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Nasopharyngeal bacterial colonisation is not necessarily asymptomatic
  1. A Finn1,
  2. D Foster2,
  3. G Goncalves3,
  4. A Brett4,
  5. F Rodrigues4
  1. 1Cellular and Molecular Medicine, University of Bristol, Bristol, UK
  2. 2Nuffield Department of Medicine, Oxford University, Oxford, UK
  3. 3ICBAS, Universidade do Porto, Porto, Portugal
  4. 4Infectious Diseases Unit, Hospital PediÃtrico de Coimbra, Coimbra, Portugal

Abstract

Nasal colonisation with bacteria including pneumococcus (Pnc), Haemophilus influenzae (H flu) and Staphylococcus aureus is generally assumed to be asymptomatic. The authors hypothesised that it is associated with upper respiratory symptoms. 439 children (4–75 months, 233 males) attending six nurseries each had alginate nasal swabs taken in February 2009 and stored in STGG broth. At sampling, nurses obtained a single symptom score for nasal discharge, nasal blockage and sneezing from parents as follows: 0, none; 1, mild–slight; 2, moderate–definite; 3, severe–bad. Swabs were cultured and bacteria identified using standard methods. For pneumococcus, density was scored as 1–5(1), -20(2), -50(3), -100(4), >100(5) colonies/50 μl broth. 231 (52.6%), 134 (30.5%) and 62 (14.1%) swabs were positive for Pnc, H flu and S aureus, respectively. Among 428 children for whom scores were available, the proportion of children colonised with Pnc and H flu rose progressively with rising symptom scores (χ2 for trend p=0.00023, 0.00001) but appeared to fall for S aureus (table 1, ns). Symptom scores and Pnc colonisation density were strongly correlated (figure 1) (p=0.00021).

Abstract G57 (P) Table 1

These results show that uncomplicated nasopharyngeal colonisation with Pnc and H flu but not S aureus in healthy children is strongly associated with nasal symptoms which are correlated to carriage density at least for Pnc. This could be because Pnc and H flu induce these symptoms and S aureus does not. This would be consistent with known proinflammatory effects of Pnc on respiratory epithelium. Such symptoms may promote transmission but also elimination. S aureus, which commonly colonises the skin, may utilise other mechanisms. Alternatively respiratory viral infections, commonly associated with rhinitis, may cause symptoms and thus promote either acquisition or proliferation of Pnc and H flu but not S aureus. Further studies to detect common viruses in these samples may therefore help further elucidate these cause and effect relationships.

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