Nationwide Survey for Current Status of Laboratory Diagnosis of Clostridioides difficile Infection in Korea

Background@#The interest in Clostridioides difficile infection (CDI) has increased, and the choice of assays became wider since the first national survey in Korea on CDI diagnosis in 2015. We conducted a survey of the domestic CDI assays with more varied questions to understand the current situation in Korea. @*Methods@#In April 2018, about 50 questions on the current status of CDI assays and details on implementation and perceptions were written, and a survey questionnaire was administered to laboratory medicine specialists in 200 institutions. @*Results@#One-hundred and fifty institutions responded to the questionnaire, of which 90 (60.0%) including one commercial laboratory, performed CDI assays. The toxin AB enzyme immunoassay (toxin AB EIA), nucleic acid amplification test (NAAT), and C. difficile culture, glutamate dehydrogenase assay, alone or in combination with other assays, were used in 75 (84.3%), 52 (58.4%), 35 (36.0%), and 23 (25.8%), respectively, and 65 (73.0%) institutions performed a combination of two or more assays. The sensitivity of toxin AB EIA was more negatively perceived, and that on specificity was more positively perceived. The perception of sensitivity and specificity of NAAT was mostly positive. Perception on the algorithm test projected it as useful but in need of countermeasures. Sixty-three (73.3%) institutions responded that they performed surveillance on CDI. @*Conclusion@#This study provides useful evidence on the current status of CDI laboratory diagnosis in Korea as well as on items that require improvement and is thought to aid in standardizing and improving the CDI laboratory diagnosis in Korea.

Laboratory Diagnostic Methods for Clostridioides difficile Infection: the First Systematic Review and Meta-analysis in Korea

Background@#Various methods are used for the diagnosis of Clostridioides difficile infection (CDI). We systematically analyzed and investigated the performance of current laboratory diagnostic methods for CDI. @*Methods@#We performed systematic review and meta-analysis of studies in PubMed, Web of Science, Cochrane Library, and KoreaMed. The following methods were evaluated: glutamate dehydrogenase (GDH) enzyme immunoassays (GDH EIAs), toxin A and B detection by enzyme immunoassays (toxin AB EIAs), and nucleic acid amplification tests (NAATs) for C. difficile toxin genes. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of each method were calculated. @*Results@#Based on 39 studies, the pooled sensitivities/specificities were 92.7%/94.6%, 57.9%/97.0%, and 90.0%/95.8% for GDH EIAs, toxin AB EIAs, and NAATs, respectively, compared with those of toxigenic culture. The pooled sensitivities of automated EIAs were significantly higher than those of non-automated EIAs for both GDH and toxins A and B.The pooled sensitivity of Xpert C. difficile was significantly higher than those of other NAATs. PPVs increased as CDI prevalence increased, and NPVs were excellent when CDI prevalence was low; at CDI prevalence of 5%, PPV = 37%–65% and NPV = 97%–100%;at CDI prevalence of 50%, PPV = 92%–97% and NPV = 65%–98%. @*Conclusions@#Toxin AB EIAs still show unsatisfactory sensitivity, whereas GDH EIAs and NAATs show relatively high sensitivity. However, toxin AB EIAs are the most specific tests. This study may provide useful information for CDI diagnosis.

Laboratory Diagnosis of Clostridium difficile Infection in Korea: The First National Survey

In May 2015, we conducted a voluntary online survey on laboratory diagnostic assays for Clostridium difficile infection (CDI) across clinical microbiology laboratories in Korea. Responses were obtained from 66 laboratories, including 61 hospitals and five commercial laboratories. Among them, nine laboratories reported having not conducted CDI assays. The toxin AB enzyme immunoassay (toxin AB EIA), nucleic acid amplification test (NAAT), and C. difficile culture, alone or in combination with other assays, were used in 51 (89.5%), 37 (64.9%), and 37 (64.9%) of the remaining 57 laboratories, respectively, and 23 (40.4%) of the laboratories performed all three assays. Only one laboratory used the glutamate dehydrogenase assay. Nine laboratories used the toxin AB EIA as a stand-alone assay. The median (range) of examined specimens in one month for the toxin AB EIA, NAAT, and C. difficile culture was 160 (50–2,060), 70 (7–720), and 130 (9–750), respectively. These findings serve as valuable basic data regarding the current status of laboratory diagnosis of CDI in Korea, offering guidance for improved implementation.

