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In-vitro activity of 29 antimicrobial agents against penicillin-resistant and -intermediate isolates of Streptococcus
O Manzor1, J Pawlak, L Saravolatz
1St John Hospital and Medical Center, Detroit, MI 48236, USA. omanzor@mindspring.com
Abstract:
Antibiotic resistance among isolates of Streptococcus pneumoniae is increasing worldwide. Optimal therapy, though unknown, should be guided by in-vitro susceptibility testing. Currently, vancomycin is the only approved antibiotic that is universally active against multiresistant S. pneumoniae. In-vitro activities were determined for 29 antimicrobial agents against 22 penicillin-intermediate S. pneumoniae (PISP) and 16 penicillin-resistant S. pneumoniae (PRSP) isolates. MICs were determined in cation-adjusted Mueller-Hinton broth with 3% lysed horse blood in microtitre trays. Antimicrobial classes tested included cephalosporins, penicillin, aminopenicillins, macrolides, quinolones, carbapenems and other antimicrobial agents. Among the classes of antimicrobial agents tested, wide differences in susceptibility were demonstrated for both PISP and PRSP. Of the cephalosporins, ceftriaxone and cefotaxime demonstrated the best in-vitro activity for both PISP and PRSP. Of the quinolones, clinafloxacin and trovafloxacin showed the greatest in-vitro activity. Rifampicin and teicoplanin demonstrated excellent in-vitro activity. Promising in-vitro results of newer agents, such as quinupristin/dalfopristin, ramoplanin, teicoplanin and linezolid may justify further evaluation of these agents in clinical trials.
Insights
Antibiotic resistance in Streptococcus pneumoniae is rising globally. This study evaluated 29 antimicrobial agents against resistant strains, finding ceftriaxone, cefotaxime, clinafloxacin, and trovafloxacin showed promising in-vitro activity.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Increasing global antibiotic resistance in Streptococcus pneumoniae necessitates updated treatment guidelines.
- Vancomycin is currently the sole approved antibiotic effective against multidrug-resistant S. pneumoniae.
- In-vitro susceptibility testing is crucial for guiding optimal therapy against resistant S. pneumoniae isolates.
Purpose of the Study:
- To determine the in-vitro activity of 29 antimicrobial agents against penicillin-intermediate S. pneumoniae (PISP) and penicillin-resistant S. pneumoniae (PRSP) isolates.
- To identify effective antimicrobial agents for treating infections caused by multidrug-resistant S. pneumoniae.
Main Methods:
- In-vitro susceptibility testing was performed on 22 PISP and 16 PRSP isolates.
- Minimum Inhibitory Concentrations (MICs) were determined using cation-adjusted Mueller-Hinton broth with lysed horse blood in microtitre trays.
- A wide range of antimicrobial classes were evaluated, including cephalosporins, penicillins, macrolides, quinolones, and carbapenems.
Main Results:
- Significant variations in susceptibility were observed across different antimicrobial classes for both PISP and PRSP isolates.
- Ceftriaxone and cefotaxime demonstrated the best in-vitro activity among cephalosporins against both PISP and PRSP.
- Clinafloxacin and trovafloxacin exhibited the highest in-vitro activity among the quinolones tested.
- Rifampicin and teicoplanin showed excellent in-vitro activity.
- Newer agents like quinupristin/dalfopristin, ramoplanin, teicoplanin, and linezolid displayed promising results.
Conclusions:
- Ceftriaxone, cefotaxime, clinafloxacin, trovafloxacin, rifampicin, and teicoplanin are effective against resistant S. pneumoniae in vitro.
- Emerging agents such as quinupristin/dalfopristin, ramoplanin, teicoplanin, and linezolid warrant further clinical investigation for treating resistant S. pneumoniae infections.