Changing trend of empirical antibiotic regimen: experience of two studies at different periods in a neonatal intensive care unit in Tehran, Iran.

Bacterial sepsis is one of the most common causes of mortality and morbidity in neonates. It has been recognized a gradual change in spectrum of organisms responsible for neonatal sepsis. In this study we have evaluated changing trend of incidence and antibiotic susceptibility in neonatal late - onset sepsis (LOS) in 2-periods. This study is based on results of blood culture in neonatal late-onset sepsis, in 2--periods study throughout 12 - years. Neonatal LOS was defined as clinical signs suggestive of infection with a positive blood culture (B/C) after 72 hrs of birth. During first study (period: 1990-1992), the most common bacteremia in LOS was staphylococcus aureus (staph aureus) (34%). Overall gram- negative bacteria (GNB) were the predominant organism (66%). It was shown that 60% of GNB were resisted to gentamicin and 3% to amikacin, while in case of gram-positive bacteria (GPB); about 95% were resisted to ampicillin and 28% to cephalothin. In the second study (period: 2004-2007), the vast majority (56.6%) of septic cases were caused by GNB. The most common cause of late- onset sepsis was klebsiela p. (31%). The GPB were resistant to cephalothin (90%). There has been a dramatic increase resistance to cephalothin and aminoglycosides and 3rd -generation cephalosporins. The combination of cephalothin plus amikacin in suspected LOS was no longer the effective therapeutic regimen in our neonatal intensive care unit (NICU). Now, it seems the best choice for empiric antibiotic regimen in suspected LOS is the combination vancomycin plus amikacin. Constant surveillance is important to guide empirical antibiotic therapy and changes in trends.