Bacterial Agents of Meningitis in Children and Detection of Their Antibiotic Resistance Patterns in Hamadan, Western Iran
Rasoul Yousefi Mashouf,
Seyyed Hamid Hashemi
Bacterial agents of meningitis in children and detection of their antibiotic resistance patterns in Hamadan, Western Iran. Bacterial meningitis is still one of the most dangerous infection diseases and causes serious complications in children. The aim of present study was to identify the most common of bacteria causing meningitis in children under 10 years of age and detection of their resistance to routine antibiotics in Hamadan. Overall 582 children suspected to meningitis were investigated for CSF cultures, elevation of CSF leukocyte count and clinical manifestations, from January 1998 to December 2002 in two hospitals. The required data of patients were gathered through a questionnaire and analyzed using Epi6 system. The species were identified by biochemical and latex-agglutination tests. Antibiogram tests were also performed by gel-diffusion method of Kirby-Bauer. Out of 582 children suspected to meningitis, 146 children (25.1%) had positive bacterial culture that %58.9 of isolates was Gram-positive cocci and %41.1 was also Gram-negative bacteria. The most common isolates were Streptococcus pneumonia (23.9%), Staphylococcus aureus (13.1%), Escherichia coli (10.9%), Neisseria meningitides (6.2%) and Haemophilus influenzae type b (4.1%). The most effective antibiotics against isolates were ceftizoxime, kanamycin and gentamicin while most of isolates showed high resistance to ampicillin, amoxicillin, sulfamthoxazole-trimethoprim and chloramphenicol. The present study showed that Gram-positive bacteria in particular, S. pneumoniae and S. aureus are predominant causes of bacterial meningitis in children involved in this region. Most species showed high resistance to routine antibiotics such as amoxicillin, ampicillin and chloramphenicol. The antimicrobial susceptibility pattern for bacteria causes meningitis may provide a guideline for the selection of appropriate drug treatment.
Bacterial meningitis is one of the most potentially serious infections in infants and older children because it is associated with a high rate of acute complications (Feigin and Pearlman, 2004; Prober, 2004). Meningitis is considered as an endemic disease in our country. Bacterial meningitis usually is the first causes of meningitis in infants and children in this region (Borjian, 1999).
The incidence of bacterial meningitis in children aged <5 years and 5<or = <10 years in Hokkaido, Japan between 1999 and 2003 was 6.3 and 0.7 cases per 100,000 children/year (Sakata, 2005). Bacterial meningitis affected almost 6000 people every year in the United States and about half of all cases occurred in children 18 years old or younger (Schuchat et al., 1995). The incidence of pneumococcal meningitis in North Yorkshire, England, between 1997 and 2002, accounted for an incidence of 1.1 per 100,000 per year that mortality was 28% (Weightman and Sajith, 2005).
Etiologic agents of bacterial meningitis are variable and usually depend to
time, geographical location and age of patients. There are three main organisms
that account for over 90% of the world's cases of meningitis (Davey et al.,
1982; Bedford et al., 2001). These are Haemophilus (H.)
influenzae type b, Neisseria (N.) meningitidis and
Streptococcus (S.) pneumoniae. However, other bacteria
such as Staphylococcus (S.) aureus, Streptococcus (S.)
agalactiae, Escherichia (E.) coli, Pseudomonas (P.)
aeruginosa and Klebsiella (K.) pneumonia could be rarely
caused of meningitis (Al-Mazrou et al., 2004; Foster and Rhoney, 2005).
In a study from Egypt, the causes of bacterial meningitis in 310 children were
H. influenzae 21%, S. pneumoniae 13.9% and N. meningitidis
14.2% (Farag et al., 2005). In other study from the United State revealed
the most common isolated bacteria from newborns was H. influenzae type
b, S. pneumoniae and N. meningitides, respectively (Wenger
et al., 1990). Before the 1990, H. influenzae type b was the leading
cause of bacterial meningitis, but new vaccines being given to children as part
of their routine immunizations have reduced the occurrence of serious H.
influenzae type b disease (Gessner, 2002; Prober, 2004). Today, N. meningitidis
and S. pneumoniae are the leading causes of bacterial meningitis (King
and Richmond, 2004; Faye et al., 2005).
