Survivability of Salmonella and Shigella spp. in sodium lauryl sulfate and tween 80 at 22 and 40 degrees C

Control of Listeria monocytogenes on vacuum-packaged frankfurters sprayed with lactic acid alone or in combination with sodium lauryl sulfate

U.S. regulations require that processors employ lethal or inhibitory antimicrobial alternatives in production of ready-to-eat meat and poultry products that support growth of Listeria monocytogenes and may be exposed to the processing environment after a lethality treatment. In this study, lactic acid (LA; 5%, vol/vol) and sodium lauryl sulfate (SLS; 0.5%, wt/vol) were evaluated individually or as a mixture (LASLS) for control of L. monocytogenes on frankfurters. Frankfurters were inoculated with a 10-strain mixture of L. monocytogenes, sprayed for 10 s (20 bar, 23 +/- 2 degrees C) with antimicrobials or distilled water (DW) before (LASLS or DW) or after (LA, SLS, LASLS, or DW) inoculation (4.8 +/- 0.1 log CFU/cm2), vacuum packaged, and stored at 4 degrees C for 90 days. Samples were analyzed for numbers of the pathogen (on PALCAM agar) and for total microbial counts (on tryptic soy agar with yeast extract) during storage. Spraying with DW, LA, or SLS after inoculation reduced numbers of L. monocytogenes by 1.3 +/- 0.2, 1.8 +/- 0.5, and 2.0 +/- 0.4 log CFU/cm2, respectively. The LASLS mixture applied before or after inoculation reduced pathogen populations by 1.8 +/- 0.4 and 2.8 +/- 0.2 log CFU/cm2, respectively. No further reduction by any treatment was observed during storage. The bacterial growth curves (fitted by the model of Baranyi and Roberts) indicated that the lag-phase duration of the bacterium on control samples (13.85 to 15.18 days) was extended by spraying with all solutions containing LA. For example, LA suppressed growth of L. monocytogenes for 39.14 to 41.01 days. Pathogen growth rates also were lower on frankfurters sprayed after inoculation with LA or LASLS compared to those sprayed with DW. Therefore, spraying frankfurters with a mixture of LA and SLS may be a useful antilisterial alternative treatment for ready-to-eat meat and poultry products.

Isolation, molecular characterization and antimicrobial resistance patterns of Salmonella and Escherichia coli isolates from meat-based fast food in Lebanon

The aim of this study was to characterize at the molecular level the different stains of Salmonella spp. and Escherichia coli that were isolated from meat-based fast food in Lebanon. In addition, this study evaluated the resistance of those strains to different antimicrobials that are commonly used. The foods included were Lahm-bi-Ajeen (LBA, meat pies) and Shawarma (Lebanese meat sandwiches similar to Gyros and Donairs, containing meat, vegetables, and sesame seeds-oil-based sauce). Polymerase chain reaction (PCR) was used to characterize and identify the strains of both bacteria. Salmonella species characterization was performed using rfb genes cluster genetic marker, while that of E. coli strains were carried out based on stx1, stx2, eaeA, fliC, and ehlyA virulence markers. The characterized strains were then tested for their response to various antimicrobials. The results showed that the tested foods were contaminated with Salmonella paratyphi (serogroup A) and Shiga Toxin (Stx)-producing E. coli (STX-EC). The PCR showed that 75% of E. coli tested strains was positive in PCR performed with stx1 primers, one of which was eaeA positive. Two of the tested strains were positive using PCR with fliC primers. The resistances of the various strains were evaluated using the following antimicrobials: Oxacillin, Teicoplanin, Trimethoprim/sulfamethoxazole, Gentamicin, Clindamycin, Cefotaxime, Cefuroxime, Erythromycin, and Vancomycin. Bacteria were highly resistant to one or more of the tested antimicrobials. Approximately 69% of E. coli and 77.8% of Salmonella spp. exhibited resistance. Salmonella spp. were shown to be 100% resistant to four antimicrobials: Oxacillin, Teicoplanin, Clindamycin, Vancomycin, and Erythromycin, while E. coli was 100% resistant to Teicoplanin and Trimethoprim/sulfamethoxazole. The most interesting findings were the high susceptibility of the E. coli to Gentamicin (100%). Highest resistance in the case of Salmonella spp. was seen against Cefotaxime (74%). Those two antimicrobials are commonly used for the treatment of enteric infections caused by gram-negative bacteria. The results showed that meat-based fast foods in Lebanon could be a public health hazard, especially Shawarma, as they may act as a potential vehicle for many antimicrobial-resistant pathogenic organisms. Improper hygienic standards and indiscriminate use of antimicrobials are two of the main causes for the prevalence of these pathogenic resistance strains in Lebanon. These results will emphasize the need to implement protective measures and more emphasis will be placed on the application of hygienic practices to reduce the levels of food contamination.