Antimicrobial-resistant Helicobacter pylori in Japan: Report of nationwide surveillance for 2018-2020.

BACKGROUND: Antimicrobial therapy is necessary to eradicate Helicobacter pylori infection. The emergence of antimicrobial-resistant bacteria poses a threat to continued treatment with antimicrobial agents. For those who prescribe antimicrobial therapy, it is necessary to constantly monitor the emergence of antimicrobial-resistant bacteria. METHOD: H. pylori clinical isolates were collected in Japan from August 2018 to December 2020 for antimicrobial susceptibility testing. The agar dilution method was used for the determination of the minimum inhibitory concentration (MIC) of clarithromycin (CLR), amoxicillin (AMX), metronidazole (MNZ), and sitafloxacin (STX). RESULTS: MICs for 938 H. pylori isolates were examined. The primary resistance rates of H. pylori clinical isolates for CLR, AMX, MNZ, and STX in Japan were 35.5%, 2.7%, 4.2%, and 27.6%, respectively. The primary resistance rates for CLR, AMX, and MNZ were significantly higher than those of the 2002-2005 isolates. The resistance rate for CLR was significantly higher in females (males: 30.7%, females: 41.5%, p < 0.001) and higher in the ≤29 years age group (54.8%) than in the other age groups, although there were no significant differences (p = 0.104). The MNZ resistance rate was significantly higher in the ≤29 years age group than in the other age groups (p = 0.004). The resistance rate for STX increased with age, but a significant difference was only seen between the 30-49 years age group and the ≥70 years age group (p < 0.001), and the resistance rate was significantly higher in strains isolated in the Kyushu region than in the other regions (p < 0.001). CONCLUSIONS: The primary resistance rates for CLR, AMX, and MNZ of H. pylori clinical isolates in Japan were higher than those of the 2002-2005 isolates. Continuous surveillance is needed to monitor the trends in antimicrobial-resistant H. pylori.

Third nationwide surveillance of bacterial pathogens in patients with acute uncomplicated cystitis conducted by the Japanese surveillance committee during 2020 and 2021: Antimicrobial susceptibility of Escherichia coli, Klebsiella pneumoniae, and Staphylococcus saprophyticus.

The Japanese surveillance committee conducted a third nationwide surveillance of antimicrobial susceptibility of acute uncomplicated cystitis at 55 facilities throughout Japan between April 2020 and September 2021. In this surveillance, we investigated the susceptibility of Escherichia coli (E. coli), Klebsiella pneumoniae (K. pneumoniae), and Staphylococcus saprophyticus (S. saprophyticus) for various antimicrobial agents by isolating and culturing bacteria from urine samples. In total, 823 strains were isolated from 848 patients and 569 strains of target bacteria, including E. coli (n = 529, 92.9 %), K. pneumoniae (n = 28, 4.9 %), and S. saprophyticus (n = 12, 2.2 %) were isolated. The minimum inhibitory concentrations of 18 antibacterial agents were determined according to the Clinical and Laboratory Standards Institute manual. In premenopausal patients, there were 31 (10.5 %) and 20 (6.8 %) fluoroquinolone (FQ)-resistant E. coli and extended-spectrum ß-lactamase (ESBL)-producing E. coli, respectively. On the other hand, in postmenopausal patients, there were 75 (32.1 %) and 36 (15.4 %) FQ-resistant E. coli and ESBL-producing E. coli, respectively. The rate of FQ-resistant E. coli and ESBL-producing E. coli in post-menopausal women was higher than that for our previous nationwide surveillance (20.7 % and 32.1 %: p = 0.0004, 10.0 % and 15.4 %; p = 0.0259). For pre-menopausal women, there was no significant difference in the rate of FQ-resistant E. coli and ESBL-producing E. coli between this and previous reports, but the frequency of FQ-resistant E. coli and ESBL-producing E. coli exhibited a gradual increase. For appropriate antimicrobial agent selection and usage, it is essential for clinicians to be aware of the high rate of these antimicrobial-resistant bacteria in acute uncomplicated cystitis in Japan.

