A number of gut microbe species like Bifidobacterium adolescentis are affected by even a single course of broad-spectrum antibiotics.
T MICROBIOME
his year scientists continued to unravel the complicated ties between human health and the thousands of microbial strains living on and inside our bodies. These microbes have evolved with humans for millennia and have been considered benign, if not helpful, to us. But as researchers at the University of Sheffield discovered, that’s not always the case. The team found that a noninfectious strain of skin bacteria called Micrococcus luteus promotes development of pathogenic Staphylococcus aureus infections in mice (Nat. Microbiol. 2018, DOI: 10.1038/ s41564-018-0198-3). What’s most interesting, says Trinity College Dublin’s Rachel M. McLoughlin, who wasn’t involved in the study, is that even dead M. luteus cells promoted infection, which means that dying, antibiotic-susceptible bacteria may actually help antibiotic-resistant bacteria survive. M. luteus’s betrayal aside, many bacteria strains are still beneficial, especially in the gut. Several studies showed that disrupting this microbial community could have negative effects on our health. One major disturbance comes from our use of antibiotics. A small study in humans reported that after a single course of treatment, several bacterial species in
More microbiome– human health connections found Antibiotics and moving to a new country affect our gut bacteria, and some of our microbial friends help pathogens 36
C&EN | CEN.ACS.ORG | DECEMBER 10/17, 2018
the gut did not return even after about six months (Nat. Microbiol. 2018, DOI: 10.1038/ s41564-018-0257-9). Another study, this one in mice, revealed that the antibiotic-triggered loss of some gut microbes messed with immune cells called macrophages and that this disruption could cause inflammatory conditions (Sci. Transl. Med. 2018, DOI: 10.1126/scitranslmed. aao4755). In both studies, the same strain of bacteria, called Bifidobacteria, went missing after the antibiotic treatment. Scientists also learned how moving to a new country can affect gut microbes. In one study, members of two communities who emigrated from Southeast Asia to the US experienced a decrease in gut microbe diversity, losing many of their native strains and picking up other US-associated strains, though not as many as they lost. This change in microbiome diversity may predispose the immigrants to obesity and other metabolic disorders (Cell 2018, DOI: 10.1016/j.cell.2018.10.029). The team proposed that diet affected the composition of the immigrants’ microbiomes but suspect other causes also play a role. Dan Knights, a microbiologist at the University of Minnesota who led the study, says the researchers are starting to dissect those possible contributing factors. They’re also studying whether the microbiome change can directly contribute to certain disorders. “We’re just at the opening stages of understanding exactly which microbes matter in different diseases, but it’s very clear that having the wrong overall community of microbes can contribute to a wide range of human diseases,” Knights says.—TIEN NGUYEN
C R E D I T: S C I MAT/ S C I EN C E S O URCE
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YEAR IN CHEMISTRY
