Multicenter evaluation of the antimicrobial activity for six broad-spectrum beta-lactams in Venezuela using the Etest method. The Venezuelan Antimicrobial Resistance Study Group

In early 1997, a 15-laboratory surveillance project was initiated in Venezuela to monitor the potency and spectrum of 6 broad-spectrum antimicrobial agents (cefepime, cefotaxime, ceftazidime, piperacillin, piperacillin/tazobactam, and imipenem) tested against approximately 100 organisms per participant center (1297 strains). Ten groups of organisms were tested by the Etest method (AB BIODISK, Solna, Sweden) with results validated by concurrent quality control strain analysis. Results from all centers were tabulated and 96.3% of quality assurance tests were within ranges recommended by the National Committee for Clinical Laboratory Standards. Among the six beta-lactam class drugs tested, imipenem and cefepime were the most active against all isolates tested. Overall, the rank order of susceptibility of the six agents was imipenem (97.2%, susceptible; MIC90 2 micrograms/ml) > cefepime (92.8%; MIC90 6 micrograms/mL) > piperacillin/tazobactam (77.2-83.0%; MIC90 > 256 micrograms/mL) > cefotaxime (72.2%; MIC90 > 256 micrograms/mL) > piperacillin (56.8-65.8%; MIC90 > 256 micrograms/mL) > ceftazidime (64.66%; MIC90 128 micrograms/mL). Both cefepime and imipenem were active against ceftazidime-resistant strains of Enterobactericaeae as well as against Pseudomonas aeruginosa and oxacillin-susceptible staphylococci. Resistance phenotypes consistent with extended spectrum beta-lactamases (ESBLs) and stably derepressed Bush group 1 cephalosporinases were documented in strains of Klebsiella spp. and Enterobacters, respectively. These data should be used to guide empiric therapy with beta-lactams in Venezuela, and additionally will provide a reference statistical baseline to which future studies in this nation can be compared.

Growth medium effect on the antifungal activity of LY 303366

The impact of growth medium selection on antifungal susceptibility testing has been well documented. Previously we described the antifungal characteristics of LY 303366 via time-kill curve methods using RPMI 1640 buffered with 0.165 M morpholinepropane-sulfonic acid as growth medium. The purpose of the current study was to compare the previously reported kill curve results with results obtained using antibiotic medium number three (AM #3) as growth medium. Antifungal activity was assessed via susceptibility testing and time-kill studies in both media. Two isolates each of Candida albicans, C. glabrata, and C. tropicalis were studied. MICs for the six isolates were found to be 10 to 100 times lower in AM #3. Time-kill studies were conducted with multiples of the MIC ranging from 0.125 x MIC to 16 x MIC. LY 303366 exhibited fungicidal (> or = 3 log10 reduction in CFU) activity against all isolates in AM #3; however, fungicidal activity was noted only for three of the six isolates when tested in RPMI. Furthermore, the rate of fungicidal activity was more rapid when AM #3 was utilized. Not only were the rate and extent of activity influenced by choice of media, but the relationships between LY 303366 concentrations and activity were also found to be media dependent. The findings from this study serve to highlight further the importance of media selection for in vitro evaluation of antifungal activity. In vivo studies need to be conducted with LY 303366 to determine which media provides the best correlation between in vitro and in vivo findings.

In vitro activity of cefepime and ceftazidime against 197 nosocomial blood stream isolates of streptococci: a multicenter sample

The increasing prevalence of streptococci as causes of potentially fatal nosocomial bacteremia requires that antimicrobial agents used for empiric therapy in hospitalized patients include both pneumococci and viridans group streptococci as well as beta-hemolytic streptococci in their activity profile. In this study, the in vitro activity of cefepime, a new fourth-generation cephalosporin, was compared with other cephalosporins versus 197 nosocomial blood stream isolates of streptococci (20 Streptococcus pneumoniae, 104 viridans group, and 73 beta-hemolytic) isolated from patients at more than 30 medial centers from 1995 to 1997. Additional agents tested included penicillin, erythromycin, and vancomycin. Overall, cefepime inhibited 83% of the isolates at concentrations < or = 0.5 microgram/mL and 100% at < or = 8 micrograms/mL. By comparison, ceftazidime inhibited 35 and 88% of isolates at the same concentrations. Cefepime was approximately eightfold more potent than ceftazidime against S. pneumoniae, viridans group streptococci, and beta-hemolytic streptococci. Among the 42 isolates with penicillin MICs > 0.12 microgram/mL, 100% were inhibited by cefepime and only 48% by ceftazidime at < or = 8 micrograms/mL. The rank order of activity for all six agents against the 197 isolates was vancomycin > ceftriaxone > cefepime > penicillin > erythromycin > ceftazidime. Based on the results of the present study, cefepime and ceftriaxone were the superior cephalosporins in potency and spectrum for empiric coverage of patients at risk for streptococcal blood stream infections.

