Süt ve Peynirden İzole Edilen Bacillus cereus’un Prevalansı, Enterokoksin Üretimi ve Antibiyotik Direnci

Abstract

Bacillus cereus is a type of bacteria that can cause severe food poisoning. The aim of this study was to determine the incidence of B. cereus in various full-fat milk and cheese samples and to assess the HBL (haemolysin BL) and NHE (nonhaemolytic enterotoxin) production and the resistance to several antimicrobial agents of the isolates. A total of 259 samples of full-fat milk (raw, pasteurized and UHT) and cheese obtained from different retail markets in Bursa province between July and December 2013 were analysed. Isolation of B. cereus was performed using Bacara agar according to the method suggested by FDA. Twenty six (10.04%) out of 259 samples were found to be contaminated with presumptive B. cereus based on their colony morphology and microscopic appearance, by counts that ranged from 1x10 1 to 1.1x10 3 CFU/mL in raw and pasteurized milk and from 4x10 1 to 3.8x10 5 CFU/g in cheese. Thirteen isolates of B. cereus were identified by API system. However, further analysis using MALDI-TOF-MS confirmed 19 isolates as B. cereus. Thirteen out of 19 (68.4%) isolates showed evidence of only NHE toxin production while six out of 19 (31.6%) isolates were positive for both NHE and HBL production. All isolates were resistant to penicillin G, although they were susceptible to oleondamycin, erythromycin and streptomycin. There were seven different patterns of multiple antibiotic resistance in this study. In our study, 84.2% (n = 16) of B. cereus isolates exhibited multiple antibiotic resistance. Keywords: Bacillus cereus, Milk, Cheese, Enterotoxin, Multiple antibiotic resistance Süt ve Peynirden İzole Edilen Bacillus cereus'un Prevalansı, Enterokoksin Üretimi ve Antibiyotik Direnci ÖzetBacillus cereus ciddi gıda zehirlenmesine neden olabilen bir bakteri türüdür. Bu çalışmanın amacı, çeşitli süt ve peynir örneklerinde B. cereus insidansını belirlemek ve elde edilen izolatların HBL (hemolizin BL) ve NHE (nonhemolitik enterotoksin) üretimini ve çeşitli antimikrobiyal ajanlara direncini belirlemektir. Temmuz -Aralık 2013 tarihleri arasında Bursa ilinde farklı satış yerlerinden toplam 259 adet tam yağlı süt (çiğ, pastörize ve UHT) ve peynir örneği analiz edilmiştir. B.cereus izolasyonu FDA tarafından önerilen metoda göre Bacara agar kullanılarak yapıldı. Analize alınan çiğ ve pastörize süt örneklerinde 1x10 1 ile 1.1x10 3 kob/mL ve peynirde 4x10 1 ile 3.8x10 5 kob/g arasında değişen sayılarda olmak üzere, toplamda 259 örneğin 26 adetinin (%10.04) koloni morfolojileri ve mikroskobik görünüşlerine de dayalı olarak B. cereus ile kontamine olduğu tespit edilmiştir. Örneklerden elde edilen 13 adet B. cereus izolatı API sistemi ile identifiye edilmiştir. Bununla birlikte, MALDI-TOF-MS kullanılarak yapılan analizde, 19 adet izolat B. cereus olarak identifiye edilmiştir. Bu 19 izolatın 13'ünün (%68.4) sadece NHE toksini bakımından, altı izolatın da (%31.6) NHE ve HBL toksinleri bakımından pozitif olduğu gözlenmiştir. Tüm izolatlar oleondamisin, eritromisin ve streptomisine duyarlı olmalarına rağmen penisilin G'ye dirençlidir. B...

Identification and Pathogenic Potential of Bacillus cereus Strains Isolated from a Dairy Processing Plant Producing PDO Taleggio Cheese

“…The isolates obtained from the analyzed Taleggio production plant showed a constant ability to produce PC-PLC, proteases, and hemolysins, whereas only most of them were able produce HBL (66.7%). These results agree with previous studies showing a very high rate of PC-PLC, protease, and hemolysin activity [4,[31][32][33], and a variable rate of HBL production (ranging from 20 to 90%) by B. cereus isolates [21,34,35].…”

“…Considering cheese, several studies confirm the high prevalence of nhe genes in B. cereus isolates [21,31,32,[35][36][37][38]. In this study, we found that all the strain clusters harbored nheA, and some also nheB (83.3%) and nheC (66.7%), indicating that 66.7% of the strains are potentially able to secrete active NHE.…”

Toxigenic Genes, Pathogenic Potential and Antimicrobial Resistance of Bacillus cereus Group Isolated from Ice Cream and Characterized by Whole Genome Sequencing

“…Various studies reported different rates of B. cereus s.l. contamination: in dried food samples of different pulses and cereals 56% [ 34 ]; in pasteurized milk 27% to 47% [ 30 , 35 , 36 , 37 ]; in milk and dairy products 14% to 70% [ 38 , 39 , 40 , 41 ]; in ice cream 30% to 63% [ 6 , 31 , 38 , 41 ]. Our study investigated the presence of the B. cereus group in ice creams, which was estimated to be 65% (33/51); a similar prevalence (62.7%) was described in Messelhausser U. et al, 2010 [ 6 ].…”

Evaluation of microbial quality and safety of selected dairy products with special focus on toxigenic genes of Bacillus cereus

“…Our findings were almost like those of Zhao et al (2020), who concluded that 94.4 % of B. cereus harboured nhe gene, while cytK gene was present in a higher percent (75.9 %) than our findings. Yibar et al (2017) recorded that 42.3 % of B. cereus isolates from the examined different cheeses types harboured nhe gene. There was a significant difference (p<0.05) between nhe and ces genes in all investigated samples except in flavoured drinking yogurt, which indicates a high association of these genes with these products.…”