title: Sensitivity of Shiga toxin-producing Escherichia coli, multidrug-resistant Salmonella, and antibiotic-susceptible Salmonella to lactic acid on inoculated beef trimmings.
abstract: Studies were performed to determine whether lactic acid treatments used to reduce Escherichia coli O157:H7 on beef trimmings are also effective in controlling non-O157 Shiga toxin-producing E. coli (nSTEC), and multidrug-resistant and antibiotic-susceptible Salmonella.  Beef trimming pieces (10 by 5 by 1 cm) were inoculated (3 log CFU/cm(2)) separately with four-strain mixtures of rifampin-resistant E. coli O157:H7, O26, O45, O103, O111, O121, and O145. Similarly, in a second study, trimmings were separately inoculated with rifampin-resistant  E. coli O157:H7, and antibiotic-susceptible or multidrug-resistant (MDR and/or MDR-AmpC) Salmonella Newport and Salmonella Typhimurium. Inoculated trimmings were left untreated (control) or were immersed for 30 s in 5% lactic acid solutions (25 or 55°C). No differences  (P ≥ 0.05) were obtained among surviving counts of E. coli O157:H7 and those of the tested nSTEC serogroups on lactic acid-treated (25 or 55°C) samples. Counts (3.1 to 3.3 log CFU/cm(2)) of E. coli O157:H7 and nSTEC were reduced (P < 0.05)  by 0.5 to 0.9 (25°C lactic acid) and 1.0 to 1.4 (55°C lactic acid) log CFU/cm(2). Surviving counts of Salmonella on treated trimmings were not influenced by serotype or antibiotic resistance phenotype and were similar (P ≥ 0.05) or lower (P < 0.05)  than surviving counts of E. coli O157:H7. Counts (3.0 to 3.3 log CFU/cm(2)) were reduced (P < 0.05) by 0.5 to 0.8 (E. coli O157:H7) and 1.3 to 1.5 (Salmonella) log CFU/cm(2) after treatment of samples with 25°C lactic acid. Corresponding  reductions following treatment with lactic acid at 55°C were 1.2 to 1.5 (E. coli O157:H7) and 1.6 to 1.9 (Salmonella) log CFU/cm(2). Overall, the results indicated that lactic acid treatments used against E. coli O157:H7 on beef trimmings should be similarly  or more effective against the six nSTEC serogroups and against multidrug-resistant and antibiotic-susceptible Salmonella Newport and Salmonella Typhimurium.
authors.affiliation: Center for Meat Safety & Quality, Department of Animal Sciences, Colorado State University, Fort Collins, Colorado 80523-1171, USA.
authors.forename: Aliyar
authors.initials: A
authors.lastname: Fouladkhah
authors.forename: Ifigenia
authors.initials: I
authors.lastname: Geornaras
authors.forename: Hua
authors.initials: H
authors.lastname: Yang
authors.forename: Keith E
authors.initials: KE
authors.lastname: Belk
authors.forename: Kendra K
authors.initials: KK
authors.lastname: Nightingale
authors.forename: Dale R
authors.initials: DR
authors.lastname: Woerner
authors.forename: Gary C
authors.initials: GC
authors.lastname: Smith
authors.forename: John N
authors.initials: JN
authors.lastname: Sofos
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002417:Cattle; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004305:Dose-Response Relationship, Drug; D024881:Drug Resistance, Bacterial; D024901:Drug Resistance, Multiple, Bacterial; D005506:Food Contamination / Q000032:analysis / Q000517:prevention & control; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D006801:Humans; D019344:Lactic Acid / Q000494:pharmacology*; D008460:Meat / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D012475:Salmonella / Q000187:drug effects* / Q000254:growth & development; D012703:Serotyping; D054323:Shiga-Toxigenic Escherichia coli / Q000187:drug effects* / Q000254:growth & development; D013696:Temperature
chemical_list: D000900:Anti-Bacterial Agents; D019344:Lactic Acid