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[Haemophilus influenzae type B: subtyping of strains isolated from respiratory infections using the outer membrane
M Catalano1, F A Rosetti, L B Ochoa
1Departamento de Microbiología, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
Abstract:
Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) applied to outer membrane protein (OMP), extracted by a micromethod, was employed to subtype H. influenza b type I. A total of 37 H. influenzae b strains were isolated from children under 4 years of age, either with lower acute respiratory infection (LARI), or asymptomatic carriers matched according sex, socioeconomic level and seasonality. Twenty seven out of the 37 H. influenzae b strains belonged to biotype I. On the basis of OMP profiles, these 27 were classified into 8 subtypes (Figs. 2, 3, 4 and 5). The probability of two randomly chosen isolates having different OMP profiles was 0.733. The subtype termed "a" showed the greatest relative frequency and was detected both in invasive strains and in those isolated from throat samples of LARI cases and healthy children. The use of 14% SDS-PAGE allowed de detection either of a 51kD or a 49kD, as well as 25-40kD proteins, in a single run (Fig. 1). Most subtype profiles showed the 51 kD protein. Growth conditions and extraction of OMPs by our modified micromethod provide a single and inexpensive procedure within the means of the average clinical laboratory. Besides, this test is much less time-consuming than classical assays. Jointly, biotyping , serotyping and OMP profile determination, proved a useful epidemiological tool to survey H. influenzae b infection.
Insights
Outer membrane protein (OMP) subtyping using SDS-PAGE identified 8 subtypes of Haemophilus influenzae type I strains from young children. Subtype "a" was most common, found in both invasive and carrier cases, aiding epidemiological surveillance.
Area of Science:
- Microbiology
- Immunology
- Molecular Biology
Background:
- Haemophilus influenzae type b (Hib) is a significant cause of invasive disease in young children.
- Accurate subtyping of Hib strains is crucial for understanding transmission dynamics and guiding public health interventions.
- Traditional methods for strain characterization can be time-consuming and resource-intensive.
Purpose of the Study:
- To develop and validate a rapid and cost-effective method for subtyping Haemophilus influenzae type b strains.
- To analyze the outer membrane protein (OMP) profiles of Hib strains isolated from children with lower acute respiratory infection (LARI) and asymptomatic carriers.
- To assess the epidemiological utility of OMP profiling for Hib surveillance.
Main Methods:
- Outer membrane proteins (OMPs) were extracted using a modified micromethod.
- Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) at 14% was used to analyze OMP profiles.
- Thirty-seven Hib strains from children under 4 years were analyzed, with 27 belonging to biotype I.
- OMP profiles were used to classify the 27 biotype I strains into 8 distinct subtypes.
Main Results:
- Twenty-seven of 37 H. influenzae type b strains were classified into 8 OMP subtypes.
- The probability of two random isolates having different OMP profiles was 0.733.
- Subtype 'a' was the most prevalent, detected in invasive strains and isolates from LARI cases and healthy children.
- SDS-PAGE effectively resolved proteins of 51 kD, 49 kD, and 25-40 kD, with most subtypes showing the 51 kD protein.
Conclusions:
- The modified micromethod for OMP extraction and SDS-PAGE is a simple, inexpensive, and rapid technique for subtyping H. influenzae type b.
- OMP profiling, combined with biotyping and serotyping, provides a valuable epidemiological tool for monitoring H. influenzae type b infections.
- The identified OMP subtypes, particularly the prevalent subtype 'a', can inform public health strategies for Hib control.