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A Bolmström

Publications and source records attributed to A Bolmström.

16 recordsLinked to original sources
PubMed2001

Clinical isolate of vancomycin-heterointermediate Staphylococcus aureus susceptible to methicillin and in vitro selection of a vancomycin-resistant derivative.

A Staphylococcus aureus strain with low-level heteroresistance to vancomycin (designated MER) but susceptible to methicillin was isolated from an outpatient with conjunctivitis who did not receive any glycopeptide antibiotics. Incubation of the parent strain, MER, with increasing concentrations of vancomycin led to rapid selection of a stable progeny homogeneously resistant to vancomycin. Electron micrographs of strain MER showed enhanced cell wall thickness and abnormal septations typically seen with methicillin-resistant S. aureus having intermediate susceptibility to vancomycin.

Adult↗
PubMed2001

Improved detection of amphotericin B-resistant isolates of Candida lusitaniae by Etest.

Both intrinsic and acquired resistance to amphotericin B have been documented for Candida lusitaniae. Amphotericin B remains the drug of choice for many critical fungal infections, and the detection of resistance is essential to monitor treatment effectively. The limitations of the National Committee for Clinical Laboratory Standards (NCCLS) reference methodology for detection of amphotericin B resistance are well documented, and several alternative methods have been proposed. Etest assays with RPMI and antibiotic medium 3 (AM3) agar were compared to the NCCLS M27-A broth macrodilution method using AM3 for amphotericin B resistance testing with 49 clinical isolates of C. lusitaniae. The panel included nine isolates with known or presumed resistance to amphotericin B on the basis of in vivo and/or in vitro data. The distribution of amphotericin B MICs by Etest with RPMI ranged from 0. 032 to 16 microg/ml and was bimodal. All of the putatively resistant isolates were inhibited by amphotericin B at >/=0.38 microg/ml and could be categorized as resistant using this breakpoint. Etest with AM3 yielded a broader amphotericin B MIC range (0.047 to 32 microg/ml), and there were six putatively resistant isolates for which MICs were >1 microg/ml. The separation of putatively susceptible and resistant isolates was less obvious. Broth macrodilution with AM3 generated a unimodal distribution of MICs (ranging from 0.032 to 2 microg/ml) and failed to discriminate most of the putatively resistant isolates at both 24 and 48 h. Etest using RPMI and, to a lesser extent, using AM3 provided better discrimination between amphotericin B-resistant and -susceptible isolates of C. lusitaniae.

Amphotericin B↗
PubMed2001

Evaluation of Etest method for determining posaconazole MICs for 314 clinical isolates of Candida species.

The performance of the Etest for posaconazole (SCH 56592) susceptibility testing of 314 isolates of Candida spp. was assessed against the National Committee for Clinical Laboratory Standards (NCCLS) microdilution broth method. The NCCLS method employed RPMI 1640 broth medium, and MICs were read after incubation for 48 h at 35 degrees C. MICs were determined by Etest for all 314 isolates with RPMI agar containing 2% glucose (RPG agar) and were read after incubation for 48 h at 35 degrees C. The Candida isolates included C. albicans (n = 174), C. glabrata (n = 57), C. tropicalis (n = 31), C. parapsilosis (n = 39), C. krusei (n = 5), C. guilliermondii (n = 6), and C. lusitaniae (n = 2). The Etest results correlated well with reference MICs. Overall agreement was 95%, and agreements for individual species were as follows: C. krusei, 100%; C. albicans, 98%; C. tropicalis, 97%; C. glabrata, 93%; C. parapsilosis, 85%; C. guilliermondii, 83%; and C. lusitaniae, 50%. The problem of trailing end points was minimized with RPG agar, and good agreement with broth dilution MICs was obtained when discernible growth within an established ellipse was ignored. The Etest method using RPG agar appears to be a useful method for determining posaconazole susceptibilities of Candida species.

Antifungal Agents↗
PubMed2001

Evaluation of Etest method for determining caspofungin (MK-0991) susceptibilities of 726 clinical isolates of Candida species.

