin topical concentrations that will minimize mutations to rifamycin resistance.

Administration, Topical↗
PubMed1993

Evaluation of disk susceptibility testing of fosfomycin tromethamine.

Fosfomycin tromethamine is an orally administered fosfomycin that may be used for single-dose therapy of uncomplicated urinary tract infections. At breakpoint concentrations [< or = 128 micrograms/ml plus 25 micrograms/ml glucose-6-phosphate (G-6-P)], fosfomycin tromethamine inhibited > 90% of the 350 bacterial isolates tested. When testing Escherichia coli, Klebsiella spp., and Enterobacter spp., we note that the performance of fosfomycin disks improved when G-6-P was added to the disks. The interpretive error rates were minimized when 200-micrograms fosfomycin disks were supplemented with either 50 or 100 micrograms G-6-P. Using < or = 128 and > or = 256 micrograms/ml as the susceptible and resistant MIC breakpoints, respectively, the regression-analysis-derived disk diffusion zone diameter breakpoints for the 200-micrograms fosfomycin disk supplemented with 50 micrograms of G-6-P are as follows: susceptible, > or = 16 mm; intermediate, 13-15 mm; and resistant, < or = 12 mm.

Bacteria↗
PubMed1993

Application of a biotyping system and DNA restriction fragment analysis to the study of Serratia marcescens from hospitalized patients.

We applied a nine-test biotyping system to the study of 138 Serratia marcescens isolates from 93 patients hospitalized in 33 different hospital bed units. Test reproducibility for a panel of 10 isolates tested in triplicate on 3 separate days was 100%. Overall, the biotyping system delineated 25 strains. In examining strain variation among isolates obtained from multiple anatomic sites over time we found that the same biotype was recovered from tracheal aspirates, urine, wounds, and blood in a given patient and that these strains were carried over time. In general, patients were infected or colonized with their own distinct biotype of S. marcescens. Temporally related isolates from seven surgical intensive care unit (SICU) patients and six unrelated control isolates were typed by biotyping and DNA restriction fragment analysis (RFA). The distribution of biotypes was similar among SICU outbreak and control isolates, with five distinct biotypes among the seven SICU isolates. Each isolate had a different DNA subtype by RFA, confirming the lack of nosocomial transmission of a single strain. These results will be useful in studying the epidemiology of S. marcescens.

Bacterial Typing Techniques↗
PubMed1993

Molecular epidemiology and antimicrobial susceptibility testing. Testing of quinolone-resistant Staphylococcus aureus strains isolated in Brazil.

An outbreak of 20 oxacillin-resistant Staphylococcus aureus (ORSA) bloodstream infections (BSIs) was detected in the intensive care unit (ICU) at Hospital Sao Paulo, Brazil. In a surveillance study, 10% of ICU personnel were defined as chronic nasal carriers of ORSA. Thirteen BSIs and five nasal isolates were available for phage typing, restriction endonuclease analysis of plasmid (REAP) and chromosomal DNA hybridized with 32P rRNA gene probe. Susceptibility testing against select antimicrobial agents, including 11 quinolones, six glycopeptides, and five topical agents, was performed by broth microdilution and the disk diffusion tests. Ten of the 13 BSI isolates and four of the five nasal strains were oxacillin and quinolone resistant. The new fluoroquinolones CI-960 and WIN57273, the glycopeptides, and the topical agents ramoplanin, bacitracin, mupirocin, and novobiocin were most active. Fourteen strains, 12 BSI isolates, and three nasal isolates showed the same REAP profile. Moreover, the same REAP and chromosomal profile was detected in at least nine BSI isolates and in two nasal isolates. These strains were nontypable by phage typing. We concluded that nosocomial cross-transmission of a single, multiresistant strain of S. aureus occurred and that the epidemic reservoir was nasal carriage by ICU personnel.

Bacteriophage Typing↗
PubMed1993

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.

Antigens, Fungal↗
PubMed1993

Restriction endonuclease analysis of plasmid DNA from methicillin-resistant Staphylococcus aureus: clinical application over a three-year period.

OBJECTIVE: To investigate trends in plasmid types of methicillin-resistant Staphylococcus aureus over a 3-year period and determine the clinical impact of plasmid typing. DESIGN: Restriction endonuclease analysis of plasmid DNA (REAP) was used to type 270 clinical isolates. SETTING: A Veterans Affairs Medical Center. RESULTS: Forty-four different REAP types were identified and, of these, 23 appeared only once. Types designed as V1 and V2 were more commonly found in nosocomial cases than in community-acquired cases (p < .05); whereas the K and D types were more common in isolates from community-acquired cases (p < .05). In 30 (11%) isolates, no plasmid was detected. When combined with epidemiological data, REAP typing revealed 4 small outbreaks that would have been missed using traditional epidemiological methods alone. In large outbreaks involving 10 or more cases, REAP typing data revealed unsuspected patterns of transmission. CONCLUSIONS: Multiple plasmid types were present in this endemic setting. Restriction endonuclease analysis of plasmid DNA was a practical and valuable adjunct to traditional epidemiological methods.

