ST37 Klebsiella pneumoniae: development of carbapenem resistance in vivo during antimicrobial therapy in neonates

Aim: To investigate the mechanism leading to in vivo carbapenem resistance development in Klebsiella pneumoniae. Methods: Carbapenemase was detected using the modified carbapenem inactivation method. beta-lactamases resistant genes were identified by PCR and sequencing. Clonal relatedness was evaluated by random amplified polymorphic DNA and multiple locus sequence typing. The relationship between sequence typing and resistant genes was analyzed by using the chi-squared test. Results: All ST37 carbapenem-resistant isolates were bla(OXA-1) positive and all ST37 carbapenem-sensitive isolates were bla(OXA-1) negative at Stage I. A significant relationship between carbapenem resistance and bla(OXA-1) was observed. The bla(OXA-1) -positive rate was significantly higher in ST37 K. pneumoniae than others. Conclusion: This is the first study about the development of carbapenem resistance in vivo potentially mediated by bla(OXA-1) in ST37 K. pneumoniae among neonates.