The performance of the Etest for testing the susceptibilities to caspofungin (MK-0991) of 726 isolates of Candida spp. was assessed against the National Committee for Clinical Laboratory Standards (NCCLS) microdilution broth method. The NCCLS method employed RPMI 1640 broth medium, and MICs were read after incubation for 48 h at 35 degrees C. MICs were determined by Etest for all 726 isolates with RPMI agar containing 2% glucose (RPG) and were read after incubation for 48 h at 35 degrees C. The Candida isolates included Candida albicans (n = 486), Candida glabrata (n = 96), Candida tropicalis (n = 51), Candida parapsilosis (n = 47), Candida krusei (n = 11), Candida lusitaniae (n = 2), and Candida guilliermondii (n = 33). In addition, a subset of 314 isolates were also tested by Etest using Casitone agar (CAS) and antibiotic medium 3 agar (AM3). The Etest results obtained using RPG correlated well with reference MICs. Overall agreement was 94% with RPG, 82% with CAS, and 79% with AM3. When RPG was used, agreement ranged from 79% for C. parapsilosis to 100% for C. krusei, C. lusitaniae, and C. guilliermondii. When CAS was used, agreement ranged from 0% for C. lusitaniae to 100% for C. glabrata. With AM3, agreement ranged from 0% for C. lusitaniae to 100% for C. guilliermondii. All three media supported growth of each of the Candida species. Etest results were easy to read, with sharp zones of inhibition. In most instances (75%) where a discrepancy was observed between the Etest and the reference method, the Etest MIC was lower. The Etest method using RPG appears to be useful for determining caspofungin susceptibilities of Candida species.

Anti-Bacterial Agents↗
PubMed2001

Evaluation of current methods for detection of staphylococci with reduced susceptibility to glycopeptides.

The sensitivity and specificity of seven methods (agar dilution, broth microdilution, Etest at 0.5 and 2.0 McFarland (McF) inocula, two agar screening methods, and population studies [PS]) were evaluated in a double-blind study involving 284 methicillin-resistant Staphylococcus aureus (MRSA) strains and 45 Staphylococcus strains with reduced susceptibilities to vancomycin (SRSV). The results were compared to the population analysis profile-area under the curve ratio method (PAP-AUC ratio compared to that of Mu3) as described by Wootton et al. The agar screening method using brain heart infusion agar (6 microg of vancomycin per ml) gave a sensitivity of 22% and a specificity of 97%. A similar method using Mueller-Hinton agar (5 microg of vancomycin per ml) gave a sensitivity of 20% and a specificity of 99%. The PS method detected 34 false positives (12%) and gave a sensitivity of 71% and a specificity of 88%. Etest using 0.5 and 2.0 McF inocula gave sensitivities and specificities of 82 and 93% and of 96 and 97%, respectively. The best Etest interpretative criteria for the 2.0 McF inoculum was > or =8 mg of vancomycin per liter and > or =8 microg teicoplanin per ml or > or =12 microg of teicoplanin per ml. The direct colony suspension inoculum for this method was found to be equally accurate in detecting (hetero-)glycopeptide-intermediate S. aureus compared to the overnight broth inoculum preparation method. Agar dilution and broth microdilution using the NCCLS breakpoint criteria for vancomycin gave sensitivities and specificities of 20 and 100% and of 11 and 100%, respectively. Using the Etest with a 2.0 McF inoculum, six different media were assessed against a selection of SRSV (n = 48) and MRSA (n = 12). Brain heart infusion agar yielded the highest sensitivity and specificity values: 88 and 88%, respectively.

Anti-Bacterial Agents↗
PubMed2000

In vitro susceptibility testing of filamentous fungi: comparison of Etest and reference microdilution methods for determining itraconazole MICs.

The performance of the Etest for itraconazole susceptibility testing of 50 isolates of filamentous fungi was assessed in comparison with the National Committee for Clinical Laboratory Standards (NCCLS) proposed standard microdilution broth method. The NCCLS method employed RPMI 1640 broth medium, and MICs were read after incubation for 48 h at 35 degrees C. Etest MICs were determined with RPMI agar containing 2% glucose and with Casitone agar and were read after incubation for 24 h (Aspergillus spp. and Rhizopus spp.) and 48 h (all species except Rhizopus spp.) at 35 degrees C. The isolates included Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Aspergillus terreus, Fusarium spp., Pseudallescheria boydii, Rhizopus spp., Paecilomyces variotii, and an Acremonium sp. Overall agreement between Etest and microdilution MICs was 96% with RPMI agar and 80% with Casitone agar. The agreement was 100% for all species except Rhizopus spp. (83%) and Paecilomyces varioti (0%) with RPMI agar. When Casitone agar was used, the agreement ranged from 50% with Rhizopus spp. to 100% with Fusarium spp., P. boydii, P. varioti, and an Acremonium sp. Notably, for Aspergillus spp., the agreement between itraconazole Etest MICs read at 24 h and reference microdilution MICs read at 48 h was 100% with both RPMI and Casitone agar. Both media supported the growth of all filamentous fungi tested. Where a discrepancy was observed between Etest and the reference method, the Etest MIC was generally higher. The Etest method using RPMI agar appears to be a useful method for determining itraconazole susceptibilities of Aspergillus spp. and other filamentous fungi.

