Impact of Infection Prevention Programs on Catheter-Associated Urinary Tract Infections Analyzed in Multicenter Study

Background@#Catheter-associated urinary tract infections (CAUTIs) account for a large proportion of healthcare-associated infections and have a significant impact on morbidity, length of hospital stay, and mortality. Adherence to the recommended infection prevention practices can effectively reduce the incidence of CAUTIs. This study aimed to assess the characteristics of CAUTIs and the efficacy of prevention programs across hospitals of various sizes. @*Methods@#Intervention programs, including training, surveillance, and monitoring, were implemented. Data on the microorganisms responsible for CAUTIs, urinary catheter utilization ratio, rate of CAUTIs per 1,000 device days, and factors associated with the use of indwelling catheters were collected from 2017 to 2019. The incidence of CAUTIs and associated data were compared between university hospitals and small- and medium-sized hospitals. @*Results@#Thirty-two hospitals participated in the study, including 21 university hospitals and 11 small- and medium-sized hospitals. The microorganisms responsible for CAUTIs and their resistance rates did not differ between the two groups. In the first quarter of 2018, the incidence rate was 2.05 infections/1,000 device-days in university hospitals and 1.44 infections/1,000 device-days in small- and medium-sized hospitals. After implementing interventions, the rate gradually decreased in the first quarter of 2019, with 1.18 infections/1,000 device-days in university hospitals and 0.79 infections/1,000 device-days in small- and medium-sized hospitals. However, by the end of the study, the infection rate increased to 1.74 infections/1,000 device-days in university hospitals and 1.80 infections/1,000 device-days in small- and medium-sized hospitals. @*Conclusion@#We implemented interventions to prevent CAUTIs and evaluated their outcomes. The incidence of these infections decreased in the initial phases of the intervention when adequate support and personnel were present. The rate of these infections may be reduced by implementing active interventions such as consistent monitoring and adherence to guidelines for preventing infections.

Changing Genotypic Distribution, Antimicrobial Susceptibilities, and Risk Factors of Urinary Tract Infection Caused by Carbapenemase-Producing Pseudomonas aeruginosa

Background@#Carbapenem-resistant Pseudomonas aeruginosa (CrPA) is a leading cause of healthcare-associated urinary tract infections (UTIs). Carbapenemase production is an important mechanism that significantly alters the efficacy of frequently used anti-pseudomonal agents. Reporting the current genotypic distribution of carbapenemase-producing P.aeruginosa (CPPA) isolates in relation to antimicrobial susceptibility, UTI risk factors, and mortality is necessary to increase the awareness and control of these strains. @*Methods@#In total, 1,652 non-duplicated P. aeruginosa strains were isolated from hospitalized patients between 2015 and 2020. Antimicrobial susceptibility, carbapenemase genotypes, risk factors for UTI, and associated mortality were analyzed. @*Results@#The prevalence of carbapenem-non-susceptible P. aeruginosa isolates showed a decreasing trend from 2015 to 2018 and then increased in the background of the emergence of New Delhi metallo-β-lactamase (NDM)-type isolates since 2019. The CPPA strains showed 100.0% non-susceptibility to all tested antibiotics, except aztreonam (94.5%) and colistin (5.9%). Carbapenems were identified as a risk and common predisposing factor for UTI (odds ratio [OR] = 1.943) and mortality (OR = 2.766). Intensive care unit (ICU) stay (OR = 2.677) and white blood cell (WBC) count (OR = 1.070) were independently associated with mortality. @*Conclusions@#The changing trend and genetic distribution of CPPA isolates emphasize the need for relentless monitoring to control further dissemination. The use of carbapenems, ICU stay, and WBC count should be considered risk factors, and aggressive antibiotic stewardship programs and monitoring may serve to prevent worse outcomes.

