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Introduction Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) that causes coronavirus disease 2019 (COVID-19) is highly contagious, with a potential to cause large nosocomial outbreaks in the hospital setting. We report the advance deployment of comprehensive, multi-level infection control measures in a 3,700-bed large hospital to prevent nosocomial outbreaks of COVID-19 during the pandemic. Methods We implemented a series of dynamic infection control policies during the pandemic. A confirmed COVID-19 Case was defined by positive real-time reverse transcriptase–polymerase chain reaction (RT-PCR) assay. All healthcare worker (HCW) having symptoms or close contact with the confirmed case received the RT-PCR test. Results A total of 5,722 patients were tested in our hospital from January to May 2020. Twenty-five patients were confirmed COVID-19, including two inpatients. A cluster of 4 HCWs with COVID-19 associated with the 2nd inpatient was identified in the early stage of epidemic. Our enhanced traffic control bundling, mask wearing, hand hygiene and environmental cleaning were reinforced after the outbreak. All other confirmed cases were identified at our outdoor quarantine station or epidemic clinic afterwards, and the results of testing for 146 symptomatic HCWs were all negative. Conclusions Integrated teamwork, advance deployment of infection control measures and efficient diagnostic testing and response protected HCW and facilities from large SARS-CoV-2 outbreaks and preserved the capacity and function of the health care system during the pandemic.

In this work, testing of factor effects to the observed data from finite mixture distributions are discussed. Likelihood ratio tests are used to test whether factors of interest have significant effects to the mixture distribution model. To carry out the likelihood ratio tests, different methods about the computation algorithm for the maximum likelihood estimation (MLE) of the parameters in the mixture models are studied. These methods are applied to the data obtained from a laboratory study on emergence of Pontomyia oceana, where the effects of factors, such as sex and temperature, to the distribution of the dates that Pontomyia oceana emerged are investigated. From the results obtained, in some cases, three-component logistic distributions are fitted to the data with two peaks very close to each other. This is somewhat surprising as merely from the histogram, it is not easy to see and usually not expected to say there are two very close peaks. From the practical point of view, as the laboratory conditions excluded the possible effects related to semi-lunar tidal fluctuations that may have a dominating influence in nature. Thus the laboratory results helps to identify all the possible factors that have minor effects. Based on the results of this study, the difference between males and females, nevertheless, suggests that sex hormone may be involved in affecting the emergence dates. The suggestion of a third peak is unexpected from our point of view and it implies that there are factors we never suspected. It is worth noting that through rigorous statistical analysis presented here, it helps to provide an objective estimation on the distribution of the emergence dates as well as the corresponding proportions and the peak synchronous emergence dates in each period under different factor effects. We only start to speculate its possible adaptive meaning after the differences have been established as a true phenomenon. From this study, it reveals some additional biological phenomena worthy of more investigations.

An effective antiseptic agent is an essential component of a central venous catheter (CVC) care bundle, to protect against catheter-related bloodstream infections (CRBSIs). We conducted a trial to compare the incidences of CRBSI and the growth of insertion site flora in patients with CVC using 2% chlorhexidine gluconate–alcohol (CHG) or 10% povidone-iodine–alcohol (PVI) in the CVC care bundle. Patients who were admitted to two medical intensive care units (ICUs) and had CVC placement for >48 h were enrolled. Using a two-way crossover design with two six-month interventions, the ICUs were assigned to use either CHG or PVI in their care bundles. A total of 446 catheters in 390 subjects were enrolled in the study. The detection rate of flora was greater in the PVI group on both day 7 (26.6% versus 6.3%, p < 0.001) and day 14 (43.2% versus 15.8%, p < 0.001). The incidence rate of CRBSI was higher in the PVI group compared to the CHG group (2.15 vs. 0 events per 1000-catheter-days, p = 0.001), although the significance was lost in the multivariate analysis. In conclusion, 2% CHG was superior to 10% PVI in the CVC care bundle in terms of the inhibition of skin flora growth at CVC insertion sites and was potentially associated with lower incidence rates of CRBSI.

Background/purpose Superspreading events (SSEs) are pivotal in the spread of SARS-CoV-2. This study aimed to investigate an SSE of COVID-19 in a hospital and explore the transmission dynamics and heterogeneity of SSE. Methods We performed contact tracing for all close contacts in a cluster. We did nasopharyngeal or throat swabbing for SARS-CoV-2 by real-time RT-PCR. Environmental survey was performed. The epidemiological and clinical characteristics of the SSE were studied. Results Patient 1 with congestive heart failure and cellulitis, who had onset of COVID-19 two weeks after hospitalization, was the index case. Patient 1 led to 8 confirmed cases, including four health care workers (HCW). Persons tested positive for SARS-CoV-2 were HCW (n = 4), patient 1's family (n = 2), an accompanying person of an un-infected in-patient (n = 1), and an in-patient admitted before the SSE (n = 1). The attack rate among the HCW was 3.2 % (4/127). Environmental survey confirmed contamination at the bed rails, mattresses, and sink in the room patient 1 stayed, suggesting fomite transmission. The index case's sputum remained positive on illness day 35. Except one asymptomatic patient, at least three patients acquired the infection from the index case at the pre-symptomatic period. The effective reproduction number (Rt) was 0.9 (8/9). Conclusion The host factor (heart failure, longer viral shedding), transmissibility of SARS-CoV-2 (Rt, pre-symptomatic transmission), and possible multiple modes of transmission altogether contributed to the SSE. Rapid response and advance deployment of multi-level protection in hospitals could mitigate COVID-19 transmission to one generation, thereby reducing its impact on the healthcare system.

