Nori Yoshioka

Methicillin-resistant Staphylococcus aureus bacteremia at a university hospital in Japan

Methicillin-resistant Staphylococcus aureus (MRSA) has become a leading cause of infections in hospitals, and mortality from MRSA bacteremia is high. In this study, we assessed the clinical characteristics and optimum management of 115 patients with MRSA bacteremia who were admitted to Osaka University Hospital between January 2006 and December 2010. Sixty-nine of the patients survived and 46 died of heart failure or renal failure. The nonsurvivors had reduced levels of platelets and albumin, and increased aspartate aminotransferase, total bilirubin, blood urea nitrogen, and creatinine levels. Other causes of death included sepsis, septic shock plus respiratory failure, disseminated intravascular coagulation, and unknown causes. However, a significant number of those whose infections were catheter-derived survived. Nonsurvivors were more often administered catecholamines and consultation with an infection-control team (ICT) was significantly associated with improved survival. Patients about whom the ICT were consulted were administered significantly more additional anti-MRSA drugs, for example trimethoprim–sulfamethoxazole, clindamycin, and gentamycin, than patients who were not the subject of consultation, although trough values for vancomycin did not differ between the two groups. Catheter removal was significantly higher for surviving patients with severe or complicated infections. These results suggest the status of patients with MRSA bacteremia who did not survive was worse than those who did survive, but that ICT consultation might significantly affect survival by recommendation of appropriate care and anti-MRSA drug use.

Available, Bed-sided, Comprehensive (ABC) score to a diagnosis of Methicillin-resistant Staphylococcus aureus infection: a derivation and validation study

BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) infections continue to be a leading problem in health care facilities worldwide.MethodsThis single-center retrospective cohort study consisted of a derivation phase and a validation phase. The derivation phase included all patients admitted to Osaka University Hospital between May 2010 and April 2011. We proposed a provisional available, bed-sided, comprehensive (ABC) score, and evaluated its accuracy using the clinical diagnosis as a reference. We subsequently revised ABC scores based on k coefficient scores of each variable; this revision was validated by applying it to another patient population.ResultsA total of 172 patients and 154 cases were enrolled in the derivation and validation studies, respectively. The revised ABC score consisted of four simple variables: type of clinical specimen (1 to 3 points), Gram-staining result (1 point), presence of local inflammation (2 points), and a systemic inflammatory response (2 points). A revised score of ≥5 points was sensitive (93.8%) and specific (90.6%), and the area under the receiver-operating curve was 0.969 (95% CI; 0.957–1).ConclusionsWe developed a simple and comprehensive scoring system for diagnosis of nosocomial MRSA infections; this system is applicable in a wide variety of situations.

Evaluation of the highly sensitive chemiluminescent enzyme immunoassay “Lumipulse HBsAg-HQ” for hepatitis B virus screening

Ongoing efforts in the development of HBsAg detection kits are focused on improving sensitivity and specificity. The purpose of this study was to evaluate an improved, highly sensitive quantitative assay, “Lumipulse HBsAg‐HQ”, a chemiluminescent enzyme immunoassay designed for a fully automated instrument, the “Lumipulse G1200”.

Genomic reorganization by IS26 in a bla NDM-5-bearing FII plasmid of Klebsiella pneumoniae isolated from a patient in Japan

An NDM-5-producing Klebsiella pneumoniae ST147 strain was isolated from a Japanese patient who had not travelled abroad in at least 5 years. Whole-genome sequencing revealed a genomic rearrangement in an FII plasmid harbouring blaNDM-5 due to the replicative transposition of IS26. A hypothetical structure was proposed for its ancestral plasmid, and comparative genomic analysis of the plasmid suggested the dissemination of structurally similar plasmids harbouring blaNDM-5 in Asian and Middle Eastern countries.