Multicenter evaluation of antimicrobial resistance to six broad-spectrum beta-lactams in Colombia using the Etest method. The Colombian Antimicrobial Resistance Study Group

The need for comprehensive and quantitative accurate antimicrobial resistance surveillance systems has become acute as a guide to problem recognition and to focus local interventions. A multilaboratory (10 medical centers) Colombia surveillance project was initiated in early 1997 to monitor the potency and spectrum of six (cefepime, cefotaxime, ceftazidime, cefoperazone/sulbactam, aztreonam, and imipenem) broad-spectrum antimicrobial agents tested against 100 organisms per participant center (802 strains). Ten groups of organisms were tested by a reference-quality method (Etest; AB BIODISK, Solna, Sweden) with results validated by concurrent quality control and additional challenge strain analysis. Results from nine qualifying medical centers were tabulated, and 95.7 to 96.8% of quality assurance tests were within expected ranges. Only cefepime (90.1-100.0% susceptible) and imipenem (96.3-100.0%) were active against all Enterobacteriaceae at > 90% of susceptible isolates using the breakpoint concentrations recommended by the National Committee for Clinical Laboratory Standards. Among ceftazidime- (or cefotaxime- or aztreonam-) resistant Enterobacter spp. and Citrobacter freundii, cefepime remained active, but not cefoperazone with sulbactam. Escherichia coli and Klebsiella spp. strains having resistance phenotypes consistent with extended spectrum beta-lactamase production were discovered in approximately 5 to 10% of isolates. All tested drugs except ceftazidime (31.8-57.7% susceptible) were active against > 94% of oxacillin-susceptible staphylococci. Similar rates of resistance (9.1-14.8%) were observed in Pseudomonas aeruginosa for five of six drugs (not cefotaxime; 15.9% of strains were susceptible). Acinetobacter spp. isolates were most susceptible to imipenem (95.8%), cefepime (86.1%), and cefoperazone/sulbactam (83.3%). Overall for the 1997 order of antimicrobial spectrums for these tested compounds was: imipenem (96.6%) > cefepime (93.6%) > cefoperazone/sulbactam (90.5%) > cefotaxime (74.9%) > aztreonam (74.3% for Gram-negative bacilli only) > ceftazidime (73.2%). These data should be used to guide empiric regimens in Colombia, and additionally will provide a resistance statistical baseline to which future studies in this nation can be compared.

Nosocomial streptococcal blood stream infections in the SCOPE Program: species occurrence and antimicrobial resistance. The SCOPE Hospital Study Group

Nosocomial blood stream infections due to streptococci represent an increasingly important problem, particularly among neutropenic cancer patients. This problem is compounded by the emerging resistance to antimicrobial agents commonly used for empiric or prophylactic treatment of hospitalized patients. In this study, we examined the species distribution and antimicrobial susceptibility profile of 295 streptococcal nosocomial blood stream isolates from more than 30 U.S. medical centers (SCOPE National Surveillance Program). Streptococci accounted for 5.9% of all nosocomial blood stream isolates reported. The viridans group streptococci (VGS) were the most frequently isolated streptococci (50.8%), followed by the beta-haemolytic streptococci (31.9%) and pneumococci (13.2%). The beta-haemolytic streptococci were dominated by serogroup B strains (63%), followed by serogroups A and G. Of these organisms, 193 strains were referred for subsequent monitor susceptibility testing. Approximately 14% of S. pneumoniae, 9.2% of VGS, and 0% of beta-haemolytic streptococci were resistant to penicillin. Ceftriaxone was highly active against virtually all isolates (93-100% susceptible) except the VGS (77% susceptible). The rank order for activity of the four agents tested against the 193 isolates was vancomycin > ceftriaxone > penicillin > erythromycin. Importantly, 69% of the penicillin intermediate and resistant strains of VGS were also resistant to at least one additional antimicrobial (31% resistant to ceftriaxone, 51% resistant to erythromycin, 15% resistant to both ceftriaxone and erythromycin). The relatively poor activity of erythromycin against virtually all streptococci and the frequent association of macrolide resistance with penicillin resistance among the VGS suggests that both macrolides and beta-lactam agents might have limited value as prophylactic agents for dental procedures and in empiric or prophylactic use in neutropenic patients.