Evaluation of Xpert C. difficile, BD MAX Cdiff, IMDx C. difficile for Abbott m2000, and Illumigene C. difficile Assays for Direct Detection of Toxigenic Clostridium difficile in Stool Specimens

BACKGROUND: We evaluated the performance of four commercial nucleic acid amplification tests (NAATs: Xpert C. difficile, BD MAX Cdiff, IMDx C. difficile for Abbott m2000, and Illumigene C. difficile) for direct and rapid detection of Clostridium difficile toxin genes. METHODS: We compared four NAATs on the same set of 339 stool specimens (303 prospective and 36 retrospective specimens) with toxigenic culture (TC). RESULTS: Concordance rate among four NAATs was 90.3% (306/339). Based on TC results, the sensitivity and specificity were 90.0% and 92.9% for Xpert; 86.3% and 89.3% for Max; 84.3% and 94.4% for IMDx; and 82.4% and 93.7% for Illumigene, respectively. For 306 concordant cases, there were 11 TC-negative/NAATs co-positive cases and 6 TC-positive/NAATs co-negative cases. Among 33 discordant cases, 18 were only single positive in each NAAT (Xpert, 1; Max, 12; IMDx, 1; Illumigene, 4). Positivity rates of the four NAATs were associated with those of semi-quantitative cultures, which were maximized in grade 3 (>100 colony-forming unit [CFU]) compared with grade 1 (<10 CFU). CONCLUSIONS: Commercial NAATs may be rapid and reliable methods for direct detection of tcdA and/or tcdB in stool specimens compared with TC. Some differences in the sensitivity of the NAATs may partly depend on the number of toxigenic C. difficile in stool specimens.

Analytical and Clinical Validation of Six Commercial Middle East Respiratory Syndrome Coronavirus RNA Detection Kits Based on Real-Time Reverse-Transcription PCR

BACKGROUND: During the 2015 outbreak of Middle East Respiratory Syndrome coronavirus (MERS-CoV), six different commercial MERS-CoV RNA detection kits based on real-time reverse-transcription polymerase chain reaction (rRT-PCR) were available in Korea. We performed analytical and clinical validations of these kits. METHODS: PowerChek (Kogene Biotech, Korea), DiaPlexQ (SolGent, Korea), Anyplex (Seegene, Korea), AccuPower (Bioneer, Korea), LightMix (Roche Molecular Diagnostics, Switzerland), and UltraFast kits (Nanobiosys, Korea) were evaluated. Limits of detection (LOD) with 95% probability values were estimated by testing 16 replicates of upstream of the envelope gene (upE) and open reading frame 1a (ORF1a) RNA transcripts. Specificity was estimated by using 28 nasopharyngeal swabs that were positive for other respiratory viruses. Clinical sensitivity was evaluated by using 18 lower respiratory specimens. The sensitivity test panel and the high inhibition panel were composed of nine specimens each, including eight and six specimens that were positive for MERS-CoV, respectively. RESULTS: The LODs for upE ranged from 21.88 to 263.03 copies/reaction, and those for ORF1a ranged from 6.92 to 128.82 copies/reaction. No cross-reactivity with other respiratory viruses was found. All six kits correctly identified 8 of 8 (100%) positive clinical specimens. Based on results from the high inhibition panel, PowerChek and AccuPower were the least sensitive to the presence of PCR inhibition. CONCLUSIONS: The overall sensitivity and specificity of all six assay systems were sufficient for diagnosing MERS-CoV infection. However, the analytical sensitivity and detection ability in specimens with PCR inhibition could be improved with the use of appropriate internal controls.

