The effect of selected Lactobacillus strains on dextran sulfate sodium-induced mouse colitis model.

Inflammatory bowel disease (IBD) comprises two major illnesses: Crohn's disease (CD) and ulcerative colitis (UC). Dextran sulfate sodium (DSS) mouse colitis model has been used in understanding the mechanism of IBD. This study was conducted to examine selected Lactobacillus spp. as potential IBD treatment in the DSS-induced animal model. Balb/c mice were used and colitis was induced by adding 5% dextran sodium sulfate into the drinking water for 8 days. Colon length, disease activity index (DAI) and histological analysis were measured as markers of inflammation in DSS colitis mice. The majority of the Lactobacillus species significantly prevented the shortening of the colon length compared with the DSS group. The DAI scores of mice were significantly reduced following usage of four Lactobacillus strains included: Lactobacillus plantarum 03 and 06, Lactobacillus brevis 02 and Lactobacillus rhamnosus 01. The histological analysis exhibited that oral administration of Lactobacillus strains had therapeutic effects on mice colitis. L. plantarum and L. brevis showed better therapeutic effect against DSS-induced acute colitis mice. The probiotic activities of these three isolates indicated that the probiotic effects were strain specific and none of these useful bacteria could exhibit all of the valued probiotic properties simultaneously.

The diversity of class B and class D carbapenemases in clinical Acinetobacter baumannii isolates.

Wide distrubution of multidrug-resistant Acinetobacter baumannii strains has become a foremost concern in hospital environments. Treatment of infections caused by multidrug resistant strains has conventionally involved the use of ß-lactams such as carbapenems. In this study, we report the distribution of carbapenemase genes in A. baumannii isolated from hospitalized patients. The study was conducted on 110 non-repetitive A. baumannii isolates collected from hospitalized patients, over a nine-month period. Clinical isolates were examined by conventional susceptibility testing, using the disk-diffusion method and multiplex polymerase chain reaction to detect acquired carbapenemase genes. All of the isolates were completely resistant to TOB, SXT, IPM, MEM, CTX, CRO, FEP, CAZ, CIP, PTZ, PIP and were susceptible to colistin, but moderately susceptible TET (2.72%), AK (4.54%) and GEN (3.63%). The prevalence of bla-OXA-51like, bla-OXA-23like, bla-OXA-24like, bla-OXA-58like, blaSIM and blaSPM genes was 100%, 96.36%, 35.45%, 7.27%, 7.27% and 3.63%, respectively. bla-GIM and bla-VIM genes were not detected among the strains. Our results suggest that OXA-type carbapenemase genes plus class B ß-lactamases contribute to carbapenem resistance in the collected isolates. Therefore, quick identification of these resistant genes using molecular approaches is critical in limiting the spread of infections caused by A. baumannii. Drug administration correction of the physicians, based on antibiotic susceptibility testing and more knowledge on the nosocomial infection control policies as essential need.

Characterization of bacteriocin production in Lactobacillus spp. isolated from mother's milk.

The purpose of the present study was to isolate Lactobacillus bacteria from mother's milk and to assess their probiotic potential. Sixty breast milk samples were collected from the volunteered mothers aged from 19 to 35 and from rural areas of Lorestan and Markazi Provinces, Iran. At first, 970 bacill-shaped bacterial colonies were isolated from these samples and stored in proper condition. Two hundred isolates were randomly selected and investigated for their ability to tolerate acidic condition and to tolerate bile salt as well. Only 33 isolates could withstand the exposure to low pH and bile salt. The isolates were identified using PCR primer specific to Lactobacillus and it was demonstrated that eighteen of thirty-three isolates were belonged to the Lactobacillus. Among the isolates, 16 and 2 of them were Lactobacillus reuteri and L. gasseri, respectively. In addition, the antibiotic resistance of the isolates was determined using disc diffusion method and all of the isolates were shown to be sensitive to eight out of the twelve investigated antibiotics. Moreover, the antagonistic effect of the isolates was inspected on ten indicator pathogens. Interestingly, all of the pathogenic bacteria were inhibited by Lactobacillus isolates. In addition, to partially understand the nature of inhibition mechanism, well diffusion deployed for two randomly-selected indicator bacteria and the resulting halos of three isolates were statistically significant compared to other lactobacillus (p < 0.05). Subsequently, bacteriocin genes (plnS, Laf, gasA) were identified by PCR among the isolates. The results showed that only 2 isolates possessed the gasA gene which were in accordance with well diffusion test. Consequently, eighteen Lactobacillus isolated from breast milk samples which all of them were able to tolerate low pH and bile salt. Similarly, all of the Lactobacillus isolates were proved to inhibit the growth of pathogen strains and two of them possess a bacteriocin-related gene.

Isolates of Lactobacillus plantarum and L. reuteri display greater antiproliferative and antipathogenic activity than other Lactobacillus isolates.

