محمدرضا عربستانی

Due to the increased prevalence of antibiotic resistance to beta-lactam and carbapenem compounds, the identification of beta-lactamase-producing enzymes is essential for the timely treatment of such isolates. The study aimed to determine the prevalence of Metallo-β-Lactamases (MBL) and Klebsiella Pneumoniae Carbapenemase    (KPC) genes among Pseudomonas aeruginosa clinical isolates.

In this cross sectional- descriptive study a total of 97 clinical isolates were collected from hospitalized patients of Hamadan hospitals from November 2017 to May 2018. After confirmation of the isolated strains, antibiotic susceptibility of the isolates was determined by disk agar diffusion, Minimum Inhibitory Concentration (MIC) was performed for imipenem using Etest method, Combined Double-Disk Test (CDDT) and Modified Hodge test (MHT) and identification of carbapenemase genes was performed by Polymerase Chain Reaction (PCR).

The results of statistical analysis showed that the highest antibiotic resistance was to cefoxitin, 92 (94.8%), and the lowest antibiotic resistance was to piperacillin-tazobactam, 38 (39.2%). Among the carbapenem antibiotics, the highest antibiotic resistance was to imipenem 48 (49.4%). Among of 49 (50.51%) carbapenem-resistant isolates, 42 (85.71%) had positive results for MIC, 26 (53.06%) and 25 (51.02%) isolates had positive results for IMP / EDTA (CDDT) and MHT test respectively. PCR results also showed that the highest and lowest gene presence among resistant isolates was related to IMP, 20 (40.8%) and GIM gene, 6 (12.24%), respectively.

Results showed that a high percentage of P. aeruginosa isolates 49 (50.51%) were resistant to carbapenem antibiotics, and a high percentage of carbapenem-resistant isolates produced beta-lactamase genes.

Different phenotypic methods are available for identification of pseudomonas aeroginosa isolates producing carbapenemase enzymes. Carbapenem inactivation method (CIM) is a fast and inexpensive way for detection of this enzyme. The purpose of this study was to evaluate the CIM method for accurate identification of carbapenemase producing pseudomonas aeruginosa isolates.

A total of 97 clinical specimens were collected from the patients in the hospitals of Hamadan from November 2017 to May 2018, in Iran. Antibiotic susceptibility test was performed by disc diffusion method. Minimum inhibitory concentration (MIC) for imipenem was measured by E-test. Then, CIM test and polymerase chain reaction (PCR) methods were performed. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the CIM test were calculated for each of the genes. Using SPSS16 software, significance of CIM test was evaluated by chi-square test (X2).

In this study, the highest and lowest levels of resistance belonged to cefoxitin 91 (93.8%) and piperacilin/tazobactam 38 )39.2%). Among 97 P. aeruginosa clinical isolates, 49 (50.51%) were carbapenemase producer with positive results for CIM test in 44 (89.7%) isolates, and negative results for CIM test in 48 (49.48%) isolates. Therefore, the sensitivity and specificity of the CIM test were 90% and 100%, respectively.

According to the results of this study CIM method is an inexpensive test which can be easily performed and has high sensitivity and specificity for identification of carbapenemase producing P. aeruginosa isolates.

Pseudomonas aeruginosa is one of the most important pathogens of nosocomial infections, especially in the ICU (Intensive Care Unit), which has resistance to a wide range of antibiotics, especially Carbapenems. Among the most important resistance mechanisms of this bacteria against carbapenems are MexAB-OprM efflux pump. Therefore, the aim of this study was to evaluate the gene expression of MexAB-OprM efflux pump in clinical isolates of P. aeruginosa that isolated from ICU.

 A total of 33 sampales were isolated from patient in ICU units from different Hamadan hospitals, since november 2018 to May 2019. Antibiotic susceptibility testing was performed using disk diffusion and Minimal Inhibitory Concentration (MIC) methods by Etest for imipenem. Expression levels of MexAB-OprM efflux pump genes were measured by Real-Time PCR.

The results of statistical analysis showed that the highest resistance was to Ceftriaxone 21 (63.63%) and the lowest resistance was to piperacillin, 11 (33.33%). The results of the MIC of imipenem showed that among off 33 samples isolated from the ICU, 14 (42.42%) and 19 (57.57%) isolates were resistant and susceptible, respectively. Increased expression of of MexA, MexB and OprM genes compared with control strain were observed in 20% (4/20), 25% (5/20) and 20% (4/20) of isolates, respectively.

