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Research Article

Antimicrobial Susceptibility Profile of Neonatal Infection and Immune Response Pattern

Sarah A. Yousef and W. Soliman
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Background and Objective: Neonatal bacterial infections are considered the major causes of mortality and morbidity among neonates in developing countries. This study is aimed to study the bacterial pathogens causing neonatal infections, their antimicrobial susceptibility profile and the immune response of neonates against bacterial infection. Materials and Methods: About 150 samples were isolated from the neonatal intensive care unit. Bacteriological identification and susceptibility testing were done to collect samples by using the VITEK system. Collected serum samples were examined for determination of C-reactive Protein (CRP), Serum Amyloids A (SAA) and lysosomal activity. Results: The incidence of Gram-positive and Gram-negative organisms represented 36 and 64% respectively of culture isolates. Obtained results show many patterns of isolates and their antimicrobial susceptibility, Klebsiella showed a resistance rate to ampicillin of (88.9%). For Streptococcus all isolates were inhibited by levofloxacin. Results revealed a high level of C-reactive Protein (CRP), lysozyme and Serum Amyloids A (SAA) in the sepsis neonates group in comparison with other groups. Conclusions: Although bacterial infections in neonates are still manageable by the commonly used antibiotics, the development of some resistance to certain antibiotics is still a problem. Neonates bacterial infections caused elevation of some immunological parameters as SAA, CRP and Lysozyme.

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Sarah A. Yousef and W. Soliman, 2021. Antimicrobial Susceptibility Profile of Neonatal Infection and Immune Response Pattern. Current Research in Bacteriology, 14: 1-9.

DOI: 10.3923/crb.2021.1.9

Copyright: © 2021. This is an open access article distributed under the terms of the creative commons attribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.


Neonatal infections are acquired in utero transplacentally, intrapartum and postpartum1. Neonatal infections are more dangerous and more difficult to be detected than mothers and older children cause their new immune systems aren't adequately developed to fight the bacteria, viruses and parasites that cause these infections2. Neonatal infections are due to many bacteria such as Escherichia coli (E. coli), Streptococcus pyogenes, methicillin or vancomycin-resistant Staphylococcus aureus (S. aureus) (MRSA or VRSA respectively), Klebsiella pneumonia, Pseudomonas aeruginosa organisms (P. aeruginosa) and other infectious organisms3.

Group B Streptococcus and enteric bacilli originate from the digestive system of the mother are typically identified as the cause of early-onset infections in the neonate4. Listeria monocytogenes can also cause infection and is present in the mother5. Infections that develop one month after infant birth is more likely due to Gram-positive bacteria and coagulase-positive Staphylococci6. Acquired maternal infection of Ureaplasma urealyticum is accompanied by a strong immune response4,7.

Neonatal infections with E. coli and S. aureus were detected, but not as frequently as infections with Group B Streptococcus8. It is reported also that Gram-negative bacteria are the predominant causes of neonatal sepsis and among them, K. pneumonia is the most common pathogen, especially in developing countries9.

There is an increase in antibiotic resistance among neonates, so continuous surveillance for antibiotic susceptibility should be done to determine the resistance pattern of bacterial isolates10. Resistance to ampicillin and gentamicin was detected, also significant resistance to cotrimoxazole and gentamicin among bacterial isolates. Meanwhile, Klebsiella and E. coli show concern resistance to third-generation cephalosporins11.

Immunologic biomarkers as C-reactive Protein (CRP), lysozyme and Serum Amyloid A (SAA) have an important role in the diagnosis of early-onset neonatal sepsis and necrotising enterocolitis12,13.

Lysozyme is a bactericidal enzyme, its levels in premature neonates were found to be significantly lower than those of matures on the first day of life. Concentrations of serum lysozyme were decreased in neonates who suffer from septicemia caused by Gram-negative organisms. Neonates levels of cord blood lysozymes were significantly lower in neonates who suffer from a predisposition to septicemia. After the first few days of life, low levels of serum lysozyme in preterm and term newborns may contribute to neonates' inability to localise an infection and destroy bacteria. Neonates with severe infection, the levels of lysozyme in serum elevated14.

C-Reactive Protein (CRP) is used as an inflammatory marker and decision making tool for antibiotic therapy in neonates. CRP is the most widely used infection marker in neonates15. CRP levels rise with any source of inflammation and infection, also in neonates has been associated with prolonged labour, perinatal asphyxia, maternal pyrexia and meconium aspiration of the newborn16.