DNA Restriction Enzymes↗
PubMed1993

Comparison of pulsed-field gel electrophoresis with isoenzyme profiles as a typing system for Candida tropicalis.

Candida species are important nosocomial pathogens, particularly in immunocompromised and critically ill patients. A variety of methods have been used to differentiate strains, but an optimal system has not been established. We compared methods for typing a panel of nine related isolates of Candida tropicalis from an outbreak of sternal wound infections as well as four unrelated control isolates of this species. (The genetic relationships of the nine isolates in the panel had been confirmed previously by restriction fragment analysis.) Typing was undertaken without knowledge of an isolate's origin. Karyotyping by contour-clamped homogeneous electric field (CHEF) gel electrophoresis failed to distinguish between outbreak and control isolates. However, when chromosome-sized DNA was digested with SfiI, EagI, SacII, or NaeI and the fragments were separated by CHEF electrophoresis, the outbreak isolates were readily identified. The isoenzyme profiles of the outbreak isolates were identical and were distinctly different from those of the control isolates. While both isoenzyme profiles and the modified CHEF procedure were discriminatory, the latter is recommended as a relatively convenient and reproducible technique for comparison of types of C. tropicalis.

Acid Phosphatase↗
PubMed1993

Elimination of Staphylococcus aureus nasal carriage in health care workers: analysis of six clinical trials with calcium mupirocin ointment. The Mupirocin Collaborative Study Group.

Six double-blind, independently randomized studies evaluated the efficacy and safety of calcium mupirocin ointment in eliminating nasal carriage of Staphylococcus aureus among health care workers. Healthy volunteers with stable nasal carriage of S. aureus (n = 339) received either calcium mupirocin ointment (n = 170) or an identical placebo ointment (n = 169) intranasally for 5 days. Nasal carriage was eliminated 48-96 hours after completion of treatment in 130 (91%) of 143 evaluable volunteers receiving mupirocin but in only 8 (6%) of 142 evaluable volunteers receiving placebo. The 85% crude difference represents a 90% pooled (adjusted) estimate of the risk difference (95% confidence interval, 0.86-0.95) and a risk ratio of 16 (P < .0001). This effect of treatment with mupirocin was observed consistently (risk ratio, 8-32) in all six centers. In addition, 96 of the 130 mupirocin-treated volunteers and 1 of the 8 placebo-treated volunteers who were culture-negative at the end of therapy remained free of S. aureus 4 weeks after treatment. Adverse events in each treatment arm were mild and equally frequent. These data, consistent across six institutions, demonstrate that calcium mupirocin ointment administered intranasally for 5 days is safe and effective in eliminating stable nasal carriage of S. aureus.

Administration, Intranasal↗
PubMed1993

RO 23-9424, a new cephalosporin 3'-quinolone: in-vitro antimicrobial activity and tentative disc diffusion interpretive criteria.

The susceptibility of 410 clinical bacterial isolates to RO 23-9424, a novel cephalosporin 3'-quinolone, was determined. Overall, 97% of Enterobacteriaceae and 100% of staphylococci were inhibited by < or = 8.0 mg/L of RO 23-9424. Only 60% of Pseudomonas aeruginosa and 80-90% of Pseudomonas spp. and Xanthomonas maltophilia were inhibited by this concentration. Enterococci and Listeria monocytogenes were resistant to RO 23-9424. Clinical isolates of Moraxella catarrhalis, Streptococcus spp., and Corynebacterium jekeium were all susceptible to < or = 8.0 mg/L of RO 23-9424. This drug's antimicrobial activity was superior to that of its two components fleroxacin and desacetylcefotaxime against the organisms tested. Using < or = 8.0 mg/L and > or = 32 mg/L respectively as the susceptible and resistant MIC breakpoints for RO 23-9424, the regression analysis-derived disc diffusion zone diameter breakpoints for the 30 micrograms disc are: susceptible > or = 19 mm, intermediate 16-18 mm, and resistant < or = 15 mm.

Anti-Infective Agents↗
PubMed1993

Dirithromycin disc susceptibility tests: interpretative criteria and quality control parameters.

Dirithromycin and its bioactive metabolite (erythromycylamine) were compared in vitro to erythromycin against 450 bacterial isolates. Dirithromycin and erythromycylamine did not differ in their in-vitro activity and the two compounds were additive when combined in equal proportions. Both compounds were active against erythromycin-susceptible bacteria but erythromycin was two to four times more potent on a weight-to-weight basis. Interpretive criteria for dirithromycin were not based on achievable blood concentrations since tissue concentrations may be 20-30 times greater than peak serum levels. Dirithromycin-susceptible strains were those with zones > or = 19 mm in diameter (15 micrograms dirithromycin disc) or MIC < or = 2.0 mg/L and resistance was defined as a zone < or = 15 mm or MIC > or = 8.0 mg/L. Interpretive criteria for testing Haemophilus influenzae on Haemophilus Test Medium (HTM) agar were not defined because of the drug's poor activity in the test system used. Two multi-laboratory studies were also undertaken, one to define quality control limits for disc diffusion tests and the other to define broth microdilution MIC control limits for tests with dirithromycin.

Anti-Bacterial Agents↗