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The present study was conducted to evaluate the response of 29 Salmonella isolates to exposure to thermal (60°C for 2 min), acidic (pH 2.9 for 30 min), and alkaline (pH 11 for 60 min) treatments and investigate the susceptibility of the isolates and their biofilms to disinfectants. The reductions of Salmonella isolates populations subjected to each treatment were analyzed according to their isolation source, serotype, antibiotic resistance pattern, and biofilm formation ability. Median reductions for all of Salmonella isolates populations after thermal, acidic, and alkaline treatments were 1.8, 2.1, and 0.7 log CFU/ml, respectively. The isolates behavior under stress conditions were not related to their isolation source, serotype, or biofilm formation ability. The median reduction after alkaline treatment in non-MDR (multidrug- resistant) isolates populations was significantly (p < .05) higher than MDR isolates. The median reduction in biofilms of moderate biofilm producers by disinfectants was significantly (p < .05) higher than that of strong biofilm producers. In conclusion, Salmonella isolates showed the highest susceptibility to acidic treatment and MDR isolates were more resistant to alkaline treatment than non-MDR ones. The current study also revealed that the strong biofilm producer isolates were more resistant to disinfectants than moderate biofilm producers. This study facilitated the understanding of the relationship between Salmonella characteristics (isolation source, serotype, antibiotic resistance pattern, and biofilm formation ability) and its susceptibility to thermal, acidic, and alkaline treatments and disinfectants. The findings are helpful for the prevention and control of Salmonella.

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Avian pathogenic Escherichia coli (APEC) is a major cause of colibacillosis and is associated with economic losses to the poultry production worldwide. Heterophils are the first line of immune defense of the avian host against invasive pathogens. In this study, APEC isolates from chickens with colibacillosis were assigned to phylogenetic groups and immunological activities of heterophils against these groups were examined. A total of 92 APEC isolates was obtained from 106 samples of diverse organs collected from chickens with colibacillosis from different farms in West Azerbaijan province, Iran. Isolates were assigned to phylogenetic groups based on the Clermont triplex PCR method, and immunological activities (including phagocytosis, respiratory burst and bacterial killing) of heterophils against these groups were examined. As results, the frequency of A, B1, B2 and D groups were 35.87, 44.57, 5.43 and 14.13%, respectively. In addition, opsonized Escherichia coli isolates belonging to B1 group significantly enhanced the level of respiratory burst (0.52 ± 0.02%) while the killing level of them was significantly lower than the other groups (29.40 ± 5.09%). There was no significant difference in phagocytic activity of heterophils against the phylogenetic groups. In conclusion, incomplete immune responses to B1 phylogenetic group maybe a principal cause of mortality by colibacillosis caused by this group. It is suggested to study heterophilic immune reaction against E. coli phylogenetic group for development of effective prevention strategy.

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Quorum sensing (QS) is a cell density-dependent mechanism used by many pathogenic bacteria for regulating virulence gene expression. Inhibition or interruption of QS by medicinal plant remedies has been suggested as a new strategy for fighting against antibiotic-resistant bacteria. This study aimed to assess the impact of sub-inhibitory concentrations of licochalcone A (LAA) and epigallocatechin-3-gallate (EGCG) as natural plant products on the QS-associated genes (sdiA and luxS) expression. The PCR test was used to confirm the presence of sdiA and luxS genes in 23 S. Typhimurium isolates from poultry. The quantitative real-time PCR assay was used to analyze the expression of sdiA and luxS in S. Typhimurium isolates in response to the treatment with sub-inhibitory concentrations of LAA and EGCG at 45-min time point. All S. Typhimurium isolates showed the presence of sdiA and luxS genes (100%). As result, the expression of QS-related genes was significantly reduced in S. Typhimurium isolates following treatment with LAA and EGCG. In conclusion, LAA and EGCG showed anti-QS activity with down-regulation of both sdiA and luxS genes in S. Typhimurium, suggesting potential therapeutic use of them against salmonellosis. However, it must be pointed out that the safety and efficiency of these compounds need more thorough research.

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In this study, Salmonella isolates recovered from meat (beef and mutton) and meat contact surfaces at retail were investigated to determine their serotype, antibiotic resistance, and biofilm formation ability. Salmonella was found in 29 (24.17%) samples out of 120 samples including 14/50 (28%) of beef, 10/40 (25%) of mutton, and 5/30 (16.67%) of meat contact surfaces. Seven isolates were identified as S. Enteritidis, three as S. Typhimurium, and two as S. Typhi, while the rest of the isolates were considered as other Salmonella spp. All of the isolates were resistant to at least one antimicrobial agent and 48.27% of them were identified as multidrug-resistant (MDR) Salmonella. All (100%) of meat contact surfaces isolates, 42.8% of beef isolates, and 30% of mutton isolates were found to be MDR Salmonella. Resistance to nalidixic acid (100%), tetracycline (79.3%), and sulphamethoxazole/trimethoprim (44.8%) were observed. The gyrA gene was detected in 19 of 29 isolates, but tetA was found in one isolate. All of the serotypes were able to form biofilm (75.86 % moderate and 24.14 % strong) and S. Enteritidis was the strongest biofilm producer. The findings indicated that the majority of Salmonella isolates in this study were MDR and biofilm producer. Then, safety measures such as cleaning and disinfection must be taken to control Salmonella and promote public health. PRACTICAL APPLICATION: The present study provides useful information on the prevalence of Salmonella serotypes in meat and meat contact surfaces and their antibiotic resistance patterns as well as biofilm formation capacities. Improving hygiene practices in livestock, slaughterhouses, and at retails may reduce the risk of meat contamination to Salmonella. Meanwhile, high levels of antibiotic resistance in Salmonella isolates emphasized on the improper use of antibiotics.

