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Susceptibility of Pseudomonas maltophilia to antimicrobial agents, singly and in combination
Abstract:
Pseudomonas maltophilia is resistant to most of the commonly used antimicrobial agents including those active against Pseudomonas aeruginosa. The susceptibility of 14 clinical isolates of P. Maltophilia to 18 antimicrobial agents was determined by broth dilution testing. All organisms were susceptible to trimethoprim-sulfamethoxazole (TMP-SMZ), minocycline, and LY127935. A total of 87 and 79% of the organisms were susceptible in vitro to colistin and chloramphenicol, respectively. With the exception of sisomicin, the organisms were resistant to the aminoglycosides. Of 21 combinations of antimicrobials examined for synergy, only the combination of TMP-SMZ with carbenicillin was consistently (86%) synergistic in vitro. Supplementation of the testing media with calcium and magnesium increased the minimal inhibitory concentrations for the aminoglycosides, the penicillins, and TMP-SMZ against P. maltophilia.
Insights
Pseudomonas maltophilia exhibits resistance to many antibiotics. However, trimethoprim-sulfamethoxazole (TMP-SMZ) and minocycline show consistent effectiveness against this pathogen.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Pseudomonas maltophilia (now often classified as Stenotrophomonas maltophilia) is an opportunistic pathogen known for its intrinsic resistance to many antibiotics.
- This resistance poses significant challenges in treating infections caused by this bacterium, particularly in immunocompromised patients.
Purpose of the Study:
- To determine the in vitro susceptibility of clinical isolates of Pseudomonas maltophilia to a range of antimicrobial agents.
- To evaluate potential synergistic combinations of antibiotics against P. maltophilia.
Main Methods:
- Broth dilution testing was employed to assess the susceptibility of 14 clinical isolates of P. maltophilia.
- Eighteen different antimicrobial agents and 21 antimicrobial combinations were tested for their efficacy.
Main Results:
- All isolates were susceptible to trimethoprim-sulfamethoxazole (TMP-SMZ), minocycline, and LY127935.
- High susceptibility rates were observed for colistin (87%) and chloramphenicol (79%).
- The combination of TMP-SMZ and carbenicillin demonstrated consistent in vitro synergy (86%).
Conclusions:
- Trimethoprim-sulfamethoxazole (TMP-SMZ) and minocycline are effective agents against Pseudomonas maltophilia.
- The synergistic activity of TMP-SMZ with carbenicillin suggests a potential therapeutic strategy for P. maltophilia infections.