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|Title: ||Pattern of pathogens and utility of latex agglutination tests in bacterial meningitis|
|Authors: ||Al-Zamil, Fahad|
Qureshi, Irfan M.
Kambal, Abdel Mageed
|Issue Date: ||Nov-2002 |
|Citation: ||Annals of Saudi Medicine: 22 (5-6); 388-391|
|Abstract: ||A total of 4180 cerebrospinal fluid (CSF) specimens from patients with bacterial meningitis, which were received by the Microbiology Laboratory of the King Khalid University Hospital (Riyadh, Saudi Arabia) between January 1995 and December 1998, were examined for the presence of classical and non-classical bacterial pathogens using Gram staining and latex agglutination test (LAT). Of 4180 CSF samples examined, 141 were culture-positive. Most of these positive cases (n=98, 69.6%) belonged to the paediatric age group (neonates and children); the remaining 43 (30.4%) belonged to adults, including young adults. Coagulase negative staphylococci (22.2%) and Pseudomonas aeruginosa (16.3%) were the most common bacteria isolated, followed by Haemophilus influenzae type b (7%), Staphylococcus aureus (4.9%), Acinetobacter spp. (4.9%), Streptococcus pneumoniae (4.9%), Klebsiella pneumoniae (4.2%), Neisseria meningitidis (3.5%), group B streptococci (2.8%), Escherichia coli (1.4%), and others (17%). Most of the cases of coagulase negative staphylococci (72.9%) and P. aeruginosa (69.5%) were seen in neonates and children. All H. influenzae type B and group B streptococcal isolates were from children and neonates. Gram staining detected 56.7% (80/141) of the culture-positive samples. It gave presumptive identification of 90.9% of H. influenzae type b, 83.3% of N. meningitidis, 80% of S. pneumoniae, and detected 66.7% of E. coli and 100% of group B streptococci, all classical pathogens. Of the non-classical pathogens, 52.1% of P. aeruginosa and 37.5% of Staphylococcus epidermidis were detected by Gram staining. The overall sensitivity of the Gram staining in CSF specimens was 56.7%, and the specificity was 99%. The positive- and negative-predictive values were 68.3% and 98.4%, respectively. LAT was performed on 543 (12.9%) cases, of which 21 were positive. The LAT identified 76.1% (16/21) of the classical culture-proven isolates, including all 7 (100%) isolates of H. influenzae type b, 60% of S. pneumoniae, and 50% of group B streptococci. The sensitivity of LAT for the classical pathogens was 76.1%, and the specificity was 98.9%. The positive- and negative-predictive values were 76.1% and 98.5%, respectively. After a detailed review of the medical records, LAT was true positive in 3 cases, but false positive in 2 cases, in which S. epidermidis was isolated. The details of these 5 cases are summarized. It is concluded that LAT has declined in favour, and needs to be performed selectively under a high clinical suspicion of meningitis and negative Gram stain, or under high clinical suspicion of meningitis and prior antibacterial therapy.|
|Appears in Collections:||King Khalid Hospital|
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