Comparison of MICE and Etest with CLSI Agar Dilution for Antimicrobial Susceptibility Testing against Oxacillin-Resistant Staphylococcus spp.

Objective: the main objective of this study was to comparatively evaluate the performance of M. I. C. E. and Etest methodologies to that of agar dilution for determining the antimicrobial susceptibility profile of oxacillin-resistant Staphylococcus spp.Methods: A total of 100 oxacillin-resistant Staphylococcus spp. isolates were collected from hospitalized patients at a teaching hospital. Antimicrobial susceptibility testing for vancomycin, teicoplanin and linezolid was performed using the reference CLSI agar dilution method (2009), Etest and M. I. C. E. methodologies. the MIC values were interpreted according to CLSI susceptibility breakpoints and compared by regression analysis.Results: in general, the essential agreement (+/- 1-log(2)) between M. I. C. E. and CLSI agar dilution was 93.0%, 84.0% and 77.0% for linezolid, teicoplanin and vancomycin, respectively. Essential agreement rates between M. I. C. E. and Etest were excellent (>90.0%) for all antibiotics tested. Both strips (M. I. C. E. and Etest) yielded two very major errors for linezolid. Unacceptable minor rates were observed for teicoplanin against CoNS and for vancomycin against S. aureus.Conclusions: According to our results, linezolid and teicoplanin MICs against all staphylococci and S. aureus, respectively, were more accurately predicted by M. I. C. E. strips. However, the Etest showed better performance than M. I. C. E. for predicting vancomycin MICs against all staphylococci. Thus, microbiologists must be aware of the different performance of commercially available gradient strips against staphylococci.Thermo Fisher Scientific, São Paulo, BrazilConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Universidade Federal de São Paulo, Lab Alerta, Disciplina Infectol, São Paulo, BrazilUniversidade Federal de São Paulo, Hosp São Paulo, Lab Cent, São Paulo, BrazilUniversidade Federal de São Paulo, Lab Alerta, Disciplina Infectol, São Paulo, BrazilUniversidade Federal de São Paulo, Hosp São Paulo, Lab Cent, São Paulo, BrazilCNPq: 307816/2009-5Web of Scienc

Co-transmission of Rahnella aquatilis between hospitalized patients

ABSTRACT Rahnella aquatilis is an environmental Gram-negative bacillus that is rarely reported as human pathogen, being mainly associated with infections in immunocompromised patients. Herein we describe two cases ofR. aquatilis isolates recovered from endotracheal aspirate cultures of different patients in a tertiary hospital located in the city of São Paulo, Brazil. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and 16S rDNA gene sequencing were performed to confirm bacterial identification after the isolates being erroneously identified as Pantoea spp. by automated system. Both isolates showed the same PFGE pattern and presented the ß-lactamase encoding geneblaRAHN-1, responsible for resistance to cephalothin. The isolates were susceptible to broad-spectrum cephalosporins, carbapenems, fluoroquinolones, aminoglycosides, and polymyxin B. This report shows the presence and transmission of uncommon bacteria in the nosocomial environment and alerts us about the need for new tools of correct microbiologic diagnosis

Nocardial scleritis: A case report and a suggested algorithm for disease management based on a literature review

Purpose: To report a case of nocardial scleritis and to propose a logical treatment algorithm based on a literature review. Observations: It is important to suspect a nocardial infection when evaluating anterior unilateral scleritis accompanied by multiple purulent or necrotic abscesses, especially in male patients with a history of chronic ocular pain and redness, trauma inflicted by organic materials, or recent ophthalmic surgery. A microbiological investigation is essential. In positive cases, a direct smear reveals weakly acid-fast organisms or Gram-positive, thin, beading and branching filaments. Also, the organism (usually) grows on blood agar and Lowenstein–Jensen plates. An infection can generally be fully resolved by debridement of necrotic areas and application of topical amikacin drops accompanied by systemic sulfamethoxazole–trimethoprim. Conclusions and significance: Together with the case report described, we review data on a total of 43 eyes with nocardial scleritis. Our proposed algorithm may afford a useful understanding of this sight-threatening disease, facilitating easier and faster diagnosis and management. Keywords: Nocardia, Microbiology, Infection, Scleral disease, Necrotizin

