Introduction
Neonatal sepsis is a serious infectious disease with high mortality [1]. The definitive diagnostic test of neonatal sepsis is blood culture and includes early onset sepsis (appearance of clinical symptoms from birth to the third- seventh day), late onset sepsis (from the third day to the twenty eighth and hospital (from two days after hospitalization) with specific and sometimes common clinical symptoms [2]. According to the results of a study, the prevalence of early and late neonatal sepsis was 1.1 and 11.9 episodes per 1000 admissions, respectively [3]. 
The prevalence of septicemia in neonates in the developed countries is 1 in 1500 full-term neonates and 1 in every 250 pre-term babies [2]. Sepsis is one of the most important preventable causes of death in infants, so in a study in this center, it was the fourth cause of death in infants [4].
The proper diagnosis and treatment of neonatal sepsis is done depends on the understanding of its causative organisms. The present study aimed to investigate the types of microorganisms in definitive neonatal sepsis.

Methods
This cross-sectional study was performed on 266 neonates hospitalized with definitive sepsis in Ghaem Hospital in Mashhad from 2010 to 2020 using simple sampling method. Infants who had clinical signs of sepsis including lethargy, apnea, respiratory distress, restlessness, seizures, need for mechanical ventilation, abdominal distension, hypotension, and food intolerance; Blood culture was done on agar medium before starting antibiotics or changing them and incubated for 48 hours at 37 degrees. The diagnosis of the type of organism was given according to the agenda of the World Society of Microbiology. Usually, three to five days after the test, the microbial mass was reported. Sepsis was divided into two main groups based on the time of onset of clinical symptoms. A positive blood culture in the first 72 hours of birth along with clinical signs of infection was considered as early sepsis and after the first 72 hours of birth as late sepsis.

Results
In terms of the most common types of microbes were 66 cases (25%) Klebsiella pneumoniae, 46 cases (17.24%) Staphylococcus epidermidis, 34 cases (12.8%) Enterobacter, 25 cases (9.4%) E. coli, 21 cases (7.9%) coagulase negative Staphylococcus, 16 cases (6%) Enterobacter aeruginosa, 15 cases (5.6%) Staphylococcus saprophyticus, 9 cases (3.4%) Staphylococcus aerus, 9 cases (3.4%), Acinetobacter, 5 cases (1.9%) Enterococcus, 5 cases (1.9%) Enterococcus faecalis, 3 cases (1.1%) gram-negative bacilli, 3 cases (1.1%) Klebsiella rhinoceros chloromatis, 2 cases (0.75%) Pseudomonas, 2 cases (0.75%) Klebsiella oxytoca, 2 cases (0.75%) gamma hemolytic streptococcus, 1 case (0.37%) Pyosiantic, 1 case (0.37%) Candida and 1 case (0.37%) Citrobacter.
Eighty eight neonates had early sepsis and 197 neonates had late sepsis. The bacterial organism of early sepsis was 29.9% gram positive, 70.1% gram negative and in late sepsis was 22.9% gram positive, 77.1% gram negative. The most common causes of early sepsis were K. pneumonia 21 cases (23.9%), Staphylococcus epidermis 16 cases (18.2%) and 10 cases (11.4%) E. coli , and the most common causes of late sepsis, K. pneumonia 35 cases (25.4%), E. aeroginosa were 25(18.1%), S. epidermis 12(8.7%) and E. coli 11(8%) (Figure 1). 



Discussion
About 6% of infants examined in terms of infection had definitive sepsis. In different studies, the prevalence of sepsis has been reported from 7 to 24% [5, 16, 17]. The lower percentage of definitive sepsis prevalence in our study compared to similar studies can be due to the progress of special care for newborns by caregivers. According to the results of the study, more than two-thirds of the causes of sepsis in newborns are gram-negative, and these microorganisms are more common in premature babies and late-onset sepsis. K. pneumonia, S. epidermis and E. coli were three most common organisms in early sepsis [21] and K. pneumonia, S. epidermis and Enterobacter were the most common organisms in late neonatal sepsis [18]. Therefore, to treat neonatal sepsis, appropriate antibiotics should be used to cover these organisms and the choice of antibiotics for neonatal sepsis should be reconsidered.
Nosocomial infections are increasing as a big problem in our medical centers. So that these infections are considered an epidemic problem in developed and developing countries today. Increasing the duration of hospitalization, increasing the use of drugs, especially antibiotics, multiple requested tests and other diagnostic studies, and heavy costs on the one hand, and increasing the morbidity and mortality of these babies on the other hand, impose a great financial and social burden on the society. Considering that nearly 80% of our late sepsis was caused by gram-negative infections and gram-negative infections are seen due to lack of proper hand washing, overcrowding in the neonatal ward, inadequacy of the number of nurses to the number of infants and long-term hospitalization, therefore it is recommended in this context, appropriate treatment policies should be made in hospitals with NICU to control hand washing and the suitability of the nurse to the baby's bed.

Ethical Considerations

Compliance with ethical guidelines
This study was approved by the Ethics Committee of Mashhad University of Medical Sciences (Code: IR.MUMS.Medical.REC.1397.529) and the sample was prepared after obtaining consent from the parents.

Funding
The present research is related to the project approved by Mashhad University of Medical Sciences (Grand No.: 970388).

Authors' contributions
Conceptualization, study design, data acquisition, interpretation and analysis: All authors; Drafting of the manuscript and final approval: Hassan Boskabadi and Maryam Zakerihamidi; Statistical analysis: Hassan Boskabadi and Ali Taghipour; Supervision, administrative, technical support and financial resources: Hassan Boskabadi.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
We would like to express our thanks and appreciation to the honorable Research Vice-Chancellor and officials of Mashhad University of Medical Sciences and all the people who helped us.

 

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