Detection of Respiratory Viruses and Atypical Bacterial Pathogens in Infants with Acute Respiratory Infections Using Multiplex PCR / 대한임상미생물학회지

Multiplex PCR of nasopharyngeal aspirates detected viruses and atypical bacteria in 75.3% (219/291) of infants with acute respiratory infections from July 2010 to June 2013. Frequent viruses were human rhinovirus (29.9%), parainfluenza virus (21.7%), respiratory syncytial virus (17.9%), and human metapneumovirus (10.3%). Mycoplasma pneumoniae and Bordetella pertussis were detected in 3.4% and 0.3%, respectively.

Comparison of ChromID Agar and Clostridium difficile Selective Agar for Effective Isolation of C. difficile from Stool Specimens

BACKGROUND: ChromID Clostridium difficile agar (IDCd; bioMerieux SA, France) is a recently developed chromogenic medium for rapid and specific isolation of C. difficile. We compared the performance of IDCd with that of Clostridium difficile Selective Agar (CDSA). METHODS: A total of 530 fresh stool specimens were collected from patients with clinical signs compatible with C. difficile infection, and cultures for C. difficile were performed on IDCd and CDSA. C. difficile colonies were identified by spore staining, odor, use of an ANI identification test kit (bioMerieux SA), and multiplex PCR for tcdA, tcdB, and tpi. RESULTS: The concordance rate between IDCd and CDSA was 90.6% (480/530). The positivity rates on IDCd on days 1 and 2 (55.6% and 85.0%, respectively) were significantly higher than those on CDSA (19.4% and 75.6%, respectively) (P<0.001 for day 1 and P=0.02 for day 2), but the detection rates on IDCd and CDSA on day 3 were not different (89.4% vs. 82.8%, P=0.0914). On day 3, the recovery rates for non-C. difficile isolates on IDCd and CDSA were 30.2% (160/530) and 22.1% (117/530), respectively (P=0.0075). Clostridium spp. other than C. difficile were the most prevalent non-C. difficile isolates on both media. CONCLUSIONS: The culture positivity rates on IDCd and CDSA were not different on day 3 but IDCd may allow for rapid and sensitive detection of C. difficile within 2 days of cultivation.

Nasal Carriage of 200 Patients with Nasal Bone Fracture in Korea

BACKGROUND: Pathogens in the nasal cavity during nasal surgery could lead to a systemic infectious condition, such as bacteremia, nosocomial infection, or toxic shock syndrome. However, there is no research about the prevalence of nasal carriage in patients with nasal bone fracture. METHODS: This was a prospective, double-blind, randomized study about the rate of nasal carriage in 200 patients with nasal bone fracture in Korea. Nasal secretions were taken from both the middle nasal meatus and colonized. All analyses were carried out using SPSS software. RESULTS: Pathogens were identified in 178 of the 200 cases. Coagulase-negative staphylococci (CNS) were the most cultured bacteria in 127 (66.84%) of the 190 total patients after excluding 10 cases of contaminated samples, and methicillin-resistant coagulase-negative staphylococci (MRCNS) were found in 48 (25.26%). Staphylococcus aureus was the second most identified pathogen, found in 36 (18.95%), followed by 7 cases (3.68%) of methicillin-resistant Staphylococcus aureus (MRSA). The prevalence rate of MRSA in the females was higher than that in the males (RR=4.70; 95% CI, 1.09-20.18), but other demographic factors had no effect on the prevalence rate of MRSA and MRCNS. CONCLUSIONS: The prevalence rate of these pathogens in patients with nasal bone fracture in Korea was similar to other reports. However, few studies have addressed the prevalence rate of CNS and MRCNS in accordance with risk factors or the change in prevalence according to specific prophylaxis against infectious complications. Additional research is needed on the potential connections between clinical factors and microbiological data.