Antimicrobial activity of 12 broad-spectrum agents tested against 270 nosocomial blood stream infection isolates caused by non-enteric gram-negative bacilli: occurrence of resistance, molecular epidemiology, and screening for metallo-enzymes

A total of 270 recent nosocomial blood stream isolates of non-Enterobacteriaceae Gram-negative bacilli representing nearly 50 U.S. medical centers were characterized. The numbers of isolates of individual organisms were: Pseudomonas aeruginosa (n = 204), Acinetobacter spp. (n = 48), and Stenotrophomonas maltophilia (n = 18). MICs were determined using the broth microdilution susceptibility method with 12 antimicrobial agents: piperacillin, piperacillin/tazobactam, ceftriaxone, ceftazidime, cefepime, imipenem, ciprofloxacin, ofloxacin, amikacin, gentamicin, tobramycin, and trimethoprim/sulfamethoxazole. Based on current National Committee for Clinical Laboratory Standards breakpoints, rates of resistance to cefepime, ceftazidime, and imipenem were as follows: P. aeruginosa, 3, 9, and 5%; Acinetobacter spp., 2, 37, and 0%; and S. maltophilia, 88.7, 35.3, and 100%, respectively. Trimethoprim/sulfamethoxazole was the most active agent against S. maltophilia (100% susceptible). Twenty-eight isolates of P. aeruginosa that expressed high levels of resistance to ceftazidime (MIC, > 256 micrograms/mL) and imipenem (MIC, > 32 micrograms/mL) were examined for potential metallo-beta-lactamase production by polymerase chain reaction and were found to be negative. Molecular typing of P. aeruginosa isolates revealed many patient-unique strains, but also noted clustering of infections due to isolates of the same DNA type, suggesting possible nosocomial transmission in 9 of 14 medical centers. Given the resistance profile and pathogenic potential of these non-enteric Gram-negative bacilli, considerable effort should be exerted to develop and enforce infection control and antimicrobial utilization practices that will limit the spread of these organisms in the hospital environment.

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.

Comparative antistreptococcal activity of two newer fluoroquinolones, levofloxacin and sparfloxacin

The objective of this study was to evaluate the in vitro activity of sparfloxacin, levofloxacin, ofloxacin, and ciprofloxacin against contemporary strains of streptococci. Susceptibility testing of a panel of 300 recent clinical isolates of streptococci (100 each of beta-hemolytic, viridans group, and Streptococcus pneumoniae) using reference broth microdilution methods was performed, and the results were compared. Sparfloxacin was the most active of the four tested fluoroquinolones, inhibiting 99-100% of all isolates at concentrations of < or = 1 microgram/ml, and was two- to eightfold more potent than the three comparative agents. Levofloxacin was also quite active, inhibiting 98-100% of the isolates at concentrations < or = 2 micrograms/ml. Both sparfloxacin and levofloxacin possess an improved spectrum and potency against contemporary strains of streptococci compared to currently available fluoroquinolones.