Comparative Genomic Analysis of Staphylococcal Cassette Chromosome mec Type V Staphylococcus aureus Strains and Estimation of the Emergence of SCCmec V Clinical Isolates in Korea

Background@#Staphylococcal cassette chromosome mec type V (SCCmec V) methicillin-resistant Staphylococcus aureus (MRSA) has been recovered from patients and livestock.Using comparative genomic analyses, we evaluated the phylogenetic emergence of SCCmec V after transmission from overseas donor strains to Korean recipient strains. @*Methods@#Sixty-three complete MRSA SCCmec V genomes (including six Korean clinical isolates) were used to construct a phylogenetic tree. Single-nucleotide polymorphisms were identified using Snippy, and a maximum-likelihood-based phylogenetic tree was constructed using RAxML. The possible emergence of the most common ancestor was estimated using BactDating. To estimate mecA horizontal gene transfer (HGT) events, Rangerdtl was applied to 818 SCCmec V strains using publicly available whole-genome data. @*Results@#The phylogenetic tree showed five major clades. German strains formed a major clade; their possible origin was traced to the 1980s. The emergence of Korean SCCmec V clinical isolates was traced to 2000–2010. mecA HGT events in Staphylococcus spp. were identified in seven strains. P7 (Hong Kong outbreak strain) served as the donor strain for two Korean sequence type (ST) 59 strains, whereas the other five recipient strains emerged from different SCCmec V donors. @*Conclusions@#Most Korean SCCmec V strains may have emerged during 2000–2010. A unique MRSA SCCmec V strain, ST72 (a Korean common type of community-associated MRSA), was also identified. The genomic dynamics of this clone with a zoonotic background should be monitored to accurately understand MRSA evolution.

Performance Evaluation of the Roche Cobas 5800 HBVand HCV Tests: Comparison of the 200 and 500 μLProtocols

Background@#Clinical management of patients infected with hepatitis B virus (HBV) or hepatitis C virus (HCV) relies on the viral load (VL). The Cobas 5800 system (Roche Diagnostics) can determine VLs in 200 and 500 µL samples, but the performance of each protocol has not been compared. We evaluated the performance of both protocols for the HBV and HCV tests. @*Methods@#Precision and linearity were verified using commercial panels. Probit analyses were used to determine limits of detection (LoDs). The results obtained with 336 samples were compared using the 200 and 500 µL protocols. Data from 6,737 retrospective HBV and 768 HCV samples were compared to estimate the effects of the different LoDs on the diagnostic results of the protocols. Correlations between protocols were tested with Spearman’s rank correlation coefficients (rho). @*Results@#The precision and linearity of both protocols were verified. The LoDs for the 200and 500 μL protocols were 6.5 and 2.7 IU/mL for HBV and 29.7 and 8.2 IU/mL for HCV,respectively. The agreement between the protocols ranged from 0.8 to 1.0. The results obtained with the HBV and HCV tests showed a strong correlation (rho = 0.994). Only 0.4% ofHBV and 0.4% of HCV test results were affected by the LoDs of the 200 μL protocol. @*Conclusions@#The Cobas 5800 200 and 500 µL protocols for the HBV DNA and HCV RNA tests demonstrated excellent performance. These findings establish the 200 µL protocol as a new option for low-volume samples, especially for pediatric and difficult-to-bleed patients.

A Case of Whole Genome Analysis of SARSCoV-2 Using Oxford Nanopore MinION System / 대한임상미생물학회지

The application of whole genome sequencing on SARS-CoV-2 viral genome is essential for our understanding of the molecular epidemiology and spread of viruses in the community. The portable whole genome sequencer MinION (Oxford Nanopore Technologies, ONT, UK) could be feasibly used in a clinical microbiology laboratory without the need of vast resources or stringent operating conditions. We used the MinION sequencer to analyze the viral genome sequence of one SARS-CoV-2 strain. In June 2020, nasopharyngeal specimen from one patient was subjected to whole-genome analysis using the nCoV-2019 sequencing protocol v2 of ARTIC using the MinION sequencer. The ONT MinKNOW software, RAMPART tool, and Genome Workbench were used. We identified 11 nucleotide variants using the Wuhan-Hu-1 isolate (NC_045512.2) as the reference sequence. There were six nucleotide variants (T265I, F924, Y3884L, P4715L, L5462, and Q6804L) in the ORF1ab region, one variant (D614G) in the S gene, one variant (Q57H) in ORF3a, one variant (P302) in the N gene, and two variants in each the 5′-UTR and 3′-UTR. In this prolonged coronavirus disease 2019 (COVID-19) pandemic season, the MinION system that operates an amplicon-based whole-genome sequencing protocol could be a rapid and reliable sequencer without the need of cumbersome viral cultivation.

