Different virulence of influenza A virus strains and susceptibility to pneumococcal otitis media in chinchillas

Abstract

We have previously shown that chinchillas infected with a multiply passaged laboratory strain of influenza A/NWS/33 (HlNl) develop negative middle-ear pressure; polymorphonuclear leukocyte oxidative, bactericidal, and chemotactic dysfunction; and increased susceptibility to pneumococcal otitis media. Because influenza A virus strains show different virulence in humans, three such strains were compared in the chinchilla model. Negative middle-ear pressure and tympanic membrane inflammation developed significantly more often in chinchillas infected with wild-type H3N2 virus than with either wild-type HlNl virus or an attenuated, cold-adapted H3N2 vaccine strain, CR29. Marked depression in polymorphonuclear leukocyte chemiluminescent activity also developed significantly more often in H3N2 infected animals than in HlNlor CR29-infected animals. Intranasal challenge of influenza virus-infected animals with type 7 Streptococcus pneumoniae resulted in a significantly greater occurrence of pneumococcal otitis media in H3N2-infected animals than in HlNl-, CR29-, or non-influenza-infected control animals. Clearance of pneumococci from nasal washings of animals infected with wild-type H3N2 was significantly delayed in comparison with the other groups. Thus, the previously demonstrated increased susceptibility to otitis media among children infected with H3N2 influenza virus may relate to the capacity of this strain to induce negative middle-ear pressure, polymorphonuclear leukocyte dysfunction, and alteration in the mucosal clearance of pneumococci.

Risk factors for acute severe pneumonia in under five children

“…The basis for susceptibility to bacterial pneumonia following influenza and influenza like infections include decrease in the function of leucocytes, macrophages, lymphocytes and monocytes, increase in the adherence of bacteria to respiratory epithelium and decrease muco-ciliary clearance History of URTI in family was an independent risk factor for severe pneumonia. 30,31 Similar results have been observed by Broor et al, Cerqueiro et al, and O'Brien et al 20,26,32 Authors therefore conclude that environmental factor (use of cooking-fuel other than LPG) and socio-demographic factors (low literacy status of the mother, incomplete immunization status) are modifiable risk factors for severe pneumonia. As for any disease primary prevention is generally superior and cost effective as compared to tertiary prevention and cure, appropriate preventive measures against these risk factors may help to reduce the morbidity and mortality of acute severe pneumonia.…”

Immunopathogenesis of polymicrobial otitis media

“…The degree to which a particular virus compromises the airway and particularly, the protective functions of the Eustachian tube has a tremendous influence on whether bacterial OM will develop and how severe the disease course will be. Giebink and Wright [86] clearly showed this correlation when they reported that strains of influenza A virus had markedly different levels of virulence in the chinchilla host when development of a negative middle-ear pressure, neutrophil dysfunction, and increased susceptibility to pneumococcal OM included the outcomes measured. These data thus supported epidemiological evidence that had already shown there to be striking differences in AOM prevalence in association with different influenza A outbreaks.…”

Role of Toll-like receptor 4 in innate immune responses in a mouse model of acute otitis media

“…The tympanic membrane color and opacity were recorded and graded in increasing order of inflammation and increasing correlation with the presence of MEEs according to the severity of acute otitis media as follows: 0, gray and translucent tympanic membrane without MEE (normal); 1, gray and opaque tympanic membrane with serous or mucoid MEE; 2, yellow and opaque tympanic membrane with purulent MEE. These grading scales are referred to Giebink & Wright (1983). At 6, 12, 24, 48 and 72 h after injection, 10 mice from each group were sacrificed under deep anesthesia by intraperitoneal administration of pentobarbital solution.…”