Comparison of an Automated Repetitive Sequence-based PCR Microbial Typing System with IS6110-Restriction Fragment Length Polymorphism for Epidemiologic Investigation of Clinical Mycobacterium tuberculosis Isolates in Korea / 대한진단검사의학회지

Tuberculosis remains a severe public health problem worldwide. Presently, genotyping is used for conducting epidemiologic and clinical studies on tuberculosis cases. We evaluated the efficacy of the repetitive sequence-based PCR (rep-PCR)-based DiversiLab(TM) system (bioMerieux, France) over the IS6110-restriction fragment length polymorphism analysis for detecting Mycobacterium tuberculosis. In all, 89 clinical M. tuberculosis isolates collected nationwide from Korea were used. The DiversiLab system allocated the 89 isolates to 8 groups with 1 unique isolate when a similarity level of 95% was applied. Seventy-six isolates of the Beijing family and 13 isolates of non-Beijing family strains were irregularly distributed regardless of rep-PCR groups. The DiversiLab system generated a rapid, sensitive, and standardized result. It can be used to conduct molecular epidemiologic studies to identify clinical M. tuberculosis isolates in Korea.

The Incidence and Clinical Features of Clostridium difficile Infection; Single Center Study / 대한소화기학회지

BACKGROUND/AIMS: Clostridium difficile is the predominant cause of nosocomial diarrhea. Recently, the incidence of Clostridium difficile infection (CDI) increases in Europe and North America. A retrospective study was performed to evaluate the change of incidence and clinical features of CDI in Korea. METHODS: From January 2003 to December 2008, inpatients diagnosed with CDI in Seoul Paik hospital were enrolled. The diagnosis of CDI was made when patients complained diarrhea with any positive results in C. difficile toxin assay, stool culture, or endoscopy. The incidence, recurrence rate, and clinical features were compared between early period (2003-2005) and late period (2006-2008). RESULTS: The incidence of CDI was 21.73 cases per 10,000 admitted patients in early period group, and significantly increased to 71.71 cases per 10,000 admitted patients in late period group (p<0.01). The hospital stay duration at the time of CDI diagnosis was shorter in late period group. Cephalosporin had the highest ratio as the causative antibiotics of CDI. However, there was no difference in recurrence rate between early and late period groups. Recurrence associated clinical factor was serum albumin level. CONCLUSIONS: The incidence of CDI showed increasing tendency during recent 6 years. The awareness of increasing disease burden is the first step in control of CDI.

Recombinant Chromosome 4 with Partial 4p Deletion and 4q Duplication Inherited from Paternal Pericentric Inversion / 대한진단검사의학회지

Pericentric inversion of chromosome 4 can give rise to 2 alternate recombinant (rec) chromosomesby duplication or deletion of 4p. The deletion of distal 4p manifests as Wolf-Hirschhorn syndrome (WHS). Here, we report the molecular cytogenetic findings and clinical manifestations observed in an infant with 46,XX,rec(4)dup(4q)inv(4)(p16q31.3)pat. The infant was delivered by Cesarean section at the 33rd week of gestation because pleural effusion and polyhydramnios were detected on ultrasonography. At birth, the infant showed no malformation or dysfunction, except for a preauricular skin tag. Array comparative genomic hybridization analysis of neonatal peripheral blood samples showed a gain of 38 Mb on 4q31.3-qter and a loss of 3 Mb on 4p16.3, and these results were consistent with WHS. At the last follow-up at 8 months of age (corrected age, 6 months), the infant had not achieved complete head control.

Current Status of External Quality Assessment of Fecal Occult Blood Test / 대한진단검사의학회지

BACKGROUND: Nationwide external quality assessment (EQA) of the fecal occult blood test (FOBT) in Korea was first introduced in 2007-2009. The EQA results were analyzed to assess the current status of FOBT and to plan the continuation of the EQA program. METHODS: The surveys included 40 hospitals in the preliminary survey conducted in 2007, 249 general hospitals in 2008, and 389 hospitals in 2009. In the surveys, the participating hospitals provided the results of the distributed materials and replies to the questionnaire on the FOBT test procedures and quality controls. RESULTS: In the surveys conducted between 2007 and 2009, a total of 650 institutes submitted 653 test system results; 3 institutes used 2 kinds of methods. All of the institutes used immunologic methods; 107 institutes (16.5%) used quantitative equipments and 546 institutes (84.0%) used qualitative kits. Most quantitative tests yielded consistent positive or negative results; however, their cut-off and measured values differed according to the equipments used. A low-level material tested in 2007 was negative in the quantitative methods but positive in some qualitative methods because of lower detection limits. The discordance rates among quantitative tests were 3.2% in 2007, 4.4% in 2008, and 0% in 2009 and the rates among qualitative tests were 13.8% in 2008 and 2.6% in 2009. Semi-solid EQA materials showed the ability to evaluate the overall test procedures with acceptable stability. CONCLUSIONS: In the first Korean FOBT EQA, commercially available EQA materials were proven to be stable. Continuation of the EQA program and further education of laboratory personnel are needed to reduce inconsistency in results. Further, the test kit, procedures, and result reports must be standardized.

