Resistencia inducible a clindamicina en Staphylococcus aureus resistentes a meticilina aislados de pacientes pediátricos en Paraguay / Inducible resistance to clindamycin in methicillin-resistant Staphylococcus aureus isolated from Paraguayan children

Resumen Introducción: El método de difusión de doble disco se presenta como una alternativa diagnóstica que permite identificar aislados de Staphylococcus aureus susceptibles a clindamicina, ante el aumento de resistencia a meticilina, reduciendo así la posibilidad de fallo en el tratamiento. Objetivo: Determinar la frecuencia de resistencia a clindamicina inducida por eritromicina en S. aureus resistentes a meticilina (SARM) aislados de niños paraguayos. Materiales y Métodos: Estudio observacional, descriptivo, de corte transversal. Se colectaron 145 aislados S. aureus que causaron infecciones de piel y tejidos blandos y osteo-articulares en pacientes pediátricos del Hospital Central del Instituto de Previsión Social en el período de diciembre-2012 a noviembre-2013. La resistencia a clindamicina se determinó por métodos automatizados y de difusión de doble disco. Se realizó reacción de polimerasa en cadena para genes ermA, ermB, ermC y msrA de aislados representativos. Resultados: La resistencia global a meticilina y clindamicina fue de 67 y 13%, respectivamente (11% atribuible al mecanismo de resistencia a clindamicina inducible). Los genes ermC y msrA fueron detectados individualmente en 25 y 17% de los aislados, respectivamente, mientras que un aislado presentó ambos genes en simultáneo. Discusión: La frecuencia de mecanismo de resistencia inducible a clindamicina señala la importancia de los métodos de difusión de doble disco en la práctica microbiológica, así como se encuentran en los límites de puntos de cortes considerados como aceptables para el uso de este antimicrobiano para infecciones cutáneas y osteo-articulares causadas por SARM.

Background: The double disc diffusion method is an alternative diagnostic that allows the identification of Staphylococcus aureus isolates apparently susceptible to clindamycin but that may develop resistance due to an induction phenomena, mainly asociated to the increase in resistance to methicillin, thus increasing the possibility of failure in the treatment. Aim: To determine the frequency of induced clindamycin resistance in methicillin-resistant S. aureus (MRSA) isolated from Paraguayan children. Materials and Methods: In this cross sectional study, we collected 145 S. aureus isolates that caused skin and soft tissue and osteoarticular infections in pediatric patients of the Central Hospital I.P.S. in the period from December-2012 to November-2013. Resistance to clindamycin was determined by automated methods and double disc diffusion. PCR was performed for ermA, ermB, ermC and msrA genes from representative isolates. Results: The global resistance to methicillin and clindamycin was 67 and 13%, respectively (11% attributable to the inducible mechanism). The ermC and msrA genes were detected individually in 25 and 17% of the isolates respectively while an isolate presented both genes simultaneously. Discussion: The frequency of inducible resistance to clindamycin indicates the importance of double disc diffusion methods in microbiological practice, as well as being within the cut off points considered acceptable for the use of this antibiotic for skin infections. and osteoarticular caused by MRSA.

Establishing Quality Control Ranges for Antimicrobial Susceptibility Testing of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus: A Cornerstone to Develop Reference Strains for Korean Clinical Microbiology Laboratories

Quality control (QC) processes are being performed in the majority of clinical microbiology laboratories to ensure the performance of microbial identification and antimicrobial susceptibility testing by using ATCC strains. To obtain these ATCC strains, some inconveniences are encountered concerning the purchase cost of the strains and the shipping time required. This study was focused on constructing a database of reference strains for QC processes using domestic bacterial strains, concentrating primarily on antimicrobial susceptibility testing. Three strains (Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus) that showed legible results in preliminary testing were selected. The minimal inhibitory concentrations (MICs) and zone diameters (ZDs) of eight antimicrobials for each strain were determined according to the CLSI M23. All resulting MIC and ZD ranges included at least 95% of the data. The ZD QC ranges obtained by using the CLSI method were less than 12 mm, and the MIC QC ranges extended no more than five dilutions. This study is a preliminary attempt to construct a bank of Korean QC strains. With further studies, a positive outcome toward cost and time reduction can be anticipated.

