Genetic Platforms of blaCTX-M in Carbapenemase-Producing Strains of K. pneumoniae Isolated in Chile

Abstract

Objective: To elucidate whether the genetic platforms of blaCTX-M contribute to the phenotypes of multi-drug-resistance (MDR) in the first carbapenemase-producing K. pneumoniae strains isolated in Chile.Method: Twenty-two carbapenemase-producing K. pneumoniae strains isolated from different Chilean patients and hospitals were studied. Their genetic relatedness was assessed by PFGE and MLST. The levels of antibiotic resistance were evaluated by determining the minimum inhibitory concentration of various antimicrobials. In addition, several antibiotic resistance genes of clinical relevance in Chile were investigated. The prevalence, allelic variants, and genetic platforms of blaCTX-M were determined by PCR and sequencing.Results: Out of the 22 strains studied, 20 carry KPC, one carries NDM-1, and one carries OXA-370. The PFGE analysis showed three clades with a genetic relatedness >85%, two formed by four strains and one by eight strains. The other strains are not genetically related, and a total of 17 different pulse types were detected. Ten different STs were identified, the main ones being ST258 (five strains) and ST1161 (seven strains). The isolates presented different percentages of resistance, and 82% were resistant to all the β-lactams tested, 91% to ciprofloxacin, 73% to colistin, 59% to gentamicin, 50% to amikacin, and only 9% to tigecycline. All isolates carried blaTEM and blaSHV, whereas 71% carried aac(6′)Ib-cr, and 57% one qnr gene (A, B, C, D, or S). The blaCTX-M gene was found in 10 of the isolates (4 blaCTX-M−15 and 6 blaCTX-M−2). The characterization of the platform, in seven selected strains, revealed that the gene is associated with unusual class 1 integrons and insertion sequences such as ISCR1, ISECp1, and IS26.Conclusion: In the first carbapenemase-producing K. pneumoniae strains isolated in Chile the genetic platform of blaCTX-M−2 corresponds to an unusual class 1 integron that can be responsible for the MDR phenotype, whereas the genetic platforms of blaCTX-M−15 are associated with different IS and do not contribute to multi-drug resistance.

High prevalence of CTX-M-1 group in ESBL-producing enterobacteriaceae infection in intensive care units in southern Chile

“…13 , 14 Although the prevalence of this group has increased in the last years in Latin America, 15 , 16 the CTX-M-2 group remains the main enzyme group reported in the region. 9 , 11 , 17 Relatively little is known about the spread of these enzymes in healthcare facilities in Chile, 18 , 19 especially in critically ill patient units, because there are no nationwide surveillance programs for this bacterial resistance mechanism.…”

Introduction of NDM-1 and OXA-370 from Brazil into Chile in strains of Klebsiella pneumoniae isolated from a single patient

“…Considering that (a) NDM-1 and OXA-370 carbapenemases had not been previously found in Chile, (b) OXA-370-producing strain was detected in a patient coming from Brazil, (c) this variant of the OXA-48-group has been described only in Brazil, and (d) the similarity of ST and carbapenemase reported in K. pneumoniae isolates in both countries (Pereira et al, 2015;Aires et al, 2017;Carrasco-Anabalón et al, 2018), the aim of this study was to determine if any of the first strains producing NDM-1 and OXA-370 isolated in Chile correspond to imported cases.…”

“…In Chile, the first description of a KPC enzyme was in 2012 in a K. pneumoniae strain isolated from a patient coming from Italy (Cifuentes et al, 2012). Subsequently, in May 2014 two strains of carbapenemase-producing K. pneumoniae were isolated in a same hospital in Santiago de Chile: strain UC358, an OXA-370 producer, and strain UC361, a NDM-1 producer (Carrasco-Anabalón et al, 2018). Strain UC358 was isolated from a patient arriving from Brazil with prolonged hospitalizations in Rio de Janeiro, whereas strain UC361 was isolated from a patient with no history of travel abroad.…”

“…Eight K. pneumoniae strains were included in the study, the two isolated in Chile plus six clinical strains from Rio de Janeiro, Brazil, producing the same carbapenemases and belonging to the same ST as the Chilean strains (three OXA-370 positive isolated in 2013 and three NDM-1 positive isolated in 2014). Furthermore, the strains carry similar determinants of antibiotic resistance such as bla CTX-M, qnrB, aac(6 0 )Ib-cr (Pereira et al, 2015;Aires et al, 2017;Carrasco-Anabalón et al, 2018). The genetic relatedness between the strains producing the same type of carbapenemases was assessed by pulsed-field gel electrophoresis (PFGE) using Xbal endonuclease (Thermo Fisher Scientific Inc., Waltham, USA).…”

“…Dendrogram were constructed with BioNumerics software version 6.6 (Maths, Kortrijk, Belgium), using the UPGMA algorithm and Dice coefficient and tolerance and optimization values of 1.5. Isolates with 85% similarity were considered as genetically related (Pereira et al, 2015;Aires et al, 2017;Carrasco-Anabalón et al, 2018).…”