Background: Klebsiella pneumoniae is a common cause of nosocomial infections. Antibiotic resistance and ability to form biofilm, as two key virulence factors of K. pneumoniae, are involved in the persistence of infections. The purpose of this study was to investigate the correlation between antimicrobial resistance and biofilm formation capability among K. pneumoniae strains isolated from hospitalized patients in Iran. Methods: Over a 10-month period, a total of 100 non-duplicate K. pneumoniae strains were collected. Antibiotic susceptibility was determined by Kirby–Bauer disk diffusion method according to CLSI. Biofilm production was assessed by tissue culture plate method. Finally, polymerase chain reaction was conducted to detect four families of carbapenemase: bla_IMP, bla_VIM, bla_NDM, bla_OXA−48; biofilm formation associated genes: treC, wza, luxS; and K. pneumoniae confirming gene: rpoB. Results: Most of the isolates were resistant to trimethoprim-sulfamethoxazole (52 %), cefotaxime (51 %), cefepime (43 %), and ceftriaxone (43 %). Among all the 100 isolates, 67 were multidrug-resistant (MDR), and 11 were extensively drug-resistant (XDR). The prevalence of the bla_VIM, bla_IMP, bla_NDM, and bla_OXA−48 genes were 7 , 11 , 5 , and 28 %, respectively. The results of biofilm formation in the tissue culture plate assay indicated that 75 (75 %) strains could produce biofilm and only 25 (25 %) isolates were not able to form biofilm. Among these isolates, 25 % formed fully established biofilms, 19 % were categorized as moderately biofilm-producing, 31 % formed weak biofilms, and 25 % were non-biofilm-producers. The antimicrobial resistance among biofilm former strains was found to be significantly higher than that of non-biofilm former strains (p < 0.05). Molecular distribution of biofilm formation genes revealed that 98 , 96 , and 34 % of the isolates carried luxS, treC, and wza genes, respectively. Conclusions: The rise of antibiotic resistance among biofilm-producer strains demonstrates a serious concern about limited treatment options in the hospital settings. All of the data suggest that fundamental actions and introduction of novel strategies for controlling of K. pneumoniae biofilm-related infections is essential.

Background: Staphylococcus aureus is one of the most important causative agents in community- and hospital-acquired infections. Aminoglycosides are powerful bactericidal drugs that are often used in combination with beta-lactams or glycopeptides to treat staphylococcal infections. Objectives: The main objective of the present study was to determine the prevalence of aminoglycoside resistance among methicillin-resistant Staphylococcus aureus (MRSA) isolates in hospitalized patients in Sari and Tehran, Iran. Methods: In this study, 174 MRSA strains isolated from different clinical samples, such as blood, sputum, tracheal exudates, bronchus, pleura, urine, wounds, and catheters, were collected from hospitalized patients in Tehran and Sari during 2014. Antibiotic susceptibility testing was performed against nine antibiotics with the Kirby-Bauer disk diffusion method according to CLSI guidelines. The MRSA strains were examined with oxacillin and cefoxitin disks. MRSA was then validated by detection of the mecA gene. PCR was used to evaluate the prevalence of the aminoglycoside-resistance genes aac (6’)-Ie/aph (2”), aph (3’)-IIIa, and ant (4’) among the MRSA isolates. Results: The results of drug susceptibility testing showed that the highest rate of resistance was against erythromycin in Tehran (84.4%) and gentamicin (71.7%) in Sari. All isolates were sensitive to vancomycin, and all strains harbored the mecA gene. The aac (6’)-Ie/aph (2”), aph (3’)-IIIa, and ant (4’)-Ia genes were detected among 134 (77%), 119 (68.4%), and 122 (70.1%) of the isolates, respectively. Conclusions: The present study showed a high prevalence of aminoglycoside-resistance genes among MRSA isolates in two cities in Iran. Keywords: Aminoglycosides; Drug Resistance; Methicillin-Resistant Staphylococcus aureus

