Bacteremia in children at the University

Hospital in Riyadh, Saudi Arabia

Fahad Abdullah Al-Zamil

Riyadh, Saudi Arabia

Author Affiliations: Department of Pediatrics, College of Medicine, King Khalid University Hospital, King Saud University, Riyadh, Kingdom of Saudi Arabia (Al-Zamil FA)

Corresponding Author: Fahad Abdullah Al Zamil, MBBS, ABP, Department of Paeditrics (39), College of Medicine, King Khalid University Hospital, P.O. Box 2925, Riyadh 11461, K.S.A. (Tel: 009661-4670807; Fax: 009661-4679463; Email: fahad_alzamil@hotmail.com)

Background: Bacteremia is a major pediatric health care problem despite the availability of new modalities in the management of this disease. The aim of the present study was to determine the incidence and pattern of bacteremia in pediatric group at a tertiary hospital in Riyadh, Saudi Arabia.

Methods: This retrospective study was conducted at the Department of Pediatrics, College of Medicine, King Khalid University Hospital, Riyadh in the period of January 2003 to January 2005. Positive culture was found in 259 patients aged below 15 years with a total of 8244 admissions in the period.

Results: The highest incidence of bacteremia was found in patients aged less than 1 year (57.9%), and the majority of patients (30.5%) were infants aged less than 1 month. Staphylococcus aureus was the most common isolated pathogen (18.7%). Prematurity was associated with 13.2% of the cases, and respiratory tract infection (10.1%) and fever (76.1%) were chief complaints.

Conclusions: Staphylococcus aureus is the most common isolated pathogen. The most common primary infections are respiratory tract infection and septic meningitis. Klebsiella pneumoniae and E. coli are the most common isolated Gram-negative organisms.

Key words: bacteremia; incidence;  Staphylococcus aureus           

World J Pediatr 2008;4(2):118-122

Introduction

Bloodstream infection has been a primary concern of physicians for over 80 years. Blood cultures are usually done for the evaluation of sick children with or without evidence of a focus of infection.^[1] Many serious infections are associated with bacteremia and the blood culture may be positive even when cultures of the specimens taken from the local area of infection (cerebrospinal fluid, tissue aspirate, synovial fluid) are negative. A report of a positive blood culture without apparent site of infection usually prompts a clinical re-evaluation and search for a primary focus.

Septicemia is a pathological condition with a mortality rate varying from 30% to 70% depending on virulence of the pathogen and host factors.^[2,3] Bloodstream infection is an important cause of death, giving a rate of 25%-50%.^[4] More recently Blomberg et al (2007)^[5] reported a mortality of 40% in pediatric patients with laboratory confirmed bacteremia. Bacterial isolation from blood specimen is often associated with high morbidity and mortality particularly among children.^[6] In recent years, bloodstream infections due to Gram-positive cocci have increased in frequency and antimicrobial resistance. Staphylococcus aureus bacteremia is a clinical problem with a particularly high incidence and mortality.^[7] The majority of bacteremia cases are caused by Staphylococcus spp., Streptococcus spp., Enterobacter spp., Escherichia coli, Klebsiella pneumoniae, and Pseudomonas.^[8]

Children who are younger than 36 months are at increased risk for bacteremia or sepsis secondary to the immaturity of their immune system. Furthermore, children in this age group may be febrile for 1 of 4 major reasons: fever of unknown reason, occult bacteremia, serious bacterial infections, and sepsis. Serious bacterial infection includes bacteremia, sepsis, infections of the soft tissues or joints, meningitis, bacterial enteritis, bacterial pneumonia, and urinary tract infections. Since the growing health care problems are related to bacteremia in children, we attempted to investigate the incidence and pattern of bacteremia in pediatric group at the University Hospital, Riyadh, Saudi Arabia. In addition, the study also aimed to provide information to the community and health officials about the main causes of bacteremia and its associated microorganism in pediatric patients.

Methods

This present retrospective study was conducted in the Department of Pediatrics, College of Medicine, King Khalid University Hospital, Riyadh during the period of January 2003 to January 2005. Included were 259 patients aged 1-180 months (less than 15 years) with positive blood culture.

All positive blood cultures were reported by the Bacteriology Laboratory of King Khalid University Hospital in the same period. The case records of all patients less than 15 years old were reviewed. The King Khalid University Hospital is a tertiary hospital that receives patients from the central region of the country. Clinical, microbiological data and other information such as temperature, immunodeficiency, central line and antibiotic therapy were obtained from the patient's medical record. A questionnaire concerning the demographic data, age, sex, clinical symptoms and signs was completed by the parents or guardians. Blood cultures were performed with an automated blood culture machine (Bact Alert, Organon Teknik). The organisms were identified by standard bacteriologic techniques.

