Rinsho Biseibutsu Jinsoku Shindan Kenkyukai shi = JARMAM : Journal of the Association for Rapid Method and Automation in Microbiology最新文献

Recently, mass spectrometers based on MALDI-TOF MS, which can rapidly identify microorganisms, have become widely used, contributing to the proper use of antimicrobial agents and diagnosis of infectious diseases through rapid reporting of bacterial species. We had the opportunity to evaluate the performance of the I-dOne, a microorganism identification system using the ATR-FTIR method. A total of 174 strains, 78 of 11 Grampositive bacteria and 96 of 12 Gram-negative bacteria, registered in the I-dOne database were used. The strains were identified using the mass spectrometer MALDI Biotyper (Bruker Japan Inc.) and compared with the I-dOne identification results. The identification agreement rate was 73.3% (255 out of 348 shares), including Gram-positive bacteria and Gram-negative bacteria. I-dOne is expected to improve its identification accuracy through software updates and database additions and improvements.

For Clostridioides difficile infections, highly sensitive rapid diagnostic test kits are necessary for prompt diagnose and infection control. In this study, we evaluated "Quick Chaser CD GDH/TOX" (evaluation kit), a rapid diagnostic kit for C. difficile, using 65 clinical stool specimens, comparing with GE test immunochromato-CD GDH/TOX "Nissui" (GE test) and TECHLAB C. DIFF QUIK CHEK COMPLETE (QUIK CHEK). The results of the evaluation kit showed a high concordance rate; 100% the positive concordance rate (31/31) and 97.1% the negative concordance rate (33/34) of GDH, 94.1% the positive concordance rate (16/17) and 97.9% the negative concordance rate (47/48) of toxin against GE test, respectively. Also 96.9% the positive concordance rate (31/32) and 97.0% the negative concordance rate (32/33) of GDH, 100% the positive concordance rate (12/12) and 90.6% the negative concordance rate (48/53) of toxin against QUIK CHEK, respectively. Additionally, comparison of discrepancy cases between kits based on Nucleic Acid Amplification test, one false negative each for GDH and toxin in the evaluation kit, two false negatives for GDH and one false negative for toxin in the GE test, one false negative for GDH and six false negatives for toxin in QUIK CHEK, and no false positive cases were observed. Therefore, the detection sensitivity of GDH and toxin of the evaluation kit was equivalent to that of two types of comparative kits.

Bacteremia can easily become severe, and it is necessary to start appropriate treatment quickly before it progresses to sepsis. In this study, we investigated a method using antibiotic discs to quickly report antibiotic resistance information for bacteremia caused by gramnegative bacilli, such as Enterobacterales, which require careful selection of appropriate antibiotics due to their tendency to cause severe illness. In cases of bacteremia caused by ESBL and AmpC-producing bacteria, reports of suspected antibiotic resistance mechanisms were made within a few hours after disk placement, allowing for the rapid modification of antimicrobial therapy, thereby contributing to the treatment. This method is considered highly beneficial as it does not require special equipment and is a cost-effective approach. However, as this method is different from the conventional disk diffusion method, and since some cases showed susceptible inhibition zone diameters for antibiotics considered to have intrinsic resistance, further investigation is necessary for its use in determining susceptibility.

Clostridioides difficile is the most common anaerobic bacterium that causes healthcare-associated infections, and prompt diagnosis and infection control are important because it causes C. difficile infection (CDI). In this evaluation, the C. difficile nucleic acid detection reagent, Smart Gene CD Toxin B (Mizuho Medy Co., Ltd., hereinafter referred to as the "evaluation reagent") was evaluated for its clinical performance in comparison with real-time PCR and toxigenic culture (TC). Measurement of evaluation reagents and real-time PCR were performed on 157 residual stool specimens from suspected CDI patients. For TC, stool culture was performed, and colonies in which C. difficile was identified by a mass spectrometer (MALDI Biotyper) were checked for toxin production using a rapid antigen diagnostic kit. The results of the evaluation reagents showed a high concordance rate; 100% sensitivity (81/81) and 100% specificity (76/76) with real-time PCR, 89.8% sensitivity (79/88), and 97.1% specificity (67/69) with TC. The evaluation reagent enables a simple nucleic acid amplification test (NAAT) in a short time and is thought to be useful in CDI treatment, which requires rapid diagnosis and infection control.

