Background

The definition of neonatal sepsis is heterogenous and has undergone through a lot of metamorphosis over the years. The term neonatal sepsis ((NS) is used to designate a systemic condition of bacterial, viral, or fungal origin that is associated with haemodynamic changes and other clinical manifestations and results in substantial morbidity and mortality [1]. In 2005, Goldstein et al. defined NS as systemic inflammatory response syndrome (SIRS) in the presence or as a result of suspected or proven infection occurring in the first 28 days of life and paediatric SIRS with accompanying temperature or leukocyte abnormalities [2]. Therefore, NS encompasses various systemic infections of the newborn such as meningitis, pneumonia, arthritis, osteomyelitis, and urinary tract infections [3, 4]. Seventy-five percent of global neonatal mortality burden is caused by prematurity and low birth weight, infections, asphyxia, and birth trauma with neonatal infection alone contributing 18% [5, 6]. The low-income earning countries account for 80% of the world’s neonatal death burden [7], and in Nigeria, the Northwest and Kaduna state has the highest burden of mortality with Neonatal Mortality Rate (NMR) of 46 and 63 per 1000 live births, respectively [8]. Serious infections (sepsis, pneumonia, and meningitis) accounted for 44% of such deaths with NS alone accounting for 23–30% [9]. Neonatal sepsis is broadly classified into early or late-onset based on the age at onset of clinical features. This classification helps to guide antibiotic therapy as it implies differences in the presumed mode of transmission, differing aetiology, and pathophysiology of the pathogens [10,11,12].

Early-onset sepsis (EOS) is variably defined as sepsis within zero to 48–72 h of birth, while some define it as that which occurs within the first 7 days of life [3, 13, 14] It may present with subtle early signs or as a fulminating septicaemic illness with pneumonia being the commonest focal infection [3]. It reflects transplacental or more frequently, ascending infections from the maternal genital tract [3, 4, 15].

Infection occurring 48–72 h after birth [3, 11, 15] or after 7 days and up to 30 days of life [14, 16] is termed late-onset sepsis (LOS). It is acquired either as nosocomial (hence the term “Health Care Acquired Infection” HCAI) or community-acquired infection and is frequently associated with meningitis [3, 4, 14].

The risk factors for NS are numerous and are dependent on the type of sepsis and environment, while in developed countries, factors such as maternal GBS colonization and advanced invasive procedures are top-most; developing countries are still battling with factors related to poor hygiene.

Several pathogens have been associated with sepsis in the neonatal period. The predominant agents are bacterial, but viruses have also been associated with fulminant infection with high mortality [17]. In most developing countries, gram-negative bacteria remain the major source of infection, while in developed countries, it is gram-positive bacteria [18].

The common organisms implicated in EOS include Group B streptococci, Escherichia coli, Streptococcus viridans, Enterococci, Staphylococcus aureus, Pseudomonas aeruginosa, and other gram-negative bacilli, while for LOS, it includes Coagulase-negative Staphylococci (CoNS), Staphylococcus aureus, Escherichia coli, Klebsiella pneumonia, Enterococci, Pseudomonas aeruginosa, and Group B streptococci [14]. Work done by various authors in different parts of the world shows differences in the frequency of causative organisms. The pathogenesis of sepsis is complex, and the prevailing, although debated theory, is that sepsis occurs when the host response overwhelms the protective mechanisms in place, resulting in a superimposing injury to the patient in addition to the infection that initially triggered this response [18]. Clinical symptoms and signs of sepsis in newborns vary with gestational age and severity of the infection. However, in most cases, features of both EOS and LOS are subtle and non-specific and may evolve [19]. Sepsis may be fulminant, leading to death in several hours from multiorgan failure, or maybe more protracted. The most frequent features are lethargy, poor feeding, abdominal distention, prolonged capillary filling time, glucose intolerance, and unexplained persistent acidosis [20]. The gold standard investigation for diagnosis of NS remains blood culture although it is time-consuming, cumbersome [15, 21], and has low sensitivity (25%) [22]. Supporting investigations include culture of bloody fluids, complete blood count, inflammatory markers, and advanced tests like polymerase chain reaction and MALDI-TOF Mass Spectrometry. Prompt and effective therapy is important as neonates with infection often deteriorate rapidly. It involves supportive care, antimicrobial therapy, and host defence modulation [20].

The aim of the study is to determine the sepsis type, risk factors, mode of presentations, implicated organisms and their sensitivities, and the outcome of proven neonatal sepsis in term neonates in our centre.