Fourth national Japanese antimicrobial susceptibility pattern surveillance program: Bacterial isolates from patients with complicated urinary tract infections.

INTRODUCTION: Antimicrobial susceptibility patterns of bacterial pathogens isolated from patients with complicated urinary tract infections were analyzed using the national surveillance data, comprising 793 bacterial strains from eight clinically relevant species. MATERIALS AND METHODS: Data were collected for the fourth national surveillance project from July 2020 to December 2021 by the Japanese Society of Chemotherapy, the Japanese Association for Infectious Disease, and the Japanese Society of Clinical Microbiology. Surveillance was supervised with the cooperation of 43 medical institutions throughout Japan. RESULTS: Fluoroquinolone required a minimum inhibitory concentration (MIC) of 2-64 mg/L to inhibit the 330 tested Escherichia coli strains. The proportion of levofloxacin-resistant E. coli strains increased from 28.6% in 2008 to 29.6% in 2011, 38.5% in 2015, and 44.5% in 2021. The proportion of levofloxacin-resistant strains of Pseudomonas aeruginosa also increased from previous survey results, showing a continuing downward trend. Conversely, the proportion of levofloxacin-resistant strains of Enterococcus faecalis decreased relative to previous reports. Neither multidrug-resistant P. aeruginosa nor carbapenem-resistant Enterobacteriaceae were detected. For methicillin-resistant Staphylococcus aureus (MRSA), the proportion of vancomycin-susceptible strains (MIC of 2 µg/mL) decreased from 14.7% to 7.7%. DISCUSSION: Bacterial strains that produced extended-spectrum ß-lactamase included E. coli (82/330 strains, 24.8%), Klebsiella pneumoniae (11/68 strains, 16.2%), and Proteus mirabilis (4/26 strains, 15.4%). As compared to previous surveillance reports, these strains showed an increase in proportion over the years.

Population Analysis of Daptomycin-non-Susceptible Methicillin-Resistant Staphylococcus aureus Reveals the Presence of Variants That Contribute to Daptomycin Resistance.

In this study, population analysis (PA) of methicillin-resistant Staphylococcus aureus (MRSA), before and after long-duration daptomycin (DAP) treatment, was used to detect subpopulations with different susceptibilities to DAP and to verify the changes in the number of resistant cells. Furthermore, we aimed to characterize the bacteriology of the variants present in the non-susceptible cell subpopulation. A DAP non-susceptible (NS) MRSA phenotype (D2) that emerged from a DAP- susceptible MRSA phenotype (D1) during treatment of an open wound, was used for testing. We performed bacteriological and genetic analyses of cryptic DAP-NS MRSA variants detected by PA to study the variants present in the resistant cell subpopulation. PA results suggest that MRSA adapted to survival in the presence of DAP are selected leading to reduced susceptibility. Within the cell population growing in media containing 2.0 mg/L of DAP, three variants with different pigment production and colony size were detected. Variant 3 was an orange colony due to enhanced production of staphyloxanthin. Our results revealed that the DAP minimum inhibitory concentration (MIC) value increased two-fold (4 mg/L) in variant 3, in which pigment production was most enhanced, compared to the parental strain D2. In conclusion, our results indicate that long-duration DAP treatment can lead to the emergence and increased proportion of DAP-NS subpopulations. Furthermore, slow-growing variants that can be detected only under antimicrobial selective pressure are present among DAP-NS cells, suggesting that these variants may also contribute to the development of DAP resistance.

Epigenetic effects of ceftriaxone-resistant Neisseria gonorrhoeae FC428 mosaic-like sequences found in PenA sequences unique to Neisseria subflava and related species.

