Vol.64 No.2 March 2016
Comparison of the clinical characteristics of community-acquired pneumonia in adults due to the mucoid and non-mucoid phenotype of Streptococcus pneumoniae
1)Department of Respirology, Shinrakuen Hospital, 3-3-11 Shindori-minami, Nishi-ku, Niigata, Japan
2)Department of Clinical Laboratory, Shinrakuen Hospital
Abstract
Two phenotypes of Streptococcus pneumoniae exist, mucoid and non-mucoid, which are classified based on colony morphology. However, the differences in their clinical characteristics have not yet been investigated. In this study, at the Shinrakuen Hospital from May 2013 to November 2014, we classified cases of adult pneumococcal pneumonia into two groups according to the aforementioned causative phenotypes. We also compared patients' backgrounds, clinical courses, antimicrobial susceptibility, and capsular polysaccharide serotypes.
Of the 17 patients with pneumococcal pneumonia, 6 (35.3%) were classified into the mucoid group, and 11 (64.7%) were classified into the non-mucoid group. All mucoid phenotypes were of the capsular serotype 3 and were more susceptible to penicillin G than were the non-mucoid phenotypes. On admission, the C-reactive protein titer was significantly higher in the mucoid group (28.4± 12.4 mg/dL) than in the non-mucoid group (13.7± 7.0 mg/dL, p=0.006). The mucoid group also showed a wider spread of infiltrates on chest radiography. There were no fatal cases in either group, but the mucoid group had a significantly higher number of cases with initial treatment failure (p=0.041) and longer periods of antimicrobial use (16.7± 9.8 days in the mucoid group and 8.1± 2.0 days in the non-mucoid group, p=0.012).
Our findings indicate that colony morphology (mucoid or non-mucoid phenotype) could be a prognostic factor in cases of pneumococcal pneumonia in adults. It is known that S. pneumoniae strains that produce greater amounts of capsular polysaccharide show the mucoid phenotype and that capsular polysaccharide confers resistance against complement-mediated opsonophagocytosis. Considering these two facts makes our results easy to understand.
Key word
Streptococcus pneumoniae, mucoid strain, community-acquired pneumonia, capsular serotype, drug susceptibility
Received
August 27, 2015
Accepted
October 29, 2015
Jpn. J. Chemother. 64 (2): 280-285, 2016
