7% for MM, and 6.2% for control arm, followed by H. influenzae type B; 2%, 3.7%, and 5% respectively

(data not shown). These differences were statistically significant across all three arms. B. pertussis was also detected in three HCWs. In a multivariable cluster adjusted log binomial model, when compared to the control group, the N95 group was significantly protective against bacterial colonization (Table 2). We MLN8237 cell line demonstrated 59% efficacy of N95 respirators against any co-infection (Table 3), and 67% against bacterial and viral co-infection (Table 4) in adjusted multivariate analyses. The only other significant variable for bacterial infection and bacterial and viral co-infection was the respiratory ward, which significantly increased the risk of colonization or co-infection

compared to other wards (Table 2 and Table 4). In addition, univariable CHIR-99021 in vivo analyses of infection and co-infection rates by other factors, such as, smoking (current vs non-smoker), staff type (doctor vs nurses) and ward type (respiratory vs other) were conducted in the analysis. For bacterial infection, HCWs working in a respiratory ward were significantly at higher risk of infection than HCWs in other wards (7.3% vs 3.5%, p < 0.001). For bacterial co-infection, nurses had a significantly higher risk than doctors (3.2% vs 1.4%, p = 0.02) and the rate was also significantly higher in respiratory wards (4.4% vs 1.8%, p = 0.001). Respiratory wards had a higher rate of bacteria–virus co-infection than other wards (2.5% vs 1%, p = 0.02). We have previously shown that N95 respirators protect against clinical respiratory illness (MacIntyre et al., 2011 and Macintyre et al., 2013). N95 respirators, but not medical masks, were significantly protective against bacterial colonization, co-colonization, Mephenoxalone viral-bacterial co-infection and dual virus infection in HCWs. We also showed a statistically significant decrease in rates of bacterial respiratory colonization with increasing levels of respiratory protection. The lowest rates were in the

N95 group, followed by the medical mask group, and the highest rates were in HCWs who did not wear a mask. Although the clinical significance of this finding is unknown in terms of the implications for HCWs, we have shown that such colonization can be prevented by the use of N95 respirators. These findings are consistent with other work we have published, which shows a reduction in bacterial colonization following use of N95 respirators (MacIntyre et al., 2013). While the role of nosocomial viral respiratory infections is accepted, bacterial infections are less well understood. Our findings suggest that bacterial respiratory tract colonization or infection in HCWs should be studied further. Bacterial colonization may be a precursor to viral and bacterial co-infections and invasive bacterial infections in individuals with influenza or other respiratory viral infections.