Increased expression of MexAB-OprM efflux pump is one of the most common mechanisms in the resistance of P. aeruginosa isolates against Carbapenem antibiotics in different units of hospitals especially intensive care unit. So identification of resistance mechanisms to Carbapenem antibiotics can be useful in controlling and treating such resistant isolates.

Recently, increased resistance to carbapenem antibiotics among Pseudomonas aeruginosa has raised concerns. The Carba NP test is used for detection of carbapenemase types. This study aimed at applying Carba NP method for rapid detection of P. aeruginosa isolates producing carbapenemase enzymes. A total of 97 clinical specimens was collected from patients in educational hospitals between November 2017 and May 2018 in Hamadan, Iran. Antibiotic susceptibility test was performed by disc diffusion method and MIC for imipenem was done by E-test. In order to detect carbapenemases enzymes, combined disk (CDT), CarbaNP, Modified Hodge (MHT), and Polymerase chain reaction (PCR) were performed. Statistical analysis was performed using SPSS V16. The highest and lowest levels of resistance were found to be to Ceftriaxone 65 (67%) and Piperacilin/Tazobactam 38 (39.2%), respectively. Among 97 clinical isolates of P.aeruginosa,
49 (50.51%) were positive for carbapenemase genes by PCR test from which 48 (97.95%) were positive for CarbaNP test. There were 48 (49.48%) PCR negative isolates of which all (100%) showed negative results for CarbaNP test. Compared to PCR, the sensitivity and specificity of this test was 98% and 100%, respectively. This study showed that a high percentage of P. aeruginosa was resistant to Carbapenem antibiotics and the CarbaNP method was highly sensitive and specific for detection of carbapenemase enzymes.

Pseudomonas aeruginosa is one of the main causes of hospital infections. Pathogenic factors in this bacterium may play a role in the resistance to carbapenem and beta-lactam. The purpose of this study was to evaluate the role and function of KPC and MBL enzymes in increasing the pathogenicity of Pseudomonas aeruginosa isolated from burn wounds. In this cross-sectional study, 63 isolates of Pseudomonas aeruginosa from burn wounds of different patients were isolated using biochemical tests such as fermentation of sugars in the OF medium, oxidase test, and so on. Determination of resistance pattern and strains with metallobetalactamase and carbapenema was done by disc diffusion method. The oprD gene was used for molecular confirmation of isolates. PCR method was used to detect pathogenicity genes. Out of 63 isolates of Pseudomonas aeruginosa isolated from burn patients, 10 isolates (15.83%) had KPC enzyme and 13 isolates (20.63%) had MBL enzymes. Doripenem, Ertapenem and meropenem were the most frequent. Also, the lasB gene was observed in 43 isolates (68.25%), plcN gene in 41 isolates (65.07%), lasA gene in 20 isolates (31.74%), apr in 60 isolates (95.23%), phzI gene in 53 isolates (84.12%), the phzII gene in 38 isolates (60.31%), phzH gene in 30 isolates (47.61%) and plcH gene in 56 isolates (88.88%). The results of this study showed that the production of Carbapnemase and MBL enzymes increased the pathogenicity of Pseudomonas aeruginosa isolated from burn wounds.

Gene mutation in Staphylococcus aureus is one of the most important causes of antibiotic-resistant strains. The High Resolution Melting Curve (HRM) analysis of DNA method can detect these mutations very high quality. The purpose of this study was to evaluate the role of clinical sample type in the occurrence of nucleotide mutations in the mecA gene of S. aureus by HRM method. In this experimental study, 43 clinical isolates of S. aureus were used. To detect possible mutations, isolates with mecA gene were replicated and sequenced. Then, analysis was performed using StepOne Software v2.3 and HRM v3.0.1 software. Sequencing results were used as gold-standard. This study with research ethics code IR.UMSHA.REC.1396.637 has been approved by research ethics committee at Hamadan University of Medical Sciences. Of 43 clinical isolates of S. aureus, 11 isolates (25.58%) had mecA gene and 32 isolates (47.41%) lacked the mecA gene. According to different clinical samples, 3 isolates (27.27%) were resistant to methicillin from blood samples, 2 isolates (18.18%) from urine specimens, 2 isolates (18.18%) from wound samples, 2 isolates (18.18%) of the catheter samples, 1 isolate (9.09%) of the abscess and 1 isolate (9.09%) were separated from the nose swab. In the meanwhile, isolates from the wound and urine had the highest mutation in the adenine amino acid as A → T, A → G, A → C, and A → X. Isolates taken from blood have mutations in Guanine amino acid as G → A. There was a significant relationship between type of mutation and type of clinical specimen in methicillin-resistant Staphylococcus aureus isolates.