Furthermore, antibiotic susceptibility testing was done by the Modified Kirby-Bauer Method. Antimicrobial test was done with ampicillin/amoxicillin, amoxicillin/clavulamic acid, aztreonum, ciprofloxacin, amicacin, imipenum, aztreonum, cefepime, cefixime, cefotaxime, cefoxitin, ceftazidime, ceftriaxone, cefuroxime, cephalexin, gentamicin, metropenem, piperacillin/tuzobactum and cotrimoxazole.

Data analysis

Univariate analysis was performed using Epi-Info version 6.0 (Centers for Disease Control and Prevention, Atlanta, USA). The means and proportions were compared by the Chi-square test and Student's t test. Statistical significance was considered at a value of P<0.05.

Results

During the study period, the medical records of the 259 patients with bacteremia were reviewed. The age of the patients ranged from 1 to 180 months (mean 27.3, median 7; SD 42.33). Of the 259 patients, 152 (58.7%) were male and 107 (41.3%) female. Bacteremia was documented in 150 patients (57.9%) of less than 1 year, of whom 79 (30.5%) were less than 1 month. Fifty (19.3%) of children were between 5 and 15 years old (Table 1). Infections and associated clinical conditions in these children are shown in Table 1 and Fig. 1. They included septicemia (16%), respiratory tract infection (10.1%), surgical repair (7.0%), osteomyelitis (5.4%), prematurity (13.2%), meningitis (8.2%), gastroenteritis (4.7%), cellulitis (3.5%), sickle cell disease (2.7%), and nephrotic syndrome (1.6%).

Gram-negative bacteria were predominant in 131 (50.6%) patients, while Gram-positive ones in 128 (49.4%) (Table 2, Fig. 2). The most common causative agents of bacteremia in these children were Staphylococcus aureus (48 patients, 18.7%), Streptococcus spp (42, 16.3%) (mainly group A beta-hemolytic streptococci), and Klebsiella pneumoniae (17, 6.6%). Escherichia coli and Haemophilus influenzae accounted for 16 (6.2%) patients respectively, Diphtheroids 17 (6.6%), Salmonella 11 (4.3%), Acinetobacter 10 (3.9%), and Brucella, Enterobacter and Pseudomonas aeroginosa 9 (3.5%) respectively. Methiciline resistance Staphylococcus aureus (MRSA) accounted for 8 (3.1%) patients, Bacillus spp 7 (2.7%), Yeast and Candida 2 (8%) respectively and Polymicrobial 14 (5.6%) (Table 2).

Chief complaints in most of the patients were fever, i.e., 197 (76.1%) patients who complained of fever and only 62 (23.7%) patients presented without fever. Symptoms recorded beside fever were dependent on the primary site of infection. They were rash (12, 4.7%), convulsions (32, 12.4%), vomiting (120, 46.3%), diarrhoea (46, 17.8%), cough (59, 22.8%), abdominal pain (38, 14.7%), chest pain (13, 5.1%), and bone pain (30, 11.6%).

Staphylococcus aureus was resistant to ampicillin/amoxicillin (95%), penicillin G (95%), cephalexin/cephradine (44%), and amoxicillin/clavulenic acid (24%). Streptococcus pneumonae resistant to the above drugs accounted for 35%, 38%, 31% and 16%, respectively. Gram-negative isolates were resistant to ampicillin/amoxicillin, including Klebsiella 100%, Acinetobacter 95% and E. coli 65%, respectively. The resistance rates of Klebsiella, Acinetobacter, and E.coli to amoxicillin clavulanic acid were 21%, 70% and 37%, respectively. Those of Klebsiella, Acinetobacter and E. coli to cotrimoxazole were 27%, 71% and 50%, respectively.

Our treatment protocol for bacteremia cases was the third generation of intravenous cephalosporin combined with ampicillin. However, the antibiotics were modified according to the blood culture.

Table 1. Characteristics of patients with bacteremia

Table 2. The different types of isolated micro-organisms

Fig. 1. Distribution of different types of primary cause of infection.

Fig. 2. Distribution of different types of micro-organism isolated.

Discussion

Bloodstream infection still carries high morbidity and mortality in hospitalized patients despite the availability of current sophisticated therapeutic modalities.^[5,9] Over the last decade, the occurrence of bloodstream infection has increased in hospitalized patients.^[9] The detection of causative bacteria is essential to the proper treatment.