OBJECTIVES: The aim of this study was to explore the origin of the PenA mosaic amino acid sequence in the ceftriaxone-resistant Neisseria gonorrhoeae FC428 clone. METHODS: The penA sequences of 27 Neisseria subflava pharyngeal isolates were determined by the Sanger method and penA sequences of 52 isolates from nine Neisseria species were obtained from the NCBI database. Comparative analysis of each PenA sequence was performed by multiple sequence alignment using ClustalW. In vitro resistance acquisition experiments were conducted to investigate the possibility of selection pressure by cefixime-induced amino acid substitution mutations in PenA. RESULTS: All N. subflava strains, including two with low susceptibility to expanded-spectrum cephalosporins (ESCs), possessed the majority of the PenA FC428 sequence. Furthermore, a number of strains, but not all, of closely related species of N. subflava showed similar results. PenA FC428 sequences were also found in some strains of distantly related species. No new mutations in the penA sequence were observed in colonies with increased MIC in in vitro resistance acquisition experiments. CONCLUSIONS: This study provides strong evidence that the FC428 PenA mosaic sequence originated from N. subflava and related species among oral commensal Neisseria species. The results of in vitro resistance acquisition experiments also suggested that one of the PenA FC428-like sequence gene polymorphisms resulted in the expression of ESC resistance. Furthermore, many of the PenA FC428 mosaic sequences were thought to be involved in the so-called epistasis effect that regulates the expression of resistance, without directly contributing to the resistance level itself.

The emergence of the ceftriaxone-resistant Neisseria gonorrhoeae FC428 clone by transfer of resistance from an oral Neisseria subflava reservoir of resistance.

BACKGROUND: The ceftriaxone-resistant Neisseria gonorrhoeae FC428 clone was first discovered in Japan in 2015. OBJECTIVES: We investigated the possibility of horizontal gene transfer from Neisseria subflava harbouring the mosaic-like PBP-2 in the emergence of the FC428 clone. We also analysed whether there were fitness costs associated with the sustained international dissemination of the clone. METHODS: Sequencing of the penA gene in ceftriaxone-resistant N. subflava strains was performed. For transformation experiments between donor N. subflava and ciprofloxacin-resistant wild-type penA N. gonorrhoeae recipient, the full-length PCR amplification product of the penA gene, including DUS regions, was used as the donor DNA. Biological fitness of the transformants was measured by growth competition assays. The impact of QRDR and mtrR mutations, which have been reported as compensatory mutations, on fitness was also assessed. RESULTS: The penA mosaic allele of the FC428 clone showed 100%, 91.8%, and 89.8% homology, respectively, with penA genes of three ceftriaxone-resistant N. subflava strains, No. 30, No. 9 and No. 14. Results were consistent with homologous recombination with the donated penA mosaic allele. In co-cultures with the parent strain, transformants showed comparable growth indicating that a gyrA mutation compensates for the fitness cost of mosaic penA alleles. CONCLUSIONS: Our findings support the hypothesis that the FC428 clone was generated by transformation of the mosaic penA allele from oropharyngeal N. subflava to N. gonorrhoeae. Furthermore, it suggests that mutations in the gyrA QRDR region compensate for fitness costs and contribute to the continued transmission of the FC428 clone.

Gene expression analysis in the potent bactericidal activity of sitafloxacin against Streptococcus pneumoniae.

We investigated the degree of expression of Streptococcus pneumoniae genes associated with bacteriolysis and cell death in relation to the rapid bactericidal activity of sitafloxacin. S. pneumoniae ATCC 49619 was added to brain heart infusion containing sitafloxacin and garenoxacin concentrations equivalent to the Cmax achieved with the usual single dose and 4 h post-Cmax concentration. RNA was extracted and cDNA was prepared using reverse transcriptase. Following RNA extraction and cDNA synthesis, quantitative PCR was performed to determine the amount of gene expression for 13 genes associated with cell death. Of the 13 genes analyzed, S. pneumoniae exposed for 10 min to a sitafloxacin concentration of 4 h post-Cmax showed 3.9 times increased expression of lytA compared to the control strain. Furthermore, we observed a slightly increased expression for cibA encoding a competence induced bacteriocin. Our study suggests that the induction of a lytic enzyme and bacteriocin may reflect gene expression in response to sitafloxacin accounting for part of its rapid bactericidal activity against S. pneumoniae.

