| Abstract: |
SUMMARY AND CONCLUSIONNeonatal septicemia remains a major clinical problem in neonatology with high morbidity and mortality rates despite the progress in neonatal intensive care and antibiotics.The diagnosis of neonatal sepsis begins with clinical suspicion. The challenge for the neonatal practitioner is to decide which babies need empiric antibiotic therapy and for how long, a decision which is complicated by the common occurrence and nonspecific nature of sepsis-like symptoms in preterm infants.Isolation of an organism from a blood culture of a neonate with clinical symptoms of infection constitutes the definitive and gold standard diagnosis of sepsis. However, the delay in obtaining the results for at least 48-72 hours and the low sensitivity of its techniques which is recorded by some authors make it necessary to have other adjunctive tests to predict septicemia as early as possible in neonates with clinical signs and symptoms of infection and to rule out septicemia in those infants whose symptoms had resolved in less time than blood culturing.This study was designed to compare the utility of a 16S rRNA PCR assay to that of the conventional blood culture for detecting bacteria in blood obtained from neonates suspected of having septicemia.The present work was conducted in Microbiology & Immunology Department and Pediatric Department, Faculty of Medicine, Zagazig University. It included 50 neonates with provisional diagnosis (made by the clinicians) of neonatal septicemia and 25 non infected neonates as control group.For each neonate the following was done:1- Full history taking.2- Full clinical examination3- Routine investigations include complete blood cell count (CBC) and C- reactive protein.4- Conventional blood culture for isolation of the causative organism and its identification.5- Polymerase chain reaction (PCR) for detection of the 16S rRNA gene from blood of the septicemic neonate.The results of this study showed that:• Only thirty nine neonates (78 %) of those diagnosed as having or suspected to have septicemia on clinical backgrounds had given positive blood culture results. The most common isolated organisms were Klebsiella pneumoniae (41.02%), coagulase negative staphylococci (20.51%), E. coli and S. aureus (10.26 %). Klebsiella pneumoniae was the commonest isolated organism in early onset infection while coagulase negative staphylococcus was the commonest in late onset infection.• Forty cases of the patient group (80 %) and one of the control group (4 %) were positive by 16S rRNA PCR. Thirty eight cases were positive and nine cases were negative by both methods. Only one case was positive by blood culture and negative by PCR. However, 2 cases of the patient group and one of the control group were positive by PCR but negative by blood culture.• A high level of agreement between the two methodologies was found. The sensitivity, specificity, positive and negative predictive values for PCR were 97.4, 91.7, 92.7 and 97.1% respectively, and the accuracy was 94.7%. These values were superior to that of CRP. This indicates the usefulness of 16S rRNA PCR as a tool in diagnosis of neonatal septicemia.In conclusion:The validity of PCR as a diagnostic test in comparison to blood culture revealed high sensitivity, specificity, predictive value of positivity, predictive value of negativity, and diagnostic accuracy values.The most interesting in these results is the high negative predictive values that were calculated for the PCR assay compared to that of culture. This is indicative of the assay’s usefulness in accurately ruling out the diagnosis of bacterial sepsis in the uninfected term neonate admitted to the NICU for such an evaluation in few hours. The previous finding saves non infected neonates from unnecessary NICU admissions and intravenous antibiotic therapies which result in expensive hospital stays for infants, separate newborns from their mothers and create potential difficulties in breast-feeding, while exposing infants to antibiotics which are increasingly expensive and overused. These practices increase the financial burden on our health care system, and contribute to the increasingly serious problem of antibiotic resistance.Although blood culturing will not be completely replaced by a nucleic acid amplification technology anytime soon, as pure isolates remain essential for antimicrobial drug susceptibility testing, PCR does appear to be an excellent diagnostic test choice for a rapid means of ruling out bacterial sepsis in certain selected patient populations.RECOMMENDATIONSAccording to the results of this study, the following is recommended:• Regarding the risk factors1) Proper antenatal care to avoid premature labor and low birth weight.2) Minimal handling of neonates and avoid invasive techniques unless they are necessary and life saving.3) It is evident that most isolated pathogens are nosocomially acquired thus an infection control committee should be developed in hospital; job of this committee is to trace the sources of infection in nosocomial cases and to develop programs of health education about prevention of nosocomial infection.4) Restrict empirical use of broad spectrum antibiotics.• Regarding the use of PCR in diagnosis:To be applicable and cost effective this methodology should be used on broad spectrum at least in central referral hospitals, and an automated well standardized system of known validity should be developed on the base of large clinical outcome-based studies with the NICU clinicians to avoid as possible the many variables which affect the test.
|
|
|