Molecular Analysis of Levofloxacin-resistant Streptococcus pneumoniae in Japan

Quinolone resistance has been attributed to amino acid mutations in the type II topoisomerases of pathogens. To better understand this mechanism of resistance, we analyzed the molecular epidemiology of levofloxacin-resistant Streptococcus pneumoniae in Japan. We measured the quinolone susceptibility of 668 strains of S. pneumoniae obtained through nationwide surveillance from 2006 to 2008. We also sequenced the quinolone resistance-determining regions (QRDRs) in type II topoisomerases and analyzed the relationship between minimum inhibitory concentration (MIC) and six specific mutations (Ser81 or Glu85 in GyrA, Asp435 in GyrB, Ser79 or Asp83 in ParC, and Asp435 in ParE). Eighteen of the isolated strains (2.7%) showed intermediate susceptibility and resistance to levofloxacin (MIC > 4µg/ml), with no significant difference among years. However, garenoxacin and sitafloxacin showed excellent activity against these strains. Of the 18 strains, 17 (94.4%) showed mutation in QRDRs, while in 12 out of 14 levofloxacin-resistant strains (85.7%) two or more mutations were identified. A single QRDR mutation was found in 3 of 60 levofloxacin-susceptible strains (5%), all of which had an MIC of 2µg/ml. We therefore found a high isolation frequency of levofloxacin-resistant S. pneumonia in Japan over a 2-year period. Furthermore, QRDR mutations were present in 5% of susceptible strains; these were thought to be in the early stages of resistance. In the future, the increasing use of levofloxacin might result in more strain resistance. We therefore suggest that strong quinolones such as garenoxacin and sitafloxacin could be proactively administered to high-risk patients

Monitoring Quinolone Resistance Due to Mutations in GyrA and ParC in Haemophilus Influenzae（2012-17）

Knowing recent drug-resistant bacteria trends is important for proper antibacterial drug use to improve the prognosis of patients with infectious diseases and for public health. Because multiple quinolone antibacterial agents are simultaneously adopted in hospitals in Japan, we examined whether minimum inhibitory concentrations （MICs） against Haemophilus influenzae differ among quinolones. We determined MICs of six different quinolone antibacterial agents and performed molecular genetic analysis. We investigated β-lactamase-producing and β-lactamase-negative ampicillin-resistant（BLNAR）H. influenzae using the nitrocefin method in parallel. Overall, 144 clinical H. influenzae strains isolated at the Showa University Hospital between 2012 and 2017 were subjected to MIC determination for penicillin/quinolone antibacterial agents using the Clinical and Laboratory Standards Institute broth microdilution method. Amino acid mutations in the quinolone resistance-determining regions were analyzed in the isolates showing an MIC value ≥ 0.25µg/ml of quinolone antibacterial agents. BLNAR isolates increased from 2016 onward. Among quinolone antibacterial agents, all isolates remained susceptible to sitafloxacin. However, for moxifloxacin（MFLX）, strains with an MIC value＝0.5µg/ml were detected every year since 2013 except in 2015. Amino acid mutations were investigated in 17 isolates （11.8％） with MFLX MIC value≥ 0.25µg/ml and confirmed in 11 isolates （7.6％）, of which 9 contained GyrA mutations. The results demonstrated that MFLX was useful for predicting the presence of amino acid mutations and 0.25 was an appropriate MIC threshold for this purpose. This screening procedure may be effective for reducing the inappropriate use of quinolones and controlling the emergence of drug-resistant H. influenzae

Usefulness of Serum C-reactive Protein in the Management of Adult Community-acquired Pneumonia