Summary Background Serratia marcescens is an important nosocomial pathogen causing significant outbreaks. Here we report an outbreak of bloodstream infection caused by S. marcescens at a 3500-bed hospital in Taiwan. The effective cooperative efforts of both laboratory personnel and infection control practitioners (ICPs) jointly contributed to the total control of the outbreak. Methods A sudden increase in the isolation of S. marcescens from blood cultures was noted in the Clinical Microbiology Laboratory. The information was passed to the ICPs and an investigation was initiated. Pulsed-field gel electrophoresis was used to study the relationships among the isolates. Results Pulsotype A was identified in 43 (82.7%) of the 52 blood isolates studied. They were isolated from 52 patients distributed across 22 wards that were surveyed by seven ICPs. All patients had undergone surgery before the infection, and fentanyl-containing intravenous fluids were used for pain control in 43 of them. Isolates from 42 belonged to pulsotype A. Three S. marcescens isolates, all from fentanyl-containing fluids and demonstrating pulsotype A, were identified from 251 environmental cultures. All fentanyl-containing fluids that were in use were withdrawn and the outbreak was stopped. Conclusions The outbreak of S. marcescens bloodstream infection apparently occurred through the use of fentanyl-containing fluids contaminated by a pulsotype A S. marcescens .

This paper considers a linear regression model with a one-dimensional control variable x and an m-dimensional response vector y=(y"1,...,y"m). The components of y are correlated with a known covariance matrix. Based on the assumed regression model, it is of interest to obtain a suitable estimation of the corresponding control value for a given target vector T=(T"1,...,T"m) on the expected responses. Due to the fact that there is more than one target value to be achieved in the multiresponse case, the m expected responses may meet their target values at different respective control values. Consideration on the performance of an estimator for the control value includes the difference of the expected response E(y"i) from its corresponding target value T"i for each component and the optimal value of control point, say x"0, is defined to be the one which minimizes the weighted sum of squares of those standardized differences within the range of x. The objective of this study is to find a locally optimal design for estimating x"0, which minimizes the mean squared error of the estimator of x"0. It is shown that the optimality criterion is equivalent to a c-criterion under certain conditions and explicit solutions with dual response under linear and quadratic polynomial regressions are obtained.

Background/Purpose Mycobacterium abscessus subsp. massiliense (a subspecies of the M. abscessus complex) is a rare causative agent of surgical site infection after cesarean section (C section). We tried to seek the common source of infection and unravel the optimal treatment modalities. Methods From September 2009 to October 2012, four postpartum women developed C-section wound infections caused by M. massiliense. Speciation of the four isolates was identified using of hsp65 , rpoB , and secA1 partial gene sequencing and the Basic Local Alignment Search Tool. The erm (41) and rrl genes were detected for the possibility of inducible macrolide resistance. Pulsed-field gel electrophoresis was used as a tool of molecular epidemiology. All patients underwent intensive intravenous and oral antimycobacterial regimens. Of these patients, three underwent debridement at least once. Results All four isolates were identified as M. abscessus subsp. massiliense . All of the isolates harbored a truncated erm (41) gene without rrl gene mutations, which explains the susceptibility to clarithromycin and azithromycin. Three isolates were indistinguishable by DNA strain typing, and the fourth strain was clonal with the other three strains. Their infections were not improved in spite of teicoplanin treatment initially. These patients underwent antimycobacterial regimens with/without surgery and were all cured. Discussion Teicoplanin treatment failure, painful cutaneous nodules, and persistent wound drainage alerted us to the possibility of nontuberculous mycobacterial skin and soft tissue infection. Accurate identification of subspecies, detection of drug resistance genes, susceptibility testing, and optimal antimycobacterial agents with/without surgical debridement are warranted for successful treatment.

Objectives To study norovirus gastroenteritis infection among residents and health care workers (HCWs) during an outbreak in a nursing home by investigating the attack rate and positive diagnostic rate for norovirus by reverse transcription–polymerase chain reaction (RT-PCR). Methods All members in a Chang Gung Memorial Hospital–affiliated nursing home from November 17, 2006, to November 25, 2006, including 236 residents and 125 HCWs, whose available medical records were available were consecutively included in the retrospective analysis. Fecal specimens of symptomatic residents and HCWs were tested for norovirus by RT-PCR. In addition, routine stool analysis and a stool culture study were conducted to identify the bacterial and parasitic agents. The fecal specimens of asymptomatic residents and HCWs were tested only for norovirus by RT-PCR. Results The outbreak was controlled within 9 days during the outbreak period. There were 51 symptomatic cases, 41 residents and 10 HCWs, during the norovirus outbreak. The odds ratio (OR) of the attack rate in the residents was approximately 2.4 times higher than that in the HCWs (OR: 2.4; 95% confidence interval [CI]: 1.2–5.0; P = .015). Norovirus was detected in 59 (30.6%) of 193 residents and in 11 (10.5%) of 105 HCWs who provided stool specimens for the study by RT-PCR. The OR of the positive diagnostic rate for norovirus by RT-PCR in the residents was approximately 3.8 times higher than that in the HCWs (OR: 3.8; 95% CI: 1.9–7.5; P Conclusions During an outbreak of norovirus gastroenteritis in a nursing home, the infection can be easily transmitted from person to person and affects both residents and HCWs. In addition, residents had a higher risk of norovirus gastroenteritis infection than HCWs.