Antifungal Agents↗
PubMed1998

Evaluation of Etest for determining in vitro susceptibility of yeast isolates to amphotericin B.

We evaluated the performance of Etest using several different agar media for testing of amphotericin B against 660 clinical isolates of yeast species including Candida albicans, C. glabrata, C. tropicalis, C. parapsilosis, C. lusitaniae, C. krusei, Candida spp., Cryptococcus neoformans, and Saccharomyces cerevisiae. Two of the C. lusitaniae isolates represented strains with high-level amphotericin B resistance. All isolates were tested by NCCLS microdilution methods with RPMI 1640 medium and by Etest using RPMI agar with 2% glucose (RPG). A subset of 108 isolates was also tested by Etest using RPG, antibiotic medium 3 agar (AM3), Casitone agar (CAS), and Mueller-Hinton agar (MHA). The overall agreement between the NCCLS reference method and Etest using RPG was 98.3%. All of the Etest methods identified the two resistant strains (MICs, 4.0 to 16 micrograms/mL), whereas the reference method failed to distinguish them from 18 other isolates with MICs of 2.0 micrograms/mL. Among the 20 isolates with reference MICs of 2.0 micrograms/mL, 12 had MICs > or = 2.0 micrograms/mL when tested by Etest with RPG (range 2.0 to 16 micrograms/mL) compared with eight with AM3, two with CAS, and five with MHA. These data indicate that Etest identifies subpopulations of yeast isolates with high amphotericin B MICs. The greater sensitivity of Etest for detection of amphotericin B resistance should be exploited in future surveillance studies.

Amphotericin B↗
PubMed1998

Evaluation of the Etest method for determining fluconazole susceptibilities of 402 clinical yeast isolates by using three different agar media.

The performance of the Etest for fluconazole susceptibility testing of 402 yeast isolates was assessed against the National Committee for Clinical Laboratory Standards (NCCLS) microdilution broth method. The NCCLS method employed RPMI 1640 broth medium, and MICs were read after incubation for 48 h at 35 degrees C. Etest MICs were determined with RPMI agar containing 2% glucose (RPG), Casitone agar (CAS), and Mueller-Hinton agar (MHA) and were read after incubation for 48 h at 35 degrees C. The yeast isolates included Candida albicans (n = 161), Candida glabrata (n = 41), Candida tropicalis (n = 35), Candida parapsilosis (n = 29), Candida krusei (n = 32), Candida lusitaniae (n = 31), Candida species (n = 19), Cryptococcus neoformans (n = 40), and miscellaneous yeast species (n = 14). The Etest results correlated well with reference MICs. Overall agreement was 94% with RPG, 97% with CAS, and 53% with MHA. When RPG was used, agreement ranged from 89% for Candida spp. to 100% for C. krusei. When CAS was utilized, agreement ranged from 93% for Cryptococcus neoformans to 100% for C. tropicalis, C. parapsilosis, C. lusitaniae, Candida spp., and miscellaneous yeast species. With MHA, agreement ranged from 17% for C. parapsilosis to 90% for C. krusei. Both RPG and CAS supported growth of all yeast species, whereas growth on MHA was comparatively weaker. Etest results were somewhat easier to read on CAS. The Etest method using either RPG or CAS, but not MHA, appears to be a viable alternative to the NCCLS reference method for determining fluconazole susceptibilities of yeasts.

Agar↗
PubMed1997

Antimicrobial Susceptibility of Klebsiella pneumoniae Producing Extended-Spectrum beta-lactamase (ESBL) Isolated in Hospitals in Brazil.