Characterization of compensatory mutations associated with restoration of daptomycin-susceptibility in daptomycin non-susceptible methicillin-resistant Staphylococcus aureus and the role mprF mutations.

The objective of this study was to investigate the underlying mechanism explaining reversion of clinical DAP non-susceptible (NS) MRSA isolates to DAP-susceptible (S) by analysis of genomic and cell wall characteristics of clinical DAP-NS MRSA and DAP-S MRSA isolates as well as in vitro revertant DAP-S MRSA using whole genome sequencing (WGS) and analysis of biological properties. WGS of the 4 clinical DAP-NS MRSA revealed mprF mutations resulting in amino acid substitutions or deletion. These same amino acid substitutions and deletion were also observed in the 4 in vitro revertant DAP-S strains. While WGS identified the presence of the same mprF mutations in both the DAP-NS and in vitro DAP-S revertant strains, new mutations were also detected in other genes and intergenic regions of in vitro DAP-S revertant strains. Transmission electron microscopy to assess cell-wall (CW) thickness of 4 sets strains (pre- and post-DAP therapy isolates and in vitro DAP-S revertant) showed that 3 of the 4 isolates developed increased thickness of the CW after DAP therapy. After reversion to DAP susceptibility, CW thickness was decreased to the same level as DAP-S MRSA. Our results indicate that in vitro conversion of DAP-NS MRSA to DAP-S is independent of mprF gene mutations and may be partially explained by a change in CW thickness. However, as some strains showed no change in the CW, further studies are required to elucidate the different mechanisms of resistance to DAP, and factors for conversion of DAP-NS to DAP-S.

In vitro activity of various antibiotics against clinical strains of Legionella species isolated in Japan.

The activities of various antibiotics against 58 clinical isolates of Legionella species were evaluated using two methods, extracellular activity (minimum inhibitory concentration [MIC]) and intracellular activity. Susceptibility testing was performed using BSYEα agar. The minimum extracellular concentration inhibiting intracellular multiplication (MIEC) was determined using a human monocyte-derived cell line, THP-1. The most potent drugs in terms of MICs against clinical isolates were levofloxacin, garenoxacin, and rifampicin with MIC90 values of 0.015 µg/ml. The activities of ciprofloxacin, pazufloxacin, moxifloxacin, clarithromycin, and azithromycin were slightly higher than those of levofloxacin, garenoxacin, and rifampicin with an MIC90 of 0.03-0.06 µg/ml. Minocycline showed the highest activity, with an MIC90 of 1 µg/ml. No resistance against the antibiotics tested was detected. No difference was detected in the MIC distributions of the antibiotics tested between L. pneumophila serogroup 1 and L. pneumophila non-serogroup 1. The MIECs of ciprofloxacin, pazufloxacin, levofloxacin, moxifloxacin, garenoxacin, clarithromycin, and azithromycin were almost the same as their MICs, with MIEC90 values of 0.015-0.06 µg/ml, although the MIEC of minocycline was relatively lower and that of rifampicin was higher than their respective MICs. No difference was detected in the MIEC distributions of the antibiotics tested between L. pneumophila serogroup 1 and L. pneumophila non-serogroup 1. The ratios of MIEC:MIC for rifampicin (8) and pazufloxacin (2) were higher than those for levofloxacin (1), ciprofloxacin (1), moxifloxacin (1), garenoxacin (1), clarithromycin (1), and azithromycin (1). Our study showed that quinolones and macrolides had potent antimicrobial activity against both extracellular and intracellular Legionella species. The present data suggested the possible efficacy of these drugs in treatment of Legionella infections.

[Bacteriological Properties of Meropenem-resistant Escherichia coli Isolated from Seven Patients within a Month].

