Antimicrobial Resistance of Pseudomonas aeruginosa Isolated from Human Infections in N’Djamena, Chad

Background: Urinary Tract infections and pus are major public health problems. The evolution of bacterial resistance to antibiotics makes the treatment of these infections problematic. This is why this study is undertaken to identify and evaluate the resistance of Pseudomonas aeruginosa to antibiotics. Methods: This is a prospective study carried out from December 2020 to November 2021. The germs were isolated on the agar supplemented with cetrimide and identified by the API 20 NE gallery method according to the manufacturer’s protocol. The strains’ resistance profiles were determined by the diffusion method on Mueller-Hinton according to the criteria EUCAST- 2021. Results: A total of 46/1467 (3.13%) Pseudomonas aeruginosa were identified, of which 29/1008 (2.87%) were urinary tract infections and 17/459 (3.70%) were pus. The high resistances were: 97.8% to ceftazidim, 91.3% to aztreonam, 93.5% to cefepim, 82.6% to piperacillin, 58.7% to levofloxacin, 52.2% to amikacin, 47.8% to tazobactam-piperacillin, 47.8% to tobramycin and 43.5% to ciprofloxacin. Low resistance was only 2.2% to fosfomycin, 2.2% to colistin and 15.2% to imipenem. Conclusion: This study reveals the considerable resistance of Pseudomonas aeruginosa to commonly used antibiotics, and thus compromises the empirical treatment practiced in hospitals. This result motivates the need to carry out susceptibility testing of isolates before any prescription of antimicrobials.

Enhancing Accumulation and Penetration Efficiency of Next-Generation Antibiotics to Mitigate Antibiotic Resistance in Pseudomonas aeruginosa PAO1

This study explores the efficacy of advanced antibiotic compounds against P. aeruginosa, focusing on Antibiotic B, an enhanced derivative of Ceftriaxone. The study measured the intracellular uptake of Antibiotic B and introduced a novel adjuvant, Influximax, which augmented its antibacterial activity. Results showed a diminished potential for resistance emergence with Antibiotic B, particularly when used in combination with Influximax. The study suggests that optimizing antibiotic delivery into bacterial cells and leveraging syner-gistic adjuvant combinations can enhance drug resistance combat. .

Resistant patterns of Pseudomonas aeruginosa in a Malaysian teaching hospital

Objective:Pseudomonas aeruginosa is an opportunistic pathogen and the leading cause of nosocomial infections. Currently a notable increase in the prevalence of multidrug-resistant P.aeruginosa worldwide has been reported in hospitalized patients and was associated with high morbidity and mortality.Methods:A retrospective laboratory based analysis regarding the spectrum and distribution of P.aeruginosa from a wide range of clinical samples in Hospital Universiti Sains Malaysia since January 2003 to December 2007 was done.Results: Altogether,there were 2 308 clinical isolates analyzed.The main sources of P.aeruginosa were from swab,respiratory,urine and blood specimens which accounted for 28.2%,21.8%,13.2%and 12.8% respectively.Results showed significant reduction in percentage of resistant towards three antibiotic namely ciprofloxacin,ceftazidime and imipenem.However the percentage of pan-resistant P.aeruginosa increased steadily over these years.Conclusion:This data is helpful to the clinician in guiding the choice of appropriate antibiotic to treat P.aeruginosa infection.At the same time,it warrants a more aggressive infection control activity to be implemented to control the spread of pan resistant strain in this centre.

Surveillance of Fluoroquinolone-Resistant Clinical Isolates of <i>Pseudomonas aeruginosa</i>

