Effect of rifampin on nasopharyngeal carriage of Haemophilus influenzae type b

Elaboration of type b capsule by Haemophilus influenzae as a determinant of pathogenicity and impaired killing by trimethoprim-sulfamethoxazole.

“…In recent years, attention has been focused on the occurrence of secondary cases of invasive Hib infections in households or day-care centers where susceptible young children are in intimate contact and at high risk of developing invasive disease (1)(2)(3)(4)(5). Efforts to interrupt person-to-person spread of Hib in these settings have included the use of antibiotics such as trimethoprim-sulfamethoxazole (TMP/ SMZ) (1,3,7), rifampin, (6)(7)(8), cefaclor (9,10), and ampicillin (11)(12)(13). During an outbreak of Hib carriage and disease in a chronic disease hospital (3), TMP/ SMZ failed to eradicate nasopharyngeal carriage in 30% of carriers, although the minimal inhibitory concentration (MIC) of TMP/SMZ for these H. influenzae (Hi) strains indicated that they were susceptible.…”

“…No significant difference (P > 0.1) in the mean numbers of bacteria in blood or CSF was observed between treatment and control groups. 6 h after treatment none of the rats receiving saline (control group) has sterile blood or CSF cultures. In contrast, 13 cultures (P < 0.001), while a 10-fold reduction in the number of bacteria in blood (from 3.9±0.6 X 104/ml to 1.5±0.6 X 103/ml) was seen in the remaining 7 animals.…”

Duration of rifampin chemoprophylaxis for contacts of patients infected with Haemophilus influenzae type B

“…The currently recommended dosage of 20 mg of rifampin per kg once daily has been found to be 95% effective in eradicating pharyngeal colonization with Hib. Previous evaluations of 2-day therapy with rifampin employed a dose of 10 mg/kg given either daily (17) or twice daily (5) in contrast to the single daily dose of approximately 20 mg/kg used in the current study. In both of these earlier studies the effectiveness was considered unsatisfactory, probably attributable to a lower peak level of antibiotic.…”