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Staphylococcus aureus is part of the normal flora of animals, and represents one of the leading causes of contagious mastitis in dairy herds worldwide. Sixty-seven epidemiologically unrelated S. aureus isolates from nasal and mastitis milk samples of dairy-producing animals (32 cows, 25 sheep, and 10 goats) were characterized by antimicrobial susceptibility testing and spa typing followed by multilocus sequence typing (MLST) on representative isolates and SCCmec-typing on methicillin-resistant S. aureus (MRSA) isolates. The highest resistance was observed to penicillin (64.2%, 43/67), followed by tetracycline (23.9%, 16/67), erythromycin (22.4%, 15/67), and streptomycin (17.9%, 12/67). In general, 18 spa types (including newly identified t16958) and 13 sequence types (STs) belonging to 8 clonal complexes (CCs) were detected. The cow-associated isolates were mainly assigned to CC5 (n = 18, related to t267-ST97, t521-ST352, t527-ST97, t304-ST6, and t084-ST15), followed by CC398 (n = 6, t937-ST291), CC45 (n = 3, t230-ST45), CC88 (n = 2, t2526-ST88), CC22 (n = 2, t3680-ST22), and CC522 (n = 1, t3576-ST522). Small ruminant isolates were mostly clustered into CC522 (n = 29, related to t3576, t1534, t16958, t7308, t7311, t7305 [ST522], t1534-ST2057, and t5428-ST2079). Two isolates from cows with mastitis were found to be MRSA, exhibited a composite profile of t937-ST291-SCCmecIV. No isolates carried the PVL and mecC genes. A significant difference in clonal types of S. aureus isolates from cows in comparison with those from small ruminants was found. This study demonstrated the circulation of diverse clones of S. aureus among dairy animals in Iran, with a different clonal composition between cows and small ruminants. The current study also reports MRSA-related mastitis in dairy cows, emphasizing the need for comprehensive surveillance.

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Pseudomonas aeruginosa is one of the most common causes of keratitis. The current study was done to evaluate the therapeutic effects of antibacterial combinations with Silver nanoparticles (Ag-NPs) and Ciprofloxacin in experimental Pseudomonas keratitis. Sixty four New Zealand rabbits were prepared. All rabbits were randomly categorized into eight groups (each group containing eight rabbits): Control +, Control -, Ciprofloxacin, Ag-NPs, Ciprofloxacin plus Betamethasone, Ag-NPs plus Betamethasone, Ciprofloxacin plus Ag-NPs, and Ciprofloxacin plus Ag-NPs plus Betamethasone. Twelve hours after bacterial inoculation into the cornea, the eyes were examined daily to evaluate the number of days of ocular discharge and blepharospasm. Also, after 108 and 204 h, first grading of corneal opacity was done and then four rabbits of each groups were euthanized for bacterial count. The results showed that the means of days of blepharospasm, ocular discharge, and bacterial counts (log CFU mL-1) were significantly different in the treatment groups at 108 and 204 h (P <0.0005, ANOVA). According to Tukey's test, Ciprofloxacin plus Ag-NPs plus Betamethasone group was significantly less than Control +, Ag-NPs, and Ag-NPs plus Betamethasone groups for these variables (P < 0.05). The mean rank of opacity scores was significantly different between treatment groups (P = 0.01, Kruskal-Wallis). Mann-Whitney U-test revealed that Ciprofloxacin plus Ag-NPs plus Betamethasone group had significantly better score than Control +, Ag-NPs, and Ag-NPs plus Betamethasone groups (P < 0.05). It seems Ag-NPs can be an appropriate adjuvant for Ciprofloxacin, but due to the results they can't be an alternative for Ciprofloxacin to treat Pseudomonas keratitis.

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BACKGROUND: Staphylococcus aureus is a significant pathogen that can colonize the nares of different animals, causing a wide range of infections in various hosts. OBJECTIVES: We intended to determine the prevalence of S. aureus in the nasal cavity of healthy ruminants and also to investigate the presence of antibiotic resistance genes. MATERIALS AND METHODS: In the present study, healthy cattle (n = 79), sheep (n = 78) and goats (n = 44) were screened for nasal carriage of S. aureus by the Polymerase Chain Reaction (PCR). Staphylococcus aureus isolates were further assessed for the presence of blaZ (encoding penicillin resistance), mecA (encoding methicillin resistance), tetK and tetM (encoding tetracycline resistance), and ermA and ermC (encoding macrolide-lincosamide-streptogramin B resistance) genes. RESULTS: The proportion of S. aureus-positive nasal swabs from cattle, sheep and goats were four (5.06%), 11 (14.1%) and 11 isolates (25%), respectively. The blaZ gene was detected in 20 out of 26 S. aureus isolates (76.9%), including four cattle (100%), nine sheep (81.8%) and seven goats (63.6%). Two of the four cattle isolates possessing the blaZ gene also had the tetK gene. Of the nine sheep isolates harboring the blaZ gene, one possessed the mecA and tetK genes together. Of the seven goat isolates with blaZ gene, one harbored the tetM gene. None of the S. aureus isolates were positive for the ermA and ermC genes. CONCLUSIONS: In contrast to cattle, S. aureus is frequently present in the nose of sheep and goats, which may represent the primary reservoir of S. aureus in small ruminant flocks. This study also showed that nasal isolates of S. aureus from healthy ruminants might be a potential reservoir of antimicrobial-resistance.