From April to May 2014, a total of seven cases of meropenem (MEPM)-resistant Escherichia coli were isolated from the sputum specimens in 7 different patients in a community hospital. The MICs of MEPM for isolates were 8 to 32 µg/mL, whereas the MICs of imipenem (IPM) were 0.5 µg/mL or 1 µg/mL. All of the isolates possessed the metallo ß-lactamase (MBL) IMP-6 gene, and were CTX-M-2 type extended-spectrum ß-lactamase (ESBL)-producers. Pulsed-field gel electrophoresis (PFGE) patterns for the isolates were identical. At the time of specimen collection, one patient had been hospitalized for a long time and the other six patients had been comparatively recently admitted to the hospital. Of the six patients, two had been staying in the same nursing facility before admission, whereas the remaining 4 patients had no relationship with each other because they had been in separate locations. Thus, these cases were not considered to be nosocomially-acquired infection. Our findings suggest that MBL-producing E. coli has been spreading widely in the community such as in local nursing facilities.

[Evaluation of the BD Phoenix ID Yeast System for the Species Identification of Clinical Yeast-Like Organisms].

Most fungi isolated from patients with deep-seated mycosis are yeast-like organisms such as Candida and Cryptococcus. As their respective susceptibilities to antifungal agents can vary depending on the species, rapid identification is important for the administration of appropriate antifungal therapy. The aim of this study was to evaluate the performance of a new automated identification panel, Phoenix Yeast ID (Becton, Dickinson Diagnostics, USA) as well as the time required for identification. The identification results of 106 isolates generated by this system were then compared with those of the API 20C AUX system (SYSMEX bioMérieux Co., Ltd. Japan). Among the 106 isolates, the identification agreement between the two yeast panels was 97/106 (91.5%). Of the 9 (8.5%) discrepant identifications, 5 identification using the Phoenix Yeast ID system and 1 identification using the API 20C AUX system agreed with the genotypic identification. Genotypic identification did not agree with the Phoenix Yeast ID or API 20C AUX findings for the remaining 3 discrepant identifications. Approximately 60% of the C. albicans, C. tropicalis, and C. parapsilosis isolates were identified within 4 hours. In total, about 90% of the 4 major Candida sp. (C. albicans, C. tropicalis and C. glabrata) were identified within 8 hours. In conclusion, the Phoenix Yeast ID findings agreed well with the API 20C AUX findings. Genotypic identification of the discrepant identifications confirmed most of the Phoenix Yeast ID panel identifications. As approximately 80% of the major Candida sp. could be identified within 8 hours using the Phoenix Yeast ID identification system, our results suggest that this system is a clinically useful addition to commercially available yeast identification panels. The Phoenix Yeast ID system showed excellent concordance with genotypic identification for the classification of organisms with discrepant API 20C AUX findings.

[Decreasing Susceptibility of MRSA to Daptomycin During the Course of Treatment].

Methicillin-resistant Staphylococcus aureus (MRSA) with decreased susceptibility to daptomycin (DAP) were isolated from 4 patients receiving DAP from November 2013 to May 2014. These patients were treated with DAP for more than 7 days in all the cases. The pulsed-field gel electrophoresis (PFGE) patterns for MRSA isolates recovered from each patient pre- and post-DAP therapy were identical. Sequencing of mprF detected 2 amino acid substitutions (T345I or L826F) in 2 of the isolates. These results suggest that in vivo MRSA was resistant to DAP during DAP therapy. Furthermore, the MICs for DAP can vary by±1 dilution depending on the susceptibility test. When testing DAP susceptibility, there is a need to monitor reproducibility using different susceptibility tests, including the CLSI method.

High Prevalence of Azithromycin-Resistant Neisseria gonorrhoeae Isolates With a Multidrug Resistance Phenotype in Fukuoka, Japan.