Clinical and Epidemiological Comparison of Human Metapneumovirus and Respiratory Syncytial Virus in Seoul, Korea, 2003-2008

Human metapneumovirus (HMPV) shares clinical and epidemiological characteristics with well-known respiratory syncytial virus (RSV). The aim of this study was to investigate the clinical and epidemiological differences between HMPV- and RSV-induced wheezing illnesses. A total of 1,008 nasopharyngeal aspirate specimens was collected from 1,008 pediatric patients hospitalized with acute respiratory tract infection at Inje University Sanggye Paik Hospital from December 2003 to April 2008, and tested for seven common respiratory viruses. Conditions classified as wheezing illness were bronchiolitis, reactive airways disease, and bronchial asthma. HMPV caused a significantly lower proportion of wheezing illness when compared to RSV (48.1% vs. 82.2%, P<0.05). HMPV-induced wheezing illness occurred predominantly in older patients when compared to RSV patients (P<0.001). RSV infections peaked in the fall and winter followed by peaks of HMPV infection in winter and spring. Eosinophil counts were significantly higher (P<0.01) in RSV patients when compared to HMPV patients. These results show that human metapneumovirus patients exhibit several different clinical and epidemiological characteristics, such as higher proportion of wheezing illness, age and seasonal incidence, and eosinophil counts, when compared to RSV patients.

Outbreak of Swine-Origin Influenza A (H1N1); Experience of a Regional Center in Seoul during a Month, August-September 2009 / 대한임상미생물학회지

BACKGROUND: The aim of this study is to clarify the epidemiology of swine-origin influenza A (H1N1) virus 2009 (S-OIV) during the first month of outbreak at one of influenza clinic in Seoul, Korea. METHODS: We documented the epidemiologic and clinical features of S-OIV-confirmed cases who visited a university hospital in Northeastern Seoul between August 21 and September 20, 2009. Nasopharyngeal swab of patients with acute febrile respiratory illnesses were evaluated with rapid influenza antigen tests and multiplex RT-PCR for S-OIV and seasonal influenza A. RESULTS: A total of 5,322 patients with acute febrile respiratory illnesses were identified at our influenza clinic for the study period. S-OIV was confirmed in 309 patients by RT-PCR. The patients ranged from 2 months to 61 years of age and 189 patients (61.2%) were teenagers. Eighty-one patients had known contact with S-OIV-confirmed patients in schools (N=61), households (N=15), and healthcare facilities (N=3). Frequent symptoms were fever (94.5%), cough (73.1%), sore throat (52.1%), and rhinorrhea (50.5%). Gastrointestinal symptoms were also present in 10 patients (4.9%). Ten patients (4.9%) required hospitalizations. Seventy patients (22.7%) could not take oseltamivir at the first visits, however, all of them recovered without complication. Rapid antigen tests showed the sensitivity of 44.4% (130/294). Patients with positive antigen tests, compared with negative antigen tests, showed higher frequencies of rhinorrhea (60.8% vs 43.3%, P=0.004) and stuffy nose (33.8% vs 20.1%, P=0.012). CONCLUSION: S-OIV infections spread predominately in school-aged children during the early accelerating phase of the outbreak. Rapid influenza antigen tests were correlated with nasal discharge and obstruction.