Ciprofloxacin (CPFX) and pazufloxacin (PZFX) have strong antibacterial activity against Pseudomonas aeruginosa. We investigated the sensitivity of P. aeruginosa to CPFX and PZFX in 373 strains isolated from inpatients (321 strains) and outpatients (52 strains) during September 2010 to September 2011 at Toho University Ohashi Medical Center. The percentage of CPFX-non-susceptible (≥3.91 μg/mL) among inpatients was 22.4%, but that among outpatients was 1.9%. As the major resistance mechanism to fluoroquinolones in P. aeruginosa involves modification of type II topoisomerases (DNA gyrase and topoisomerase IV), we examined mutations in the quinolone-resistance-determining regions (QRDRs) of gyrA and parC of P. aeruginosa isolates. Among the 373 isolates, 73 isolates had reduced CPFX-susceptibility and 88 had reduced PZFX-susceptibility. Sequencing of gyrA and parC revealed base substitutions that resulted in amino acid replacements in QRDR of GyrA in 70 P. aeruginosa isolates, while Thr83Ile (in GyrA) and Ser87Leu (in ParC) substitutions were found in 12 strains. These replacements were clearly associated with reduced susceptibility to CPFX and PZFX. However, we also found strains with high MICs to quinolones without mutations in either gyrA or parC. We then investigated the effect of efflux pumps in CPFX-resistance in these isolates. In the presence of an efflux pump inhibitor, MIC values in 12 of 66 strains decreased to 1/23. We also sequenced genes related to overexpression of efflux pumps, viz., mexZ, mexR, and nfxB. Eight of the strains without mutations in QRDRs had a mutation in mexZ, 7 strains had a mutation in mexR, but no mutation was identified in nfxB.

Effect of Combined Therapy on Colistin Resistant <i>Pseudomonas aeruginosa</i>: An <i>in Vitro</i>Study

Pseudomonas aeruginosa is known for its antibiotic resistance to the clinicians. The infections caused by this pathogen are hard to treat because of its highly versatile property to mutate and acquire drug resistance. Pseudomonas aeruginosa also possesses intrinsic property of resistance to certain antibiotics like tetracyclines. However;in a practice to overcome the problem of multi drug resistance, clinicians restored the use of some antibiotics that were previously been used to treat the Pseudomonal infections;but they were discontinued because of its toxic effects. Colistin is an example of one such antibiotic. Use of Colistin was barred for its neurotoxicity. However in recent clinical trials, Colistin was reintroduced to fight with this superbug. Sadly in recent years, Pseudomonas aeruginosa developed resistance to Colistin as well. Therefore combined therapy is an alternate and suitable treatment to overcome the infections caused by multidrug-resistant Pseudomonas aeruginosa. The present study is an in vitro study;in which we tested synergy between two antibiotics namely streptomycin and Colistin on 29 clinical isolates of P. aeruginosa collected from hospitals in Jazan city KSA. The combination of two drugs showed synergistic activity on 55.1% of tested strains, while 20.6% strains had partial synergy, whereas indifferent synergy was observed in 13.8% strains and the 6.8% of strains had additive synergy. In addition to this, the drugs when combined also showed antagonism on one strain (3.44%). The present study showed synergistic action on Colistin-resistant Pseudomonas aeruginosa to greater extent (55.1%) by the two tested drugs. Hence Colistin and streptomycin can be used as a suitable combination therapy (in vivo) to treat multidrug resistant P. aeruginosa infections.

Mutational and Phylogenetic Analysis of <i>nfxB</i>Gene in Multidrug-Resistant Clinical Isolates of <i>Pseudomonas aeruginosa</i>Hyperexpressing MexCD-OprJ Efflux Pump

The present study focused on MexCD-OprJ efflux pump and its regulatory gene nfxB in multidrug resistant (MDR) clinical isolates of Pseudomonas aeruginosa collected from Kerala, South India. Semi-quantitative reverse transcription-PCR technique was employed to detect hyperexpression of the efflux pump gene, mexD. Amplicons from nfxB gene of isolates hyperexpressing the efflux pump were sequenced for mutational and phylogenetic analysis. Among 29 isolates of MDR P. aeruginosa, increased mexD transcription was detected in 10.3% of the isolates when compared with P. aeruginosa reference strain, PAO (MTCC-3541). Various synonymous and non-synonymous mutations in nfxB regulatory gene sequences were detected. Notably, mutations detected in the strains designate Pa6 and Pa7 have been found to be novel and are hitherto unreported in GenBank data base. The genetic divergence and homogeneity of the nfxB regulatory gene sequences of mexCD-oprJ operon were clearly apparent in the phylogram generated employing similar sequences retrieved from the public database.

