Use of metagenomic microbial source tracking to investigate the source of a foodborne outbreak of cryptosporidiosis

Cryptosporidium is a protozoan parasite of global public health importance that causes gastroenteritis in a variety of vertebrate hosts, with many human outbreaks reported yearly, often from ingestion of contaminated water or food. Despite the major public health implications, little is typically known about sources of contamination of disease outbreaks caused by Cryptosporidium. Here, we study a national foodborne outbreak resulted from infection with Cryptosporidium parvum via romaine lettuce, with the main goal to trace the source of the parasite. To do so, we combined traditional outbreak investigation methods with molecular detection and characterization methods (i.e. PCR based typing, amplicon and shotgun sequencing) of romaine lettuce samples collected at the same farm from which the contaminated food was produced. Using 18S rRNA typing, we detected C. parvum in two out of three lettuce samples, which was supported by detections in the metagenome analysis. Microbial source tracking analysis of the lettuce samples suggested sewage water as a likely source of the contamination, albeit with some uncertainty. In addition, the high degree of overlap in bacterial species content with a public human gut microbial database corroborated the source tracking results. The combination of traditional and molecular based methods applied here is a promising tool for future source tracking investigations of food- and waterborne outbreaks of Cryptosporidium spp. and can help to control and mitigate contamination risks.

Bactericidal antisense effects of peptide-PNA conjugates

Antisense peptide nucleic acids (PNAs) can specifically inhibit Escherichia coli gene expression and growth and hold promise as anti-infective agents and as tools for microbial functional genomics. Here we demonstrate that chemical modification improves the potency of standard PNAs. We show that 9- to 12-mer PNAs, especially when attached to the cell wall/membrane-active peptide KFFKFFKFFK, provide improvements in antisense potency in E. coli amounting to two orders of magnitude while retaining target specificity. Peptide-PNA conjugates targeted to ribosomal RNA (rRNA) and to messenger RNA (mRNA) encoding the essential fatty acid biosynthesis protein Acp prevented cell growth. The anti-acpP PNA at 2 microM concentration cured HeLa cell cultures noninvasively infected with E. coli K12 without any apparent toxicity to the human cells. These results indicate that peptides can be used to carry antisense PNA agents into bacteria. Such peptide-PNA conjugates open exciting possibilities for anti-infective drug development and provide new tools for microbial genetics.