Vanessa Burrowes

Microbial Indicator Profiling of Fresh Produce and Environmental Samples from Farms and Packing Facilities in Northern Mexico.

To compare microbiological indicator and pathogen contamination among different types of fresh produce and environmental samples along the production chain, 636 samples of produce (rinsates from cantaloupe melons, jalapeño peppers, and tomatoes) and environmental samples (rinsates from hands of workers, soil, and water) were collected at four successive steps in the production process (from the field before harvest through the packing facility) on 11 farms in northern Mexico during 2011 and 2012. Samples were assayed for enteric pathogens (Escherichia coli O157:H7, other Shiga toxigenic E. coli, Salmonella, and Listeria monocytogenes) and microbial indicators (coliforms, other E. coli strains, and Enterococcus spp.). Salmonella was the only pathogen detected; it was found in one preharvest jalapeño sample (detection limits: 0.0033 CFU/ml in produce and hand samples, 0.0013 CFU/ml in water, and 0.04 CFU/g in soil). Microbial indicator profiles for produce, worker hands, and soil from jalapeño and tomato farms were similar, but cantaloupe farm samples had higher indicator levels (P < 0.05 for all comparisons) on fruit (6.5, 2.8, and 7.2 log CFU per fruit) and hands (6.6, 3.1, and 7.1 log CFU per hand) for coliforms, E. coli, and Enterococcus, respectively, and lower E. coli levels in soil (<1 CFU/g). In water from tomato farms, E. coli indicators were significantly more prevalent (70 to 89% of samples were positive; P = 0.01 to 0.02), and geometric mean levels were higher (0.3 to 0.6 log CFU/100 ml) than those in cantaloupe farm water (32 to 38% of samples were positive, geometric mean <1 CFU/100 ml). Microbial indicators were present during all production steps, but prevalence and levels were generally highest at the final on-farm production step (the packing facility) (P < 0.03 for significant comparisons). The finding that microbial contamination on produce farms is influenced by produce type and production step can inform the design of effective approaches to mitigate microbial contamination.

Enteric Infections in Young Children are Associated with Environmental Enteropathy and Impaired Growth

To investigate the relationship between faecal contamination in child play spaces, enteric infections, environmental enteropathy (EE) and impaired growth among young children.

Identification of the Enzyme Responsible for N-Acetylation of Norfloxacin by Microbacterium sp. Strain 4N2-2

ABSTRACT Microbacterium sp. 4N2-2, isolated from a wastewater treatment plant, converts the antibacterial fluoroquinolone norfloxacin to N-acetylnorfloxacin and three other metabolites. Because N-acetylation results in loss of antibacterial activity, identification of the enzyme responsible is important for understanding fluoroquinolone resistance. The enzyme was identified as glutamine synthetase (GS); N-acetylnorfloxacin was produced only under conditions associated with GS expression. The GS gene (glnA) was cloned, and the protein (53 kDa) was heterologously expressed and isolated. Optimal conditions and biochemical properties (Km and V max) of purified GS were characterized; the purified enzyme was inhibited by Mn2+, Mg2+, ATP, and ADP. The contribution of GS to norfloxacin resistance was shown by using a norfloxacin-sensitive Escherichia coli strain carrying glnA derived from Microbacterium sp. 4N2-2. The GS of Microbacterium sp. 4N2-2 was shown to act as an N-acetyltransferase for norfloxacin, which produced low-level norfloxacin resistance. Structural and docking analysis identified potential binding sites for norfloxacin at the ADP binding site and for acetyl coenzyme A (acetyl-CoA) at a cleft in GS. The results suggest that environmental bacteria whose enzymes modify fluoroquinolones may be able to survive in the presence of low fluoroquinolone concentrations.

Risk factors for household transmission of vibrio cholerae in Dhaka, Bangladesh (CHoBI7 Trial)

AbstractHousehold contacts of cholera patients are at a 100 times higher risk of a Vibrio cholerae infection than the general population. To examine risk factors for V. cholerae infections and investigate intervention strategies among this population, we followed household contacts of cholera patients for the 1-week high-risk period after the index patient obtained care. This study was nested within a randomized controlled trial of the Cholera-Hospital-Based-Intervention-for-7-days (CHoBI7), a handwashing with soap and water treatment intervention in Dhaka, Bangladesh. Rectal swab results were available from 320 household contacts of cholera patients at five time points over a 1-week period. Fecal and water samples were analyzed for V. cholerae by bacterial culture. All analyses were stratified by study arm. Within the intervention arm, stored household drinking water with a median free chlorine concentration below 0.5 mg/L was associated with a three times higher odds of a cholera infection (odds ratio [OR]: 3.0; 95% confidence interval [CI]: 1.32, 6.63). In the control arm, having V. cholerae in stored water was associated with a significantly higher odds of a symptomatic cholera infection (OR: 8.66; 95% CI: 2.11, 35.48). No association was found between observed handwashing with soap at food and stool-related events and V. cholerae infections. Stored household drinking water with detectable V. cholerae and chlorine concentrations below the World Health Organization guideline were found to be important risk factors for cholera infection among household contacts of cholera patients. These findings emphasize the need for water treatment interventions targeting this high risk population.

Prevalence and associated factors of pre-hypertension and hypertension in Nepal: Analysis of the Nepal Demographic and Health Survey 2016

Hypertension is the leading risk factor for cardiovascular diseases and develops faster among pre‐hypertensive individuals. However, there is a lack of nationally representative studies that investigate the prevalence and determinants of these two conditions in many developing countries, including Nepal. This study investigates the prevalence and determinants of pre‐hypertension and hypertension in Nepal.

Rapid Dipstick Detection of Vibrio cholerae in Household Stored and Municipal Water in Dhaka, Bangladesh: CHoBI7 Trial

In urban Dhaka, Bangladesh, 30% of source water samples collected from the households of patients with cholera had detectable Vibrio cholerae. These findings indicate an urgent need for a public health intervention for this population. The Crystal VC® dipstick test is a rapid method for detecting V. cholerae in stool and water. However, to date no study has investigated the use of the rapid dipstick test for household surveillance of stored drinking water.