Plasmid-mediated colistin and fosfomycin resistance among clinical isolates of ESBL- and carbapenemase-producing Klebsiella pneumoniae in Northern Iran

The development of extensively-resistant strains of Klebsiella pneumoniae (K. pneumoniae) in the hospitals is associated with hospitalization and uncontrolled use of antibiotics. There is a scarcity in the colistin and fosfomycin resistance encoding genes rate and mechanisms in Iran. Our aim was to determine the rate of biofilm formation and fosfomycin and colistin resistance among K. pneumoniae producing ESBL and carbapenemases by detection of mcr-1, mcr-2 and fosA genes in Tehran, Iran during 2020-2021. After collecting 73 samples, the isolates were identified using biochemical tests. The antibiotic susceptibility test was implemented using disk diffusion method. The phenotypic determination of extended-spectrum beta-lactamases (ESBLs) and carbapenemase enzymes was conducted using combined disk and CARBA-NP tests, respectively. The biofilm formation was performed using microtiter tissue plate assay. The polymerase chain reaction (PCR) was performed to detect mcr-1, mcr-2 and fosA genes associated with colistin and fosfomycin resistance, respectively. The highest resistance rate was against ampicillin (97%), chloramphenicol (90%) and ciprofloxacin (87%), respectively, while the lowest resistance rate was against gentamicin (4%), amikacin (10%), and cotrimoxazole (18%). Moreover, 44 and 23 isolates were ESBL and carbapenemase producing K. pneumonia), respectively. Forty-eight isolates were strong biofilm forming K. pneumoniae and one isolate was non-biofilm producer. In the PCR test, four isolates amplified the fosA2 and one mcr-2 genes, respectively, while none of them outlined neither fosA3 nor mcr-1 genes amplification. This study demonstrated that the frequency of K. pneumoniae isolates producing ESBL and carbapenemase and also mcr-1, mcr-2 and fosA genes was low but considering facilitated spread of these genes, proper isolation and control is essential. Moreover, these strains had the ability to form biofilms in vitro which persist infections in the hospital settings.

Plasmid-mediated colistin and fosfomycin resistance among clinical isolates of ESBL- and carbapenemase-producing Klebsiella pneumoniae in Northern Iran Keywords:

Klebsiella pneumoniae , Antibiotic resistance , Colistin , ESBL , carbapenemase