Transmission of Staphylococcus aureus from Humans to Green Monkeys in The Gambia as Revealed by Whole-Genome Sequencing.

UNLABELLED: Staphylococcus aureus is an important pathogen of humans and animals. We genome sequenced 90 S. aureus isolates from The Gambia: 46 isolates from invasive disease in humans, 13 human carriage isolates, and 31 monkey carriage isolates. We inferred multiple anthroponotic transmissions of S. aureus from humans to green monkeys (Chlorocebus sabaeus) in The Gambia over different time scales. We report a novel monkey-associated clade of S. aureus that emerged from a human-to-monkey switch estimated to have occurred 2,700 years ago. Adaptation of this lineage to the monkey host is accompanied by the loss of phage-carrying genes that are known to play an important role in human colonization. We also report recent anthroponotic transmission of the well-characterized human lineages sequence type 6 (ST6) and ST15 to monkeys, probably because of steadily increasing encroachment of humans into the monkeys' habitat. Although we have found no evidence of transmission of S. aureus from monkeys to humans, as the two species come into ever-closer contact, there might be an increased risk of additional interspecies exchanges of potential pathogens. IMPORTANCE: The population structures of Staphylococcus aureus in humans and monkeys in sub-Saharan Africa have been previously described using multilocus sequence typing (MLST). However, these data lack the power to accurately infer details regarding the origin and maintenance of new adaptive lineages. Here, we describe the use of whole-genome sequencing to detect transmission of S. aureus between humans and nonhuman primates and to document the genetic changes accompanying host adaptation. We note that human-to-monkey switches tend to be more common than the reverse and that a novel monkey-associated clade is likely to have emerged from such a switch approximately 2,700 years ago. Moreover, analysis of the accessory genome provides important clues as to the genetic changes underpinning host adaptation and, in particular, shows that human-to-monkey switches tend to be associated with the loss of genes known to confer adaptation to the human host.

Development and assessment of molecular diagnostic tests for 15 enteropathogens causing childhood diarrhoea: a multicentre study.

BACKGROUND: Childhood diarrhoea can be caused by many pathogens that are difficult to assay in the laboratory. Molecular diagnostic techniques provide a uniform method to detect and quantify candidate enteropathogens. We aimed to develop and assess molecular tests for identification of enteropathogens and their association with disease. METHODS: We developed and assessed molecular diagnostic tests for 15 enteropathogens across three platforms-PCR-Luminex, multiplex real-time PCR, and TaqMan array card-at five laboratories worldwide. We judged the analytical and clinical performance of these molecular techniques against comparator methods (bacterial culture, ELISA, and PCR) using 867 diarrhoeal and 619 non-diarrhoeal stool specimens. We also measured molecular quantities of pathogens to predict the association with diarrhoea, by univariate logistic regression analysis. FINDINGS: The molecular tests showed very good analytical and clinical performance at all five laboratories. Comparator methods had limited sensitivity compared with the molecular techniques (20-85% depending on the target) but good specificity (median 97·3%, IQR 96·5-98·9; mean 95·2%, SD 9·1). Positive samples by comparator methods usually had higher molecular quantities of pathogens than did negative samples, across almost all platforms and for most pathogens (p<0·05). The odds ratio for diarrhoea at a given quantity (measured by quantification cycle, Cq) showed that for most pathogens associated with diarrhoea-including Campylobacter jejuni and Campylobacter coli, Cryptosporidium spp, enteropathogenic Escherichia coli, heat-stable enterotoxigenic E coli, rotavirus, Shigella spp and enteroinvasive E coli, and Vibrio cholerae-the strength of association with diarrhoea increased at higher pathogen loads. For example, Shigella spp at a Cq range of 15-20 had an odds ratio of 8·0 (p<0·0001), but at a Cq range of 25-30 the odds ratio fell to 1·7 (p=0·043). INTERPRETATION: Molecular diagnostic tests can be implemented successfully and with fidelity across laboratories around the world. In the case of diarrhoea, these techniques can detect pathogens with high sensitivity and ascribe diarrhoeal associations based on quantification, including in mixed infections, providing rich and unprecedented measurements of infectious causes. FUNDING: Bill & Melinda Gates Foundation Next Generation Molecular Diagnostics Project.

Activity of aspirin analogues and vanillin in a human colorectal cancer cell line.

Colorectal cancer is the third most common cancer and is associated with significant morbidity and mortality. Epidemiological and animal studies indicate that regular acetylsalicylic acid (aspirin) intake is associated with a reduction in the incidence of colorectal cancer. Acetylsalicylic acid (ASA) has also been shown to inhibit colorectal cancer cell proliferation in vitro. The molecular basis for this specific cytotoxicity is an area of considerable debate. To investigate the toxicity of salicylates, the sensitivity of the DNA mismatch repair proficient SW480 human colorectal cancer cell line to four categories of compounds with varying degrees of structural similarity to acetylsalicylic acid was tested. These compounds were: i) salicylic acid analogues with substituents at the 5-position; ii) ASA analogues with extended chain lengths in the acyl group; iii) vanillin (4-hydroxy-3-methoxybenzaldehyde; and iv) bis(2-carboxyphenyl) succinate (BCS) and structurally similar derivatives thereof. It was found that compounds with amino and acetamido substituents at the salicylate 5-position were less toxic than ASA itself. Modifications to the length of the hydrocarbon chain in the acyl groups of ASA analogues also marginally reduced toxicity. Vanillin exhibited relatively limited toxicity against the SW480 colorectal cancer cell line. Commercially available and in-house synthesised BCS (diaspirin) were notably more inhibitory to cell growth than ASA itself, yet retained substantial specificity against colorectal cancer cell lines vs. non-colorectal cancer cell lines. BCS and ASA were toxic to SW480 cells through initiation of necrotic and apoptotic pathways. Fumaroyldiaspirin and benzoylaspirin exhibited greater toxicity than ASA against the SW480 cell line. A novel method for synthesis of BCS, a compound that has erratic commercial availability, is described. We propose that the anti-inflammatory and anticancer capacity of BCS and the other analogues described herein is worthy of investigation.