Characterization of genotypes and antimicrobial resistance profiles of clinical isolates of Shigella from patients in the southern region of Iran.

BACKGROUND: Shigella spp., which are facultative anaerobic bacilli within the Enterobacteriaceae family, present a significant public health burden due to their role as prominent contributors to diarrheal diseases worldwide. A molecular analysis can facilitate the identification and assessment of outbreaks involving this bacterium. So, we aimed to investigate the antibiotic susceptibility pattern and clonal relatedness of clinical Shigella spp. isolates obtained from patients with diarrhea in Hormozgan province, South of Iran. METHODS: From 2019 to 2021, a cross-sectional investigation was conducted on 448 stool samples obtained from patients who were experiencing diarrhea, in the southern region of Iran. Shigella spp. isolates were identified based on biochemical and serological tests. All Shigella species were verified using species-specific polymerase chain reaction (PCR), followed by susceptibility testing to antimicrobial agents. Subsequently, genotyping of all Shigella species was conducted using ERIC-PCR. RESULTS: Out of a total of 448 stool samples, the presence of Shigella was detected in 62 cases, accounting for a prevalence rate of 13.84%. Among the identified isolates, the majority were attributed to S. flexneri, representing 53.23% of the cases. This was followed by S. sonnei at 24.19% and S. boydii at 22.58%. Notably, no instances of S. dysenteriae were found. The highest prevalence of Shigella isolates was observed in infants and children under the age of five. A significant proportion of the identified isolates demonstrated resistance to various antibiotics. Specifically, high resistance rates were noted for ampicillin (90.78%), piperacillin-tazobactam (87.1%), cefixime (83.87%), trimethoprim-sulfamethoxazole (83.87%), cefotaxime (82.26%), and ceftriaxone (80.65%). In addition, a substantial number (87.1%) of the isolates exhibited a multidrug-resistant (MDR) phenotype. Using the ERIC-PCR method, a total of 11 clusters and 6 distinct single types were identified among all the Shigella isolates. CONCLUSION: A notable occurrence of antibiotic-resistant Shigella species has been noted, with multi-drug resistant (MDR) strains presenting an increasing challenge for treating shigellosis worldwide, and this includes Iran. Techniques such as ERIC-PCR are useful for assessing the genetic variation and connections between Shigella strains, which indirectly contributes to understanding antimicrobial resistance patterns. Further research is needed to explore the specific correlation between resistance genes and ERIC genotyping patterns in Shigella strains.

Bacteriological characteristics of hypervirulent Klebsiella pneumoniae rmpA gene (hvKp-rmpA)-harboring strains in the south of Iran.

Background and Objectives: To provide data on the occurrence of classical K. pneumoniae (cKp) and hypervirulent Klebsiella pneumoniae (hvKp) strains harboring the gene encoding regulator of mucoid phenotype A (rmpA) and evaluated characteristics of virulence biomarkers, carbapenemase, extended-spectrum-ß-lactamase (ESBL)-producing, and capsule serotypes among K. pneumoniae clinical isolates collected in the south of Iran. Materials and Methods: A total of 400 K. pneumoniae isolates were collected. First, the K. pneumoniae isolates were screened for rmpA gene by PCR, and then they were characterized for the presence of the virulence genes (pagO, iucA, iroB, luxR), capsular serotype genes (K1, K2, K5, K20, K54, and K57), carbapenemase (bla NDM, bla IMP, bla VIM, bla KPC, bla SPM, bla OXA-48, and bla OXA-181) and ESBL (bla CTX-M, bla SHV and bla TEM) genes. For all K. pneumoniae isolates phenotypic tests include of string test and disk diffusion test were performed. Results: In total, 16 (4%) hvKp-rmpA+ and 384 (96%) cKp were observed. Of hvKp-rmpA+ strains, 16 (100%) were carried pagO, iroB, and luxR genes, and 13 (81.3%) strains harbored iucA gene. The most prevalent capsular type genes were K1 (62%) and K2 (19%) in hvKp-rmpA+ strains. The incidence of bla SHV gene in hvKp and cKp was 94% (15/16) and 87.5% (336/384), respectively. The cKp isolates carried bla NDM (30/384; 7.8%) gene. Conclusion: Our data suggest that the incidence of hvKp was low. Also, hvKp-rmpA+ strains have less antibiotic resistance than cKp isolates. Serotypes K1 and K2, and bla SHV gene were strongly associated with hvKp-rmpA+.

