Soon Deok Park

The Prevalence of Vaginal Microorganisms in Pregnant Women with Preterm Labor and Preterm Birth

Background To investigate the risk factors for vaginal infections and antimicrobial susceptibilities of vaginal microorganisms among women who experienced preterm birth (PTB), we compared the prevalence of vaginal microorganisms between women who experienced preterm labor (PTL) without preterm delivery and spontaneous PTB. Methods Vaginal swab specimens from 126 pregnant women who experienced PTL were tested for group B streptococcus (GBS), Mycoplasma hominis, Mycoplasma genitalium, Ureaplasma urealyticum, Chlamydia trachomatis, Trichomonas vaginalis, Neisseria gonorrhoeae, Treponema pallidum, herpes simplex virus (HSV) I and II, and bacterial vaginosis. A control group of 91 pregnant women was tested for GBS. Antimicrobial susceptibility tests were performed for GBS, M. hominis, and U. urealyticum. Results The overall detection rates for each microorganism were: U. urealyticum, 62.7%; M. hominis, 12.7%; GBS, 7.9%; C. trachomatis, 2.4%; and HSV type II, 0.8%. The colonization rate of GBS in control group was 17.6%. The prevalence of GBS, M. hominis, and U. urealyticum in PTL without preterm delivery and spontaneous PTB were 3.8% and 8.7% (relative risk [RR], 2.26), 3.8% and 17.3% (RR, 4.52), and 53.8% and 60.9% (RR, 1.13), respectively, showing no significant difference between the 2 groups. The detection rate of M. hominis by PCR was higher than that by culture method (11.1% vs. 4.0%, P=0.010). The detection rates of U. urealyticum by PCR and culture method were 16.7% and 57.1%, respectively. Conclusions There was no significant difference in the prevalence of GBS, M. hominis, and U. urealyticum between the spontaneous PTB and PTL without preterm delivery groups.

Multiplex Real-Time PCR Assay for Rapid Detection of Methicillin-Resistant Staphylococci Directly from Positive Blood Cultures

ABSTRACT Methicillin-resistant Staphylococcus aureus (MRSA) is the most prevalent cause of bloodstream infections (BSIs) and is recognized as a major nosocomial pathogen. This study aimed to evaluate a newly designed multiplex real-time PCR assay capable of the simultaneous detection of mecA, S. aureus, and coagulase-negative staphylococci (CoNS) in blood culture specimens. The Real-MRSA and Real-MRCoNS multiplex real-time PCR assays (M&D, Republic of Korea) use the TaqMan probes 16S rRNA for Staphylococcus spp., the nuc gene for S. aureus, and the mecA gene for methicillin resistance. The detection limit of the multiplex real-time PCR assay was 103 CFU/ml per PCR for each gene target. The multiplex real-time PCR assay was evaluated using 118 clinical isolates from various specimen types and a total of 350 positive blood cultures from a continuous monitoring blood culture system. The results obtained with the multiplex real-time PCR assay for the three targets were in agreement with those of conventional identification and susceptibility testing methods except for one organism. Of 350 positive bottle cultures, the sensitivities of the multiplex real-time PCR kit were 100% (166/166 cultures), 97.2% (35/36 cultures), and 99.2% (117/118 cultures) for the 16S rRNA, nuc, and mecA genes, respectively, and the specificities for all three targets were 100%. The Real-MRSA and Real-MRCoNS multiplex real-time PCR assays are very useful for the rapid accurate diagnosis of staphylococcal BSIs. In addition, the Real-MRSA and Real-MRCoNS multiplex real-time PCR assays could have an important impact on the choice of appropriate antimicrobial therapy, based on detection of the mecA gene.

Prevalence and resistance patterns of extended-spectrum and AmpC β-lactamase in Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Salmonella serovar Stanley in a Korean tertiary hospital

Park SD, Uh Y, Lee G, Lim K, Kim JB, Jeong SH. Prevalence and resistance patterns of extended‐spectrum and AmpC β‐lactamase in Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Salmonella serovar Stanley in a Korean tertiary hospital. APMIS 2010; 118: 801–8.

PCR-Reverse Blot Hybridization Assay for Screening and Identification of Pathogens in Sepsis

ABSTRACT Rapid and accurate identification of the pathogens involved in bloodstream infections is crucial for the prompt initiation of appropriate therapy, as this can decrease morbidity and mortality rates. A PCR-reverse blot hybridization assay for sepsis, the reverse blot hybridization assay (REBA) Sepsis-ID test, was developed; it uses pan-probes to distinguish Gram-positive and -negative bacteria and fungi. In addition, the assay was designed to identify bacteria and fungi using six genus-specific and 13 species-specific probes; it uses additional probes for antibiotic resistance genes, i.e., the mecA gene of methicillin-resistant Staphylococcus aureus (MRSA) and the vanA and vanB genes of vancomycin-resistant enterococci (VRE). The REBA Sepsis-ID test successfully identified clinical isolates and blood culture samples as containing Gram-positive bacteria, Gram-negative bacteria, or fungi. The results matched those obtained with conventional microbiological methods. For the REBA Sepsis-ID test, of the 115 blood culture samples tested, 47 (40.8%) and 49 (42.6%) samples were identified to the species and genus levels, respectively, and the remaining 19 samples (16.5%), which included five Gram-positive rods, were identified as Gram-positive bacteria, Gram-negative bacteria, or fungi. The antibiotic resistances of the MRSA and VRE strains were identified using both conventional microbiological methods and the REBA Sepsis-ID test. In conclusion, the REBA Sepsis-ID test developed for this study is a fast and reliable test for the identification of Gram-positive bacteria, Gram-negative bacteria, fungi, and antibiotic resistance genes (including mecA for MRSA and the vanA and vanB genes for VRE) in bloodstream infections.

