The principle aim of this study was to analyze the number of capb copies, and to assess sequence divergence in the hcsA and hcsB genes of Hib strains isolated from
children with Hib diseases in our district before the introduction of the Hib conjugate vaccine. A total of 24 Hib strains isolated between November 2004 and May 2009 from 24 children with invasive Hib diseases who had not received Hib conjugate vaccine in Kagoshima Prefecture, Japan, were collected and examined. Of these strains, 15 were isolated from CSF and 9 from blood. The strains were epidemiologically unrelated and individually stored at −80°C. All isolates were identified as serotype b by PCR capsular genotyping (14). PFGE was performed using a CHEF-DR 3 apparatus (Nippon Bio-Rad Laboratories, Tokyo, Japan) according to previously reported methodology (15). Briefly, DNA was digested by SmaI and separated on 1% agarose gels by PFGE under the following
JNK inhibitor mw conditions: current range, 100 to 130 mA at 14°C for 16 hr; initial switch time, 5.3 s, linearly increasing to a final switch time of 49.9 s; angle, 120°; field strength, 6 volts/cm. The gels were stained with ethidium bromide and photographed. A lambda with a size range of 48.5 kb to 1 Mb (BME, Rockland, ME, USA) was used as a size marker. For interpretation of banding patterns separated by PFGE, we referred to the criteria of Tenover et al. (16). selleck Two variants of the capb locus DNA sequence, type I and type II, were determined by PCR using two primer sets targeting the hcsA gene which could discriminate between the two capsular genotypes as described in a previous report (12). The DNA sequences of the PCR products were determined Lonafarnib purchase by an ABI Prism 310 sequencer (Applied Biosystems Japan, Tokyo, Japan). The number of capb locus copies was detected by Southern blotting analysis according to previously reported methods (8). Because KpnI and SmaI restriction sites flank the capb locus, extracted DNA in an agarose plug was digested with these enzymes, separated by PFGE, and transferred to a nylon membrane. A Hib
capsule-specific 480-bp probe was constructed by PCR (14) and labeled with DIG using a DIG high prime DNA labeling kit (Roche Diagnostics, Mannheim, Germany). The membrane was hybridized with the probe and visualized by chemiluminescent detection using a DIG detection kit (Roche Diagnostics). The Kpn I/Sma I fragment of a two copy strain was expected to be 45-kb, because it includes two repeats of the locus (18 + 17 kb) plus additional segments (∼10 kb) upstream and downstream of the cap region (17). Three-, four-, and five-copy fragments showed increased size in 18-kb increments for each additional copy (63, 81, and 99-kb, respectively) (8). A summary of results is shown in Table 1. The type I-associated hcsA gene was found in all of the strains examined. The DNA sequences of all the PCR products were completely identical. PFGE analysis showed nine distinctive restriction patterns (A to I) among the 24 isolates.
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