Role of viral and bacterial pathogens in causing pneumonia among Western Australian children: a case–control study protocol

Bhuiyan, Mejbah Uddin; Snelling, Thomas L; West, Rachel; Lang, Jurissa; Rahman, Tasmina; Borland, Meredith L; Thornton, Ruth; Kirkham, Lea-Ann; Sikazwe, Chisha; Martin, Andrew C; Richmond, Peter C; Smith, David W; Jaffe, Adam; Blyth, Christopher C

There is evidence that respiratory viruses may have a role in facilitating bacterial colonisation, enhancing bacterial infection, and/or in enhancing disease severity either directly or indirectly. Viruses disrupt the respiratory epithelium barrier and also alter the defence mechanism of host epithelium potentially leading to bacterial entrance and enabling secondary bacterial infection [35, 36] . The incidence of invasive pneumococcal infection has been observed to be higher during increased seasonal activity of some respiratory viruses including influenza, RSV, parainfluenza 3 and 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 F o r p e e r r e v i e w o n l y 5 adenovirus [37, 38] . Further, in clinical trials in South Africa, conjugate pneumococcal vaccination resulted in overall decrease in virus-associated pneumonia, suggesting interactions between respiratory viruses and pneumococcus in causing pneumonia in children [39] . In Australia, ecological data has demonstrated a reduction in viral pneumonia following introduction of PCV vaccines [40] . RSV has been reported to facilitate bacterial colonization with Haemophilus influenzae, Streptococcus pyogenes, Staphylococcus aureus, and Moraxella catarrhalis in the nasopharynx of young children with acute respiratory infection [41] . Another study in Australia identified Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus in 25% patients in intensive care who were admitted with severe influenza A infection during 2009 Influenza pandemic [42] . The patients with viral-bacterial co-infection has been reported to suffer for treatment failure, longer ventilator support and increased likelihood of intensive care unit admission [12, [43] [44] [45] .