BACKGROUND: The current guidelines recommend a combination of ceftriaxone and azithromycin as a first-line treatment of gonorrhea in the United States and Europe. Despite not being recommended as a first-line regimen in Japan, an oral 2-g dose of azithromycin did become available for gonococcal infections in 2009. Recently, the emergence of azithromycin-resistant Neisseria gonorrhoeae isolates has been reported in several countries, including Japan. METHODS: Antimicrobial susceptibility testing was performed on a total of 677 clinical isolates of N. gonorrhoeae obtained from January 2010 to December 2013 in Fukuoka, Japan. A molecular analysis by N. gonorrhoeae multiantigen sequence typing was conducted on the azithromycin-resistant isolates. RESULTS: The proportion of azithromycin-resistant isolates (minimum inhibitory concentration > 0.5 µg/mL) increased significantly from 1.8% in 2010 to 22.6% in 2013 (P < 0.001). Among 50 azithromycin-resistant isolates, 30 (60%) exhibited a resistant phenotype to multiple drugs including cefixime. The 2 predominant sequence types (STs) identified by N. gonorrhoeae multiantigen sequence typing were ST6798 (por allele 4033 and tbpB allele 110) and ST1407 (por allele 908 and tbpB allele 110) at 40.0% (20/50) and 12.0% (6/50), respectively. There was a statistically significant increase of the proportion of ST6798 from 0% (0/19) in 2010-2012 to 64.5% (20/31) in 2013 (P < 0.001). CONCLUSIONS: Over the previous 4 years, an increasing prevalence of azithromycin-resistant N. gonorrhoeae isolates with a multidrug-resistant phenotype was observed. Furthermore, the azithromycin-resistant isolates seemed to belong to 2 predominant STs. As a result, continued surveillance of gonococci resistant to antimicrobial agents, including azithromycin in Fukuoka, Japan, is necessary.

The efficacy, safety, and pharmacokinetics of biapenem administered thrice daily for the treatment of pneumonia in the elderly.

Biapenem has been widely used to treat bacterial pneumonia; however, there is little information concerning its efficacy and safety in elderly patients. Based on pharmacokinetic-pharmacodynamic theory, administration of biapenem thrice rather than twice daily would be expected to be more effective because of longer time above the minimum inhibitory concentration. In this study, we aimed to evaluate the efficacy, safety, and pharmacokinetics of biapenem (300 mg) administered thrice daily in pneumonic patients aged 65 years or older. Biapenem was effective in 22 of 25 patients, as assessed by the improvement in clinical symptoms and/or the eradication of the causative organisms, and caused no serious adverse events. The pharmacokinetic profile was established based on simulations using a modeling program. Among 17 patients whose causative organisms were detected, time above the minimum inhibitory concentration was estimated to be 100% in 16 patients, all of whom showed clinical improvement. The results of this study confirmed the efficacy and safety of 300 mg of biapenem administered thrice daily for the treatment of pneumonia in elderly patients.

Distribution of Staphylococcus aureus carriage among healthcare workers in a Japanese convalescent and rehabilitation hospital.

Earlobes, nasal cavities, and fingers of 145 healthcare workers in convalescent and rehabilitation hospital (60 nurses and 85 rehabilitation healthcare workers) were sampled. Of the 3 sites sampled, Staphylococcus aureus was detected in one or more sites in 25 nurses and 27 rehabilitation workers. S. aureus was detected in all 3 sites in 2 (8.0%) nurses and 2 (7.4%) rehabilitation workers, and the S. aureus isolates in each case showed related PFGE pattern. S. aureus was detected in both the fingers and nasal cavities of 5 (18.5%) of the rehabilitation healthcare workers; in all 5 cases, the PFGE patterns of the S. aureus isolates from each site belonged to same cluster based on PFGE. Of the 2 cases in which methicillinresistant S. aureus (MRSA) was recovered from earlobes, fingers, and nasal cavities, in both cases, MRSA isolates from the 3 sites were the same clone according to PFGE analysis and SCCmec type IV. As S. aureus was detected in pierced earlobes of nurses, hand hygiene must be practiced after touching pierced earlobes and before patient contact. The same S. aureus clone in the nasal cavity and earlobes indicates that the route of transmission is through the fingers.

