Distribution Of Integrons Research Articles

A Comprehensive Study on the Distribution of Integrons and Their Gene Cassettes in Clinical Isolates.

Antibiotic resistance is a significant global health concern, leading to increased morbidity, mortality, and health care costs. Integrons are genetic elements that could acquire and express gene cassettes, including those that confer antibiotic resistance. This comprehensive study focused on the distribution of integrons and their gene cassettes in clinical isolates. This study explored the structure and classification of integrons with particular emphasis on Class I, II, III, and IV integrons. It also discussed the role of integrons in antibiotic resistance. The findings of this study contribute to a better understanding of the mechanisms underlying antibiotic resistance and provide valuable insights for developing strategies to combat this public health crisis.

Distribution characteristics of integrons and correlation analysis of antibiotic resistance in urine isolated Enterobacter cloacae.

This study aims to understand the distribution of integrons among Enterobacter cloacae isolated from clinical urine specimens in our hospital, as well as the molecular characteristics of the variable region resistance gene cassette of integron-positive strains and its relationship with drug resistance. We collected a total of 80 strains of Enterobacter cloacae isolated from urine specimens of hospitalized patients in our hospital between August 2019 and July 2023, and conducted drug sensitivity testing on them. Polymerase Chain Reaction (PCR) technology was employed to screen these strains for Class 1, 2, and 3 integrons. Following this, the promoter and variable regions of integron-positive strains were amplified and sequenced. Additionally, Enterobacterial Repetitive Intergenic Consensus PCR (ERIC-PCR) was utilized for homology analysis of integron-positive strains. Among the 80 clinical strains, Class 1 integrons were detected in 31 (38.8%) strains, and the following resistance gene cassettes were identified: aadA2, aadA1, aadB, aac(6'), and catB8. Three types of variable region promoters were observed: PcS (4 strains), PcW (7 strains), and PcH1 (17 strains), with consistently inactive downstream P2 promoters. Additionally, Class 2 integrons were detected in 5 (6.3%) strains, carrying the variable region resistance gene cassette dfrA1-sat2-aadA1. The promoters for Class 2 integrons were uniformly of the Pc2D-Pc2A-Pc2B-Pc2C type. No Class 3 integrons were detected. The strains containing integrons showed significantly higher resistance rates to ciprofloxacin, compound sulfamethoxazole, levofloxacin, gentamicin, amikacin, and tobramycin compared to those without integrons (P<0.05). 35 strains of Enterobacter cloacae carrying integrons are primarily classified into three genotypes: A, B, and C. These genotypes are mainly distributed in the urology department and Intensive Care Unit (ICU). The distribution of variable region gene boxes and promoter types is relatively concentrated in the same genotype. Our study confirmed that Enterobacter cloacae isolated from urine samples predominantly carries Class 1 integrons with an extended array of antibiotic-resistant genes. For future research, it is recommended to explore additional resistance mechanisms and evaluate the effectiveness of new therapeutic strategies. Clinicians should be vigilant about the possibility of clonal dissemination and implement enhanced infection control measures in hospital settings.

Analysis of the Class 1 Integrons, Carbapenemase Genes and Biofilm Formation Genes Occurrence in Acinetobacter baumannii Clinical Isolates.

