Identification of hypervirulent Klebsiella pneumoniae isolates using the string test in combination with Galleria mellonella infectivity

Distinguishing between hypervirulent Klebsiella pneumoniae (hvKp) and classical Klebsiella pneumoniae (cKp) is a challenge to clinical laboratories. The aim of this study was to determine the practicability of combining the G. mellonella killing assay with a string test to differentiate hvKp from cKp. One hundred and three clinical K. pneumoniae isolates were collected. PCR amplification and wzi sequencing were used to determine the capsular serotype. Virulence genes allS, iro, iuc, and rmpA2, used frequently to identify hvKp, were detected by PCR. The virulence of K. pneumoniae isolates was evaluated using the following assays in parallel: molecular markers detection, G. mellonella killing assay alone, G. mellonella killing assay combined with the string test, and mouse infection. The results showed that the sensitivity, specificity, positive predictive value, and negative predictive value of combining the G. mellonella killing assay with a string test were 95.56%, 94.83%, 93.48%, and 96.49%, respectively, compared with mouse infection used as a positive reference. These values were significantly greater than those obtained using the G. mellonella killing assay only. The sensitivity, specificity, positive predictive value, and negative predictive value of allS, iro, iuc, and rmpA2 were greater than 77.78%, but less than combining the G. mellonella killing assay and string test. G. mellonella killing assay used in conjugation with the string test is a relatively simple and accurate method to assess K. pneumoniae virulence and differentiate between hvKp and cKp.