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Enhanced nasopharyngeal colonization of rats by piliated Haemophilus influenzae type b
Abstract:
Piliated Haemophilus influenzae type b strains display an enhanced adherence to human epithelial cells in vitro. However, clinical isolates, even from mucosal sites, are seldom piliated, although piliated populations can be selected from them. Experiments with rats have led some authors to suggest that piliation does not implement colonization by H. influenzae type b. Piliated populations were obtained from 35 strains by selection for adherence to human erythrocytes. One strain, H. influenzae H305, simultaneously acquired an increased adherence to rat erythrocytes and buccal epithelial cells. In contrast to other strains, H. influenzae H305 in piliated form was more effective than in nonpiliated form in the colonization of rats by intranasal inoculation. After the piliated inoculum, however, the colonies cultured from the nasal washes were negative for erythrocyte adherence. Thus, piliated H. influenzae type b strains have an apparent advantage to initiating colonization in the rat model but may give rise to nonpiliated progeny that are more readily cultivable from the mucosal surface.
Insights
Piliated Haemophilus influenzae type b show better initial colonization in rats. However, these piliated bacteria may produce nonpiliated offspring that are easier to grow from mucosal surfaces.
Area of Science:
- Microbiology
- Infectious Diseases
- Bacterial Pathogenesis
Background:
- Piliated Haemophilus influenzae type b (Hib) strains exhibit enhanced in vitro adherence to human epithelial cells.
- Clinical Hib isolates are rarely piliated, despite the ability to select for piliated populations.
- Previous rat studies suggested piliation does not aid Hib colonization.
Purpose of the Study:
- To investigate the role of piliation in Haemophilus influenzae type b colonization using a rat model.
- To determine if piliated Hib strains have an advantage in initiating colonization compared to nonpiliated strains.
Main Methods:
- Piliated Hib populations were generated from 35 clinical strains by selecting for adherence to human erythrocytes.
- One strain, H. influenzae H305, was characterized for altered adherence to rat erythrocytes and buccal cells after piliation.
- Colonization efficiency of piliated and nonpiliated H. influenzae H305 was assessed in rats via intranasal inoculation.
Main Results:
- Piliation of H. influenzae H305 increased its adherence to rat erythrocytes and buccal epithelial cells.
- Piliated H. influenzae H305 demonstrated superior colonization of rat nasal passages compared to its nonpiliated form.
- Bacterial colonies cultured from nasal washes post-piliated inoculum were predominantly nonpiliated and lacked erythrocyte adherence.
Conclusions:
- Piliated Hib strains possess an initial colonization advantage in the rat model.
- Piliated Hib may rapidly transition to nonpiliated forms on mucosal surfaces, facilitating subsequent cultivation.
- The findings suggest a dynamic role for piliation in the early stages of Hib infection.