Isolation and characterization of ESBL-producing Klebsiella pneumoniae isolates harboring β-lactamase genes

BACKGROUND AND OBJECTIVESK. pneumoniae is a gram-negative, rode shape, non-motile, encapsulated bacteria. K. pneumoniae is one of the members of the enterobacteriaceae family that can cause a wide range of nosocomial infections. This bacteria considers a dangerous bacterium due to the high prevalence of antibiotic resistance, virulence factor genes, and extended-spectrum β-lactamase (ESBL) producing. Hence, the antibiotic choice to combat ESBL positive K. pneumoniae strains can be extremely limited. Thus, routine screening of ESBL-producing K. pneumoniae in health care settings can be a proper tool in order to decreasing ESBL producing strains emergence. This study aimed to determining K. pneumoniae isolates antibiotic resistance pattern, frequency of ESBL-producing isolates, and ESBL-related genes.MATERIALS AND METHODSIn this study, clinical samples such as sputum, blood, and urine were used to isolation of desired bacteria. primary identification of isolates was performed by IMViC tests, then, amplification of specific ۱۶s rRNA by PCR method was used as final identification of isolates. The antibiotic resistance pattern was determined by disk diffusion method via ampicillin (۱۰ μg), aztreonam (۳۰ μg), amikacin (۳۰ μg), ciprofloxacin (۵ μg), tetracycline (۳۰ μg), ceftriaxone (۳۰ μg), ceftazidime (۳۰ μg), gentamicin (۱۰ μg), imipenem (۱۰ μg), and, trimethoprim-sulfamethoxazole (۱.۲۵/۲۳.۷۵ μg) disks according to CLSI guidelines. Evaluation of ESBL production was performed by the double disk synergy test (DDST) method. In the end, the prevalence of β-lactam genes including blaNDM-۱, blaSHV, blaOXA-۴۸, and blaOXA-۲۳ in ESBL-producing isolates were investigated by PCR technique.RESULTS AND DISCUSSIONIn this study, ۵۰ different K. pneumoniae isolates (۵۸% males, ۴۲% females) were identified. Compatible with other researches, the isolates of this bacterium showed high antibiotic resistance in this study. The isolates were most resistant to ampicillin (۹۸%), following tetracycline (۷۶%), amikacin (۵۸%), ceftriaxone (۵۰%), ciprofloxacin (۵۰%), gentamicin (۳۸%), trimethoprim-sulfamethoxazole (۳۰%), imipenem (۲۰%), and aztreonam (۱۰%). Every isolate was resistant to at least one group of antibiotic classes that were used in the present study, moreover, the lowest resistance was against the antibiotic aztreonam, while the highest resistance was found against ampicillin, this is compatible with the fact that K. pneumoniae strains are resistant to ampicillin intrinsically due to presence of blaSHV-۱ genes in this bacteria. In addition, the frequency of ESBL-positive isolates was determined as ۱۸%. Frequency of blaNDM-۱, blaSHV, blaOXA-۴۸, and blaOXA-۲۳ genes among ESBL-producing isolates were ۵۵.۵۵%, ۴۴.۴۴%, ۳۳.۳۳%, ۷۷.۷۷% respectively. According to other studies conducted in Iran, ESBL-producing K. pneumoniae isolates specially NDM-۱ and OXA-۴۸ harboring isolates have been increasing in the past several years, however, the frequency of these isolates in the present study was less than mentioned papers even with the study that were conducted in Tabriz city. It can be due to the factors like geographical diversity, location of study, population density, administering antibiotics, and personal hygiene, it seems investigation of the mentioned factors can be very helpful in understanding this phenomenon.CONCLUSIONIn conclusion, in this study β-lactamase harboring ESBL-positive K. pneumoniae isolates were identified, however, large-scale research including the characterization community and nosocomial infections-related Klebsiella spp. strains from different regions of Iran are required to offer information on the spread of these microorganisms in this country.

کلیدواژه ها:

Antimicrobial resistance ، K. pneumoniae ، ESBL