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Published on: January 17, 2014
Molecular and phenotypic characterization of Streptococcus pneumoniae isolates in a Japanese tertiary care hospital
Takumi Nakao1, Kosuke Kosai1, Norihiko Akamatsu2
1Department of Laboratory Medicine, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
Abstract:
This study aimed to investigate the bacterial characteristics of pneumococcal isolates obtained from a tertiary care hospital in Japan. We analyzed the antimicrobial susceptibility, possession of macrolide resistance genes, pneumococcal serogroup/serotype, and sequence type (ST) of pneumococcal isolates from patients aged 15 years or older between 2011 and 2020 at Nagasaki University Hospital. Of the 73 isolates analyzed, 86.3% showed resistance to macrolides, and 28.8%, 46.6%, and 11.0% harbored mefA, ermB, and both, respectively. Of the isolates possessing ermB, 97.6% showed high levels of macrolide resistance [minimal inhibitory concentration (MIC) range, > 16 µg/mL]. Solithromycin (MIC range, 0.03-0.25 µg/mL), regardless of the presence of macrolide resistance genes, and lascufloxacin (MIC range, 0.06-0.5 µg/mL) showed potent in vitro activity against pneumococci. Serotype 19A was the most prevalent (six isolates), followed by serotypes 10A, 15A, and 15B/C (five isolates each). Four serotypes (11A, 19A, 22F, and 23B) and five STs (36, 99, 433, 558, and 3111) were significantly correlated with the presence of macrolide resistance genes. All four isolates with serotype 11A/ST99 and three isolates with serotype 19A/ST3111 harbored both mefA and ermB. No macrolide resistance genes were detected in either of the two isolates with serotype 22F/ST433, while all ten isolates with serogroup 15 (serotypes 15A and 15B/C, five isolates each) possessed ermB alone. Our study revealed the bacterial characteristics of the pneumococcal isolates obtained from our hospital. In vitro activity of solithromycin and lascufloxacin against these isolates was confirmed.
Insights
High rates of macrolide resistance were found in Japanese pneumococcal isolates, with specific serotypes and sequence types linked to resistance genes. Novel antibiotics solithromycin and lascufloxacin demonstrated potent in vitro activity against these resistant strains.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Streptococcus pneumoniae (pneumococcus) is a leading cause of bacterial infections worldwide.
- Macrolide resistance in pneumococci is a growing public health concern, complicating treatment options.
- Understanding the characteristics of local pneumococcal populations is crucial for effective antimicrobial stewardship.
Purpose of the Study:
- To investigate the bacterial characteristics of pneumococcal isolates from a Japanese tertiary care hospital.
- To analyze antimicrobial susceptibility, macrolide resistance gene prevalence, serotypes, and sequence types.
- To evaluate the in vitro activity of novel antibiotics against these isolates.
Main Methods:
- Analysis of 73 pneumococcal isolates from patients aged ≥15 years (2011-2020) at Nagasaki University Hospital.
- Antimicrobial susceptibility testing, including minimal inhibitory concentration (MIC) determination.
- Detection of macrolide resistance genes (mefA, ermB) and characterization of pneumococcal serotypes and sequence types (STs).
Main Results:
- 86.3% of isolates exhibited macrolide resistance; 28.8% harbored mefA, 46.6% ermB, and 11.0% both.
- Isolates with ermB showed high-level macrolide resistance (MIC > 16 µg/mL).
- Serotype 19A was most prevalent; serotypes 11A, 19A, 22F, and 23B, along with specific STs, were significantly correlated with macrolide resistance genes.
- Solithromycin and lascufloxacin demonstrated potent in vitro activity against all isolates, irrespective of resistance gene presence.
Conclusions:
- A high prevalence of macrolide resistance exists in pneumococcal isolates from Nagasaki University Hospital.
- Specific serotypes and STs are associated with macrolide resistance mechanisms.
- Solithromycin and lascufloxacin represent promising therapeutic options against drug-resistant pneumococci.
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