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Aims This study aims to investigate the in vitro pathogenicity of Chromobacterium haemolyticum strain WI5 toward the intestinal tract, its resistance to water treatments, and its potential for foodborne transmission through leafy greens produced in hydroponic systems. Methods and results C. haemolyticum WI5 caused cytopathic effects in human colon cells HCT116 and exhibited an 8.2-fold higher cell attachment compared to Salmonella serotype Typhimurium. It showed comparable resistance to sodium hypochlorite (NaOCl) and ultraviolet (UV) treatments as Escherichia coli O157: H7 and Pseudomonas aeruginosa but was more susceptible to desiccation. On lettuce, C. haemolyticum WI5 failed to persist, with counts decreasing below the detection limit (≥4 log reductions) after 3 and 2 days at 4 and 25°C, respectively. Conclusions C. haemolyticum WI5 demonstrated considerable virulence features and high in vitro pathogenicity toward the intestinal tract. NaOCl and UV treatments were effective in disinfecting C. haemolyticum in water. Due to its high susceptibility to desiccation and poor survivability on lettuce, the foodborne transmission potential of C. haemolyticum is considered limited. [ABSTRACT FROM AUTHOR]

Aims: We investigated the fate of Salmonella in lettuce seeds grown in a hydroponic system and the potentials of applying photodynamic inactivation (PDI) to enhance microbial safety of hydroponic farming systems. Methods and Results: Lettuce was grown from Salmonella‐contaminated seeds, and rose bengal‐mediated PDI was applied. Without intervention, Salmonella could persist in plants and hydroponic farming environment throughout 6 weeks of lettuce growth. Cross‐contamination from Salmonella‐inoculated to noninoculated seedlings was observed. PDI significantly decreased Salmonella from 3.90 ± 0.31 log colony‐forming unit (CFU) per plant to 2.77 ± 0.49 log CFU per plant without extra illumination needed (p < 0.01) by week six. Conclusions: Salmonella from contaminated seeds could survive for an extended period in lettuce and hydroponic farming environment and posed serious cross‐contamination risks. Rose bengal‐mediated PDI showed promise in controlling Salmonella contamination in lettuce in a hydroponic farming setting. Significance and Impact of the Study: This study shed light on the serious food safety implications that Salmonella‐contaminated lettuce seeds might entail in a hydroponic farming environment and demonstrated rose bengal‐mediated PDI as a potential mitigation strategy. These findings contribute to the increasingly relevant field of urban farming systems and their associated food safety concerns. [ABSTRACT FROM AUTHOR]

Although conventionally considered an animal pathogen, recent evidence increasingly suggests that fresh produce may act as significant transmission vehicles and alternative hosts to Salmonella. This study reports the differential survivability of two genetically similar Salmonella Thompson strains (ST 889B and ST 688C) on the adaxial surface of pre-harvest basil (Ocimum basilicum) leaves. Upon inoculation, two distinct phenomena, a dried water-print or a macroscopic lesion, were observed within 24 h. ST 889B survived better than ST 688C on healthy-looking leaves without lesions, possibly due to its higher biofilm-forming ability. Both strains survived better on the leaves with lesions than on the healthy-looking leaves (ST 688C: 4.39 ± 0.68 vs. 2.18 ± 0.29; ST 889B: 4.78 ± 0.12 vs. 2.83 ± 0.18 log CFU per sample at 6 days post-inoculation). ST 889B caused the formation of lesions at a higher frequency [70/117 leaves (59.8%)] than ST 688C [35/96 leaves (36.5%)]. Thus, we highlighted two distinct Salmonella survival strategies in the basil pathosystem and demonstrated gene expression polymorphism (variations in the expression of the same set of genes) as an indispensable strategy in the colonization of plants as hosts by the human pathogens. [ABSTRACT FROM AUTHOR]

Group B Streptococcus (GBS) was previously not known to be transmitted through food, but an outbreak investigation in Singapore in 2015 documented for the first time an association between GBS Type III Sequence Type 283 infection and consumption of raw fish dishes. As very little is known about the survival of GBS during heat treatment and the stomach transit, its survival under simulated conditions was studied, in comparison with that of Escherichia coli O157:H7 and Listeria monocytogenes. The mean D-values of four GBS strains ranging from 0.72 to 0.88 min in neutral pH tryptone soy broth at 56.4 °C and 0.44–1.43 min at pH 2.35 at 37 °C in simulated gastric fluid, were significantly lower (p < 0.05) than those of E. coli O157:H7 and L. monocytogenes. This study suggests possible factors other than acid or heat resistance of GBS to be instrumental to its pathogenicity. [ABSTRACT FROM AUTHOR]

Background: Salmonella enterica subspecies enterica serovar Saintpaul (S. Saintpaul) is an important gut pathogen which causes salmonellosis worldwide. Although intestinal salmonellosis is usually self-limiting, it can be life-threatening in children, the elderlies and immunocompromised patients. Appropriate antibiotic treatment is therefore required for these patients. However, the efficacy of many antibiotics on S. enterica infections has been greatly compromised due to spreading of multidrug resistance (MDR) plasmids, which poses serious threats on public health and needs to be closely monitored. In this study, we sequenced and fully characterized an S. enterica MDR plasmid pSGB23 isolated from chicken. Results: Complete genome sequence analysis revealed that S. Saintpaul strain SGB23 harbored a 254 kb megaplasmid pSGB23, which carries 11 antibiotic resistance genes responsible for resistance to 9 classes of antibiotics and quaternary ammonium compounds that are commonly used to disinfect food processing facilities. Furthermore, we found that pSGB23 carries multiple conjugative systems, which allow it to spread into other Enterobacteriaceae spp. by self-conjugation. It also harbors multiple types of replicons and plasmid maintenance and addictive systems, which explains its broad host range and stable inheritance. Conclusions: We report here a novel MDR plasmid pSGB23 harboured by S. enterica. To our knowledge, it carried the greatest number of antibiotic resistance genes with the broadest range of resistance spectrum among S. enterica MDR plasmids identified so far. The isolation of pSGB23 from food sources is worrisome, while surveillance on its further spreading will be carried out based on the findings reported in this study. [ABSTRACT FROM AUTHOR]