In vitro antibacterial activities of doripenem, imipenem, and meropenem against recent Streptococcus pneumoniae isolates

Dual drug delivery of vancomycin and imipenem/cilastatin by coaxial nanofibers for treatment of diabetic foot ulcer infections

Diabetic foot ulcer infections are the main causes of hospitalization in diabetics. The present study aimed to develop vancomycin and imipenem/cilastatin loaded core-shell nanofibers to facilitate the treatment of diabetic foot ulcers. Therefore, novel core-shell nanofibers composed of polyethylene oxide, chitosan, and vancomycin in shell and polyvinylpyrrolidone, gelatin, and imipenem/cilastatin in core compartments were prepared using the electrospinning technique. The nanofibers were characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, tensile test, and drug release. The antibacterial activity of drug-loaded nanofibers in different drugs concentrations was evaluated against Methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli, and Pseudomonas aeruginosa by disk diffusion method. Furthermore, the cytotoxicity of fibers was investigated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay. The obtained results showed that the prepared nanofibers were smooth having a core-shell structure with almost no cytotoxicity. The nanofibrous mats exhibited significant antibacterial activity against S. aureus and MRSA with the inhibition zones of 2.9 and 2.5 cm and gram-negative bacteria species of E. coli and P. aeruginosa with the inhibition zones of 1.9 and 2.8 cm, respectively. With respect to the significant antibacterial activities of these nanofibrous mats, they might be used as suitable drug delivery devices not only for diabetic foot ulcer infections but also for other chronic wounds.

Effects of Delayed Antibiotic Therapy on Outcomes in Children with Streptococcus pneumoniae Sepsis

Delayed antimicrobial therapy is associated with poor outcomes in sepsis, but the optimal antibiotic administration time remains unclear. We aimed to investigate the effects of the time of antimicrobial administration on outcomes and evaluate an optimal empirical antibiotic administration time window for children with Streptococcus pneumoniae sepsis. This retrospective study enrolled children with S. pneumoniae sepsis who presented to the Children's Hospital of Chongqing Medical University from May 2011 to December 2018. Classification and regression tree (CART) analysis was used to determine the time-to-appropriate-therapy (TTAT) breakpoint. Outcomes were compared between patients receiving early or delayed therapy, defined by CART-derived TTAT breakpoint. During the study period, 172 patients were included. The CART-derived TTAT breakpoint was 13.6 h. After adjustment for confounding factors, a TTAT of ≥13.6 hours was found to be an independent predictor of sepsis-related in-hospital mortality (odds ratio [OR] = 39.26; 95% confidence interval [CI] = 6.10 to 252.60), septic shock (OR = 4.58; 95% CI = 1.89 to 11.14), and requiring mechanical ventilation (OR = 2.70; 95% CI = 1.01 to 7.35). A Pediatric Risk of Mortality (PRISM) III score of ≥10 was independently associated with delayed therapy. Delayed antibiotic therapy was associated with poor outcomes in children with S. pneumoniae sepsis. The optimal empirical antibiotic administration time window in children with S. pneumoniae sepsis was within 13.6 h. Efforts should be made to ensure timely and appropriate therapy.

Identification of Antipneumococcal Molecules Effective Against Different Streptococcus pneumoniae Serotypes Using a Resazurin-Based High-Throughput Screen

Streptococcus pneumoniae is a major human pathogen, causing around 1.6 million deaths worldwide each year. By optimizing a resazurin-based assay to detect S. pneumoniae growth in 384-well microplates, we developed a new high-throughput screening (HTS) system for the discovery of antipneumococcal molecules, which was unsuccessful using conventional absorbance measurements. Before applying our protocol to a large-scale screen, we validated the system through a pilot screen targeting about 7,800 bioactive molecules using three different S. pneumoniae serotypes. Primary screenings of a further 27,000 synthetic small molecules facilitated the identification of 3-acyl-2-phenylamino-1,4-dihydropquinolin-4-one (APDQ) derivatives that inhibited growth of S. pneumoniae with MIC₉₀ values <1 μM (0.03-0.81 μM). Five selected APDQ derivatives were also active against Staphylococcus aureus but neither Klebsiella pneumoniae nor Pseudomonas aeruginosa, suggesting that APDQ may act specifically against Gram-positive bacteria. Our results both validated and demonstrated the utility of the resazurin-based HTS system for the identification of new antipneumococcal molecules. Moreover, the identified new antipneumococcal molecules in this study may have potential to be further developed as new antibiotics.

