Neonatal sepsis is one of the leading causes of neonatal morbidity and mortality worldwide. [1] [2] It accounts for an estimated 30% - 50% of all neonatal deaths in the developing countries [2] [3] [4] . Globally, up to 20% of neonates develop sepsis and 1% die from sepsis-related causes. [1] [4] Important contributing factors in developing countries include delayed identification of causative etiological microorganisms, inappropriate treatment, outdated antibiotic guidelines, and the emergence of resistance strains. [5]

Neonatal sepsis refers to a clinical syndrome that is marked by signs and symptoms of infection in the first 28 days of life, with or without isolation of a pathogen. [4] [6] This can be categorized as early onset sepsis (EONS) and late-onset sepsis (LONS). EONS is defined as onset of signs and symptoms of infection within 72 hours of life and may be associated with isolation of a pathogen or not. In the LONS, signs and symptoms become apparent after 72 hours of life and categorization of EONS and LONS is to show the varying causes and pathophysiology of common isolates related to the time of onset of the condition. It is also crucial in prevention and treatment due to variations in etiological agents.

Recent reviews of causative agents of neonatal sepsis in the developed world revealed that group B Streptococcus (GBS) is a major cause of early-onset neonatal sepsis. [7] This is in contrast with the bacteriological profile of resource-limited settings where GBS rates are lower and Klebsiella pneumoniae, Staphylococcus aureus and Coagulase-negative staphylococci (CoNS) are the predominant pathogens of EOS. [7] [8] However, the main causative agent of LONS in neonatal intensive care unit reported globally remains coagulase-negative staphylococci (CoNS). [9]

In Nigeria, a wider spectrum of Gram-negative organisms including K. pneumoniae, Citrobacter spp., Escherichia coli, Enterobacter spp., Acinetobacter baumannii, Pseudomonas aeruginosa and Proteus spp. are prevalent in EONS. This observation was from a report of multicenter studies carried out in the Southwestern part of Nigeria. [10] In the Northwestern part of Nigeria, the frequently isolated organisms from neonatal sepsis were K. pneumoniae, Staphylococcus aureus, coagulase-negative Staphylococcus (CoNS) and E. coli. [4] [11]

Bacterial isolates responsible for neonatal sepsis seem to have acquired resistance to a number of antibiotics over the last few decades, and thus making treatment options extremely difficult. [12] [13] Global resistance to first-line empiric treatment regimens is on the increase, adding further complication to antimicrobial choices. [14] Studies from Nigeria have documented the emergence of drug resistance to multiple antibiotics howbeit mostly in an adult population. [4] [15]

Knowledge of prevalent bacterial isolates and their antibiotic susceptibility pattern is crucial when choosing the appropriate empirical therapy in order to decrease morbidity and mortality of neonatal sepsis. There is, however, a paucity of such data in most NICUs of our institutions. The objectives of this study were to: determine the prevalence of culture-positive neonatal sepsis in the NICU of LASUTH, its bacteriological profile and the antibiotic susceptibility pattern of the isolates.

Neonatal sepsis is considered as the leading cause of mortality and morbidity in the NICU. Several studies conducted in Nigeria with the same study population put the culture-positive rate between 28.1% and 35.6%. [3] [12] [20] This study which is first to be conducted in the NICU of LASUTH gives a culture-positive rate of 32.3%. This is also similar to studies conducted in Ghana and Nepal which gave the culture-positive rate of 28% [21] and 32.4% [22] respectively. Some studies, however, gave a much higher culture-positive rate. [4] This variation may be due to the volume of blood collected, the timing of blood collection and the laboratory technique employed.

The majority of the culture-positive sepsis were early onset neonatal sepsis (EONS) accounting for 78.6%. This finding is consistent with other studies which gave between 65% and 78% culture-positive rate in EONS. [3] [12]

In this study, the frequency of isolation of gram-positive bacteria 47 (84%) is much higher than gram negative bacteria 9 (16%). This is in sharp contract from other authors from Nigeria, where the preponderance of gram positive bacteria is not as high as reported in this study. [12] [20] [23] Studies from Ghana, Nepal and Germany also gave gram positive preponderance with 71% [22] , 72% [21] and 74% [24] respectively. However, some studies gave gram negative preponderance. [25] These differences may be due to the spectrum of causative organisms across geographical locations and the level of compliance with IPC measures in various hospital settings.

