Incidence of and risk factors for surgical site infection after colorectal surgery: A multiple-center prospective study of 3,663 consecutive patients in China.

BACKGROUND: Surgical site infection (SSI) after colorectal surgery (CRS) remains a significant problem for its negative clinical outcomes. However, it is poorly understood in China. This study aims to investigate the incidence, risk factors and microbiology of SSI after CRS. METHODS: A nationwide prospective multicenter design was applied. Patients in 19 Chinese hospitals from 2015 to 2018 were prospectively monitored for SSI after CRS. Demographic data, hospital characteristics, and potential perioperative risk factors were collected and analyzed, using univariate and multivariate logistic regression models. RESULTS: Among 3,663 study participants, 134(3.66%) episodes of SSI were identified. The incidence rate of SSI decreased from 5.9 infections per 100 procedures in 2015 to 3.1 infections per 100 procedures in 2018 (incidence rate ratio, 0.52; 95% CI, 0.28-0.94). The SSI rates were 1.88, 4.15, 6.27 and 11.58 per 100 operations for the National Nosocomial Infections Surveillance system (NNIS) risk index categories of 0, 1, and 2 or 3, respectively. Escherichia coli (54/134, 40.3%) and Klebsiella pneumoniae (10/134, 7.5%) were the most frequently isolated microorganisms. A high prevalence of antibiotic resistance were observed in our study, with rates of extended spectrum beta-lactamase-producing or carbapenem-resistant Escherichia coli and Klebsiella pneumonia of 50.0%(27/54) and 30.0%(3/10) respectively. Preoperative hospital stay ≥ 48h (OR=2.28, 95% CI: 1.03-5.02, P=0.042) and contaminated or dirty wound (OR=3.38, 95% CI: 1.88-6.06, P=4.50×10-5) were significantly associated with increasing risk of SSI after CRS. CONCLUSION: A statistically significant but modest decrease in the incidence rate of CRS SSI over the 4-year study period was observed in this study. Noticeably, the relatively high rates of multidrug-resistant pathogens causing SSI after CRS should be alert, while more studies with large population are needed due to the small number of isolates identified in our survey.

Intranasal immunization with autolysin (LytA) in mice model induced protection against five prevalent Streptococcus pneumoniae serotypes in China.

In order to evaluate immunogenicity and protective efficacy of LytA from Streptococcus pneumoniae, we subcloned the full-length lytA-encoded autolysin (LytA) from 5 major pathogenic serotype isolates in China and obtained purified rLytA. Bioinformatics analysis showed that sequences of LytA were highly conserved in all strains we used in this work, and western blot analysis demonstrated that rLytAs from heterogeneous serotypes were cross-recognized by serum of mice infected with 23F strain SH137. Mice were intranasally immunized with purified rLytA, and serum anti-rLytA IgG, IgA and secretory IgA were elicited. More importantly, rLytA intranasal-immunized mice showed a significantly higher survival rate and lower bacterial carriage in response to infection by Streptococcus pneumoniae. The fact that mice immunized with rLytA from strain SH137 also had a higher survival rate after intraperitoneal injection of other four serotype strains of living S. pneumoniae suggested that it possessed cross-protection effect. Our study revealed that intranasal immunization with rLytA may protect mice against mucosal and systemic pneumococcal infection; hence, it was an attractive vaccine candidate.