Production of reuterin in a fermented milk product by Lactobacillus reuteri: Inhibition of pathogens, spoilage microorganisms, and lactic acid bacteria.

We assessed the antimicrobial activity of reuterin produced in vitro in glycerol aqueous solutions in situ by Lactobacillus reuteri ATCC 53608 as part of a fermented milk product against starter (Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus), spoilage (Penicillium expansum), pathogenic (Staphylococcus aureus Salmonella enterica ssp. enterica, and Listeria monocytogenes), and pathogen surrogate (Escherichia coli DH5α) microorganisms. We also assayed the influence of cold storage (28 d at 4°C) and reuterin on the color and rheology of the fermented milk product. We obtained maximum reuterin concentrations of 107.5 and 33.97 mM in glycerol aqueous solution and fermented milk product, respectively. Reuterin was stable throughout its refrigerated shelf life. Gram-positive microorganisms were more resistant to reuterin than gram-negative microorganisms. Penicillium expansum and Lactobacillus reuteri ATCC 53608 survived at concentrations up to 10 and 8.5 mM, respectively. Escherichia coli DH5α was the most sensitive to reuterin (0.9 mM). The presence of reuterin did not cause relevant changes in the quality parameters of the fermented milk product, including pH, acidity, soluble solids, color, and rheological aspects (storage and loss moduli and viscosity). This study demonstrated the viability of using Lactobacillus reuteri ATCC 53608 as a biopreservative in a fermented milk product through reuterin synthesis, without drastically modifying its quality parameters.

Irrigation water quality and the benefits of implementing good agricultural practices during tomato (Lycopersicum esculentum) production.

The implementation of good agricultural practices (GAP) from irrigation water to the tomato packaging process enhances the safety of fresh produce and its value throughout the food chain. The aim of the present study was to show that fresh produce farms that apply and enforce GAP could reduce the presence of Salmonella in finished produce. Samples were collected biweekly from six packing houses from the central region of Sinaloa, México, for the isolation of Salmonella spp by the ISO 6579:2002 method, and the isolated strains were serotyped and genotyped by the Kauffmman-White scheme and pulsed field gel electrophoresis (PFGE), respectively. Salmonella strains were detected in 13 (36.1 %) irrigation water samples, while only two tomato samples were positive (5.5 %). Eight different serotypes were identified in irrigation water, and Salmonella Oranienburg (34 %) was the most prevalent; however, only Salmonella Agona and Salmonella Weltevreden were present on tomatoes. Salmonella Oranienburg was the most widely dispersed and variable serotype, with 10 different PFGE profiles. Salmonella Weltevreden was isolated from both types of samples, albeit with distinct genetic profiles, implying that the sources of contamination differ. These results confirm the utility of implementing good agricultural practices to reduce Salmonella contamination in irrigation water and the packaging process.

Detection of pathogenic micro-organisms on children's hands and toys during play.

AIMS: This study aimed to determine if the children's leisure activities impact the presence of pathogens on their hands and toys. METHODS & RESULTS: To assess the microbiological hazard in playground areas, a pilot study that included 12 children was conducted. We then conducted an intervention study; children's hands and toys were washed before playing. Faecal coliforms, pathogenic bacteria and Giardia lamblia were quantified by membrane filtration, selective media and flotation techniques, respectively; rotavirus, hepatitis A and rhinovirus by RT-PCR. Pilot study results revealed faecal contamination on children's hands and toys after playing on sidewalks and in public parks. Pathogenic bacteria, hepatitis A and G. lamblia on children's hands were also found. In the intervention study, Staphylococcus aureus and Klebsiella pneumoniae were found on children's hands at concentrations up to 2·5 × 10(4) and 1 × 10(4) CFU hands(-1), respectively. E. coli and Kl. pneumoniae were detected on toys (2·4 × 10(3) and 2·7 × 10(4) CFU toy(-1), respectively). Salmonella spp, Serratia spp and G. lamblia cysts were also present on toys. CONCLUSION: Children's play activities influence microbial presence on hands and toys; the transfer seems to occur in both ways. SIGNIFICANCE AND IMPACT OF THE STUDY: Control strategy needs to be implemented to protect children from infectious diseases.

First Report of Blue Mold Caused by Penicillium oxalicum in Tomato (Solanum lycopersicum) in Mexico.