Acinetobacter baumannii is a non-fermentative Gram-negative bacterium that can cause nosocomial infections in critically ill patients. Carbapenem-resistant A. baumannii (CRAB) has spread rapidly in clinical settings and has become a key concern. The main objective of this study was to identify the distribution of integrons and biofilm-formation-related virulence genes in CRAB isolates. A total of 269 A. baumannii isolates (219 isolates of CRAB and 50 isolates of carbapenem-sensitive A. baumannii (CSAB)) were collected. Carbapenemase genes (bla KPC, bla VIM, bla IMP, bla NDM, and bla OXA-23-like) and biofilm-formation-related virulence genes (abal, bfms, bap, and cusE) were screened with PCR. Class 1 integron was screened with PCR, and common promoters and gene cassette arrays were determined with restriction pattern analysis combined with primer walking sequencing. Whole-genome sequencing was conducted, and data were analyzed for a bla OXA-23-like-negative isolate. All 219 CRAB isolates were negative for bla KPC, bla VIM, bla IMP, and bla NDM, while bla OXA-23-like was detected in 218 isolates. The detection rates for abal, bfms, bap, and cusE in 219 CRAB were 93.15%, 63.93%, 88.13%, and 77.63%, respectively. Class 1 integron was detected in 75 CRAB (34.25%) and in 3 CSAB. The single gene cassette array aacA4-catB8-aadA1 with relatively strong PcH2 promoter was detected in class 1 integrons. The bla OXA-23-like-negative CRAB isolate was revealed to be a new sequence type (Oxford 3272, Pasteur 2520) carrying bla OXA-72, bla OXA-259, and bla ADC-26. In conclusion, bla OXA-23-like was the main reason for CRAB's resistance to carbapenems. A new (Oxford 3272, Pasteur 2520) CRAB sequence type carrying the bla OXA-72, bla OXA-259, and bla ADC-26 was reported.

Molecular Characterization of Class 1 Integrons and Carbapenem-Resistant Genes in Enterobacter cloacae Complex Isolates.

Enterobacter cloacae complex (ECC) widely exists in the hospital environment and is one of the important conditional pathogens of hospital-acquired infection. To investigate the distribution of integrons and carbapenem-resistant genes in clinical ECC, 70 isolates of ECC from non-sputum specimens were collected. Class 1 and class 2 integron integrase gene intI1 and intI2, as well as common carbapenem-resistant genes, blaKPC, blaVIM, blaIMP, blaNDM, blaGES, and blaOXA-23, were screened. Gene cassette arrays and common promoters of class 1 integron together with subtypes of carbapenem-resistant genes were determined by sequencing. Resistant rates to commonly used antimicrobial agents between class 1 integron-positive and integron-negative ECC isolates were analyzed. The whole-genome of blaNDM-7 harboring Enterobacter hormaechei was sequenced and the sequence around blaNDM-7 was analyzed. Twenty isolates were positive for intI1. Nineteen different antimicrobial-resistant gene cassettes and 11 different gene cassette arrays, including aadA22-lnuF, were detected in this study. Common promoters of class 1 integron PcH1, PcW, PcW-P2, and PcH2 were detected in 12, 4, 3, and 1 isolates, respectively. The rates of antimicrobial resistance of intI1-positive isolates were higher than those of intI1-negative isolates to clinical commonly used antimicrobial agents. Carbapenem-resistant genes blaKPC-2, blaNDM-1, blaNDM-2, and blaNDM-7 were detected in 2, 1, 1, and 1 isolates, respectively. blaNDM-7 was located between bleMBL and IS5. To the best of our knowledge, this study reported for the first time of blaNDM-7 in ECC isolate in China.

Integron distribution and relationship to antimicrobial resistance in E. coli isolated from blood culture

PurposeThe aim of this study was to evaluate the distribution of integrons in strains of E. coli isolated from blood culture and the relationship between integrons and antimicrobial resistance. MethodsThe study included 100 E. coli strains sent to the Medical Microbiology Laboratory from different clinics between September 2022 and June 2023. Antibiotic susceptibility was evaluated according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST). The presence of integrons was determined by the inhouse polymerase chain reaction (PCR). ResultsIntegron positivity was detected in 45 (45%) of isolates, and class 1 integrons were found in 41 (41%), class 2 integrons in 2 (2%), and both class 1 integrons and class 2 integrons in 2 (2%). Class 3 integron positivity was not detected. In total, 63 cases of community origin and 37 cases of hospital origin were identified. When antibiotic resistance was evaluated, the highest sensitivity was noted for amikacin (1%), meropenem (5%), imipenem (6%), and the highest resistant antibiotics were ampicillin (82%), cepfuroxime sodium (65%), and amoxicillin/clavulanate (62%), respectively. Of the 16 antimicrobial substances evaluated, 10 had an antibiotic resistance rate of over 45%. In class 1 integron-positive samples, ampicillin resistance and trimethoprim/sulfamethoxazole resistance were higher than in negative samples (p = 0.02, p = 0.0001, respectively). Fifty-one (51%) samples were found to have multiple drug resistance (MDR). In total, 59.5% of hospital-acquired isolates and 46% of community-acquired isolates were considered to be MDR. The class 1 integron positivity in MDR samples was high (p = 0.038). ConclusionThe high MDR rates in both hospital-acquired and community-acquired isolates are alarming. In particular, class 1 integron monitoring is very important to prevent the spread of MDR isolates.

