An antibiotic policy to prevent emergence of resistant bacilli

Background Fear of infection in neonatal intensive care units (NICUs) often leads to early use of empiric broad-spectrum antibiotics, a strategy that selects for resistant bacteria. We investigated whether the emergence of re sistant strains could be halted by modifying the empiric antibiotic regimen s to remove the selective pressure that favours resistant bacteria. Methods Two identical NICUs were assigned to different empiric antibiotic r egimens. On unit A, penicillin G and tobramycin were used for early-onset s epticaemia, flucloxacillin and tobramycin were used for late-onset septicae mia, and no broad-spectrum beta-lactam antibiotics, such as amoxicillin and cefotaxime were used, In unit B, intravenous amoxicillin with cefotaxime w as the empiric therapy. After 6 months of the study the units exchanged reg imens. Rectal and respiratory cultures were taken on a weekly basis. Findings There were 436 admissions, divided equally between the two regimen s (218 in each), Three neonates treated with the penicillin-tobramycin regi men became colonised with bacilli resistant to the empirical therapy used v ersus 41 neonates on the amoxicillin-cefotaxime regimen (p < 0.001). The re lative risk for colonisation with strains resistant to the empirical therap y per 1000 patient days at risk was 18 times higher for the amoxicillin-cef otaxime regimen compared with the penicillin-tobramycin regimen (95% CI 5.6 -58.0). Enterobacter cloacae was the predominant bacillus in neonates on th e amoxicillin-cefotaxime regimen, whereas Escherichia coli predominated in neonates on the penicillin-tobramycin regimen. These colonisation patterns were also seen when the units exchanged regimens. Interpretation Policies regarding the empiric use of antibiotics do matter in the control of antimicrobial resistance, A regimen avoiding amoxicillin and cefotaxime restricts the resistance problem. of antimicrobial and cefot axime.