Nasal Colonization of Serine Protease esp Positive Staphylococcus epidermidis Affecting Staphylococcus aureus Colonization / 대한임상미생물학회지

Background@#Staphylococcus aureus is a common colonizer of the nasal vestibule and is found in approximately 20%–30% of healthy adults, while Staphylococcus epidermidis appears to be the most frequent colonizer in all regions of the upper respiratory tract. Esp, aserine protease of S. epidermidis, was reported to inhibit S.aureus colonization. This study was performed to examine the nasal colonization of S. aureus and S. epidermidis and the presence of esp determinants. @*Methods@#Nasal swab specimens from 54 patients were cultured on blood agar plates (BAP) and selective media for S. aureus (S. aureus ID, bioMerieux, France) for the isolation of S.aureus and S. epidermidis. After 48 hours of incubation of with BAP, three or four colonies suspected of being coagulase-negative staphylococci (CNS) were identified by MALDI-TOF MS (Bruker, Germany). Polymerase chain reaction (PCR) for esp was performed on all CNS isolates identified as S. epidermidis. @*Results@#Forty-three S. epidermidis strains were isolated from 18 (33.3%) of the 54 patients.Nine (50.0%) of the 18 patients carried S. aureus, while the other nine did not. Of the 36 S. epidermidis non-carriers, 13 (36.1%) were colonized by S. aureus. All S. epidermidis strains were confirmed by PCR to have esp determinants. @*Conclusion@#S. epidermidis colonization did not affect S. aureus colonization in the nasal cavity. All S. epidermidis strains harbored the esp gene. We could not find any differences in the nasal colonization rates of S. aureus according to the presence of esp-positive S. epidermidis. Further research on the characterization of S. epidermidis in Korea is needed to understand the association between S. epidermidis and S. aureus colonization.

Nasal Colonization of Serine Protease esp Positive Staphylococcus epidermidis Affecting Staphylococcus aureus Colonization / 대한임상미생물학회지

Background@#Staphylococcus aureus is a common colonizer of the nasal vestibule and is found in approximately 20%–30% of healthy adults, while Staphylococcus epidermidis appears to be the most frequent colonizer in all regions of the upper respiratory tract. Esp, aserine protease of S. epidermidis, was reported to inhibit S.aureus colonization. This study was performed to examine the nasal colonization of S. aureus and S. epidermidis and the presence of esp determinants. @*Methods@#Nasal swab specimens from 54 patients were cultured on blood agar plates (BAP) and selective media for S. aureus (S. aureus ID, bioMerieux, France) for the isolation of S.aureus and S. epidermidis. After 48 hours of incubation of with BAP, three or four colonies suspected of being coagulase-negative staphylococci (CNS) were identified by MALDI-TOF MS (Bruker, Germany). Polymerase chain reaction (PCR) for esp was performed on all CNS isolates identified as S. epidermidis. @*Results@#Forty-three S. epidermidis strains were isolated from 18 (33.3%) of the 54 patients.Nine (50.0%) of the 18 patients carried S. aureus, while the other nine did not. Of the 36 S. epidermidis non-carriers, 13 (36.1%) were colonized by S. aureus. All S. epidermidis strains were confirmed by PCR to have esp determinants. @*Conclusion@#S. epidermidis colonization did not affect S. aureus colonization in the nasal cavity. All S. epidermidis strains harbored the esp gene. We could not find any differences in the nasal colonization rates of S. aureus according to the presence of esp-positive S. epidermidis. Further research on the characterization of S. epidermidis in Korea is needed to understand the association between S. epidermidis and S. aureus colonization.

