In vitro activities of colistin, imipenem and ceftazidime against drug-resistant Pseudomonas aeruginosa and Acinetobacter baumannii isolates in the south of Iran

Abstract

Objective The present study aimed to determine in vitro activity of colistin and other agents against drug-resistant isolates of Pseudomonas aeruginosa and Acinetobacter baumannii . Results This in vitro study performed on a collection of non-fermenting Gram-negative bacilli (NFB) consist of 18 A. baumannii and 21 P. aeruginosa isolates. Non-duplicated isolates (one per patient) were isolated from blood, endotracheal tube and sputum samples of hospitalized patients in the south of Iran. The minimum inhibitory concentrations (MICs) of each isolate was determined using Epsilometer (E)-test strips containing colistin, imipenem, and ceftazidime. In overall, all A. baumannii isolates were non-susceptible to imipenem and ceftazidime. In contrast, all isolates were susceptible to colistin with MIC50 and MIC90 of 0.75/1.5 µg/mL, respectively. Antibiotic susceptibility results showed that 81% and 23.8% of P. aeruginosa isolates were susceptible to ceftazidime and imipenem, respectively. While, all of the P. aeruginosa isolates were susceptible to colistin with MIC50 and MIC90 of 0.5/1 µg/mL, respectively. In summary, colistin showed the promising in vitro activity against drug-resistant strains of two clinically important NFB in our region. However, investigation on a larger collection of drug-resistant strains demands to support these observations in the near future.

Antimicrobial Activity of Colistin Against Contemporary (2015 – 2017) P. aeruginosa and A. baumannii Isolates From a Chinese Surveillance Program

“…only in the range 19.2 -33.0% and for P. aeruginosa 55.6 -63.1% to ciprofloxacin, cefepime and piperacillintazobactam, but 83.4% to amikacin, indicating that for all tested antimicrobial agents other than colistin, at best only amikacin might serve as an empiric treatment option for P. aeruginosa infections. In contrast, overall susceptibility rates to colistin were 94.6 and 95.7% for P. aeruginosa and A. baumannii in isolates obtained from IAIs, UTIs and RTIs in the present study, which is in agreement with previously reported high susceptibility rates of both species in other countries (Ece et al, 2014;Malekzadegan et al, 2019). In addition, there was no visible trend of decreasing colistin susceptibilities toward 2017 in the different hospital departments and Chinese regions, except for a slight decrease in east Jiangzhe.…”

In vitro activity of colistin against multidrug-resistant Acinetobacter baumannii isolates harboring blaOXA-23-like and blaOXA-24-like genes: A multicenter based study

“…Polymyxins are usually drug of choice to treat infections caused by MDR Gram-negative bacteria [12]. Previously two comparable reports were available from southern region [10,29], but our study was the first report from our region in the north of Iran. Moreover, our results are consistent with reports from CANWARD study and SENTRY program suggests that colistin remains an available option for the treatment of infection caused by CRAB since the majority of isolates were susceptible to colistin [30,31].…”

“…Limited therapeutic options to treat infections caused by these drug-resistant strains request development of new drugs or recruiting the old ones [10]. Colistin (also known as polymyxin E) is a multicomponent polypeptide antibiotic and relatively old polymyxin that achieved its antimicrobial effect by acting directly on bacterial cell membrane.…”

“…Colistin (also known as polymyxin E) is a multicomponent polypeptide antibiotic and relatively old polymyxin that achieved its antimicrobial effect by acting directly on bacterial cell membrane. [11] Currently, colistin is a reliable option for treatment of infections caused by MDR Gram-negative bacteria [10,12].…”

Detection of carbapenem resistance and virulence genes among Acinetobacter baumannii isolated from hospital environments in center of Iran

“…Multidrug-resistant Acinetobacter baumannii is an opportunistic pathogen that causes nosocomial infections [1][2][3]. Infections caused by this bacterium have a high prevalence in hospitalized and immunocompromised patients who are admitted to intensive care units [4,5]. These infections are ventilator-associated pneumonia, soft-tissue, urinary tract, and meningitis infections [6][7][8].…”