Because of the major increasing of antibiotic resistance in bacteria causing bacterial meningitis in the last few years, attempts have been made to organize an appropriate antibiotic treatment regime with combination of synergistic antibiotics (Erdem and Pahsa, 2005; Saha et al., 2005; Prober, 2004). Therefore, the purpose of this study was to describe the frequency of etiologic agents of bacterial meningitis among children under 10 years of age in a sample of patients in the west of Iran, with emphasis on the frequency of bacterial meningitis of unusual etiology and detection of drug resistance of isolated bacteria from patients with bacterial meningitis.
MATERIALS AND METHODS
A cross-sectional and prospective descriptive study was conducted on children under 10 years of age who were suspected to bacterial meningitis and admitted in the pediatric department of two hospitals (Sina and Ekbatan) in Hamedan, the west of Iran between January 1998 and December 2002. Active surveillance for cases of bacterial meningitis among the study population, which comprised 582 children, was implemented. The required data of the patients including clinical manifestations, patient demographics (age, sex and season) and types of microorganisms isolated from Cerebrospinal Fluid (CSF), were recorded in a special questionnaire and then analyzed using EP1 INFO 6 software package.
After the establishing of indication, lumbar punction was performed. CSF was sent to cytological, biochemical and bacteriological analyses. Diagnosis of meningitis was established when at least three criteria of four were fulfilled: (1) isolation of bacterial pathogens by CSF culture and identification of bacteria; (2) elevation of CSF leukocyte count more than 20 with predominance of polymorphonuclear leukocytes; (3) hypoglucorrhachia (glycaemia less than 40% mg or less than 50% of glycaemia); (4) clinical manifestations including fever, consciousness, neck stiffness and sign of mental irritation. The sampling of CSF of each patient was done to culture at two times to make sure of growing any pathogenic microorganisms. The etiologic diagnosis was based on either stained-smears (Gram) of CSF sediment, culture and latex-agglutination test.
Cultivation and isolation of organisms were performed according to the methods outlined in the Bailey and Scotts Diagnostic Microbiology (Forbes et al., 2002). The sediment of spinal fluid was prepared for providing the smear and cultures. Specimens were then cultured on appropriated culture media including Thayer-Martine agar, Eeosin Methylen Blue (EMB) agar and Blood agar (Merck, Germany). The cultures were incubated in 37°C for 24-48 h and then the colonies were removed for further studying. Biochemical and antigenic properties of isolates were verified for identification purposes. In essential cases, specific antiserum against bacteria was used for precise identification of bacteria type (Koneman et al., 1997).
In order to detection of the susceptibility of isolates to routine antimicrobial drugs, the all isolates were tested by disc diffusion (Kirby-Bauer) method (Bauer et al., 1986). Eight antibiotics including amoxicillin (AMX), ampicillin (AM), chloramphenicol (CH), cephalexin (CF), ceftizoxime (CT), gentamicin (GM), kanamycin (KA) and sulfamthoxazole trimethoprim (SXT) were applied. Results were then collected and analyzed.
Out of 582 children less than 10 years suspected to meningitis, only 146 children (25.1%) had positive bacterial culture that 58.9% of isolates was Gram-positive cocci and 41.1% was also Gram-negative bacteria. The most common isolates of Gram-positive cocci were as follow: S. pneumonia (23.9%), S. aureus (13.1%), S. agalactiae and Staphylococcus (S.) epidermidis each 13 cases (8.9%). The most common isolates of Gram-negative bacteria were: E. coli (10.9%), N. meningitidis and P. aeruginosa each 9 cases (6.2%) and H. influenzae type b (4.1%). Frequencies of the all isolated bacteria from patients with bacterial meningitis are shown in Table 1.
Fever (88.3%), Leukocytosis (74.6%), nausea and vomiting (67.1%), sleepness (66.4%) and headache (46.6%) were most common clinical manifestations of meningitis in children under 10 years of age with bacterial meningitis. Frequencies of clinical manifestations of patients are shown in Table 2.
Of 146 patients with bacterial meningitis, 79 cases (54.2%) were males and
67 cases (45.8%) were females. The frequencies of age groups of patients with
bacterial meningitis are shown in Table 3, the most frequent
patients were belonged to the 0-2 years old (28.3%) and the least frequent patients
were belonged to the 8-10 years old (13.1%).
||Frequencies of microorganisms isolated from patients with
||The frequencies of clinical manifestations of the patients
with bacterial meningitis
||The frequencies of the age groups of patients with bacterial
||Antibiotics resistance patterns of isolated bacteria from
patients with bacterial meningitis
|*: SXT = Sulfamthoxazole-trimethoprim, KA = Kanamycin, GM
= Gentamicin, CT = Ceftizoxime, CF = Cephalexin, CH = Chloramphenicol, AM
=Ampicillin, AMX = Amoxicillin
Present results showed that the most frequent bacterial meningitis (43.7%)
was occurred during fall and then winter with frequency of 27.6% and summer
14.8%. The lowest frequency (13.9%) was belonged to winter.
