Clinical features, antimicrobial resistance and serotypes of Streptococcus agalactiae in southern Taiwan

Autor: Ying Hsiang Wang, 王盈翔
Rok vydání: 2015
Druh dokumentu: 學位論文 ; thesis
Popis: 104
To investigate the clinical features, antimicrobial resistance, serotypes and risk factors associated with streptococcus agalactiae infection in southern Taiwan, a series of studies on useful grading systems to predict invasive diseases and population structure within streptococcus agalactiae isolates by examining capsular serotype, resistance phenotype and PFGE (pulse-field gel electrophoresis) genotype have been done. 1. A comparison of invasive and non-invasive group B streptococcus (GBS) infection The clinical and microbiological characteristics of 228 GBS isolates from 226 hospitalized non-pregnant patients during a prospective study from October 2006 to June 2008. We found that invasive disease was tended to be more predominant in male, involve in subjects who were > 40 years old and cause from hospital-acquired GBS. Charlson Comorbidity Index (CCI) is a better predictive factor for invasive GBS diseases than individual comorbid conditions. This study demonstrated higher resistance to erythromycin (58.3%) and clindamycin (57.9%) associated with resistance phenotype cMLSB (60.1%), iMLSB (25.2%), M (7.7%) and LSA (7.0%). The major serotypes were V (29.4%), Ib (24.6%), III (14.0%), VI (10.5%) and IV (10.1%). Emergence of prevalent serotype Ib showed higher resistance to erythromycin (91.0%) and clindamycin (82.1%). Among 56 serotype Ib isolates, only 4 isolates were non-resistant and revealed relatively heterogenous PFGE patterns, whereas 67.3% (35 of 52) of the resistant serotype Ib isolates showed identical PFGE patterns (genotype A1). These results, indicating possible genetic clustering of a resistant clone family within the serotype Ib population. 2. Examination the correlation of drug-resistant genes with serotypes and with the mutations of the quinolone resistance-determining region (QRDR) in GBS isolates The ermB and mefE genes carried in serotypes Ib and V were highly associated with the resistance to macrolides and clindamycin. GBS with a serine-to-leucine mutation at codon 81 in GyrA and with a serine-to-phenylalanine or serine-to-tyrosine mutation at codon 79 in ParC had a higher minimum inhibitory concentration (MIC) of levofloxacin than isolates with only an aspartic acid-to-tyrosine mutation at codon 83 (>32 μg/mL vs. 16 μg/mL) in GyrA. 3. The clinical characteristics of recurrent GBS infection, specifically with respect to useful grading systems to predict recurrence. Recurrent rate was 9.3% (32/345). CCI is a better predictive factor for recurrence (P=0.011) than individual comorbid conditions. The clinical diagnosis of 70 episodes mainly comprised 39 urinary-tract infections (U), 22 soft-tissue infections (S), and 9 bloodstream infections (B). The prevalent ST/SGs belonging to recurrent strains were serotype V (34.3%), Ib (22.9%), VI (17.1%), III (12.9%), IV (7.1%), and Ia (5.7%). Recurrent strains maintained lower frequency of resistance to erythromycin or clindamycin when compared with non-recurrent strains (51.4% versus 66.1%, respectively; P=0.021). A point of concern is the finding of serotype VI, less common serovar previously, responsible for 17.1% of the recurrent strains and 7.7% of the non-recurrent strains (P=0.014). We examined the genetic diversity on the 12 strains of serotype VI (derived from 7 individuals with recurrence). Five isolate pairs were identical by PFGE, whereas genotypically heterogeneous structures (6 distinct PFGE patterns) corresponding to these 7 patients. Our data supported that relapse is a pivotal factor in disease recurrence. 4. Clinical features and risk factors for group B streptococcal skin and soft tissue infections GBS soft tissue infections (STIs) most frequently develop in adult, particularly between 40 and 59 years. Male was more common in overall GBS infection than female (65.6%, 21/32 versus 34.4%, 11/32, respectively). The relation between the leukocytosis, inflammatory syndrome markers (CPR, ESR) and anemia is clear but without statistical significance. Hyperglycemia (serum glucose＞180 mg/dL) can be used as diagnostic evaluation tools being strongly correlated with the severity of the soft tissue infections. Physicians must pay special attention to the patients with higher cumulative number of the laboratory risk indicator for necrotizing fasciitis score (LRINEC) cutoff points because they are at particular high risk to have severe GBS STIs [OR=25.333（95％CI=3.531-181.781）;LRINEC≧5; P
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