Staphylococcus aureus was the highest organism isolated from this study 25(44.6%) followed closely by Staphylococcus epidermidis 21 (37.5%). This finding combined the predominant pathogens from developing and developed countries together. S. aureus remains the dominant pathogen causing neonatal sepsis in developing countries accounting for 18% - 25% [12] [21] of all isolates from neonate with neonatal sepsis whereas in developed countries group B Streptococcus and CONS are the predominant pathogen isolated. [26] The reason for this may not be far from the cosmopolitan nature of Lagos and LASUTH itself that receives patient from all strata of the cosmopolitan society.

Among the gram-negative bacilli, the Klebsiella pneumoniae demonstrated maximum susceptibility to Meropenem and Cefepime (100% respectively) and fair susceptibility to Levofloxacin (67%) while showing maximum resistance to 3^rd generation cephalosporin, ciprofloxacin and gentamycin. This is in agreement with several studies from India, Egypt and Ghana where MDR Klebsiella pneumoniae were isolated and only sensitive to Meropenem and levofloxacin. [27] [28]

The pseudomonas demonstrated high susceptibility to Aminoglycosides, Levofloxacin, Cefepime and Piperacillin/tazobactam but high resistance to cefotaxime and ciprofloxacin. This finding is in concurrent with studies from Ghana [26] .

The Acinetobacter isolated from this study is generally susceptible except to ciprofloxacin, gentamycin and piperacillin/tazobactam. This is quite uncommon as most isolate of Acinetobacter baumanii in clinical settings are MDR strains.

The findings from this study revealed very encouraging results in that gram-positive bacteria isolate are susceptible to linezolid and vancomycin, which is also supported by the findings of other studies. [24] Whereas it showed high resistance to penicillin, cloxacillin, ciprofloxacin and cotrimoxazole. Vancomycin and linezolid could be considered as safe antibiotics of choice for the successful empiric treatment of suspected neonatal sepsis cases caused by gram positive bacterial infections.

The overall resistance of gram-positive isolates to cefotaxime is 34.5% while that of gram negative is 50%. This is a big threat to the unit as cefotaxime and amikacin are currently used as the first line empirical antibiotic. This will account for about 40% failure in first line antibiotic therapy.

The overall resistance to ciprofloxacin among gram positive and gram-negative isolate is 48% and 100% respectively. This is quite alarming as neonates with gram negative sepsis on 2^nd line antibiotic is likely to die thereafter.

In general, the high antibiotic resistance rates among bacterial isolates might be due to the emergence of antimicrobial resistance which is a normal evolutionary process for microorganisms that is accelerated by the selective pressure exerted by widespread antibiotic use and misuse; poor infection prevention and control measures in neonatal unit and lack of adherence to the unit protocol on Infection prevention and control.

The culture-positive rate in this study was 32.5%. Gram positive organisms were predominant accounting for 84.0%. Staphylococcus aureus was the predominant isolate accounting for 44.6%. Both gram positive and gran negative organisms showed high resistant to commonly used antibiotic.

This study will recommend the combination of vancomycin and meropenem as the 2^nd line antibiotic. However, continuous surveillance and periodic evaluation is necessary.

This study had some limitations. Firstly, is the retrospective nature of the study that is based on the data collected form laboratory records which lack information about the neonates’ hospitalization date, clinical information, and treatment outcome. Second, this study was conducted only at the inborn session of the neonatal unit of the hospital; therefore, the antibiotic resistance patterns observed in our study might not generalize the entire state and country at large even though other reports in the country supported our findings.

It is already known that bacterial are the commonest cause of neonatal sepsis and also that this bacterial are becoming resistance to commonly used antibiotic.

This study is able to identify the common bacterial isolate of neonatal sepsis in our facility and it also reveals the resistance profile of such bacterial isolates.

Author 1 (Oluwadamilare Afolabi Obe): Conceptualization, design, data collection, data analysis, funding, literature review, and writing.

Author 2 (Wasiu Bamidele Mutiu): Conceptualization, design, data collection, data analysis, funding, critical review.

Author 3 (Peter Odion Ubuane): Conceptualization, design, sample collection, literature review.

Author 4 (Ibrahim Oladipupo Odulate): Data collection, laboratory work, data analysis, literature review.

The authors declare no conflicts of interest.

Obe, O.A., Mutiu, W.B., Ubuane, P.O. and Odulate, I.O. (2023) Bacteriological Profile and Antibiotic Susceptibility Pattern of Common Isolates of Neonatal Sepsis in a Tertiary Hospital from Lagos, Nigeria. Open Access Library Journal, 10: e9558. https://doi.org/10.4236oalib.1109558