Serum Amyloid A (SAA) is an inflammatory protein which raised during the inflammatory response to bacterial infection. SAA is an acute-phase protein that is a precursor protein in inflammation-associated reactive amyloidosis and synthesized in the liver. SAA is a prognostic marker in late-onset sepsis in preterm infants17.

This research aimed to study bacterial pathogens which causing neonatal infections and their antimicrobial susceptibility profile. Also detection of neonates immunological response against bacterial infection.


Study area: The study was carried out at a Women's Childbirth Hospital and King Khaled Hospital in the Hail region, from November, 2018-January, 2020.

Ethical approval: This study was approved by the institutional board member of Maternity Hospital Hail, Saudi Arabia. Neonates` parents were informed about the purpose of the medicinal analysis, study subjects were not exposed to any risks.

Collection of clinical samples: One hundred clinical samples including blood, eye swabs, nasal swabs, ear swabs, Axilla, and umbilical cords were collected from NICUs at Maternity Hospital Hail and transferred immediately to the Laboratory of Microbiology and immunology in the same hospitals for their microbiological and immunological analysis. In addition, the necessary analysis prescribed by physicians such as haemoglobin level and Complete Blood Count (CBC) were examined.

A total of 50 serum samples of neonates were included, 5 were selected in the control group (normal neonates without any signs of infection), 30 neonates were diagnosed as sepsis with positive blood culture and 15 neonates were included in the clinical sepsis group (with clinical signs of sepsis but their blood culture was negative).

Bacterial Identification and Susceptibility Testing: Collected samples were streaked by either sterile loops or swabs (ear, eye and nasal swabs) axilla and umbilical cords were also streaked on blood agar, chocolate agar, Sabouraud dextrose agar, CLED agar18, Thioglycollate broth, Selenite F. broth, Salmonella Shigella agar and GM agar. After incubation at 37°C for 24-48 hrs, growing colonies were purified on another agar plate and slope cultures of pure isolates were made and kept throughout the experimental work4,5,9.

Identification and susceptibility testing were done using the VITEK system. Identification of microorganisms is accomplished by biochemical methods19.

Pure colonies were suspended in saline and were turbidometrically controlled. The suspension was inoculated into identification cards, which contain different biochemical broths in reaction cells and one negative control cell to increase viability19.

The VITEK programmed computer determines whether each well is positive or negative by measuring light attenuation with an optical scanner20. When the incubation period is completed, the reactions are analysed automatically and the identification is printed20. Antibacterial sensitivity tests were run similarly on cards that contain dilutions of antibiotics to detect the breakpoint Minimum Inhibitory Concentration (MIC) against bacterial isolates19. Separate cards for Gram-negative and Gram-positive organisms were provided. The MIC cut-off values differentiating sensitive, moderate and resistant status for an organism against appropriate antimicrobials are programmed into the system19.

Immunological parameters estimations

Lysozyme activity: Lysozyme activity was measure by using a turbidity assay in which 0.2 mg mL–1 lyophilized Micrococcus lysodeikticus in 0.04 M sodium phosphate buffer (pH 5.75) was used as substrate. 50 μL of serum was added to 2 mL of the bacterial suspension and the reduction in absorbance at 540 nm was determined after 0.5 and 4.5 min incubation at 22°C, only one unit of lysozyme activity was estimated as a reduction in absorbance of 0.001 min–1. Normal sera were tested at a dilution of 1 in 5 to obtain a linear rate of clearance of the suspension21.

Measurement of C-reactive protein: C-Reactive Protein (CRP) is considered the widest marker used for the detection of neonates bacterial infection, Using CRP to detect neonatal sepsis is hampered by its low initial sensitivity22. The level of C-reactive protein was determined by using an enzyme-linked immunosorbent assay kit supplied by MyBioSource, California, San Diego (USA). MBS039949 ELISA kit is based on C-reactive protein antibody and C-reactive protein antigen interactions to detect C-reactive protein antigen targets in serum samples.

Serum amyloid A (SAA): Serum amyloid A is an apo-lipoprotein synthesized by the liver23. Its levels rise early during bacterial inflammatory response up to 1000 times higher than the baseline of serum values but are significantly influenced by the patient’s hepatic function24.