The excessive use of Macrolide-Lincosamide-Streptogramin B (MLSB) to treat infections caused by Staphylococcus aureus (S. aureus,) the producer of toxic shock syndrome toxin-1 (TSST-1), can provide the basis for the emergence of resistant strains. The purpose of this study was to determine the pattern of antibiotic resistance to macrolides and tetracyclines and the genes involved in the occurrence of these resistance in S. aureus strains with TSST-1 toxin. In this descriptive cross-sectional study, 113 isolates of S. aureus were studied. Determination of pattern of resistance to macrolides and tetracyclines and different induction phenotypes was performed using disk diffusion method and D test. PCR was used to determine the presence of ermA, ermB, ermC, mphC and tsst gene. Of 113 isolates of S. aureus, 13 isolates (11.5%) were phenotypic D and 11 isolates (9.7%) were a phenotype R. Based on the resistance to clindamycin-erythromycin, 69 isolates (61.66%) were identified as S-phenotype. Tetracycline-resistant isolates (59.29%) had the highest frequency, and isolates resistant to minosilicon, dithromycin and tritromycin had the lowest abundance. In addition, 16 isolates (15.14%) were tst gene, 15 isolates (13.27%) were ermA gene, 6 isolates (5.3%) were ermB gene, 14 isolates (12.38%) were genes ermC and 1 isolate (0.88%) were also carriers of the aphC gene. There was a significant relationship between S. aureus MLSB strains and tst gene presence (p≥0.05). Induced resistance to clindamycin and tetracycline had a significant relationship with the presence of tsst gene in S. aureus strains producing TSST-1 toxin.

Pharmaceutical residuals like antibiotics in livestock products and their consumption by humans from food chain can lead to the spread of bacteria resistant to antibiotics. The aim of the current study was to investigate antibiotic resistance and determine the prevalence rate of genes encoding extended spectrum beta-lactamase (ESBLs) in Acinetobacter strains isolated from raw foodstuffs. In this study, 300 samples from protein foodstuffs (mutton, beef, chicken, hamburger, hot dog, sausages) and dairy foodstuffs (raw milk and cheese) were prepared and investigated in terms of contamination with Acinetobacter baumannii from July 2015 to November 2016. The isolated bacteria were identified by biochemical tests to species level and confirmed by the PCR technique via blaOXA-51 gene. Antibiotic resistance of the isolates was studied using the diffusion disc method. Also, the presence of ESBLs enzymes in the isolates wa s done phenotypically and genetically through PCR and combined disk tests. The results showed that 43 strains of A. baumannii were isolated from the protein and dairy foodstuffs, 93% from protein foodstuffs and 7% from dairy foodstuffs. Also, 30% of the isolates had multidrug- resistance (MDR). Further, the findings of PCR illustrated that the prevalence of genes encoding ESBLs in the isolates were: TEM 21%, PER 23.5%, VEB 18.5 % and SHV35%. Foodstuffs can act as a food source for A. baumannii that can lead to transferring and spreading genes encoding antibiotic resistance to humans.

Background and purpose: High Resolution Melting curve analysis DNA (HRM) is one of the most sensitive and precise methods for detecting Staphylococcus aureus and resistance to Methicillin. The aim of this study was to analyze the HRM for detection of methicillin-resistant S. aureus strains. In this experimental study, standard strains of S.aureus ATCC25923 and ATCC 33592 were used. To identify S.aureus from ITS gene and methicillin resistance, the mecA gene was used. Analysis was performed using StepOne v2.3 and HRM v3.0.1. Sequencing results were used as gold standard. The analytical sensitivity of the PCR method by ITS primer was capable of detecting 104 CFU bacteria and detecting bacteria for the mecA gene up to 103 CFU. The analytical sensitivity of the HRM method was also valid for ITS gene primer to dilute 10-2 CFU and the mecA gene primer up to a dilution of 10-5 CFU to detect bacteria. In HRM analysis, the lowest error rate was observed in the melting curves of DNA. Thus, considering the closest temperature range for analysis, the melting temperature for the ITS gene was 86 ± 0.5°C and for the mecA gene was 81± 0.5°C. The results of temperature and sequence determination proved the specificity of the HRM. The HRM has high sensitivity and specificity for detecting low levels of bacteria.

