Multiplex PCR for screening of integrons in bacterial lysates

Antimicrobial susceptibility profile and molecular characterization of Vibrio parahaemolyticus strains isolated from imported shrimps

Vibrio parahaemolyticus is a threat to human health and one of the leading bacterial causes of seafood-borne infection worldwide. This pathogen is autochtonous in the marine environment and is able to acquire antimicrobial resistance (AMR) mechanisms, which is a global concern. However, the emergence of AMR V. parahaemolyticus strains in seafood is still understudied, as interpretation criteria for this species for antimicrobial susceptibility tests are limited in the literature. In this study, we investigated the susceptibility profiles to clinically important antibiotics and the associated genetic determinants of V. parahaemolyticus isolates cultured from imported shrimps. Based on the analysis of the resistance phenotypes of 304 V. parahaemolyticus isolates, we have defined experimental epidemiological cutoff values (COWT) for 14/15 antibiotics tested. We observed that 19.1% of the bacterial isolates had acquired resistance to at least one antibiotic class. The highest number of resistance was associated with tetracycline (14.5% of the strains) and trimethoprim-sulfamethoxazole (3.6%). Moreover, seven strains were multidrug-resistant (MDR, resistant to at least three antibiotic classes). The most frequently identified genes in these strains were aph(3″)-Ib/aph(6)-Id (aminoglycoside resistance), sul2 (sulfonamide), tet(59) (tetracycline), and floR (chloramphenicol). The SXT/R391 family ICE and class 1 integron-integrase genes were detected by PCR in three and one MDR V. parahaemolyticus strains, respectively. Consequently, V. parahaemolyticus in seafood can act as a reservoir of AMR, constituting a health risk for the consumer.IMPORTANCEOur study on "Antimicrobial Resistance Profiles and Genetic Determinants of Vibrio parahaemolyticus Isolates from Imported Shrimps" addresses a critical gap in understanding the emergence of antimicrobial resistance (AMR) in this seafood-associated pathogen. Vibrio parahaemolyticus is a major cause of global seafood-borne infections, and our research reveals that 19.1% of isolates from imported shrimps display resistance to at least one antibiotic class, with multidrug resistance observed in seven strains. Importantly, we establish experimental epidemiological cutoff values for antibiotic susceptibility, providing valuable criteria specific to V. parahaemolyticus. Our findings underscore the potential risk to consumers, emphasizing the need for vigilant monitoring and intervention strategies. This study significantly contributes to the comprehension of AMR dynamics in V. parahaemolyticus, offering crucial insights for global public health. The dissemination of our research through Microbiology Spectrum ensures broad accessibility and impact within the scientific community and beyond.

Dynamics of integron structures across a wastewater network - Implications to resistance gene transfer

Class 1 and other integrons are common in wastewater networks, often being associated with antibiotic resistance genes (ARGs). However, the importance of different integron structures in ARG transfer within wastewater systems has only been implied, especially between community and hospital sources, among wastewater treatment plant compartments, and in receiving waters. This uncertainty is partly because current clinical class 1 integron qPCR assays (i.e., that target human-impacted structures, i.e., clintI1) poorly delineate clintI1 from non-impacted class 1 integron structures. They also say nothing about their ARG content. To fill these technical gaps, new real-time qPCR assays were developed for "impacted" class 1 structures (called aint1; i.e., anthropogenic class 1 integrons) and empty aint1 structures (i.e., carry no ARGs; called eaint1). The new assays and other integron assays then were used to examine integron dynamics across a wastewater network. 16S metagenomic sequencing also was performed to characterise associated microbiomes. aint1 abundances per bacterial cell were about 10 times greater in hospital wastewaters compared with other compartments, suggesting aint1 enrichment with ARGs in hospital sources. Conversely, the relative abundance of eaint1 structures were over double in recycled activated sludge compared with other compartments, except receiving waters (RAS; ∼30% of RAS class 1 structures did not carry ARGs). Microbiome analysis showed that human-associated bacterial taxa with mobile integrons also differed in RAS and river sediments. Further, class 1 integrons in RAS bacteria appear to have released ARGs, whereas hospital bacteria have accumulated ARGs. Results show that quantifying integron dynamics can help explain where ARG transfer occurs in wastewater networks, and should be considered in future studies on antibiotic resistance in the environment.

