Prevalence, serotyping and antimicrobials resistance mechanism of Salmonella enterica isolated from clinical and environmental samples in Saudi Arabia

Abstract Salmonella is recognized as a common foodborne pathogen, causing major health problems in Saudi Arabia. Herein, we report epidemiology, antimicrobial susceptibility and the genetic basis of resistance among S. enterica strains isolated in Saudi Arabia. Isolation of Salmonella spp. from clinical and environmental samples resulted in isolation of 33 strains identified as S. enterica based on their biochemical characteristics and 16S-rDNA sequences. S. enterica serovar Enteritidis showed highest prevalence (39.4%), followed by S. Paratyphi (21.2%), S. Typhimurium (15.2%), S. Typhi and S. Arizona (12.1%), respectively. Most isolates were resistant to 1st and 2nd generation cephalosporin; and aminoglycosides. Moreover, several S. enterica isolates exhibited resistance to the first-line antibiotics used for Salmonellosis treatment including ampicillin, trimethoprim-sulfamethoxazole and chloramphenicol. In addition, the results revealed the emergence of two S. enterica isolates showing resistance to third-generation cephalosporin. Analysis of resistance determinants in S. enterica strains (n = 33) revealed that the resistance to β-lactam antibiotics, trimethoprim-sulfamethoxazole, chloramphenicol, and tetracycline, was attributed to the presence of carb-like, dfrA1, floR, tetA gene, respectively. On the other hand, fluoroquinolone resistance was related to the presence of mutations in gyrA and parC genes. These findings improve the information about foodborne Salmonella in Saudi Arabia, alarming the emergence of multi-drug resistant S. enterica strains, and provide useful data about the resistance mechanisms.

Alkaline protease from a new halotolerant alkaliphilic Bacillus agaradhaerens strain ak-r isolated from egyptian soda lakes / Protease alcalina de uma nova estirpe ak-r halotolerante e alcalófila de Bacillus agaradhaerens isolada a partir dos lagos alcalinos egípcios

Alkaline proteases are hydrolytic enzymes that cleave peptide bonds in proteins and peptides in alkaline conditions, which occupy a pivotal importance with respect to their industrial applications. This study aimed to isolate new alkaline protease producing alkaliphilic bacteria from Egyptian soda lakes and optimize the fermentation process to enhance the enzyme production. The extensive screening process of the samples collected from Egyptian soda lakes resulted in isolation of a potent alkaline protease producing alkaliphilic strain AK-R. The isolate was identified as Bacillus agaradhaerens strain AK-R based on 16S rRNA gene analysis (99%). Wheat bran and gelatin supported maximum alkaline protease production as carbon and nitrogen sources, respectively. Strain AK-R is halo-tolerant thermotolerant alkaliphilic bacterium in nature, as it can grow over a wide range of NaCl concentrations (up to 25%) and up to 55 °C, with maximal growth and enzyme production at 2.5-5%, and pH 11 at 35 °C. Among the tested cations, only Mg2+ and Ca2+ ions significantly enhanced the enzyme production by about 1.2, and 1.3 fold compared to control, respectively. Alkaline protease secretion was coherent with the growth pattern, reaching maximal yield after about 32 h (mid stationary phase). In conclusion a new halo-tolerant thermo-tolerant alkaliphilic alkaline protease producing Bacillus agaradhaerens strain AK-R was isolated from Egyptian soda lakes. Optimization of the nutritional and cultivation conditions resulted in increase of enzyme yield by 20 fold. Strain AK-R and its extracellular alkaline protease with salt, pH and temperature, tolerance signify their potential application in laundry and pharmaceuticals industries.

Proteases alcalinas são enzimas hidrolíticas que quebram ligações peptídicas em proteínas e peptídeos em condições alcalinas, o que ocupa uma importância fundamental em relação às suas aplicações industriais. Este estudo teve como objetivo isolar novas proteases alcalinas e produzir bactérias alcalófilas a partir dos lagos salgados alcalinos egípcios e otimizar o processo de fermentação para aumentar a produção de enzimas. O extensivo processo de triagem das amostras coletadas dos lagos salgados alcalinos egípcios resultou no isolamento de uma protease alcalina potente produzindo uma estirpe alcalófila AK-R. O isolado foi identificado como sendo a estirpe AK-R de Bacillus agaradhaerens baseado na análise de genes 16S rRNA (99%). O farelo de trigo e a gelatina suportaram a produção máxima de protease alcalina como fontes de carbono e nitrogênio, respectivamente. A estirpe AK-R é uma bactéria alcalófila halotolerante e termotolerante, pois pode crescer dentro de uma vasta gama de concentrações de NaCl (até 25%) e até 55ºC, com crescimento e produção de enzimas máximos a 2.5-5% e pH 11 a 35ºC. Dentre os cátions testados, somente os íons Mg2+ e Ca2+ aumentaram significativamente a produção de enzimas em cerca de 1.2 e 1.3 em comparação ao controle, respectivamente. A secreção de protease alcalina foi coerente com o padrão de crescimento, atingindo o rendimento máximo após 32h (fase estacionária média). Pode-se concluir que uma nova estirpe AK-R de Bacillus agaradhaerens halotolerante, termotolerante e alcalófila produtora de protease alcalina foi isolada a partir dos lagos salgados alcalinos egípcios. A otimização das condições de nutrição e cultivo resultou num aumento da produção de enzima em 20 vezes. A estirpe AK-R e a sua protease alcalina extracelular com tolerância ao sal, pH e temperatura tornam significantes as suas potenciais aplicações nas indústrias farmacêutica e de lavanderia.