Staphylococcus aureus(S.aureus) has many pathogens. Antibiotic resistance may increase the invasion of this bacterium. The aim of this study was to determine the role and effect of some antibiotic resistance in the spread of pathogenic strains of S.aureus in different clinical specimens. 95 clinical isolates of S.aureus were collected from different clinical specimens. Antibiotic resistance pattern was determined by Disc diffusion method (Kirby-Bauer) for 6 different classes. Identification of adhesion agent genes in isolated isolates was performed using Multiplex-PCR and specific primers. For analysis of the results, GraphPad Prism version 6 and ꭕ2 statistical sampling was used. p≤0.05 was considered significant.
Findings: Of 95 isolates of S.aureus, 29 isolates (30.52%) were resistant to methicillin, 12 isolates (12.63%), resistant to clindamycin, 48 isolates (50.52%), resistant to gatyfloxacin, 88 (92.63%) isolates resistant to gentamicin, 57 (60%) isolates resistant to erythromycin and 79 isolates (83.15%) were resistant to tetracycline. fnbA genes were isolated in 14 isolates (14.73%), fnbB in 29 isolates (30.52%), fib in 21 isolates (22.10%), clfA in 17 isolates (17.89%) and clfB in 19 isolates (20%). There was a significant correlation between resistance to macular antibiotics, tetracycline, beta-lactam, lacosamide, aminoglycoside and pathogens. The adhesion factors in S.aureus possibly cause some structural changes and cause resistance to various antibiotic classes

Clindamycin is one of the selective drugs for treatment of staphylococcal infections. Molecular methods can complete phenotypic methods to diagnosis induction resistance to clindamycin. The aim of this study was to identify the genes responsible for the resistance to clindamycin and erythromycin, and determine their antibiotic resistance pattern. 100 isolates of Staphylococcus epidermidis and Staphylococcus saprophyticus were isolated from 466 different clinical specimens using biochemical tests. Using the disc diffusion method, Antibiogram susceptibility test was conducted to determinate lincosamides and tetracycline resistance pattern. Then ermA, ermB, ermC and msrA genes were identified and investigated by PCR method. Out of 100 strains of coagulase-negative staphylococci isolated from clinical specimens, 5 isolates were identified as S. saprophyticus (5%) and 55 isolates of S. epidermidis (55%), respectively. Out of the 5 isolated of S. saprophyticus, 2 (40%) isolates were resistant to methicillin and one (20%) isolate had D phenotype. In addition, 1 isolate had ermA gene and 1 isolate had ermB. Out of the 55 isolates of S. epidermidis, 25 (45.45%) isolates were resistant to methicillin, of which nine (36%) isolates had D phenotype. Also, 4 (16%) isolates had ermA gene, 3 (12%) isolates had ermB, 6 (24%) isolates had ermC and 1 (4%) isolate was carrying the msrA. The phenotypic pattern of resistance to macrolide- lincosamides groups does not have a high degree of accuracy in detecting methicillin-resistant MLSB strains.

Secreted toxins of the burn wounds caused by Pseudomonas aeruginosa play an important role in spreading infection. The antibiotic resistance pattern may have an effect on the increased toxicity of this bacterium. Therefore, the aim of this study was to determine the relationship between the presence of P. aeruginosa toxins isolated from burn wounds and the antibiotic resistance pattern. In this cross sectional-descriptive study, P. aeruginosa isolates were first isolated from the burn wound samples by using biochemical tests. The next step dealt with the investigation of antibiotic resistance pattern based on CLSI (Clinical and Laboratory Standards Institute). The process of identifying the genes responsible for producing toxin was performed by polymerase chain reaction method. Data analysis was performed in SPSS (version 16) using the Chi-square test. Out of 250 strains isolated from burn wounds, 63 isolates (25.2%) were obtained from P. aeruginosa. With regard to resistance, the obtained results revealed that Doripenem, Ertapenem, and Meropenem antibiotics had the highest frequency, whereas, the antibiotics of Piperacillin/Tazobactam and Piperacillin had the lowest frequency. Moreover, resistance to imipenem was observed to be semi-sensitive regarding the minimum inhibitory concentration in three isolates (76.4%). The exoS, toxA, exoT, exoY, and pvdA genes were observed in 40 (63.49%), 31(49.2%), 39 (61.9%), 56 (88.88%), and 50 (79.36%) isolates, respectively. In addition, there was a significant correlation between the antibiotic resistance pattern and distribution of toxin genes (P <0.05). According to the obtained results, it can be concluded that the antimicrobial resistance pattern could play an important role in the distribution of P. aeruginosa toxin genes isolated from burn wounds.