Comparison of Two Enzyme Immunoassay for Detection of Clostridium difficile Toxin A and Toxin B / 대한진단검사의학회지

BACKGROUND: Enzyme immunoassay (EIA) capable of detecting both toxin A and toxin B is strongly recommended for the diagnosis of Clostridium difficile associated disease. Therefore, we evaluated two different EIAs for the detection of C. difficile toxin A/B. METHODS: For a total of 228 stool specimens we performed bacteriologic cultures for C. difficile and examined for toxin A and toxin B using enzyme linked fluorescent immunoassay (ELFA; VIDAS CDAB, Bio-Merieux sa, France) and ELISA (C.DIFFICILE TOX A/B II, TECHLAB, USA). We also performed PCR assays for toxin A and B genes in 117 C. difficile isolates that grew from the stool cultures and compared the results with those obtained with the two different EIAs. RESULTS: The concordance rate between ELFA and ELISA was 85.5% (195/228). Using the culture and PCR results as the standard, the sensitivity/specificity of the ELFA and ELISA were 65.0%/72.1% and 71.8%/70.3%, and for positive/negative predictive values were 78.4%/69.6% and 71.8%/70.3%, respectively (P value >0.05). No differences were observed between the results of ELFA and ELISA with toxin A- toxin B+ strains of C. difficile. CONCLUSIONS: The sensitivity of the ELISA was slightly higher than that of ELFA for toxin A and toxin B, but the specificity and positive predictive value of the ELFA were rather higher than those of the ELISA, although no statistical differences were observed. A bacteriologic culture and PCR assay for toxin genes are recommended in case the both EIAs are negative.

The Implementation and Effects of a Clinical Laboratory Accreditation Program in Korea from 1999 to 2006 / 대한진단검사의학회지

BACKGROUND: The Korean Laboratory Accreditation Program (KLAP) by the Korean Society of Laboratory Medicine (KSLM) was started in 1999. We summarized history and achievement of KLAP for the last 8 yr. METHODS: We analyzed 8 yr data (1999-2006) of historical events, trends of participating laboratories, and scores according to the impact of the question to the outcome of the tests. Inspection check lists are for 'laboratory management', 'clinical chemistry', 'diagnostic hematology', 'clinical microbiology', 'diagnostic immunology', 'transfusion medicine', 'cytogenetics', 'molecular genetics', 'histocompatibility', 'flow cytometry', and 'comprehensive laboratory test verification report'. The laboratories with score 90 or higher got 2-yr certificate and laboratories with score between 60 and 89 got 1-yr certificate. The laboratories with score below 60 failed accreditation. RESULTS: The number of accredited laboratories was 2.4 times higher in 2006 (n=227) than in 1999 (n=96). Inspection check lists have been revised 5 times till 2006. The average accreditation rate was 99.6% during these periods and the 2-yr accreditation rate was 32.4% in 2000, 45.6% in 2001, 53.3% in 2002, 47.3% in 2003, 68.5% in 2004, 37.7% in 2005, and 47.7% in 2006. Number of participants in inspector training workshops increased from 89 in 2000 to 766 in 2006. CONCLUSIONS: The KLAP has been in place successfully and stabilized over the past 8 yr. It seemed to enhance the laboratory quality. Efforts for improvement of quality control and inspector training workshops appeared to be in the main contributing factors.

Influence of the Pre-Analytical Specimen Storage Conditions on the Fecal Occult Blood Test Results / 대한진단검사의학회지