In this study, bacteremia was confirmed in the 259 patients with various diseases. Primary infection was the common cause giving a rate of 84%. The most common infections identified included respiratory tract infection (10.1%) and septic meningitis (8.2%). The findings of our study were not in agreement with those reported by Nimri et al (2001)^[10] that common infections were gastroenteritis (40.4%) and pneumonia or bronchopneumonia.^[11]

The most common causative bacteria were Staphylococcus aureus (48 cases, 18.7%) isolated by surgical repair from osteomyelitis cases, Streptococcus spp (42, 16.3%), and Streptococcus pneumoniae (15, 5.8%) isolated from cases of pneumonia. Similar to our study, Streptococcus pneumoniae was reported previously as the most common pathogen in children with bacteremia.^[12] In our study, group B Streptococcus was found as a causative pathogen in 11 neonates (4.3%). Unlike our study, group A Streptococcus was found in few cases of bacteremia.^[13]

Staphylococcus epidermidis exists in the normal skin and mucosal flora and their presence in blood might indicate contamination of blood culture.^[14] In this study, we found 192 Staphylococcus epidermidis isolates, and in the same period, researchers from King Faisal Specialist Hospital, Riyadh found 124 cases of Staphylococcus epidermidis infection.^[15] They considered the majority of these isolates as possible skin contaminates. The number of positive blood cultures and sepsis symptoms encourage clinicians to decide antimicrobial therapy.

In this study, E. coli was isolated from 6.2% of the cases, the same number of cases of Haemophilus influenza (6.2%). Klebsiella pneumoniae was isolated from 6.6% of the cases. A study reported that E. coli, Pseudomonas aeroginosa and Klebsiella spp were the most common isolated Gram-negative organisms.^[16] Our findings in the present study were also consistent with those that E. coli were the most frequent Gram-negative bacterial species recovered from blood culture.^[17] The incidence of bacteremia caused by Klebsiella pneumoniae was 6.6% of the cases in this study; the rate was similar to that reported previously (7.4%).^[12]

We found Haemophilus influenzae in 16 cases (6.2%), including 15 cases (93.7%) under the age of 5 years. This is in agreement with the rate of 92% for cases of Haemophilus influenzae below 5 years.^[18]

Pseudomonas aeroginosa was isolated from 3.5% of cases by positive blood culture in this study. This concurs with Wendt et al^[16] who found that this organism was the commonest Gram-negative pathogen. Similarly, a study of children undergoing transplantation found Pseudomonas aeroginosa as a major pathogen causing blood infection.^[8]

Polymicrobial bacteremia was found in 13 cases (5.2%) in this study. The isolates included E. coli, MRSA, Klebsiella, Pseudomonas, Acinotobacter, Staphylococcus aureus, Staphylococcus epidermidis, Candida, and Streptococcus. Polymicrobial bacteremia was previously reported to be caused by E. coli, P. aeroginosa, K. pneumoniae, K. oxytica, S. marcesceus, E. cloacal, and A. caumannii.^[11]

In addition, occult bacteremia was detected in 13 patients (31%) and the mean age of children was 21 months.^[19] Similarly, 78.6% of the isolates were Gram-positive bacteria including the Staphylococcus epidermidis (55.4%), Staphylococcus aureus (9.5%) Streptococcus pneumoniae (4.5%) and Enterococcus faecalis (4%).^[20] Furthermore, Gram-negative bacteria in 44 cases (20%) included Escherichia coli and Klebsiella pneumoniae (K. pneumoniae) (3.6% respectively). Three isolates (1.3%) were Candida glabrata.

High rates of resistance to common antibiotics for mild and moderate infection are potentially a serious problem in hospitalized patients. Since particular concern is given to the number of non-susceptible isolates, the overall high rates of resistance to available antibiotics in this study may not reflect the actual rates in the community, because those patients with more susceptible organisms may be successfully treated at home or at a local health center. Multiple drug resistance of isolates from bacteremic children is also reported.^[21,22]

We conclude that the highest incidence of bacteremia may be present in patients below 1 year and most of them are infants under 1 month old. Considering the whole study population, we find Staphylococcus aureus is the most common isolated pathogen. The most common primary infections are respiratory tract infection and septic meningitis. Klebsiella pneumoniae and E. coli are the most common isolated Gram-negative organisms.

Acknowledgements

The author would like to thank Dr. Muslim Al Saadi (assistant Prof. & Consultant Pediatric Respirologist) for critical review of the manuscript and Mr. Nabeel Abdulqader for his collection of the data.

Funding: None.

Ethical approval:  Ethical Committee of the College of Medicine approved the study.

Competing interest: I declare that in the present study there is no conflict of interest with any institution or organization.

Contributors: This manuscript is a sole work of Dr. Fahad Al Zamil.

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Received May 21, 2007 Accepted after revision February 15, 2008