Vaccination strategy for epidemic viral diseases in healthcare workers: Cut-off for optimal immunization

Healthcare workers (HCWs) are at an increased risk of being exposed to epidemic viral diseases (EVDs), such as measles, rubella, mumps, and varicella-zoster. Currently, in case of the absence of written records on previous immunizations, the Japanese Society for Infection Prevention and Control guidelines require HCWs to have antibody titers higher than laboratory thresholds, possibly leading to over-immunization. We report our vaccination strategy and the consequent incidences of EVDs at the Osaka University Hospital between 2000 and 2016. In 2001, we initiated an annual serology check of antibody titers against EVDs and immunization for newly employed HCWs. As an additional vaccination program, all HCWs with low antibody titers were vaccinated in 2005 and 2010. Antibody titers were determined by an enzyme immunoassay (EIA), with a positive range of >2.0 cut-off index. After implementing the vaccination strategy to keep the laboratory threshold, there were only sporadic cases of EVDs among HCWs. More than 99% of individuals who had positive titers in 2005 remained the positive antibody titers in 2010, indicating that a minimum interval of 5 years is enough to measure immunity. Unprotected workers can, even silently, transmit the contagious viruses to patients and coworkers, possibly resulting in a nosocomial outbreak. However, over-vaccination may yield adverse effects and financial burdens. Our observational data indicate that the laboratory cut-off index of >2.0 by EIA may provide a sufficient herd immunity to prevent EVDs among HCWs.

Durability of immunity by hepatitis B vaccine in Japanese health care workers depends on primary response titers and durations

Background Health care workers (HCWs) are frequently exposed to hepatitis B virus (HBV) infection. The efficacy and safety of immunization with the hepatitis B (HB) vaccine are well recognized, but the durability of immunity and need for booster doses in those with secondary vaccine response failure remains controversial. Methods This was a retrospective cohort study performed at Osaka University Hospital, Japan. We examined antibodies against HB surface antigen (anti-HBs) titers annually after immunization for previously non-immunized HCWs. Primary responders were categorized by their sero-positive durations as short responders (those whose anti-HBs titers declined to negative range within 3 years), and long responders (those who retained positive anti-HBs levels for 3 years and more). We re-immunized short responders with either single or 3-dose boosters, the long responders with a single booster when their titers dropped below protective levels, and examined their sero-protection rates over time thereafter. Results From 2001 to 2012, data of 264 HCWs with a median age of 25.3 were collected. The rate of anti-HBs positivity after primary vaccination were 93.0% after three doses (n = 229), 54.5% after two doses (n = 11), and 4.2% after a single dose (n = 24). Of 213 primary responders, the anti-HBs levels of 95 participants (44.6%) fell below the protective levels, including 46 short responders and 49 long responders. HCWs with higher initial anti-HBs titers after primary vaccination had significantly longer durations of sero-positivity. For short responders, 3-dose booster vaccination induced a longer duration of anti-HBs positivity compared to a single-dose booster, whereas for long responders, a single-dose booster alone could induce prolonged anti-HBs positivity. Conclusion Our preliminary data suggested that it may be useful to differentiate HB vaccine responders based on their primary response durations to maintain protective levels of anti-HBs efficiently. A randomized, prospective, large-scale study is warranted to support our findings.

Novel and Simple Approach to Estimating the Actual Incidence of Blood and Body Fluid Exposure

BACKGROUND There is no current way to determine the actual blood and body fluid exposure (BBFE) incidence in hospitals. We propose a simple, reliable, and widely available method for the accurate estimation of BBFE. METHODS Data for BBFE for healthcare workers between 2006 and 2015 at Osaka University Hospital were retrospectively extracted from the electronic records. Annual positivity of hepatitis C virus (HCV) antibody in the source individuals and overall patient population were calculated over time. We created an estimation formula focusing on the difference in HCV positivity between the source individuals and overall patient population for the actual number of BBFEs. A linear regression model was used to evaluate the temporal change in the reported and estimated BBFEs. RESULTS During the study period, 937 BBFEs were reported. HCV positivity between the post-BBFE cohort and overall patient population greatly differed; the incidence ratio ranged from 2.1 to 5.7. The linear regression model revealed that the reported BBFEs did not significantly change during the study period (the slope, 1.315 [95% confidence interval (C.I.): -0.849 to 3.480, p = 0.199]). The annual incidence ratio of the estimated and reported BBFEs significantly reduced over time (the slope, -0.287 [95% C.I.: -0.488 to -0.086, p = 0.011]), indicating that, although the reported number of BBFEs seemed unchanged, the estimated incidence decreased. CONCLUSIONS We propose a novel and simple approach to estimating the actual incidence of BBFEs in hospitals using the difference in HCV positivity between the post-BBFE cohort and overall patient population.