As it is observed (Table 4), the most effective antibiotics against both Gram-negative bacteria and gram-positive cocci were ceftizoxime, kanamycin and gentamicin while most of isolates showed high resistance against ampicillin, sulfamthoxazole-trimethoprim, chloramphenicol and amoxicillin. P. aeruginosa, S. aureus, S. epidermidis and K. pneumonia showed the highest resistance to many of antibiotics applied in this study. P. aeruginosa showed hundred percent resistances to four antibiotics including ampicillin, sulfamthoxazole-trimethoprim, cephalexin and amoxicillin. S. aureus, S. epidermidis and K. pneumoniae were also resistant (100%) to ampicillin. However, S. pneumonia, S. agalactiae, N. meningitidis and H. influenzae type b, showed low or moderate resistance to antibiotics used in this study. S. pneumonia, N. meningitidis and H. influenzae type b showed no resistance (0%) to ceftizoxime and gentamicin, they were sensitive to antibiotics of aminoglycosides groups including kanamycin and gentamicin and group of cephalosporines including cephalexin and ceftizoxime.
Knowing whether a virus causes meningitis or bacterium is important because the severity of illness and the treatment differ. Most researchers have demonstrated that H. influenzae type b; S. pneumonia and N. meningitidis are as main agents of bacterial meningitis especially in children (Ignjatovic, 2001; Bedford et al., 2001). In this study, S. pneumoniae, S. aureus and E. coli have been the most important causes of bacterial meningitis in involved children (Table 1). Nonetheless a considerable percentage was attributed to other unusual bacteria, which may be K. pneumoniae, P. aeruginosa and Citrobacter (C.) freundii and others as shown by Gebremariam in Addis Ababa (Gebremariam, 1998). However, in India, a low incidence of infection with N. meningitidis has been reported (Grimwood et al., 2000). These findings are also slightly similar to results obtained by Laxer and Marks (1977) in third world countries.
Present findings in some cases were differed from other reports (Farag et al., 2005; Bedford et al., 2001). In a study, bacterial agents of meningitis in 70% of children between 1 to 5 years of age were H. influenzae type b, N. meningitidis and S. pneumoniae, respectively (Gold, 1993). In other study from Central Iran, the most common causes of meningitis in children were H. influenzae type b, S. pneumonia, N. meningitidis and Salmonlla paratiphy A, respectively (Borjian, 1999). As observed, in most studies, H. influenzae type b and N. meningitidis are known as main causes of meningitis in infants and children, whereas in present study only 4.4% of patients had H. influenzae type b and 6.5% had N. meningitides. This event may be because of widespread of vaccination against these strains. With the decline in H. influenzae type b disease, cases of bacterial meningitis have decreased since 1986 (Feigin and Pearlman, 2004; Prober, 2004). Present study also revealed a decrease in the proportion of H. influenzae type b and N. meningitides in children. Meningococcal meningitis is a continuing threat in day-care centers and schools. Healthy children and young adults are susceptible and death can occur within a few hours of onset. In this study, N. meningitidis was not a common isolate.
In this study, Gram-negative bacilli including E. coli, P. aeruginosa, C. freundii and K. pneumonia had important contribution in creating bacterial meningitis (Table 1). S. aureus was also the second predominant cause of bacterial meningitis in patients involved. P. aeruginosa and S. aureus are versatile human pathogen that continues to be an important cause of nosocomial infections especially in pediatric units (Lin et al., 2004; Mihalache et al., 1999). P. aeruginosa and S. aureus meningitis in children and neonates were presented to withdraw attention to this clinical entity.
Clinical manifestation of bacterial meningitis in children in this study was not significantly different from that of other developing and developed countries, however it will help us in speedy diagnosis of our pediatrics patients. The diagnosis of bacterial meningitis is rarely a difficult diagnostic dilemma when a patient presents with fever, headache, neck stiffness and altered mental status. Although the clinical scenario may suggest meningitis, it is the cerebrospinal fluid white blood cell count that establishes the definitive diagnosis (Faria and Farhat, 1999). In our experience, fever, Leukocytosis, nausea and vomiting were the predominant of clinical findings of children with bacterial meningitis (Table 2). These findings are is agreement with some other studies (Al-Mazrou et al., 2004; Chang et al., 2004).
