Katayoon Nofouzi , Alaleh Rakhshanpoor, Reza Asadpour,
Volume 11, Issue 4 (7-2017)
Abstract
ABSTRACT
Background and Objectives: Mastitis caused by Staphylococcus aureus is a widely distributed disease in cattle, goats and sheep. The infection is often subclinical in cattle, leading to reduced milk production and quality, but acute catarrhal or even gangrenous inflammation may also occur. The aim of this study was to investigate resistance of S. aureus isolates from bovine subclinical mastitis to a number of antibiotics.
Methods: Milk samples were collected from 120 cows in different regions of Tabriz, Iran. Milk samples were cultured and bacteriological identification was performed. Antimicrobial susceptibility of the isolates was assessed by determining minimum inhibitory concentration. Plasmid DNA was extracted by an alkaline lysis method.
Results: The highest frequency of resistance was observed against gentamicin (100%) and β- lactam antibiotics including amoxicillin (96%), ampicillin (40%) and penicillin (96%). The isolates mostly contained large plasmids, which might harbor acquired antibiotic resistance.
Conclusion: The results confirm the high frequency of antibiotic resistance among staphylococci isolated from bovine subclinical mastitis.
Keywords: Anti-infective Agents, Cattle, Staphylococcus Aureus, Mastitis, Plasmids.
Leila Asadpour, Mohammad Moradi Bazghaleh,
Volume 17, Issue 3 (5-2023)
Abstract
Background: Fluoroquinolones are a class of broad-spectrum antimicrobials typically used for the treatment of lower urinary tract infections. We aimed to determine the frequency of quinolone resistance genes in Klebsiella pneumoniae isolates from urinary tract infections in Guilan Province, Iran.
Methods: The resistance of 114 clinical isolates of K. pneumoniae to common fluoroquinolones and the minimum inhibitory concentration of ciprofloxacin were determined by disk diffusion and broth microdilution methods, respectively. Frequency of five plasmid-mediated quinolone resistance (PMQR) genes including qnrA, qnrB, qnrS, qepA, and aac (6')-Ib-cr was determined by PCR.
Results. According to phenotypic assays, 60 isolates (52.6%) were resistant to at least one quinolone compound, 42 isolates (36.8%) were resistant to all tested quinolones, and 28 isolates (24.6%) showed a high level of ciprofloxacin resistance. In addition, aac(6')-Ib-cr was the most common PMQR gene (𝑛 = 44), followed by qnrS (𝑛 = 32), and qnrB (𝑛 = 21).
Conclusion: The possible dissemination of PMQR genes poses a serious threat to the management of infections by resistant Klebsiella pneumoniae.
Mehdi Bozorgi Mazandarani, Mohammad Kargar, Farshid Kafilzadeh,
Volume 20, Issue 2 (6-2026)
Abstract
Background: The emergence of fluoroquinolones (FQ) resistance in the Escherichia coli (E. coli) sequence type 131 (ST131) has become a major challenge in the management of urinary tract infections (UTI). Chromosomal mutations and plasmid-mediated quinolone resistance (PMQR) determinants play an important role in the FQ resistance.
Methods: This cross-sectional study was conducted in 2020 on 300 urine samples. aimed to investigate the prevalence of the chromosomal mutations, the PMQR genes including qnr, aac (6′)-Ib-cr, and efflux pumps among the FQ-resistant ST131 and non-ST131 E. coli causing UTI. Initially, the ST131 clone was detected using allele-specific PCR and confirmed by multilocus sequence typing.
Results: Among 95 FQ-resistant E. coli isolates, 30% (n=29/95) as belonging to the ST131 clone. The most frequently detected PMQR genes in FQ-resistant isolates were aac(6)’-lb-cr and qnrS. However, statistical analysis revealed a stronger association between aac(6ʹ)-Ib-cr and the ST131 clone (62%; p<0.03). The oqxA gene was the most prevalent efflux pump gene observed in both ST131 (n=11; 38%) and non-ST131 (n=16; 24%) isolates. Analysis of the gyrA and parC genes revealed significantly higher in ST131 compared to non-ST131. Double mutations, S80I+E84V, were significantly more prevalent in both gyrA (76% ST131 vs. 43% non-ST131; p=0.004) and parC (55% ST131 vs. 26% non-ST131; p=0.002). High-level resistance (MIC ≥32 μg/mL) observed in 96.6% (n=28/29) of ST131 isolates compared to 65% (n=43/66) of non-ST131 isolates.
Conclusion: The double mutations confer high level resistance to FQs in ST131 clone. These findings on resistance mechanisms can guide infection control strategies.
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