Mutant Prevention Concentrations of Imipenem and Meropenem againstPseudomonas aeruginosaandAcinetobacter baumannii

The aim of this study was to determine the usefulness of the MPC of carbapenems against clinical isolates ofPseudomonasspp.andAcinetobacterspp. and to assess its possible relationship with mechanisms of resistance. Detection of the mechanisms of resistance was performed using Antibiotic Susceptibility Testing, Double Disk Synergy, disk antagonism, addition of NaCl to the medium, addition of PBA or EDTA to Carbapenem disks, addition of PBA to Cefoxitin disks, and CCCP test for 10Pseudomonasspp. andAcinetobacter baumanniistrains. The MIC and MPC were determined using the broth macrodilution and plate dilution methods, respectively. FourAcinetobacter baumanniistrains produced MBL. Two of them produced Oxacillinase and one produced ESBL. TwoPseudomonasspp. isolates produced both KPC and MBL. The resistantAcinetobacterspp. andPseudomonasspp. strains had higher MPC values than susceptible ones. However, the Mutant Selection Window was found to be dependent on the degree of resistance but not on a particular mechanism of resistance. The usefulness of the MPC was found to be dependent on its value. Based on our data, we recommend determining the MPC for each isolate before using it during treatment. Furthermore, the use of T>MSW instead of T>MIC is suggested.

Download Full-text

Mutations in the fks1 Gene in Candida albicans, C. tropicalis, and C. krusei Correlate with Elevated Caspofungin MICs Uncovered in AM3 Medium Using the Method of the European Committee on Antibiotic Susceptibility Testing

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00088-08 ◽

2008 ◽

Vol 52 (9) ◽

pp. 3092-3098 ◽

Cited By ~ 85

Author(s):

Marie Desnos-Ollivier ◽

Stéphane Bretagne ◽

Dorothée Raoux ◽

Damien Hoinard ◽

Françoise Dromer ◽

...

Keyword(s):

Candida Albicans ◽

Antibiotic Susceptibility ◽

Susceptibility Testing ◽

Antifungal Susceptibility ◽

Clinical Isolates ◽

Antibiotic Susceptibility Testing ◽

Wild Type ◽

European Committee ◽

Rpmi Medium

ABSTRACT Mutations in two specific regions of the Fks1 subunit of 1,3-β-d-glucan synthase are known to confer decreased caspofungin susceptibility on Candida spp. Clinical isolates of Candida spp. (404 Candida albicans, 62 C. tropicalis, and 21 C. krusei isolates) sent to the French National Reference Center were prospectively screened for susceptibility to caspofungin in vitro by the broth microdilution reference method of the Antifungal Susceptibility Testing Subcommittee of the European Committee on Antibiotic Susceptibility Testing (AFST-EUCAST). Twenty-eight isolates (25 C. albicans, 2 C. tropicalis, and 1 C. krusei isolate) for which the caspofungin MIC was above the MIC that inhibited 90% of the isolates of the corresponding species (MIC90) were subjected to molecular analysis in order to identify mutations in the fks1 gene. Substitutions in the deduced protein sequence of Fks1 were found for 8 isolates, and 20 isolates had the wild-type sequence. Among the six C. albicans isolates harboring mutations, six patterns were observed involving amino acid changes at positions 641, 645, 649, and 1358. For C. tropicalis, one isolate showed an L644W mutation, and for one C. krusei isolate, two mutations, L658W and L701M, were found. Two media, RPMI medium and AM3, were tested for their abilities to distinguish between isolates with wild-type Fks1 and those with mutant Fks1. In RPMI medium, caspofungin MICs ranged from 0.25 to 2 μg/ml for wild-type isolates and from 1 to 8 μg/ml for mutant isolates. A sharper difference was observed in AM3: all wild-type isolates were inhibited by 0.25 μg/ml of caspofungin, while caspofungin MICs for all mutant isolates were ≥0.5 μg/ml. These data demonstrate that clinical isolates of C. albicans, C. tropicalis, and C. krusei with decreased susceptibility to caspofungin in vitro have diverse mutations in the fks1 gene and that AM3 is potentially a better medium than RPMI for distinguishing between mutant and wild-type isolates using the AFST-EUCAST method.