Molecular Characterization of Multiple Antibiotic-Resistant Acinetobacter baumannii Isolated from Egyptian Patients

Acinetobacter baumannii is an opportunistic microorganism commonly found in intensive care units (ICUs), and it is responsible for a broad span of hospital-acquired infections. Persistence of nosocomial infection caused by multidrug-resistant (MDR) A. baumannii is an alarming health care issue in Egypt, and at present, colistin remains the treatment of choice for the management of MDR A. baumannii infections. A. baumannii possesses great capacity to develop and acquire resistance to a broad range of antibiotics. The acquisition and dissemination of antibiotic-resistant determinants in A. baumannii strains are mediated by integrons, especially class I integrons. This study focuses on the characterization of some genetic mechanisms underlying the multidrug-resistant phenotypes of A. baumannii isolates in Egypt. Forty-eight A. baumannii specimens were isolated from different hospitalized patients; least resistance was observed against amikacin and tigecycline, with 60% and 58.5% of the isolates resistant, respectively, whereas 62.5% of the isolates were resistant to imipenem and meropenem. The highest sensitivity was found for colistin. Genetic analysis revealed that blaoxa-51 was detected in all isolates, the blaoxa-23-like gene was detected in 80% of the isolates, and blaoxa-24 and blaoxs-58 were not detected in any isolate. Finally, PCR analysis revealed that 6.6% of isolates carried the class I integron gene.

Integrons and Antiseptic Resistance Genes Mediate Resistance of Acinetobacter baumannii and Pseudomonas aeruginosa Isolates from Intensive Care Unit Patients with Wound Infections

BACKGROUND

Acinetobacter baumannii and Pseudomonas aeruginosa are of major concern for hospitalized patients.

METHODS

We evaluated antibiotic and antiseptic resistance of A. baumannii (n = 29) and P. aeruginosa (n = 37) isolates recovered from 66 intensive care unit (ICU) patients and determined the prevalence of qacE, qacEΔ1, and integrons in these clinical isolates. Antibiotic and antiseptic susceptibility testing was performed via Kirby Bauer disk diffusion and broth microdilution methods, respectively. The resistance genes and integrons were detected by PCR. A. baumannii and P. aeruginosa ICU isolates showed 100% and 70.3% antibiotic multiple drug resistance patterns, respectively.

RESULTS

The isolates also revealed high levels of resistance (MIC ≥ 16 µg/ml) against antiseptics commonly used in Egyptian hospitals (Benzalkonium, Benzethonium, and Chlorhexidine). The qacEΔ1 gene showed higher levels of prevalence in both A. baumannii and P. aeruginosa isolates (93.5% and 78%, respectively) as compared to that of qacE gene (52.0% and 33.0%, respectively). The intI1 was more prevalent among A. baumannii isolates (65.5%) compared to P. aeruginosa isolates (37.8%). P. aeruginosa resistance genotypes were significantly associated with antibiotic and antiseptic resistance patterns. A. baumannii resistance genotypes were associated with antiseptic-resistance patterns.

CONCLUSION

The excessive usage of antiseptics may escalate bacterial resistance, especially with high prevalence of intI1 integron in these pathogens.

Genotyping and molecular characterization of clinical Acinetobacter baumannii isolates from a single hospital in Southwestern Iran

ACINETOBACTER BAUMANNII

(A. baumannii) is a pathogen responsible for nosocomial infections among the hospitalized patients. The aim of this study was to investigate genotyping and molecular characterization and to examine the biofilm formation ability of A. baumannii isolates. In total, 70 A. baumannii isolates were collected from patients admitted to Imam Khomeini Hospital in Ahvaz, Southwestern Iran. Minimum inhibitory concentrations (MIC) test was performed using Vitek 2 system. The presence of genes encoding metallo-β-lactamases, oxacillinases, and integrase and the biofilm formation ability were then evaluated. Multiple locus variable-number tandem repeat (VNTR) analysis (MLVA) typing and multiplex PCR were performed to determine the genetic relationships. The blaOXA-23-like gene had the highest prevalence. The frequency of genes encoding blaSPM, blaIMP, and blaVIM among MDR A. baumannii isolates were 12 (17.1%), 18 (25.7%), and 22 (31.4%), respectively. Moreover, 46 isolates (75.4%) harbored class I integron and 10 isolates (16.39%) carried class II integron. The number of weak, moderate and strong biofilm-producing isolates were 3 (4.3%), 7 (10%), and 55 (78.5%), respectively. The results showed that 70 A. baumannii isolates were grouped into 12 distinct MLVA types with five clusters and four singleton genotypes. In addition, 25 (35.7%) isolates were assigned to international clone (IC) variants, 37 (52.8%) isolates belonged to group 1 (IC II), and 8  (11.4%) isolates belonged to group 2 (IC I). Our findings revealed that the population structure of the A. baumannii isolates was genetically diverse. More focus on genetic variation and antibiotic resistance of A. baumannii isolates are recommended.

