Colistin resistance in Enterobacter spp. isolates in Korea

Abstract

We investigated the colistin resistance rate among 356 Enterobacter spp. clinical isolates from eight hospitals in Korea. Antibiotic susceptibility testing was performed by broth microdilution. While 51 of 213 (23.9%) Enterobacter cloacae isolates were colistin-resistant, only six of 143 (4.2%) E. aerogenes isolates showed resistance. We also identified the skip well phenotype in eight E. cloacae and three E. aerogenes isolates. Multilocus sequence typing for E. cloacae and randomly amplified polymorphic DNA analysis and enterobacterial repetitive intergenic consensus PCR for E. aerogenes revealed that clonal spreading of colistin-resistant and skip well Enterobacter spp. isolates had not occurred. In vitro time-kill assays were performed with three colistin-resistant, three skip well, and two colistin-susceptible isolates of E. cloacae and E. aerogenes. Inconsistent results were observed among isolates with skip well phenotypes; while some were eradicated by 2 mg/L colistin, others were not. This suggests that skip well isolates have differentiated into different categories. As the high rates of colistin resistance in E. cloacae detected are of clinical concern, continuous monitoring is warranted. In addition, the clinical implications and mechanisms of the skip well phenotype should be investigated to ensure the appropriate use of colistin against Enterobacter infections.

In vitro Activity of Pentamidine Alone and in Combination With Aminoglycosides, Tigecycline, Rifampicin, and Doripenem Against Clinical Strains of Carbapenemase-Producing and/or Colistin-Resistant Enterobacteriaceae

“…However, the appearance of colistin-resistant strains has risen dramatically in the last decade due to antibiotic pressure in both human treatment and its use in agriculture (Kempf et al, 2016 ; Olaitan et al, 2016 ). In a recently published study (Hong et al, 2018 ), the in vitro activity of colistin was analyzed against 356 clinical strains of Enterobacter spp. from eight Korean hospitals, founding that 23.9 and 4.2% of E. cloacae and E. aerogenes strains, respectively, were resistant to colistin.…”

Identification and antimicrobial susceptibilities of Enterobacter species isolated from clinical specimen in southeastern Turkey from 2015 to 2017

“…1 Among 6 colistin-resistant E. aerogenes isolates; meropenem, cefepime, gentamicin, ciprofloxacin, ceftazidime and trimethoprim/sulfomethoxazole resistant rates were 16.7% (1 isolate), 16.7% (1 isolate), 50%(3 isolates), 50%(3 isolates), 83.3%(5 isolates) and 83.3%(5 isolates), respectively. 1 In two articles published in 2016, researchers reported that colistin has failed in some treatments due to colistin resistance; E.cloacae and E.aerogenes species as opportunistic pathogens that can cause serious problems for human health. 22,23 In a study conducted in Brazil in 2018, the researchers evaluated the resistance profiles of 14 Enterobacter isolates ( 8 E.cloacae and 6 E.aerogenes) to different antibiotics.…”

“…These facultative anaerobe Gram negative rods may cause opportunistic infections especially in immunocompromised patients. 1 Hoffman et al described E.cloacae, E.asburiae, E.hormaechei and E.kobei species as ''E.cloacae complex'' in 2005. [2][3][4][5] Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumanni, Pseudomonas aeruginosa ve Enterobacter spp.…”

Two Distinct Genotypes of KPC-2-Producing Klebsiella pneumoniae Isolates from South Korea

“…The carbapenemase genes bla KPC , bla IMP , bla VIM , bla NDM , bla SPM , and bla SIM and an extended spectrum β-lactamase gene bla CTX-M were detected by PCR amplification and Sanger sequencing using previously described primers [ 18 , 19 , 20 ]. The presence of mcr , a plasmid-borne colistin resistance gene, was also determined by PCR [ 21 ].…”