[Comparative analysis of the pathogens responsible for hospital acquired and community acquired late onset neonatal septicemia].

OBJECTIVE: Late onset neonatal septicemia (systemic infection after 72 hours of life) remains a major cause of neonatal morbidity and mortality. Early treatment with appropriate antibiotics is critical since infected infants can deteriorate rapidly. The aim of this study was to review the pathogens responsible for late onset neonatal septicemia (LONS) and their antimicrobial susceptibilities in order to guide the initial selection of appropriate antibiotics for infants with suspected LONS.

METHODS: A retrospective chart review of all cases with LONS seen in the neonatal intensive care unit (NICU) of Yuying Children's Hospital of Wenzhou Medical College from January 1, 2002 to December 31, 2005 was conducted. All cases were selected based on the clinical presentation and at least one positive result of blood culture. The basic clinical characteristics and the results of blood culture and antimicrobial susceptibilities were analyzed.

RESULTS: A total of 102 cases with LONS were identified. Among those 102 cases, 80 were community acquired (infants admitted from home and the blood culture was done on admission) and 22 were hospital acquired (infants became sick while in the NICU and the blood culture was done prior to use of antibiotics). The clinical presentations were non-specific. Compared to the infants with community acquired LONS, infants with hospital acquired LONS were usually born more prematurely (mean gestational age 33 +/- 3 vs 39 +/- 2 wks, t = 2.255, P < 0.01), with lower weight (mean weight 1.79 +/- 0.70 vs 3.23 +/- 0.67 kg, t = 8.818, P < 0.01) and with younger age (mean age 12 +/- 6 vs 16 +/- 7 days, t = 7.581, P < 0.05). Of the 102 cases, a total of 103 strains of bacteria were isolated. Among the pathogenic bacteria isolated, the most common were coagulase-negative Staphylococcus (CoNS) (50/103, 48.5%), followed by Klebsiella pneumoniae (16/103, 15.5%). The main pathogens for community acquired LONS were Staphylococcus species and Escherichia coli. The most important pathogen responsible for hospital acquired LONS was Klebsiella pneumoniae. Most (> 80%) of the Staphylococcus especially CoNS were resistant to common antibiotics such as penicillin, erythromycin and cefazolin. Significant numbers (6/9) of Staphylococcus aureus isolated were methicillin-resistant Staphylococcus aureus (MRSA). However, all of the Staphyloccus isolates were sensitive to vancomycin. Almost all (15/16) of the Klebsiella pneumoniae isolated were multi-drug resistant due to production of extended-spectrum beta-lactamases (ESBLs). They were sensitive only to a few antibiotics such as carbapenems, aminoglycosides and quinolones. There was also one strain of vancomycin-resistant Enterococcus (VRE). Furthermore, there was no a single case of late onset neonatal sepsis due to infection with group B Streptococcus (GBS).

CONCLUSIONS: The clinical manifestations of late onset neonatal sepsis are usually non-specific. GBS is not a significant pathogen responsible for community acquired LONS in the Wenzhou area. There are increasing numbers of multi-drug resistant bacterial species isolated from the newborn infants with late onset neonatal septicemia, which is most likely due the non-restricted use of antibiotics in the hospitals as well as in the communities. A routine blood culture should be taken from any newborn infant who is suspected of LONS and empirical use of appropriate antibiotics should be initiated as soon as the blood specimen for culture has been drawn. To reduce the occurrence of multi-drug resistant bacteria, the use of antibiotics especially the third generation cephalosporins in neonates should be restricted as much as possible.