Characterization of pig tonsils as niches for the generation of Streptococcus suis diversity.

Streptococcus suis is a gram-positive bacterium that causes meningitis, septicemia, endocarditis, and other disorders in pigs and humans. We obtained 42 and 50 S. suis isolates from lesions of porcine endocarditis and palatine tonsils, respectively, of clinically healthy pigs in Japan; we then determined their sequence types (STs) by multilocus sequence typing (MLST), cps genotypes, serotypes, and presence of classical major virulence-associated marker genes (mrp, epf, and sly). The 42 isolates from endocarditis lesions were assigned to a limited number of STs and clonal complexes (CCs). On the other hand, the 50 isolates from tonsils were diverse in these traits and seemingly in the degree of virulence, suggesting that tonsils can accommodate a variety of S. suis isolates. The goeBURST full algorithm using tonsil isolates obtained in this study and those retrieved from the database showed that major CCs as well as many other clusters were composed of isolates originating from different countries, and some of the STs were very similar to each other despite the difference in country of origin. These findings indicate that S. suis with not only different but also similar mutations in the genome have survived in tonsils independently across different geographical locations. Therefore, unlike the lesions of endocarditis, the tonsils of pigs seemingly accommodate various S. suis lineages. The present study suggests that S. suis acquired its diversity by natural mutations during colonization and persistence in the tonsils of pigs.

Sitafloxacin- Versus Moxifloxacin-Based Sequential Treatment for Mycoplasma Genitalium Infections: Protocol for a Multicenter, Open-Label Randomized Controlled Trial.

BACKGROUND: Mycoplasma genitalium is an emerging sexually transmitted pathogen associated with increasing antibiotic resistance. The current treatment guidelines recommend moxifloxacin-sequential therapy for macrolide-resistant Mgenitalium or strains with unknown resistance profiles. However, it is unclear whether sitafloxacin, a 4th-generation fluoroquinolone antibiotic, is effective against resistant strains. OBJECTIVE: This study aims to assess and compare the efficacy and safety of sitafloxacin- and moxifloxacin-based treatment regimens for managing Mgenitalium infections. METHODS: We will conduct this randomized controlled trial at multiple centers in Japan. Eligible participants include adults aged 18 years or older with a confirmed Mgenitalium infection, as determined through the nucleic acid amplification test. Patients will be randomly assigned using a stratified approach based on the treatment facility and infection site. The interventions comprise oral sitafloxacin (200 mg) daily for 7 days (with optional pretreatment of oral doxycycline, 200 mg, daily for up to 7 days), with a control group receiving oral doxycycline (200 mg) daily for 7 days followed by moxifloxacin (400 mg) daily for another 7 days. The primary outcome is the treatment success rate with a superiority margin of 10%, as confirmed through the nucleic acid amplification test. Secondary outcomes encompass changes in the bacterial load at the urogenital or rectal sites and the emergence of posttreatment-resistant mutant strains. RESULTS: Enrollment commenced in June 2023 and will conclude in December 2024, with findings anticipated by 2025. The expected success rates fall within the range of 80% for sitafloxacin and 42% for moxifloxacin against Mgenitalium carrying the G248T (S83I) mutation, based on previous studies. Accordingly, with a 5% significance level (2-sided) and 80% statistical power, we aim to recruit 50 participants per group, factoring in a 10% expected dropout rate. CONCLUSIONS: This study will provide valuable insights into the efficacy and safety of sitafloxacin- versus moxifloxacin-based sequential therapy in treating Mgenitalium infections. These findings have the potential to influence clinical guidelines, favoring more effective therapeutic choices. The multicenter approach enhances the robustness of this study. However, a limitation is the potential insufficiency of statistical power to detect posttreatment-resistant mutant strains in each group, rendering posttreatment-resistance mutations a notable concern. In the future, we may need to increase the sample size to enhance power. TRIAL REGISTRATION: Japan Registry of Clinical Trials (jRCTs031230111); https://jrct.niph.go.jp/en-latest-detail/jRCTs031230111. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/52565.

Emergence of Phytobacter diazotrophicus carrying an IncA/C2 plasmid harboring bla NDM-1 in Tokyo, Japan.