Rhodococcus erythropolis septicaemia in a patient with acute lymphocytic leukaemia

Rhodococcus erythropolis rarely causes infection in humans. We report the second case of R. erythropolis septicaemia in a 7-year-old child. However, to our knowledge it is the first case in a patient with acute lymphocytic leukaemia who had been undergoing chemotherapy. The identification was performed using 16S rRNA gene sequencing. Even though R. erythropolis is rarely associated with human infections, it should be considered as a potential causative agent of bacteraemia, rather than overlooked as a contaminant.

Evaluation of PCR-reverse blot hybridization assay, REBA Sepsis-ID test, for simultaneous identification of bacterial pathogens and mecA and van genes from blood culture bottles.

Background The aim of this study was to evaluate a newly developed PCR-based reverse blot hybridization assay (PCR-REBA), REBA Sepsis-ID (M&D, Wonju, Korea), to rapidly detect the presence of bacteremia and antimicrobial resistance gene in blood culture samples. Methods One thousand four hundred consecutive blood culture samples from patients with a delta neutrophil index greater than 2.7% were selected from March to July in 2013. Three hundred positive and 1,100 negative for bacterial growth in blood culture bottles samples were tested by conventional and real-time PCR-REBA, respectively. Results The overall agreement between the conventional identification test and the REBA Sepsis-ID test was 95.3% (286/300). Agreement for gram-positive bacteria, gram-negative bacteria, fungi, and polymicrobials was 94.5% (190/201), 97.3% (71/73), 100% (14/14), and 91.7% (11/12), respectively. The detection rate of the mecA gene from methicillin-resistant Staphylococcus isolates was 97.8% (90/92). The vanA gene was detected in one blood culture sample from which vancomycin-resistant Enterococcus was isolated. When the cycle threshold for real-time PCR was defined as 30.0, 2.4% (26/1,100) of negative blood culture samples tested positive by real-time PCR. Conclusions The REBA Sepsis-ID test is capable of simultaneously and quickly detecting both causative agents and antimicrobial resistance genes, such as mecA and van, in blood culture positive samples.

Performance of PCR-REBA assay for screening and identifying pathogens directly in whole blood of patients with suspected sepsis.

Rapid and accurate identification of a broad range of bacterial and fungal pathogens is the key to successful management of patients with bloodstream infections (BSIs). The aim of this study was to evaluate the diagnostic performance of PCR‐REBA Sepsis‐ID test for the detection of BSIs pathogens.

Real-time PCR TaqMan assay for rapid screening of bloodstream infection

BackgroundSepsis is one of the main causes of mortality and morbidity. The rapid detection of pathogens in blood of septic patients is essential for adequate antimicrobial therapy and better prognosis. This study aimed to accelerate the detection and discrimination of Gram-positive (GP) and Gram-negative (GN) bacteria and Candida species in blood culture samples by molecular methods.MethodsThe Real-GP®, -GN®, and -CAN® real-time PCR kit (M&D, Wonju, Republic of Korea) assays use the TaqMan probes for detecting pan-GP, pan-GN, and pan-Candida species, respectively. The diagnostic performances of the real-time PCR kits were evaluated with 115 clinical isolates, 256 positive and 200 negative blood culture bottle samples, and the data were compared to results obtained from conventional blood culture.ResultsEighty-seven reference strains and 115 clinical isolates were correctly identified with specific probes corresponding to GP-bacteria, GN-bacteria and Candida, respectively. The overall sensitivity and specificity of the real-time PCR kit with blood culture samples were 99.6% and 89.5%, respectively.ConclusionsThe Real-GP®, -GN®, and -CAN® real-time PCR kits could be useful tools for the rapid and accurate screening of bloodstream infections (BSIs).

Factors Influencing the False Positive Signals of Continuous Monitoring Blood Culture System

respectively. The false positive rates of CMBCS sig- nals according to BDA, BDN, BSA, and BSN were 0.6%, 0.1%, 0.1%, and 0.1%, respectively. The blood volume, detection time, time interval between admis- sion and test, C-reactive protein concentration, leuko- cyte count, delta neutrophil index, and mean perox- idase index showed statistically significant differences between the two groups. Conclusion: There were no variables with diagnostic sensitivity and specificity for discriminating the two groups. Therefore, analysis of bacterial growth curves produced by CMBCS is needed for early and effec- tive detection of false positive signals. (Ann Clin Microbiol 2014;17:58-64)

Macrolide resistance of Mycoplasma pneumoniae and its detection rate by real-time PCR in primary and tertiary care hospitals.

Background This study aimed to evaluate the prevalence of Mycoplasma pneumoniae in primary and tertiary care hospitals and its macrolide resistance rate. Methods Nasopharyngeal swabs were collected from 195 pediatric patients in primary and tertiary care hospitals from October to November 2010. The AccuPower MP real-time PCR kit (Bioneer, Korea) was used for the detection of M. pneumoniae. Direct amplicon sequencing was performed to detect point mutations conferring resistance to macrolides in the 23S rRNA gene. Results Among the 195 specimens, 17 (8.7%) were M. pneumoniae positive, and 3 of the strains (17.6%) obtained from these 17 specimens displayed the A2063G mutation in 23S rRNA. Three macrolide-resistant M. pneumoniae isolates were isolated from patients hospitalized at the primary care hospital. The positive rates of M. pneumoniae for the primary and tertiary care hospitals were 12.1% (15/124) and 2.8% (2/71), respectively (P=0.033). Conclusions The positive rate of M. pneumoniae in the primary care hospital was higher than that in the tertiary care hospital. Simultaneous detection of M. pneumoniae and macrolide-resistant mutation genes in the 23S rRNA by real-time PCR is needed for rapid diagnosis and therapy of M. pneumoniae infections.