IntegronFinder 2.0: Identification and Analysis of Integrons across Bacteria, with a Focus on Antibiotic Resistance in Klebsiella.

Integrons are flexible gene-exchanging platforms that contain multiple cassettes encoding accessory genes whose order is shuffled by a specific integrase. Integrons embedded within mobile genetic elements often contain multiple antibiotic resistance genes that they spread among nosocomial pathogens and contribute to the current antibiotic resistance crisis. However, most integrons are presumably sedentary and encode a much broader diversity of functions. IntegronFinder is a widely used software to identify novel integrons in bacterial genomes, but has aged and lacks some useful functionalities to handle very large datasets of draft genomes or metagenomes. Here, we present IntegronFinder version 2. We have updated the code, improved its efficiency and usability, adapted the output to incomplete genome data, and added a few novel functions. We describe these changes and illustrate the relevance of the program by analyzing the distribution of integrons across more than 20,000 fully sequenced genomes. We also take full advantage of its novel capabilities to analyze close to 4000 Klebsiella pneumoniae genomes for the presence of integrons and antibiotic resistance genes within them. Our data show that K. pneumoniae has a large diversity of integrons and the largest mobile integron in our database of plasmids. The pangenome of these integrons contains a total of 165 different gene families with most of the largest families being related with resistance to numerous types of antibiotics. IntegronFinder is a free and open-source software available on multiple public platforms.

Antibiotic Resistance Profile of Salmonella enterica Isolated from Exotic and Indigenous Leafy Green Vegetables in Accra, Ghana

Fresh produce-borne enteric bacterial pathogens that are resistant to antibiotics have posed serious challenges to food safety and public health worldwide. This study was conducted to evaluate the antibiotic resistance profiles of Salmonella enterica isolates (n = 33) recovered from exotic and indigenous leafy green vegetable samples (n = 328) collected from 50 vegetable farms in 12 farming areas and 37 vegetable sellers in four market centers in Accra, Ghana, from March 2016 to March 2017 and to determine the distribution of integrons among antibiotic-resistant isolates. The susceptibility of the Salmonella isolates to 12 antibiotics was assayed with the standard disk diffusion assay. The MICs of the five most resisted antibiotics were determined with a twofold macrodilution method. A PCR assay was used to detect the presence of integrons in Salmonella isolates, and PCR products with the amplified integron gene cassette were purified and sequenced with the Sanger sequencing technology. The Salmonella isolates used in the study were resistant to at least one tested antibiotic, and 30.3% (10 of 33) of the isolates were multidrug resistant. Most isolates (81.8%) were resistant to sulfisoxazole. The MICs of tetracycline, cefoxitin, streptomycin, ampicillin, and sulfisoxazole were 16, 32, 64, 64, and >1,024 μg/mL, respectively. Five patterns of multidrug resistance were observed among the Salmonella isolates, and the most common patterns were AAuFox (30.3%) and AAuFoxSSu (18.1%). One (3.0%) of the 33 Salmonella isolates tested positive for the class 1 integron, with a gene cassette of about 800 bp. Nucleotide sequencing revealed that this class 1 integron carried a single gene, dfrA7. Further studies are needed to determine whether the consumption of contaminated leafy green vegetables is a route for acquiring antibiotic-resistant Salmonella in Accra, Ghana.

Integron and its role in antimicrobial resistance: A literature review on some bacterial pathogens.

