Virulence Factors And Antimicrobial Susceptibility Characteristics Of Klebsiella Pneumoniae In Intestinal Tract From Various Populations

Objective:To investigate the carriage rate, virulence, drug resistance and molecular epidemiology characteristics of Klebsiella pneumoniae in intestinal tract from hospitalized patients, diarrheal outpatients and healthy population.Methods:Fresh stool samples were collected and inoculated onto medium. Identification was conducted by Matrix-assisted Laser Desorption/Ionization Time-of-flight Mass Spectrometry (MALDI-TOF MS) Vitek MS. String test was performed to detect hypermucoviscous phenotype, and Kirby-Bauer disk diffusion method was used for antimicrobial susceptibility testing. Capsular serotypes (including K1, K2, K5, K20, K54and K57) and associated virulence factors (including wcaG, rmpA, magA and aerobactin) were detected with specific primers. Genes encoding for spectrum beta-lactamases, extended-spectrum beta-lactamases, plasmid-mediated AmpC beta-lactamases and carbapenemases were detected by PCR. Seven housekeeping genes (gapA, infB, gpi, PhoE, rpoB and tonB) were amplified and sequenced for Multilocus Sequence Typing (MLST) analysis.Results:A total of141K. pneumoniae isolates were collected from hospitalized patients (54/125, carriage rate of43.2%), diarrheal outpatients (44/257,17.1%), and healthy population (43/141,30.5%). Forty-nine isolates were positive for virulence genes, of which,35demonstrated hypermucoviscous phenotype. Fourteen isolates (14/141,9.9%) were serotype K1,15(15/141,10.6%) were serotype K2, while K20and K57were less frequently detected, K54was not detected. Aerobactin was most frequently detected with the detection rate of30.5%, followed by rmpA (19.9%), wcaG (12.1%) and magA (9.9%). K. pneumoniae isolates from healthy population possessed the highest detection rate of virulence, and the detection rates of K1/K2serotype, wcaG, rmpA, magA and aerobactin were significantly higher than those from hospitalized patients, however, healthy population derived isolates were susceptible to most drugs. Isolates from hospitalized patients had the highest resistance rate with over30%resistant to cephalosporin, and22.2%resistant to carbapenem. K. pneumoniae isolates without virulence were more resistant to antimicrobial drugs than those with virulence, additionally,3isolates were identified for the coexistence of virulence and resistance genes (magA+Kl+blasnv-2, aerobactin+blaTEM-1+blaKPC-2, aerobactin+wcaG+blaCTX-M-14+blaSHV-1).Differences were observed among sequence types (ST) of isolates with virulence and without virulence, ST of those with virulence were more centralized, ST23and ST86were the main ST. In addition, isolates belonging to ST23were serotype Kl, while those belonging to ST65and ST86were serotype K2.Conclusions:Hospitalized patients had the highest carriage rate of K. pneumoniae isolates, and those isolates were less virulent but possessed the highest resistance rate. Healthy population carried higher proportion of virulent isolates. Virulent isolates were more susceptible to antimicrobial drugs than those without virulence. Particular ST were associated with virulence. The healthy population carried the virulent isolates which belonged to dominant clones in pyogenic live abscesses patients, indicating that invasive isolates infecting the liver were from intestinal tract.