Piergiorgio Cojutti1, Assunta Sartor2, Matteo Bassetti3, Claudio Scarparo2, Federico Pea4. 1. Institute of Clinical Pharmacology, Santa Maria della Misericordia University Hospital, Azienda Sanitaria Universitaria Integrata, Udine, Italy; Department of Medicine, University of Udine, Udine, Italy. 2. Microbiology Laboratory Unit, Santa Maria della Misericordia University Hospital, Azienda Sanitaria Universitaria Integrata, Udine, Italy. 3. Department of Medicine, University of Udine, Udine, Italy; Infectious Diseases Clinic, Santa Maria della Misericordia University Hospital, Azienda Sanitaria Universitaria Integrata, Udine, Italy. 4. Institute of Clinical Pharmacology, Santa Maria della Misericordia University Hospital, Azienda Sanitaria Universitaria Integrata, Udine, Italy; Department of Medicine, University of Udine, Udine, Italy. Electronic address: federico.pea@asuiud.sanita.fvg.it.
Abstract
OBJECTIVES: The aim of this study was to assess the minimum inhibitory concentration (MIC) distribution for meropenem and other antimicrobials with Gram-negative activity against Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC-Kp) clinical isolates collected at a tertiary hospital in Italy between 2013-2016. METHODS: The antimicrobial susceptibility of KPC-Kp strains was tested by the broth microdilution method using customised 96-well plates and the results were interpreted according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) recommendations. RESULTS: Among 169 consecutive KPC-Kp clinical isolates, 45 (26.6%) were susceptible to meropenem (MIC≤2mg/L). Among the 124 meropenem-resistant isolates, 73 (58.9%) had a meropenem MIC between 16-64mg/L. The overall resistance rate for the other antimicrobials tested was very high both for ciprofloxacin and levofloxacin (99.0%), was moderate for amikacin (37.4%) and was low for gentamicin (11.2%), colistin (8.2%) and tigecycline (7.7%). Aminoglycosides had a dichotomous behaviour in relation to meropenem MIC increase. The resistance rate for gentamicin remained <20% across all meropenem MICs; conversely, that for amikacin increased from <20% in the presence of meropenem MIC≤8mg/L up to ca. 80% in the presence of meropenem MIC≥64mg/L. Resistance rates for tigecycline and colistin remained <20% in the presence of meropenem MICs up to 64mg/L. CONCLUSION: The overall susceptibility rates of antimicrobials with Gram-negative activity may vary greatly among KPC-Kp clinical isolates. A tight relationship between meropenem MIC increase and the resistance rate for amikacin was documented.
OBJECTIVES: The aim of this study was to assess the minimum inhibitory concentration (MIC) distribution for meropenem and other antimicrobials with Gram-negative activity against Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC-Kp) clinical isolates collected at a tertiary hospital in Italy between 2013-2016. METHODS: The antimicrobial susceptibility of KPC-Kp strains was tested by the broth microdilution method using customised 96-well plates and the results were interpreted according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) recommendations. RESULTS: Among 169 consecutive KPC-Kp clinical isolates, 45 (26.6%) were susceptible to meropenem (MIC≤2mg/L). Among the 124 meropenem-resistant isolates, 73 (58.9%) had a meropenem MIC between 16-64mg/L. The overall resistance rate for the other antimicrobials tested was very high both for ciprofloxacin and levofloxacin (99.0%), was moderate for amikacin (37.4%) and was low for gentamicin (11.2%), colistin (8.2%) and tigecycline (7.7%). Aminoglycosides had a dichotomous behaviour in relation to meropenem MIC increase. The resistance rate for gentamicin remained <20% across all meropenem MICs; conversely, that for amikacin increased from <20% in the presence of meropenem MIC≤8mg/L up to ca. 80% in the presence of meropenem MIC≥64mg/L. Resistance rates for tigecycline and colistin remained <20% in the presence of meropenem MICs up to 64mg/L. CONCLUSION: The overall susceptibility rates of antimicrobials with Gram-negative activity may vary greatly among KPC-Kp clinical isolates. A tight relationship between meropenem MIC increase and the resistance rate for amikacin was documented.