In recent years, different acquired resistance mechanisms, including transposons, bacteriophages, plasmids, and integrons have been identified as involved in the spread of resistance genes in bacteria. The role of integrons as mobile genetic elements playing a central role in antibiotic resistance has been well studied and documented. Integrons are the ancient structures that mediate the evolution of bacteria by acquiring, storing, disposing, and resorting to the reading frameworks in gene cassettes. The term integron describes a large family of genetic elements, all of which are able to capture gene cassettes. Integrons were classified into three important classes based on integrase intI gene sequence. Integrons can carry and spread the antibiotic resistance genes among bacteria and are among the most significant routes of distribution of resistance genes via horizontal transfer. All integrons have three essential core features. The first feature is intI, the second one is an integron-associated recombination site, attI, and an integron-associated promoter, Pc, is the last feature. Among them, the class 1 integron is a major player in the dissemination of antibiotic resistance genes across pathogens and commensals. Various classes of integrons possessing a wide variety of gene cassettes are distributed in bacteria throughout the world. This review thus focuses on the distribution of integrons among important bacteria.

Distribution of integrons and phylogenetic groups among Escherichia coli causing community-acquired urinary tract infection in Upper Egypt.

Escherichia coli is a major cause of community-acquired urinary tract infections (CA-UTIs). In this study, we investigated the antimicrobial resistance patterns, the distribution of phylogenetic groups, and the prevalence and characteristics of integron-bearing E. coli isolates from outpatients with CA-UTIs in El-Minia governorate, in Upper Egypt. Out of the 583 urine samples collected, 134 were positive for E.coli, from which the most resistant isolates (n= 80) were selected for further analysis. The majority of these isolates (62.5%, 50/80) showed multidrug resistance profiles. Group B2 was the most predominant phylogenetic group (52.5%), followed by group F (21.25%), Clades I or II (12.5%), and finally isolates of unknown phylogroup (13.75%). Of the 80 isolates, 7 (8.75%) carried class1 integrons, which contained 3 different types of integrated gene cassettes, including those conferring resistance to streptomycin/spectinomycin, trimethoprim, and some open reading frames of unknown function (gcuF). In conclusion, the types and combinations of the gene cassettes in our study may reflect the specific selective pressures to which the isolates were subjected within the study region, therefore, providing valuable data for future intervention strategies that are precisely tailored to prevent the dissemination of the uropathogenic E.coli strains circulating within Upper Egypt.

Distribution of integrons and phylogenetic groups among highly virulent serotypes of Klebsiella pneumoniae in a Chinese tertiary hospital

ObjectivesThis study describes the distribution of integrons and phylogenetic groups among clinical highly virulent serotype (HVS) Klebsiella pneumoniae isolates in a Chinese tertiary hospital. MethodsClass 1, 2 and 3 integrases were identified by PCR in 90 clinical isolates of HVS K. pneumoniae. Antimicrobial susceptibility was determined by the disk diffusion method. Multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were used to analyse the genotypes of the HVS K. pneumoniae isolates. ResultsSerotypes K1, K2, K20, K54 and K57 accounted for 54.5%, 21.1%, 1.1%, 18.9% and 4.4% of the 90 isolates. Among the 50 integron-positive isolates, 48 (96%) and 2 (4%) were classified as having class 1 (intI1) and class 2 (intI2) integrons, respectively. Gene cassettes encoding resistance to trimethoprim (dfr) and aminoglycosides (aac, aad) were found to be predominant in class 1 integrons. In addition, the most prevalent sequence type (ST) among the HVS K. pneumoniae isolates was ST23 (49/90; 54.4%), followed by ST29 (11/90; 12.2%), ST86 (10/90; 11.1%), ST65 (9/90; 10.0%), ST15 (6/90; 6.7%), ST412 (4/90; 4.4%) and ST34 (1/90; 1.1%). ConclusionIn summary, a high prevalence of integrons (55.6%) was found among HVS K. pneumoniae isolates in a Chinese tertiary hospital. Class 1 integrons were the most predominant and their variable regions were polymorphic. The presence of integrons in HVS K. pneumoniae isolates results in increased antimicrobial resistance.