An outbreak of Candida parapsilosis prosthetic valve endocarditis

Candida parapsilosis, an important nosocomial pathogen and the most common species of Candida found on the hands of health care workers, is a rare cause of prosthetic valve endocarditis (PVE). From March through June 1994, four cases of C. parapsilosis PVE were diagnosed at a 400-bed community hospital. The mean time to presentation after valve replacement surgery was 148 days (range, 20 to 345). Three of the four patients died of complications of PVE. Multiple environmental cultures were performed, and only one was positive for C. parapsilosis. Cultures from the bypass pump, cell saver, cardioplegia solution, and subsequent valves were all negative. All valve replacements were performed by the same operating room team. Interviews with the surgeon and physician assistant, the only personnel involved in all cases, revealed that their hypoallergenic gloves were subject to frequent tears during valve replacement procedures, often requiring several glove changes per procedure. Hand cultures of personnel were obtained, and cultures from 20 individuals (26%) were positive for C. parapsilosis. Hand cultures of the surgeon and physician assistant obtained 8 months after the last case had surgery were negative for yeasts. Molecular typing of the 3 available case isolates, 14 epidemiologically unrelated patient isolates, 1 environmental isolate, and 20 hand isolates was performed by electrophoretic karyotyping and restriction endonuclease analysis of genomic DNA using restriction enzymes BssHII and EagI followed by pulsed field gel electrophoresis. The three case isolates were identical by restriction endonuclease analysis of genomic DNA, and two of the three shared the same electrophoretic karyotyping profile. The remaining patient, environmental, and hand isolates represented 29 different DNA types and were distinctly different from the case isolates. All of the isolates tested were susceptible to amphotericin B, 5FC, fluconazole, and itraconazole. The circumstantial evidence suggests the probability of glove tears during valve replacement surgery and subsequent transmission of C. parapsilosis to patients.

Nosocomial enterococcal blood stream infections in the SCOPE Program: antimicrobial resistance, species occurrence, molecular testing results, and laboratory testing accuracy. SCOPE Hospital Study Group

Characteristics of nosocomial enterococcal blood stream infection (NEBSI) isolates obtained from patients at 41 U.S. hospitals participating in the SCOPE Program were studied. Isolates from 480 episodes of NEBSI were characterized according to species and antimicrobial susceptibility profile. Selected isolates were also identified to species and vancomycin resistance genotype using polymerase chain reaction based methods. Polymerase chain reaction genotyping and ribotyping were used as genetic markers for molecular epidemiologic typing. Enterococci were the third most common cause of nosocomial blood stream infection in this study, accounting for 11.7% of all isolates reported. Enterococcus faecalis was the most common species (59.6%), followed by E. faecium (19.4%). Species identification errors involving E. faecium, E. durans, E. avium, and E. raffinosus were observed. Vancomycin resistance was observed in 36.4% of all participating medical centers and varied from 11.1% of medical centers in the Northwest to 60.9% of medical centers in the Southwest. Vancomycin-resistant enterococci accounted for 20.6% of NEBSI in the Northeast, 11.4% in the Southeast, 11.1% in the Southwest, and 9.5% in the Northwest regions. VanA genotypes predominated in the Northeast and Southwest, whereas vanA and vanB genotypes were equally prevalent in the Northwest and Southeast. Molecular typing studies identified strains that were unique to individual hospitals as well as strains that were prevalent in several different hospitals. NEBSI with vancomycin-resistant enterococci continues to escalate among hospitalized patients in all geographic areas of the USA.

The clinical microbiology laboratory and infection control: emerging pathogens, antimicrobial resistance, and new technology

The clinical microbiology laboratory is an essential component of an effective infection control program. Laboratory personnel have a broad range of technologies, from traditional methods of detecting and identifying organisms to modern molecular typing methods, that they can use to support and enhance the efforts of the infection control staff. If the infection control team applies these technologies appropriately, it can prevent problems and solve nosocomial mysteries efficiently. In this era of cost-containment, staff members in the laboratory and in the infection control program must work hard to communicate their unique and shared goals, needs, and problems. If the laboratory and infection control personnel cooperate and collaborate rather than compete, both programs will be successful and the patients and the hospital will benefit because the risk of nosocomial infections and the frequency of resistant organisms will be reduced.