Phytobacter diazotrophicus is an Enterobacterales species that was originally identified as a plant growth-promoting, Gram-negative bacterium. Recently, this species has been recognized as relevant to opportunistic human and nosocomial infections in clinical settings. Its frequent misidentification as other Enterobacterales species from clinical examination occasionally causes a delay in the identification of nosocomial outbreaks. Here, we report the emergence of New Delhi metallo-ß-lactamase (NDM)-producing P. diazotrophicus isolated from hospitalized pediatric patients and hospital environments in Tokyo, Japan. In our case, these isolates were found during an investigation of carbapenem-resistant Enterobacterales in relation to nosocomial infections. Whole-genome sequencing is useful for overcoming the difficulty of species identification. Furthermore, we found that bla NDM-1 was carried by an IncA/C2 plasmid (approximately 170 kbp), which was transferrable from the clinical isolates to the recipient strain Escherichia coli J53. Our study demonstrated that P. diazotrophicus behaves as a carrier of bla NDM-harboring plasmids, potentially disseminating resistance to carbapenems among Enterobacterales. IMPORTANCE Early detection of nosocomial outbreaks is important to minimize the spread of bacteria. When an outbreak is caused by multidrug-resistant bacteria such as carbapenem-resistant Enterobacterales, a delay in findings makes it difficult to control it because such bacteria often spread not only among human patients but also in hospital environments. Phytobacter diazotrophicus, an Enterobacterales species that has recently been found to be relevant to clinical settings, is often misidentified as other bacteria in clinical laboratories. Here, we found NDM-producing P. diazotrophicus in hospitalized pediatric patients and their environment in Tokyo, Japan. Given that the isolates carried bla NDM-1-harboring transferrable plasmids, the influence of such bacteria could be greater with the mediation of horizontal transfer of carbapenem resistance. Our findings suggest that P. diazotrophicus should be recognized as an NDM-carrier, for which more attention should be paid in clinical settings.

Effectiveness of sitafloxacin monotherapy for quinolone-resistant rectal and urogenital Mycoplasma genitalium infections: a prospective cohort study.

BACKGROUND: Mycoplasma genitalium has a tendency to develop macrolide and quinolone resistance. OBJECTIVES: We investigated the microbiological cure rate of a 7 day course of sitafloxacin for the treatment of rectal and urogenital infections in MSM. PATIENTS AND METHODS: This open-label, prospective cohort study was conducted at the National Center for Global Health and Medicine, Tokyo, Japan from January 2019 to August 2022. Patients with M. genitalium urogenital or rectal infections were included. The patients were treated with sitafloxacin 200 mg daily for 7 days. M. genitalium isolates were tested for parC, gyrA and 23S rRNA resistance-associated mutations. RESULTS: In total, 180 patients (median age, 35 years) were included in this study, of whom 77.0% (97/126) harboured parC mutations, including 71.4% (90/126) with G248T(S83I) in parC, and 22.5% (27/120) harboured gyrA mutations. The median time to test of cure was 21 days. The overall microbiological cure rate was 87.8%. The cure rate was 100% for microbes harbouring parC and gyrA WTs, 92.9% for microbes harbouring parC G248T(S83I) and gyrA WT, and 41.7% for microbes harbouring parC G248T(S83I) and gyrA with mutations. The cure rate did not differ significantly between urogenital and rectal infection (P = 0.359). CONCLUSIONS: Sitafloxacin monotherapy was highly effective against infection caused by M. genitalium, except strains with combined parC and gyrA mutations. Sitafloxacin monotherapy can be used as a first-line treatment for M. genitalium infections in settings with a high prevalence of parC mutations and a low prevalence of gyrA mutations.

High prevalence of circulating dual-class resistant Mycoplasma genitalium in asymptomatic MSM in Tokyo, Japan.

OBJECTIVES: To assess the prevalence and antibiotic resistance profile of Mycoplasma genitalium detected from urogenital/rectal swab samples obtained from MSM in Tokyo, Japan. METHODS: We performed PCR-based screening for M. genitalium urogenital/rectal infection in 982 asymptomatic MSM between 1 January 2019 and 5 November 2020. Mutations in the antibiotic resistance-associated genes gyrA and parC and the 23S rRNA of M. genitalium were analysed. RESULTS: The prevalence of M. genitalium infection was 6.1%: the prevalence of rectal and urogenital infection was 4.7% and 1.4%, respectively. Among the cases, 48 were successfully analysed for 23S rRNA, 41 for parC mutations and 37 for gyrA mutations. Macrolide- and quinolone-resistance associated mutations (23S rRNA and parC mutations) were observed in 43 (89.6%) and 28 (68.3%) cases, respectively. The quinolone-resistance associated mutation-harbouring variants also harboured macrolide-resistance associated mutations. The S83I mutation in the parC gene was most commonly identified (24 cases, 58.5%), and its combination with M95I or D99N mutation in the gyrA gene was observed in 9 of 36 successfully analysed cases (25.0%). No significant association was observed between the presence of antibiotic resistance and antibiotic exposure for either macrolides or fluoroquinolones (P = 0.785 and 0.402, respectively). CONCLUSIONS: In Tokyo, there is an alarmingly high prevalence of M. genitalium harbouring macrolide and/or quinolone resistance-associated mutations in MSM, irrespective of antibiotic exposure. The high prevalence of M. genitalium strains with both parC and gyrA mutations limits the efficacy of sitafloxacin. Therefore, suitable alternatives are required to treat such M. genitalium infections.

Complete Genome Sequence of Ceftriaxone-Resistant Neisseria gonorrhoeae SS3160, Isolated in Tokyo, Japan.

We report the complete genome sequence of ceftriaxone-resistant Neisseria gonorrhoeae SS3160, harboring the mosaic penA-60.001 allele. This Japanese isolate has a unique sequence type (ST), ST13429, which was determined by multilocus sequence typing from the chromosome sequence (2,214,955 bp). It carries two plasmids, pConjugative (39,057 bp) and pCryptic (4,207 bp).