Comparison of a Novel Herbal Medicine and Omeprazole in the Treatment of Functional Dyspepsia: A Randomized Double-Blinded Clinical Trial.

BACKGROUND: The Trachyspermum ammi L. (TA), Anethum graveolens L. (AG), and Zataria multiflora Boiss (ZM) herbal oils are among the most used herbal products in traditional medicine as the antiseptic, anesthetic, carminative, and antispasmodic. However, there are no clinical studies to evaluate the efficacy of the herbs mentioned in the treatment of functional dyspepsia (FD). This study was designed to appraise the efficacy and safety of a novel herbal medicine consisting of ZM, AG, and TA essential oils compared to omeprazole in FD treatment. METHODS: The present study was a randomized double-blind clinical trial with parallel groups in Iran. Patients in control and intervention arms received omeprazole 20 mg once a day and 250 mg soft-gel capsules containing 180 mg of essential oils of ZM, AG, and TA twice a day for two weeks, respectively. The primary outcome was the sufficient response rate in the postprandial distress syndrome (PDS) and/or epigastric pain syndrome (EPS) at the end of the intervention. Secondary outcomes were the improvement rate in the PDS, EPS, Gastrointestinal Symptom Rating Scale (GSRS), and quality of life scores. Also, safety and tolerability were assessed. RESULTS: The within-group comparison of EPS, PDS, total GSRS, GSRS Pain, and GSRS Dyspepsia scores with that at the end of the treatment indicated a significant reduction in both control and intervention groups (p < 0.001). However, after two weeks of treatment, the herbal medication and omeprazole arms were significantly different in the sufficient response rate based on PDS (p < 0.01) and EPS (p < 0.05) scores (78.3% (18/23) and 73.7% (14/19) in the intervention group vs. 36.4% (8/22) and 40.9% (9/22) in the control group). Also, the mean reduction in EPS (p < 0.05), PDS (p < 0.01), and GSRS (p < 0.001) scores after treatment was significantly higher in the intervention group than control group. CONCLUSION: Based on the study findings, this herbal medicine can be considered as an appropriate treatment of FD. However, a larger multicenter trial is needed to confirm the results of the trial.

Antimicrobial resistance patterns and their encoding genes among clinical isolates of Acinetobacter baumannii in Ahvaz, Southwest Iran.

Acinetobacter baumannii is one of the most important organisms in nosocomial infections. Antibiotic resistance in this bacterium causes many problems in treating patients. This study aimed to investigate antibiotic resistance patterns and resistance-related, genes in clinical isolates of Acinetobacter baumannii. This descriptive study was conducted on 124 isolates of Acinetobacter baumannii collected from clinical samples in two teaching hospitals in Ahvaz. The antibiotic resistance pattern was determined by disk diffusion. The presence of genes coding for antibiotic resistance was determined using the polymerase chain reaction method. Out of 124 isolates, the highest rate of resistance was observed for rifampin (96.8%). The resistance rate for imipenem, meropenem, colistin, and polymyxin-B were 78.2%, 73.4%, 0.8% and 0.8%, respectively. The distribution of qnrA, qnrB, qnrS, Tet A, TetB, and Sul1genes were 52.6%, 0%, 3.2%, 93.5% 69.2%, and 6.42%, respectively. High prevalence of tetA, tetB, and qnrA genes among Acinetobacter baumannii isolated strains in this study indicate the important role of these genes in multidrug resistance in this bacteria. • Acinetobacter baumannii is an important human pathogen that has attracted the attention of many researchers Antibiotic resistance in this bacterium causes many problems in treating patients. • The resistance rate for imipenem, meropenem, colistin, and polymyxin-B were 78.2%, 73.4%, 0.8% and 0.8%, respectively. The distribution of qnrA, qnrB, qnrS, Tet A, TetB, and Sul1genes were 52.6%, 0%, 3.2%, 93.5% 69.2%, and 6.42%, respectively.

Investigating the frequency of free-living amoeba in water resources with emphasis on Acanthamoeba in Bandar Abbas city, Hormozgan province, Iran in 2019-2020.

