Objective:Pseudomonas aeruginosa is one of the leading pathogen causing healthcare-associated infections, particularly in immunocompromised and critically ill patients. The development of carbapenem resistance in P. aeruginosa infections is worrisome. Data specifically comparing the susceptibility of the three available carbapenems are lacking in the Indian subcontinent.Materials and Methods:We evaluated the minimum inhibitory concentrations (MICs) of the three commonly used carbapenems– imipenem, meropenem, and doripenem against, 435 P. aeruginosa isolates obtained from respiratory samples and compared their susceptibility patterns to determine the best possible carbapenem among those available that may be used in combination regimes.Results:Overall, 222 (51.0%) of isolates were susceptible to doripenem followed by imipenem 206 (47.3%) and meropenem 195 (44.8%), respectively. Two hundred and sixty-two (60.23%) strains were intermediate or resistant to at least one carbapenem. The MIC90 of all three carbapenems was >32 μg/ml while the MIC50 of meropenem was 16 μg/ml which was higher than MIC50 of both imipenem (4 μg/ml) and doripenem (2 μg/ml).Conclusion:Our study revealed that doripenem exerted better in vitro activity against the tested bacteria compared to imipenem and meropenem, but the difference was not statistically significant.

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Introduction: Urinary tract infections (UTI) are the most common bacterial infections affecting humans.. Fosfomycin has been approved for use in uncomplicated UTI caused by E. coli and Enterococcus. However, data regarding sensitivity of organisms causing hospital acquired or complicated UTI is scarce worldwide. We aimed to determine the in vitro sensitivity of drug resistant organisms causing hospital acquired and complicated UTI towards fosfomycin. Materials and Methods: Over a 6 month period, urine samples were processed as per standard microbiological protocols. Bacterial isolates were identified by routine microbiological methods followed by automated methods. Antibiotic sensitivity tests were done for different antibiotics. Fosfomycin sensitivity was tested by disc diffusion assay and minimum inhibitory concentration (MIC) was determined by E test method. Results: A total of 248` organisms causing hospital acquired and/or complicated UTI were isolated of which E. coli 88(35.48%) was most common followed by K. pneumoniae 78(31.45%) and P. aeruginosa 64(25.80%). Of 248, 92.74% (230/248) isolates were sensitive to fosfomycin. All the E. coli isolates were sensitive to fosfomycin with a low MIC (range 0.064-16 mg/L) while 97.43% (76/78) of the K. pneumoniae and 71.87% (46/64) P. aeruginosa of isolates were sensitive with a higher MIC (range 0.5-32 mg/L and 6-64mg/L respectively). Fosfomycin MIC geometric mean among E. coli, K. pneumoniae and P. aeruginosa was; 1.05, 7.19 and 19.61 mg/L respectively.  K. pneumoniae and P. aeruginosa showed a significantly higher geometric mean MIC compare to E. coli (P <0.0001). Conclusions: This study suggests that fosfomycin has the potential to replace the parenteral antibiotics for treating complicated or hospital acquired lower UTI especially in case of Enterobacteriaceae.