Occurrence of integrons and antibiotic resistance genes in cryoconite and ice of Svalbard, Greenland, and the Caucasus glaciers

The prevalence of integrons and antibiotic resistance genes (ARGs) is a serious threat for public health in the new millennium. Although commonly detected in sites affected by strong anthropogenic pressure, in remote areas their occurrence, dissemination, and transfer to other ecosystems is poorly recognized. Remote sites are considered as a benchmark for human-induced contamination on Earth. For years glaciers were considered pristine, now they are regarded as reservoirs of contaminants, thus studies on contamination of glaciers, which may be released to other ecosystems, are highly needed. Therefore, in this study we evaluated the occurrence and frequency of clinically relevant ARGs and resistance integrons in the genomes of culturable bacteria and class 1 integron-integrase gene copy number in the metagenome of cryoconite, ice and supraglacial gravel collected on two Arctic (South-West Greenland and Svalbard) and two High Mountain (the Caucasus) glaciers. Altogether, 36 strains with intI1 integron-integrase gene were isolated. Presence of class 1 integron-integrase gene was also recorded in metagenomic DNA from all sampling localities. The mean values of relative abundance of intI1 gene varied among samples and ranged from 0.7% in cryoconite from Adishi Glacier (the Caucasus) to 16.3% in cryoconite from Greenland. Moreover, antibiotic-resistant strains were isolated from all regions. Genes conferring resistance to β-lactams (bla_SHV, bla_TEM, bla_OXA, bla_CMY), fluoroquinolones (qepA, qnrC), and chloramphenicol (cat, cmr) were detected in the genomes of bacterial isolates.

Metagenomic analysis of β-lactamase and carbapenemase genes in the wastewater resistome

The emergence and spread of resistance to antibiotics among bacteria is the most serious global threat to public health in recent and coming decades. In this study, we characterized qualitatively and quantitatively β-lactamase and carbapenemase genes in the wastewater resistome of Central Wastewater Treatment Plant in Koziegłowy, Poland. The research concerns determination of the frequency of genes conferring resistance to β-lactam and carbapenem antibiotics in the genomes of culturable bacteria, as well as in the wastewater metagenome at three stages of treatment: raw sewage, aeration tank, and final effluent. In the final effluent we found bacteria with genes that pose the greatest threat to public health, including genes of extended spectrum β-lactamases - bla_CTX-M, carbapenemases - bla_NDM, bla_VIM, bla_GES, bla_OXA-48, and showed that during the wastewater treatment their frequency increased. Moreover, the wastewater treatment process leads to significant increase in the relative abundance of bla_TEM and bla_GES genes and tend to increase the relative abundance of bla_CTX-M, bla_SHV and bla_OXA-48 genes in the effluent metagenome. The biodiversity of bacterial populations increased during the wastewater treatment and there was a correlation between the change in the composition of bacterial populations and the variation of relative abundance of β-lactamase and carbapenemase genes. PCR-based quantitative metagenomic analysis combined with analyses based on culture methods provided significant information on the routes of ARBs and ARGs spread through WWTP. The limited effectiveness of wastewater treatment processes in the elimination of antibiotic-resistant bacteria and resistance genes impose the need to develop an effective strategy and implement additional methods of wastewater disinfection, in order to limit the increase and the spread of antibiotic resistance in the environment.

