ABSTRACT
In this study, lactic acid bacteria (LAB) strains were isolated from ground beef, and it was analyzed if they have any effect on the growth of two reference bacteria (Salmonella sp. and Escherichia coli). It was found that five isolates showed an inhibitory effect in both reference bacteria by spot at the lawn assay. These bacteria were selected to perform growth kinetics in co-culture to determine if they modify the growth parameters of the reference bacteria. Subsequently, LAB cultures and three treatments (crude extract, thermally treated and thermally treated with neutral pH) of cells free supernatants (CFS) were screened by the agar well diffusion assay. In co-culture, selected LAB altered the growth rate and reduce the maximum population of both reference bacteria. While, LAB cultures and CFS also showed antimicrobial activity, and there was no significant difference among CFS treatments. LAB isolated from ground beef showed an antimicrobial effect against the reference bacteria that could be used for meat biopreservation purposes.
Subject(s)
Antibiosis , Food Preservation/methods , Lactobacillus delbrueckii/physiology , Lactococcus lactis/physiology , Leuconostoc mesenteroides/physiology , Limosilactobacillus fermentum/physiology , Meat/analysis , Animals , Cattle , Colony Count, Microbial , Escherichia coli/growth & development , Escherichia coli/isolation & purification , Escherichia coli/pathogenicity , Food Microbiology/methods , Humans , Hydrogen-Ion Concentration , Lactobacillus delbrueckii/isolation & purification , Limosilactobacillus fermentum/isolation & purification , Lactococcus lactis/isolation & purification , Leuconostoc mesenteroides/isolation & purification , Salmonella/growth & development , Salmonella/isolation & purification , Salmonella/pathogenicityABSTRACT
Lactic Acid Bacteria ï¼LABï¼ are generally recognized as safe. It has been used to increase the shelf-life of fermented products, and its antimicrobial action is based on the metabolites secretions, such as lactic acid, hydrogen peroxide, reuterin, bacteriocins and the like-bacteriocins substances. It has been proven that LAB are able to inhibit deteriorating bacteria of raw meat, but improper handling of live cultures could lead to spoilage. So, the use of their bacteriocins, small antimicrobial peptides, could be an alternative. Besides reducing the number of spoilage bacteria, it seeks to inhibit pathogenic bacteria such as Salmonella, enterohemorrhagic Escherichia coli and Listeria. The food industry uses few bacteriocins and now bacterial resistance has been reported. For that reason, the search of novel bacteriocins produced by LAB is a priority. Moreover, the natural microbiota of meat could be a reservoir of LAB.
Subject(s)
Food Microbiology , Food Storage/methods , Lactobacillales/physiology , Meat/microbiology , Animals , Bacteriocins/metabolism , Bacteriocins/pharmacology , Bacteriocins/toxicity , Drug Resistance, Microbial , Food Contamination/prevention & control , Food Preservation/methods , Food Preservatives/metabolism , Food Preservatives/pharmacology , Food Preservatives/toxicity , Food Safety/methods , Humans , Meat Products/microbiology , Microbiota/physiology , Red Meat/microbiologyABSTRACT
This is the first report about anthelmintic resistance (AR) in hair sheep farms determined in a sub-humid tropical climate, in an area known as Huasteca Potosina, Mexico. Faecal egg count reduction tests (FECRT) and egg hatch in vitro tests were conducted to identify the level of AR against benzimidazole (BZ) in parasitic gastrointestinal nematode (GIN) populations. An allele-specific polymerase chain reaction (AS-PCR) was performed to obtain a 250â¯bp band, indicating resistance, and a 550â¯bp band, indicating susceptibility to BZ. Macrocyclic lactones (ML) and imidazothiazole (IMZ) drugs were also tested with the FECRT. A PROBIT analysis was conducted using SAS to determine the 50% lethal doses (LD50) of the drugs according to the egg hatch in vitro test. Resistance to BZ and ML was found on all farms (0-70% effectiveness), whereas the susceptibility of nematodes to IMZ was detected with the FECRT (93-100% effectiveness). The LD50 was higher than the discriminating dose (0.1⯵gâ¯ml-1) for BZ and confirmed AR to this anthelmintic; we also confirmed a high AR frequency with AS-PCR. Therefore, we suggest that strategic deworming should be performed to avoid the development of resistance to imidazothiazole.