In vitro activities of antimicrobial combinations against clinical isolates of Neisseria gonorrhoeae.

The Centers for Disease Control and Prevention (CDC) now recommend combination therapy with ceftriaxone 250 mg plus azithromycin (AZM) 1 g as a first-line regimen for gonorrhea because the increase of Neisseria gonorrhoeae resistant to multiple antimicrobial agents. However, reports on the in vitro activity of antimicrobial combinations against clinical isolates of N. gonorrhoeae are very rare. In the present study, a checkerboard method was utilized to examine the in vitro activity of ceftriaxone (CTRX), cefodizime (CDZM), spectinomycin (SPCM), or gentamicin (GM) in combination with AZM against 25 clinical isolates of N. gonorrhoeae. The SPCM + AZM combination demonstrated the lowest mean fractional inhibitory concentration index (FICI) of 0.69, followed by the CDZM + AZM combination (mean FICI, 0.75), the CTRX + AZM combination (mean FICI, 0.81), and the GM + AZM combination (mean FICI, 0.83). Additivity/indifference effect was detected for the SPCM + AZM combination, the CDZM + AZM combination, the CTRX + AZM combination, and the GM + AZM combination, against 96%, 72%, 92%, and 100% of the isolates, respectively. There was no antagonism for any of the antimicrobial combinations against the 25 N. gonorrhoeae isolates. These results suggest that the antimicrobial combinations may be worthy of clinical evaluation as an alternative regimen for gonococcal infections caused by antimicrobial-resistant strains.

[Examination of metallo-beta-lactamase-producing different types of Serratia marcescens detected in the same patient].

Metallo-beta-lactamase (MBL) producing Serratia marcescens isolate was recovered from a study patient in September, 2007 in whom MBL non-producing S. marcescens had been isolated 2 months previously. Two S. marcescens isolates recovered from the study patient showed the same pulsed-field gel electrophoresis (PFGE) pattern. Seven S. marcescens isolates were recovered from other patients in our hospital during August, 2007 and November, 2007. Five of the seven isolates produced MBL. All of the MBL-producing isolates showed the same PFGE pattern and harbored plasmids of the same size and bla(IMP) genes. The bla(IMP) genes were easily transferred to Escherichia coli DH5alpha by transformation of a plasmid purified from the MBL-producing isolate. Those transformation experiments suggested that bla(IMP) genes were encoded by the plasmid. From these observations, it was speculated that the MBL non-producing S. marcescens isolate recovered from the study patient had acquired the plasmid which encoded bla(IMP) genes and a monoclone of MBL-producing S. marcescens spread horizontally in our hospital.

[Bactericidal activity of sitafloxacin and other new quinolones against antimicrobial resistant Streptococcus pneumoniae].

We conducted a study assess the bactericidal activity of sitafloxacin (STFX) against Streptococcus pneumoniae isolates recovered from respiratory infections including penicillin-resistant (PRSP) isolates, macrolide resistant isolates possessing mefA and ermB resistance genes and quinolone resistance isolates with mutations in gyrA or gyrA and parC. Each isolate tested was grown in hemosupplemented Mueller-Hinton broth and adjusted to approximately 10(5) CFU/ mL. Isolates were than exposed to a Cmax antimicrobial blood level that would be attained with routine antimicrobial administration and an antimicrobial level that would be expected 4 hours post-Cmax (Cmax 4hr). Bactericidal activity was measured for up to 8 hours. Excluding a subset of S. pneumoniae isolates with mutations in the quinolone resistance determining region (QRDR), all quinolones showed bactericidal activity at Cmax and Cmax 4 hr antimicrobial concentrations for up to 8 hours. Against S. pneumoniae isolates with either gyrA or gyrA and parC mutations, bactericidal activity of STFX was shown for up to 4 to 8 hours following Cmax based on a limit of detection of < 1.3 log CFU/mL. Garenoxacin (GRNX) did not showed bactericidal activity below the limit of detection for up to 8 hours with exposure to Cmax and no bactericidal activity was seen with levofloxacin. When all quinolones tested where adjusted to concentrations corresponding to their MICs, STFX showed the most rapid bactericidal activity against PRSP. This rapid bactericidal activity in PRSP is a key to the effectiveness of STFX. Our findings show that beyond inhibition of bacterial replication by blocking their DNA replication pathway and synthesis of proteins, STFX demonstrated characteristics contributing to greater bactericidal activity compared to GRNX. In conclusion, of the newer quinolones, STFX showed the strongest bactericidal activity against S. pneumoniae isolates with mutations in the QRDR which indicates that it may show the most effective clinical utility among the quinolones in respiratory infections.