The appropriate treatment of bacterial meningitis has been controversial and has become more complex with the emergence of resistance to commonly used antibiotics. The pathogens that cause bacterial meningitis were found to be becoming increasingly resistant to the some common antimicrobial agents used in this study. Out of 8 tested antibiotics in this study, gentamicin, kanamycin and ceftizoxime were the most effective antibiotics in both Gram-positive cocci and Gram-negative bacilli. Regarding some reports (Saha et al., 2005; Karen et al., 2001; Foster and Rhoney, 2005), antibiotics of beta-lactam (ampicillin and amoxicllin), cephalosporin and also chloramphenicol have been recommended as effective drugs for those affected by bacterial meningitis, whereas most of the isolated bacteria in this study, showed high drugs resistance (between 20 to 100%) to many of these mentioned antibiotics (Table 4). S. pneumoniae, a common pathogen in pediatric infections, has become resistant to penicillin and makes these infections difficult to treat (Erdem and Pahsa, 2005; Hernandez et al., 2003). The National Reference Center in France for Pneumococci determined the susceptibility to antibiotics of 2,837 S. pneumoniae isolated in 1997 (Geslin, 1997). The incidence of S. pneumoniae with reduced susceptibility to penicillin G increased from 3.8% in 1987 to 48% in 1996 (Geslin, 1997). In this study, S. pneumoniae was the most common causes of meningitis and showed high resistance to amoxicllin, ampicillin and chloramphenicol. Rifampin and chloramphenicol have been recommended as alternative therapies, since they are less costly and more accessible to communities with limited resources (Hernandez et al., 2003). However, the differing levels of resistance found in target populations may restrict their use. In our communities, the increasing cost of treating resistant infections supports economic arguments for prevention through conjugate S. pneumoniae immunization.
The percentage of beta-lactamase-producing H. influenzae increased progressively in last few years (Dabernat et al., 2004). In Papua New Guinea more than 20% of H. influenzae type b meningitis are now resistant to chloramphenicol and resistant H. influenzae meningitis treated with chloramphenicol results in certain death or severe brain injury (Duke, 2002). Third-generation cephalosporins are a therapeutic option but are very expensive. In this study, H. influenzae type b, showed good susceptibility to kanamycin, gentamicin, chloramphenicol and cephalosporin.
Meningococcal resistance to antibiotics is emerging in some part of world. The incidence of N. meningitidis with reduced susceptibility to penicillin G increased from less than 1% in 1991 to 18% in 1996 in France. (Guibourdenche, 1997; Struillou et al., 1998). The strains belonged to various serogroups; most belonged to serogroup b, none produced a beta-lactamase and all were susceptible to cefotaxime and ceftriaxone. In our study, N. meningitidis showed a moderate resistance to cephalexin, amoxicllin, ampicillin and chloramphenicol.
In present study, S. aureus and Gram-negative bacilli such as E. coli, P. aeruginosa and K. pneumonia showed high resistance to many of tested antibiotics (Table 4). The emergence and spread multidrug-resistance among species of P. aeruginosa and S. aureus has become a major concern worldwide and is seriously challenging current treatment strategies (Karen et al., 2001; Foster and Rhoney, 2005). The emergence of third-generation cephalosporin non-susceptible E. coli strains in infant bacterial meningitis, as shown in this study, has caused a therapeutic challenge in choosing initial empirical antibiotics for treating infant patients with post-neurosurgical meningitis. Present results emphasize that the timely use of appropriate antibiotics is essential for the management of this potentially fatal central nervous system infection. However, it should be noted that the number of cases examined in this study is too small to reach a therapeutic conclusion regarding infant bacterial meningitis, and further large-scale studies will be needed for this purpose.
We may come to this conclusion that Gram-positive cocci are major agents in causing bacterial meningitis in children investigated in this region that showed quite high resistance to routine antibiotics like amoxicillin, ampicillin, sulfamethoxazole-trimethoprim and chloramphenical. Through this experience, it became apparent that for the initial treatment of bacterial meningitis in infants, it is necessary to apply a combination of two antibiotics, instead of a single agent and new antibiotics should be considered for such combinations rather than persisting on conventional of cephalosporin and beta-lactam antibiotics.
This study was funded by the Students Research Center of Hamadan University of Medical Sciences, Hamadan, Iran. The authors gratefully acknowledge of Mrs Z. Heidar Barghi for her technical assistance.
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