1416. Assessing the potential for interspecies transmission of Clostridioides difficile on dairy farms

Background Clostridioides difficile (CD) can cause severe colitis in humans and many species of animals. It is thought that farm animals could be a reservoir for CD and that farm workers could therefore be at increased risk of colonization and infection with CD. While pigs and swine farm workers have been shown to be colonized with identical clones of CD, the zoonotic transmission of CD from animals to people has not been definitively demonstrated, and no studies have examined whether dairy farm workers, who are generally in closer contact with animals than swine farmers, are at increased risk of being colonized or infected with CD. The aim of this study was to assess whether dairy calves and farm workers harbored genetically similar isolates of CD. Methods First, we validated a glove-juice protocol to detect CD spores on the hands of farm workers. Volunteers’ hands were inoculated with serially diluted suspensions of non-toxigenic CD organisms, and hand rinsates underwent broth enrichment and anaerobic culture. Second, we collected fecal samples from 5 randomly selected dairy calves (< 7 d of age) from each of 23 farms in southeastern Pennsylvania, northern Maryland, and Delaware. We focused specifically on dairy calves, as the prevalence of CD is highest in this age group. Third, using the glove-juice protocol, we collected hand rinsates from 38 dairy farm workers who work closely with calves. Only 4 of these workers were willing to submit fecal samples along with their hand rinsates. All fecal samples and hand rinsates underwent broth enrichment and anaerobic culture for CD. Results Validation of the glove juice protocol showed that CD could be recovered successfully from all hand rinsate dilutions (up to 10-6). When applied to farm workers, this method yielded CD in none of the hand rinsates (0%, 95% CI 0.0-92.2%). CD was also not detected in any of the human fecal samples. However, CD was detected from calf fecal samples on 10 farms (43.5%, 95% CI 20.8%-80.0%). Conclusion While the zoonotic transmission of CD cannot be ruled out, our results suggest that contact with dairy animals is not likely to be associated with an increased risk of acquiring CD via the fecal-oral route. The glove-juice protocol appears to be a useful tool for studying the epidemiology of CD in populations where obtaining fecal samples is difficult. Disclosures All Authors: No reported disclosures

A comparison of GenomEra® GBS PCR and GeneXpert ® GBS PCR assays with culture of GBS performed with and without broth pre-enrichment

This study was designed to compare the performance of GeneXpert® and GenomEra® group B streptococcus (GBS) PCR assays, held up against standard culture of GBS performed with and without broth pre-enrichment. In Denmark, the strategy for preventing early onset GBS infection (EOGBS) is risk factor based. Three hundred and sixty six women fulfilling one or more of the criteria for presence of risk factors for EOGBS were prospectively included. Rectovaginal swab samples were taken intrapartum and tested bed-site by the GenomEra® and the GeneXpert® GBS PCR assays and cultured at the microbiology laboratory using Granada agar plates with and without prior growth of sampling material in selective enrichment broth. Among 366 participants tested intrapartum, 99 were GBS-positive by culture, 95 by GenomEra, and 95 by GeneXpert. Compared with culture, the GenomEra and the GeneXpert performed with a sensitivity of 91.8% and 91.7% and a specificity of 98.1% and 97.3%, respectively. A combined reference standard was established by defining true positives as either culture-positive samples or culture-negative samples where both the GeneXpert and the GenomEra GBS PCR assays were positive. Using this, the sensitivity increased to 92.2% and the specificity to 99.6% for GenomEra and to 92.0% and 96.8% for GeneXpert. The use of selective broth enrichment found only three additional GBS culture-positive samples. The performance of the two PCR methods examined was very similar and close to the findings by culture, and both PCR assays are thus applicable as rapid intrapartum bed-site tests.

Assessing the intestinal carriage rates of vancomycin-resistant enterococci (VRE) at a tertiary care hospital in Hungary

Excessive use of antibiotics contributes to the selection of resistant bacteria and intestinal colonization with multiresistant pathogens poses a risk factor for subsequent infections. The present study assessed vancomycin-resistant enterococci (VRE) carriage rates in patients admitted to our tertiary care hospital. Stool samples sent for routine culturing were screened with vancomycin containing solid or broth enrichment media. VRE isolates were identified with matrix-assisted laser desorption/ionization-time of flight mass spectrometry and antibiotic susceptibilities were tested by E-test. Vancomycin resistance genes were detected by polymerase chain reaction. Medical records of carriers were examined for suspected risk factors for colonization. Altogether 3025 stool specimens were analyzed. Solid media identified a VRE carriage rate of 2.2% while broth enrichment detected 5.8%. Seventy percent of the isolates were Enterococcus faecium. VanB genotype was detected in 38.2%, VanA in 37.3%, VanC1 in 22.6%, and VanC2 in 1.9%. All VRE were sensitive to linezolid, daptomycin, and tigecycline. Collective risk factors for carriage were diabetes, normal flora absence, Clostridioides difficile positivity, longer hospital stay, and advanced age. 78.5% of the carriers received antibiotic therapy which was metronidazole in most cases (47.3%). We recommend regular screening of risk groups such as patients with diabetes, history of recent hospitalization, or former C. difficile infection as an imperative step for preventing VRE dissemination.

Comparing the Yield of Staphylococcus aureus Recovery with Static versus Agitated Broth Incubation

Given the lack of standardization of methodologies for microbial recovery from built environments, we sought to compare the yield of Staphylococcus aureus with a broth enrichment method when incubated in agitated versus static conditions. Five unique strains of S. aureus at five different concentrations were cultured to compare direct plating, agitated broth enrichment, and static broth enrichment culture methods. All samples were incubated at 35° in ambient air. The lowest concentration recovered across three replicates and five strains did not differ between culture methods (Fisher’s exact test, p=0.50); notably, recovery of S. aureus was equivalent between static and agitated broth incubation. When broth enrichment was used (both static and agitated), the burden of S. aureus growth was higher (by semiquantitative assessment of 4-quadrant streaking) compared to the direct plating culture method. Optimizing strategies for microbial recovery is essential, particularly in areas of lower biomass, given the paucity of research concerning microbial communities of built environments. The results of this study, in conjunction with other experiments investigating microbiomes of built environments, can help inform protocols for standardizing culturing methods within built environments.