The prevalence of klebsiella pneumoniae producing extended-spectrum beta-lactamase (ESBL) has been increasing all over the world. Infections caused by ESBL producing isolates are difficult to detect with current susceptibility tests, and are difficult to treat. ESBLs confer resistance to all currently available beta-lactam, except carbapenems. In addition, ESBL production is usually associated with resistance to other classes of antimicrobial agents such as aminoglycosides and quinolones. The objective of this study was to evaluate the in vitro susceptibility patterns of ESBL producing K pneumoniae isolated in Brazil. Seventy-two strains were tested using E test against 30 antimicrobial agents, including carbapenems, second and third generation cephalosporins, aminoglycosides, quinolones, and some new compounds. The most active compounds (i.e. 100% susceptibility) were meropenem (MIC90, 0.125µg/mL), imipenem (MIC90, 0.25µg/mL), and cefotetan (MIC90, 2µg/mL). Ciprofloxacin (MIC90, 1µg/mL, 94% susceptibility) and cefepime (MIC90, 6µg/mL, 92% susceptibility), were also very active against our collection of ESBL producing K pneumoniae. None of the six aminoglycosides showed good activity against these strains (16% to 41% susceptibility) and only 39% of the isolates were susceptible to piperacillin/tazobactam. The results of our study indicated that the carbapenems are the most active compounds against ESBL producing L pneumoniae in Brazil, and ciprofloxacin remains very active against these strains. Cefotetan and cefepime were also very active against ESBL producing K.pneumoniaein Brazil; however, further studies are necessary to evaluate the role of these cephalosporins in the treatment of infections due to ESBL producing strains.

Journal Article↗
PubMed1996

Quality control guidelines for National Committee for Clinical Laboratory Standards--recommended broth macrodilution testing of ketoconazole and itraconazole.

Ketoconazole and itraconazole were tested in a multilaboratory study to establish quality control (QC) guidelines for yeast antifungal susceptibility testing. Two isolates that had been previously identified as QC isolates for amphotericin B, fluconazole, and flucytosine (Candida parapsilosis ATCC 22019 and Candida krusei ATCC 6258) were tested in accordance with the National Committee for Clinical Laboratory Standards M27-P guidelines. Each isolate was tested 20 times with the two antifungal agents in the five laboratories by using a lot of RPMI 1640 unique to each laboratory as well as a lot common to all five laboratories, thus generating 200 MICs per drug per organism. Overall, 96 to 99% of the MICs for each drug fell within the desired 3-log2 dilution range (mode +/- 1 log2 dilution). By using these data, 3-log2 dilution QC ranges encompassing 98% of the observed MICs for three of the organism-drug combinations and 94% of the observed MICs for the fourth combination were established. These QC ranges are 0.064 to 0.25 micrograms/ml for both ketoconazole and itraconazole against C. parapsilosis ATCC 22019 and 0.125 to 0.5 micrograms/ml for both ketoconazole and itraconazole against C. krusei ATCC 6258.

Antifungal Agents↗
PubMed1996

Multisite reproducibility of the Etest MIC method for antifungal susceptibility testing of yeast isolates.

A multicenter study was performed to establish the interlaboratory reproducibility of Etest, to provide an additional comparison of Etest MICs with reference broth macrodilution MICs, and to develop some tentative quality control (QC) guidelines for using Etest for antifungal susceptibility testing of Candida spp. Two QC strains, Candida parapsilosis ATCC 22019 and Candida krusei ATCC 6258, were tested by Etest against amphotericin B, fluconazole, flucytosine, itraconazole, and ketoconazole in each of four laboratories. The QC strains were tested 20 times each against the five antifungal agents by using a common lot of RPMI agar. A total of 80 MICs per drug per strain were generated during the study. Overall, 98 to 100% of the MICs fell within a 3 log2 dilution range for the respective yeast-antifungal agent combinations. The level of agreement of Etest MICs with broth macrodilution MICs was 86 to 100% with amphotericin B (C. krusei and C. parapsilosis), itraconazole (C. krusei and C. parapsilosis), flucytosine (C. parapsilosis), and fluconazole (C. parapsilosis). A lower level of agreement was observed with ketoconazole (C. krusei and C. parapsilosis). Although all participants reported identical Etest MICs, the MICs of flucytosine and fluconazole when tested against C. krusei fell well above the upper limits of the reference range for this strain. The tentative QC limits for the two QC strains and five antifungal agents when tested by the Etest methodology are the same as the QC limits when tested by the reference broth macrodilution method for amphotericin B and C. krusei, itraconazole and C. krusei, flucytosine and C. parapsilosis, fluconazole and C. parapsilosis, and itraconazole and C. parapsilosis. The Etest QC ranges are 1 dilution broader (4-dilution range) than the reference macrodilution method QC ranges for ketoconazole and C. krusei, amphotericin B and C. parapsilosis, and ketoconazole and C. parapsilosis.