Distribution of integrons and antimicrobial resistance in carbapenem-resistant Acinetobacter baumannii clinical strains

Objective To investigate the distribution of integrons in clinical isolates of carbapenem-resistant Acinetobacter baumannii and their relationships to bacterial resistance to antimicrobial agents. Methods A total of 115 carbapenem-resistant Acinetobacter baumannii strains were isolated from clinical samples of patients from January to October, 2017. Phoenix 100 automatic microbiological analyzer was used for antimicrobial sensitivity analysis. Classes 1 and 2 integrase genes and carbapenemase-encoding genes, blaIMP, blaVIM, blaKPC, blaNDM and blaOXA-23, were screened by PCR. The variable regions of integrons were amplified by long fragment PCR. The types of promoters and gene cassette arrays of variable regions were determined by sequencing and overlap PCR. Relationships between integrons and antimicrobial resistance were analyzed. Results The 115 isolates of carbapenem-resistant Acinetobacter baumannii were resistant to most commonly used antimicrobial agents, but sensitive to polymyxin E. All of the isolates carried blaOXA-23 gene and none of them were positive for blaIMP, blaVIM, blaKPC or blaNDM gene. Class 1 integrase gene intI1 was detected in 40 isolates (34.8%), while class 2 integrase gene intI2 was not detected. Two gene cassette arrays of variable regions, aacA4-catB8-aadA1 (39 isolates) and aacC1-gacP-gacQ-aadA1a (23 isolates), were detected in intI1-positive isolates. Twenty-two isolates carried both aacA4-catB8-aadA1 and aacC1-gacP-gacQ-aadA1a. The upstream promoters of the variable regions were relatively strong promoters, PcH2 and PcS. The gene cassettes of the variable regions endowed bacteria with resistance to chloramphenicol and aminoglycoside antibiotics. The resistance rate of class 1 integron-positive isolates to compound sulfamethoxazole was higher than that of negative strains. However, their resistance rate to ampicillin/sulbactam was lower than that of negative strains. Conclusions Antimicrobial resistance in carbapenem-resistant Acinetobacter baumannii was serious. Carbapenem resistance was associated with blaOXA-23 gene. The types of promoters of variable regions in class 1 integrons were all relatively strong promoters. Class 1 integrons were closely related to sulfonamides resistance. Key words: Acinetobacter baumannii; Carbapenem; Antimicrobial resistance; Integron; Promoter

Enterococcal isolates from bovine subclinical and clinical mastitis: Antimicrobial resistance and integron-gene cassette distribution

Bovine mastitis is one of the most prevalent and costly diseases, and can be caused by a variety of bacterial pathogens including enterococci. Unfortunately, comprehensive studies about the prevalence and antimicrobial resistance profiles of entercocci are scarcely reported. This study aimed to investigate the occurrence of enterococci associated with bovine clinical mastitis and subclinical mastitis, to assess their antimicrobial resistance profiles, and to detect the distribution of integrons and gene cassette arrays in Liaoning of China. Our results indicated subclinical mastitis occurred in 34.3% of bovine, and 21.4% of bovine were positive for clinical mastitis, meanwhile Enterococcus faecium is the predominant pathogen in both clinical mastitis and subclinical mastitis. More than 50% of the total isolates were resistant to penicillin, ceftiofur, tylosin, lincomycin, and oxytetracycline. Class I integrons was detected in enterococcal isolates from both clinical and subclinical mastitis with 57.1% and 45.3%, respectively. Meanwhile, class II integrons only were observed in enterococcal isolates from subclinical mastitis. Multidrug resistance has become prevalent in enterococci isolated from clinical mastitis and subclinical mastitis in Liaoning, northeast of China. This study revealed that enterococcal isolates had shown resistant to β-lactam antibiotics including penicillin, and different therapeutic programs should be carried out in Liaoning of China.

Conserved phylogenetic distribution and limited antibiotic resistance of class 1 integrons revealed by assessing the bacterial genome and plasmid collection

BackgroundIntegrons, especially the class 1 integrons, are major contributors to the acquisition and dissemination of antibiotic resistance genes (ARGs). However, comprehensive knowledge of the types, content, and distribution of integrons in bacterial taxa is lacking to evaluate their contribution.ResultsWe have constructed a new integrase database and developed a pipeline that provides comprehensive recovery of class 1 integrons. Previous PCR-based techniques might only detect one fourth of the integron-integrases and integrons recovered in this study. By exploring the class 1 integrons in over 73,000 currently available complete and draft bacterial genomes, the contribution of class 1 integrons in spreading and acquiring ARGs was evaluated. Firstly, the host species of class 1 integrons are highly conserved within (96%) in class Gammaproteobacteria, dominated by four pathogenic species of “ESKAPE.” Secondly, more than half of class 1 integrons are embedded in chromosomes with less potential for horizontal gene transfer. Finally, ARGs that have been acquired by these integrons only cover 11% of all the ARG genotypes detected in bacterial genomes.ConclusionsThe above observations indicated that there are both biological and ecological limitations to class 1 integrons in acquiring and spreading ARGs across different classes of the domain Bacteria.

