Prevalence, resistance patterns, and risk factors for antimicrobial resistance in bacteria from retail chicken meat in Colombia.

As a step toward implementing the Colombian Integrated Program for Antimicrobial Resistance Surveillance (COIPARS), this study aimed to establish the baseline antimicrobial resistance patterns of Salmonella serovars, Escherichia coli, and Enterococcus spp. isolates in retail poultry meat from independent stores and from a main chain distributor center. MICs of the isolates were determined for antimicrobials used both in humans and animals, using an automated system. Salmonella serovars were isolated from 26% of the meat samples and E. coli from 83%, whereas Enterococcus faecalis and Enterococcus faecium were detected in 81 and 13% of the meat samples, respectively. A principal finding of concern in this study was that almost 98% of isolates tested were multidrug resistant. Ceftiofur, enrofloxacin, nalidixic acid, and tetracycline were the antimicrobials that showed the highest frequency of resistance among Salmonella and E. coli isolates. For enterococci, 61.5% of E. faecium isolates were found to be resistant to quinupristin-dalfopristin; this is significant because it is used to treat nosocomial infections when vancomycin resistance is present. Vancomycin resistance was detected in 4% of the E. faecalis isolates. The results of our study highlight the need for rapid implementation of an integrated program for surveillance of antimicrobial resistance by the Colombian authorities in order to monitor trends, raise awareness, and help promote practices to safeguard later generation antimicrobial agents.

Antagonistic effect of Lactobacillus strains against Escherichia coli and Listeria monocytogenes in milk.

The current work studied four types of binary antagonist/pathogen bacterial culture system, in order to determine the effect of interaction between two strains of Lactobacillus plantarum and two food-borne pathogens, Listeria monocytogenes and Escherichia coli, in whole UHT milk at 37°C. To determine the type of interaction between the two bacterial populations in co-cultures and to evaluate the antagonistic activity of the lactic acid bacteria (LAB) on the pathogenic bacteria, the growth curves, the kinetic parameters, and the pH profiles of mono- and co-cultures were compared. The Lb. plantarum strains showed different bacteriocin-like inhibitory substance (BLIS) production, auto- and co-inducible. The antibacterial effect of neutralized supernatants of mono and co-cultures harvested at different times of incubation was assessed in order to establish the presence of bacteriocin-like inhibitory-substances (BLIS) and their possible relation to the growth inhibition of the pathogen. The LAB reduced the growth of Esch. coli and of List. monocytogenes by 4 and ∼5 log cycles, respectively and influenced other growth kinetic parameters, such as µ(max) and lag phase, in the different binary combinations. The growth of the LAB was not relevantly altered by simultaneous growth with the pathogenic strains showing an interaction of amensalism. The pattern of inhibition exerted by the LAB on the pathogens was different; Lb. plantarum LB279 inhibited the growth of List. monocytogenes more effectively than that of Esch. coli. The behaviour of Esch. coli in co-culture with Lb. plantarum WS4174 suggested the presence of metabolic crowding in the mechanism of growth suppression. This exploratory study showed the complexity and specific particularities of the inhibition phenomena between bacterial communities.