Prevalence of β-lactam antibiotic resistance of Escherichia coli isolated from a neonatal intensive care unit

Throughout the study period, 110 distinct E. coli strains were collected. Among these, 62 cases presented strains, which were resistant against at least one of seven ß-lactam antibiotics associated with conditions such as ventilator-associated pneumonia (35/62), catheter-associated urinary tract infection (14/62), necrotizing enterocolitis (7/62), skin infection (1/62), and neonatal septicemia (5/62). Resistance of E. coli isolates to seven β-lactam antibiotics ranged from 2.73-56.36%. In 62 strains (56.36%, 62/110), six genotypes (11 sub-genotypes) of 111 β-lactamase genes were identified. Conjugation experiments revealed two transconjugants carrying the bla_KPC-2 gene and two carrying the bla_OXA-1 gene, exhibiting resistance to carbapenems and other β-lactams. The plasmids of four strains were successfully conjugated and transferred to recipient E. coli C600. PCR of the transconjugant resistance genes revealed that two carried a bla_KPC-2 gene with a MIC increased up to 32-fold relative to the recipients, and the other two carried a bla_OXA-1 gene with a 32-fold increased MIC. For isolate ECK03 carrying bla_KPC-2, bla_CTX-M-64, bla_CTX-M-65, and bla_TEM-1, sequencing results showed that bla_KPC-2, bla_CTX-M-64, and bla_TEM-1 were harbored on a 114-kb pECK03_KPC-2 plasmid, whereas two identical bla_CTX-M-64 genes were harbored in E. coli isolate ECF13. CONCLUSION: These findings highlight the existence of E. coli β-lactam resistance within NICU populations, emphasizing the need for continual monitoring of β-lactamase isolates to facilitate effective antibiotic selection.