Molecular Characterization of Clostridium difficile Isolates from Human Subjects and the Environment.

Clostridium difficile is a spore-forming, gram-positive, anaerobic bacillus that can cause C. difficile infection (CDI). However, only a few studies on the prevalence and antibiotic resistance of C. difficile in healthy individuals in China have been reported. We employed a spore enrichment culture to screen for C. difficile in the stool samples of 3699 healthy Chinese individuals who were divided into 4 groups: infants younger than 2 years of age and living at home with their parents; children aged 1 to 8 years of age and attending three different kindergarten schools; community-dwelling healthy adult aged 23-60 years old; and healthcare workers aged 28-80 years old. The C. difficile isolates were analyzed for the presence of toxin genes and typed by PCR ribotyping and multilocus sequence typing (MLST). The minimum inhibitory concentration of 8 antimicrobial agents was determined for all of the isolates using the agar dilution method. The intestinal carriage rate in the healthy children was 13.6% and ranged from 0% to 21% depending on age. The carriage rates in the 1654 community-dwelling healthy adults and 348 healthcare workers were 5.5% and 6.3%, respectively. Among the isolates, 226 were toxigenic (225 tcdA+/tcdB+ and 1 tcdA+/tcdB+ ctdA+/ctdB+). Twenty-four ribotypes were found, with the dominant type accounting for 29.7% of the isolates. The toxigenic isolates were typed into 27 MLST genotypes. All of the strains were susceptible to vancomycin, metronidazole, fidaxomicin, and rifaximin. High resistance to levofloxacin and ciprofloxacin at rates of 39.8% and 98.3%, respectively, were observed. ST37 isolates were more resistant to levofloxacin than the other STs. The PCR ribotypes and sequence types from the healthy populations were similar to those from the adult patients

eBURST diagram of the 226 toxigenic <i>C</i>. <i>difficile</i> isolates from the healthy individuals.

<p>(a) Population snapshot showing the clusters of linked sequence types (STs) and unlinked STs in the entire <i>C</i>. <i>difficile</i> MLST database. (b) Three new STs (286, 289, and 290) were identified in this study.</p

Abundance of STs (%) in the 3 study populations.

<p>Data on the STs of <i>C</i>. <i>difficile</i> isolates from adult inpatients with diarrhea were obtained from a survey conducted in China in 2011.</p

MICs of 8 antimicrobial agents for toxigenic and non-toxigenic <i>C</i>. <i>difficile</i> isolates as determined by using agar dilution.

<p>MICs of 8 antimicrobial agents for toxigenic and non-toxigenic <i>C</i>. <i>difficile</i> isolates as determined by using agar dilution.</p

MICs of 8 antimicrobial agents for 344 <i>C</i>. <i>difficile</i> isolates determined by the agar dilution method.

<p>MICs of 8 antimicrobial agents for 344 <i>C</i>. <i>difficile</i> isolates determined by the agar dilution method.</p

Frequency of PRs among the 344 <i>C</i>. <i>difficile</i> isolates from healthy Chinese individuals.

<p>Frequency of PRs among the 344 <i>C</i>. <i>difficile</i> isolates from healthy Chinese individuals.</p

Characteristics of the 226 toxigenic <i>C</i>. <i>difficile</i> strains: genotype and antimicrobial susceptibility.

<p>Characteristics of the 226 toxigenic <i>C</i>. <i>difficile</i> strains: genotype and antimicrobial susceptibility.</p

Asymptomatic intestinal <i>C</i>. <i>difficile</i> carriage rate (%) in healthy children in the 3 kindergartens(group B).

<p>Asymptomatic intestinal <i>C</i>. <i>difficile</i> carriage rate (%) in healthy children in the 3 kindergartens(group B).</p

Primers used in the present study.

<p>Primers used in the present study.</p

Characteristics of infants aged 0–2 years with and without <i>C</i>. <i>difficile</i>.

<p>Characteristics of infants aged 0–2 years with and without <i>C</i>. <i>difficile</i>.</p