PURPOSE: Lactic acid bacteria (LAB) have been associated with many beneficial effects in human digestive physiology. The aim of this study was to evaluate such effect, including attachment, antiproliferation and anti-pathogenic/antibacterial/antimicrobial properties of LAB isolated from healthy humans. METHODOLOGY: Thirteen isolates, obtained from fecal samples of healthy individuals, were identified by phenotypic and molecular methods. Human colon adenocarcinoma cell line HT-29 and the cell proliferation kit II (XTT) assay were used for examination of the Lactobacillus adherence and antiproliferative activity, respectively. In addition, the inhibitory effect of Lactobacillus isolates against pathogenic bacteria was examined. RESULTS: Out of 13 Lactobacillus isolates, 5 (38 %) isolates were non-adhesive, 4 (31 %) were adhesive and 4 (31 %) were strongly adhesive. Amongst the isolated lactobacilli, L. reuteri showed the highest degree of inhibitory effect against the attachment of the enteropathogens. The XTT assay showed that 3 different isolates had the strongest antiproliferative activity with the maximum effect observed by L. plantarum isolates. CONCLUSION: Our results described that different Lactobacillus species isolated from normal fecal samples had different degrees of antiproliferative and anti-pathogenic/antibacterial/antimicrobial activities. However, no isolates showed all of the examined properties concurrently, suggestive that a combination of Lactobacillus species is needed for an active biological defense system.

Determination of Bacteriocin Genes and Antibacterial Activity of Lactobacillus Strains Isolated from Fecal of Healthy Individuals.

Lactobacillus species play a major role in gastrointestinal (GI) tract function, intestinal microbiota balance, and the immune system activity by exerting a strong activity against many intestinal pathogens. The aim of this study was to isolate Lactobacillus species from fecal samples, investigate their antimicrobial properties, and characterize their bacteriocin encoding genes. 48 fecal samples were grown in MRS broth and then MRS agar. The colonies grown in MRS agar were selected and identified by PCR. 72 Lactobacillus species were obtained from 434 lactic acid bacteria (LAB) strains. Approximately 40% of all Lactobacillus isolates had antimicrobial activity against one or more microorganisms and 17.4% of them were active against all four indicator bacteria. The frequency of bacteriocin encoding genes were 5 (6.9%), 3 (4.1%) and 5 (6.9%) for Gassericin A, Plantaricin S and Laf operon, respectively. pH alteration had no effect on antibacterial activity, but in the alkaline range these activities were reduced and the strains showed the highest antibacterial activity after 48 h incubation. These data indicate that the majority of isolates were susceptible to GI tract or belonged to other bacterial forms such as viable but nonculturable (VBNC). The detection of bacteriocin encoding genes in about only 6% of all Lactobacillus isolates seems to be due to the existence of many other bacteriocin encoding genes in Lactobacillus species which were not tested. Further study of the bacteriocin gene clusters, types, subtypes and the probiotic effect of these strains will contribute to a better characterization of these isolates.

Bifidobacterium obtained from mother's milk and their infant stool; A comparative genotyping and antibacterial analysis.

Antibacterial activity of Bifidobacterium species has been considered as an important probiotic property for development of human gut immunity. This study was conducted to assess the genotypes and antibacterial activities of the native Bifidobacterium isolates obtained from the human's breast milk and the feces of their paired infants. Fifty-six samples from twenty-eight mothers' milk and paired infants feces were collected and cultured. Suspicious colonies were picked up and confirmed by phenotypic and molecular identifications. Randomly amplified polymorphic DNA (RAPD-PCR) and antibacterial activity were carried out. Amongst 56 samples, 41 different Bifidobacterium species including 12 B. breve, 14 B. longum, and 15 B. bifidum were isolated. Out of which, 12 isolates including B. longum (6), B. breve (4) and B. bifidum (2) were shared between six mother-infant pairs. Only three strains of B. longum showed 100% similarity in their RAPD-PCR. No significant difference was observed in the antibacterial activity of the Bifidobacterium isolates, with the same or different RAPD-PCR profile, against the enteric bacteria. Overall, 29% of the Bifidobacteria species isolated from the mothers milk and their paired infants feces were shared. All species of Bifidobacteria showed the universal role of antipathogens activities irrespective of the host and the isolation site.

Clonal Diversity in Multi Drug Resistant (MDR) Enterococci Isolated from Fecal Normal Flora.

Enterococci are Gram positive and catalase- negative cocci that are found in the gastrointestinal tract of mammals and birds, and are readily isolated from soil, surface and waters. The aim of this study was to discriminate between Enterococcus isolates based on repetitive element sequence based -PCR (Rep-PCR) with the BOXA2R primer and their antibiotics profile. Enterococci isolates were obtained from 180 fecal samples. The isolates were identified by biochemical reaction and specific identification was confirmed by PCR with species specific primers. All isolates were subjected to Rep typing and antimicrobial susceptibility tests. Rep-PCR analysis of 180 isolates revealed 93 REP types with forty-five single types (ST1 to ST45) and forty-eight common types (CT1 to 48). Antibiotic susceptibility tests exhibited that 53 (29.4%), 43 (23.8%), 11 (6.1%) and 9 (5%) were resistant to erythromycin, tetracycline, gentamicin and ciprofloxacin respectively but among the isolates, sixteen were multi drug resistant (MDR). These MDR isolates showed 11 Rep types with seven single types and four common types. In addition, 81.2% of MDR isolates were from male subjects and the average age of these persons was more than fifty years. This study showed that 56.2% of MDR isolates were homogeneous with 95 % similarity, and high rate of resistance to tetracycline and erythromycin (81.2%) were observed in these isolates. The concern about these normal flora isolates are the pathogenic potential of these bacteria through the horizontal transfer of antibiotic resistance and virulence genes.