Monday micro – evolution in action!

By Siouxsie Wiles 16/12/2013

This week’s Monday Micro is all about microbial adaptation, with two interesting new papers just out. The first relates to the H7N9 strain of bird flu that appeared in China earlier this year; as of the most recent WHO report there have been 137 lab confirmed cases with 45 deaths. There is currently no vaccine available against H7N9, so patients are treated with antiviral agents like oseltamivir (Tamiflu). During the outbreak in China, strains of H7N9 emerged which had become resistant to oseltamivir by changing their neuraminidase gene.

Rong Hai and colleagues (1) studied strains of H7N9 with a particular neuraminidase mutation, known as NA-R292K and found that this mutation led to high levels of resistance to oseltamivir and another antiviral agant peramivir, as well as partial resistance to zanamivir. But they also found something more disturbing. When seasonal strains of flu become highly resistant to antivirals, this happens at a cost, and they become less able to replicate and spread between hosts. But this might not be the case for these H7N9 mutants. Instead they were as able as the unmutated H7N9 strain to replicate inside human respiratory cells in the lab, could cause disease in mice, and could transmit from infected to uninfected guinea pigs. Scary.

The second paper, published in PLOS Pathogens shows how quickly a friend can be turned into a foe (2). Migla Miskinyte and colleagues took a commensal strain of E. coli and passaged it through macrophages for 30 days. Macrophages are one of the workhorses of our immune system, responsible for gobbling up bacteria and killing them. Within just 30 days, clones of E. coli evolved that could escape being destroyed by macrophages, and these were found to be more able to cause disease in mice.

Monday Micro will be taking a break over the festive season. Hope you all have a great one, whatever your belief system or lack thereof. I’ll leave you with the lovely Rebecca Watson, reminding you why you shouldn’t give your money to the Salvation Army. Feel free to donate to a charity that supports equality. Or become someone’s patron and help them make cool stuff. Happy holidays!


1. Hai R, Schmolke M, Leyva-Grado VH, Thangavel RR, Margine I, Jaffe EL, Krammer F, Solórzano A, García-Sastre A, Palese P, Bouvier NM. Influenza A(H7N9) virus gains neuraminidase inhibitor resistance without loss of in vivo virulence or transmissibility. Nature Communications, 2013; 4 DOI: 10.1038/ncomms3854

2. Miskinyte M, Sousa A, Ramiro RS, de Sousa JAM, Kotlinowski J, et al. (2013) The Genetic Basis of Escherichia coli Pathoadaptation to Macrophages. PLoS Pathog 9(12): e1003802. doi:10.1371/journal.ppat.1003802