OBJECTIVE: These amoebas can cause dangerous illnesses when they accidentally enter the human body, so it is necessary to determine various forms of organisms in water resources to prevent the danger they can cause and risks to human health. Currently, in Bandar Abbas, there is no sufficient information about the distribution of Acanthamoeba, and we intended to study its frequency and determine the related genotypes. RESULTS: Out of 83 water samples collected from different resources in the city, 31 plates (37.3%) were found to be positive for free-living amoebae. Of these, five were identified as Acanthamoeba (6%) by culture method and 8 (9.6%) by molecular method. Positive sample sequence analysis enabled us to distinguish two genotypes of T4 (7 cases) and T15 (1 case) in this study.

Efficacy and Safety of a Novel Herbal Medicine in the Treatment of Irritable Bowel Syndrome: A Randomized Double-Blinded Clinical Trial.

BACKGROUND: The unresponsiveness to conventional pharmacological treatments and their side effects have led patients with irritable bowel syndrome (IBS) to use complementary and alternative medicine such as herbal remedies. Beside, Zataria multiflora Boiss (ZM), Trachyspermum ammi L. (TA), and Anethum graveolens L. (AG) are being used as an antiseptic, carminative, and antispasmodic in traditional medicine. This trial investigated the efficacy and safety of a combination of ZM, AG, and TA essential oils in the treatment of IBS. METHOD: The present study was a randomized double-blind clinical trial with parallel groups in Iran. Patients in the control arm received three tablets of 10 mg hyoscine butylbromide daily for two weeks, and the intervention arm was daily treated with two 250 mg softgel capsules containing 180 mg of essential oils of ZM, AG, and TA for two weeks. Primary outcomes were the response rates based on the IBS Symptom Severity Scale (IBS-SSS), IBS Adequate Relief (IBS-AR), and IBS Global Assessment Improvement (IBS-GAI) at the end and two weeks after the end of the intervention. Secondary outcomes were the improvement rates in IBS-SSS scores, improving the quality of life, safety, and tolerability. RESULTS: The posttreatment improvement percentage based on IBS-AR, IBS-GAI, and IBS-SSS scales was 83.9%, 75%, and 87% in the intervention group and 37.9%, 27.5%, and 34.4% in the control group, respectively (P < 0.001). Also, the improvement of the quality of life in the herbal medicine arm was significantly more than that in the control arm (P < 0.001). CONCLUSIONS: According to the results, the herbal medicine investigated in this study can be considered an appropriate alternative treatment for IBS.

Frequency and Antimicrobial Susceptibility Patterns of Diabetic Foot Infection of Patients from Bandar Abbas District, Southern Iran.

Diabetic foot infection is among the most common complications of diabetes mellitus which significantly causes hospitalization and is the most prevalent etiology of nontraumatic amputation worldwide. The current study aimed at assessing the frequency and antimicrobial susceptibility patterns of diabetic foot infection of patients from the Bandar Abbas area, in the south of Iran. In this study, a total of 83 diabetic patients with diabetic infected foot wounds referring to Shahid Mohammadi Hospital, Bandar Abbas, from 2017 to 2018 were assessed. Samples were obtained from wound sites and evaluated by aerobic culture and also an antibiogram test for antibiotic susceptibility. Factors including age, sex, type of diabetes, the medication used for diabetes, previous history of diabetic foot infection, duration of wound incidence, fever, and laboratory indices were recorded for each subject. The most prevalent detected bacteria were Escherichia coli (20.5%), Enterococcus sp. (16.9%), Klebsiella sp. (12%), Staphylococcus aureus (8.4%), Enterobacter sp. (7.2%), and Acinetobacter sp. (6%). The results of antibiogram tests revealed the most and the least antibiotic sensitivity for E. coli sp. as meropenem and ciprofloxacin, for Enterococcus sp. as gentamicin and ciprofloxacin, for Klebsiella sp. as amikacin and cotrimoxazole, and for Enterobacter sp. as cotrimoxazole and both amikacin and ciprofloxacin. Staphylococcus aureus was sensitive to vancomycin and doxycycline, and Acinetobacter sp. was 100% resistant to all antibiotics except amikacin and gentamycin. A significant statistical association was found between the C-reactive protein and the patients' diabetic foot infection organisms (P=0.019). Findings of the study revealed E. coli sp. as the most common bacteria which are infecting the foot lesions in the studied population. The highest antibiotic susceptibility was seen for vancomycin, linezolid, and carbapenem.

