Background: Nosocomial infection is a global public health problem, particularly by multi-drug resistant bacteria, increasing morbidity, mortality, and health care costs. The distribution of pathogens and antimicrobial sensitivity patterns change with time and vary among hospitals.

Objective: To determine and compare the bacterial pathogens causing nosocomial infections in pediatric patients and their susceptibility patterns between January 2000-December 2002 and January 2003-December 2005.

Material and Method: The bacterial pathogens and antimicrobial susceptibilities of children diagnosed as nosocomial infections at BMA Medical College and Vajira Hospital between January 2000 - December 2002 and January 2003- December 2005 were comparatively analyzed.

Results: 1,863 and 1,884 isolates were identified in 2000-2002 and 2003-2005, respectively. The common sites of infections were bloodstream (28.6%), lower respiratory tract (15.3%), skin and soft tissue (14.9%), and urinary tract (12.5%). The major isolated gram positive pathogens were S. aureus, coagulase negative Staphylococcus and Enterococus. The major gram negative pathogens were E. coli, P. aeruginosa, K. pneumoniae, Enterobacter spp. and Acinetobacter spp. Compared between 2000-2002 and 2003-2005, methicillin resistant S. aureus (MRSA) was decreased from 4.3% to 1.5% P. aeruginosa from 13.3% to 7.5%, Enterobacter spp. from 4.2% to 2.4%, Serratia spp. from 1.3% to 0.3%, but methicillin resistant coagulase negative Staphylococcus was increased from 5.6% to 10.5% and K. pneumoniae from 5.5% to 7.7%, (p<0.05). All gram positive cocci remained sensitive to vancomycin and linezolid. In 2003-2005, gram negative rods were less sensitive to 3^rd and 4^th generation cephalosporins and aminoglycosides than in 2000-2002. Sensitivity of gram negative rods to 3^rd and 4^th generation cephalosporins were not significantly different except Enterobacter spp. and Serratia spp., which were more sensitive to 4^th generation cephalosporin (p<0.05). Most gram negative pathogens (80-100%) were sensitive to ciprofloxacin except Acinetobacter spp. (61%). Carbapenems sensitivity were 100% except 92-100% for Enterobacter and 67-86% for P. aeruginosa, Acinetobacter spp. and Serratia spp.

Conclusion: The bacterial pathogens causing nosocomial infections and their susceptibility patterns change with time, so periodic surveillance are essential as a guide for more proper empirical therapy especially in serious or life threatening infections that need urgent appropriate antibiotics.

Keywords: Nosocomial bacterial infection, Epidemiologic study, Children, Susceptibility patterns