Abundance of mobile genetic elements in an Acinetobacter lwoffii strain isolated from Transylvanian honey sample

Based on phylogenetic analyses, strain M2a isolated from honey, an unexpected source of acinetobacters, was classified as Acinetobacter lwoffii. The genome of this strain is strikingly crowded with mobile genetic elements. It harbours more than 250 IS elements of 15 IS-families, several unit and compound transposons and 15 different plasmids. These IS elements, including 30 newly identified ones, could be classified into at least 53 IS species. Regarding the plasmids, 13 of the 15 belong to the Rep-3 superfamily and only one plasmid, belonging to the “Low-GC” family, possesses a seemingly complete conjugative system. The other plasmids, with one exception, have a mobilization region of common pattern, consisting of the divergent mobA/mobL-family and mobS-, mobC- or traD-like genes separated by an oriT-like sequence. Although two plasmids of M2a are almost identical to those of A. lwoffi strains isolated from gold mine or Pleistocene sediments, most of them have no close relatives. The presence of numerous plasmid-borne and chromosomal metal resistance determinants suggests that M2a previously has also evolved in a metal-polluted environment. The numerous, possibly transferable, plasmids and the outstanding number of transposable elements may reflect the high potential of M2a for rapid evolution.

Co-Occurrence of Plasmid-Mediated Colistin Resistance (mcr-1) and Extended-Spectrum β-Lactamase Encoding Genes in Escherichia coli from Bovine Mastitic Milk in China

Both mcr-1 phosphoethanolamine transferase enzymes and extended-spectrum β-lactamases (ESBLs) are the main plasmid-mediated mechanisms of resistance to colistin and third-generation cephalosporins, respectively, and currently considered a major concern to humans and food animals. Prevalence of mcr-1 gene in Escherichia coli from dairy cattle has rarely been reported. Our objective was to determine prevalence and characteristics of mcr-1 carrying E. coli isolated from clinical mastitis cases in large dairy farms (>500 cows) in 16 provinces of China. A total of 249 E. coli was isolated from 2,038 mastitic milk samples. Among these isolates, 2.0% (n = 5) and 19.7% (n = 49) were colistin resistant mcr-1-positive and ESBL-producing isolates, respectively. All mcr-1-positive isolates that produced ESBLs also carried the bla_CTX-M-15 gene and belonged to phylogroup-A. Most mcr-1 and bla_CTX-M-15 genes were located on conjugative plasmids (IncP and IncF, respectively) that were successfully transferred to transconjugants in conjugation experiments. All mcr-1-positive E. coli isolates were multidrug resistant, exhibiting resistance to common antimicrobials. Multilocus sequence typing of these mcr-1-carrying E. coli isolates revealed four sequence types, reflecting substantial diversity. Multilocus sequence analysis detected evolutionary connection of mcr-1 carrying isolates with our recently reported ESBL-producing E. coli isolates, raising concerns regarding fast dissemination between bacteria. To our knowledge, this was the first nation-wide report describing isolates of E. coli from mastitic milk samples collected on large dairy farms in China, carrying mcr-1 and bla_CTX-M-15 genes on conjugative plasmids. We concluded that dairy cattle are a potential source of mcr-1-carrying and ESBL-producing E. coli.

Study of genetic diversity, biofilm formation, and detection of Carbapenemase, MBL, ESBL, and tetracycline resistance genes in multidrug-resistant Acinetobacter baumannii isolated from burn wound infections in Iran

Background

Antimicrobial resistance in multidrug-resistant Acinetobacter baumannii (MDR-AB) isolated from burn wound infections is a major concern in intensive care or burns units worldwide, and molecular studies are considered critical strategies for control of MDR-AB outbreaks in this regard. Thus, in this study, antibiotic resistance, biofilm-forming ability, molecular epidemiology of MDR A. baumannii strains recovered from patients with burns were investigated in three major hospital centers of Iran.

Methods

In this cross-sectional research, 163 non-repetitive A. baumannii strains were tested for susceptibility to antimicrobial agents. Polymerase chain reaction (PCR) was performed to characterize ambler classes A, B, and D β-lactamases, ISAba1 and integrons, biofilm formation was also investigated. Clonal relatedness was analyzed using Pulsed-Field Gel Electrophoresis (PFGE).