Amphotericin B↗
PubMed1994

Determinations of minimum bactericidal concentrations, kill curves, and postantibiotic effects with the Etest technology.

The bactericidal activity of antimicrobial agents is generally determined following broth dilution minimum inhibitory concentrations (MIC) procedures. These methods are cumbersome, require advanced technical experience, and lack proven reproducibility. Etest (AB Biodisk, Solna, Sweden) is a predefined antimicrobial gradient on a plastic carrier strip that is used to generate a precise MIC on an agar plate. A pilot study was conducted to investigate whether a drug's bactericidal effect could be assessed by transferring the "growth-inhibition pattern" from the Etest MIC ellipse onto a drug-free agar plate. The transfer was performed using four techniques of replica plating, a filter method, drug inactivation, and sampling of growth alongside the Etest strip. Defined antimicrobial-organism models were used to determine the minimum bactericidal concentrations (MBCs), killing curves (KCs), and postantibiotic effects (PAEs) of several drugs. Preliminary results suggest that the Etest provides an alternative method for studies determining the MBCs, KCs, and PAEs of various antimicrobial agents.

Anti-Bacterial Agents↗
PubMed1994

Evaluation of Etest for rapid susceptibility testing of Mycobacterium chelonae and M. fortuitum.

Etest is a new concept for MIC determinations for antimicrobial agents that is based on a predefined antibiotic gradient on a plastic strip calibrated with a continuous logarithmic MIC scale covering 15 twofold dilutions. Etest was compared with a reference agar dilution method for susceptibility testing of clinical isolates of Mycobacterium chelonae and M. fortuitum. Results read after 3 days showed good agreement between MICs obtained with Etest and those obtained with the reference method within +/- 2 dilutions for 90% of all test combinations. All but one of the strains were inhibited by low concentrations of ciprofloxacin or amikacin. Susceptibility to clarithromycin, erythromycin, imipenem, rifampin, doxycycline, and fusidic acid was variable, and all strains were resistant to ceftazidime and trimethoprim. The results suggest that Etest is well suited for studies of drug resistance in rapidly growing mycobacteria.

Amikacin↗
PubMed1992

Evaluation of the E-Test for susceptibility testing of pneumococci.

The E-Test (AB Biodisk, Sweden) is an antibiotic gradient strip that is applied to an inoculated agar plate and results in an elliptical zone of inhibition that intercepts the graded strip, producing a quantitative (microgram per milliliter) result. Pneumococci (100) were used in this study, 38 penicillin-susceptible [minimal inhibitory concentrations (MICs), less than or equal to 0.12 micrograms/ml], 42 intermediately resistant (MICs, 0.12-1.0 micrograms/ml), and 20 resistant (MICs, greater than 1 microgram/ml). E-Test strips were evaluated on Mueller-Hinton agar plates with 5% sheep blood. Agar dilution MICs were determined by the National Committee for Clinical Laboratory Standards (NCCLS) method. Penicillin MICs for the E-Test tended to be slightly lower (one log2 dilution) than reference MICs due to the continuous scale from which E-Test MICs were read. All but two penicillin-susceptible isolates were correctly categorized by the E-Test method. Of the 62 penicillin-resistant strains, 59 had E-Test MICs of greater than or equal to 0.12 micrograms/ml, with 88% of these strains having E-Test MICs within one doubling dilution of the reference MICs. However, using the current NCCLS breakpoint MICs, many of the penicillin-resistant strains with reference MICs of 2 micrograms/ml were categorized as intermediate by the E-Test, with MICs of 0.38-1 microgram/ml. For chloramphenicol, erythromycin, and tetracycline, correlation of the two methods was excellent. E-Test chloramphenicol MICs provided clearer separation of susceptible and resistant strains than did the reference method. We conclude that the E-Test is a reliable method for determination of MICs of the antibiotics evaluated for pneumococci.

Chloramphenicol↗
PubMed1992

The E-Test as an epidemiologic tool.

A comparison was made of the discriminating power of the E-Test and conventional methods to distinguish different bacterial strains harboring plasmid-mediated extended-spectrum beta-lactamases. The E-Test provided quantitative data comparable to those of a broad range of concentrations in the agar dilution method, but proved to be far superior to the disk diffusion test or the broth microdilution semiautomatic PASCO system for the detection and hence for the epidemiologic surveillance of this type of resistant strain.

Bacteria↗