Molecular detection of virulence factors and biofilm formation in Pseudomonas aeruginosa obtained from different clinical specimens in Bandar Abbas.

BACKGROUND AND OBJECTIVES: Pseudomonas aeruginosa is a ubiquitous opportunistic pathogen. The presence of several virulence factors such as exotoxin and exoenzyme genes and biofilm may contribute to its pathogenicity. The purpose of this study was to investigate the presence of toxA, exoU and exoS, the determination of biofilm production and antimicrobial susceptibility patterns among clinical isolates of P. aeruginosa. MATERIALS AND METHODS: In this study, 75 isolates of P. aeruginosa were recovered from various clinical specimens. Antimicrobial susceptibility pattern of isolates were identified. Virulence genes toxA, exoU and exoS were determined using PCR. The ability of biofilm production was assessed. RESULTS: Antimicrobial susceptibility test showed that 12 strains were resistant to more than 8 antibiotics (17.14%). The most effective antibiotic was colistin as 98.6% of isolates were sensitive. The frequencies of exoU and exoS genes were detected as 36.6% and 55.7%, respectively. In addition, 98.6% of the isolates were biofilm producers. Exotoxin A was detected in sixty-eight isolates (95.7%). CONCLUSION: The findings of this study showed that, the presence of P. aeruginosa exotoxin and exoenzyme genes, particularly, the exoU gene is the most common virulence factors in the bacterial isolates from urine samples. Biofilm is a serious challenge in the treatment of P. aeruginosa infection.

Prevalence of nontuberculous mycobacteria and high efficacy of d-cycloserine and its synergistic effect with clarithromycin against Mycobacterium fortuitum and Mycobacterium abscessus.

BACKGROUND: The prevalence of pulmonary disease caused by nontuberculous mycobacteria (NTM) is reportedly on the rise in the world. Some of the species are resistant to various antibiotics; hence, limited treatment options are available. The aims of this study were to investigate the prevalence of NTM and to determine the effect of d-cycloserine against Mycobacterium fortuitum and Mycobacterium abscessus isolated from clinical specimens to find out the synergistic effect of d-cycloserine and clarithromycin. METHODS: A total of 95 nonduplicate pulmonary isolates of NTM were collected from three major Regional Tuberculosis (TB) Centers. NTM isolates were identified by conventional tests and PCR sequence analysis of the rpoB gene. PCR sequencing of erm-41 was performed for detecting the inducible resistance to macrolides. In vitro susceptibilities and activities of d-cycloserine-clarithromycin combinations were accessed using the broth microdilution method. RESULTS: Among 714-positive acid-fast bacilli from TB-suspected cases, 95 isolates were identified as NTM (13.3%). The prevalence of identified isolates was as follows: M. fortuitum 46 (48.4%), Mycobacterium simiae 16 (16.8%), Mycobacterium kansasii 15 (15.7%), M. abscessus 7 (7.3%), Mycobacterium thermoresistibile 4 (4.2%), Mycobacterium elephantis 3 (3.2%), Mycobacterium porcinum 2 (2.1%), and Mycobacterium chimaera 2 (2.1%). In addition, rpoB sequence analysis could identify all NTM isolates. The effect of d-cycloserine was better than that of clarithromycin. The synergistic effect of d-cycloserine with clarithromycin was observed for six (100%) and five (71.5%) strains of M. fortuitum and M. abscessus, respectively. CONCLUSION: In the present study, we demonstrated a wide range of NTM in processed samples from different provinces of Iran. Our observations indicated that d-cycloserine was very active against M. abscessus and M. fortuitum; hence, d-cycloserine, either alone or in combination with clarithromycin, may be promising for the treatment of M. abscessus- and M. fortuitum-associated diseases.

Integron types, antimicrobial resistance genes, virulence gene profile, alginate production and biofilm formation in Iranian cystic fibrosis Pseudomonas aeruginosa isolates.

