Cronobacter spp. in foods of plant origin: occurrence, contamination routes, and pathogenic potential.

Cronobacter is an emerging bacterial pathogen associated with infections such as necrotizing enterocolitis, sepsis, and meningitis in neonates and infants, related to the consumption of powdered infant formula. In addition, this bacterium can also cause infections in adults by the ingestion of other foods. Thus, this review article aims to report the occurrence and prevalence of Cronobacter spp. in foods of plant origin, as well as the possible sources and routes of contamination in these products, and the presence of pathogenic strains in these foods. Cronobacter was present in a wide variety of cereal-based foods, vegetables, herbs, spices, ready-to-eat foods, and foods from other categories. This pathogen was also found in cultivation environments, such as soils, compost, animal feces, rice and vegetable crops, as well as food processing industries, and domestic environments, thus demonstrating possible contamination routes. Furthermore, sequence types (ST) involved in clinical cases and isolates resistant to antibiotics were found in Cronobacter strains isolated from food of plant origin. The identification of Cronobacter spp. in plant-based foods is of great importance to better elucidate the vehicles and routes of contamination in the primary production chain and processing facility, until the final consumption of the food, to prevent infections.

The effect of sodium chloride and temperature on the levels of transcriptional expression of staphylococcal enterotoxin genes in Staphylococcus aureus isolates from broiler carcasses.

Staphylococcus aureus is one of the most common pathogens associated with food poisoning, which is caused by the ingestion of food contaminated with staphylococcal enterotoxins (SE). Our study aims at evaluating the occurrence and expression of five SE genes (sea, seb, sec, sed, and see) in S. aureus previously isolated from broiler carcasses. Besides that, it also presents an in vitro analysis of the effects of sodium chloride and temperature on the levels of transcriptional expression. A total of 30 S. aureus isolates were investigated for the presence of SEs by PCR assay. The expression level and the effects of sodium chloride (2.5% NaCl), as well as temperature (8 ºC and 12 ºC), on the transcriptional expression, were evaluated by a quantitative reverse transcription PCR (RT-qPCR). Twelve isolates carried at least one of the SE genes. Among them, five representative isolates presented transcriptional expression for at least one gene. Both sodium chloride and low temperatures interfered with the expression of the SE genes, decreasing their values. However, one isolate displayed relative expression 2.25 times higher for sed gene than S. aureus FRI 361 in optimal conditions (p < 0.05), demonstrating their toxigenic potential even under salt stress. There was no evidence of enterotoxin gene expression at 8 ºC.

Expression levels of the agr locus and prfA gene during biofilm formation by Listeria monocytogenes on stainless steel and polystyrene during 8 to 48 h of incubation 10 to 37 °C.

The objective of this study was to compare the gene expression levels of the agr locus and prfA gene during adhesion and biofilm formation by four L. monocytogenes isolates (2 biofilm-forming and 2 non-forming) on stainless steel and polystyrene surfaces at different temperatures (10 °C, 20 °C and 37 °C), and times (8 h, 12 h, 24 h and 48 h). The agrA and prfA genes were expressed at higher levels than the agrBCD genes. The levels of agr locus expression were higher in the biofilm-forming strains, and the greatest difference between biofilm-forming and non-forming isolates was observed for the agrB, agrC and agrD genes. However, no difference in the expression of the prfA gene was seen among the isolates, independent of the biofilm-forming ability. Maximum expression of the agr locus and prfA gene was observed at 37 °C, whereas expression was lowest at 10 °C. The agr locus, and particularly the agrB, agrC and agrD genes, is important in the initial adhesion phase of biofilm production by L. monocytogenes, with this expression independent of prfA. In addition, the agr locus and prfA gene expression levels were strongly influenced by time and temperature.

Prevalence and expression of staphylococcal enterotoxin genes in Staphylococcus aureus isolated from food poisoning outbreaks.

Staphylococcus aureus is an important pathogen of foodborne origin. The pathogen produces a variety of toxins that include the staphylococcal enterotoxins (SE). The present study aimed to evaluate the prevalence and expression of 5 SE genes (sea, seb, sec, sed, and see) in S. aureus isolated from outbreaks occurred in the state of Rio Grande do Sul, Brazil. All isolates, with the exception of 2, presented the same or higher transcriptional expression than the reference strains for at least 1 of these genes. The presence of SE genes combined with high levels of transcriptional expression suggests that 1 or more SEs were involved with the staphylococcal food poisoning outbreak analyzed in the present study.

EStafilococos coagulase positiva em queijos minas frescal e minas padrão comercializadosem Pelotas, Rio Grande do Sul / Coagulase positive staphylococcus In minas frescal and minas padrão cheese commercialized in Pelotas, Rio Grande do Sul (Brazil)

O objetivo deste estudo foi avaliar a presença de Estafi lococos coagulase positiva (ECP) em amostras de queijos industrializados Minas Frescal e Minas Padrão, comercializados na cidade dePelotas, Rio Grande do Sul. Foram avaliadas vinte e oito (28) amostras de queijo minas frescal e quarenta e quatro (44) de queijo minas padrão, coletadas no comércio local. Quatro amostrasapresentaram contaminação acima do padrão estabelecido pela RDC 12, de 12 de janeiro de 2001 (ANVISA), sendo três de queijo minas frescal e uma de queijo minas padrão. A presença de ECPé preocupante uma vez que esses micro-organismos podem se multiplicar, produzir e secretar toxinas em níveis sufi cientes para causar intoxicação alimentar estafi locócica, enfermidade transmitida por alimentos de grande importância em saúde pública.

Detecção de genes do cluster egc em Staphylococcus aureus isolados de alimentos de origem animal / Detection of genes of egc cluster in Staphylococcus aureus isolated from foods of animal origin

Os objetivos deste estudo foram detectar, por PCR, genes codificadores de enterotoxinas estafilocócicas, pertencentes ao cluster egc (genes seg, sei, selm, seln e selo) em Staphylococcus aureus isolados em diferentes alimentos de origem animal, e relacionar sua presença com a fonte de isolamento. Quarenta e uma cepas de S. aureus de diferentes origens (carne de frango, leite cru, embutidos cárneos e queijo) foram avaliadas por PCR, por meio da amplificação de um fragmento de 3375pb (denominado egc parcial), que foi utilizado como marcador da presença do cluster, e fragmentos de cada um dos genes pertencentes ao cluster egc. Há presença de genes do cluster egc em isolados de S. aureus isoladas em alimentos de origem animal; entretanto, diferentes genótipos puderam ser observados em função da fonte de isolamento. A ocorrência de S. aureus isolados em carne de frango que possuíam todos os genes do cluster foi elevada; no entanto, nos isolados oriundos dos demais alimentos, essa ocorrência foi reduzida.

The aim of this study was to detect, through PCR usage, the genes which encodes staphylococcal enterotoxins and which belongs to egc cluster (seg, sei, selm, seln and selo) in S. aureus isolated from different foods of animal origin and correlate their presence with the strain origin. Forty-one strains of S. aureus from different sources (chicken meat, raw milk, sausage meat and cheese) were evaluated through PCR by amplifying a fragment of 3375bp (called partial egc), which was used as a marker for the presence of cluster, and fragments of individual genes belonging to egc cluster. There is presence of the egc cluster in strains of S. aureus isolated from foods of animal origin, however, different genotypes could be observed depending on the isolation source. The occurrence of strains isolated from chicken meat that had all the genes of the cluster was high; however, in the strains isolated from the other foods, such occurrence has been reduced.