The use of vitamin K plays a very important role in human health. This vitamin may have effects on some of the pathogens such as biofilms in Staphylococcus aureus.In this account, the purpose of this study was to determine the effect of vitamin K on the expression of icaA and icaR genes in methicillin-resistant S. aureus isolated from the wound sample.
In this interventional study, 15 isolates of methicillin-resistant S. aureus were treated with vitamin K at concentrations of 1, 10, 50, 100, 200, 300 and 500 μg / ml. Time intervals for incubation were determined 24, 48 and 72 hours. Finally, the desired RNA was extracted and cDNA was synthesized. The expressions of icaA and icaR genes were evaluated using qPCR method.
The expression levels of icaA and icaR genes were used as controls prior to vitamin treatment. Both of genes showed a reduced expression rate in isolates which treated by vitamin K. This effect on the expression of icaA and icaR was clearly observed at a concentration of 200 μg and also in the 48-hour incubation.
Vitamin K along with some antibiotics could be effective against some certain skin infections which caused by methicillin resistance S. aureus.

Staphylococcus aureus is one of the most common causes of food poisoning, which due to excessive use of antibiotics has become resistant to different antibiotics. In addition, it is also capable of producing biofilm. The aim of this study was to investigate antibiotic resistance patterns and phenotypic study of biofilm production in S. aureus isolates separated from confectionary pastries in Hamadan.
In this descriptive- cross-sectional study, 370 samples of creamy (280) and dried (90) pastries were collected randomly (May to February 2017). To separate possible microbial contaminations, part of samples were cultivated with conventional microbiological methods. The separated S. aureus isolates were confirmed using polymerase chain reaction (PCR) and nuc gene amplification. The antibiotic susceptibility pattern of all isolates was determined by disk agar diffusion (DAD) method based on CLSI guideline and also, microplate modified method was used to identify biofilm strains.
The results showed that 34.64% of the creamy pastries and 3.33% of the dried pastries were infected with S. aureus. Antibiogram results showed the highest resistance was related to penicillin (90%). In the quantitative study of biofilm production, 42 strains (42%) were strongly adhesive, while 17 (17%) and 41 (41%) strains were weakly adhesive and lacking adhesive ability, respectively.
Consumption of creamy pastries increases the risk of infection with S. aureus and is a serious warning to the health system. Pasteurization and storage of food stuff in the refrigerator, continuous microbial control of pastries and the screening of the confectionary staff can reduce the level of microbial contamination and the risk of staphylococcal poisoning.

Effective antibiotics on the translation pathway, such as mupirocin, may cause gene mutations in methicillin-resistant Staphylococcus aureus in long-term. Using high-sensitivity methods plays an important role in identifying these bacteria. Our goal was to identify these mutations using high-resolution melting (HRM) curve of DNA analysis.
Resistance to mupirocin was identified using disc microdilution plate method in according to the Clinical and Laboratory Standards Institute (CLSI) guideline. mupA gene amplification in the isolates of methicillin-resistant Staphylococcus aureus was done using polymerase chain reaction (PCR). Then, analysis was performed using StepOne Software and HRM software. Sequencing was used as gold-standard method for confirming of the results.
Findings: Out of 162 Staphylococcus aureus isolates, 83 (51.32%) were methicillin resistant. Among methicillin-resistant Staphylococcus aureus isolates, 47 (52.80 %) showed high level resistance to mupirocin carrying mupA. The most and lowest resistance was observed for penicillin (79.62%) and ceftazidime (6.17%), respectively. Moreover, all of multi-drug resistant (MDR) isolates were mupirucin resistant, too. Among mupirocin-resistant Staphylococcus aureus, wound samples were the most prevalent. Besides, isolates obtained from wound and blood demonstrated the highest mutation in A and G bases. Meaningful association was observed between the type of clinical sample and mutation rate, and resistance to mupirocin and methicillin (P Mupirocin-derived gene mutations provide multi-drug resistance in methicillin-resistant Staphylococcus aureus.