Nationwide population-based surveillance of invasive pneumococcal disease in Japanese children: Effects of the seven-valent pneumococcal conjugate vaccine

BACKGROUND

In Japan, the seven-valent pneumococcal conjugate vaccine (PCV7) was introduced in 2010. PCV13 has replaced PCV7 since November 2013.

METHODS

The effectiveness of PCV7 in protecting against invasive pneumococcal disease (IPD) in children aged <5 years was evaluated in a nationwide active population-based surveillance of IPD in 2008-2013 in 10 prefectures in Japan.

RESULTS

1181 cases were identified; 711 pneumococcal strains were analyzed for serotyping and antimicrobial resistance. Compared with the baseline IPD incidence (25.0 per 100,000), a 98% decline in IPD caused by PCV7 serotypes was found after the introduction of PCV7. This was partially offset by an increased incidence of IPD caused by PCV13 minus PCV7 and non-PCV13 serotypes, resulting in a 57% decline in overall IPD incidence. Absolute increases in the incidence rates of IPD caused by PCV13 minus PCV7 and non-PCV13 serotypes were 2.1 and 2.8 per 100,000 during the study period, respectively. The proportion of meropenem-nonsusceptible strains, especially with serotypes 19A and 15A, increased significantly after PCV7 introduction.

CONCLUSIONS

Our data confirmed a 98% decline in IPD incidence caused by PCV7 serotypes in children aged <5 years and serotype replacement after PCV7 introduction. This shows the importance of continuing surveillance of serotypes responsible for IPD and their antimicrobial resistance in Japan.

Genetic analysis of invasive pneumococcal isolates from children in Ontario, Canada, 2007-2012

BACKGROUND

Multilocus sequence typing (MLST) is commonly used to understand the genetic background of invasive pneumococcal disease (IPD) isolates. This study was conducted to identify serotype and genetic change among IPD isolates in Canadian children following vaccine use.

METHODS

Clinical isolates collected from children ≤5 years old of Ontario, Canada with IPD during 2007-2012 were characterized with serotyping, multilocus sequence typing and antimicrobial susceptibility testing.

RESULTS

One year after 13-valent pneumococcal conjugate vaccine (PCV13) implementation, a decline in 19A and 7F was observed in 2012, coincident with the rise of serogroup 15 and 22F. Clonal complex (CC) 199, CC320 and CC695 are 3 major CCs in 19A (74%). From 2007 to 2012, clonal shift was detected in the 19A population as CC320 and CC199 declined, whereas CC695 rose to a majority. Genetically, serogroup 15 was composed of 2 CCs and 7 sequence types (STs), making it more diverse than serotypes 3, 7F and 22F. Interestingly, 60% of 15C isolates were a novel ST, suggesting high single nucleotide polymorphism frequency in house-keeping genes of 15C. Several newly appeared STs found in 19A and 15 indicate the possibility of recent serotype switching events.

CONCLUSION

Genetic shift because of PCV13 impact may have resulted in the decline of 19A in IPD. Recent rise of serogroup 15 infections in children could be because of its selective advantage conferred by genetic diversity, frequent recombination in the population plus drug resistance potential related to CC63 genotype. Close monitoring of serotype replacement and genetic change in IPD among children post-PCV13 is warranted.

Bacteremic pneumonia caused by extensively drug-resistant Streptococcus pneumoniae

The emergence of antimicrobial resistance threatens the successful treatment of pneumococcal infections. Here we report a case of bacteremic pneumonia caused by an extremely drug-resistant strain of Streptococcus pneumoniae, nonsusceptible to at least one agent in all classes but vancomycin and linezolid, posing an important new public health threat in our region.