Campylobacter jejuni is a leading cause of bacterial gastroenteritis in humans, and contamination of poultry has been implicated in illness. The bacteria are fastidious in terms of their temperature requirements, being unable to grow below ca. 31°C, but have been found to be physiologically active at lower temperatures and to tolerate exposure to low temperatures in a strain-dependent manner. In this study, 19 field isolates of C. jejuni (10 of clinical and 9 of poultry origin) were studied for their ability to tolerate prolonged exposure to low temperature (4°C). Although substantial variability was found among different strains, clinical isolates tended to be significantly more likely to remain viable following cold exposure than poultry-derived strains. In contrast, the relative degree of tolerance of the bacteria to freezing at ؊20°C and freeze-thawing was strain specific but independent of strain source (poultry versus clinical) and degree of cold (4°C) tolerance.Campylobacter jejuni is currently a leading cause of bacterial gastroenteritis in humans (1,20,30). Infection by C. jejuni is also the most common antecedent to Guillain-Barré syndrome, an autoimmune disorder of the peripheral nervous system (19). C. jejuni and related campylobacters are unique among human food-borne pathogens in being obligate microaerophiles and in their narrow and rather unusual temperature range for growth. C. jejuni and other "thermophilic campylobacters" grow optimally at a relatively high temperature (42°C), but their minimal growth temperature is in the range of 31 to 36°C (3,5,8), and growth ceases abruptly around 30°C (8).C. jejuni is a commensal microbe in avian species, including poultry (13, 36), and epidemiological studies have frequently implicated raw and undercooked poultry in human campylobacteriosis (1,20,30). A substantial portion (as much as 98%) of poultry at retail is contaminated with the pathogen (1, 29). Other meat products can also be contaminated with Campylobacter and can contribute to human illness, along with untreated water, raw milk, and exposure to live birds and to pets with diarrhea (1,20).Several studies suggest that, in spite of fastidious requirements for growth, C. jejuni has the potential for remarkable survival under conditions nonpermissive to growth. In surface waters and water microcosms, survival was shown to be limited to a few days at ambient temperatures of ca. 20°C but was noticeably enhanced (up to several weeks) at 4°C (2, 22, 31). Rollins and Colwell (26) showed that at 4°C C. jejuni could survive and remain at the viable but nonculturable stage for about 4 months. Oxygen consumption, catalase activity, ATP generation, chemotaxis, and protein synthesis were also observed at 4°C (8). Furthermore, Lee et al. (15) showed that C. jejuni remained viable on raw chicken skin fragments at Ϫ20 and Ϫ70°C for 14 and 56 days, respectively. In the same study, C. jejuni was also able to persist on the chicken skin fragments at 4°C (15).The ability of C. jejuni to survive refrigeration and fr...

Listeria monocytogenes of serotype 4b has been implicated in numerous outbreaks of food-borne listeriosis and in ca. 40% of sporadic cases. Strains of this serotype appear to be relatively homogeneous genetically, and molecular markers specific for distinct serotype 4b lineages have not been frequently identified. Here we show that DNA fragments derived from the putative mannitol permease locus of Listeria monocytogenes had an unexpectedly high potential to differentiate among different strains of serotype 4b when used as probes in Southern blotting of EcoRI-digested genomic DNA, yielding four distinct restriction fragment length polymorphism (RFLP) patterns. Strains of two epidemic-associated lineages, including the major epidemic clone implicated in several outbreaks in Europe and North America, had distinct RFLPs which differed from those of all other serotype 4b strains that we screened but which were encountered among strains of serotypes 1/2b and 3b. In addition, three serogroup 4 lineages were found to have unique RFLPs that were not encountered among any other L. monocytogenes strains. One was an unusual lineage of serotype 4b, and the other two were members of the serotype 4a and 4c group. The observed polymorphisms may reflect evolutionary relationships among lineages of L. monocytogenes and may facilitate detection and population genetic analysis of specific lineages.

Teichoic acid-associated N-acetylglucosamine and rhamnose have been shown to serve as phage receptors in Listeria monocytogenes serotype 1/2a. We generated and characterized two single-copy Tn916ΔE mutants which were resistant to phage A118 and several other serotype 1/2a-specific phages. In one mutant the insertion was immediately upstream of the recently identifiedptsHI locus, which encodes two proteins of the phosphoenolpyruvate-dependent carbohydrate uptake system, whereas in the other the insertion was immediately upstream of an operon whose most distal gene was clpC, involved in stress responses and virulence. Transduction experiments confirmed the association of the phage-resistant phenotype of these mutants with the transposon insertion. Phage A118 resistance of the mutants could be attributed to inability of the phage to adsorb onto the mutant cells, and biochemical analysis of cell wall composition showed that the teichoic acids of both mutants were deficient in N-acetylglucosamine. Rhamnose and other teichoic acid and cell wall components were not affected.

Three experiments (EXP) were conducted to evaluate effectiveness of Bacillus strains on pathogen inhibition in vitro (EXP. 1 and 2) and on growing-finishing pig performance and bacteria shedding (EXP. 3). In EXP. 1, antimicrobial activity of 4 individual Bacillus strains were tested against 9 bacterial pathogens using agar diffusion cross-streak assay. In EXP. 2, a combination of 4 strains (FS4) was evaluated for antimicrobial activity against surrogate strains of the same pathogens in EXP. 1 using well-diffusion and competitive exclusion assays. There were strong inhibitory effects against Streptococcus agalactiae and Staphylococcus aureus aureus with zones of inhibition (ZOI) up to 18.1 and 13.7 mm, respectively. Moderate effects were observed against Listeria monocytogenes, Bordetella bronchiseptica, Escherichia coli, and Salmonella enterica serovar Typhimurium with ZOI up to 8.7, 8.7, 8.1, and 6.3 mm, respectively. On broth, FS4 inhibited Listeria completely (9 log10 CFU/mL) and reduced Staphylococcus by 8 log10 CFU/mL after 24h co-cultivation. In EXP. 3, 236 pigs (initial BW: 33 kg; 6–7 pigs/pen; 17 pens/treatment) were used to evaluate effects of feeding FS4 (7.5 x 104 CFU/g of feed) vs. the control (CON) diets. On d 0, 49, and at market, a pooled fresh fecal sample per pen was obtained for the enumeration of total Salmonella, E. coli, coliform, and Lactobacillus. Feeding FS4 improved (P < 0.05) BW (d 72), ADG (d 43–72 and d 0–72), and Feed:Gain (d 43–72) compared to CON. Overall, pigs fed FS4 were numerically heavier (1.1 kg) than CON pigs. FS4 reduced (P < 0.05) total coliform counts in pigs at market, and numerically reduced E. coli at d 49; however, FS4 had no impact on Lactobacillus. Our data indicate that FS4 had strong inhibitory effects against Streptococcus, Listeria, and Staphylococcus and feeding FS4 improved performance of pigs and lowered coliform shedding without impacting Lactobacillus.