Vancomycin-resistant Enterococcus raffinosus: molecular epidemiology, species identification error, and frequency of occurrence in a national resistance surveillance program

Enterococcal blood stream infections are the third most common among all nosocomial blood stream infections in the United States and the occurrence of glycopeptide (vancomycin, teicoplanin) resistance in these isolates has markedly increased. Control of hospital-acquired infections with vancomycin-resistant enterococci requires high quality antimicrobial susceptibility test methods and species identification procedures as a supplement to epidemiologic investigation and appropriate infection control procedures. In this report, bacteremias caused by Enterococcus avium (BioMerieux Vitek, Hazelwood, MO, USA) were observed to be Enterococcus raffinosus infections (six of eight cases; 1.1% of all cases) when reference biochemical identification methods were applied. The vancomycin-susceptible E. raffinosis (two strains) and E. avium (two strains) had unique phenotypic and genotypic molecular profiles. In contrast, four vancomycin-resistant E. raffinosus strains (van A by polymerase chain reaction) from a single institution had the same phenotypic and molecular (PCR, PFGE, ribotyping) pattern, indicating clonal dissemination among four patients over a 66-day period. Clinical laboratories should be aware of the high probability that van A genes may be transferred from Enterococcus faecium or Enterococcus faecalis to other more rarely encountered Enterococcus species. Also contemporary, widely used commercial identification systems may fail to accurately identify those rare species. Errors appear to be most prevalent for E. avium, Enterococcus durans, and E. raffinosus based on the experience of the SCOPE Program.

Update on antifungal resistance

Overuse of antifungal agents has resulted in the selection of naturally resistant Candida species, as well as expression of resistance from previously susceptible species resulting from genetic mutations and/or selection of resistant subpopulations. Strategies for the appropriate use of antifungal agents need to be developed to prevent further development of resistance.

Inducible amp C beta-lactamase producing gram-negative bacilli from blood stream infections: frequency, antimicrobial susceptibility, and molecular epidemiology in a national surveillance program (SCOPE)

A surveillance study of nosocomial blood stream infections [Surveillance and Control of Pathogens of Epidemiologic Importance (SCOPE)] was conducted during a 14-month period in 1995 to 1996 in approximately 50 American medical centers. Among the 4725 blood stream infections, the etiologic agent was Enterobacter spp. in 230, Citrobacter freundii in 24, and Serratia marcescens in 65. The vast majority of these isolates (89%) had been sent to the University of Iowa including 198 Enterobacter spp. (46 Enterobacter aerogenes, 141 Enterobacter cloacae, 11 other Enterobacter spp.), 23 C. freundii, and 62 S. marcescens. Because these species are capable of producing Amp C beta-lactamase, we examined their susceptibility to 12 broad-spectrum antimicrobial agents. The frequency of resistance to ceftazidime and the molecular epidemiology of ceftazidime-resistant strains was also examined. Among the Enterobacter spp. and C. freundii isolates, resistance to third generation cephalosporins (ceftazidime, ceftriaxone) and broad-spectrum semisynthetic penicillins (piperacillin), with or without an enzyme inhibitor (piperacillin/tazobactam), was high, e.g., 35 to 50%. The S. marcescens isolates were quite susceptible to all agents tested. Both imipenem and cefepime were active against virtually all isolates tested including 84 stably derepressed Amp C-producing ceftazidime-resistant strains of Enterobacter spp. and C. freundii. The overall rank order of activity for the six best agents against these Amp C-producing strains was: imipenem (100% susceptible) > amikacin = cefepime (98.6%) > ciprofloxacin = gentamicin = ofloxacin (93.6 to 94.0%). Molecular typing studies of ceftazidime-resistant E. cloacae using an automated ribotyping system, as well as pulsed-field gel electrophoresis, indicated that although clonal spread of a single strain occurred in some of the medical centers, most of the episodes of bacteremia were caused by patient-unique strains. Control of these resistant organisms will require attention to microbiologic recognition of phenotypes, to infection control practices, and to limiting the overuse of certain extended spectrum beta-lactams.