Impact of Wastewater Treatment on the Prevalence of Integrons and the Genetic Diversity of Integron Gene Cassettes.

The integron platform allows the acquisition, expression, and dissemination of antibiotic resistance genes within gene cassettes. Wastewater treatment plants (WWTPs) contain abundant resistance genes; however, knowledge about the impacts of wastewater treatment on integrons and their gene cassettes is limited. In this study, by using clone library analysis and high-throughput sequencing, we investigated the abundance of class 1, 2, and 3 integrons and their corresponding gene cassettes in three urban WWTPs. Our results showed that class 1 integrons were most abundant in WWTPs and that wastewater treatment significantly reduced the abundance of all integrons. The WWTP influents harbored the highest diversity of class 1 integron gene cassettes, whereas class 3 integron gene cassettes exhibited highest diversity in activated sludge. Most of the gene cassette arrays detected in class 1 integrons were novel. Aminoglycoside, beta-lactam, and trimethoprim resistance genes were highly prevalent in class 1 integron gene cassettes, while class 3 integrons mainly carried beta-lactam resistance gene cassettes. A core class 1 integron resistance gene cassette pool persisted during wastewater treatment, implying that these resistance genes could have high potential to spread into environments through WWTPs. These data provide new insights into the impact of wastewater treatment on integron pools and highlight the need for surveillance of resistance genes within both class 1 and 3 integrons.IMPORTANCE Wastewater treatment plants represent a significant sink and transport medium for antibiotic resistance bacteria and genes spreading into environments. Integrons are important genetic elements involved in the evolution of antibiotic resistance. To better understand the impact of wastewater treatment on integrons and their gene cassette contexts, we conducted clone library construction and high-throughput sequencing to analyze gene cassette contexts for class 1 and class 3 integrons during the wastewater treatment process. This study comprehensively profiled the distribution of integrons and their gene cassettes (especially class 3 integrons) in influents, activated sludge, and effluents of conventional municipal wastewater treatment plants. We further demonstrated that while wastewater treatment significantly reduced the abundance of integrons and the diversity of associated gene cassettes, a large fraction of integrons persisted in wastewater effluents and were consequentially discharged into downstream natural environments.

Incidence and risk of co-transmission of plasmid-mediated quinolone resistance and extended-spectrum β-lactamase genes in fluoroquinolone-resistant uropathogenic Escherichia coli: a first study from Kolkata, India.

Co-resistance to fluoroquinolones and β-lactams results in treatment complications for uropathogenic Escherichia coli (UPEC) infections. This study aimed to detect the coexistence and co-transmission of plasmid-mediated quinolone resistance (PMQR) and extended-spectrum β-lactamase (ESBL) genes in UPEC from Kolkata, India. Escherichia coli was detected biochemically from culture-positive urine samples. Antimicrobial resistance and ESBL production were confirmed by disk diffusion assay. Transfer of PMQR and ESBL genes was performed using azide-resistant E. coli J53 as recipient. PCR was conducted to identify PMQR and ESBL genes, plasmid incompatibility types, insertion sequences, integrons and ERIC-PCR patterns. PMQR determinants were detected in 50.0% (35/70) of ciprofloxacin-resistant isolates, with ESBL production in 42.9% (15/35) and a β-lactamase inhibitor-resistant phenotype in 51.4% (18/35). The highest co-occurrence (37.1%; 13/35) and co-transmission of aac(6')-Ib-cr with blaTEM, blaCTX-M and blaOXA was observed. Among the conjugal plasmids, replicon types FrepB/FrepB+F1B were predominant, with rare incidences of A/C, N, X, I1, FIIS, L/M and H1. Distribution of integrons and ISEcp1 and IS26, either alone or in combination, irrespective of PMQR and ESBL gene types was observed. Discrete ERIC-PCR profiles indicated that acquisition of PMQR and ESBLs and their dissemination may be attributed to horizontal gene transfer. This study demonstrates for the first time the risk of co-transmission of fluoroquinolone and β-lactam resistance amongst UPEC from Kolkata, posing a major public-health threat and limiting treatment options. Monitoring at the molecular level is necessary to design appropriate prescription policies to combat the alarming rise in drug resistance amongst these uropathogens.