Methods

Study location

The study was conducted at the neonatal unit of Ahmadu Bello University Teaching Hospital (ABUTH)—a tertiary hospital located in Zaria, Kaduna State. The unit has a 30-bed capacity across its in-born and out-born wards and an average number of 900 admissions per year over serving Kaduna and other neighbouring states.

Study design

It was an observational prospective cross-sectional study conducted over a 10-month period from October 2018 to July 2019 of term neonates that were evaluated for sepsis.

Study population

Consecutive term neonates presenting with at least three or more risk factors and/or clinical features suggestive of sepsis and admitted into the neonatal unit were recruited for the study.

Ethics

Ethical approval for the study was obtained from Ahmadu Bello University Teaching Hospital Health Research Ethics Committee with ref no ABUTH/HREC/CL/05. Parental consent was obtained for all neonates before recruitment.

Data collection

A structured questionnaire was used to obtain the socio-demographic characteristics and details of perinatal events from patients’ relatives/carers. Their samples were taken at admission for blood culture, complete blood count (CBC), C-reactive protein (CRP), and procalcitonin (PCT).

Bacterial identification and susceptibility testing

Blood specimen (3 ml) from neonates with presumptive bloodstream infections were taken under aseptic condition and immediately transferred blood culture bottle containing 15 ml of Brain Heart Infusion (BHI) and incubated aerobically at 37 °C for 24 h. Broth with signs of growth were immediately removed and sub-cultured on 5% Sheep blood and MacConkey agar plate and incubated in the same condition as the broth above. Growths from both culture plates were examined and gram-stained. Isolates were sub-cultured on Nutrient agar (NA) for further identification and biochemical testing. Microbact™ 24E (Oxiod UK) and Staph ID were used to identify the organisms according to the manufacturer’s instructions.

Antimicrobial susceptibility testing (AST) for every organism isolated was done and interpreted using the modified Kirby–Bauer single disk diffusion technique with the following antibiotics: amoxicillin/clavulanate (20/10 µg), ceftriaxone (30 µg), cefoxitin (30 µg), ceftazidime (30 µg), chloramphenicol (30 µg), ciprofloxacin (5 µg), gentamicin (10 µg), and meropenem (10 µg) according to the Clinical and Laboratory Standards Institute (CLSI) guidelines [23].

Data analysis

Data were analysed using the Statistical Package for the Social Sciences (SPSS) version 22 IBM SPSS Inc, Chicago, IL, USA. Values were expressed as count/percentages and mean/standard deviation. Data was presented in frequency tables.

Results

Table 1 shows the general characteristics of the neonates with proven sepsis. Ninety-four (37.9%) of the 248 subjects recruited into the study had proven sepsis out of whom 68% had -LOS with a male-to-female ratio of 1:1 and 2:1 for EOS and LOS, respectively. Babies delivered outside the facility and admitted into the out-born unit accounted for 66.7% EOS and 96.7% LOS, respectively. The most common maternal risk factor for sepsis is prolonged (premature rupture of membranes) PROM of > 18 h (26.7%) followed by peripartum fever and dysuria which were all seen in EOS, while for LOS, there were no significant maternal risk factors as shown in Table 2.

Table 1 General characteristics of studied neonates
Full size table
Table 2 Maternal risk factors identified
Full size table

Table 3 the presenting symptoms; while respiratory difficulty followed by fever, convulsion, and poor suck were the most common symptoms in EOS, in LOS, it was fever followed by poor suck, yellowish discoloration of the body, and convulsion. The most common signs for EOS were tachypnoea, depressed primitive reflexes, dyspnoea, and pyrexia, while for LOS, it was pyrexia, jaundice, depressed reflexes, and abnormal tone. This is shown in Table 4.

Table 3 Presenting symptoms in neonates with proven sepsis
Full size table
Table 4 Presenting signs in neonates with proven sepsis
Full size table

Overall gram-negative bacteria were the most common group of isolates in both types of sepsis, and the pool is largely contributed to by the Enterobacteriaceae. While there were diverse isolates, S.aureus remained the most common isolate for both EOS and LOS. This was followed by Enterococcus spp, E. coli, and P. mirabilis for EOS, and E. agglomerans and K.pneumoniae for LOS as depicted in Table 5.

