Microbial evaluation of sandboxes located in urban area

Vertical stratification and seasonality of fecal indicator bacteria in New York City playground sandboxes

Sandboxes in public play spaces afford a crucial opportunity for urban children to engage in naturalistic play that fosters development of cognitive, social, and motor skills. As open pits, sandboxes in New York City public playgrounds are potentially exposed to fecal inputs from various sources, including wild and domestic animals. A longitudinal study of thirteen sandboxes located in public playgrounds on the east side of Manhattan reveals ubiquity of the fecal indicator bacteria enterococci and Escherichia coli through all seasons. The highest concentrations of bacteria occur in surface sand (n = 42; mean enterococci 230 MPN/g and E. coli 182 MPN/g dry weight), with significantly lower levels at depths below the surface (n = 35; mean enterococci 21 MPN/g and E. coli 12 MPN/g dry weight), a stratification consistent with fecal loading at the surface. Generalized linear mixed models indicate that sand depth (surface vs. underlayers) is the most influential variable affecting bacterial levels (P <0.001 for both enterococci and E. coli), followed by sampling season (P <0.001 for both). Bacterial concentrations do not vary significantly as a function of playground location or ZIP code within the study area. Children's exposure while playing in sandboxes likely reaches 105 enterococci and 104E. coli in a typical play period. Microbial source tracking to identify fecal hosts reveals dog, bird, and human biomarkers in low concentrations. Open sandbox microcosms installed at ground level in the urban environment of Manhattan are fouled by enterococci and E. coli within two weeks, while adjacent closed microcosms exhibit no fecal contamination over a 33-day sampling period. Collectively, our results indicate that increasing the frequency of sand refills and covering sandboxes during times of disuse would be straightforward management strategies to mitigate fecal contamination in playground sandboxes.

Potential use of high-throughput sequencing of bacterial communities for postmortem submersion interval estimation

Microorganisms play vital roles in the natural decomposition of carcasses in aquatic systems. Using high-throughput sequencing techniques, we evaluated the composition and succession of microbial communities throughout the decomposition of rat carcasses in freshwater. A total of 4,428,781 high-quality 16S rRNA gene sequences and 2144 operational taxonomic units were obtained. Further analysis revealed that the microbial composition differed significantly between the epinecrotic (rat skins) and the epilithic (rocks) samples. During the carcass decomposition process, Proteobacteria became the dominant phylum in the epinecrotic, epilithic, and environmental (water) samples, followed by Firmicutes in the epinecrotic samples and Bacteroidetes in the epilithic and water samples. Microbial communities were influenced by numerous environmental factors, such as dissolved oxygen content and conductivity. Our study provides new insight about postmortem submersion interval (PMSI) estimation in aquatic environments.

Recreational sandboxes for children and dogs can be a source of epidemic ribotypes of Clostridium difficile

Different studies have suggested that the sand of public playgrounds could have a role in the transmission of infections, particularly in children. Furthermore, free access of pets and other animals to the playgrounds might increase such a risk. We studied the presence of Clostridium difficile in 20 pairs of sandboxes for children and dogs located in different playgrounds within the Madrid region (Spain). Clostridium difficile isolation was performed by enrichment and selective culture procedures. The genetic (ribotype and amplified fragment length polymorphism [AFLP]) diversity and antibiotic susceptibility of isolates was also studied. Overall, 52.5% (21/40) of samples were positive for the presence of C. difficile. Eight of the 20 available isolates belonged to the toxigenic ribotypes 014 (n = 5) and 106 (n = 2), both regarded as epidemic, and CD047 (n = 1). The other 12 isolates were non-toxigenic, and belonged to ribotypes 009 (n = 5), 039 (n = 4), and 067, 151 and CD048 (one isolate each). Nevertheless, all isolates (even those of a same ribotype) were classified into different AFLP genotypes indicating non-relatedness. In conclusion, our results revealed the presence of epidemic ribotypes of C. difficile in children's and dog's sandboxes located nearby, which constitutes a major health risk.