Evolution of Resistance to a Last-Resort Antibiotic in Staphylococcus aureus via Bacterial Competition

• Published in: Cell 2014-08, Vol.158 (5), p.1060-1071
• Main Authors: Koch, Gudrun, Yepes, Ana, Förstner, Konrad U., Wermser, Charlotte, Stengel, Stephanie T., Modamio, Jennifer, Ohlsen, Knut, Foster, Kevin R., Lopez, Daniel
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Anti-Bacterial Agents - pharmacology; Bacteriocins - genetics; Bacteriocins - metabolism; Biofilms - drug effects; Biological Evolution; Female; Methicillin-Resistant Staphylococcus aureus - classification; Methicillin-Resistant Staphylococcus aureus - drug effects; Methicillin-Resistant Staphylococcus aureus - genetics; Methicillin-Resistant Staphylococcus aureus - physiology; Mice, Inbred BALB C; Microbiological Phenomena; Molecular Sequence Data; Pigmentation; Sequence Alignment; Staphylococcal Infections - drug therapy; Staphylococcal Infections - microbiology; Staphylococcus aureus - classification; Staphylococcus aureus - drug effects; Staphylococcus aureus - genetics; Staphylococcus aureus - physiology; Vancomycin - pharmacology
• ISSN: 0092-8674; 1097-4172
• DOI: 10.1016/j.cell.2014.06.046

Antibiotic resistance is a key medical concern, with antibiotic use likely being an important cause. However, here we describe an alternative route to clinically relevant antibiotic resistance that occurs solely due to competitive interactions among bacterial cells. We consistently observe that isolates of Methicillin-resistant Staphylococcus aureus diversify spontaneously into two distinct, sequentially arising strains. The first evolved strain outgrows the parent strain via secretion of surfactants and a toxic bacteriocin. The second is resistant to the bacteriocin. Importantly, this second strain is also resistant to intermediate levels of vancomycin. This so-called VISA (vancomycin-intermediate S. aureus) phenotype is seen in many hard-to-treat clinical isolates. This strain diversification also occurs during in vivo infection in a mouse model, which is consistent with the fact that both coevolved phenotypes resemble strains commonly found in clinic. Our study shows how competition between coevolving bacterial strains can generate antibiotic resistance and recapitulate key clinical phenotypes. [Display omitted] •Biofilm competition leads MRSA to evolve new strains•New strains resemble clinically relevant multi-drug-resistant isolates•In vivo experiments show similar strain diversification pattern•Biofilm evolution generates antibiotic resistance in the absence of antibiotic Resistance to vancomycin can occur in S. aureus as a result of evolution and competition within the bacterial strain and in the absence of vancomycin. This selection occurs both in vitro and within a mouse infection model.