Phenotypic Characterization and Antibiogram of CSF Isolates in Acute Bacterial Meningitis

Abstract

Context: Acute bacterial meningitis (ABM) is a medical emergency, which warrants an early diagnosis and an aggressive therapy. Despite the availability of potent newer antibiotics, the mortality rate caused by acute bacterial meningitis remains significantly high in India and in other developing countries, which ranges from 16 - 32%. There is a need of a periodic review of bacterial meningitis worldwide, since the pathogens which are responsible for the infection may vary with time, geography and the age of the patient.

Aims: Our aim was to study the bacterial profiles and antimicrobial susceptibility patterns of the CSF isolates which were obtained from patients of acute bacterial meningitis in our area.

Settings and design: Two hundred and fifty two clinically diagnosed cases of acute bacterial meningitis, who were admitted to the wards of a tertiary medical centre in Patna, during the period from August 2011 to December 2012, were included in this study.

Material and methods: Two hundred and fifty two CSF samples from as many patients of ABM were processed for cell counts, biochemical analysis, gram staining, culture, antigen detection by latex agglutination test (LAT) and antibiotic susceptibility tests, as per the standard techniques.

Results: In this study, 62.3% patients were males and 37.7% were females The most common age group of presentation was 12-60 years (80.2%). Gram stained smears were positive in 162 (64.3%) samples, while culture yielded positive growth in 200 (79.4%) patients. Streptococcus pneumoniae was the most common pathogen which was isolated in 120 (60%) culture positive cases. Cell counts showed the predominance of neutrophils in all cases with ABM. High protein and low sugar levels correlated well with the features of ABM. All gram positive isolates were sensitive to vancomycin. All the gram negative isolates were sensitive to imipenem. Twenty two (8.7%) patients expired during the course of study. Deaths were caused by N.meningitidis in 9 (40.9%) cases, by S.pneumoniae in 3 (13.6%) cases and by H.influenzea in 1 (4.5%) case. In the remaining 9 (40.9%) mortality cases, the organism could not be identified.

Conclusion: Simple, rapid, inexpensive tests like gram staining remain significant means for diagnosis of ABM in developing countries. LAT for pneumococcal antigen should be performed first, since Streptococcus pneumoniae remains the major aetiological agent of ABM, both in adults and children. The final diagnosis of ABM depends upon a comprehensive analysis of CSF smears, cultures, LAT, cytological, biochemical and clinical findings of the cases, and a single test or parameter cannot be used to decide the course of management in the patients. However, empirical therapy is advocated, considering the potentially high rate of mortality in these patients.

Keywords: Acute bacterial meningitis; Antimicrobial susceptibility pattern; Haemophilus influenzae; Latex agglutination test; Neisseria meningitidis; Pyogenic meningitis; Streptococcus pneumoniae.

[Table/Fig-1]:

Percentage distribution of patients of ABM based on sex (n=252)

[Table/Fig-4]:

Etiological agents isolated in culture positive CSF samples (n=200)

[Table/Fig-5]:

Culture negative samples of CSF positive for antigens of S.pneumoniae, N.meningitidis and H.influenzae by LAT (n=52)