Anti-bacterial activity of essential oils against multidrug-resistant foodborne pathogens isolated from raw milk / Atividade antibacteriana de óleos essenciais contra patógenos alimentares multirresistentes isolados de leite cru

The presence of pathogenic bacteria in food is considered as a primary cause of food-borne illness and food quality deterioration worldwide. The present study aimed to determine the effectiveness of five essential oils (EOs) against multidrug-resistant foodborne pathogens. In the current study Gram-negative bacteria (Escherichia, Enterobacter, Citrobacter, Proteus, Pseudomonas, and Klebsiella) and the Gram-positive bacteria Staphylococcus were isolated from raw milk and biochemically characterized. The anti-bacterial effect of different antibiotics and EOs (thyme, oregano, lemongrass, mint, and rosemary) was determined using the standard disc diffusion method. The antibiogram study revealed that Gram-negative bacteria were highly resistant to penicillin while Staphylococcus was resistant to streptomycin, amoxicillin, and lincomycin. Moderate resistance was observed to doxycycline, amikacin, enrofloxacin, kanamycin and cefixime. Isolates were found less resistant to gentamycin, chloramphenicol, and ciprofloxacin. EOs showed a broad range of antimicrobial activity against all bacteria except P. aeruginosa. Of these, thyme was more effective against most of the multi-drug resistant bacterial strains and formed the largest zone of inhibition (26 mm) against Escherichia followed by oregano oil (18 mm) against Staphylococcus (p<0.05). Klebsiella spp and Citrobacter spp showed resistance to mint and lemongrass oil respectively. The EOs such as lemongrass, mint and rosemary were less active against all the bacteria. The findings of the recent study suggest the use of EOs as natural antibacterial agents for food preservation.

A presença de bactérias patogênicas em alimentos é considerada a principal causa de doenças transmitidas por alimentos e deterioração da qualidade dos alimentos em todo o mundo. O presente estudo teve como objetivo determinar a eficácia de cinco óleos essenciais (OEs) contra patógenos de origem alimentar multirresistentes. No presente estudo, bactérias Gram-negativas (Escherichia, Enterobacter, Citrobacter, Proteus, Pseudomonas e Klebsiella) e as bactérias Gram-positivas Staphylococcus foram isoladas do leite cru e caracterizadas bioquimicamente. O efeito antibacteriano de diferentes antibióticos e OEs (tomilho, orégano, capim-limão, hortelã e alecrim) foi determinado usando o método padrão de difusão em disco. O estudo do antibiograma revelou que as bactérias Gram-negativas eram altamente resistentes à penicilina, enquanto o Staphylococcus era resistente à estreptomicina, amoxicilina e lincomicina. Foi observada resistência moderada à doxiciclina, amicacina, enrofloxacina, canamicina e cefixima. Os isolados foram encontrados menos resistentes à gentamicina, cloranfenicol e ciprofloxacina. Os OEs mostraram uma ampla gama de atividade antimicrobiana contra todas as bactérias, exceto P. aeruginosa. Destes, o tomilho foi mais eficaz contra a maioria das cepas bacterianas multirresistentes e formou a maior zona de inibição (26 mm) contra Escherichia seguido de óleo de orégano (18 mm) contra Staphylococcus (p<0,05). Klebsiella spp e Citrobacter spp apresentaram resistência ao óleo de menta e capim-limão, respectivamente. Os OEs como capim-limão, hortelã e alecrim foram menos ativos contra todas as bactérias. Os resultados do estudo recente sugerem o uso de OEs como agentes antibacterianos naturais para conservação de alimentos.

Anti-bacterial activity of essential oils against multidrug-resistant foodborne pathogens isolated from raw milk.

The presence of pathogenic bacteria in food is considered as a primary cause of food-borne illness and food quality deterioration worldwide. The present study aimed to determine the effectiveness of five essential oils (EOs) against multidrug-resistant foodborne pathogens. In the current study Gram-negative bacteria (Escherichia, Enterobacter, Citrobacter, Proteus, Pseudomonas, and Klebsiella) and the Gram-positive bacteria Staphylococcus were isolated from raw milk and biochemically characterized. The anti-bacterial effect of different antibiotics and EOs (thyme, oregano, lemongrass, mint, and rosemary) was determined using the standard disc diffusion method. The antibiogram study revealed that Gram-negative bacteria were highly resistant to penicillin while Staphylococcus was resistant to streptomycin, amoxicillin, and lincomycin. Moderate resistance was observed to doxycycline, amikacin, enrofloxacin, kanamycin and cefixime. Isolates were found less resistant to gentamycin, chloramphenicol, and ciprofloxacin. EOs showed a broad range of antimicrobial activity against all bacteria except P. aeruginosa. Of these, thyme was more effective against most of the multi-drug resistant bacterial strains and formed the largest zone of inhibition (26 mm) against Escherichia followed by oregano oil (18 mm) against Staphylococcus (p<0.05). Klebsiella spp and Citrobacter spp showed resistance to mint and lemongrass oil respectively. The EOs such as lemongrass, mint and rosemary were less active against all the bacteria. The findings of the recent study suggest the use of EOs as natural antibacterial agents for food preservation.

Isolation, diversity, and biotechnological potential of rhizo- and endophytic bacteria associated with mangrove plants from Saudi Arabia.

Marine bacteria have been exceptional sources of halotolerant enzymes since decades. The aim of the present study was to isolate bacteria producing hydrolytic enzymes from seven different mangroves collected from the coastal area of Thuwal, Jeddah, Saudi Arabia, and to further screen them for other enzymatic and antifungal activities. We have isolated 46 different rhizo- and endophytic bacteria from the soil, roots, and leaves of the mangroves using different enzymatic media. These bacterial strains were capable of producing industrially important enzymes (cellulase, protease, lipase, and amylase). The bacteria were screened further for antagonistic activity against fungal pathogens. Finally, these bacterial strains were identified on the basis of the16S rDNA sequence. Taxonomic and phylogenetic analysis revealed 95.9-100% sequence identity to type strains of related species. The dominant phylum was Gammaproteobacteria (γ-Proteobacteria), which comprised 10 different genera - Erwinia, Vibrio, Psychrobacter, Aidingimonas, Marinobacter, Chromohalobacter, Halomonas, Microbulbifer, and Alteromonas. Firmicutes was the second dominant phylum, which contained only the genus Bacillus. Similarly, only Isoptericola belonged to Actinobacteria. Further these enzyme-producing bacteria were tested for the production of other enzymes. Most of the active strains showed cellulytic and lipolytic activities. Several were also active against fungal pathogens. Our results demonstrated that the mangroves represent an important source of potentially active bacteria producing enzymes and antifungal metabolites (bioactive products). These bacteria are a source of novel halophilic enzymes and antibiotics that can find industrial and medicinal use.