Overview of Multidrug-Resistant Pseudomonas aeruginosa and Novel Therapeutic Approaches

Gram-negative bacilli Pseudomonas aeruginosa is an important pathogen in hospitalized patients, contributing to their morbidity and mortality due to its multiple resistance mechanisms. Therefore, as therapeutic options become restricted, the search for new agents is a priority. Latterly an accelerated increase in frequency of multidrug-resistant clinical strains has severely limited the availability of therapeutic options. Several in vitro and in vitro studies evaluating the efficacy of different antimicrobials agents and development of vaccines against P. aeruginosa have been reported as novel approaches, such as inhibition of virulence factor expression or inhibition of their metabolic pathways.

Study on the Effect of Shuanghuanglian Powder Needle Combined with Cefoperazone and Sulbactam Sodium on Pseudomonas aeruginosa in Vitro

Objective: To explore the antibacterial activity of combined use of Shuanghuanglian and cefoperazone sulbactam sodium on resistant strains of Pseudomonas aeruginosa. Methods: The Pseudomonas aeruginosa strains which were sensitive and resistant to cefoperazone sulbactam sodium were selected to prepare different test bacterial solutions respectively;The experimental liquid of Shuanghuanglian and Cefoperazone Sulbactam Sodium were prepared separately and set as different test groups and control groups;The Drug Sensitivity Tests of Shuanghuanglian and cefoperazone sulbactam sodium at different concentration gradients which were used alone or used in combination were carried out for different strains with sensitivity and resistance, And use standard entry as a reference control. Result: The results of drug sensitivity test of Shuanghuanglian combined with Cefoperazone-Sulbactam sodium against the resistant strains of Pseudomonas aeruginosa were compared with the results of drug sensitivity test of the two separately used, and the difference was statistically significant (P 〈 0.05) [The drug sensitivity test results of Shuanghuanglian and cefoperazone sulbactam sodium to Pseudomonas aeruginosa resistant strains were statistically significant compared with the drug sensitivity test results of Shuanghuanglian and Cefoperazone Sulbactam Sodium used separately (P 〈 0.05)];There was a dependence between strains and concentration in the effect of the combination of the two drugs. Conclusion: The combination of Shuanghuanglian and cefoperazone sulbactam sodium has synergistic antibacterial or bactericidal effect on Pseudomonas aeruginosa resistant strains. .

Analysis of Clinical Characteristics and Risk Factors of Pseudomonas aeruginosa Bloodstream Infection in 55 Cases

Objective: Pseudomonas aeruginosa bloodstream infection presents a severe challenge to hospitalized patients. To investigate the clinical characteristics, risk factors and drug resistance of Pseudomonas aeruginosa bloodstream infection. Methods: Clinical data and laboratory results of patients with Pseudomonas aeruginosa bloodstream infection in the First Affiliated Hospital of Yangtze University from January 2019 to December 2022 were retrospectively analyzed. The factors associated with infection and death were analyzed by univariate analysis. Results: A total of 55 patients were enrolled in this study, The 28-day mortality rate was 14.5%. Univariate analysis showed that high procalcitonin, low albumin, ICU admission, central venous catheterization, indwelling catheter, and mechanical ventilation were associated with death. Multivariate Logistic regression analysis showed that hypoproteinemia and central venous catheters were independent risk factors for death in patients with Pseudomonas aeruginosa bloodstream infection. Conclusions: The drug resistance of P. aeruginosa bloodstream infection is not high, but the fatality rate is high. The combination of hypoalbuminemia after the onset of the disease and the use of central vein catheters can lead to increased mortality, suggesting that clinical identification of high-risk patients as early as possible, reducing the use of catheters, preventing the occurrence of P. aeruginosa bloodstream infection and improving the prognosis.