Comparison of cefoxitin disk diffusion test and mecA gene PCR results for methicillin resistance detection in Staphylococcus intermedius group isolates from canine origin in Brazil

The study evaluated cefoxitin disk diffusion tests breakpoints and their correlation to mecA gene PCR results for detecting Methicillin-resistant Staphylococcus intermedius Group (MRSP) isolates from dogs in Brazil. Agreement using proposed breakpoint (resistant < 30 mm) was encouraging. The current study reinforces that an epidemiological breakpoint can be established to predict presence of MRSP.

Resistência a antifúngicos de Candida tropicalis isoladas no Estado do Ceará / Antifungal resistance of Candida tropicalis isolated in the State of Ceará

Neste estudo, foi avaliada a resistência a drogas antifúngicas em 51 cepas de Candida tropicalis isoladas de amostras clínicas no Estado do Ceará, Brasil. Resistência antifúngica foi um evento raro no nosso estudo e foi restrita a 3 (5,9 por cento) das cepas de Candida tropicalis, que exibiram resistência a fluconazol e itraconazol.

In this study, the resistance to antifungal drugs was investigated among 51 strains of Candida tropicalis isolated from clinical samples in the State of Ceará, Brazil. Antifungal resistance was a rare finding in our study and was restricted to three (5.9 percent) of the strains of Candida tropicalis. These exhibited resistance to both fluconazole and itraconazole.

Evaluation of Disk Diffusion Test with Glucose- and Methylene blue-Enriched Mueller-Hinton Agar for Susceptibility Testing of Fluconazole against Candida Isolates / 대한진단검사의학회지

BACKGROUND: Recently, the disk diffusion testing of fluconazole against Candida spp. has been attempted in order to provide a simple inexpensive method in the routine laboratory. We investigated the possibility and reliability of a fluconazole disk diffusion method using a Mueller-Hinton agar supplemented with glucose and methylene blue (GM-MH). METHODS: One hundred and seven isolates of Candida spp. (54 C. albicans, 21 C. glabrata, 20 C. tropicalis, 6 C. parapsilosis, 4 C. krusei, and 2 C. lusitaniae) were tested with the broth microdilution method of National Committee for Clinical Laboratory Standards (NCCLS) document M27-A2 and a disk diffusion test using GM-MH agar. RESULTS: The overall categorical agreement between the NCCLS method and the disk diffusion method was 89.8% for fluconazole, with 0.9% very major errors and 9.3% minor errors; no major errors were detected. CONCLUSIONS: These data suggest that the fluconazole disk diffusion test on GM-MH agar can be used as a routine screening procedure for susceptibility of Candida spp. in the clinical laboratory.

Comparative evaluation of fluconazole susceptibility methods for Candida species: Broth microdilution test, E test and disk diffusion test / 대한임상병리학회지

BACKGROUND: Currently fungal infections have been increasing in clinical aspect. Among them Candida albicans is considered as the most pathogenic. National Committee for Clinical Laboratory Standards(NCCLS) recommends broth macrodilution method for antifungal susceptibility test, but it is difficult to perform. E test is a relatively easy method to perform for the susceptibility testing. So in this study, antifungal susceptibility procedures were compared to determine MIC for fluconazole against 130 Candida strains isolated from clinical specimens. METHOD: The tests including were microdilution method, E test and disk diffusion method. The latter two tests were performed in casitone agar and the former test performed in RPMI 1640 media(Sigma Chemical co. St. Louis, USA). MIC was determined after 24 hrs of incubation. We used Candida albicans ATCC 90018 and Candida parapsilosis ATCC 90028 as controls. A total of 130 strains(93 C. albicans, 29 C. tropicalis, 5 C. parapsilosis and 3 C. glabrata) were tested. RESULTS: The MIC50 and MIC90 of broth microdilution test for C. albicans was > OR =64 microgram/mL equivalently. Agreement of > OR = +/-2 dilution between broth microdilution test and E test was 54 %, and the concordance rate was 55%. The concordance rate between E test and disk diffusion was 90%. CONCLUSIONS: From this study, we conclude that E test can be used as a alternative and convenient method to macrodilution method to determine MIC of fluconazole. But it is necessary for attention to microcolonies surrounding the E test strip. Disk diffusion method is rapid and also can be used as an alternative and convenient method.