Results

Among 163 A. baumannii strains collected, 94.5% of them were Carbapenem-Non-Susceptible A. baumannii (CNSAB) and also 90.1 and 52.2% of them were Metallo-β-Lactamases (MBL) and Extended-Spectrum β-Lactamases (ESBL) producing isolates, respectively. Colistin and polymyxin B exhibited excellent activity against CNSAB strains. High prevalence of bla_{OXA − 23-like} (85.1%), bla_VIM (60.5%), bla_{PER − 1} (42.3%), tetB (67.8%), and Class 1 integrons (65.6%) were identified in CNSAB strains. ISAba1 element was associated with 42 (25.8%) and 129 (98.5%) of bla_OXA-51-like and bla_OXA-23-like genes, respectively. 6 clusters with the ability to form strong biofilms were found to be dominant and endemic in our entire areas.

Conclusions

Results of the present study show that antimicrobial resistance in CNSAB isolates from burn wound infections in monitored hospitals in Iran is multifactorial, and also findings of the study suggested that local antibiotic prescription policies should be regularly reviewed, and efficient infection control measures should be observed. Therefore, further strengthening of surveillance of antimicrobial resistance is urgently needed in these regions.

Evaluation of The Pathogenic Potential of Insecticidal Serratia marcescens Strains to Humans

We observed the death of insect caterpillars of Spodoptera exigua in the laboratory culture line and identified Serratia marcescens as the bacterial causative agent of the insect death. We confirmed that S. marcescens had insecticidal activity against S. exigua and caused high mortality of larvae. The LC₅₀ values of S. marcescens CFU per 1 cm² of insect diet surface were similar for all isolates. Our research reports novel strains with high pesticidal activity as candidates for future research on a new bioinsecticide. As bioinsecticides cannot be harmful to non-target organisms, we determined the pathogenic properties of S. marcescens to humans. We proved the ability of S. marcescens to damage mammalian epithelial cells. All strains had cytopathic effects to Vero cells with a cytotoxic index ranging from 51.2% ± 3.8% to 79.2% ± 4.1%. We found that all of the strains excreted catecholate siderophore - enterobactin. All isolates were resistant to sulfamethoxazole, tobramycin, gentamicin, cefepime, and aztreonam. We did not observe the ESBL phenotype and the integrons' integrase genes. Resistance to sulfamethoxazole was due to the presence of the sul1 or sul2 gene. The use of resistant S. marcescens strains that are pathogenic to humans in plant protection may cause infections difficult to cure and lead to the spread of resistance genes. The results of our study emphasize the necessity of determination of the safety to vertebrates of the bacteria that are proposed to serve as biocontrol agents. The novelty of our study lies in the demonstration of the indispensability of the bacteria verification towards the lack of hazardous properties to humans.

We observed the death of insect caterpillars of Spodoptera exigua in the laboratory culture line and identified Serratia marcescens as the bacterial causative agent of the insect death. We confirmed that S. marcescens had insecticidal activity against S. exigua and caused high mortality of larvae. The LC₅₀ values of S. marcescens CFU per 1 cm² of insect diet surface were similar for all isolates. Our research reports novel strains with high pesticidal activity as candidates for future research on a new bioinsecticide. As bioinsecticides cannot be harmful to non-target organisms, we determined the pathogenic properties of S. marcescens to humans. We proved the ability of S. marcescens to damage mammalian epithelial cells. All strains had cytopathic effects to Vero cells with a cytotoxic index ranging from 51.2% ± 3.8% to 79.2% ± 4.1%. We found that all of the strains excreted catecholate siderophore – enterobactin. All isolates were resistant to sulfamethoxazole, tobramycin, gentamicin, cefepime, and aztreonam. We did not observe the ESBL phenotype and the integrons’ integrase genes. Resistance to sulfamethoxazole was due to the presence of the sul1 or sul2 gene. The use of resistant S. marcescens strains that are pathogenic to humans in plant protection may cause infections difficult to cure and lead to the spread of resistance genes. The results of our study emphasize the necessity of determination of the safety to vertebrates of the bacteria that are proposed to serve as biocontrol agents. The novelty of our study lies in the demonstration of the indispensability of the bacteria verification towards the lack of hazardous properties to humans.