Antibiotic resistance pattern of Pseudomonas aeruginosa wound isolates among Chinese burn patients:A systematic review and meta analysis

Objective:To investigate the resistance profiles to antimicrobial agents of wound-isolated Pseudomonas(P.)aeruginosa among Chinese burn patients.Methods:Electronic databases and manual search were used to identify eligible studies published since 2010.The objectives were pooled resistance rates for eleven common antimicrobial agents,estimated by a random-effects model.Subgroup analyses were conducted by stratifying the studies into three four-year periods based on year of isolation.Results:A total of 35 studies were included.Gentamicin had the highest pooled resistance rate(56%,95%CI 48%-64%),while meropenem had the lowest pooled resistance rate(29%,95%CI 20%-40%).There was an increasing trend of resistance to common antimicrobial agents of wound-isolated P.aeruginosa over a span of twelve years(2009-2020).There remained the highest risk of gentamicin resistance over time in China.Subgroup analyses indicated significantly higher resistances to ceftazidime and levofloxacin from 2017 to 2020.Conclusions:Enhanced resistance to common antimicrobial agents in wound-isolated P.aeruginosa presents a challenge in burn wound management in China's Mainland.Effective stewardship programs should be established based on corresponding resistance profiles,thereby optimizing treatment options for hospitalized burn patients.

Characterization of Cr(Ⅵ) resistance and reduction by Pseudomonas aeruginosa

The experiments were conducted to evaluate the Cr(Ⅵ)resistance and reduction by Pseudomonas aeruginosa.After this bacterium tolerated 40 mg/L Cr(Ⅵ),the growth of cells was observed.The bacterial growth was obviously lower than the controls over 24 h and the binary cell fission was observed in cell morphology by scanning electron microscope.P.aeruginosa was found to be able to reduce Cr(Ⅵ)although Cr(Ⅵ)had toxic effects on the cells.The results demonstrate that Cr(Ⅵ)is reduced from 40 mg/L to about 18 mg/L in 72 h.The value of pH drops from 7.02 to around 5.65 after 72 h.A significant increase in the value of redox potential occurs during Cr(Ⅵ)reduction and Cr(Ⅵ)reduction can be observed over a range of redox potential from+3 mV to+91 mV.Both of SO4 2-and NO3 -have no effect on Cr(Ⅵ)reduction.The presence of Zn 2+has a notable inhibitory effect on Cr(Ⅵ) reduction while Cu 2+ substantially stimulates Cr(Ⅵ)reduction.In the presence of Zn 2+ ,Cr(Ⅵ)decreases from 40 mg/L to only 26-27 mg/L,whereas Cr(Ⅵ)drops to 1-2 mg/L after 48 h in the presence of Cu2 +.

Surveillance on the multi-drug resistance and the β-lactamase resistance genes in Pseudomonas aeruginosa

In the present study,27 multi-drug resistant strains of Pseudomonas aeruginosa were isolated from clinical specimens in our hospital from Jan 2005 to Nov 2005,in which the resistant genes encodingβ-lactamase including TEM,SHV,OXA,PER,VEB,GES,CARB,IMP,VIM,SPM,GIM,DHA and OprD2 were tested by PCR amplification and sequenced by DNA sequencer.It was found that the detection rates of bla_(VEB),bla_(GES) and bla_(CARB) genes in these 27 isolates of P.aeruginosa were 11.1%, 11.1% and 48.1%,respectively,but almost the oprD2 gene was lacked(92.6%).In addition,the resistant genes encoding TEM,SHV,OXA,PER,IMP,VIM,SPM,GIM and DHAβ-lactamase were all not found.It was also demonstrated that the sequence of bla_(VEB) gene appeared to be identical to that of the bla_(VEB-1)(AY536743),while the bla_(CES) and bla_(CARB) genes shared 99% identity with bla_(GES-1) (AY219651)and bla_(CARB-3)(S46063) genes.From these observations,it is evident that P.aeruginosa carrying the bla_(VES),bla_(GES) and bla_(CARB) resistant genes isolated in our hospital confers the resistance toβ- lactams,and the loss of the oprD2 gene may be the important cause to develop resistance to imipenem in P.aeruginosa.