C-Reactive protein (CRP) is widely used as a marker of infection, but there is insufficient evidence as to its usefulness in patients with community-acquired pneumonia (CAP). In the present study, we investigated the clinical usefulness of CRP in a retrospective study of 242 patients aged 14 years who were hospitalized with CAP. Patients were classified into three groups according to the number of days between disease onset and the initial measurement of CRP as follows: Group 1, 0-1 day; Group 2, 2-4 days; Group 3, 5 days. Patients in Groups 2 and 3, who had more severe pneumonia, had higher CRP levels. Over time, CRP levels decreased in the responders in Groups 2 and 3; specifically, in Group 2, median CRP levels on Days 0, 3, and 7 were 9.85, 5.33, and 0.81mg/dL, respectively, compared with 9.99, 4.29, and 0.70mg/dL, respectively, in Group 3. In patients not responding to initial treatment, median CRP levels increased from Day 0 to Day 3 (4.32 vs. 11.70mg/dL, respectively). In all non-responders, CRP levels on Day 3 were>50% of levels on Day 0. In conclusion, when measured approximately 48 h after disease onset, CRP is useful for evaluating the severity of pneumonia and predicting the response to treatment. A good clinical outcome is likely when CRP levels on Day 3 are 50% of those on admission

All-cause mortality rates in adults with carbapenem-resistant Gram-negative bacterial infections: a comprehensive review of pathogen-focused, prospective, randomized, interventional clinical studies

Carbapenem resistance; Gram-negative; CefiderocolResistència als carbapenems; Gram-negatius; CefiderocolResistencia a carbapenémicos; Gram-negativo; CefiderocolIntroduction Pathogen-focused, randomized, controlled trials (PF-RCT) are important in the fight against carbapenem-resistant (CR) Gram-negative infections. Some recently approved antibiotics and older generic antibiotics with activity against CR Gram-negative bacteria were investigated in PF-RCTs in a variety of infections. Areas covered We searched Pubmed, Cochrane database and international clinical trial databases for PF-RCTs for the period between 2005 and 2020 and compared the study designs, patient populations, infection types, pathogens, and Day-28 all-cause mortality (ACM). Expert opinion PF-RCTs are particularly challenging to quantitatively assess and compare due to the heterogeneity in infection types, pathogens, CR mechanism, inclusion/exclusion criteria, and endpoints. Data interpretation is further complicated by lack of formal statistical analysis plans and/or non-inferiority design, and limited power across most PF-RCTs. The studies with new antibiotics (i.e. plazomicin, meropenem/vaborbactam, cefiderocol) ranked lower regarding feasibility, with relatively small sample sizes (analyzed: 37–118) versus the comparative effectiveness studies of older generic drugs (analyzed: 94–406). ACM ranged between 11.8% and 40% for CR Enterobacterales, 17.7% and 57.4% for CR Acinetobacter spp., and 20.0% and 30.8% for CR Pseudomonas aeruginosa. The information gathered must be considered carefully alongside the study limitations and caution should be exercised when making direct comparisons across trials

Investigation of the Therapeutic Effect of Tobramycin in Mice with Experimental Pneumonia in One-shot Versus Divided-dose Schedules

We measured the plasma levels of tobramycin administered by different methods and evaluated the therapeutic effects of tobramycin in mice with experimental pneumonia in various methods and dose schedules. (1) Mice were dosed with tobramycin intramuscular, intravenous oneshot injection and drip infusion, and intramuscular injection in divided doses at intervals of 15 minutes. The plasma concentration of the drug was determined at timed intervals after administration in each instance. Intramuscular and one-shot intravenous injections resulted in substantially parallel time courses of plasma concentration and plasma concentration with drip infusion was similar to that after divided intramuscular injection. (2) A therapeutic experiment was conducted in mice with Klebsiella pneumoniae pneumonia using one-shot and divided intramuscular injection methods of tobramycin. The one-shot injection group showed a satisfactory result at the dose level of 2 mg/kg, but the injection in four divided doses yielded better results at 1 mg/kg. Therefore, in cases where high doses are not feasible or are undesirable, the time of contact of the bacteria and the drug should be prolonged, rather than trying to increase the peak plasma concentration of the drug