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Background:Among the enteric pathogens, diarrheagenic Escherichia coli are important causes of diarrhea in children in both developing and industrialized countries. Some Lactobacillus species are commonly used as probiotics, with effects especially against acute diarrhea in childhood.Objectives:The aim of this study was to explore antimicrobial activity of Lactobacillus strains isolated from fecal flora of healthy breast-fed infants against five diarrheagenic E. coli pathotypes such as enteroaggregative E. coli (EAEC), enterohaemorrhagic E. coli (EHEC) enteroinvasive E. coli (EIEC), enteropathogenic E. coli (EPEC) and enterotoxigenic E. coli (ETEC).Materials and Methods:Fecal samples were collected from seven healthy breast-fed infants between 1 to 18 months of age in Tehran city, Iran. Identification of Lactobacillus isolates was performed by biochemical and 16S rRNA gene sequencing methods. An agar well diffusion assay was used for detection of antimicrobial activity of Lactobacillus isolates against five diarrheagenic E. coli pathotypes.Results:A total of 20 Lactobacillus isolates were identified from stool samples. Lactobacillus fermentum was the most frequently isolated strain, followed by L. plantarum and L. rhamnosus. Seven Lactobacillus strains including L. fermentum (four isolates), L. paracasei (one isolate), L. plantarum (one isolate) and L. rhamnosus (one isolate) had a mild inhibitory activity against diarrheagenic E. coli. The mechanism of inhibitory activity of Lactobacillus strains appeared to be due to the production of organic acids or hydrogen peroxide.Conclusions:Our findings show that Lactobacillus strains with human origin had a mild inhibitory activity against the diarrheagenic E. coli, and these strains may be useful as probiotic candidates in prevention of intestinal infections caused by diarrheagenic E. coli.

Staphylococcus aureus is one of the most common causes of seafood-borne diseases worldwide, which are attributable to the contamination of food by preformed enterotoxins. In this study, a total of 206 (34.3%) Staphylococcus aureus strains were obtained from 600 fish and shrimp samples and were tested for their antimicrobial susceptibility. We assessed the prevalence of the genes responsible for the staphylococcal enterotoxins (SEA, SEB) and toxic shock syndrome toxin 1 (TSST-1) genes. The results indicated that 34% of aqua food samples were contaminated with S. aureus, and 23.8% of these isolates were mec-A-positive. Sixty-four percent of the strains isolated from contaminated seafood was enterotoxigenic S. aureus, and 28.2% of SEs were MRSA-positive. The most prevalent genotype was characterized by the presence of the sea gene (45.2%), followed by the seb gene (18.5%), and the tst gene encoding TSST-1 was found in eight strains (3.9%). Of the 206 S. aureus isolates, 189 strains (84.9%) were resistant to at least one antibiotic. Given the frequent outbreaks of enterotoxigenic MRSA, it is necessary to make revisions to mandatory programmes to facilitate improved hygiene practices during fishing, aquaculture, processing, and sales to prevent the contamination of fishery products in Iran.

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Nosocomial infection constitutes a major public health problem worldwide. Increasing antibiotic resistance of pathogens associated with nosocomial infections has also become a major therapeutic challenge for physicians. Thus, development of alternative treatment protocols, such as the use of probiotics, matters. The aim of this research was to determine the antagonistic properties of Lactobacillus plantarum and Lb. fermentum isolated from the faeces of healthy infants against nonfermentative bacteria causing nosocomial infections. One hundred five samples of nosocomial infections were collected and processed for bacterial isolation and antimicrobial susceptibility testing following standard bacteriologic techniques. The antibiotic susceptibility test was performed by the disk diffusion method, and antagonistic effect of Lactobacillus strains was investigated by well diffusion method. Of 105 samples, a total of 29 bacterial strains were identified as nonfermentative bacteria, including 17 Acinetobacter baumannii and 12 Pseudomonas aeruginosa. A. baumannii showed high resistance to tested antibiotics except ampicillin/sulbactam, and P. aeruginosa showed resistance to ampicillin/sulbactam and gentamicin and sensitive to amikacin and meropenem. Lb. plantarum had antagonistic properties against both A. baumannii and P. aeruginosa strains. Lb. plantarum had considerable effects on preventing the growth of A. baumannii and P. aeruginosa strains. However, further research is needed to better understanding of these effects on P. aeruginosa.

Probiotics beneficially affect human health by improving the balance of intestinal microbiota and mucosal defence against pathogens. Many probiotic bacteria, mostly belong to the genera Lactobacillus, are used in commercial probiotic fermented milks throughout the world. The aim of this study was to investigate the probiotic potential of lactic acid bacteria (LAB) isolated from various Iranian traditional yogurts. During an 18-month study from October 2013 to May 2014, 96 samples were equally collected from traditional yogurts produced from goat, sheep and cow milk in Yazd Providence, Iran. Samples were transferred into MRS broth for enrichment and then subcultured on MRS agar. Isolates were studied for morphological and biochemical characteristics, using Gram staining and catalase test. The ability to tolerate acidic pH and resistance to bile salts were used as restrictive criteria for probiotic potential. Selected LAB were further identified using 16S rDNA sequence analysis. Of 96 yogurt samples, 47 LAB were isolated; from which 12 were candidates for probiotics. Six probiotic isolates belonged to Pediococcus acidilacticii and other six isolates to Lactobacillus plantarum, L. brevis, L. fermentum and L. kefiri. In summary, LAB strains isolated from Iranian traditional yogurts were considered as viable candidates of probiotics, based on their properties such as acid and bile tolerance.

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