As one of the fat-soluble vitamins, vitamin K, can in some cases have intrinsic inhibitory effects on the activity of methicillin-resistant Staphylococcus aureus. The aim of this study, was to determine the effect of vitamin K2 on the expression of mecA and blaZ genes in Multi Drug Resistant Methicilin Resistance S. aureus isolates.
76 clinical isolates of methicillin-resistant S.aureus were isolated by phenotypic tests. For treatment of isolates, concentrations of 1, 10, 50, 100, 200, 300 and 500 μg / ml of vitamin K2 and different time intervals were used. The q-PCR method was used to quantitatively evaluate the genes. It was also used to analyze the results of REST 2008 V3 and SPSS 16 software.
The expression of blaZ and mecA genes was reduced only at a concentration of 500 μg / ml of vitamin K2. Additionally, the 48 and 72 hours incubation times had the best effect on the effect of vitamins on the genes studied. In the isolates from clinical specimens, ulcers and urine reduced the expression of mecA and blaZ genes. Also, there was a significant relationship between incubation time and clinical specimen type on decreasing the expression of the desired genes (P≤0.01, P≤0.05).
In accordance to the results of this study, the use of vitamin K2 can play an important role in the control of methicillin-resistant Staphylococcus aureus strains.

Quorum sensing (QS) phenomenon, promoters involved in this pathway and the effect of these promoters on the expression of some structural genes, such as agrA and PII, could reveal the proper activity and gene expression of antibiotic resistance in S. aureus. The aim of this study was defining the relationship between promoter-dependent Quorum Sensing induced genes and methicillin resistance in clinical strains of S. aureus.
In this analytical study, 315 isolates of S. aureus were collected. Resistant and susceptible strains were evaluated for the presence of promoter-dependent quorum sensing induced genes qualitatively and quantitatively. Calculating the gene expression of agrA and PII was carried out by Real-Time PCR. Statistical analysis (descriptive and analytical) was done using SPSS version 16 software and the data analysis of gene expression was carried out by REST 2008 V3.
Among 125 strains of S. aureus resistant to methicillin, 100 isolates (83/33%) had the promoter P2 gene and all isolates had the agrA gene and of 190 strains susceptible to methicillin, 84 isolates (44/21%) had the P2 gene and 169 isolated (88/94%) had the agrA gene. P2 and AgrA gene expression was greater in the resistant isolates in comparison to susceptible isolates.
In accordance with the results of this study, the association between quorum sensing /gene induction and drug resistance is a matter of importance.

Backgrounds and Aim: Staphylococcus aureus biofilms are involved in a multitude of serious chronic infections. Production of biofilms is a defensive-invasive process controlled and regulated by the aap and icaR genes. The expression levels of these genes play an important role in the formation of biofilm. The aim of this study was to investigate the expression of icaR and aap regulatory genes in clinical isolates of S. aureus resistant to methicillin and gentamicin.
In this analytical study, among 285 samples, we detected 100 isolates of methicillin resistant and 82 isolates of gentamicin resistant S. aureus. Resistant strains were evaluated for the presence of biofilm regulatory genes. The expression levels of regulatory genes were measured by real-time PCR method. We used SPSS software 16 for statistical analysis and also REST 2008 V3 software for analysis of quantitative results.
Among 100 methicillin resistant and 82 gentamicin resistant isolates of S. aureus the highest expression levels of icaR and aap genes were detected in the smears obtained from the wounds and catheters. Moreover, a different pattern of gene expression was observed in multidrug resistant strains in comparison to the strains with lower rate of resistance. Also, there was a significant relationship between the presence and activity of regulatory genes and biofilm formation in different samples (p≤0 / 05).
Considering the frequency of biofilm producing strains of S. aureus in the smears from the catheters and wounds and also increased gene expression, appropriate therapeutic measures should be considered for methicillin and gentamicin resistant of S. aureus.