Table 5 Organisms isolated from blood cultures of studied neonates
Full size table

Most of the isolates in EOS were sensitive to ciprofloxacin followed by meropenem, while for LOS, it is ciprofloxacin followed by amoxicillin-clavulanate, gentamicin, chloramphenicol, and meropenem. This is shown in Tables 6 and 7, respectively.

Table 6 Antibiotic sensitivity pattern of EOS isolates
Full size table
Table 7 Antibiotic sensitivity pattern of LOS isolates
Full size table

Table 8 shows the outcome of admission of the neonates. The majority of neonates who had both types of sepsis were discharged from the hospital. Among these neonates, those with EOS had a longer average hospital stay of 8.9 days. The overall mortality rate was largely attributed to Staphylococcus aureus.

Table 8 Admission outcome of studied neonates
Full size table

Discussion

The prevalence of culture-proven sepsis from the study is 37.9%. This observation is similar to findings from earlier studies in the same centre by Onalo et al. [24] (35.5%) and Olorokooba et al. [25] (37.6%) which likely denotes poor public health interventions to reduce the prevalence of sepsis in society more so that most of the neonates came from within the metropolis. The observation is also similar to reports by Ekwochi [26] in Enugu (38.6%) and Mugalu [27] (37%) in Uganda but higher than what was found by Nwankwo [28] (27.8%), Ogundare [29] (16%), and Mhada [30] (26%). Late-onset sepsis was observed to be the most common type of sepsis (68%) similar to some reports [28, 31] as against other reports [32,33,34,35,36]. Most of the patients came through the out-born unit as was also reported by Nwankwo et al. [28] and this coupled with the preponderance of LOS implies the source of infections to be likely from the community. Though non-maternal factors associated with LOS were not evaluated in this study, factors such as poor personal hygiene/unhygienic practices, dirty environments, poor cord care, and exposure of neonates to well-wishers as is customary in our culture may have been contributory. Maternal risk factors for sepsis were mainly seen in EOS largely from prolonged PROM, and this is in keeping with the well-documented fact that the source of infection in EOS is the mother as was reported by some. [24, 33]. Several studies [24, 28, 31, 34, 36] have shown sepsis to be more common in males as we have observed, and it is believed that males are more prone to infections because of the presence of a single X-chromosome. The clinical features observed were non-specific for both EOS and LOS, but while EOS was more associated with features of pneumonia, LOS was more associated with features of meningitis; however, the presence of fever and jaundice should raise the index of suspicion of infection as they were the most observed symptoms and signs. Mhada et al. [30] reported a similar observation. Looking at the isolate groups, gram negatives were observed to be the commonest aetiology for both EOS and LOS as reported by some authors [28, 32] but in contrast to findings by others [24, 26, 31]. Coming down to individual isolates, our findings were quite interesting as the organisms were diverse; some are rare/opportunistic, and for some, this may be their first documentation as a cause of NS. We also observed infection with dual organisms (5.4%). The single most common isolate was Staphylococcus aureus for both EOS and LOS as was documented by some authors [24, 30, 37] but in contrast to findings by others [28, 31,32,33,34, 36] and in developed countries where GBS and CoNS predominates. This has buttressed the fact that pathogen burden varies between within countries, and variation is also seen from nursery to nursery [3]. Also, one organism or a group of organisms may over time replace another as the leading cause of NS in a particular region [18]. Most of the S. aureus isolates were methicillin resistant which signifies resistance to penicillin and cephalosporins likely from indiscriminate use of antibiotics. As the isolates vary from nursery-nursery so also will the antibiotic sensitivity. Ciprofloxacin from the study had the highest sensitivity across most of the isolates and should therefore be replaced as the antibiotic of first choice for both EOS and LOS, and more so that the risk of foetal arthropathy is no longer there. This observation was documented by Ekwochi et al. Mortality for both EOS and LOS was 16.7%, though high but it is lower than what was found in other studies [28, 31, 34, 36]. The mortality was majorly contributed by gram negatives likely because they are more virulent and stimulate a lot of inflammatory response but S. aureus and Klebsiella spp seem to be the most important culprits.

Conclusion

Neonatal sepsis still remains an important cause of morbidity and mortality. Clinical features are non-specific and are caused by diverse organisms; some of which are considered rare and opportunistic. As most of the cases were late-onset sepsis coming from the community, these infections can be preventable by deploying public health interventions: public enlightenment, improved personal hygiene especially hand hygiene, environmental sanitation, discouragement of harmful traditional practices, and rational use of antibiotics.