Antimicrobial Resistance Profiles and Clonal Relatedness of <i>Pseudomonas aeruginosa</i>Strains Recovered from Wounds Infections of Outpatient Population Presenting in a Rural Hospital in Kenya

Pseudomonas aeruginosa is a leading cause of hospital infections and is intrinsically resistant to most antibiotics. Emergence of multidrug resistant (MDR) strains has been reported in the world and poses a great challenge in the management of infections associated with this species. While a substantial amount of research has been done on strains from most of other infection caused by this species in developed countries, little is known about the susceptibility profiles of strains recovered from African countries in general and Kenya in particular. Furthermore, there is paucity of data regarding strain, phenotype and genetic diversity of strains recoverable from wounds among patients in Kenya. The possible risk factors for acquisition of MDR strains and possible factors that could fuel clonal expansion in hospital and community settings remain undetermined. This cross-sectional study conducted in Tigoni Hospital, a rural area in Central Kenya sought to determine risk factors associated with carriage of MDR Pseudomonas aeruginosa in wounds among rural population. We also analyzed antimicrobial resistance profiles among these isolates. Prevalence of P. aeruginosa in wounds was 28% with 85 isolates recovered from wounds of 299 participants. Most antimicrobial resistance prevalence was recorded towards Ceftazidime (64%) and Cefepime (52%) while Piperacillin-tazobactam was the most effective antimicrobial agent with a resistance prevalence rate of 20%. Resistance towards new classes of aminoglycosides such as Gentamicin was at 45% while that towards Amikacin was at 40%. Compared to other related studies, relatively lower resistance towards Ciprofloxacin (25%) and Meropenem (40%) were recorded. Some of the risk factors identified for carriages of MDR strains were self-medication (p: 0.001, C.I: 3.01 - 8.86, O.R: 5.17) and non-completion of dosage (p: 0.12, C.I: 0.9 - 2.5, O.R: 1.5).

Effect of Antibiotic Consumption on Resistance of <i>Pseudomonas aeruginosa</i>Isolated from Lebanese Patients with Emphasis on MBL Production

The relationship between antibiotic consumption and resistance has been widely evaluated. Pseudomonas aeruginosa is one of the most important opportunistic pathogens in the nosocomial setting, and its resistance to antibiotics is increaseing. Production of metallo-β-lactamases (MBLs) is currently the most fearful resistance mechanism due to the potential of dissemination. This study aimed to evaluate the correlation between antibiotic consumption (expressed in DDD/100 bed days) and resistance (expressed in % of isolates and patients) in different time periods for P. aeruginosa between 2006 and 2009 at Saint George Hospital University Medical Center (SGH-UMC), Beirut. Pearson correlation coefficients (r) were calculated and linear regression was performed. Detection of MBL-producing Imipenem resistant P. aeruginosa (IRPA) isolates between 2008 and 2009 was performed using three MBL screening methods: MBL Etest?, Imipenem/EDTA combined disk test and EDTA disk potentiation with four cephalosporins. The modified Hodge test was also performed. From 2006 till 2009, there was a trend of increasing resistance of P. aeruginosa to all antibiotics, and the highest % of resistance was for Ofloxacin. Concerning resistance expressed by isolates, high correlation coefficients resulted among Imipenem, Ciprofloxacin and Tazobactam consumption and resistance to these agents in the same year correlation;Ceftazidime and Ofloxacin consumption and resistance in the next year correlation;Gentamicin and Ofloxacin consumption and the change in resistance (ΔR). Concerning resistance expressed by patients, results were similar except for Ceftazidime and Ofloxacin correlation in the next year correlation. In MBL screening, three isolates gave accordance among 4 methods which showed a positive result. The correlation between antibiotic consumption and resistance is highly dependent on the kind of antibiotic, the organism and the time of correlation. Various MBL screening phenotypic methods on one isolate can increase accuracy and eliminate false positive and negative results.

Resistance to Beta Lactam Antibiotics of <i>Pseudomonas aeruginosa</i>Isolated in Community Infections within HIV Infected Persons in Lomé-Togo

Objective: Describe resistance to beta lactam antibiotics of Pseudomonas aeruginosa in community infection within HIV-1 infected persons. Methods: We have studied prospectively from June 15th to December 31st 2013 inthe Clinic Hotel-Dieu and NGO VISA of Lomé, adult HIV-1 infected patients under anti retroviral therapy combining tenofovir, lamivudine and efavirenz for at least one year. The technique of agar diffusion susceptibility using discs of Ticarcillin + clavulanic acid is used to study the β-lactamase production. The diagnosis of species was performed by the chloroform test and the test for sensitivity to kanamycin and colistin. Results: Thirty five strains of Pseudomonas aeruginosa were obtained. The T-lymphocytes CD4 mediane was 575 cells/mm3 of blood. Urine represented 15 cases, skin abscesses 11 cases, externa suppurate otitis 7 cases and vaginal swab for 2 cases. The phenotypes were: wild phenotypes 23 cases (65.7%), resistant phenotypes 12 cases. Among resistant phenotypes, 4 were complex phenotype;5 were ESBL phenotypes;2 were hyper productive cephalosporinases phenotypes and 1 was a specific phenotype with impermeability to imipenem. Conclusion: The acquisition of resistance of Pseudomonas aeruginosa to beta lactam antibiotics in community infections among HIV-1 infected person incentives controls and promotes the rational use of antibiotics.