Cystic fibrosis (CF) patients commonly suffer from continuous and recurrent lung infections caused by Pseudomonas aeruginosa, the dominant pathogen in CF airways. This study aimed to determine the integron types, gene cassettes, virulence determinants, ß-lactam resistance genes, biofilm formation and alginate production in P. aeruginosa isolated from Iranian CF patients. A total of 143 P. aeruginosa isolates were obtained from CF patients. Susceptibility of isolates to different antimicrobials was evaluated by disc diffusion method. ESBL, MBL and KPC production was assessed. Congo red agar and tissue culture plates were used for evaluation of biofilm formation. Alginate production was determined using the Carbazole assay. Integrase genes, resistance determinants (ESBLs, MBLs and KPC) and genes encoding virulence factors were evaluated by PCR. All isolates were susceptible to colistin, piperacillin-tazobactam and ticarcillin; 8.4% of isolates were considered as MDR phenotype. Out of 6.3% IPM-resistant isolates, prevalence of virulence genes was as follows: lasB (100%) and plcB (100%), plcH (96.5%). Biofilm formation and alginate production ability were found in 54.5% of isolates. The prevalence of the alginate-encoding genes was 92.3%, 86.7% and 67.1% for algD, algU and algL genes, respectively. PpyR, pslA and pelA genes were detected in 98.6%, 89.5% and 57.3% of the isolates, respectively. The high prevalence of colonization in CF lungs may increase the pathogenicity of P. aeruginosa due to their adhesion and protective properties caused by biofilm- and alginate-production. LasB, plcB, plcH, exoS, toxA, algD, ppyR and pslA genes were predominant in CF P. aeruginosa strains.

Dual infections of two carbapenemase-producing Acinetobacter baumannii clinical strains isolated from the same blood culture sample of a patient in Iran.

In this study, the draft genome sequences of two different carbapenem-resistant Acinetobacter baumannii clinical strains isolated from the same blood culture sample of an Iranian patient were determined. The strain A. baumannii 554S harbouring blaoxa72 gene belonged to ST 307 whereas A. baumannii 554L carrying blaoxa23 gene belonged to ST 2. We found that this sample contains two different isolates of A. baumannii, each phenotypically and genetically different.

Growth Rate and Biofilm Formation Ability of Clinical and Laboratory-Evolved Colistin-Resistant Strains of Acinetobacter baumannii.

Two different mechanisms of resistance to colistin in Acinetobacter baumannii have been described. The first involves the total loss of lipopolysaccharide (LPS) due to mutations in the lpxACD operon, which is involved in the lipid A biosynthesis pathway. The second entails the addition of ethanolamine to the lipid A of the LPS resulting from mutations in the PmrAB two-component system. To evaluate the impact of colistin resistance-associated mutations on antimicrobial resistance and virulence properties, four pairs of clinical and laboratory-evolved colistin-susceptible/colistin-resistant (ColS/ColR) A. baumannii isolates were used. Antimicrobial susceptibility, surface motility, in vitro and in vivo biofilm-forming capacity, in vitro and in vivo expression levels of biofilm-associated genes, and in vitro growth rate were analyzed in these strains. Growth rate, in vitro and in vivo biofilm formation ability, as well as expression levels of biofilm-associated gene were reduced in ColR LPS-deficient isolate (the lpxD mutant) when compared with its ColS partner, whereas there were not such differences between LPS-modified isolates (the pmrB mutants) and their parental isolates. Mutation in lpxD was accompanied by a greater reduction in minimum inhibitory concentrations of azithromycin, vancomycin, and rifampin than mutation in pmrB. Besides, loss of LPS was associated with a significant reduction in surface motility without any change in expression of type IV pili. Collectively, colistin resistance through loss of LPS causes a more considerable cost in biological features such as growth rate, motility, and biofilm formation capacity relative to LPS modification. Therefore, ColR LPS-modified strains are more likely to spread and transmit from one patient to another in hospital settings, which results in more complex treatment and control.

Correction to: Acquisition of Tn6018-3' CS regions increases colistin MICs against Acinetobacter baumannii isolates harboring new variants of AbaRs.

The published online version of this article contained a mistake. The correct affiliation of Alireza Ekrami should have been "Infectious and Tropical Diseases Research Center, Health Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran" . The authors regret this error.