The incidence of g-positive and g-negative organisms represented 36 and 64% respectively of culture isolates. Acinetobacter baumannii was estimated in 13% of blood samples while Klebsiella pneumonia was detected in 11% of samples, Meanwhile, Klebsiella pneumoniae was estimated in 6% among examined eye samples also S. aureus was detected in 5% of blood samples. Klebsiella oxytoca and Enterobacter cloacae were distributed in 2% of nasal samples, while Acinetobacter baumannii and S. aureus were detected in 4% of examined samples. The obtained data detect 2% of Enterobacter gergoviae distributed in samples isolated from Ears, while Staphylococcus haemolyticus was detected In one sample isolated from the axilla of examined neonates. Examined umbilical samples show the distribution of S. aureus in 5% of samples followed by Klebsiella pneumoniae 2%.

The antimicrobial profile of Klebsiella showed a resistance rate to ampicillin of (88.9%) and high resistance to the antibiotics used than other bacteria.

Because the antimicrobial susceptibility profile of Staphylococcus aureus causing neonatal infection show resistance to (fosfomycin and oxacillin). Fourteen oxacillin resistant Staphylococcus strains (82%) were identified, Table 1.

Acinetobacter isolates were resistant to most of the antibiotics tested, but (88.9%) of tested isolates were sensitive to colistin as represented in Table 2. Acinetobacter baumannii shows high resistance to used antibiotics while all E. coli species were resistant to amoxicillin and ampicillin, as estimated in Table 2. Meanwhile, All the Pseudomonas aeruginosa strains screened showed 100% resistance to ampicillin. Enterobacteriaceae species shows no resistant isolates to meropenem, piperacillin (combination antibiotic), and amikacin (Table 2).

Table 1: Antimicrobial susceptibility profile of Staphylococcus species causing neonatal infections
Antibiotics tested MIC's and interpretation
Isolates Oxa Gen Tob Lvx Mxf Ery Lzd Tec Van Tet Tgc Fos Nit Fus Mup Rif
S. aureus > = 4 R < = 0.5 S < = 1 S 0.25 S < = 0.25 S > = 8 R 2 S < = 0.5 S 16 S < = 1 S < = 0.12 S 16 S 32 S N/A N/A < = 1 S
S. aureus (MRSA) > = 4 R N/A < = 1 S N/A < = 0.25 S N/A 2 S < = 0.5 S 1S N/A < = 0.5 S 1 S < = 16S < = 0.5 N/A N/A
S. epidermidis > = 4 R < = 0.5 S 2 S < = 0.12 S 1 S > = 8 R N/A > = 32 R > = 32R > = 16S - 16 S 256 R > = 3 R N/A > = 32 R
S. hominis N/A N/A N/A N/A < = .3 S N/A 2 S 1 S N/A N/A < = 0.12 S 13 R < = 2 S > = 3 R N/A N/A
S. warneri > = 4 R > = 2 R > = 2 R > = 8 R 2 R > = 8 R 1 S > = 3 2 < = 1 < = 0.12 S < = 8 S < = 2 < = 3 N/A N/A
S. pseudintermedius > = 4 R < = 0.5 S < = 1 S 1 S < = 0.25 S > = 8 R 2 S 1 S 1 S > = 16 R < = 0.12 S 128 R < = 16 S N/A N/A < = 1 S
S. haemolyticus > = 4 R N/A N/A 0.25 S < = 0.3 S N/A N/A 4 S 1 S N/A 0.25 S 13 R < = 16 S N/A N/A N/A
Oxa: Oxacillin, Ery: Erythromycin, Van: Vancomycin, Fos: Fosfomycin, Mup: Mupirocin, Gen: Gentamycin, Mxf: Moxifloxacin, Lzd: Linezolid, Tet: Tetracyclinee, Tec: Teicoplanin, Tgc: Tigecycline, Rif: Rifampicin, Tob: Tobramycin, Lvx: Levofloxacin, Fus: Fusidic acid, S: Sensitive, R: Resistant, N/A: Not applicable

