Multidrug resistance (MDR), specifically to ampicillin and chloramphenicol, has complicated the treatment of Haemophilus influenzae type b (Hib) meningitis. This is worsened by use of prior antibiotics, which limits identification of the causative agent by culture and increases reliance on antigen detection.
We aimed to develop a PCR assay for detecting the family of Haemophilus integrating and conjugative elements (ICEs) represented by ICEHin1056 among antibiotic resistant Hib, and then apply this directly to CSF to diagnose Hib meningitis and predict organism susceptibility, irrespective of culture results.
Primers specific for orf 51 of ICEHin1056 were designed and multiplexed with Bex primers, specific for H. influenzae, and tested on culture positive and negative cases.
Of 73 Hib isolates, orf 51 PCR amplicons, predicting the presence of ICEs, were found in all 33 MDR isolates while only in 1 of 33 sensitive strains. The remaining 7 ampicillin susceptible, chloramphenicol and tetracycline resistant strains did not produce a PCR product to orf 51. PCR amplification from CSF specimens of these culture positive cases produced identical results with 100% and 97% positive and negative predictive values, respectively. Multiplex PCR to detect Bex and orf 51 identified another 16 MDR Hib cases among 81 culture-negative CSF samples.
Direct PCR for orf 51 in CSF identified resistance pattern of 51% more Hib strains than culture alone (110 versus 73). The ability to detect MDR, in culture negative Hib meningitis cases has significant implications for better directing antibiotic treatment of meningitis cases and thus for preventing disability and death.
From the *Department of Microbiology, Dhaka Shishu (Children) Hospital, Dhaka, Bangladesh; †Department of International Health, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD; ‡Child Health Programme, ICDDR,B, Dhaka, Bangladesh; §Department of Child and Adolescent Health and Development, World Health Organization, Geneva, Switzerland; and ∥Infectious Diseases and Clinical Microbiology, University of Oxford, UK.
Accepted for publication July 6, 2007.
Nurul Islam, PhD, is currently with the Laboratory of Genetics, National Institute on Aging, National Institutes of Health, Baltimore, MD.
The study was partially supported by the Wellcome Trust—Burroughs Wellcome Fund Infectious Disease Initiative; the Department of Child and Adolescent Health and Development, World Health Organization, Geneva, Switzerland; and Dhaka Shishu Hospital, Bangladesh.
Address for correspondence: Samir K. Saha, PhD, Professor and Head, Department of Microbiology, Bangladesh Institute of Child Health, Dhaka Shishu (Children) Hospital, Dhaka 1207, Bangladesh.- E-mail firstname.lastname@example.org.