AmpC-type beta-lactamases have been implicated in group C of Amber, which includes EBC, CIT, MOX, FOX, DHA, and ACC. The active presence of these plasmid genes in clinical isolates of P.aeruginosa has resulted in resistance to a wide range of antibiotics. Therefore, we aimed to determine the minimum inhibitory concentrations (MIC) of different antibiotic groups in clinical isolates of P. aeruginosa carrying AmpC enzyme and study their relationship pattern.
In this descriptive study, the MIC of 95 P. aeruginosa isolates was determined using E-test for cefocytosine, cefpodoxime, cefotaxime, ceftazidime, ciprofloxacin, colicitin, aztreonam, and ceftriaxone antibiotics (Liofilchem, Italy). Multiplex polymerase chain reaction was used to amplify and identify plasmid genes. The Chi-squared test was used to determine the relationship between variables.
Of the 95 P. aeruginosa isolates, 95 (100%) isolates were resistant to cefoxitin, 79 (83.5%) isolates to cefpodoxime, 2 (2.1%) isolates to ceftazidime, 87 (81.57%) isolates to ceftriaxone, and 22 (23.15%) isolates were resistant to aterranum, but none of the isolates was resistant to colistin. In addition, 21 (22.1%) isolates had FOX gene, 13 (11.57%) isolates had AAC gene, 7 (36.6%) isolates had MOX gene, 4 (21.4%) isolates had CIT gene, 2 (2.1%) isolates had DHA gene, and 1 (1.05%) isolate had EBC gene. It is worth mentioning that there was a significant relationship between the presence of plasmid genes and antibiotic resistance (level of significance: P≤0.05).
The presence of the genes encoding the AmpC enzyme can provide the ground for resistance to a broad range of antibiotics.

Different clinical specimens play a decisive role in the type and nature of drug resistance in pathogenic organisms. Occasionally, the presence of certain antibiotic resistance genes is associated with the type of clinical specimen. The aim of this study was to determine the relationship between the presence of chromosomal and plasmid-encoded AmpC genes and type of clinical specimen in Pseudomonas aeruginosa.
In this descriptive and experimental study, 114 isolates of Pseudomonas aeruginosa, and clinical specimens including blood, urine, wound secretion, burn injuries were collected from teaching hospitals in Hamadan. The presence of chromosomal and plasmid-encoded AmpC genes was evaluated using multiplex PCR technique.
FINDINGS: The plasmid-encoded AmpC genes were observed more than chromosomal genes in Pseudomonas aeruginosa isolates. The FOX gene with a value of 29 (37.66%) (p≤0.037) and DHA gene with a value of 5(6.4%) (p≤0.015) in plasmid-encoded AmpC genes, while FOX gene with a value of 39 (48.75%) (p≤0.001) and MOX gene with a value of 2 (7.36%) in chromosomal AmpC genes had the highest and lowest frequency, respectively.
The results of the study showed that the presence of chromosomal and plasmid-encoded AmpC genes may have various frequencies according to the type of clinical specimen.

Due to the increasing in antibiotic resistance in bacteria, especially the infections which their treatment is very difficult, there is a need for producing new drugs. The aim of this study was identification and purification of quorum sensing peptides causing apoptosis in Staphylococcus aureus as new treatment antibiotics.
The supernatant from Staphylococcus aureus, Enterococcus faecalis, and Enterococcus faecium were collected after centrifugation. Then, the supernatant was isolated from the specimens that had the greatest effect on the growth of bacteria. Liquid chromatography was used to purify it. In next step, for detection of protein concentration, Bradford test and for confirmation, two dimensional electrophoresis were used. Finally, to determine the antimicrobial activity of purified peptides, minimum inhibitory concentration (MIC) and minimum inhibitory concentration (MBC) of peptides were investigated.
Findings: The obtained effective ingredient was a polypeptide that was effective against multi-drug resistant bacteria. The results of MIC for methicillin-resistant Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Salmonella paratyphi A and B, Klebsiella oxytoka, Acinetobacter Bumanni, and Shigella dysenteria were 3.2, 7.0, 5.0, 5.0, 3.0, 6.0, 1.0, and 7.0 µg/ml, respectively.
The polypeptide derived from this study showed a vast antimicrobial property against gram-positive and gram-negative bacteria.