Investigating of four main carbapenem-resistance mechanisms in high-level carbapenem resistant Pseudomonas aeruginosa isolated from burn patients.

BACKGROUND: Pseudomonas aeruginosa is an opportunistic pathogen involved in many infections. Carbapenem-resistant P.aeruginosa has emerged as an important cause of infection in different hospitals worldwide. We aimed to determine frequencies of the four main resistance mechanisms [metallo-beta lactamase (MBL) production (blaIMP, blaVIM, blaSPM and blaNDM), overproduction of the MexAB-OprM and MexXY efflux pumps, overproduction of chromosome-encoded AmpC ß-lactamase, and reduced OprD expression] in high-level carbapenem-resistant P.aeruginosa isolated from patients with burns. METHODS: In a descriptive study, 107 P. aeruginosa isolates were collected from patients with burn injuries and tested for antibiotic susceptibility, by an E-test for carbapenems, an E-test for metallo-ß-lactamase producer isolates, and PCR to detect MBL genes. Furthermore, high-level carbapenem-resistant isolates were tested by real-time PCR for the expression levels of the mexB, mexY, ampC, and oprD genes. RESULTS: Amongst all P. aeruginosa isolates, 78.5%, 46.7%, and 15% were imipenem-, meropenem-, and doripenem-resistant, respectively; 72% of isolates were multidrug-resistant. The blaIMP and blaVIM genes were detected in 17.9% and 1.2% of isolates; respectively. The blaSPM and blaNDM genes were not observed. Among the resistant isolates, mexB overexpression (63.2%) was the most frequent mechanism, followed by mexY overexpression (52.6%), ampC overexpression (36.8%), and reduced oprD expression (21.1%). CONCLUSION: Emerging antimicrobial resistance in burn wound bacterial pathogens is a serious therapeutic challenge for clinicians. In the present study, most of the isolates were MDR. This finding indicated an alarming spread of resistant isolates and suggested that infection control strategies should be considered. Resistance to carbapenems is influenced by several factors, not all of which were evaluated in our study; however, the results showed that production of MBLs and overexpression of the mexB gene were the most frequent mechanisms in carbapenem-resistant isolates.

Identification of Carbapenem-Resistant Klebsiella pneumoniae with Emphasis on New Delhi Metallo-Beta-Lactamase-1 (blaNDM-1) in Bandar Abbas, South of Iran.

BACKGROUND AND OBJECTIVE: The spread of carbapenem-resistant Klebsiella pneumoniae especially blaNDM-1-carrying isolates is a great concern worldwide. In this study we describe the molecular basis of carbapenem-resistant K. pneumoniae in three teaching hospitals at Bandar Abbas, south of Iran. MATERIALS AND METHODS: A total of 170 nonduplicate clinical isolates of K. pneumoniae were investigated. Antimicrobial susceptibility test was performed by disc diffusion method. PCR was carried out for detection of carbapenemase (blaKPC, blaIMP, blaVIM, blaNDM, blaSPM, blaOXA-48, and blaOXA-181) and extended-spectrum ß-lactamase (blaCTX-M, blaSHV, blaTEM, blaVEB, blaGES, and blaPER). Clonal relatedness of blaNDM-1-positive isolates was evaluated by multilocus sequence typing (MLST). RESULTS: Tigecycline was the most effective antimicrobial agent with 96.5% susceptibility. In addition, 6.5% of the isolates were carbapenem resistant. BlaNDM-1 was identified in four isolates (isolate A-D) and all of them were multidrug-resistant. MLST revealed that blaNDM-1-positive isolates were clonally related and belonged to two distinct clonal complexes, including sequence type (ST) 13 and ST 392. In addition to blaNDM-1, isolate A coharbored blaSHV-11, blaCTX-M-15, and blaTEM-1, isolate B harbored blaSHV-11 and blaCTX-M-15, and isolates C and D contained both blaSHV-1 and blaCTX-M-15. CONCLUSION: Our results indicate that NDM-1-producing K. pneumoniae ST 13 and ST 392 are disseminated in our region. Moreover, one of our major concerns is that these isolates may be more prevalent in the near future. Tracking and urgent intervention is necessary for control and prevention of these resistant isolates.

Dissemination of carbapenem-resistant Acinetobacter baumannii in patients with burn injuries.