Investigation of Pseudomonas aeruginosa Resistance Pattern against Antibiotics in Clinical Samples from Iranian Educational Hospital

Pseudomonas aeruginosa (P. aeroginosa) is one of the opportunistic pathogens, which is the main cause of prevalent hospital infections worldwide. The aim of this study was to determine the prevalence of antibiotic resistance pattern against P. aeroginosa from clinical samples in our population. This study was performed during March 2009 to September 2011. During this period 233 clinical isolated samples from hospital patients were examined. In these studies, different strains of P. aeroginosa were isolated from samples, then microbiologically tested. Bacterial susceptibility was performed by the disc-diffusion tests with Kirby Baur disc diffusion tests in Muller-Hinto environment. Our results showed maximum antibiotic resistance (99.5%) of P. aeruginosa against Trimetoprime Solfametoxasole and Ciprofloxacin (55.33%), Amikacin (61%), Imipenem (33%), which were identified as the most effective antibiotics in this study. In conclusion, indeed most Pseudomonas aeruginosa strains infections are treated as soon as possible due to their severe resistance against antibiotics. So, we have to apply an accurate antibiotic treatment discipline, according to the finding, based on antibiogram, in order to prevent its spread and also, monitoring and optimization of antimicrobial use should be considered carefully.

Clinical Distribution and Drug Resistance of 224 Strains of Pseudomonas Aeruginosa

Objective:To provide evidence for a rational and effective prevention and treatment of Pseudomonas aeruginosa,the clinical characteristics and the resistance to various antibiotics of were investigated.Methods:A retrospective analysis of 224 strains of Pseudomonas aeruginosa isolated from various specimens from various clinical departments of our hospital(April 1,2018 to June 31,2019)were conducted.Identification and drug susceptibility test of isolated strains was performed using a fully automatic bacterial identification analyzer(MicroScan WalkAway-96 plus),and data analysis was performed using WH0NET5.6 software.Results:Among all the bacteria isolated in our hospital during the above period,Pseudomonas aeruginosa accounted for 10.09% of them all and 12.57% of Gram-negative bacilli,respectively.These isolates were mainly derived from sputum specimens(68.75%),mainly from male patients(70.54%),and mostly 61-70(27.23%)or 51-60(22.77%)years old.Pseudomonas aeruginosa isolates are mainly from Rehabilitation Ward,ICU,and Liver Transplantation Unit,accounted for 29.91%,12.95% and 10.27% of all isolates,respectively.The sensitivity of Pseudomonas aeruginosa to various antibacterial drugs,in the order of high to low were carbapenems,aztreonam,quinolones,cephalosporins,piperacillin/tazobactam,aminoglycoside,with a lowest resistance rate(2.4%)to amikacin and a highest resistance rate to imipenem(33.0%).Conclusion:The isolation rate of Pseudomonas aeruginosa was relatively stable during the study period,and among all the P.aeruginosa detected,most of them were from the respiratory secretions of elderly male patients.The resistance rate of Pseudomonas aeruginosa isolates to various antibiotics is mainly within 30%.Clinical units such as Rehabilitation Ward,ICU,and Liver Transplantation Unit have a high detection rate;therefore,these departments should be monitored in a focused manner.Our research provides a scientific basis for the rational use of antibiotics and a better control of Pseudomonas aeruginosa infection.

