A Epidemiological Investigation Of Nosocomial Infections And The Characteristics Of Bacterial Colonization On Newborn Infants In NICU

Objective: Firstly, to investigate the incidence of nosocomial infections(NI) of newborn infants in NICU and to explore the risk factors and strategies of infection control.; Secondly, to find the prevalence of bacterial colonization of infants in NICU and to analyze the impact of antimicrobial agents on antibiotic resistance of the colonized bacteria on infants in NICU. Finally, to determine the influence of environment on bacterial colonization and infection though special survey on the outbreak of Klebsiella pneumoniae nosocomial infection, and provide the evidence for cutting off transmission passes and protecting susceptible population.Methods: The first study enrolled 638 hospitalized newborn infants from Apr 2003 to Dec 2004. The clinical data, such as the clinical manifestation, the condition of colonized bacteria of these infants were collected and the NI rates were calculated. The second study was made among 210 hospitalized newborn infants from Sep 2005 to Mar 2007. Bacterial colonization was examined by the method of nasopharyngeal and rectal swab culture immediately at admission and during hospitalization. In addition, cultures from nasopharyngeal and rectal swab also were obtained before and after antimicrobial agents administration. The clinical data and the result of bacterial culture surveillance was collected The last study was the special survey on an outbreak of Klebsiella pneumoniae's nosocomial infection in NICU in Dec 2006. A homology identification was performed on 11 Klebsiella pneumoniae strains of 7 infected infants and the environment sampling from 81 sampling points of the related medical personnel and medical facilities was carried out.Results: The overall NI rates were 11.6 per 100 patients. The overall NI patient-day rates were 14.9 per 1,000 NICU patient-days.The catheter-associated bloodstream infection rate were 18 per 1000 umbilical or central line-days. The ventilator-associated pneumonia infection rate were 63.3 per 1,000 ventilator-days. The most common infection was pneumonia (45.4%). The NI rate was 24.8% in the infants who acquired bacterial colonization in nasopharyngeal or rectal, and the NI rate were 1.9% in the infants without bacterial colonization correspondingly. There are highly significant difference between two groups (x~2=79.7, P＜0.001). Multiple logistic regression analysis revealed that 3 independent risk factions: the parenteral nutrition(OR=7.185, 95%CI 3.399～15.188),birth weight≤1500g(OR=3.30, 95%CI 1.100～9.963) and mechanical ventilation(OR=2.527, 95%CI 1.092～5.850). The bacteriology data showed the most commom colonized organisms in NICU were Klebsiella pneumoniae ss (36.8%), Escherichia coli (24.8%) and Enterococcus faecium (16.7%). The proportion about extended-spectrum beta-lactamase (ESBLs) production of the two main Enterobacters was 22%. The antibiotic resistant colonized bacteria on infants in NICU increased according to longer hospitalization and antibiotic usage may enhanced the antibiotic resistance of the colonized bacteria. It was showed that the most susceptible antibiotic for the Gram-negative organisms were meropenem, Cefoperazone/Sulbactam and Piperacillin/Tazobactam.Special survey on an outbreak of Klebsiella pneumoniae's nosocomial infection in NICU showed that all this 7 infected newborns had Klebsiella pneumoniae colonization in nasopharyngeal and/or rectal swab peri-infection period. The result of homology identification for 11 Klebsiella pneumoniae was highly homologisation and this outbreak of Klebsiella pneumoniae nosocomial infection was due to cross-transmission. The source of infection were the infants who had already infected or colonized with Klebsiella pneumoniae, the route of transmission may be hands of medical personnel in NICU. Space limited and medical personnel related insufficient was environment basement.Conclusions: Nosocomial infections have become a matter of major concem in NICU. It is important to investigate the high risk factors for nosocomial infections of newborn infants in NICU. Reducing the duration of the parenteral nutrition and the mechanical ventilation as early as possible and obtaining the message of individual bacterial colonization in NICU may contribute to reduce the incidence of nosocomial infections and provide reference of clinical rational antibiotic administration. Antibiotic usage may change the species of colonized bacterium and enhanced the antibiotic resistance of the colonized bacteria and result in changes in colonized bacteria species. Special survey should be performed when there was outbreaks of NI in order to isolate the source of infection, cut off the route of transmission and protect the susceptible population.