Table 2: Antimicrobial susceptibility profile Types of Acinetobacter sp., E. coli, Pseudomnas aeruginosa and Enterobacter sp.
Antibiotics tested MIC's and interpretation
Isolates Amp Amc Tzp Nfx Ctx Cfz Fos Tgc Cfpm Ipm Mem Ami Etp Gen Cip Col Nit Tmp lynx Tob Min
A. baumanni > = 32 R > = 32 R > = 13 R > = 16 R N/A > = 64 R > = 2 R N/A > = 64 > = 16 > = 16 R N/A N/A > = 16 R > = 4 R < 0.5 S >5 R >2 R N/A N/A N/A
A. lwoffi < = 2 > = 32 > = 13 R N/A > = 64R < = 1 S N/A N/A > = 64 R < = 0.25 S > = 16 R 16 S N/A > = 16 R > = 4 R N/A >5 R >3 R N/A N/A N/A
E. coli 8 S 4 S < = 4 S N/A > = 6 R < = 1 S < = 2 S N/A < = 1 S < = 0.5 S < = 0.3 S < = 2 S <5 S < = 1 S < = 0.3 S N/A 32 S <2 S N/A N/A N/A
P. aeruginosa N/A N/A N/A N/A < = 1 S < = 1 S N/A >8 R < = 1 S 2 S 0.5 S < = 2 S N/A < = 1 S < = 0.3 S N/A N/A >3 R 0.25 S <1 S >2 R
Enterobacter N/A N/A < = 4 S < = 0.5 S < = 1 S < = 1 S 64 R N/A < = 1 S 2 S < = 0.3 S < = 2 S N/A < = 1 S < = 0.3 S N/A N/A <2 S N/A N/A N/A
Enterobacter N/A N/A < = 4 S N/A N/A N/A N/A N/A N/A < = 0.3 S < = 0.3 S < = 2 S N/A < = 1 S < = 0.3 S N/A N/A < = 2 S N/A N/A N/A
Enterobacter N/A N/A 8 S N/A N/A 16 R N/A N/A 2 S < = 0.3 S 0.5 S < = 2 S N/A > = 2 R > = 4 R N/A N/A >3 R N/A N/A N/A
Amp: Ampicillin, Amc: Amoxicllin, Tzp: Pipracillin/piperacillin, Nfx: Norfloxacin, Ctx: Cefotaxime, Cfz: Ceftazidin, Cfpm: Cefoperazone, Ipm: Imipenem, Mem: Meropenem, Ami: Amikacin, Cib: Ciprofloxacin, Col: Colistin, Nit: Nitroxolin, Tmp: Trimethoprim, Min: Minocycline

Table 3: Antimicrobial susceptibility profile of Klebsiella sp., Strept. aglactia and Enterococcus gallinarum
Antibiotics tested MIC's and interpretation
Isolates Amp Amc Tzp Tec Cet Fox Caz Van Cro Cfpm Ipm Mem Amk Gen Mox Cip Tgc Nit Tmp Lyx Tet Clin
K. pneumoniae > = 3 R 2 R >1 R N/A > = 6 R 8 R > = 6 R N/A > = 6 R > = 6 R - > = 2 R - > = 2 R N/A 0.5 S 2 S 32 S > = 20 S N/A N/A N/A
K. oxytoca > = 3 R 8 S <4 S N/A >6 R 32 R N/A N/A 16 - <0.3 S <2 S <2 S <1 S N/A <2 S 5 S 1 R < = 20 S N/A N/A N/A
S. agalactiae N/A N/A N/A <5 S N/A N/A N/A <5 S N/A N/A N/A N/A N/A N/A N/A N/A <1 S <2 S < = 1 S 1 S >2 R > = 8 R
E.gallinarum N/A N/A N/A <5 S N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A 2 R N/A <1 S 3 S N/A N/A N/A N/A
Clin: Clindamycin, Amk: Amikacin, Caz: Ceftazidime, Cro: Ceftriaxone

Table 4: Antimicrobial susceptibility profile of Serratia marcescens, Cronobacter sakazaki, Raoultella ornithinolytica, Moraxella lacunato and Aeromonas salmonicida
Antibiotics tested MIC's and interpretation
Isolates Rif Caz Tet tec Cfpm Aza Ami Gen Fox Imp Mox Tob Fos Cip Min Lvx Nit Mem Tgc Col Tmp Amo Etp Amp Tzp Cet Ami
S. marcescens N/A 32 R N/A N/A 32 R 32 R 4 S 8 R N/A N/A N/A 2 S N/A 2 R N/A > = 8 R N/A N/A 2 S > = 2 R > = 3 R N/A N/A N/A N/A N/A N/A
C. sakazaki N/A < = 1 S N/A N/A < = 1 S N/A < = 2 S < = 1 S < = 4 R < = 3 S N/A N/A N/A < = 3 S N/A N/A 32 S < = 2 S 1 S N/A < = 2 S < = 2 S N/A N/A < = 4 S > = 6 R N/A
R. ornithinolytica N/A 16 R N/A N/A < = 1 S > = 6 R < = 2 S < = 1 S - < = 3 S N/A < = 1 S N/A 0.5 S 4 S N/A N/A < = 3 S 1 S 5 S N/A N/A < = 5 S 8 S 8 S N/A N/A
M. lacunato 8 R 8 R > = 3 R N/A N/A N/A N/A N/A N/A < = 3 S < = 1 S > = 1 S N/A N/A N/A 25 R N/A 0.3 S N/A 20 S N/A N/A N/A N/A N/A N/A N/A
A. salmonicida N/A 16 R N/A N/A N/A N/A N/A < = 1 S 1 S < = 4 S N/A N/A N/A > = 4 R N/A N/A N/A N/A N/A N/A > = 3 R > = 32 R N/A > = 32 R < = 4 < = 2 N/A
Aza: Azacitidine, Etb: Etophyllin, Col: Citicoline, Tec: Teicoplanin