BACKGROUND: Carbapenem-resistant Acinetobacter baumannii has emerged as an important cause of infection in burn patients. This study aimed to characterize the antimicrobial susceptibility pattern, determine the prevalence of oxacillinase and metallo-beta-lactamase (MBL) genes, and type the A. baumannii isolates obtained from burn patients. METHODS: During a 1-year period, a total of 40 nonduplicated isolates of A. baumannii were obtained from burn patients who were hospitalized in the Taleghani Burn Hospital in Ahvaz, in the southwest of Iran. Testing for antimicrobial susceptibility was carried out by disk diffusion and E-test. To screen MBL production, a double disk synergy and MBL E-test were performed. The presence of blaOXA-23-like, blaOXA-24-like, blaOXA-51-like and blaOXA-58-like, blaVIM, blaIMP and blaSPM, and blaNDM was sought by polymerase chain reaction (PCR). Repetitive extragenic palindromic sequence-based PCR was carried out for determination of isolates clonality. RESULTS: Overall, 92.5% of isolates were carbapenem-resistant. Polymyxin B, colistin, and ampicillin-sulbactam were the most effective agents in vitro, with a susceptibility rate of 100%, 97.5%, and 72.5%, respectively. According to the double disk synergy and E-test, 55.6% and 97.3% of isolates were MBL producers, respectively. Furthermore, 70% of isolates harbored blaOXA-23-like and 20% were positive for blaOXA-24-like. However, no encoding genes were detected for blaVIM, blaIMP and blaSPM, blaNDM, and blaOXA-58-like. Repetitive extragenic palindromic sequence-based PCR revealed that carbapenem-resistant isolates belonged to four clones, including A, B, C, and D; the predominant clones were B and C. CONCLUSION: The rate of carbapenem resistance was high, and it appeared that blaOXA-23-like and blaOXA-24-like contributed to the carbapenem resistance of A. baumannii isolates. This result suggests that the two predominant clones of A. baumannii were spread among burn patients. In order to prevent future dissemination of resistant isolates among burn patients, an effective infection control plan is necessary.

Acquisition of Tn6018-3' CS regions increases colistin MICs against Acinetobacter baumannii isolates harboring new variants of AbaRs.

Colistin is the last hope to treat extensively drug resistance (XDR) Acinetobacter baumannii (A. baumannii) infections, but resistance to colistin is currently reported in clinical centers all over the world. Here, we studied two colistin-resistant A. baumannii isolates with a difference in minimum inhibitory concentrations (MICs) that were isolated from a single burn patient during treatment in the hospitalization period. The international clonal (IC) lineage, multilocus sequence typing (MLST), and multiple loci variable number tandem repeat (VNTR) analysis (MLVA) typing were used to characterize the relatedness of A. baumannii isolates. Lipopolysaccharides (LPS) and PmrAB system analysis by PCR sequencing, polyacrylamide gel electrophoresis (PAGE), and real-time PCR were performed to determine the intactness and probable modifications of the LPS as the main resistance mechanisms to colistin. A combination of PCR, sequencing, and restriction fragment length polymorphism (RFLP) was used for A. baumannii resistance islands (AbaR) mapping as resistance-determinant reservoirs. Two isolates were identical at all MLST and VNTR marker loci that indicated the isolates were the same strain. In comparison to colistin-heteroresistant A. baumannii strain TEH267 (MIC = 1.5 mg/L), colistin-resistant A. baumannii strain TEH273 (MIC ≥256 mg/L) acquired two genomic regions including Tn6018-topA sequence and topA sequence-3' CS in its AbaR structure containing ispA and cadA genes which, it would appear, could be associated with eightfold increase in colistin MIC. Both isolates had new variants of AbaR-like structures which could be derivatives of the typical AbaR3. According to the results of this study, AbaRs could be associated with an increase in MIC to colistin.

Plasmid borne Carbapenem-Hydrolyzing Class D ß-Lactamases (CHDLs) and AdeABC efflux pump conferring carbapenem-tigecycline resistance among Acinetobacter baumannii isolates harboring TnAbaRs.

