Molecular characterisation and epidemiology of transmission of intraoperative Staphylococcus aureus isolates stratified by vancomycin minimum inhibitory concentration (MIC).

Background: Reduced vancomycin susceptibility in Staphylococcus aureus (S. aureus) is considered a more pathogenic strain characteristic and is associated with treatment failure. We aimed to characterise the epidemiology of intraoperative transmission of S. aureus isolates with reduced vancomycin susceptibility. Methods: S. aureus isolates (N=173) collected from 274 randomly selected operating room environments at three major academic medical centres in 2009-2010 were characterised by vancomycin minimum inhibitory concentration (MIC). We aimed to characterise the transmission dynamics for VISA and isolates with relatively reduced vancomycin (MIC= 2µg/mL) susceptibility at the range of therapeutic differentiation. Results: Intraoperative S. aureus MIC was 1.38 ± 0.34 µg/mL. No VISA isolates were identified (95% upper confidence limit 2.1%) and those with an MIC of 2 µg/mL accounted for 12.72% (22/173) of all isolates. MIC=2 µg/mL isolates were more frequently cultured from the hands of healthcare providers [19.3% (16/83)] versus otherwise [6.7% (6/90)], with unadjusted risk ratio 2.89, P=0.021, and from patients with >2 major comorbidities [25.0% (8/32)] versus otherwise [9.9% (14/141)], with unadjusted risk ratio 2.52, P=0.035. Both were significant when tested simultaneously. The adjusted relative risk for provider hands was 2.77 (95% CI 1.15 to 6.69, P=0.024). The adjusted relative risk for patients with >2 major comorbidities was 2.37 (95% CI 1.11 to 5.05, P=0.026). MIC=2µg/mL was not associated with greater risk of clonal transmission (unadjusted P=0.34, adjusted P=0.18). Conclusion: Intraoperative VISA is a rare event. S. aureus isolates MIC=2µg/mL isolates were not associated with increased risk of intraoperative transmission. The epidemiology of detected intraoperative transmission is consistent with Centers for Disease Control guidelines.

Effectiveness and feasibility of an evidence-based intraoperative infection control program targeting improved basic measures: a post-implementation prospective case-cohort study.

STUDY OBJECTIVE: A randomized controlled study demonstrated that an optimized intraoperative infection control program targeting basic preventive measures can reduce Staphylococcus aureus transmission and surgical site infections. In this study we address potential limitations of operating room heterogeneity of infections and compliance with behavioral interventions following adoption into clinical practice. DESIGN: A post-implementation prospective case-cohort study. SETTING: Twenty-three operating rooms at a large teaching hospital. PATIENTS: A total of 801 surgical patients [425 (53%) women; 350 (44%) ASA > 2, age 54.6 ± 15.9 years] were analyzed for the primary and 804 for the secondary outcomes. INTERVENTIONS: A multifaceted, evidence-based intraoperative infection control program involving hand hygiene, vascular care, and environmental cleaning improvements was implemented for 23 operating room environments. Bacterial transmission monitoring was used to provide monthly feedback for intervention optimization. MEASUREMENTS: S. aureus transmission (primary) and surgical site infection (secondary). MATERIALS AND METHODS: The incidence of S. aureus transmission and surgical site infection before (3.5 months) and after (4.5 months) infection control optimization was assessed. Optimization was defined by a sustained reduction in anesthesia work area bacterial reservoir isolate counts. Poisson regression with robust error variances was used to estimate the incidence risk ratio (IRR) of intraoperative S. aureus transmission and surgical site infection for the independent variable of optimization. MAIN RESULTS: Optimization was associated with decreased S. aureus transmission [24% before (85/357) to 9% after (42/444), IRR 0.39, 95% CI 0.28 to 0.56, P < .001] and surgical site infections [8% before (29/360) and 3% after (15/444) (IRR 0.42, 95% CI 0.23 to 0.77, P = .005; adjusted for American Society of Anesthesiologists' physical status, aIRR 0.45, 95% CI 0.25 to 0.82, P = .009]. CONCLUSION: An optimized intraoperative infection control program targeting improvements in basic preventive measures is an effective and feasible approach for reducing S. aureus transmission and surgical site infection development.

Operating room PathTrac analysis of current intraoperative Staphylococcus aureus transmission dynamics.