Avaliação das metodologias M.I.C.E.®, Etest® e microdiluição em caldo para determinação da CIM em isolados clínicos Evaluation of M.I.C.E.TM, Etest® and CLSI broth microdilution methods for antimicrobial susceptibility testing of nosocomial bacterial isolates

INTRODUÇÃO: As fitas Oxoid® M.I.C.Evaluator® (M.I.C.E., Thermo Fisher Scientific, Basingstoke, UK), recém-lançadas no mercado brasileiro, representam uma alternativa rápida para a realização de testes de sensibilidade a antimicrobianos (TSA). OBJETIVO: Avaliar o desempenho da metodologia M.I.C.E. em relação à microdiluição em caldo (teste de referência) e ao Etest® (BioMérieux, Marcy l'Étoile, France). Material e métodos: Foram selecionados 160 isolados bacterianos, sendo P. aeruginosa (20), Acinetobacter spp. (20), K. pneumoniae (20), E. coli (20), S. aureus (20), Staphylococcus coagulase-negativa (20), E. faecalis (20) e E. faecium (20). Os TSAs foram realizados por microdiluição em caldo, Etest e M.I.C.E., seguindo-se as recomendações do Clinical Laboratory Standards Institute (CLSI, 2009) e dos respectivos fabricantes. Os resultados foram interpretados segundo os critérios estabelecidos pelo CLSI e comparados por análise de regressão. RESULTADOS: Avaliando-se todas as combinações de antimicrobianos vs. a espécie bacteriana, o desempenho da metodologia M.I.C.E. foi muito bom, apresentando uma concordância geral (variação na concentração inibitória mínima [CIM] ± 1-log2) > 90%, exceto para cefotaxima (85%) e vancomicina (76,3%), quando em comparação com os resultados da metodologia de referência. Quando comparado com o Etest, a metodologia M.I.C.E. apresentou concordância geral > 96%, com exceção para a combinação amoxicilina/ácido clavulânico (67,5%). CONCLUSÃO: Os resultados do TSA obtidos pela metodologia M.I.C.E. apresentaram boa correlação com aqueles obtidos pela microdiluição em caldo e pelo Etest, indicando que essa metodologia é uma alternativa rápida para a determinação da CIM pelos laboratórios de microbiologia clínica. Atenção especial deve ser dada á determinação da CIM para a combinação amoxicilina/ácido clavulânico.<br>INTRODUCTION: The Oxoid® M.I.C.EvaluatorTM methodology (M.I.C.E., Thermo Fisher Scientific, Basingstoke, UK), recently released into the market, represents a rapid alternative to antimicrobial susceptibility testing. OBJECTIVE: The objective of this study was to evaluate the performance of M.I.C.E. methodology in relation to broth microdilution (reference test) and Etest® (BioMérieux, Marcy l'Étoile, France). Material and method: A total of 160 bacterial isolates were collected comprising the following species: P. aeruginosa (20), Acinetobacter spp. (20), K. pneumoniae (20), E. coli (20), S. aureus (20), coagulase-negative Staphylococcus (20), E. faecalis (20) and E. faecium (20). Following Clinical Laboratory Standands Institute (CLSI) standards (2009) and the manufacturers' recommendations, antimicrobial susceptibility testing was performed using broth microdilution method, Etest and M.I.C.E. The results were interpreted according to the criteria established by CLSI and compared through regression analysis. RESULTS: All antimicrobial combinations vs. bacterial species were evaluated and M.I.C.E. methodology yielded good results with general correlation (MIC variation ± 1-log2) > 90%, except for cefotaxime (85%) and vancomycin (76.3%) when compared with the reference method. The M.I.C.E. results compared to Etest showed general correlation (> 96%), except for amoxicillin/clavulanic acid (67.5%) combination. CONCLUSION: AST results obtained from M.I.C.E. methodology showed a good correlation with those from broth microdilution and Etest, which corroborates its time effectiveness in the determination of MIC. However, the combination of amoxicillin/clavulanic acid requires further attention