A total of 825 samples of retail raw meats (chicken, turkey, pork, and beef) were examined for the presence ofEscherichia coliandSalmonellaserovars, and 719 of these samples were also tested forCampylobacterspp. The samples were randomly obtained from 59 stores of four supermarket chains during 107 sampling visits in the Greater Washington, D.C., area from June 1999 to July 2000. The majority (70.7%) of chicken samples (n= 184) were contaminated withCampylobacter, and a large percentage of the stores visited (91%) hadCampylobacter-contaminated chickens. Approximately 14% of the 172 turkey samples yieldedCampylobacter, whereas fewer pork (1.7%) and beef (0.5%) samples were positive for this pathogen. A total of 722Campylobacterisolates were obtained from 159 meat samples; 53.6% of these isolates wereCampylobacter jejuni, 41.3% wereCampylobacter coli, and 5.1% were other species. Of the 212 chicken samples, 82 (38.7%) yieldedE. coli, while 19.0% of the beef samples, 16.3% of the pork samples, and 11.9% of the turkey samples were positive forE. coli. However, only 25 (3.0%) of the retail meat samples tested were positive forSalmonella. Significant differences in the bacterial contamination rates were observed for the four supermarket chains. This study revealed that retail raw meats are often contaminated with food-borne pathogens; however, there are marked differences in the prevalence of such pathogens in different meats. Raw retail meats are potential vehicles for transmitting food-borne diseases, and our findings stress the need for increased implementation of hazard analysis of critical control point (HACCP) and consumer food safety education efforts.

A total of 50 isolates of Shiga toxin-producing Escherichia coli (STEC), including 29 O157:H7 and 21 non-O157 STEC strains, were analyzed for antimicrobial susceptibilities and the presence of class 1 integrons. Seventy-eight ( n = 39) percent of the isolates exhibited resistance to two or more antimicrobial classes. Multiple resistance to streptomycin, sulfamethoxazole, and tetracycline was most often observed. Class 1 integrons were identified among nine STEC isolates, including serotypes O157:H7, O111:H11, O111:H8, O111:NM, O103:H2, O45:H2, O26:H11, and O5:NM. The majority of the amplified integron fragments were 1 kb in size with the exception of one E. coli O111:H8 isolate which possessed a 2-kb amplicon. DNA sequence analysis revealed that the integrons identified within the O111:H11, O111:NM, O45:H2, and O26:H11 isolates contained the aadA gene encoding resistance to streptomycin and spectinomycin. Integrons identified among the O157:H7 and O103:H2 isolates also possessed a similar aadA gene. However, DNA sequencing revealed only 86 and 88% homology, respectively. The 2-kb integron of the E. coli O111:H8 isolate contained three genes, dfr XII, aadA 2, and a gene of unknown function, orfF , which were 86, 100, and 100% homologous, respectively, to previously reported gene cassettes identified in integrons found in Citrobacter freundii and Klebsiella pneumoniae . Furthermore, integrons identified among the O157:H7 and O111:NM strains were transferable via conjugation to another strain of E. coli O157:H7 and to several strains of Hafnia alvei . To our knowledge, this is the first report of integrons and antibiotic resistance gene cassettes in STEC, in particular E. coli O157:H7.

Retail organic ( n = 198) and conventional ( n = 61) chickens were analyzed. Most organic (76%) and conventional (74%) chickens were contaminated with campylobacters. Salmonellae were recovered from 61% of organic and 44% of conventional chickens. All Salmonella enterica serovar Typhimurium isolates from conventional chickens were resistant to five or more antimicrobials, whereas most S. enterica serovar Typhimurium isolates (79%) from organic chickens were susceptible to 17 antimicrobials tested.

Recent outbreaks linked toSalmonella-contaminated produce heightened the need to develop simple, rapid, and accurate detection methods, particularly those capable of determining cell viability. In this study, we examined a novel strategy for the rapid detection and quantification of viable salmonellae in produce by coupling a simple propidium monoazide sample treatment with loop-mediated isothermal amplification (PMA-LAMP). We first designed and optimized a LAMP assay targetingSalmonella. Second, the performance of PMA-LAMP for detecting and quantifying viable salmonellae was determined. Finally, the assay was evaluated in experimentally contaminated produce items (cantaloupe, spinach, and tomato). Under the optimized condition, PMA-LAMP consistently gave negative results for heat-killedSalmonellacells with concentrations up to 10⁸CFU/ml (or CFU/g in produce). The detection limits of PMA-LAMP were 3.4 to 34 viableSalmonellacells in pure culture and 6.1 × 10³to 6.1 × 10⁴CFU/g in spiked produce samples. In comparison, PMA-PCR was up to 100-fold less sensitive. The correlation between LAMP time threshold (T_T) values and viableSalmonellacell numbers was high (R²= 0.949 to 0.993), with a quantification range (10²to 10⁵CFU/reaction in pure culture and 10⁴to 10⁷CFU/g in produce) comparable to that of PMA in combination with quantitative real-time PCR (PMA-qPCR). The complete PMA-LAMP assay took about 3 h to complete when testing produce samples. In conclusion, this rapid, accurate, and simple method to detect and quantify viableSalmonellacells in produce may present a useful tool for the produce industry to better control potential microbial hazards in produce.

The antimicrobial susceptibilities of 168 Vibrio parahaemolyticus and 151 Vibrio vulnificus isolates recovered from 82 Louisiana Gulf and retail oysters in 2005 and 2006 were determined. Overall, the two vibrios remained susceptible to the majority of antimicrobials tested; reduced susceptibility was detected only in V. parahaemolyticus for ampicillin (81%; MIC ≥ 16 μg/ml). Additionally, V. parahaemolyticus displayed significantly higher MICs for cefotaxime, ciprofloxacin, and tetracycline than V. vulnificus .