Comparison of Three Methods with CHROMagar for Surveillance Culture of Carbapenem-Resistant Acinetobacter baumannii / 대한임상미생물학회지

Background@#Carbapenem-resistant Acinetobacter baumannii (CRAB) has emerged as an important nosocomial pathogen.The purpose of this study was to determine the effective methods for performing surveillance cultures of CRAB. @*Methods@#Nasal and rectal swabs were obtained concurrently from hospitalized intensive care unit patients colonized with CRAB. All the samples were inoculated in CHROMagar Acinetobacter medium with CR102 (CHROMagar), MacConkey agar medium supplemented with 5 µg/mL imipenem (MCA-IPM), and triptic soy broth medium supplemented with 5 µg/ mL imipenem (TSB-IPM). CRAB detection rates for each sample were compared. @*Results@#The CRAB detection rate in either one of the nasal or rectal swabs from the 37 patients tested were 89.2% (33/37) with the use of CHROMagar, 78.4% (29/37) with the use of MCA-IMP, and 86.5% (32/37) with the use of TSB-IMP. @*Conclusion@#We determined that concurrent use of both nasal and rectal swabs and CHROMagar could be an effective method for CRAB surveillance cultures.

Rapid Identification of OXA-48-like, KPC, NDM, and VIM Carbapenemase-Producing Enterobacteriaceae From Culture: Evaluation of the RESIST-4 O.K.N.V. Multiplex Lateral Flow Assay

There is an urgent need for accurate and rapid diagnostic assays capable of identifying carbapenemase-producing Enterobacteriaceae (CPE). We assessed the performance of the RESIST-4 O.K.N.V. (OKNV) assay (Coris BioConcept, Gembloux, Belgium) for the identification of oxacillinase (OXA)-48-like-, Klebsiella pneumoniae carbapenemase (KPC)-, New Delhi metallo-β-lactamase (NDM)-, and Verona integron-encoded metallo-β-lactamase (VIM)-producing Enterobacteriaceae grown on sheep blood agar (SBA) and the CHROMagar KPC medium. Sixty-five carbapenem-resistant Enterobacteriaceae (CRE) isolates with characterized carbapenemase content were used to evaluate the OKNV assay. The assay correctly identified all 30 isolates that produced one of the four targeted carbapenemase families. Additionally, it correctly identified 15 isolates that co-produced KPC and NDM, VIM and NDM or OXA-48-like and NDM, but failed to identify an NDM-1 and OXA-232 co-producing Klebsiella pneumoniae isolate. All 16 non-carbapenemase-producing CRE and four CPE isolates exhibited negative results, and no cross-reaction was observed. Overall, the sensitivity and specificity of the assay were 97.8% and 100%, respectively. The OKNV assay is an accurate and rapid assay for identifying OXA-48-like, KPC, NDM, and VIM carbapenemases produced by Enterobacteriaceae isolates cultured on both SBA and the CHROMagar KPC media in the clinical microbiology laboratory.

Seroprevalence of Anti-SARS-CoV-2 Antibodies among Outpatients in Southwestern Seoul, Korea

Serosurveillance studies reveal the actual disease burden and herd immunity level in the population. In Seoul, Korea, a cross-sectional investigation showed 0.07% anti-severe acute respiratory syndrome coronavirus-2 antibody seropositivity among 1,500 outpatients of the university hospitals. Low seroprevalence reflects well-implemented social distancing.Serosurveillance should be repeated as the pandemic progresses.

Positivity of Carbapenemase-producing Enterobacteriaceae in Patients Following Exposure within Long-term Care Facilities in Seoul, Korea