Frequent mutations of SARS-CoV-2 change the strain more transmissible, leading to the pandemic in worldwide. We detected Y453F substitution on Omicron strain, isolated from a Japanese patient in July 2022. While Y453F substitution was identified B1.1.298 lineage in Netherlands and Denmark in 2020, the substitution has not been reported in Omicron strain especially in Japan. Y453F substitution is associated with higher viral infectivity because it is sited in the receptor-binding domain (RBD), and Y453F substitution contributes to increase binding affinity to angiotensin converting enzyme 2 (ACE2). Additionally, Y453F substitution has been reported to escape human leukocyte antigen (HLA), which is known to recognize non-self-antigens in virus-infected cells as cellular immunity, so it should be closely monitored.

Yersinia enterocolitica is a causative agent of food poisoning and has been isolated from pork and stream water, causing Yersinia enterocolitica in humans. The bacterium is divided into multiple serotypes and biotypes, among which serotypes O3 and O8 and biotypes 1B, 3, and 4 are frequently isolated in Japan. Biotype 3 can be classified as [VP+, Suc+], [VP-, Suc+], [VP-, Suc-] based on the biochemical properties. Among them, [O3, 3, VP-, Suc-] has been reported to be identified as Yersinia kristensenii in a simple identification kit. An increasing number of facilities in the field of microbiological testing are currently using mass spectrometers to identify species of microorganisms. However, there are many facilities where mass spectrometers have not yet been installed and microbial identification and susceptibility testing devices are used to identify bacterial species. No reports have described how the [O3, 3, VP-, Suc-] type, which is identified as Y. kristensenii in the simple identification kit, is identified by the microbial identification and susceptibility testing devices. In this study, 15 strains of Y. enterocolitica, which were previously isolated, serotyped, and biotyped from fecal culture tests at our hospital, were analyzed to see how these strains were identified in RAISUS S4, Microscan WalkAway, VITEK2 Blue, and BD Phoenix. [O3, 3, VP-, Suc-] was identified as Y. kristensenii in RAISUS S4, Microscan WalkAway, and VITEK2 Blue and as Y. enterocolitica in BD Phoenix. [O3, 3, VP-, Suc+], [O3, 4] and [O8, 1B] were identified as Y. enterocolitica. Therefore, when a sample was identified as Y. kristensenii by RAISUS S4, Microscan WalkAway, or VITEK2 Blue, the possibility that it was actually [O3, 3, VP-, Suc-] could not be ruled out. The possibility of Y. enterocolitica should be informed to attending physicians.

In this study, we examined the accuracy and rapidity of drug susceptibility determination using clinical isolates of MRSA with the fully automated rapid identification susceptibility testing system RAISUS S4. Ninety eight MRSA strains were used and the time until methicillin resistance was determined was analyzed by both of the standard method (18-hr method) and the rapid method. Five strains (5.1%) were determined to be methicillin-sensitive in MPIPC by rapid method only while all strains were determined to be resistant in CFX. The average methicillin resistance determination time was 7.0/5.0 hr for MPIPC, 6.3/5.0 hr for CFX, and 6.3/5.0 hr for the combination of MPIPC and CFX by the standard/rapid method, with the rapid method being significantly shorter (Wilcoxon's signed rank sum test, p<0.01). Strains determined to be methicillin-sensitive by MPIPC tended to have a longer time to methicillin resistance by the standard method, but this effect was much less pronounced for the rapid method using CFX. Methicillin resistance determination by the rapid method using RAISUS S4 enables rapid detection of MRSA without false-susceptible results, which may lead to early and appropriate treatment.

