This was a retrospective review of all bacterial isolates in blood cultures obtained from the neonatal unit at CMJAH between 1 June 2009 and 30 June 2010. This is a tertiary care neonatal unit which cares for both inborn and outborn neonates. A list of positive blood cultures was obtained from the National Health Laboratory Service (NHLS) Computer Data Warehouse. Information obtained included identification of the organism(s) isolated and the antibiotic sensitivity of each organism. A neonate was defined as being ≤28 days of age. Only blood stream infections (BSIs) were included in the audit. Babies with clinical or laboratory signs suggestive of sepsis but with negative blood cultures were excluded. Other infections, such as pneumonia, conjunctivitis, urinary tract infection, meningitis, phlebitis, skin abscess, and omphalitis, were excluded. Infections were classified as early onset (EOS) if the positive culture was obtained before 72 hours of life and late onset (LOS) if the positive blood culture was obtained after 72 hours of life. A sepsis-related death (SRD) was diagnosed if the baby died within 5 days of developing a BSI. If more than one pathogenic organism was isolated from a single culture this was classified as a polymicrobial infection.
Blood cultures were performed on babies with a history of obstetric risk factors (e.g., chorioamnionitis, prolonged rupture of membranes) or who presented with signs of suspected sepsis, such as apnoea, lethargy, temperature instability, respiratory distress, hypotension, poor feeding, glucose imbalance, and seizures. A sterile 0.5
mL blood sample was sent for culture prior to commencing antibiotic therapy, together with a full blood count and C reactive protein (CRP). The CRP was repeated after 24 hours.
During the study period, EOS was treated empirically with penicillin and amikacin. Empiric therapy for LOS was modified in consultation with the microbiology unit in response to the changing antibiograms prevalent in the unit at the time. Positive blood cultures were each reviewed with the microbiology unit and a joint decision was taken on the significance of the organism and appropriate de-escalation of antibiotic therapy was instituted. A BSI was diagnosed if a pathogenic organism was isolated, the baby was clinically ill, and there were nonspecific laboratory signs of sepsis including a raised CRP, abnormal white cell count, or platelet count. Certain organisms, including Micrococcus species, Bacillus species, and Corynebacterium species, were classified as contaminants. CoNS were regarded as contaminants if the baby was clinically well, the CRP was normal, and there were no indwelling central catheters. Organisms classified as contaminants were excluded from the analysis. If the same organism was isolated from the same patient within 7 days, this was considered to be a single episode of BSI.
Limited clinical and demographic information on each patient was obtained from a neonatal computer database. This included obstetric risk factors for infection, antenatal care, use of antenatal corticosteroids, outcome, duration of hospitalization, gender, birth weight, gestational age, place of birth, birth asphyxia, HIV exposure, nasal continuous positive airways pressure (NCPAP), mechanical ventilation, necrotizing enterocolitis (NEC) grade 2 and 3 [6
], surgery, and intraventricular haemorrhage (IVH) grade 3 and 4 [7
]. Each pathogenic organism isolated was considered as a separate episode of BSI—if 2 pathogenic organisms were isolated from a single patient, that patient's clinical information would be entered for each separate organism. Variables were entered as yes, no, or unknown. Information regarding total patient days and total live births during the study period was obtained from admission and labour ward statistics. The live births included those from Hillbrow Community Health Centre and Alexandra Clinic.
Statistical analysis was done using SPSS version 19 (IBM). Categorical variables were described as frequencies and percentages and compared using Chi-square analysis. Fisher's exact test was used in those instances where the anticipated size of a cell was below 5. If normally distributed, continuous variables were described as mean and 95% confidence intervals and means were compared using the unpaired t-test. If the distribution was not normal, the data was described using median and interquartile range and compared using Mann-Whitney U analysis. All data was compared considering SRD, EOS, and Gram stain as outcome variables. Significant differences are reported.
The study was approved by the Human Research Ethics Committee of the University of the Witwatersrand.