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Naturally occurring NAD-independent Haemophilus parainfluenzae
1Emergent Pathogen Research Unit, South African Medical Research Council, School of Pathology, University of Witwatersrand, Parktown, Johannesburg.
Abstract:
Four, NAD-independent, clinical isolates of Haemophilus parainfluenzae were recovered from a genital ulcer, a purulent skin lesion, a sputum specimen and a throat swab respectively. With the exception of NAD requirement, the strains exhibited the biochemical characteristics of H. parainfluenzae biotype II. The genetic relationship between these isolates and a standard strain of H. parainfluenzae was determined by testing transforming activities of two chromosomal markers, streptomycin resistance and nalidixic acid resistance. The clinical isolates were efficient donors and recipients in transformation. In addition, we demonstrated transfer of the genes conferring NAD independence to typical, NAD-requiring H. parainfluenzae and Haemophilus influenzae strains.
Insights
Four clinical isolates of Haemophilus parainfluenzae were found to be independent of nicotinamide adenine dinucleotide (NAD). These NAD-independent strains could transfer this trait to other bacteria, including Haemophilus influenzae.
Area of Science:
- Microbiology
- Bacterial Genetics
- Clinical Microbiology
Background:
- Haemophilus parainfluenzae is a common commensal bacterium.
- Most strains of H. parainfluenzae require nicotinamide adenine dinucleotide (NAD) for growth.
- NAD-independent strains are rare and their genetic basis is not well understood.
Purpose of the Study:
- To characterize NAD-independent clinical isolates of H. parainfluenzae.
- To investigate the genetic relatedness of these isolates to standard H. parainfluenzae strains.
- To determine if the NAD-independent trait is transferable.
Main Methods:
- Isolation and biochemical characterization of clinical strains.
- Genetic analysis using transformation assays with streptomycin and nalidixic acid resistance markers.
- Testing the ability of NAD-independent strains to transfer the NAD-independent trait.
Main Results:
- Four NAD-independent clinical isolates of H. parainfluenzae were identified from various infection sites.
- These isolates shared biochemical characteristics with H. parainfluenzae biotype II.
- The NAD-independent isolates were efficient in genetic transformation.
- Genes conferring NAD independence were successfully transferred to NAD-requiring H. parainfluenzae and H. influenzae.
Conclusions:
- NAD-independent H. parainfluenzae strains exist in clinical settings.
- The NAD-independent trait is genetically transferable, suggesting a mobile genetic element.
- This finding has implications for understanding H. parainfluenzae pathogenesis and evolution.