Methicillin-resistant Staphylococcus aureus (MRSA) strains showing POT type 106-77-113 have been associated with USA300. Additionally, many strains produce Panton-Valentine Leukocidin (PVL). Until 2018, 106-77-113 was the most dominant POT-type PVL-producing bacteria isolated in our hospital; however, in 2018, one strain with POT type 106-255-121 was isolated, and thereafter, since 2019, an increasing trend towards isolation of this strain has been observed. In this study, we compared two PVL-producing strains detected in skin infections-derived materials from outpatients during the three-year period between 2019 and 2021 through genetic analysis using next-generation sequencers. Eight, each of POT types 106-77-113 (POT-A) and 106-255-121 (POT-B), strains were included in this study, and PVL productivity, drug susceptibility, multi-locus sequencing typing (MLST), and resistance genes and virulence genes were detected. Both the groups shared the same MLST profile (3-3-1-1-4-4-3), but a single nucleotide mutation of ARCC was detected in POT-B type strain, which was determined to be similar to ST 8 of POT-A and POT-B type strains. Only POT-B type strains harbored aac(6')-aph(2″) and erm(A) genes, consistent with the results of drug susceptibility tests. All the strains were resistant to GM and CAM and were positive to D-zone test. On the other hand, the POT-A strains were sensitive to GM, and 7 of 8 strains were sensitive to CLDM and MINO. However, one POT-A type strain was found to harbor erm(C), tet(K), and tet(M) genes and was resistant to CAM, CLDM, and MINO. Both groups of isolates harbored 17 genes including ACME, lukF-PV, and LukS-PV, and no difference in pathogenicity was observed. In our hospital, one strain of POT type 106-255-121 was isolated for the first time in 2018, and the number of isolates of this type has been increasing since then. The present study confirms that POT type 106-255-121 strains have the same virulence as POT type 106-77-113 strains have and have also acquired a drug resistance gene.

We compared rapid antigen detection kits widely used for the rapid diagnosis of group A streptococcal pharyngitis, evaluating their minimum detection sensitivity and operability in five levels. Five kits based on the immunochromatographic method were used: ImunoAce Strep A (Tauns), ImunoAce Strep A Neo (Tauns), Quick Navi-StrepA2 (Denka), Quick Vue Dipstick Strep A (SB Bioscience) and RapidTesta Strep A (SEKISUI MEDICAL). Thirteen strains were tested: 10 clinical isolates of Streptococcus pyogenes, 2 strains of Streptococcus dysgalactiae subsp. equisimilis (SDSE), and S. pyogenes ATCC 19615. All kits had the same or higher minimum detection sensitivity than previously reported. ImunoAce StrepA Neo had the highest detection sensitivity and the best overall evaluation among the group A streptococcal rapid antigen detection kits used in this study. The detection sensitivity of SDSE with group A polysaccharide antigen was comparable to that of S. pyogenes. Although culture tests are necessary to confirm the causative organism, SDSE may present with clinical symptoms similar to those of S. pyogenes, and detection with a rapid antigen detection kit may be of therapeutic value.

Rapid positive blood culture reporting allows early and appropriate treatment of severe infections to improve patient prognosis. This study evaluated performance of the VersaTREK system with gas pressure detection and tornado stirring method and the conventional BacT/ALERT 3D system. Time to positivity (TTP) of simulated blood cultures without whole blood using 17 ATCC strains was faster with VersaTREK than BacT/ALERT 3D, averaging 6.3 h in aerobic bottles and 12.7 hours in anaerobic bottles. In simulated blood cultures with whole blood using 53 clinical isolates, on average, VersaTREK was faster in aerobic bottles by 6.5 h but slower in anaerobic bottles by 3.8 h. Fifty of 53 simulated blood cultures with whole blood (94%) showed fastest TTP with VersaTREK. TTP of VersaTREK for anaerobic bacteria Bacteroides fragilis and Clostridium perfringens, Helicobacter cinaedi, and Candida glabrata was fast, and viable bacteria numbers in bottles using the Miles and Misra method increased quickly.