Occurrence and mechanisms of amikacin resistance and its association with β-lactamases in Pseudomonas aeruginosa: a Korean nationwide study

Abstract

In Korea, the amikacin resistance rate in P. aeruginosa was high (22%), and it varied among provinces (3.8% to 40%). Four types of AG-modifying enzyme genes [aph(3')-VI, ant(2'')-I, aac(6')-I and aac(3)-II/VI] were found in 48 isolates. Thirty-six strains harboured two or more types of enzymes, of which a combination of aph(3')-VI and ant(2'')-I was the most frequent (24/36 isolates, 66.7%). None harboured aac(3)-I, aac(3)-III/IV, aac(6')-II, ant(4')-II, rmtA, rmtB, rmtC or armA. Forty-two isolates co-harboured beta-lactamase genes (mostly bla(OXA-10)). A class 1 integron was detected in all but one, and all the ant(2'')-I and 26/29 bla(OXA-10) were found in it. In contrast, aph(3')-VI was not found to be associated with the class 1 integron. Considering the possibility of co-selection and dissemination, constant monitoring of resistance evolution is necessary.

Occurrence of aminoglycoside-modifying enzymes genes (aac(6′)-I and ant(2′′)-I) in clinical isolates of Pseudomonas aeruginosa from Southwest Nigeria.

“…It has been previously reported that the occurrence of these combination of enzymes varied by geographic regions and among hospitals 9 , this suggests a reason for differences in our result and other findings. Consistent with other previous studies that reported co-habitation of one or more AME genes in a single P. aeruginosa isolates 9,15,19 , 12.9% of P. aeruginosa isolates in this study harbours both aac(6′)-I and ant(2′′)-I genes and they were distributed among the selected hospitals (Table 1). According to previous reports 8,20,21 , the presence of aac(6′)-I gene in an organism is significant for amikacin resistance while ant(2′′)-I is responsible for the inactivation of gentamicin.…”

“…Out of the three classes of AMES (aph, aac and ant) investigated in this study, only aac(6′)-I and ant(2′′)-I genes were detected while aac (6′) -I was the most frequent. This is in line with previous studies conducted in Belgium, Greece, France and India, where aac(6′)-I was the most frequently detected AME genes 9,18,20 but is in sharp contrast to studies conducted in USA, Korea and Iran where the most common AME gene detected were aac(6′)-II and aph (3′)-IV 9,15,19 . It has been previously reported that the occurrence of these combination of enzymes varied by geographic regions and among hospitals 9 , this suggests a reason for differences in our result and other findings.…”

“…The DNA template obtained from the supernatant of a boiled extracts of P. aeruginosa cells was used for PCR amplification as described previously 14,15 . PCR amplification was carried out in a volume of 25µl containing the following: 1 -2 µl DNA templates, 20pM of each primer, 250 µM of dNTP, 10mM Tris-HCl (pH8.3), 50mM KCl, 2.5mM MgCl2 and 1.5U of Taq DNA polymerase (Promega Corporation, Madison, USA), using various annealing conditions for each primer set for the detection of various AME genes (aac(3)-I, aac(3)-II, aac(6′)-I, aac(6′)-II, ant(2′′)-I and aph(3′)-VI) 15 investigated in this study.…”

“…, 87.3% from Korea 15 , 43.5% from India 18 , and 54% from Iran 19 . Out of the three classes of AMES (aph, aac and ant) investigated in this study, only aac(6′)-I and ant(2′′)-I genes were detected while aac (6′) -I was the most frequent.…”

Efflux pump genes and antimicrobial resistance of Pseudomonas aeruginosa strains isolated from lower respiratory tract infections acquired in an intensive care unit

“…16 In our study, the aminoglycoside resistance rates in P. aeruginosa were lower than that in the study from Korea. 25 Aminoglycoside resistance arises more frequently via enzymatic modification of the aminoglycosides, and less frequently via mexXY-oprM efflux systems. 16 So no relation was found between the presence of mexX gene and aminoglycosides (amikacin, gentamicin and tobramycin).…”