Molecular characterisations of integrons in clinical isolates of Klebsiella pneumoniae in a Chinese tertiary hospital

Integrons are mobile genetic elements that play an important role in the distribution of antibiotic-resistance genes among bacteria. This study aimed to investigate the distribution of integrons in clinical isolates of Klebsiella pneumoniae and explore the molecular mechanism of integron-mediated multiple-drug resistance in K.pneumoniae. Class 1, 2, and 3 integrases were identified by polymerase chain reaction (PCR) among 178 K.pneumoniae clinical isolates. Antibiotic susceptibility was examined by disk-diffusion method. Conjugation experiments were conducted to evaluate the horizontal-transfer capability, and multilocus sequence typing (MLST) assays were conducted to explore the genetic relationships among the isolates. Highly virulent serotypes were identified by PCR from the 44 integron-positive isolates with variable regions. Class1 and 2 integrons were detected in 60.1% and 1.7% of isolates, respectively. One isolate carried both class 1 and 2 integrons. Class 3 integrons were not detected in all 178 isolates. Among the 44 integrons containing variable regions, 39 were located in conjugative plasmids. Dihydrofolate reductase (dfrA) and aminoglycoside adenyltransferase (aad) were found to be the most common in class 1 and 2 integrons. These gene cassettes encoded resistance to trimethoprim and aminoglycosides. Moreover, the association between integron carriage and antibiotic resistance was most significant for aminoglycosides, phenicols, and fluoroquinolones. Among the 44 integron-positive isolates with variable regions, 9 were classified as highly virulent serotypes (k1, k2, k20, and k54). In addition, MLST analysis detected 13 sequence types (STs), with the predominant ones being ST11 and ST15. The eBURST analysis revalued the existence of 11 singleton STs and one group, which is comprised of ST11 and ST437. The wide diversity of detected integrons suggested that the horizontal transfer by mobile genetic elements played a major role in the distribution of antimicrobial resistance genes, thereby indicating the urgent need to use effective means of avoiding the spread of drug-resistant bacteria.

The trend of enteropathogenic Escherichia coli towards atypical multidrug resistant genotypes

The aim of this study was to investigate the prevalence of multidrug resistance (MDR) in atypical enteropathogenic Escherichia coli (EPEC) genotypes among 547 diarrheal children. All E. coli isolates with eae+stx1−stx2− genotypes included in this study and atypical property of EPEC was characterized by the absence of Bundle-forming pili (bfpA gene). Bacterial pathogens were detected in 70 patients (12.8%) among which atypical EPEC (5.3%) were the most common. The higher resistance rate was seen to tetracycline (70%), cotrimoxazole (60%) and nalidixic acid (53.3%) related to MDR phenotype in 63.3% of isolates. The presence of class 1 and 2 integrons was 30% and 6.6% with the dominance of dfrA, aadA gene cassettes among the isolates. Eleven out of 21 phenotypically tetracycline-resistant isolates (52.38%) harboured one or two tetracycline resistance genes (A–D) which shows the incapability of known data to reasonable tetracycline resistance phenotypes among EPEC isolates. A high level of genotypic diversity was seen among the isolates by Pulsed-field gel electrophoresis method which ranged from 89.7 to 29% and no clear correlation was obtained between tetracycline resistance or integron carriage and specific pulsotypes. In conclusion, the data presented here add to knowledge about the heterogeneous nature of MDR EPEC population in Iran which has a growing tendency towards atypical genotypes. The distribution of integrons among EPEC isolates in Iran is decreasing; although, the resistance gene content is almost stable through years.