Background@#Carbapenemase-producing Enterobacteriaceae (CPE) are emerging as a worldwide threat. Long-term care facilities (LTCFs) are considered a reservoir for CPE and play a central role in transmission to acute care hospitals. We investigated the CPE positivity in patients exposed to CPE in LTCFs. Furthermore, we analyzed the CPE positivity rates in the environment exposed to CPE. @*Methods@#We collected rectal swab specimens from patients residing in LTCFs who were exposed to CPE. Environmental sampling was performed by infection control practitioners from sites classified as patient private space, common space in the patient room, common space other than patient rooms, and nursing station. Each sample was cultured on a Chrom KlebsiellaF pneumoniae carbapenemase (KPC) agar for CPE screening. The positive isolates were subjected to a polymerase chain reaction to identify the presence of bla KPC , bla VIM , bla IMP , bla OXA-48 , and bla NDM and determine CPE genotype. @*Results@#From 65 index cases, a total of 24 hospitals and 481 patients were enrolled; 414 patients who had resided in the same patient room as a patient with confirmed CPE and 67 patients who were newly admitted to that patient room. A total of 117 (24.3%) patients were positive for CPE among which 93 (22.5%, 93/414) were already admitted patients and 24 (35.8%, 24/67) were newly admitted patients. A total of 163 CPEs were detected and K. pneumoniae (n = 104, 63.8%) was the most common bacteria followed by Escherichia coli (n = 43, 26.4%) and Citrobacter koseri (n = 11, 6.7%). Environmental sampling was performed in 24 hospitals and 604 sites. A total of 12 sites (2.0%) were positive for CPE and sink in the nursing station (n = 6, 4.2%) was the most contaminated space. @*Conclusion@#CPE colonization rates in patients exposed to CPE in LTCFs were higher than those found in acute care hospitals. Proper infection control measures for detecting and reducing CPE colonization in patients residing in LTCFs are required. Newly admitted patients could also be carriers; therefore, infection control for newly admitted patients also needs to be thorough.

Serotype Distribution and Antimicrobial Resistance of Invasive and Noninvasive Streptococcus pneumoniae Isolates in Korea between 2014 and 2016

BACKGROUND: Several factors contribute to differences in Streptococcus pneumoniae serotype distribution. We investigated the serotype distribution and antimicrobial resistance of S. pneumoniae isolated between 2014 and 2016 in Korea. METHODS: We collected a total of 1,855 S. pneumoniae isolates from 44 hospitals between May 2014 and May 2016, and analyzed the serotypes by sequential multiplex PCR. We investigated the distribution of each serotype by patient age, source of the clinical specimen, and antimicrobial resistance pattern. RESULTS: The most common serotypes were 11A (10.1%), followed by 19A (8.8%), 3 (8.5%), 34 (8.1%), 23A (7.3%), and 35B (6.2%). The major invasive serotypes were 3 (12.6%), 19A (7.8%), 34 (7.8%), 10A (6.8%), and 11A (6.8%). Serotypes 10A, 15B, 19A, and 12F were more common in patients ≤5 years old, while serotype 3 was more common in patients ≥65 years old compared with the other age groups. The coverage rates of pneumococcal conjugate vaccine (PCV)7, PCV10, PCV13, and pneumococcal polysaccharide vaccine 23 were 11.8%, 12.12%, 33.3%, and 53.6%, respectively. Of the 1,855 isolates, 857 (46.2%) were multi-drug resistant (MDR), with serotypes 11A and 19A predominant among the MDR strains. The resistance rates against penicillin, cefotaxime, and levofloxacin were 22.8%, 12.5%, and 9.4%, respectively. CONCLUSIONS: There were significant changes in the major S. pneumoniae serotypes in the community. Non-PCV13 serotypes increased in patients ≤5 years old following the introduction of national immunization programs with the 10- and 13-polyvalent vaccines.

Performance of HemosIL ReadiPlasTin, a Liquid Reagent for Prothrombin Time Measurement

BACKGROUND: Prothrombin time (PT) measurement is an important test for screening blood coagulation disorders and monitoring anticoagulant therapy. In this study, we evaluated the analytical performance of HemosIL ReadiPlasTin (Instrumentation Laboratory, USA), a liquid reagent for PT measurement. METHODS: The precision of HemosIL ReadiPlasTin was evaluated according to the Clinical and Laboratory Standards Institute (CLSI) EP5-A3 guidelines. Further, comparison with HemosIL RecombiPlasTin 2G (Instrumentation Laboratory, USA) was made according to the CLSI EP9-A3 guidelines. The reference intervals were established according to the CLSI C28-A3 guidelines. RESULTS: The coefficient of variation values for repeatability and total imprecision at two levels of control materials were lower than 1.1% and 3.4%, respectively. The performance of HemosIL ReadiPlasTin was comparable to that of HemosIL RecombiPlasTin 2G, with a high correlation (r=0.996). The reference interval for normal subjects was 10.4–13.3 seconds. CONCLUSIONS: HemosIL ReadiPlasTin showed an acceptable degree of imprecision and its performance showed high correlation with that of a conventional reagent. Therefore, it is expected to be useful for PT measurement in clinical laboratories.