Prevalence of Class 1 Integron, Resistance Gene Cassettes and Antimicrobial Susceptibility Profiles among Isolates of Pseudomonas aeruginosa in Iran

Pseudomonas aeruginosa is one of the most important opportunistic human pathogens worldwide. High prevalence of Multi Drug Resistant P. aeruginosa (MDRPa) in Iran is a serious problem for antimicrobial therapy. Several studies have reported the MDRPa in Europe and Asia. Due to the use of broad-spectrum antibiotics, bacterial resistance is increasing in Iran, located in Middle East. The present cross-sectional study was designed to investigate the prevalence of class1 integron, resistance gene cassettes and antimicrobial susceptibility profiles among isolates of P. aeruginosa in Al-Zahra Hospital, Isfahan City, central part of Iran from Jan-Sep 2014. The aim of this study was to determine the antimicrobial susceptibility, the prevalence of Class1 integron, resistance gene a measuring in Iran. A total of 231 P. aeruginosa isolates were collected from clinical specimens including urine (50.6%), tracheal tube (25.5%), wound (13.4%), blood (6.1%), catheter (2.2%), cerebrospinal fluid (1.7%) and sputum (0.4%) isolates from hospitalized patients (mean age: 50.27 ± 24.12 years).The majority of patients (68%) were male. Isolates were collected from different parts of the hospital as follows: ICU, Internal Medicine, Emergency care, Pediatrics, Nephrology, Transplant Center, General surgery and Infectious. Revealed data show a high rate of MDR P. aeruginosa isolates in the studied area;also, the result signifies the spread of aadA6 among clinical isolates in hospitalized patients.

Detection of the Mex Efflux Pumps in <i>Pseudomonas</i><i>aeruginosa</i>by Using a Combined Resistance-Phenotypic Markers and Multiplex RT-PCR

The aim of this study was to detect the expression of 4 clinically-important efflux pumps in the Resistance-Nodulation-Cell Division (RND) family including MexAB-OprM, MexXY, MexCD-OprJ and MexEF-OprN in Pseudomonas aeruginosa using a combination of resistance-phenotypic markers and multiplex RT-PCR (mRT-PCR). The antibiotic substrates specific for each Mex systems were used as phenotypic markers including carbenicillin, MexAB-OprM, erythromycin, MexCD-OprJ, norfloxacin and imipenem, MexEF-OprN and gentamicin, MexXY-OprM. The methods were validated with reference strains with known genotypes of the Mex systems and the potential applicability in clinical practice was tested with clinical isolates. The results for the reference strains support that the combination of resistance phenotype and mRT-PCR is a potential-attractive method for diagnosis of efflux-mediated resistance in P. aeruginosa. Further development to make it more practical for clinical use and study in a larger number of clinical isolates is required.

Role of MexA-MexB-OprM Efflux Pump System in Chronic Pseudomonas Aeruginosa Pulmonary Infection in Mice

In order to investigate the role of the MexA-MexB-OprM efflux pump system in the pathogenesis of Pseudomonas aeruginosa(PA)-induced pulmonary infection,pulmonary infection models were established by intratracheal injection of K767(wild type),nalB(MexA-MexB-OprM up-regulated mutant),and △m exB(knockout) strains,separately.All mice were treated with Meropenem(intraperitoneal injection,100 mg/kg body weight,twice every day),and strain-related pathology,bacteria count,cytokine level,myeloperoxidase(MPO,indicator of neutrophil recruitment) activity,and macrophage inflammatory protein-2(MIP-2) expression were evaluated at early(3rd day post-infection) and late(7th and 14th day post-infection) stages of infection.E-test showed that △mexB was more significantly sensitive to panipenan(ETP),meropenem(MP) and imipenem(IP) than K767 and nalB strains.There was no significant difference in sensitivity to cefepime(TM) among the three stains.In contrast to the K767 and nalB groups,the △ mexB group showed decreased bacteria burden over time and less extensive pathological change.Additionally,MPO activity and levels of inflammatory cytokines(IL-1b,IL-12,and TNF-α) were increased at the early stage(day 3) and decreased at the later stage(day 14).Serum MIP-2 expression level was steadily increased in all three groups from early to late stages,but significantly higher in △m exB group than in K767 and nalB groups(P<0.05).In conclusion,the MexA-MexB-OprM efflux pump system might play an important role in PA-induced chronic pulmonary infection.High expression of the MexA-MexB-OprM efflux pump could increase antibacterial resistance and promote infection.