Investigating the distribution of integrons among clinical isolates of acinetobacter baumannii and their association to carbapenem resistance

Background: Background: To determine the dissemination of classes of integrons and their roles in carbapenem resistant strains of Acinetobacter baumannii. Integron1, 2 and 3 have been reported in various microrognisms and are implicated in conferment of multi drug resistance. Carriage of carbapenem resistance genes on these integrons has not been consistent. Multidrug drug resistance is being increasingly reported in A.baumannii. Though integron 1 and 2 have been detected, there is no report from India correlating carbapenem resistance to the presence of integrons in A.baumannii. Methods & Materials: Materials and methods: One hundred fifteen (n=115) clinical isolates of A.baumannii were collected from different clinical specimens of clinical microbiology laboratories two different tertiary care hospitals. Cultures were identified by routine microbiology methods and also by VITEK-2 system. Antimicrobial susceptibility testing and minimum inhibitory concentration for panel of 20 antibiotics were examined. To investigate classes of integrons, multiplex PCR for integrase intI1 and intI2 was performed along with A.baumannii species specific marker (Ab-ITS). ClassA, B and D carbapenemases were identified in these isolates and the distribution of carbapenemases with specific reference to type of integron has been determined by PCR. Results: Results: A total of 115 isolates were included in this study. Genotypic and phenotypic results showed 93(80%) as carbapenem resistant and 22(20%) as carbapenem sensitive isolates. Out of the 93 carbapenem resistant isolates, 76 (81%) isolates possessed integrons. 58(62%) isolates carried class 1 integron and 18(19%) isolates carried class 2 integron. Surprisingly, 11 carbapenem resistant isolates and two carbapenem sensitive isolates harboured both classes of integrons. One carbapenem sensitive isolate had only class 2 integron. Conclusion: Conclusion: Multiplex PCR for the detection and identification of integron classes along with species specific marker (Ab-ITS) will be a useful method for the epidemiological studies. This rapid, reliable determination of the genetic relatedness of clinical isolates in this antibiotic era is essential when investigating cases of nosocomial outbreak.

Characterization of integrons and novel cassette arrays in bacteria from clinical isloates in China, 2000-2014.

Rapid dissemination of antibiotic resistance genes among bacterial isolates is an increasing problem in China. Integron, a conserved DNA sequence, which is carried on episomal genetic structures, plays a very important role in development of antibiotic resistance. This systematic analysis was based on MEDLINE and EMBASE databases. We summarized the distribution and proportion of different types of gene cassette arrays of integrons (including class 1, 2, 3 and atypical class 1 integron) from clinical bacteria isolates in China. Fifty-six literatures were included in this study. Most of the strains were Gram-negative bacteria (94.1%, 7,364/7,822) while only 5.9% strains were Gram-positive bacteria. Class 1 integrons were detected in 54.2% (3956/7295) Gram-negative strains. aadA2 was the most popular gene cassette array detected from 60 Gram-positive bacteria while dfrA17-aadA5 were detected in 426 Gram-negative bacteria. This study identified 12 novel gene cassette arrays which have not been previously found in any species. All the novel gene cassette arrays were detected from Gram-negative bacteria. A regional characteristic of distribution of integrons was presented in this study. The results highlight a need for continuous surveillance of integrons and provide a guide for future research on integron-mediated bacteria resistance.

Preferential carriage of class 2 integrons in Acinetobacter baumannii CC113 and novel singletons.

Our understanding of the distribution of integrons associated with multidrug resistance in Acinetobacter baumannii isolates around the world remains incomplete. The association between the class 1 and 2 integron A. baumannii-positive isolates (n = 60), recovered since 1982 from 11 Argentinean hospitals, and the circulating lineages, was investigated. While class 2 integrons were highly significantly associated with clonal lineage CC113B/CC79P (P = 0·009) and novel singletons (P = 0·001), class 1 integrons were found not to be associated with CC109B/CC1P or other lineages. The study reveals a differential distribution of class 2 integrons in lineages, and suggests that the prevalence of intI2 in Argentina is related to the emergence of novel singletons in recent years and to the abundance of CC113B/CC79P, which has been the local dominant lineage for several decades.