In recent years, the prevalence of resistance to aminoglycosides among clinical isolates of Pseudomonas aeruginosa is increasing. The aim of this study was to investigate the role of aminoglycoside‐modifying enzymes (AMEs) in resistance to aminoglycosides in clinical isolates of P. aeruginosa. The clinical isolates were collected from different hospitals. Disk agar diffusion test was used to determine the antimicrobial resistance pattern of the clinical isolates, and the minimum inhibitory concentration of aminoglycosides was detected by microbroth dilution method. The PCR was performed for discovery of aminoglycoside‐modifying enzyme‐encoding genes. Among 100 screened isolates, 43 (43%) isolates were resistant to at least one tested aminoglycosides. However, 13 (13%) isolates were resistant to all tested aminoglycosides and 37 isolates were detected as multidrug resistant (MDR). The resistance rates of P. aeruginosa isolates against tested antibiotics were as follows: ciprofloxacin (41%), piperacillin‐tazobactam (12%), cefepime (32%), piperacillin (26%), and imipenem (31%). However, according to the MIC method, 13%, 32%, 33%, and 37% of the isolates were resistant to amikacin, gentamicin, tobramycin, and netilmicin, respectively. The PCR results showed that AAC(6 ^′ )-Ib was the most commonly (26/43, 60.4%) identified AME‐encoding gene followed by AAC(6 ^′ )-IIa (41.86%), APH(3 ^′ )-IIb (34.8%), ANT(3 ^″ )-Ia (18.6), ANT(2 ^″ )-Ia (13.95%), and APH(3 ^″ )-Ib (2.32%). However, APH(3 ^′ )-Ib was not found in any of the studied isolates. The high prevalence of AME‐encoding genes among aminoglycoside‐resistant P. aeruginosa isolates in this area indicated the important role of AMEs in resistance to these antibiotics similar to most studies worldwide. Due to the transmission possibility of these genes between the Gram‐negative bacteria, we need to control the prescription of aminoglycosides in hospitals.

Ethanol, methanol, chloroform, petroleum ether and aqueous extracts of leaves ofParrotia persica were evaluated for antibacterial activity. The zone of inhibition varied from 13 to 22 mm. The highest inhibit-tion was obtained with methanol and ethanol. Chloroform and petroleum ether extracts did not show any activity. The minimal inhibitory concentration (MIC) value of the methanol extract for the test bacteria ranged between 3.12 and 6.25 mg/ml and that of ethanol extract ranged between 6.25 and 12.5 mg/ml. The results scientifically validate the use of this plant in the traditional medicine of Iran. Key words: Parrotia persica, antibacterial activity, methanol extract, traditional medicine.

Introduction: Metallo-β-lactamases (MBLs) play a major role in the resistance of Pseudomonas aeruginosa to carbapenems. We investigated the antibiotic susceptibility patterns and frequency of MBLs genes (blaIMP and blaSPM) in carbapenem-resistant P. aeruginosa clinical isolates in Sari, Iran. Materials and Methods: The isolates were identified using standard microbiological tests, and their antibiotic susceptibility pattern was determined by the disk agar diffusion method according CLSI criteria. Phenotypic identification of MBL-producing strains assessed by the combined disk test (CDT). Then, polymerase chain reaction (PCR) was used to detect the presence of blaIMP and blaSPM genes. Results: The highest and lowest levels of antibiotic resistance were observed against gentamicin (40%) and piperacillin-tazobactam (13%), respectively. Besides, 40 isolates (40%) had the multi-drug resistant (MDR) phenotype, while 5 (12.5%) MDR isolates were resistant to all antibiotics tested. The results of the CDT showed that among 43 carbapenem non-susceptible clinical isolates of P. aeruginosa, 33 (76.74%) isolates were MBL-producing strains. Also, the frequency of the blaIMP gene among 43 carbapenem non susceptible isolates was determined to be 6.97%, while none of these isolates carried the blaSPM gene. Conclusion: Due to the high prevalence of carbapenem-resistant and MDR P. aeruginosa in this study, routine antibiotic susceptibility testing and phenotypic identification of carbapenemase production by this bacterium are necessary for the proper selection of antibiotics.