A review of the in vitro activity of meropenem and comparative antimicrobial agents tested against 30,254 aerobic and anaerobic pathogens isolated world wide

The in vitro activity of meropenem (formerly SM-7738), a new carbapenem, was compared with that of imipenem and five other broad-spectrum antimicrobials (ceftazidime, cefotaxime, piperacillin, piperacillin/tazobactam, and ciprofloxacin) against 30,254 clinically significant pathogens isolated in nine countries worldwide. Overall, the carbapenems, meropenem and imipenem, were the most active drugs. Meropenem was four- to 64-fold more active than imipenem against Gram-negative bacteria, including the Enterobacteriaceae, Pseudomonas aeruginosa, Burkholderia cepacia, Haemophilus influenzae, and Neisseria meningitidis. Meropenem was also quite active against ceftazidime-resistant strains of Enterobacteriaceae, inhibiting 87.5 to 100% at < or = 4 micrograms/ml. In contrast, imipenem was four- to eight-fold more active than meropenem against Gram-positive species, including methicillin-susceptible strains of Staphylococcus aureus and Staphylococcus epidermidis, Streptococcus pneumoniae, and Enterococcus faecalis. Among the anaerobes, strains resistant to meropenem or imipenem were encountered very rarely. These extensive data provide additional in vitro support for the clinical use of meropenem as a broad spectrum antimicrobial agent active against key pathogenic species of bacteria.

Variations in fluconazole susceptibility and DNA subtyping of multiple Candida albicans colonies from patients with AIDS and oral candidiasis suffering one or more episodes of infection

Five Candida albicans colonies from each infection in AIDS patients receiving fluconazole therapy for oropharyngeal candidiasis over a 2-year period were evaluated by antifungal susceptibility testing and DNA subtyping, and the results were correlated with clinical response to determine the occurrence of clinically significant selection of more-resistant C. albicans over multiple infections. A total of 534 C. albicans isolates were obtained from 38 patients who exhibited 84 episodes of infection. Antifungal susceptibility testing revealed that the MICs for 93% of the isolates were < or = 8.0 microg/ml and the MICs for 7% of the isolates were > or = 64 microg/ml. DNA subtyping revealed 70 different subtypes, with 78% of patients with one infection exhibiting one DNA subtype and 80% of patients with more than one infection exhibiting multiple DNA subtypes. Also, patients who had multiple infections had lower CD4 counts than those with single infections. Differences between the single-infection group and the multiple-infection group regarding the number of DNA subtypes and CD4 counts were both statistically significant. Of the 74 evaluable infections all were successfully treated with regular-dose (100-mg/day) fluconazole, except for three patients who ultimately responded to higher-dose fluconazole. Only one patient may have shown clinically significant selection of a more-resistant C. albicans strain over multiple courses of treatment. Interestingly, MICs reached only 8.0 microg/ml, even though doses of 400 mg of fluconazole were necessary for clinical cure.

International Conference for the Development of a Consensus on the Management and Prevention of Severe Candidal Infections

Because of the rapidly increasing incidence of serious candidal infections, a consensus conference of 22 investigators from the United States, Europe, and Japan was held to discuss strategies for the prevention and treatment of deep-organ infections caused by Candida species. Commonly asked questions concerning the management of candidal infections were selected for discussion by the participating investigators. Possible answers to the questions were developed by the investigators, who then voted anonymously for their preferences. In certain instances, unanimity or a strong consensus was the result. In all cases, the full spectrum of responses was recorded and is presented in this report. The forms of candidal infection addressed included candidemia, candiduria, hepatosplenic candidiasis (chronic systemic candidiasis), candidal endophthalmitis, and candidal peritonitis. Prevention and treatment strategies were considered for patients who have undergone surgery, for neutropenic and nonneutropenic patients, and for patients who have undergone bone marrow and solid organ transplantation. The therapeutic roles of amphotericin B (standard and lipid formulations) and the azoles were considered.

Accuracy of the Vitek system for antimicrobial susceptibility testing Enterobacteriaceae bloodstream infection isolates: use of "direct" inoculation from Bactec 9240 blood culture bottles

