International Journal of Medical Laboratory

Background and Aims: Given the importance of aminoglycoside resistance in nosocomial and community infections caused by bacterial pathogenes such as Klebsiella pneumoniae (K. pneumoniae), the aim of this study was to determine the frequency of aac (6')- Ib and aac (3)- IIa, the genes encoding aminoglycoside modifying enzymes involved in aminoglycoside resistance.
Material and Methods: A total of 100 K. pneumonia isolates were collected from hospitalized patients from April to September 2015 in Borujerd hospitals. Conventional microbiological tests were carried out to detect and confirm K. pneumonia isolates. Antibiotic susceptibility of isolates was detected by disk diffusion methods. The presence of the aac(6')-Ib and aac(3)-IIa genes which encode aminoglycoside modifying enzymes was determined by polymerase chain reaction.
Results: Among 100 K. pneumonia isolates, 34% showed resistance to gentamicin and 21% to amikacin. Resistance to both gentamicin and amikacin was detected in 18% of the isolates. Multi-resistance phenotypes were detected in 71% of the isolates. The aac (3)-IIa and aac(6ʹ)-Ib genes were found in 71% (n=24) and 5.8% (n=2) of aminoglycoside resistant isolates, respectively. Simultaneous carriage of aac (3)-IIa and aac(6ʹ)-Ib was detected in 64% (n=22) of the aminoglycoside resistant isolates.
Conclusions: The results of this study showed the presence of aac (3)-IIa genes in more than 70% of the aminoglycosides resistant K. pneumoniae strains; this may be due to the transmission of this gene through mobile genetic elements that create a high risk of rapid spread of these genes in hospitals.