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We studied the seroprevalence of HBsAg, anti-HBs and anti-HBc and the vaccination histories among health care workers (HCWs) at a large suburban referral hospital in Korea. The purpose of this study was to determine the immune status of HCWs against hepatitis B virus and we also wanted to prepare a practical guideline to protect HCWs from occupational exposure. During December, 2003, 571 HCWs (56 physicians, 289 nurses, 113 technicians and 113 aid-nurses) aged between 21 and 74 yr were included in the surveillance. The positive rates of HBsAg and anti-HBs were 2.4% (14/571) and 76.9% (439/571), respectively. The positive rate of anti-HBs was lower in the physician group, and this was associated with the male gender and older age. Of the 439 anti-HBs positive cases, 320 cases (73.1%) were anti-HBc negative and this was significantly associated with a past history of HBV vaccination. The distribution of the anti-HBs levels was not associated with age (except for HCWs in their sixties), gender or occupation. Our study revealed that the seroprevalence rates of HBsAg and anti-HBs in HCWs in Korea were not different from those of the general population. Based on this surveillance, we can make reasonable decisions in case of occupational exposure to hepatitis B virus.

Enzyme immunoassays (EIA) to detect glutamate dehydrogenase or toxins A (TcdA) and B (TcdB), a cytotoxicity assay, and bacteriologic culture have disadvantages when applied individually to diagnosis of Clostridium difficile infections. Stool specimens (n ‫؍‬ 1,596) were subjected to toxin detection via an enzymelinked fluorescent immunoassay (ELFA; Vidas CDAB assay) and bacteriologic culture for toxigenic C. difficile in a three-step algorithm with additional toxigenic culture. Isolates (n ‫؍‬ 163) from ELFA-negative stool specimens were examined via ELFA for toxin production. We amplified tcdA and tcdB from C. difficile isolates and tcdB from stool specimens that were ELFA positive or equivocal and culture negative, and we compared the results to those obtained with the three-step algorithm. More than 26% of stool specimens (419/1,596) were culture positive, yielding 248 isolates (59.2%) with both toxin genes (tcdA-and tcdB-positive isolates), 88 isolates (21.0%) with either tcdA or tcdB, and 83 (19.8%) that had no toxin genes (tcdA-and tcdB-negative isolates). Among 49 (culture-negative/ELFA-positive or -equivocal) stool specimens, 53.1% (26/49) represented tcdB-positive isolates. Therefore, the total number of PCR-positive cases was 362, and 27.1% (98/362) of these were detected through toxigenic culture. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 63.3%, 96.7%, 90.5%, and 92.4% (ELFA alone); 92.8%, 93.3%, 80.2%, and 97.8% (culture); and 70.7%, 91.4%, 95.5%, and 100% (three-step algorithm ELFA and bacterial culture with toxigenic culture), respectively, with culture and PCR for tcdA and tcdB as the standards. Thus, sensitivity and specificity were highest using culture and ELFA, respectively, but we recommend the three-step algorithm comprising EIA to detect both toxins and toxigenic culture for C. difficile as a practical method for achieving better PPV and NPV.Clostridium difficile is an important nosocomial pathogen, causing antimicrobial-associated diarrhea and pseudomembranous colitis. Toxins A (TcdA) and B (TcdB) mediate the pathogenesis of C. difficile infection (CDI), and toxin detection is an important part of diagnosis. A cytotoxicity neutralization assay (CNA) is the reference method for toxin detection, but it is expensive and time-consuming and requires tissue culture facilities (34,35). Most laboratories now use a commercial enzyme immunoassay (EIA) to detect TcdA and/or TcdB, with the benefits of rapid turnaround time and ease of use (3,21,22,23,26,27,33,35). The putative Ͼ90% sensitivity of toxin EIAs is not often realized in practice, but EIA is the only toxin detection method available to many routine medical laboratories. The demand for EIA kits detecting both TcdA and TcdB has increased due to increased worldwide prevalence of TcdA-negative, TcdB-positive (TcdAϪ TcdBϩ) strains (1,12,24,29,32).A two-step algorithm, based upon EIA-based detection of species-specific antigen glutamate dehydrogenase (GDH-Ag) and toxin detection via CN...

The prevalence of toxigenic Clostridium difficile in Korea has been reported to be approximately 60–80 %. Although the prevalence of the tcdA−tcdB+ C. difficile strain was less then 5 % prior to the year 2000, it has become an emerging nosocomial pathogen in Korea. Therefore, we have attempted to determine the multicentre nationwide prevalence of tcdA+tcdB+ and tcdA−tcdB+ C. difficile for epidemiological purposes. C. difficile strains (n=724, 30 from 2000, 80 from 2001, 74 from 2002, 76 from 2003, 179 from 2004, 285 from 2005) were obtained retrospectively from January 2000 to December 2005 from in-patients at 6 hospitals, all of whom were suspected of having C. difficile-associated disease (CDAD), colitis or pseudomembranous colitis. The numbers of participating hospitals varied yearly (1 in 2000, 2 in 2001–2003, 3 in 2004, 5 in 2005). The hospitals were located in Seoul (n=4), Kyunggi Province (n=1) and Busan (n=1), Korea. PCR assays for tcdA and tcdB genes were conducted using 724 unduplicated C. difficile isolates. The mean prevalence of tcdA+tcdB+ and tcdA−tcdB+ C. difficile strains over the 6 years was 51.8 % (38.4–59.3 %) and 25.8 %(10–56.0 %), respectively. The mean prevalence of tcdA−tcdB+ C. difficile strains was less than 7 % until 2002, but began to increase in 2003 (13.2 %) and achieved a peak in 2004 (50.3 %). In 2005, the mean prevalence of tcdA+tcdB+ and tcdA−tcdB+ C. difficile strains was 47.7 % (30.9–60.3 %) and 27.0 % (17.6–54.8 %), respectively. This nationwide epidemiological study showed that tcdA−tcdB+ C. difficile strains have already spread extensively throughout Korea, and our results provide basic data regarding the controversies currently surrounding the toxigenicity of tcdA−tcdB+ C. difficile. The use of enzyme immunoassays capable of detecting both TcdA and TcdB is strongly recommended for the diagnosis of CDAD in microbiology laboratories, in order to control the spread of the tcdA−tcdB+ strains of C. difficile.

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