A recent investigation indicates that rapid antimicrobial susceptibility tests (AST) can affect patient therapy leading to reductions in health-care costs for some patient populations. However, there is little information relative to the often performed direct inoculation of positive blood culture bottles into rapid AST systems. AST results of direct inoculated Vitek (bioMerieux Vitek, Hazelwood, MO, USA) GNS cards were compared to those inoculated per package insert recommendations and a reference broth microdilution test using 50 consecutive Enterobacteriaceae bloodstream infection isolates. Escherichia coli (44% of isolates), Klebsiella ssp. (30%), and six other members of this family were tested against 15 antimicrobial agents. The direct inoculation method produced only two false-susceptible (0.3%), seven false-resistant (0.9%; six different drugs), and 48 minor errors (6.4%). The GNS cards inoculated in the usual, recommended manner had no very major error, and 7.5% combined major and minor errors. If the results of the urinary infection-specific drugs (nitrofurantoin, trimethoprim/sulfamethoxazole; not appropriate for bacteremia therapy) and ampicillin/sulbactam were deleted, both Vitek inoculation methods yielded results well within acceptable limits (< or = 4.5% overall error). These results indicate that the direct inoculation method of Vitek GNS cards from Enterobacteriaceae bloodstream infections (detected by Bactec 9240, Becton-Dickinson, Cockeysville, MD, USA) performed as well as the NCCLS broth microdilution test. Thus, a procedural modification of this type could further accelerate rapid access to accurate AST data.

Evaluation of growth characteristics on blood agar and eosin methylene blue agar for the identification of Candida (Torulopsis) glabrata

Candida albicans and Candida (Torulopsis) glabrata are the most common species of yeast encountered in the clinical laboratory. In this study, we sought to evaluate simple means of screening cultures for the presence or absence of C. glabrata. Twelve thousand five hundred (12,500) consecutive cultures were evaluated for sufficient yeast growth to warrant identification. When detected (369 isolates), the amount of growth on eosin methylene blue agar (EMB) versus sheep blood agar (BAP) (both incubated in 5% CO2), wet mount morphology, and germ tube production were evaluated. All germ tube-negative yeasts were definitively identified using the Vitek YBC card. Of the 369 yeast isolates included in this study, 225 were C. albicans, 102 C. glabrata, and 42 other Candida species. Growth on EMB was greater than BAP for 92 isolates; all identified as C. glabrata. When EMB growth was equal to or less than BAP, 10 isolates were C. glabrata and 267 were other Candida ssp. An accurate presumptive identification of C. glabrata may be made using the observation of greater growth on EMB versus BAP. When coupled with the germ tube test, the majority of yeast isolates could be identified by these simple methods in our laboratory.

Role of molecular epidemiology in infection control

Molecular typing methods have enabled infection control personnel to investigate outbreaks and endemic nosocomial infections more quickly and thoroughly than they could have with basic epidemiologic and microbiologic methods. This article reviews molecular typing methods that have been used successfully in the practice of hospital epidemiology. Included is an explanation of the basic principles of these methods and a description of their strengths and weaknesses.

Antifungal pharmacodynamic characteristics of fluconazole and amphotericin B tested against Candida albicans

Time-kill curves were determined for three isolates of Candida albicans tested against fluconazole and amphotericin B at multiples of the MIC. Fluconazole produced fungistatic activity, with concentration-related growth effects observed over a narrow range of concentrations. Amphotericin B exhibited fungicidal activity, with enhancement of activity over a broader range of concentrations.

Antifungal susceptibility testing: technical advances and potential clinical applications

The clinical application of in vitro antifungal susceptibility testing has been limited by a lack of reproducibility and uncertain clinical relevance. As a result of several collaborative studies, the National Committee for Clinical Laboratory Standards (NCCLS) has proposed a standardized antifungal susceptibility test method, NCCLS M27-T. More convenient, user-friendly methods (microdilution broth and stable gradient technology) have been evaluated, and the potential for a similar process with a disk diffusion method is apparent. Adaptation of the standard method for susceptibility testing of filamentous fungi appears promising. The existence of a standardized method facilitates meaningful analysis of studies addressing the issue of clinical relevance of antifungal susceptibility testing. Correlation of MICs with clinical response to therapy is beginning to emerge, most notably in relation to fluconazole and itraconazole therapy for oropharyngeal candidiasis associated with infection with the human immunodeficiency virus. This accumulated experience with antifungal susceptibility testing allows us to provide several specific recommendations for antifungal susceptibility testing in the clinical laboratory. Application of this developing technology to new antifungal agents and other disease states will enhance our ability to effectively deal with the emerging problem of fungal infection.

