Purpose: Multidrug resistant (MDR) Klebsiella pneumoniae (Kp)
is a worldwide concern worsened by colistin resistance emergence.
In this study, molecular epidemiology of clinical MDR Kp strains is described, assessing clonal relationships and resistance genes
profiles. Prevalence of Extended-Spectrum Beta-Lactamase (ESBL)
blaCTX-M, blaTEM and blaSHV genes was evaluated, as well as that
associated to carbapenems (blaKPC, blaGES, blaVIM, blaIMP, blaNDM,
blaOXA-48) and colistin resistance (mcr-1,2,3,4 and mgrB).
Methods & Materials: Twenty-six Kp cultures were collected
from âŁœA.Cardarelli⣞ hospital in Molise Region (Central Italy),
57.7% from Intensive Care Unit (ICU). The Minimum Inhibitory Concentration (MIC) was assessed by BD Phoenixâ„¢. Genotyping was
achieved through Pulsed-Field Gel Electrophoresis (PFGE) withXbaI
and MultiLocus Sequence Typing (MLST). PCRs for resistance genes
detection and mgrB sequencing were performed.
Results: Most (n = 20, 77%) strains were carbapenems resistant
(imipenem, meropenem, ertapenem), and 53% (n = 14) to colistin.
A higher prevalence of blaKPC (100%) and blaSHV (96.2%) was found
compared with blaTEM (88.5%), blaVIM (69.0%) and blaCTX-M (7.7%).
While none colistin-resistant (col-R) strain carried mcr-1,2,3,4 variants, 42.8% (n = 6) had an Insertion Sequence (IS) in mgrB, identified
as IS5-like (5/14, 36%) and ISKpn14 (1/14, 7%). The prevalent
Sequence Type was ST512 (50%), followed by ST101 (38.5%) and
ST307 (11.5%). PFGE detected 12 clusters and 18 pulsotypes (95%
similarity), and was more discriminating than MLST (Simpson’s
Index 95%vs 61%). An ICU outbreak, during November 2014-January
2015, included five ST512 strains, blaTEM/blaSHV/blaVIM/blaKPC positive, and col-R due to mgrB IS5-like.
Conclusion: Molecular epidemiology study identified an outbreak caused by poor compliance with hygienic standards because
of reduced personnel during Christmas holidays. Although ST258
is the most prevalent in Italy, half strains were typed as ST512
that represents its monoallelic variant. Our results confirm the
endemic blaKPC distribution and blaTEM/blaSHV as the prevalent
ESBLs in Kp hospital outbreaks. According to epidemiological data,
plasmid mcr variants were not found in col-R strains. Conversely,
IS elements prevalence in mgrB explain resistance in about half
col-R strains, and was in line with Italian data. Further investigations are needed to identify mgrB mutations in IS negative col-R
strains