Evaluation of the Real-Q RV Detection Kit for the Identification of Viruses That Result in Respiratory Infections

Viral respiratory infections are one of the most common infections worldwide. It is important to detect the virus early and precisely. In this study, we evaluated the limit of detection (LoD) and usefulness of the Real-Q RV Detection kit (BioSewoom, Seoul, Korea). We measured the LoD of the Real-Q RV Detection kit using 10 strains of standard viruses. We then compared the detection results by the Allplex Respiratory Panel Assay kit (Seegene, Seoul, Korea) using 123 clinical specimens. The discrepant results were confirmed by sequencing. Among the 10 standard viruses, the LoD of human rhinovirus (HRV) was the lowest and that of parainfluenza virus 2 and 3 was relatively high as detected by Real-Q RV Detection kit. Agreements of the two kits ranged from 95.9% to 100%. Three specimens detected negative by the Allplex Respiratory Panel kit were detected as adenovirus (AdV) by the Real-Q RV Detection kit and were confirmed by sequencing. Similarly, a specimen detected negative by the Allplex Respiratory Panel kit was detected as HRV by the Real-Q RV Detection kit and was confirmed by sequencing. A specimen detected as human enterovirus by the Allplex Respiratory Panel kit was detected as HRV by the Real-Q RV Detection kit and was confirmed by sequencing. Real-Q RV Detection kit showed good diagnostic performance and can be useful for detecting major viruses that cause respiratory infections.

Evaluation of a New Multiplex Real-Time PCR Assay for Detecting Gastroenteritis-Causing Viruses in Stool Samples

BACKGROUND: Diarrhea has been the second leading cause of death among children under the age of five, and the rapid and accurate pathogen diagnosis in patients with diarrhea is crucial for reducing morbidity and mortality. A newly developed one-step multiplex real-time PCR assay, the Allplex GI-Virus Assay, was evaluated for its ability to detect six diarrhea-causing viruses (rotavirus, norovirus genogroup I (GI) and genogroup II (GII), enteric adenovirus, astrovirus, and sapovirus) in stool samples. METHODS: The performance of the Allplex assay was compared with those of another multiplex PCR assay (Seeplex Diarrhea-V Ace Detection) and genotyping by sequencing, using 446 stool samples from patients with acute gastroenteritis. RESULTS: The overall agreement rates between the results of the Allplex and Seeplex assays were 98.7% for rotavirus, 99.1% for norovirus GI, 93.3% for norovirus GII, 98.0% for adenovirus, and 99.6% for astrovirus. The overall agreement rates between the Allplex assay and genotyping were 99.1% for rotavirus, 99.1% for norovirus GI, 98.7% for norovirus GII, 89.7% for adenovirus, 98.2% for astrovirus, and 99.8% for sapovirus. In addition, eight rotavirus genotypes, three norovirus GI genotypes, four norovirus GII genotypes, eight adenovirus genotypes, two astrovirus genotypes, and two sapovirus genotypes were detected. CONCLUSIONS: The Allplex assay showed high agreement with Seeplex and genotyping results, and was able to additionally detect sapoviruses. The Allplex assay could be useful in identifying viral gastrointestinal infections in patients with acute gastroenteritis symptoms.

