Study Design
We used a retrospective cohort study design to explore the use of cluster analysis in depicting antibiotic management of neonatal sepsis and its association with newborns' outcomes in a limited resources NICU.
Ethical approval
The research was performed following the ethical standards of the 1964 Declaration of Helsinki and was approved by the Ethical Committee of St. Luke Catholic Hospital (SLCH) on the 14th of September (protocol number 1293/2021).
Study setting
SLCH is a referral hospital located in Wolisso Town, about one hundred km from the capital Addis Ababa. It is situated in the South-West Shoa Zone (SWSZ) of the Oromia region (Ethiopia), that has an estimated population of 1,311,406 inhabitants, of which 15% are under five years of age [12]. SLCH catchment area includes the woreda of Ameya, Wenchi, Waliso rural, Woliso town, Becho, and Goro representing the reference hospital for 743.797 individuals. The number of deliveries assisted at SLCH was 4455 in 2019 and 4015 in 2020. The SLCH NICU has 16 beds with an annual average bed-occupation rate of 112% in 2020 [13]. Vital parameters and blood oxygen saturation are routinely monitored, and respiratory support consists of intranasal oxygen, bubble CPAP and electric CPAP.
Population
All newborns admitted in NICU between 1st April 2021, and 31st July 2021 and discharged with the diagnosis of probable neonatal sepsis were included. Exclusion criteria were missing information about antibiotic management or regarding the type of neonatal sepsis.
Operational definitions
Probable neonatal sepsis was defined as the presence of two or more of the following clinical signs and symptoms: hypo-hyperthermia (BT <35.5°C or >37.5°C), heart rate >180 or <100 bpm, respiratory rate >60 bpm with grunting or desaturations, lethargy or altered mental status, glucose intolerance (plasma glucose >10mmol/l), feed intolerance; plus at least one of the following laboratory results at birth: leukocytosis (WBC count >34,000*109/l), leukopenia (WBC count <5,000*109/l), thrombocytopenia (platelets count <100,000*109/l) [14].
Neonatal sepsis was defined as early-onset (EOS) if the sepsis symptoms started within 72 hours of birth and late-onset (LOS) if after 72 hours from birth [2,3].
Data collection
For each subject, the following data were collected: sex, age and weight at admission, date of hospital admission and of hospital discharge, number of antenatal care (ANC) visits, mode of delivery, delivery place, presence of maternal chorioamnionitis, occurrence of premature rupture of membranes (PROM), maternal pre-eclampsia/eclampsia, Apgar score at 1st, 5th, 10th minute, respiratory status at birth, use of oxygen and/or positive pressure ventilation with AMBU bag at birth. We also collected data on type of neonatal sepsis, type of every antibiotic used during hospitalization, start and end date of every antibiotic type, presence of RD, number, type and length of every respiratory support device used during hospitalization and the outcome at NICU discharge.
Antibiotic regimens
The antibiotic management protocol at the SLCH NICU had three different antibiotic lines. The first two lines are based on WHO and Ethiopian guidelines [15]: the first based on Ampicillin plus Gentamicin and the second line includes Ampicillin (higher dosage) – or Cloxacilline if any sign or suspect of staphylococci infection, plus Cefotaxime or Ceftazidime as the first choice - or Ceftriaxone if the previous two are not available. The third line uses Ciprofloxacin plus Cloxacilline (or Vancomycin). Ciprofloxacin was empirically chosen as a third line because in Addis Abeba Central Hospital, where blood cultures and antibiotic resistance profile are available, several cases of resistance to gentamicin and cephalosporins but high sensitivity to meropenem and ciprofloxacin were found [16]. First line duration of antibiotic treatment was recommended for 5-7 days. If no improvement was observed in the first 48/72 hours, the second line regimen was started. The third line was under specialist prescription based on the clinical status of the newborns.
Study endpoints
The primary endpoints were the number of newborns assigned to each cluster of antibiotic line switch and the development of respiratory distress and death in NICU. The secondary endpoints were the proportion of patients diagnosed with neonatal sepsis and the frequencies of early and late-onset neonatal sepsis subtypes.
Statistical analysis
For descriptive purposes, frequency rates and percentages were used for categorical variables and medians with interquartile range (IQR) for continuous variables. Proportions for categorical variables were compared by the χ2 and Fisher’s exact test. Continuous variables were compared via Mann-Whitney-U non-parametric test.
In order to explore the effect of the antibiotic management clusters and the clinical variables on RD and mortality, two logistic regression models were fitted for multivariable analyses. In the first model, the occurrence of RD was the response variable while the type of neonatal sepsis, age, weight, and antibiotic management clusters were included as potential determinants. Outcome at NICU discharge (dead or alive) was the second response variable, with type of neonatal sepsis, age, weight, antibiotic management cluster, and presence of RD as potential determinants. Results were presented as odds ratio (OR). Additionally, the main clinical features were tested between clusters through χ2 or Fisher’s exact test and Mann-Whitney-U non-parametric test. Dunn’s test with a Bonferroni adjustment was used for nonparametric pairwise multiple comparisons. Post-hoc multiple comparison between clusters in the logistic regressions was carried out through Tukeys' test.
The optimal number of antibiotic management clusters to be imputed in the algorithm was evaluated through silhouette coefficient fitted on Gower distance computed as the average of partial dissimilarities across individuals included in the study. Variables included to be used in the Gower distance estimation were the type of antibiotics used as the first, second, or third line, respectively, and the length in days of every antibiotic line. The Gower distance was selected because data had both continuous and categorical variables, and it allows for mixed variables to be used simultaneously. The individuals were assigned to the different clusters through the partitioning around medoids technique with the k-medoids algorithm fitted on the previous computed optimal number of clusters and Gower distance [17].
A p-value <0.05 was considered significant. All analyses were performed using the R software (version 4.1.1) [18].