Table 5: Immunological parameters of neonates of serum sample
Sepsis (positive blood culture)
Clinical sepsis (negative blood culture)
Serum amyloid A (SAA) μg mL–1
Lysozyme activity
Serum CRP (mg dL–1)
SAA: Serum amyloid A, CRP: C-reactive protein

Streptococcus agalactiae show high resistance to clindamycin and all isolates were inhibited by levofloxacin Table 3, while the only one isolate of Enterococcus in this study show sensitivity to all of the antibiotics tested except moxifloxacin (Table 3).

Aeromonas growth was prevented by most of the antibacterial agents, meanwhile few isolates show multidrug resistance patterns. Aeromonas salmonicida show resistance to Ampicillin (Table 4), while Moraxella lacunata was sensitive to moxifloxacin, tobramycin, trimethoprim and tigecycline as illustrated in Table 4.

Raoultella different classes of antimicrobials showed significant effects such as β-Lactam penicillins, for Raoultella ornithine show resistance to ceftazidime, azithromycin and levofloxacin (Table 4). While Serratia isolates were found to be sensitive to amikacin, tobramycin, and tigecycline, Serratia marcescens show sensitivity to tobramycin and amikacin (Table 4). Cronobacter sakazakii isolate in this study is found to be sensitive for many types of antibiotics and resistant to cephalothin as shown in Table 4.

Almost all of these bacterial strains were multidrug-resistant and have variability in their sensitivity or resistant profiles, no strain was either completely resistant or sensitive to a certain antibiotic. Such types of studies with good infection control practice and the use of sensible antibiotics will guarantee the success of infection management and maintain the potency of available antibiotics.

The mean of CRP in the control group was 0.365±0.78 mg dL–1 and the sepsis group showed a higher value of CRP than clinical sepsis and control groups with a mean of 8.384±1.36 mg dL–1. CRP results revealed a significant increase in the sepsis group in comparison with control and clinical sepsis as shown in (Table 5). Obtained results revealed a high concentration of lysozyme in the sepsis group in comparison with the control group. The mean plasma lysozyme concentration in healthy neonates was 0.83±0.78 μg mL–1 while in sepsis neonates (positive blood culture) was 1.56±0.89 μg mL–1 (Table 5).

SAA concentration in serum reported high concentration in the sepsis group in comparison with other groups. The mean of SAA in the control group was 8.85±0.23 μg mL–1, while the sepsis group showed a higher value of SAA with a mean of 23.56±0.69 μg mL–1 (Table 5).


Antimicrobial susceptibility testing show variable levels of resistance to tested antibiotics. Klebsiella species isolates have high rates of resistance to the used antimicrobial agents20. Most K. pneumoniae isolates are resistant to amoxicillin and ampicillin, due to a constitutively expressed chromosomal class-A β-lactamase20. Our study showed a resistance rate to ampicillin of (88.9%). However, Klebsiella isolates were reported to be sensitive to fluoroquinolones. Ciprofloxacin, an orally well-absorbed quinolone, is commonly used for empirical UTI treatment20. Our study showed a sensitivity rate to Ciprofloxacin of (95%). Because of fail treatment with routine drugs fluoroquinolones have been used as an alternative medication.