Antibiotic-resistant phenotypes and genotypes of Neisseria gonorrhoeae isolates in Japan: identification of strain clusters with multidrug-resistant phenotypes.

OBJECTIVES: To determine the antibiotic susceptibility and the genotype distributions of N. gonorrhoeae isolates in Fukuoka, Japan, and to evaluate the specific associations between genotypes and antibiotic resistance. METHODS: Antibiotic susceptibility testing and N. gonorrhoeae multiantigen sequence typing (NG-MAST) were performed on 242 and 239 N. gonorrhoeae isolates, respectively, in Fukuoka, Japan in 2008. RESULTS: No isolates showed resistance to spectinomycin, ceftriaxone, or cefixime, although 34 (14.0%) and 149 (61.6%) isolates displayed decreased susceptibility to ceftriaxone (minimum inhibitory concentration range, 0.06-0.5 mg/L) and cefixime (minimum inhibitory concentration range, 0.06-0.5 mg/L), respectively. Furthermore, 171 (70.7%), 68 (28.1%), 39 (16.1%), and 1 (0.4%) isolates were resistant to ciprofloxacin, tetracycline, penicillin, and azithromycin, respectively. The 239 isolates were divided by NG-MAST into 67 sequence types (STs); the 4 most common STs were ST2958 (20.5%), ST4018 (7.5%), ST1407 (6.7%), and ST4487 (5.9%). ST2958 and ST1407 were characterized by a multidrug-resistant phenotype, whereas ST4018 and ST4487 presented a susceptible phenotype. Interestingly, ST1407, which is now common in Europe and Australia, was identified as a predominant ST in this study. CONCLUSIONS: This is the first report combining N. gonorrhoeae antibiotic susceptibility testing with molecular typing by using NG-MAST in Japan. Although a large diversity in NG-MAST was identified, based on comparisons with the international data, the ST1407 with a multidrug-resistant phenotype currently seems to be circulating worldwide.

[Nationwide antimicrobial susceptibility survey of Neisseria gonorrhoeae isolates in Japan].

In a nationwide antimicrobial susceptibility survey of 494 Nesseria gonorrhoeae isolates collected from February 2008 to December 2009 in 3 regions of Japan, 112 (22.7%) were collected from western Japan (Kinki, Chugoku, Shikoku, and Kyushu), 277 (56.1%) from mid-eastern Japan (Kanto), and 105 (21.1%) from eastern Japan (Tokai, Hokuriku, Koushinetsu, Tohoku, and Hokkaido). Resistance to ciprofloxacin (CPFX) was 72.8%, to penicillin G (PCG) 19.8%, and to tetracycline (TC) 18.2%. Intermediate resistance to CPFX was 1.8%, to PCG 73.7%, and to TC 43.7%. These results indicate that both types of resistance to the 3 agents were very high. Intermediate resistance to cefixime (CFIX) was 38.1% and to cefozidim (CDZM) 13.4%. Resistance to CFIX was only 0.4% and to CDZM 0%. Susceptibility to azithromycin was 96.6%, to ceftriaxone 99.8%, and to spectinomycin 100%. No significant difference in resistance was seen to different antimicrobial agent classes tested in the 3 regions, although intermediate resistance to CFIX in western Japan was significantly higher than in mid-eastern Japan.