Comparison of the Luminex xTAG Respiratory Viral Panel Fast v2 Assay With Anyplex II RV16 Detection Kit and AdvanSure RV Real-Time RT-PCR Assay for the Detection of Respiratory Viruses

BACKGROUND: The accurate and rapid identification of the causative viruses is important for the timely diagnosis and management of respiratory infections. Multiplex molecular diagnostic techniques have been widely adopted to detect respiratory viruses. We compared the results of a newly upgraded, multiplex, molecular bead-based respiratory viral panel (RVP) assay with the results of Anyplex II RV16 detection kit and AdvanSure RV real-time RT-PCR assay. METHODS: We tested 254 respiratory specimens and cultured viral strains using the Luminex xTAG RVP Fast v2 assay (Luminex Molecular Diagnostics, Canada) and Anyplex II RV16 detection kit and compared the results. Specimens showing discordant results between the two assays were tested with a AdvanSure RV real-time RT-PCR assay. RESULTS: Of the 254 respiratory specimens, there was total agreement in the results between the xTAG RVP Fast v2 assay and the other real-time PCR assay in 94.1–100% of the specimens. The agreement levels were relatively low (94.1–97.6%) for specimens of adenovirus, coronavirus NL63, and parainfluenza type 3. In comparison to the other assay, the xTAG RVP Fast v2 assay detected a higher number of parainfluenza type 3 (4 cases) and metapneumovirus (9 cases). CONCLUSIONS: The xTAG RVP Fast v2 assay showed comparable capabilities compared with the other assays; it will be useful for identifying respiratory viral infections in patients with respiratory symptoms. Clinicians should be aware of the characteristics of the assays they use, since different assays show different detectability for each virus.

Disk Carbapenemase Test for the Rapid Detection of KPC-, NDM-, and Other Metallo-β-Lactamase-Producing Gram-Negative Bacilli

BACKGROUND: Rapid detection of carbapenemase-producing gram-negative bacilli (GNB) is required for optimal treatment of infected patients. We developed and assessed a new disk carbapenemase test (DCT). METHODS: Paper disks containing 0.3 mg of imipenem and bromothymol blue indicator were developed, and the performance of the DCT were evaluated by using 742 strains of GNB with or without carbapenemases. RESULTS: The paper disks were simple to prepare, and the dried disks were stable at -20℃ and at 4℃. The DCT detected 212 of 215 strains (98.6% sensitivity with 95% confidence interval [CI] 96.0-99.5%) of GNB with known class A (KPC and Sme) and class B (NDM, IMP, VIM, and SIM) carbapenemases within 60 min, but failed to detect GES-5 carbapenemase. The DCT also detected all two Escherichia coli isolates with OXA-48, but failed to detect GNB with OXA-232, and other OXA carbapenemases. The DCT showed 100% specificity (95% CI, 99.2-100%) in the test of 448 imipenem-nonsusceptible, but carbapenemase genes not tested, clinical isolates of GNB. CONCLUSIONS: The DCT is simple and can be easily performed, even in small laboratories, for the rapid detection of GNB with KPC, NDM and the majority of IMP, VIM, and SIM carbapenemases.

Prevalence and Molecular Characteristics of Carbapenemase-Producing Enterobacteriaceae From Five Hospitals in Korea

BACKGROUND: The emergence of carbapenemase-producing Enterobacteriaceae (CPE) represents a major clinical problem because these bacteria are resistant to most antibiotics. CPE remain relatively uncommon in Korea. We report the prevalence, clinical characteristics, and molecular epidemiology of CPE isolates collected from five university hospitals in Korea. METHODS: Between January and December 2015, 393 non-duplicated isolates that were nonsusceptible to ertapenem were analyzed. Production of carbapenemase, extended-spectrum β-lactamase, and AmpC β-lactamase was determined by genotypic tests. Antimicrobial susceptibility profiles were determined by using an Etest. Clonality of Klebsiella pneumoniae carbapenemase (KPC)-2-producing and oxacillinase (OXA)-232-producing Klebsiella pneumoniae isolates was determined by pulsed-field gel electrophoresis (PFGE). RESULTS: Of the 393 isolates tested, 79 (20.1%) were CPE. Of these 79 isolates, 47 (59.5%) harbored the bla(OXA-232) gene while the remaining isolates carried genes bla(KPC-2) (n=27), bla(IMP-1) (n=4), and bla(NDM-1) (n=1). Among the 24 KPC-2 K. pneumoniae isolates from hospital B, 100% were resistant to carbapenems, 8% to colistin, and 0% to tigecycline. Among the 45 OXA-232 K. pneumoniae at hospital C, 95% were resistant to ertapenem, 68% to imipenem, 95% to meropenem, 10% to colistin, and 24% to tigecycline. PFGE analysis revealed a unique pattern for KPC-2 K. pneumoniae and identified 30 isolates belonging to the dominant pulsotypes (PT)1 and PT2 among 41 OXA-232 K. pneumoniae isolates. CONCLUSIONS: CPE strains are present in Korea, with the majority of K. pneumoniae isolates producing OXA-232 and KPC-2. The prevalence and predominant genotypes of CPE show hospital-specific differences.