Methicillin-resistant S. aureus (MRSA) is a major nosocomial pathogen causing serious morbidity and mortality in immunosuppressed patients25. Using broad-spectrum antibiotics in treatment protocol also increases the risk of acquiring resistant bacteria and MRSA. In our study one case of MRSA was reported, treatment antibiotic-resistant bacteria is a therapeutic problem. Most of the Staphylococcal strains are reported to be resistant to oxacillin. Because of inactivation of antibiotic as a result of structural modification by enzymatic action, prevention of access to a target by altering outer membrane permeability, alteration of an antibiotic target site, efflux pump which pumps out antibiotic and target enzyme bypass26. This study identified fourteen oxacillin resistant Staphylococcus strains (82%), on the other hand, a kind of S. aureus known as hetero-VRSA, frequently produces VRSA when exposed to vancomycin and is linked to infections. The presence of hetero-VRSA is thought to be a good predictor of vancomycin's therapeutic success in hospitals. Vancomycin resistance is acquired when the cell wall thickens as a result of the accumulation of significant amounts of peptidoglycan. For all isolated VRSA strains, this appears to be a common resistance mechanism27.

In this study 3 cases (15%) of VRSA were identified, a recent report of Staphylococcus resistance to commonly used antibiotics highlights the importance of the development of new agents such as tigecycline for adequate treatment of highly resistant strains. This research also evaluates tigecycline activity against clinically isolated Staphylococcus species.

Similar to the results of other studies28, tigecycline was effective against all of Staphylococcus species, there was no resistance to tigecycline among Staphylococcal isolates in biologic samples obtained in this study.

A. baumannii causes hospital-acquired epidemics as a result of treatment failures caused by multiple antibiotic resistances29. Colistin remains one of the last-resort antibiotics for the treatment of multidrug-resistant Acinetobacter30. In this study, Acinetobacter isolates were resistant to most of the antibiotics tested, but (88.9%) of tested isolates were sensitive to colistin.

In this study isolated E. coli were resistant to ampicillin and amoxicillin, indicating a cautious use of these antibiotics for the treatment of E. coli infections. E. coli resistance to penicillins is increasing by the day, however, there are only a few studies that show 100% resistance to penicillins31.

Antibiotics active against E. coli were amikacin, Imipenem, meropenem generally with no resistant isolates. This is also reported in other studies31. It is recommended to treat the UTIs caused by E. coli by combination therapy especially amikacin and ciprofloxacin to provide better results32.

Because of the synergy between a multi-drug efflux system or a type 1 AmpC-lactamase and limited outer membrane permeability, P. aeruginosa is naturally resistant to numerous antimicrobial agents33. Almost all of the six P. aeruginosa strains tested were ampicillin-resistant 100% of the time. For many Gram-positive and Gram-negative bacteria, carbapenems (such as Meropenem and Imipenem) are the medications of choice.

The most efficacious antibiotics that we found in our study were Carbapenems. In this study, there was no resistance to Impineme and Meropenem. Similar results have been published in various other studies too indicating that Carbapenems are the drugs of choice in case of infections, especially multidrug-resistant P. aeruginosa with minimum detected resistance34. Obtained results show no resistance for ciprofloxacin and levofloxacin, while this activity was reported in other studies35. Although both ciprofloxacin and levofloxacin are active against P. aeruginosa, levofloxacin use might be associated with a higher risk of isolation of quinolone-resistant P. aeruginosa than ciprofloxacin35.

Enterobacteriaceae show resistance to monotherapy of cephalosporins and penicillins. A combination of ampicillin, amoxicillin and third-generation cephalosporins with sulbactam and monotherapy of amikacin showed higher sensitivity to Enterobacteriaceae infections but maximum sensitivity was shown by carbapenems36. The obtained results revealed, no resistant isolates to meropenem, piperacillin (a combination antibiotic) and amikacin.

Levofloxacin inhibited all Streptococcus isolates, and time-kill data from additional investigations showed that levofloxacin is bactericidal against most Streptococci and had increased action when coupled with gentamicin. Levofloxacin, alone or in combination with an aminoglycoside, could be a good alternative to more traditional treatments for common or serious streptococcal infections37.

On the other hand, most Streptococci show similar susceptibility patterns to the majority of antibiotics. They remain uniformly sensitive to vancomycin, teicoplanin, trimethoprim, chloramphenicol and rifampicin. In this study, all of the isolates were trimethoprim sensitive38. The only isolate of enterococcus in this study show sensitivity to all of the antibiotics tested except moxifloxacin. This has been described in other studies as Fluoroquinolone resistant species39.

