Resumo Devido à extensa aplicação de antibióticos como promotores de crescimento na alimentação animal, a resistência aos antimicrobianos aumentou. Para superar esse desafio, os microbiologistas do rúmen buscam novos probióticos para melhorar a produtividade do gado. O presente estudo teve como objetivo isolar e avaliar bactérias lácticas específicas de raças (BAL) como potenciais probióticos animais. 12 cepas foram isoladas de diferentes amostras, incluindo leite, rúmen e fezes de búfalos Nilli Ravi. Esses isolados foram avaliados quanto ao seu potencial antimicrobiano contra patógenos animais comuns (Bacillus spp., E. coli, Staphylococcus aureus, Salmonella spp., Listeria spp.). Todos os isolados foram identificados por meio do sequenciamento do gene 16S rRNA e as análises filogenéticas inferiram que essas cepas apresentaram estreita relação com as espécies de vários gêneros; Enterococcus lactis, Pediococcus pentosaceus, Bacillus subtilis, Weissella cibaria, Weissella soli, Bacillus tequilensis, Weissella bombi, Bacillus licheniformis, Lactococcus lactis, Bacillus megaterium, Lactobacillus ruminis e Lactococcus lactis. O perfil probiótico dos isolados foi obtido usando critérios padrão, particularmente com propriedades probióticas animais.

Abstract Due to extensive application of antibiotics as growth promoters in animal feed, antimicrobial resistance has been increased. To overcome this challenge, rumen microbiologists search for new probiotics to improve the rate of livestock production. The present study was aimed to isolate and evaluate breed-specific lactic acid bacteria (LAB) as potential animal probiotics. The current study was conducted during 10 months from July 2020 to April 2021, in which a total of n=12 strains were isolated from different samples including milk, rumen, and feces of Nilli Ravi Buffaloes. These isolates were evaluated for their antimicrobial potential against common animal pathogens (Bacillus spp., E. coli, Staphylococcus aureus, Salmonella spp., Listeria spp.). All the isolates were identified using 16S rRNA gene sequencing and the phylogenetic analyses inferred that these strains showed close relations to the species of various genera; Enterococcus lactis, Pediococcus pentosaceus, Bacillus subtilis Weissella cibaria, Weissella soli, Bacillus tequilensis, Weissella bombi, Bacillus licheniformis, Lactococcus lactis, Bacillus megaterium, Lactobacillus ruminis, and Lactococcus lactis. NMCC-Ru2 has exhibited the enormous potential of antimicrobial activity, 28 mm, for Salmonella typhimurium;23 mm for Listeria monocytogenes 21 mm for E.coil. Highest resistance was seen in NMCC-Ru2 agasint test antbiotic, like 25.5 mm for Tetracycline. Overall results revesl that the probiotic profile of isolates was achieved using standard criteria, particularly with animal probiotic properties

Resumo 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.

Abstract 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.