Tigecycline Resistant Klebsiella pneumoniae Isolated from Austrian River Water

Abstract

Antibiotic-resistant bacteria are spreading worldwide in medical settings but also in the environment. These resistant bacteria illustrate a major health problem in our times, and last-line antibiotics such as tigecycline represent an ultimate therapy option. Reports on tigecycline non-susceptible Enterobacteriaceae are presented with regard to medical settings but are rare with that for the environment. The aim of this study was to characterize two tigecycline non-susceptible Klebsiella pneumoniae isolates from the river Mur, and to question the resistance mechanism. The screening for chromosomal mutations revealed a deletion and a silent point mutation in one isolate and a point mutation in the other isolate all within the ramR allele. RamR acts as repressor and prevents overexpression of ramA. These mutations are likely to cause a resistant phenotype due to the overexpression of AcrAB-TolC. MLST revealed that the isolates belonged to two unrelated MLST types (ST2392 and ST2394). Both isolates only revealed resistance to tigecycline and tetracycline. This is one of the rare reports of tigecycline-resistant Klebsiella pneumoniae from surface water. The presence of two genetically different isolates suggests that the river water may bear substances that favor mutations that can lead to this efflux pump-driven resistance.

CusS-CusR Two-Component System Mediates Tigecycline Resistance in Carbapenem-Resistant Klebsiella pneumoniae

“…However, Nielsen et al (2014) reported that the IS5 insertion element increased the MIC of tigecycline by four-fold and was not dependent on the functional AcrAB-TolC efflux pump, suggesting that the AcrAB-TolC efflux pump is not the only mechanism causing tigecycline resistance. Hladicz et al (2017) reported that RamR is a repressor that prevents the overexpression of ramA; when ramR is mutated, ramA is overexpressed, leading to tigecycline resistance; this mechanism was confirmed by Li et al (2017). However, in the current study, no mutation in ramR was detected.…”

Antibiotics in Crab Ponds of Lake Guchenghu Basin, China: Occurrence, Temporal Variations, and Ecological Risks

“…As a new class of environmental contaminants, antibiotics have been the subject of numerous discussions due to their large-scale usage and long-term adverse effects [ 1 , 2 , 3 ]. Thousands of tons of antibiotics are used for therapeutic purpose or as animal growth promoters every year [ 4 , 5 , 6 ].…”

Molecular epidemiology and mechanisms of tigecycline resistance in carbapenem‐resistant Klebsiella pneumoniae isolates

“…16,19 The transcription of ramA, marA, and soxS is repressed by RamR, MarR, and SoxR, respectively. 13,26 RamA is also regulated by Lon protease. 27,28 As RamR directly represses the expression of ramA, loss-of-function mutations in ramR can cause the overexpression of ramA.…”