Investigating the role of pneumococcal neuraminidase A activity in isolates from pneumococcal haemolytic uraemic syndrome.
Streptococcus pneumoniae diseases are a rare but increasingly recognized trigger of atypical haemolytic uraemic syndrome (HUS) in young children and associated with a higher mortality rate than diarrhoea-associated HUS. This study aimed to determine the importance of neuraminidase A (NanA) and genomic diversity in the pathogenesis of pneumococcal HUS (pHUS). We investigated the nanA gene sequence, gene expression, neuraminidase activity and comparative genomic hybridization of invasive pneumococcal disease (IPD) isolates from patients with pHUS and control strains matched by serotype and sequence type (ST), isolated from patients with IPD but not pHUS. The nanA sequence of 33 isolates was determined and mutations at 142 aa positions were identified. High levels of diversity were observed within the NanA protein, with mosaic blocks, insertions and repeat regions present. When comparing nanA allelic diversity with ST and disease profile in the isolates tested, nanA alleles clustered mostly by ST. No particular nanA allele was associated with pHUS. There was no significant difference in overall neuraminidase activity between pHUS isolates and controls when induced/uninduced with N-acetylneuraminic acid. Comparative genomic hybridization showed little difference in genetic content between the pHUS isolates and the controls. Results of gene expression studies identified 12 genes differentially regulated in all pHUS isolates compared with the control. Although neuraminidase enzyme activity may be important in pHUS progression and contribute to pathogenesis, the lack of a distinction between pHUS isolates and controls suggests that host factors, such as acquired abnormalities of the alternative complement cascade in young children, may play a more significant role in the outcome of pHUS.
College of Medical, Veterinary & Life Sciences, Glasgow Dental Hospital & School, University of Glasgow, 378 Sauchiehall Street, Glasgow G2 3JZ, UK.
Andrew
A
Smith
National Centre for Scientific Research, Laboratory of Microbiology and Molecular Genetics, Toulouse University, Toulouse, France.
Calum
C
Johnston
Microbiology Department, Monklands Hospital, Monkscourt Avenue, Airdrie ML6 0JS, UK.
Donald
D
Inverarity
Respiratory & Vaccine Preventable Bacteria Reference Unit, Public Health England, 61 Colindale Avenue, Colindale, London NW9 5HT, UK.
Mary
M
Slack
Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK.
Gavin
G
K Paterson
East Midlands Pathology, Nottingham University Hospitals NHS Trust, Nottingham NG7 2UH, UK.
Mathew
M
Diggle
Institute of Microbiology and Infection, School of Immunity and Infection, University of Birmingham, Birmingham B15 2TT, UK.
Timothy
T
Mitchell
D000483:Alleles; D002675:Child, Preschool; D055028:Comparative Genomic Hybridization; D020869:Gene Expression Profiling; D014644:Genetic Variation; D006463:Hemolytic-Uremic Syndrome / Q000209:etiology*; D006801:Humans; D007223:Infant; D009439:Neuraminidase / Q000235:genetics / Q000633:toxicity*; D011008:Pneumococcal Infections / Q000150:complications* / Q000382:microbiology; D017422:Sequence Analysis, DNA; D013296:Streptococcus pneumoniae / Q000145:classification / Q000201:enzymology* / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics / Q000633:toxicity*
D037521:Virulence Factors; D009439:Neuraminidase