BACKGROUND: Operating room (OR) reservoir Staphylococcus aureus isolates have been linked to 50% of surgical site infections. We aimed to assess S aureus transmission dynamics in today's ORs to further guide health care-associated infection prevention. METHODS: Forty OR case-pairs were randomly selected for observation in a 5-month prospective cohort study. Case-pair S aureus transmission dynamics were mapped using OR PathTrac. RESULTS: S aureus pathogens were isolated from ≥1 OR reservoirs in 45.7% (37 of 81) of surgical cases, and epidemiologically related transmission events were confirmed in 22.5% (9 of 40) of case-pairs. Patient skin sites and provider hands provided comparable risk of OR S aureus exposure (19 of 481 patient vs 35 of 1,173 provider hands, relative risk [RR], 1.32; 95% confidence interval [CI], 0.77-2.29; P = .32). Environmental contamination at case 2 start was higher than at case 1 start (case 2 start 32 of 152 sites with >20 colony-forming units vs case 1 start 7 of 163 sites with >20 colony-forming units; RR, 4.90; 95% CI, 2.23-10.77; P < .0001). The stopcock contamination rate was not significantly different than our prior study in 2008 (19 of 164 2008 vs 8 of 77 2018; RR, 1.12; 95% CI, 0.51-2.43; P = .78). All epidemiologically related transmission events involved the between-case mode of transmission and phenotype H. CONCLUSIONS: Current OR S aureus exposure threats reliably include patient skin sites and provider hands. Perioperative S aureus preventive measures should extend from patient decolonization to include improved hand decontamination efforts.

High-risk Staphylococcus aureus transmission in the operating room: A call for widespread improvements in perioperative hand hygiene and patient decolonization practices.

BACKGROUND: Increased awareness of the epidemiology of transmission of pathogenic bacterial strain characteristics may help to improve compliance with intraoperative infection control measures. Our aim was to characterize the epidemiology of intraoperative transmission of high-risk Staphylococcus aureus sequence types (STs). METHODS: S aureus isolates collected from 3 academic medical centers underwent whole cell genome analysis, analytical profile indexing, and biofilm absorbance. Transmission dynamics for hypertransmissible, strong biofilm-forming, antibiotic-resistant, and virulent STs were assessed. RESULTS: S aureus ST 5 was associated with increased risk of transmission (adjusted incidence risk ratio, 6.67; 95% confidence interval [CI], 1.82-24.41; P = .0008), greater biofilm absorbance (ST 5 median absorbance ± SD, 3.08 ± 0.642 vs other ST median absorbance ± SD, 2.38 ± 1.01; corrected P = .021), multidrug resistance (odds ratio, 7.82; 95% CI, 2.19-27.95; P = .002), and infection (6/38 ST 5 vs 6/140 STs; relative risk, 3.68; 95% CI, 1.26-10.78; P = .022). Provider hands (n = 3) and patients (n = 4) were confirmed sources of ST 5 transmission. Transmission locations included provider hands (n = 3), patient skin sites (n = 4), and environmental surfaces (n = 2). All observed transmission stories involved the within-case mode of transmission. Two of the ST 5 transmission events were directly linked to infection. CONCLUSIONS: Intraoperative S aureus ST 5 isolates are hypertransmissible and pathogenic. Improved compliance with hand hygiene and patient decolonization may help to control the spread of these dangerous pathogens.

Methicillin-resistant Staphylococcus aureus has greater risk of transmission in the operating room than methicillin-sensitive S aureus.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is a pathogenic S aureus strain characteristic associated with increased patient morbidity and mortality. The health care system needs to understand MRSA transmissibility in all settings to improve basic preventive measures to generate sustained reductions in invasive MRSA infections. Our primary aim was to compare intraoperative transmissibility of MRSA versus methicillin-sensitive S aureus (MSSA) isolates. METHODS: S aureus isolates (N = 173) collected from 274 randomly selected operating room environments (first and second case of the day in each operating room, a case pair) at 3 hospitals underwent systematic-phenotypic and genomic processing to identify clonally related transmission events. Confirmed transmission events were defined as at least 2 S aureus isolates obtained from ≥2 distinct intraoperative reservoirs sampled within or between cases in a study unit that were epidemiologically and clonally related. We explored the relationship between clonal transmission and methicillin resistance with Poisson regression analysis. RESULTS: We identified 58 clonal transmission events. MRSA isolates were associated with increased risk of clonal transmission compared with MSSA isolates (adjusted incidence risk ratio [IRR], 1.68; 95% confidence interval [CI], 1.13-2.49; P = .010; unadjusted IRR, 1.85; 95% CI, 1.23-2.77; P = .003, respectively). CONCLUSIONS: MRSA isolates are associated with increased risk of intraoperative transmission. Future work should examine the impact of the attenuation of intraoperative MRSA transmission on the incidence of invasive MRSA infections.