AUTHOR=Wu Xiufeng , Zhan Fuguo , Zhang Jiawei , Chen Shanjian , Yang Bin 

TITLE=Identification of hypervirulent Klebsiella pneumoniae carrying terW gene by MacConkey-potassium tellurite medium in the general population

JOURNAL=Frontiers in Public Health

VOLUME=10

YEAR=2022

URL=https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2022.946370

DOI=10.3389/fpubh.2022.946370

ISSN=2296-2565

ABSTRACT=<sec><title>Objectives</title><p>To establish a MacConkey-potassium tellurium medium-based method for selectively culturing <italic>terW</italic> gene-positive <italic>Klebsiella pneumoniae</italic> (KP), to evaluate its performance and apply it to identifying particular clonal hypervirulent KP (hvKP) strains in epidemiological surveillance.</p></sec><sec><title>Methods</title><p>The virulence genes, <italic>rmpA, iutA</italic>, and <italic>terW</italic>, were detected by PCR. The minimum inhibitory concentration of potassium tellurite of hvKP (<italic>rmpA</italic><sup>+</sup>/ <italic>iutA</italic><sup>+</sup>) and classical KP (<italic>rmpA</italic><sup>−</sup> and <italic>iutA</italic><sup>−</sup>) was determined using the agar dilution method. The MacConkey medium containing 4 μg/ml potassium tellurite was prepared and the performance in detecting <italic>terW</italic><sup>+</sup> KP was evaluated, including an agreement with PCR and positive/negative predictive value. Fecal samples from healthy volunteers in Fujian were collected and cultured in the medium, then positive strains were identified using MALDI-TOF MS, antimicrobial susceptibility was tested by Kirby-Bauer assays, and virulence genes and capsular serotype genes were tested by PCR.</p></sec><sec><title>Results</title><p>In KP isolated from clinical specimens (<italic>N</italic> = 198), the positive rate of <italic>terW</italic> was 37.9%, and the detection rate of <italic>terW</italic> in hvKP was significantly higher than that in classical KP (70.6% <italic>vs</italic> 13.3%). The potassium tellurite resistance levels of <italic>terW</italic><sup>+</sup> (<italic>N</italic> = 75) and <italic>terW</italic><sup>−</sup> (<italic>N</italic> = 55) KP were 8–128 μg/ml and &lt;1–8 μg/ml, respectively, with significant differences. KP was selectively cultured on a MacConkey medium with 4 μg/ml potassium tellurite, and its agreement with PCR was good (Kappa=0.936), and the positive and negative percent agreement and positive and negative predictive values were 100% (75/75), 92.7% (51/55), 94.9% (75/79), and 100% (51/51), respectively. The prevalence of tellurite-resistant KP was 16.7% (86/516) in fecal samples from healthy volunteers, among which the positive rate of <italic>terW</italic> was 100% (86/86). The antimicrobial resistance characteristics of <italic>terW</italic><sup>+</sup> KP showed no difference between healthy volunteers and inpatients. The most common capsular serotypes associated with high virulence were K1, K2, and K57.</p></sec><sec><title>Conclusions</title><p>The MacConkey medium containing 4 μg/ml potassium tellurite could easily select and culture <italic>terW</italic><sup>+</sup> KP in fecal samples with high sensitivity and specificity, which is a practical method for the epidemic surveillance of hvKP in the general population.</p></sec>