AUTHOR=Azam Mudsser , Gaind Rajni , Yadav Gulshan , Sharma Amit , Upmanyu Kirti , Jain Manisha , Singh Ruchi 

TITLE=Colistin Resistance Among Multiple Sequence Types of Klebsiella pneumoniae Is Associated With Diverse Resistance Mechanisms: A Report From India

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.609840

DOI=10.3389/fmicb.2021.609840

ISSN=1664-302X

ABSTRACT=<p><bold>Background:</bold> The resistance to colistin and carbapenems in <italic>Klebsiella pneumoniae</italic> infections have been associated with increased morbidity and mortality worldwide. A retrospective observational study was conducted to determine the prevalence and molecular events contributing to colistin resistance.</p><p><bold>Methods:</bold> Clinical samples were screened for colistin resistance and underlying mechanisms were studied by PCR-based amplification and sequence analysis of genes of two-component regulatory system (<italic>phoPQ</italic> and <italic>pmrAB</italic>), regulatory transmembrane protein-coding <italic>mgrB</italic>, and mobilized colistin resistance genes (<italic>mcr-1-8</italic>). Gene expression of <italic>pmrC</italic> and <italic>pmrK</italic> was analyzed by qRT-PCR, and the genetic relationship was assessed by MLST. The putative effect of amino-acid substitutions was predicted by a combination of bioinformatics tools.</p><p><bold>Results:</bold> Of 335 <italic>Klebsiella</italic> spp. screened, 11 (3.2%) were identified as colistin-resistant (MIC range, 8 to &gt;128 μg/ml). <italic>K. pneumoniae</italic> isolates belonged to clonal complex-11 (CC11) with sequence types (STs): 14, 16, 43, 54, 147 and 395, whereby four isolates conferred three novel STs (3986, 3987 and 3988) profiles. Sequence analysis revealed non-synonymous potentially deleterious mutations in <italic>phoP</italic> (T151A), <italic>phoQ</italic> (del87–90, del263–264, L30Q, and A351D), <italic>pmrA</italic> (G53S), <italic>pmrB</italic> (D150V, T157P, L237R, G250C, A252G, R315P, and Q331H), and <italic>mgrB</italic> (C28G) genes. The <italic>mgrB</italic> gene in three strains was disrupted by insertion sequences encoding IS<italic>1</italic>-like and IS<italic>5</italic>/IS<italic>1182</italic> family-like transposase genes. All 11 isolates showed an elevation in the transcription level of <italic>pmrC</italic> gene. Mobilized colistin-resistance (<italic>mcr</italic>) genes were not detected. All but one of the colistin-resistant isolates was also resistant to carbapenems; β-lactamase genes <italic>bla<sub>NDM-1-like</sub></italic>, <italic>bla<sub>OXA-48-like</sub></italic>, and <italic>bla<sub>CTX-M-like</sub></italic> were detected in eight, five, and nine isolates, respectively.</p><p><bold>Conclusion:</bold> All the studied colistin- and carbapenem-resistant <italic>K. pneumoniae</italic> isolates were genetically distinct, and various mechanisms of colistin resistance were detected, indicating its spontaneous emergence in this bacterial species.</p>