Resistance to methicillin and the presence of the ccr gene in Staphylococcus aureus have provided the basis for the emergence of methicillin resistant strains. The aim of this study was to identify the ccr cassette alleles in methicillin-resistant S.aureus strains and to determine the relationship between the presence of these casts with a multivariate process.
In this study, 135 clinical isolates of methicillin-resistant S.aureus was isolated by genotypic methods. ccr gene cassette was evaluated qualitatively by multiplex PCR method. Data was analyzed using SPSS version 16 and also, the chi - square test was used.
FINDINGS: Out of 135 strains of S.aureus resistant to methicillin, penicillin and erythromycin antibiotic resistance were the most frequent, more than 90%, respectively. Also, ccr gene cassette in the study on genes ccrA/B1, ccrA/B2, ccrA/B3, ccrA/B4, ccrA2/B, ccrC had taken place, respectively, in 2 isolates (1.3%) for gene ccrA/B1, 12 isolates (8.2%) ccrA/B2, 15 isolates (10.34 %) ccrA/B3, 2 isolates (1.3%) ccrA/B4, 4 isolates (8.2 percent) ccrA2/B and 22 isolates (15.87 %) were positive for the gene ccrC. A significant correlation between the presence of these genes and antibiotic distribution was observed (p=0.05).
The ccr gene cassette can provide a background of resistance to various antibiotics in methicillin-resistant S.aureus strains.

Efflux pumps are regarded as one of the most important mechanisms of antibiotic resistance in this era. Staphylococcus aureus is one of the bacterial groups with efflux pumps. The pumps’ activity is coded by specific genes. The aim of this study was to determine the phenotypic and molecular pattern of efflux pumps in the clinical isolates of methicillin-resistant S. aureus.
This study was conducted on 302 S. aureus bacteria collected from different clinical specimens. We detected 145 isolates of methicillin-resistant using disk diffusion method with cefoxitin (30 µg) as well as minimum inhibitory concentration with E-test strips and cefoxitin disks. In addition, multiplex polymerase chain reaction method was employed to identify the genes responsible for resistance to efflux pump and gyrase. The data were analyzed using SPSS software version 16.
Among the 145 isolates of methicillin-resistant S. aureus, norfloxacin and ciprofloxacin had the highest frequency. Furthermore, norA, norB, norC, grlA, grlB, gyrA, and gyrB genes were positive in 39 (25.825%), 12 (9.97%), 41 (49.15%), 75 (49.66%), 37 (26.50%), 58 (38.41%), and 19 clinical isolates (12.58%), respectively.
As the findings indicated, the presence of efflux pumps in the strains of methicillin-resistant Staphylococcus aureus provided the ground for the emergence of multi-drug resistant bacteria.

Resistance to beta-lactams is the most important feature in Staphylococcus aureus (S. aureus). There is a possibility that the amount of resistance and beta-lactam antibiotic resistance gene expression are different in Staphylococcus resistant strains. The aim of this study was to determine the expression of mecA and blaZ genes in methicillin-resistant S. aureus and the relationship between gene expression patters.
In this experimental-analysis study, 120 clinical isolates of methicillin-resistant S. aureus were isolated from different clinical samples using phenotypic tests. To study the quality of the mecA and blaZ genes in resistant isolates, polymerase chain reaction (PCR) was used. In addition, the quantity of genes, SYBR-Green-1-based real-time PCR was applied. REST 2008 and SPSS software were used to analyze the data.
Findings: Out of 120 isolates of methicillin-resistant S. aureus, 105 isolates (87.5%) had blaZ gene. The most diverse gene expression changes in sample type were seen in blood and urine samples. So, the expression on the wound and urine clinical samples was dramatically more than the other sites. In addition, significant relationship was observed between the blaZ and mecA gene expression and the kind of clinical samples.
The results of this study suggested that different doses of antibiotics should be used to treat staphylococcal infections in different organs.

Rapid and timely detection of Staphylococcus aureus can play a significant role in the treatment of staphylococcal infections.Impresingly, by precise designing methods which have acceptable sensitivity and specificity, can identify species and even antibiotic-resistant strains. The purpose of this study was to evaluate the real time PCR diagnostic method based on the melting curve analysis for the detection of clinical isolates of S. aureus and the methicilin resistance gene.
In this experimental study, clinical isolated of S. aureus was used from the Microbiology Bank of Hamadan University of Medical Sciences. The primer design was done by selecting (ITS) target for S. aureus and the mecA gene for methicillin-resistant strains. Real-time PCR and DNA melting curves analysis were used to determine the analytical specificity and sensitivity of the designed primers.
The analytical specificity of the primers was 83.79 ° C for S. aureus and 76.6 ° C for methicillin resistant Staphylococcus aureus respectively. The analytical sensitivity of the primers was 15 CFU/ml bacteria for ITS gene and 25 CFU/ml bacteria for mecA gene.
By selecting appropriate primers and using sensitive molecular techniques, which could be the main factors for designing of both quick and accurate method, it is possible to identify invasive bacteria such as S. aureus.