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[Molecular characterization of invasive Haemophilus influenzae strains isolated in Tunisia]
Y Ben Salem1, O Boullegue, M Mastouri
1Faculté de Pharmacie de Monastir, Tunisie.
Abstract:
We reported a molecular characterization of 25 Haemophilus influenzae strains derived from cases of meningitis and sepsis in children aged less than five years hospitalized in pediatric wards from three hospitals in the Sahel area (Tunisia) during the period 1997-2002. These strains were biotyped and subjected to a capsular typing by Slide agglutination serotyping and Polymerase Chain Reaction (PCR). The genetic polymorphism of these strains was also studied in Arbitrarily Primed Polymerase Chain Reaction (AP-PCR) with two sets of primers: RAP IV and 217 delta(2) as in Pulsed Field Gel Electrophoresis after digestion of the total DNA with the restriction enzyme SmaI (PFGE SmaI). Nineteen strains among 25 (76%) were of biotype I. The bexA gene was highlighted in 13 strains (52%) and in all the cases it was of the type b. Twelve strains (48%) were shown to be unencapsulated by PCR. AP-PCR RAP IV (23 genotypes/25 with a discrimination index ID=0.993) had shown nearly the same discriminatory power than PFGE (20 genotypes/21 strains with a discrimination index ID=0.995). We thus note, how capsular typing by PCR is more sensitive than slide agglutination serotyping. We also note the genetic diversity of the invasive strains isolated with a remarkable presence of non typable strains. AP PCR seems to be an alternative of choice for the epidemiologic follow-up of the Haemophilus influenzae invasive infections.
Insights
Molecular characterization of Haemophilus influenzae strains from Tunisian children revealed significant genetic diversity. Arbitrarily Primed PCR (AP-PCR) proved effective for tracking invasive infections and showed PCR capsular typing is more sensitive than slide agglutination.
Area of Science:
- Microbiology
- Molecular Biology
- Epidemiology
Background:
- Haemophilus influenzae is a significant cause of meningitis and sepsis in young children.
- Characterizing invasive strains is crucial for understanding disease transmission and developing control strategies.
Purpose of the Study:
- To perform a molecular characterization of Haemophilus influenzae strains from pediatric meningitis and sepsis cases in Tunisia.
- To compare the discriminatory power of different molecular typing methods for epidemiological surveillance.
Main Methods:
- Biotyping, capsular typing (slide agglutination, PCR), Arbitrarily Primed PCR (AP-PCR), and Pulsed Field Gel Electrophoresis (PFGE) were used.
- Genetic polymorphism was assessed using AP-PCR with RAP IV and 217 delta(2) primers and PFGE SmaI.
Main Results:
- 76% of strains were biotype I; 52% harbored the bexA gene (type b).
- 48% of strains were unencapsulated by PCR.
- AP-PCR RAP IV and PFGE demonstrated high discriminatory power (ID=0.993 and 0.995, respectively).
- PCR capsular typing was more sensitive than slide agglutination serotyping.
Conclusions:
- Haemophilus influenzae invasive strains exhibit considerable genetic diversity, including a notable proportion of non-typable strains.
- AP-PCR is a valuable tool for the epidemiological follow-up of invasive Haemophilus influenzae infections.
- Molecular methods like PCR offer improved sensitivity for capsular typing compared to traditional serotyping.
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