Related Experiment Video

Updated: Aug 24, 2026

Antibiotic Efficacy Testing in an Ex vivo Model of Pseudomonas aeruginosa and Staphylococcus aureus Biofilms in the Cystic Fibrosis Lung
09:26

Antibiotic Efficacy Testing in an Ex vivo Model of Pseudomonas aeruginosa and Staphylococcus aureus Biofilms in the Cystic Fibrosis Lung

Published on: January 22, 2021

Fluoroquinolone resistance in clinical isolates of Streptococcus pneumoniae from Asian countries: ANSORP study

Won Sup Oh1, Ji Yoeun Suh, Jae-Hoon Song

  • 1Samsung Medical Centre, Sungkyunkwan University School of Medicine, Seoul, Korea.

Microbial Drug Resistance (Larchmont, N.Y.)
|May 14, 2004
PubMed

Insights

Reduced susceptibility to ciprofloxacin in Streptococcus pneumoniae is linked to multiple genetic mutations. Specific alterations in gyrA, gyrB, parC, and parE genes contribute to fluoroquinolone resistance in these bacterial isolates.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Genetics

Background:

  • Streptococcus pneumoniae is a leading cause of bacterial pneumonia and meningitis.
  • Fluoroquinolone antibiotics are crucial for treating pneumococcal infections.
  • Emergence of fluoroquinolone resistance in S. pneumoniae poses a significant public health threat.

Purpose of the Study:

  • To investigate the genetic mechanisms underlying reduced susceptibility to ciprofloxacin in clinical isolates of Streptococcus pneumoniae from Asia.
  • To identify specific mutations in quinolone resistance-determining regions (QRDRs) associated with fluoroquinolone resistance.

Main Methods:

  • Antimicrobial susceptibility testing was performed on 17 clinical isolates.
  • Serotyping and pulsed-field gel electrophoresis (PFGE) were used for molecular characterization.
  • DNA sequencing of gyrA, gyrB, parC, and parE genes was conducted to identify mutations in QRDRs.

Main Results:

  • All but one isolate exhibited multiple amino acid alterations in the QRDRs of gyrA, gyrB, parC, and parE.
  • Ile460 --> Val in parE was the most frequent mutation.
  • Specific mutations, such as Lys137 --> Asn in parC and Ser81 --> Phe in gyrA, were associated with high-level fluoroquinolone resistance.
  • Two novel mutations in gyrB (Ala390 --> Val and Asn423 --> Thr) were identified.
  • PFGE suggested the local spread of a multidrug-resistant Spain(23F)-1 clone in Hong Kong.

Conclusions:

  • Multiple genetic mutations in QRDRs are responsible for reduced ciprofloxacin susceptibility in S. pneumoniae.
  • Specific mutations in parC and gyrA play key roles in developing high-level and multidrug resistance.
  • The Spain(23F)-1 clone may be spreading in Hong Kong, necessitating further surveillance.

Related Concept Videos

Mechanism of Antibiotic Resistance in MRSA01:25

Mechanism of Antibiotic Resistance in MRSA

Antibiotic resistance in bacteria arises when microorganisms evolve the ability to withstand drugs designed to kill them or inhibit their growth, rendering once-effective treatments useless. This phenomenon, driven by genetic change and selection under antibiotic exposure, poses a profound threat to modern medicine. Mechanisms include drug-inactivating enzymes (e.g., β-lactamases), efflux pumps that eject antibiotics, mutations altering antibiotic targets, decreased drug uptake, and acquisition...
Inhibitors of Bacterial DNA Synthesis01:28

Inhibitors of Bacterial DNA Synthesis

Bacterial pathogens depend on precise and efficient DNA replication to sustain infection. Two type II topoisomerases—DNA gyrase and topoisomerase IV—are critical to this process, as they resolve DNA supercoiling and unlink chromosomes during replication. Fluoroquinolones, synthetic derivatives of quinolones, exploit this mechanism by stabilizing the transient DNA–enzyme cleavage complex, preventing strand religation, and causing lethal double-strand breaks. These antibiotics are selectively...
Clinical Significance of Antibiotic Resistance01:25

Clinical Significance of Antibiotic Resistance

Methicillin-resistant Staphylococcus aureus (MRSA) presents a critical public health threat, arising from its capacity to resist β-lactam antibiotics due to acquisition of the mecA gene within the staphylococcal cassette chromosome mec (SCCmec). This gene encodes penicillin-binding protein 2a (PBP2a), which impairs binding efficacy of methicillin and other β-lactams. MRSA has evolved into distinct clonal lineages impacting humans and animals alike, reinforcing its significance within the One...
Gene Regulation in Microbial Communities: Quorum Sensing01:28

Gene Regulation in Microbial Communities: Quorum Sensing

Quorum sensing is a mechanism of bacterial communication that enables coordinated gene expression in response to changes in population density. This facilitates collective behaviors that enhance survival, resource acquisition, and ecological adaptation. This process relies on small signaling molecules called autoinducers that accumulate as bacterial populations grow. When a critical threshold concentration of autoinducers is reached, bacterial cells collectively modify gene expression,...
Development of Antibiotic Resistance01:30

Development of Antibiotic Resistance

Antibiotic resistance is a major public health concern that arises when bacteria evolve mechanisms to withstand the effects of antibiotic treatments. This resistance can be intrinsic, acquired through genetic mutations, or transferred between bacteria via horizontal gene transfer. The development of antibiotic resistance poses significant challenges in treating bacterial infections and necessitates ongoing research to develop new therapeutic strategies.Intrinsic resistance occurs when bacterial...
Atypical Pneumonia01:14

Atypical Pneumonia

Atypical pneumonia, often caused by Mycoplasma pneumoniae, is a form of pulmonary infection that differs from the classical presentation of bacterial pneumonia in both its cause and clinical symptoms. Mycoplasma pneumoniae is a pleomorphic bacterium notable for its lack of a rigid cell wall. This structural characteristic imparts resistance to beta-lactam antibiotics and significantly influences the bacterium’s behavior within the human host.Other pathogens responsible for the disease include...