Download Full-text

Antibiotic Susceptibility Testing (Agar Disk Diffusion and Agar Dilution) of Clinical Isolates of Enterococcus faecalis and E. faecium: Comparison of Mueller-Hinton, Iso-Sensitest, and Wilkins-Chalgren Agar Media

Chemotherapy ◽

10.1159/000007118 ◽

1998 ◽

Vol 44 (4) ◽

pp. 217-229 ◽

Cited By ~ 9

Author(s):

Walter H. Traub ◽

Udo Geipel ◽

Birgit Leonhard

Keyword(s):

Enterococcus Faecalis ◽

Antibiotic Susceptibility ◽

Susceptibility Testing ◽

Clinical Isolates ◽

Disk Diffusion ◽

Antibiotic Susceptibility Testing ◽

Mueller Hinton ◽

Agar Dilution ◽

Agar Media

Download Full-text

Prevalence of constitutive and inducible clindamycin resistance among clinical isolates of Staphylococcus aureus in a tertiary care institute in North India

International Journal of Research in Medical Sciences ◽

10.18203/2320-6012.ijrms20172999 ◽

2017 ◽

Vol 5 (7) ◽

pp. 3120

Author(s):

Jeevan Shetty ◽

Zarrin Afroz

Keyword(s):

Staphylococcus Aureus ◽

Antibiotic Susceptibility ◽

Susceptibility Testing ◽

Tertiary Care ◽

Clinical Isolates ◽

Diffusion Method ◽

Clinical Samples ◽

Antibiotic Susceptibility Testing ◽

Sensitivity Testing ◽

Inducible Clindamycin Resistance

Background: Clindamycin is an important drug used in the treatment of Methicillin Sensitive Staphylococcus aureus (MSSA) as well as in Methicillin-resistant Staphylococcus aureus (MRSA) infections. This drug is widely used in the treatment of skin and soft tissue infections caused by them. Therapeutic failure caused by macrolide-lincosamine-streptogramin B constitutive and inducible clindamycin resistance (MLSBc and MLSBi) is being more commonly reported.Methods: The present study was conducted over a period of six months from October 2016 to March 2017 to know the incidence of MLSBc and MLSBi in Staphylococcus aureus (S. aureus) isolates obtained in our hospital by D-test as per CLSI guidelines. A total of 130 isolates of S.aureus were obtained from different clinical specimens which included pus/ wound swab (n=266), urine (n=577), sputum (n=225), blood (n=221), throat swab (n=71), ear/eye discharge (n=21), high vaginal swab (n=20) and body fluids (n=50). All the isolates were subjected to antibiotic sensitivity testing by Kirby Bauer’s disc diffusion method. Amoxyclav, Erythromycin, Clindamycin, Co-trimoxazole, Tetracycline, Ofloxacin, Gentamicin, Linezolid and Vancomycin were the antibiotics used.Results: Out of 130 (8.9%) isolates of S. aureus obtained from 1451 clinical samples, 82 (63.1%) were found to be MSSA and 48 (36.9%) were MRSA. Among S. aureus, 43 (33.1%) isolates showed MLSBc resistance, 22 (16.9%) isolates showed MLSBi resistance and 20 (15.4%) isolates showed MS phenotype. The remaining 45 (34.6%) isolates remained sensitive to Erythromycin. Among MSSA, MLSBc were observed in 18 (22%) isolates and MLSBi in 9 (11%) while in MRSA, MLSBc were observed in 25 (52.1%) isolates and MLSBi in 13 (27.1%) isolates. Almost all clinical isolates showed 100% sensitivity to Vancomycin and Linezolid in routine antibiotic susceptibility testing. Both MLSBc and MLSBi resistance was significantly higher (p<0.05) in MRSA than in MSSA.Conclusions: The study emphasizes the importance of conducting D test along with routine antibiotic susceptibility testing for better utilization of clindamycin in S. aureus infections.

Download Full-text