BACKGROUND: Korean national cancer screening program selected fecal occult blood test (FOBT) as a primary screening method of colorectal carcinoma in adult > or =50 yr old irrespective of symptom. Notice to pre-analytical errors is especially important for the FOBT because examinees collect and submit their specimens to laboratories by themselves. We examined the influences of the fecal storage temperatures, durations and with or without buffer on the FOBT results. METHODS: Thirty FOBT-positive specimens above 100 ng/mL were used for the study from July to August 2008. Quantitative FOBT was performed with OC-sensors II (Eiken Chemical Co., Japan). Each specimen was divided into 4 groups. Two groups in plastic buffer-free containers were kept either at 4degrees C or room temperature (25-28degrees C), respectively. Another two groups in buffer-tubes were also kept either at 4degrees C or room temperature. Each group was repeatedly examined with same method every 24 hr up to 120 hr. RESULTS: Eleven specimens (36.7%) in buffer-free containers converted to negative results (below the 100 ng/mL) after 24 hr and 17 specimens (56.7%) did after 48 hr at room temperature. Ten specimens (33.3%) in buffer-free containers converted to negative after 48 hr at 4degrees C. Specimens contained in buffer-tubes showed little change; 3 specimens (10.0%) at room temperature and no specimen at 4degrees C showed negative conversions after 48 hr. CONCLUSIONS: Buffer-tube minimizes false negative FOBT results during pre-analytical delay of specimen. The examinees using buffer-free containers need to be educated to hand in their specimens to laboratories as soon as possible.

The Possibility of Fluid Contamination Within Syringes in Case of Experimental Needle Contamination

PURPOSE: The present study examined the risk of intraocular infection only in cases where the injection needle was replaced when the injection needle was contaminated before intraocular injection. METHODS: Staphylococcus aureus and Staphylococcus epidermidis were cultured and smeared on the end of 30 syringe needles containing 0.1 mL normal saline. After removing only the injection needle, the normal saline in the syringes was injected onto blood agar plates and cultured. RESULTS: The culture results were positive in 21 out of 30 samples in the group smeared with Staphylococcus aureus, and in 25 out of 30 samples in the group smeared with Staphylococcus epidermidis. CONCLUSIONS: When the injection needle is contaminated, the replacement of the needle does not eliminate the possibility of intraocular infection.

The Possibility of Fluid Contamination Within Syringes in Case of Experimental Needle Contamination

PURPOSE: The present study examined the risk of intraocular infection only in cases where the injection needle was replaced when the injection needle was contaminated before intraocular injection. METHODS: Staphylococcus aureus and Staphylococcus epidermidis were cultured and smeared on the end of 30 syringe needles containing 0.1 mL normal saline. After removing only the injection needle, the normal saline in the syringes was injected onto blood agar plates and cultured. RESULTS: The culture results were positive in 21 out of 30 samples in the group smeared with Staphylococcus aureus, and in 25 out of 30 samples in the group smeared with Staphylococcus epidermidis. CONCLUSIONS: When the injection needle is contaminated, the replacement of the needle does not eliminate the possibility of intraocular infection.

Evaluation of the VIDAS CDAB Kits for the Detection of the Clostridium difficile Toxins A and B / 대한임상미생물학회지

BACKGROUND: Since the emergence of variant Clostridium difficile strains that fail to produce detectable toxin A, diagnostic kits targeted to detect toxin A only showed a considerable rate of false negative results. The aim of this study was to evaluate a toxins A and B (toxins A/B) detection kit recently marketed in Korea, and to compare toxin positive rates before and after introduction of the new kit. METHODS: The results of 5,783 toxin A assays performed during the 7-year period from 2001 through 2007 were analyzed and compared them to the toxins A/B assay data of 519 samples obtained from January to June 2008 in a university hospital. An enzyme-linked fluorescent immunoassay for toxins A/B (VIDAS C. difficile Toxin A & B, bioMerieux SA, France: VIDAS CDAB) and PCR for toxin genes A/B were performed directly in 102 stool samples from hospitalized patients. RESULTS: The positive rates of toxin A assays tended downward annually from 2001 to 2007 (16.3%, 17.8%, 13.9%, 11.4%, 13.8%, 8.2%, and 5.8%, respectively), but increased to 12.1% in 2008 after changing to the toxin A/B detection kit. The concordant rate of the VIDAS CDAB kit with the PCR method was 82.4%. Compared to the PCR method, the sensitivity and specificity of the toxin A/B kit were 60.7% and 90.5% respectively. CONCLUSION: Testing kits for C. difficile toxin A only could result in a misdiagnosis more frequently than the testing kit for toxins A/B. The sensitivity of the newly launched toxin A/B detection kit from bioMerieux SA needs to be improved, but it showed a good specificity