Ultrastructural Changes in Clinical and Microbiota Isolates ofKlebsiella pneumoniaeCarriers of GenesblaSHV,blaTEM,blaCTX-M, orblaKPCWhen Subject toβ-Lactam Antibiotics
The aim of this study was to characterize the ultrastructural effects caused byβ-lactam antibiotics inKlebsiella pneumoniaeisolates. ThreeK. pneumoniaeclinical isolates were selected for the study with resistance profiles for third-generation cephalosporins, aztreonam, and/or imipenem and with different resistance genes for extended-spectrumβ-lactamases (ESBL) orKlebsiella pneumoniaecarbapenemase (KPC). TwoK. pneumoniaeisolates obtained from the microbiota, which were both resistant to amoxicillin and ampicillin, were also analyzed. In accordance with the susceptibility profile, the clinical isolates were subjected to subminimum inhibitory concentrations (sub-MICs) of cefotaxime, ceftazidime, aztreonam, and imipenem and the isolates from the microbiota to ampicillin and amoxicillin, for analysis by means of scanning and transmission electron microscopy. TheK. pneumoniaeisolates showed different morphological and ultrastructural changes after subjection toβ-lactams tested at different concentrations, such as cell filamentation, loss of cytoplasmic material, and deformation of dividing septa. Our results demonstrate thatK. pneumoniaeisolates harboring different genes that encode forβ-lactamases show cell alterations when subjected to differentβ-lactam antibiotics, thus suggesting that they possess residual activityin vitro, despite the phenotypic resistance presented in the isolates analyzed.