Stable azole drug resistance associated with a substrain of Candida albicans from an HIV-infected patient

Oral candidiasis is one of the earliest and most frequent complications of a failing immune system in HIV-infected individuals. For several years, oral candidiasis has been treated effectively with azole drugs, the one most frequently used is fluconazole. Unfortunately, extensive use of the drug for treatment and prophylaxis has led to treatment failure in an increasing number of patients. In most of these cases, strains of C. albicans isolated from the infection are less susceptible to fluconazole. The development of azole resistance in strains of C. albicans has been studied biochemically and more recently with molecular techniques. One excellent example of the development of azole resistance in C. albicans has been documented in a series of 17 C. albicans isolates from a single patient over a 2-year period. During this time, the patient experienced 14 episodes of oral candidiasis and was treated with increasing doses of fluconazole. Molecular and biochemical analyses confirms that the isolates are the same strain of C. albicans and that the resistance in these isolates is stable over 600 generations, suggesting that the changes in this strain are genetic in nature. In addition, the development of resistance is correlated with the identification of a substrain or variant of the original strain, as identified by restriction fragment length polymorphism (RFLP) analysis with the moderately repetitive probe, Ca3. The analysis of this series of isolates demonstrates that azole drug resistance is associated with several small genetic changes, each of which contributes to the overall resistance of the strain. Clearly, continual use of azole drugs by a patient can select for genetic changes that render oral candidiasis refractory to treatment.

In vitro evaluation of contemporary beta-lactam drugs tested against viridans group and beta-haemolytic streptococci

Streptococci continue to be prevalent causes of mild as well as of serious, life-threatening infections. Furthermore, some species harbor antimicrobial resistances (pneumococcus, viridans gr. streptococci) that compromise effective chemotherapy with beta-lactam drugs or other antimicrobial classes. In this study, the potency and spectrum of 12 beta-lactams was assessed versus 274 contemporary isolates of viridans group and beta-haemolytic streptococci using reference methods. Cefotaxime and ceftriaxone (MIC90s, 0.015 to 2 micrograms/ml, 84 to 100% susceptible) were consistently most potent among the agents tested. Ceftazidime (MIC90s, 0.25 to 8 micrograms/ml) and ticarcillin (MIC90s, 0.5 to > 32 micrograms/ml) were least active among the cephalosporins and penicillins, respectively. When 25% pooled serum was added to the reference test medium, ceftriaxone activity decreased fourfold, and cefotaxime remained highly active. As penicillin/beta-lactam-resistant streptococci with altered penicillin-binding protein target sites become more prevalent, only a few "third-generation" cephems seem to have sustained activity when used alone or possibly with a carefully selected co-drug. Routine testing of these species against beta-lactams and alternative drugs should be encouraged to detect emerging resistance patterns.

In vitro susceptibilities of clinical yeast isolates to a new echinocandin derivative, LY303366, and other antifungal agents

LY303366 is a new semisynthetic echinocandin derivative with potent, broad-spectrum fungicidal activity. We investigated the in vitro activity of LY303366, amphotericin B, flucytosine (5FC), fluconazole, and itraconazole against 435 clinical yeast isolates (413 Candida and 22 Saccharomyces cerevisiae isolates) obtained from over 30 different medical centers. MICs for all five antifungal agents were determined by the National Committee for Clinical Laboratory Standards method with RPMI 1640 test medium. LY303366 was also tested in antibiotic medium 3 as specified by the manufacturer. Overall, LY303366 was quite active against all of the yeast isolates when tested in RPMI 1640 (MIC at which 90% of the isolates are inhibited [MIC90], 1.0 microg/ml) but appeared to be considerably more potent when tested in antibiotic medium 3 (MIC90, 0.03 microg/ml). When tested in antibiotic medium 3, LY303366 was 16- to >2,000-fold more active than itraconazole, fluconazole, amphotericin B, or 5FC against all species except Candida parapsilosis. When tested in RPMI 1640, LY303366 was comparable to amphotericin B and itraconazole and more active than fluconazole and 5FC. All of the isolates for which fluconazole and itraconazole had elevated MICs (> or = 128 and > or = 2.0 microg/ml, respectively) were inhibited by < or = 0.007 microg of LY303366/ml when tested in antibiotic medium 3 and < or = 0.5 microg/ml when tested in RPMI 1640. Based on these studies, LY303366 has promising antifungal activity and warrants further in vitro and in vivo investigation.