In Vitro Synergistic Effects of Antimicrobial Combinations on Extensively Drug-Resistant Pseudomonas aeruginosa and Acinetobacter baumannii Isolates

BACKGROUND: Extensively drug-resistant (XDR) Pseudomonas aeruginosa and Acinetobacter baumannii are a threat to hospitalized patients. We evaluated the effects of antimicrobial combinations on XDR P. aeruginosa and A. baumannii isolates. METHODS: P. aeruginosa and A. baumannii isolates, which were resistant to all antibiotics except colistin (CL), were collected from eight hospitals in Korea. Genes encoding metallo-beta-lactamases (MBLs) and OXA carbapenemases were detected by PCR in eight P. aeruginosa and 30 A. baumannii isolates. In vitro synergy of antimicrobial combinations was tested by using the checkerboard method. RESULTS: Minimum inhibitory concentrations of beta-lactams, aminoglycosides, and fluoroquinolones were very high, while that of CL was low for majority of XDR P. aeruginosa and A. baumannii isolates. Antimicrobial combinations including Imipenem (IPM)-CL, ceftazidime (CAZ)-CL, and rifampin (RIF)-CL exerted only additive/indifferent effects on majority of XDR P. aeruginosa isolates. Proportions of XDR A. baumannii isolates that showed synergistic and additive/indifferent inhibition after treatment with antimicrobial combinations used are as follows: IPM-ampicillin-sulbactam (AMS), 17% and 80% isolates, respectively; IPM-rifampin (RIF), 13% and 81% isolates, respectively; IPM-CL, 13% and 87% isolates, respectively; and RIF-COL, 20% and 73% isolates, respectively. Significant proportion (19%) of XDR P. aeruginosa isolates produced MBLs, and majority (82%) of A. baumannii isolates produced either MBLs or OXA-23. CONCLUSIONS: Our results suggest that combinations of IPM-AMS, IPM-RIF, IPM-CL, and RIF-CL are more useful than individual drugs for treating 13-20% of XDR A. baumannii infections.

Detection of Rotavirus from the Inner Surfaces of Domestic Refrigerators

BACKGROUND: Rotavirus is the leading cause of acute viral gastroenteritis, particularly in children, and is transmitted through the fecal-to-oral route by contaminated food or the environment. This study examined the contamination of the inner surfaces of domestic refrigerators with pathogens causing gastroenteritis. METHODS: Swab specimens from shelf surfaces of freezers and refrigerators were collected from 10 domestic refrigerators. Multiplex PCR for bacterial and viral pathogens causing acute gastroenteritis was performed. The VP7 and VP4 genes of rotavirus were amplified and then analyzed by DNA sequencing. RESULTS: Rotavirus was detected in five domestic refrigerators in the same apartment complex. All rotavirus samples showed the G1 genotype and the same DNA sequences. No pathogens causing acute gastroenteritis were identified in the other five domestic refrigerators. CONCLUSIONS: The inner surfaces of domestic refrigerators can be contaminated with pathogens causing acute gastroenteritis, such as rotavirus. Attention should be given to the hygiene of refrigerators. To estimate the contamination or hygienic status for food storage, testing for viral pathogens combined with ordinary bacterial cultures may be necessary.