MALDI-TOF mass spectrometry identification of yeast-form fungi: a comparison between methods

Introduction: Identification of yeast species has clinical and epidemiological value. Different methods can be used, such as chromogenic media, microculture on corn meal agar with Tween 80, as well as conventional biochemical and automated methods. Recently, proteomic studies employing matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry have been a major advance in diagnosis due to speed of execution and accuracy of results. Methods: For this study, 79 yeast samples were submitted to identification using chromogenic medium, microculture on corn meal-Tween 80 agar, VITEK 2 Compact identification, and MALDI-TOF mass spectrometry. Results: Most of the 79 samples were identified, with differences in the performance of the methods used. Colonial morphology and microscopy were compatible with the genus Candida. MALDI-TOF mass spectrometry had the best performance, with 78 strains identified (98.7%), compared to VITEK 2 Compact (92.4%) and microculture on corn meal agar (70.9%). Conclusions: MALDI-TOF mass spectrometry using the VITEK MS instrument performed best and has proven to be a revolutionary method in clinical microbiology laboratories. Regarding the identification of C. albicans and C. tropicalis, the chromogenic medium had excellent performance, thus being a good option to optimize the process. (AU)

Antagonistic activity expressed by Shigella sonnei: identification of a putative new bacteriocin

Bacteriocins are antibacterial, proteinaceous substances that mediate microbial dynamics. Bacteriocin production is a highly disseminated property among all major lineages of bacteria, including Shigella. In this paper, we addressed the purification and characterisation of a bacteriocin produced by a Shigella sonnei strain (SS9) isolated from a child with acute diarrhoea. The substance was purified through ammonium-sulphate precipitation and sequential steps of chromatography. The intracellular fraction obtained at 75% ammonium sulphate maintained activity following exposure to pH values from 1-11 and storage at -80ºC for more than two years and was inactivated by high temperatures and proteases. The molecular mass of the purified bacteriocin was determined by mass spectrometry to be 18.56 kDa. The N-terminal sequence of the bacteriocin did not match any other antibacterial proteins described. A putative new bacteriocin produced by S. sonnei has been detected. This bacteriocin may represent a newly described protein or a previously described protein with a newly detected function. Considering that SS9 expresses antagonism against other diarrhoeagenic bacteria, the bacteriocin may contribute to S. sonnei virulence and is potentially applicable to either preventing or controlling diarrhoeal disease.

Acute diarrhea associated with Salmonella enterica in Belo Horizonte-MG: prevalence and characterization of isolates / Diarreia aguda associada a Salmonella enterica em Belo Horizonte-MG: prevalência e caracterização das amostras isoladas

Introduction: Acute infectious diarrhea is still regarded as a public health problem associated with a wide range of etiologic agents, from which Salmonella enterica is particularly worth mentioning inasmuch as it is a major cause of inflammatory diarrhea in both developed and developing countries. Objective: To assess the distribution of S. enterica among children with acute diarrhea in Belo Horizonte and to characterize bacterium isolates. Material and methods: The study group comprised a total of 157 children from low socioeconomic background. Stool samples were collected for leukocyte analysis and Salmonella bacterial culture. The isolates were serotyped and evaluated as to antimicrobial susceptibility profile, extended-spectrum â-lactamases (ESBL) production, and presence of virulence markers (invA, iroB, and spvC). RESULTS: A total of 5/3.2% children were infected by S. enterica, 3/60% by S. enterica Typhimurium, 1/20% by S. enterica Enteritidis and 1/20% S. enterica subsp. enterica serotype 8.20:z4,z23:-. Fecal leucocytes were detected in two out of five fecal specimens positive for S. enterica. Isolates from three children were resistant to nalidixic acid, nalidixic acid + chloramphenicol, and nalidixic acid + chloramphenicol + ampicillin. ESBL production was not detected. All samples presented invA and iroB genes. spvC marker was observed in isolates from two children infected by S. Typhimurium and S. Enteritidis. Conclusion: The results demonstrate that S. enterica infection is uncommon among children from our region. Furthermore, they indicate the need for periodic monitoring of bacterial antimicrobial susceptibility profile in order to establish suitable antimicrobial therapy when required.

INTRODUÇÃO: A diarreia infecciosa aguda é considerada um problema de saúde pública associado a uma ampla gama de agentes etiológicos, entre os quais destaca-se Salmonella enterica, causa importante de diarreia inflamatória em países desenvolvidos e em desenvolvimento. OBJETIVOS: Avaliar a distribuição de S. enterica em crianças com diarreia aguda em Belo Horizonte e caracterizar as amostras isoladas. MATERIAL E MÉTODO: O grupo de estudo consistiu de 157 crianças de nível socioeconômico baixo. Espécimes fecais foram empregados para pesquisa de leucóc itos e cultivo de Salmonella. As amostras isoladas foram sorotipadas e submetidas à avaliação do perfil de suscetibilidade a antimicrobianos, da produção de betalactamases de amplo espectro (ESBL) e da presença de marcadores de virulência (invA, iroB e spvC). RESULTADOS: Cinco/3,2% crianças apresentaram-se infectadas por S. enterica; três/60%, por S. enterica Typhimurium; uma/20%, por S. enterica Enteritidis; e uma/20%, por S. enterica subsp. enterica sorotipo 8,20:z4,z23:-. Leucócitos fecais foram detectados em dois dos cinco espécimes positivos para S. enterica. As amostras isoladas de três crianças apresentaram resistência a ácido nalidíxico, ácido nalidíxico + cloranfenicol e ácido nalidíxico + cloranfenicol + ampicilina. Nenhuma amostra produziu ESBL. Todas as amostras albergavam os genes invA e iroB. O marcador spvC foi observado em amostras isoladas de duas crianças infectadas por S. Typhimurium e S. Enteritidis. CONCLUSÃO: Os resultados demonstram que diarreia associada a S. enterica é raramente observada entre crianças da nossa região e indicam a necessidade de avaliação periódica do perfil de suscetibilidade a antimicrobianos da bactéria para orientar o estabelecimento de antibioticoterapia, quando indicada.

Shigella in Brazilian children with acute diarrhoea: prevalence, antimicrobial resistance and virulence genes

Diarrhoeal disease is still considered a major cause of morbidity and mortality among children. Among diarrhoeagenic agents, Shigella should be highlighted due to its prevalence and the severity of the associated disease. Here, we assessed Shigella prevalence, drug susceptibility and virulence factors. Faeces from 157 children with diarrhoea who sought treatment at the Children's Hospital João Paulo II, a reference children´s hospital in Belo Horizonte, state of Minas Gerais, Brazil, were cultured and drug susceptibility of the Shigella isolates was determined by the disk diffusion technique. Shigella virulence markers were identified by polymerase chain reaction. The bacterium was recovered from 10.8% of the children (88.2% Shigella sonnei). The ipaH, iuc, sen and ial genes were detected in strains isolated from all shigellosis patients; set1A was only detected in Shigella flexneri. Additionally, patients were infected by Shigella strains of different ial, sat, sen and set1A genotypes. Compared to previous studies, we observed a marked shift in the distribution of species from S. flexneri to S. sonnei and high rates of trimethoprim/sulfamethoxazole resistance.