Prophage-encoded methyltransferase drives adaptation of community-acquired methicillin-resistant Staphylococcus aureus
Robert J. Ulrich, Magdalena Podkowik, Rebecca Tierce, Irnov Irnov, Gregory Putzel, Nora M. Samhadaneh, Keenan A. Lacey, Daiane Boff, Sabrina M. Morales, Sohei Makita, Theodora K. Karagounis, Erin E. Zwack, Chunyi Zhou, Randie H. Kim, Karl Drlica, Alejandro Pironti, Harm van Bakel, Victor J. Torres, Bo Shopsin
Robert J. Ulrich, Magdalena Podkowik, Rebecca Tierce, Irnov Irnov, Gregory Putzel, Nora M. Samhadaneh, Keenan A. Lacey, Daiane Boff, Sabrina M. Morales, Sohei Makita, Theodora K. Karagounis, Erin E. Zwack, Chunyi Zhou, Randie H. Kim, Karl Drlica, Alejandro Pironti, Harm van Bakel, Victor J. Torres, Bo Shopsin
View: Text | PDF
Research Article Infectious disease Microbiology

Prophage-encoded methyltransferase drives adaptation of community-acquired methicillin-resistant Staphylococcus aureus

Abstract

We recently described the evolution of a community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) USA300 variant responsible for an outbreak of skin and soft tissue infections. Acquisition of a mosaic version of the Φ11 prophage (mΦ11) that increases skin abscess size was an early step in CA-MRSA adaptation that primed the successful spread of the clone. The present study shows how prophage mΦ11 exerts its effect on virulence for skin infection without encoding known toxin or fitness genes. Abscess size and skin inflammation were associated with DNA methylase activity of an mΦ11-encoded adenine methyltransferase (designated pamA). pamA increased expression of fibronectin-binding protein A (fnbA; FnBPA), and inactivation of fnbA eliminated the effect of pamA on abscess virulence without affecting strains lacking pamA. Thus, fnbA is a pamA-specific virulence factor. Mechanistically, pamA was shown to promote biofilm formation in vivo in skin abscesses, a phenotype linked to FnBPA’s role in biofilm formation. Collectively, these data reveal a critical mechanism — epigenetic regulation of staphylococcal gene expression — by which phage can regulate virulence to drive adaptive leaps by S. aureus.

Authors

Robert J. Ulrich, Magdalena Podkowik, Rebecca Tierce, Irnov Irnov, Gregory Putzel, Nora M. Samhadaneh, Keenan A. Lacey, Daiane Boff, Sabrina M. Morales, Sohei Makita, Theodora K. Karagounis, Erin E. Zwack, Chunyi Zhou, Randie H. Kim, Karl Drlica, Alejandro Pironti, Harm van Bakel, Victor J. Torres, Bo Shopsin

×

Figure 3

pamA increases skin abscess size and inflammation in the absence of mΦ11.

Options: View larger image (or click on image) Download as PowerPoint
pamA increases skin abscess size and inflammation in the absence of mΦ1...
(A) Effect of pamA on skin abscess size. Abscess area at the indicated times after infection with approximately 1 × 107 bacterial CFU of LAC* with empty vector (EV) (maroon, n = 50 abscesses, strain RU129) or constitutively expressed pamA (purple, n = 50 abscesses, strain RU121) integrated into the chromosome in single copy. Data are pooled from 4 independent experiments and represent mean ± SD. Statistical significance was determined by Mann-Whitney test, ****P ≤ 0.0001. (B) Effect of pamA on CFU recovered from skin abscesses. Skin abscesses (n = 25 abscesses per strain) from 2 independent infections in A were harvested at 72 hours and CFU enumerated. Data represent mean ± SD. Statistical significance determined by Mann-Whitney test. (C) Effect of pamA on skin inflammation. Biopsies of skin abscess (n = 15 per strain, pooled from 2 independent experiments) 72 hours after infection with LAC* containing pamA (strain RU121) or EV control (strain RU129) were H&E stained and inflammatory burden was graded by a blinded dermatopathologist. Statistical significance determined by χ2 test (P = 0.0014). (D) Representative images of skin abscess biopsies from C. One image from each strain is presented according to dermatopathologist architecture classification as nodular (above) or diffuse (below). (E) Effect of pamA on local proinflammatory and vascular proliferation cytokines. Skin abscess biopsies from 3 independent experiments of LAC* with pamA (n = 24 abscesses, strain RU121) or EV control (n = 22 abscesses, strain RU129) were homogenized, and levels of the indicated cytokines were measured. Data represent mean ± SD. Statistical significance was determined by Mann-Whitney test, **P ≤ 0.01, ***P ≤ 0.001, ****P ≤ 0.0001.