Lethal synergism induced in mice by influenza type A virus and type Ia group B streptococci.
Intranasal inoculation of CD-1 or BALB/c mice with low doses of influenza A/PR8/34 (HON1) virus followed 48 h later by intranasal inoculation of low doses of type Ia group B streptococci effected a lethal synergism. At a constant input dose of virus, a direct relationship between input dose of bacteria and percent mortality was observed; the converse was also true. An inverse relationship between input dose of group B streptococci, but not input dose of virus, and mean time to death was observed in CD-1 but not in BALB/c mice. The kinetics of influenza A/PR8/34 virus and group B streptococcal replication in singly and dually infected BALB/c mice was determined by assaying samples from the lungs, liver, spleen, and blood for viable group B streptococci and infectious influenza A/PR8/34 virus. No significant difference in virus replication in the lung was observed between singly and dually infected mice. Extrapulmonary dissemination of virus was not observed. Concurrent virus infection effected a 10,000- to 100,000-fold increase in the levels of type Ia group B streptococci in the lung. Potentiation of group B streptococcal infection of the lung was not associated with bacteremia or infection of the liver or spleen, a finding contrary to previous observations of fulminant septicemia after intranasal inoculation of mice with input doses of group B streptococci less than one-tenth of the pulmonary levels observed in the present study.
D000818:Animals; D000942:Antigens, Bacterial / Q000032:analysis; D000956:Antigens, Viral / Q000032:analysis; D005260:Female; D009980:Influenza A virus / Q000276:immunology / Q000472:pathogenicity*; D007700:Kinetics; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009976:Orthomyxoviridae Infections / Q000382:microbiology / Q000401:mortality; D011014:Pneumonia / Q000382:microbiology / Q000401:mortality; D013290:Streptococcal Infections / Q000382:microbiology / Q000401:mortality; D013292:Streptococcus agalactiae / Q000276:immunology / Q000472:pathogenicity*; D014774:Virulence; D014779:Virus Replication
D000942:Antigens, Bacterial; D000956:Antigens, Viral