Antimicrobial resistance of Aeromonas species is commonly chromosomally mediated, however, β-lactamases produced via way of means of aeromonads might also additionally on occasion be encoded via way of means of plasmids or integrons40.

Aeromonas isolate was inhibited by most antimicrobial agents, with few isolates showing a multidrug resistance profile. It shows resistance to ampicillin, amoxicillin and ceftazidime as reported by Murray et al.41. Most of Moraxella species except Moraxella catarrhalis, are susceptible to penicillin, cephalosporins, tetracyclines, quinolones, and aminoglycosides42. In our study, Moraxella isolates were sensitive to trimethoprim, moxifloxacin, tobramycin, and tigecycline.

Raoultella ornithinolytica causes enteric fever, a different class of antimicrobials showed significant effects such as β-Lactam penicillins (amoxicillin/clavulanic acid, ampicillin/sulbactam and piperacillin), cephalosporins (cefazolin, ceftriaxone and cefuroxime), monobactam (aztreonam), fluoroquinolones (ciprofloxacin and levofloxacin), aminoglycosides (amikacin and tobramycin) and tetracycline43. This sensitivity pattern appears also in our results. Serratia isolate was found to be sensitive to amikacin, tobramycin and tigecycline. Amikacin is useful in treating patients infected with gentamicin-resistant S. marcescens organisms. The capacity of S. marcescens strains to develop resistance to amikacin limits the usefulness of this antibiotic in the treatment of deep tissue infections44. Cronobacter sakazakii isolate in this study is found to be sensitive for many types of antibiotics that are also reported in other studies, such infections are treated with ampicillin and gentamicin45. Enterobacter species are resistant to narrow-spectrum penicillins which have good activity against E. coli. Increasing resistance of Cronobacter to antibiotics should prompt researchers to consider carbapenems in concert with an aminoglycoside. Minimizing the use of broad-spectrum antibiotics and selecting antibiotics on basis of sensitivity results are of paramount importance45.

CRP is one of every of the foremost used laboratory tests for neonatal bacterial infection and despite the continuing emergence of the latest infection markers15. CRP incorporates a role within the diagnosis of early-onset neonate sepsis and there's an association between CRP levels and sepsis46. An association between high CRP levels and neonatal sepsis has been detected, despite CRP may be a non-specific marker in inflammatory reactions, the relatively high specificity and sensitivity above 4.09 ng mL–1 level of CRP strengthen the use of CRP within the diagnosis of neonatal sepsis47.

Lysozyme is considered an indicator of innate immune response and phagocytic activity. This is based on, phagocytosis is stimulated by the presence of an antigen, the amount of serum lysozyme is increased21.

SAA show a significant increase in the sepsis group in comparison with another group, this was contradictory to the study done by who reported that sepsis produced an elevation of SAA levels than what occurred with the control normal group. There is a high probability of neonates with normal SAA levels when there is no neonatal sepsis, neonate with symptoms of sepsis will have blood culture-positive neonatal sepsis if SAA levels is >10 μg mL–1 48.

The findings of these studies suggest that CRP, Lysozyme and SAA, are visiting be helpful as diagnostic and prognostic markers of neonatal sepsis in routine clinical settings. However, it's recommended to check the diagnostic efficiency of CRP during a combination with other chemical markers to extend the specificity of the test.

Overall, neonatal septicemia is also a life-threatening emergency and its rapid treatment with antibiotics is very important. The knowledge of the etiological organisms of neonatal sepsis and their antibiotic susceptibility profile is critical for effective therapeutic intervention. Thus, minimizing the use of broad-spectrum antibiotics and selecting antibiotics on basis of sensitivity results are of paramount importance. This study has enrolled neonates which were only admitted to Women's Childbirth Hospital and King Khaled Hospital in the Hail region Future research should cover suspected neonates from different regions.


We conclude that a Higher proportion of the neonates with sepsis showed raised CRP, SAA and lysozyme levels than those without sepsis and the level correlated well to the severity of the condition. The findings of this study suggest that CRP, SAA and lysozyme can be used as diagnostic and prognostic biomarkers of neonatal sepsis.


This study discovers that CRP, SAA and lysozyme as biomarkers of neonatal sepsis. Also, it will help the researcher for antibiotics treatment protocols of neonates, through the determination of antimicrobial sensitivity patterns and immune responses developed.


The authors are indebted to Hail maternity hospital for allowing us to carry out this work in the Laboratory of Microbiology and serology.


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