Water quality, availability, and acute gastroenteritis on the Navajo Nation - a pilot case-control study.

The Navajo Nation includes approximately 250,000 American Indians living in a remote high desert environment with limited access to public water systems. We conducted a pilot case-control study to assess associations between acute gastroenteritis (AGE) and water availability, use patterns, and quality. Case patients with AGE and non-AGE controls who presented for care to two Indian Health Service hospitals were recruited. Data on demographics and water use practices were collected using a standard questionnaire. Household drinking water was tested for presence of pathogens, coliforms, and residual chlorine. Sixty-one subjects (32 cases and 29 controls) participated in the study. Cases and controls were not significantly different with respect to water sources, quality, or patterns of use. Twenty-one percent (n = 12) of study participants resided in dwellings not connected to a community water system. Eleven percent (n = 7) of subjects reported drinking hauled water from unregulated sources. Coliform bacteria were present in 44% (n = 27) of household water samples, and 68% (n = 40) of samples contained residual chlorine concentrations of <0.2 mg/L. This study highlights issues with water availability, quality, and use patterns within the Navajo Nation, including sub-optimal access to community water systems, and use of water hauled from unregulated sources.

Comparison of six commercial DNA extraction kits for detection of Brucella neotomae in Mexican and Central American-style cheese and other milk products.

Raw or inadequately pasteurized milk from infected animals and cheese made with such milk are a frequent vehicle for human brucellosis infection. Also, biological terrorism is a concern with certain Brucella spp. Due to matrix-associated real-time polymerase chain reaction (qPCR) inhibitors, robust sample preparations are crucial. We compared six commercial nucleic acid extraction kits using nine Mexican and Central American-style soft cheeses or creams and three liquid milk products inoculated with Brucella neotomae, a surrogate for pathogenic Brucella spp. Kits were evaluated by purity and quantity of DNA as determined by qPCR Ct values, reproducibility across cheese and milk types, and cost. At 10(7) CFU/g in four different cheeses, Qiagen statistically outperformed all other kits. When two cheese styles were inoculated at dual levels, Qiagen and High Pure kit extracted samples at 1.5 × 10(5) CFU/g produced average Ct values of 34-39, while PrepSEQ and MagMAX kit extracted samples exhibited higher or no Ct values. High Pure and Qiagen kits excelled also with liquid milk products. Considering matrices, inoculation levels, and kits evaluated, High Pure and Qiagen products produced Brucella DNA of high quality and quantity indicated by the lowest Ct values and were the least expensive.

Characterization of microflora in Latin-style cheeses by next-generation sequencing technology.

BACKGROUND: Cheese contamination can occur at numerous stages in the manufacturing process including the use of improperly pasteurized or raw milk. Of concern is the potential contamination by Listeria monocytogenes and other pathogenic bacteria that find the high moisture levels and moderate pH of popular Latin-style cheeses like queso fresco a hospitable environment. In the investigation of a foodborne outbreak, samples typically undergo enrichment in broth for 24 hours followed by selective agar plating to isolate bacterial colonies for confirmatory testing. The broth enrichment step may also enable background microflora to proliferate, which can confound subsequent analysis if not inhibited by effective broth or agar additives. We used 16S rRNA gene sequencing to provide a preliminary survey of bacterial species associated with three brands of Latin-style cheeses after 24-hour broth enrichment. RESULTS: Brand A showed a greater diversity than the other two cheese brands (Brands B and C) at nearly every taxonomic level except phylum. Brand B showed the least diversity and was dominated by a single bacterial taxon, Exiguobacterium, not previously reported in cheese. This genus was also found in Brand C, although Lactococcus was prominent, an expected finding since this bacteria belongs to the group of lactic acid bacteria (LAB) commonly found in fermented foods. CONCLUSIONS: The contrasting diversity observed in Latin-style cheese was surprising, demonstrating that despite similarity of cheese type, raw materials and cheese making conditions appear to play a critical role in the microflora composition of the final product. The high bacterial diversity associated with Brand A suggests it may have been prepared with raw materials of high bacterial diversity or influenced by the ecology of the processing environment. Additionally, the presence of Exiguobacterium in high proportions (96%) in Brand B and, to a lesser extent, Brand C (46%), may have been influenced by the enrichment process. This study is the first to define Latin-style cheese microflora using Next-Generation Sequencing. These valuable preliminary data will direct selective tailoring of agar formulations to improve culture-based detection of pathogens in Latin-style cheese.