Here we studied the prevalence and mechanisms of simultaneous resistance to carbapenem and tigecycline and accumulation of resistance determinants reservoirs in genome of Acinetobacter baumannii (A. baumannii) clinical isolates. Susceptibility of the isolates were measured to 18 antimicrobial agents. Genetic diversity of the microbial population was determined using the International Clonal lineage typing (IC typing), multiple locus VNTR analysis (MLVA) and plasmid profiling methods. To detect the AbaRs, Carbapenem-Hydrolyzing Class D ß-Lactamases (CHDLs) genes, AdeABC efflux pump genes and resistance determinants, PCR was used. Filter mating experiments were used to prove that if carbapenem resistance genes are located on conjugative plasmids or not. Among the A. baumannii clinical isolates, 40.8% were carbapenem-tigecycline resistant and in this population, 46.9% were belonging to IC I, IC II or IC III and 53.1% were IC variants. These isolates had fallen in 40 MLVA types and were harboring plasmids in multiple numbers and sizes. In this study, blaOXA-23-like was the most prevalent CHDL and conjugation analysis proved that the carbapenem resistance genes are located on conjugative plasmids. All efflux pump genes, except for adeC, were detected in all carbapenem-tigecycline resistant A. baumannii (CTRAb) isolates. Resistance determinants were distributed in both TnAbaRs and R plasmids with a shift toward the R plasmids. Emerging of carbapenem resistant A. baumannii (CRAB) with simultaneous resistance to the last line therapy including tigecycline represent emerging of extensively drug resistance (XDR) and pandrug resistance (PDR) phenotypes that would be a great threat to our public health system.

Characterization of Oxacillinase and Metallo-ß-Lactamas Genes and Molecular Typing of Clinical Isolates of Acinetobacter baumannii in Ahvaz, South-West of Iran.

BACKGROUND: Carbapenem resistant Acinetobacter baumannii is an important nosocomial pathogen associated with a variety of infections. OBJECTIVES: The current study aimed to characterize the antimicrobial susceptibility, analyze the prevalence of oxacillinase and metallo-ß-lactamase (MBL) genes and molecular typing of clinical isolates of A. baumannii. MATERIALS AND METHODS: A total of 124 non-repetitive isolates of A. baumannii were collected from various clinical specimens in two teaching hospitals in Ahvaz, south-west of Iran. Antimicrobial susceptibility test was carried out by disk diffusion method. The minimum inhibitory concentrations (MICs) of imipenem, meropenem, colistin and tigecycline were determined using E-test. To screen for MBL production, double disk synergy (DDs) test and MBL E-test were performed. The presence of bla OXA-23-like, bla OXA-24-like, bla OXA-51-like, bla OXA-58-like, bla VIM, bla IMP and bla SPM genes was assessed by polymerase chain reaction (PCR). To identify clonal relatedness, all isolates were subjected to repetitive sequence-based PCR (rep-PCR). RESULTS: Based on disk diffusion results, the highest rate of resistance was observed in rifampin (96.8%). Colistin and polymyxin-B were the most effective agents in vitro. According to the MIC results, the rate of resistance to imipenem, meropenem, colistin and tigecycline were 78.2%, 73.4%, 0.8% and 0, respectively. Metallo-ß-lactamase production was positive in 42.3% and 79.4% of the isolates by DDs test and E-test, respectively. All isolates (100%) carried bla OXA-51-like gene. According to the results of multiplex PCR, bla OXA-23-like and bla OXA-24-like genes were detected in 85.6% and 6.2% of carbapenem resistant isolates, respectively. No bla OXA-58- like, bla VIM, bla IMP and bla SPM were detected. By rep-PCR, carbapenem resistant isolates were separated into six genotypes (A to F). Genotype A (30.9%) was the most prevalent (P value < 0.001). Genotypes B and C were found in 28.9% and 26.8% of the isolates, respectively. CONCLUSIONS: The rate of carbapenem resistant A. baumannii isolates were high in this study. Since, bla OXA-58-like or MBL genes were not detected, it seems that resistance to carbapenems is related to bla OXA-23-like and bla OXA-24-like. Moreover, bla OXA-23-like was the most prevalent oxacillinase (OXA) gene. Most of the isolates belonged to one of the four dominant genotypes indicating clonal dissemination in the hospitals under study. In order to control the spread of carbapenem-resistant A. baumannii, infection- control strategies are needed.