Tomato is the primary vegetable exported from Mexico to the United States. In June 2007, stem rots were observed in tomato cv. Imperial plants growing in a greenhouse in the Culiacan Valley. Disease symptoms included stem rot with a mycelial growth with a grayish blue sporulation. The disease was observed to be affecting 1% of the tomato plants growing in the greenhouse, and has been observed sporadically in greenhouses during subsequent agricultural cycles in other tomato-growing areas in Mexico. Affected stems showed initial symptoms of a dark brown necrotic area surrounding only the cut regions of pruned leaves and stems. As the infection continued on the tissues, the spot grew and then became covered with a grayish blue sporulation. Severe stem rot led to death of the plants. Rotted stems of tomato plants were collected and samples of the infected tissues were plated onto potato dextrose agar (PDA) to isolate the fungus. The preliminary identification of the pathogen was Penicillium oxalicum Currie & Thom on the basis of morphological criteria with ellipsoidal conidia approximately 4 × 3 µm borne in columns, conidiophores mostly biverticillate, and ampulliform phialides (2). The identification was confirmed by sequencing internal transcribed spacer 1 (ITS1), 5.8S, and ITS2 regions of the ribosomal DNA (GenBank Accession No. HM452308). The isolate was deposited in the Coleccion Nacional Microbiana y de Cultivos Celulares CINVESTAV-IPN, Mexico. Koch's postulates were fulfilled by reproducing stem rots on healthy inoculated tomato stems. Pathogenicity testing involved fungal growth on PDA for 5 days, after which a 4-mm disk of actively growing mycelia was transferred to wounds (4 × 4 mm) made with a scalpel in stems of 6-week-old tomato cv. Imperial plants. Inoculated plants were covered with plastic bags to maintain a high relative humidity for 24 h and were maintained in a greenhouse at 25 ± 2°C. Seven days after inoculation, all of the inoculated stems showed rot symptoms similar to those observed in the greenhouse. Stems that were inoculated only with an agar disk did not show any symptoms of the disease. The pathogen was reisolated from inoculated plants but not from noninoculated plants. Artificial inoculation was performed twice. Although P. oxalicum has been previously reported as a causal agent of cucumber (1) and tomato stem rots in Japan (3), to our knowledge, this is the first report of P. oxalicum causing stem rot in tomato plants in Mexico. References: (1) T. M. O'Neill et al. Plant Pathol. 40:78, 1991. (2) J. I. Pitt. The Genus Penicillium and Its Teleomorphic States Eupenicillium and Talaromyces. Academic Press, London, UK, 1979. (3) S. Umemoto et al. J. Gen. Plant Pathol. 75:399, 2009.

Impact of prescribed cleaning and disinfectant use on microbial contamination in the home.

AIMS: To identify and quantify the presence of Escherichia coli, Staphylococcus aureus, Salmonella, hepatitis A and norovirus in households and to assess the effect of chlorine and quaternary ammonium-based disinfectants following a prescribed use. METHODS AND RESULTS: Eleven sites distributed in kitchen, bathroom, pet and children's areas of two groups of 30 homes each: (i) a nonprescribed disinfectant user group and (ii) a disinfectant protocol user group. During the 6-week study, samples were collected once a week except for week one when sample collection occurred immediately before and after disinfectant application to evaluate the disinfectant protocol. The concentration and occurrence of bacteria were less in the households with prescribed use of disinfectants. The greatest reductions were for E. coli (99%) and Staph. aureus (99·9999%), respectively. Only two samples were positive for HAV, while norovirus was absent. Disinfection protocols resulted in a significant (P < 0·05) microbial reduction in all areas of the homes tested compared to homes not using a prescribed protocol. CONCLUSIONS: The study suggests that disinfectant product application under specific protocol is necessary to achieve greater microbial reductions. SIGNIFICANCE AND IMPACT OF THE STUDY: Prescribed protocols constitute an important tool to reduce the occurrence of potential disease-causing micro-organisms in households.

Detection and characterization of hepatitis A virus and Norovirus in estuarine water samples using ultrafiltration--RT-PCR integrated methods.

AIMS: Waterborne outbreaks of hepatitis A and Norovirus disease have been reported and associated with contaminated water supply in various countries. However, in Mexico, there are no studies that report HAV and NV presence in water. This study reports the application of ultrafiltration and RT-nested PCR methods to concentrate and identify these viruses. METHODS AND RESULTS: Forty estuarine water samples were collected from the Huizache Caimanero Lagunary Complex. Samples were concentrated by ultrafiltration system (UFS) and RT-nested PCR was performed for HAV and NV identification. These viruses were found in 80% and 70% of the samples collected respectively and both were present in 57.5%. The DNA sequences analysis showed that 21 estuarine water samples were associated with HAV and 13 with NV. Faecal coliforms were isolated in 48.57% of the samples, while Escherichia coli were found in 34.28%. CONCLUSIONS: DNA sequencing showed that the genotype IB for HAV and GII for NV were predominant in México. No significant relationships were detected between indicators and viruses (P < 0.05). SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows that the UFS is adequate for viral concentration. This is the first study analysing the genetic sequence of HAV and NV isolated from Mexican estuarine water.