Evaluation of The Pathogenic Potential of Insecticidal Serratia marcescens Strains to Humans

We observed the death of insect caterpillars of Spodoptera exigua in the laboratory culture line and identified Serratia marcescens as the bacterial causative agent of the insect death. We confirmed that S. marcescens had insecticidal activity against S. exigua and caused high mortality of larvae. The LC₅₀ values of S. marcescens CFU per 1 cm² of insect diet surface were similar for all isolates. Our research reports novel strains with high pesticidal activity as candidates for future research on a new bioinsecticide. As bioinsecticides cannot be harmful to non-target organisms, we determined the pathogenic properties of S. marcescens to humans. We proved the ability of S. marcescens to damage mammalian epithelial cells. All strains had cytopathic effects to Vero cells with a cytotoxic index ranging from 51.2% ± 3.8% to 79.2% ± 4.1%. We found that all of the strains excreted catecholate siderophore – enterobactin. All isolates were resistant to sulfamethoxazole, tobramycin, gentamicin, cefepime, and aztreonam. We did not observe the ESBL phenotype and the integrons’ integrase genes. Resistance to sulfamethoxazole was due to the presence of the sul1 or sul2 gene. The use of resistant S. marcescens strains that are pathogenic to humans in plant protection may cause infections difficult to cure and lead to the spread of resistance genes. The results of our study emphasize the necessity of determination of the safety to vertebrates of the bacteria that are proposed to serve as biocontrol agents. The novelty of our study lies in the demonstration of the indispensability of the bacteria verification towards the lack of hazardous properties to humans.

Prevalence of Antibiotic Resistance Genes in Multidrug-Resistant Enterobacteriaceae on Portuguese Livestock Manure

The exposure of both crop fields and humans to antibiotic-resistant bacteria in animal excreta is an emergent concern of the One Health initiative. This study assessed the contamination of livestock manure from poultry, pig, dairy farms and slaughterhouses in Portugal with resistance determinants. The resistance profiles of 331 Enterobacteriaceae isolates to eight β-lactam (amoxicillin, cefoxitin, cefotaxime, cefpirome, aztreonam, ceftazidime, imipenem and meropenem) and to five non-β-lactam antibiotics (tetracycline (TET), trimethoprim/sulfamethoxazole (SXT), ciprofloxacin (CIP), chloramphenicol (CHL) and gentamicin) was investigated. Forty-nine integron and non-β-lactam resistance genes were also screened for. Rates of resistance to the 13 antibiotics ranged from 80.8% to 0.6%. Multidrug resistance (MDR) rates were highest in pig farm samples (79%). Thirty different integron and resistance genes were identified. These were mainly associated with resistance to CHL (catI and catII), CIP (mainly, qnrS, qnrB and oqx), TET (mainly tet(A) and tet(M)) and SXT (mostly dfrIa group and sul3). In MDR isolates, integron presence and non-β-lactam resistance to TET, SXT and CHL were positively correlated. Overall, a high prevalence of MDR Enterobacteriaceae was found in livestock manure. The high gene diversity for antibiotic resistance identified in this study highlights the risk of MDR spread within the environment through manure use.

Significant spread of extensively drug-resistant Acinetobacter baumannii genotypes of clonal complex 92 among intensive care unit patients in a university hospital in southern Iran

PURPOSE

Infections associated with Acinetobacter baumannii represent an increasing threat in healthcare settings. Therefore, we investigated the epidemiological relationship between clinical isolates of A. baumannii obtained from patients in a university hospital in Bandar Abbas in southern Iran.

METHODOLOGY

Sixty-four consecutive non-duplicate clinical isolates collected during 2014-2015 were subjected to susceptibility testing, clonal relationship analysis using PFGE, multilocus variable-number tandem-repeat analysis (MLVA) and multilocus sequence typing (MLST), and examined for the presence of carbapenemases and integrons.

RESULTS

Almost all A. baumannii isolates were extensively drug-resistant (XDR; 98 %) and carried an OXA carbapenemase gene (blaOXA-23-like; 98 %) and class 1 integrons (48 %). PFGE and MLST analysis identified three major genotypes, all belonging to clonal complex 92 (CC92): sequence type 848 (ST848) (n=23), ST451 (n=16) and ST195 (n=8). CC92 has previously been documented in the hospital setting in northern Iran, and ST195 has been reported in Arab States of the Persian Gulf. These data suggest national and global transmission of A. baumannii CC92.

CONCLUSION

This report demonstrates the occurrence and potential spread of closely related XDR genotypes of A. baumannii CC92 within a university hospital in southern Iran. These genotypes were found in the majority of the investigated isolates, showed high prevalence of blaOXA-23 and integron class 1, and were associated with stay in the intensive care unit. Very few treatment options remain for healthcare-adapted XDR A. baumannii, and hence effective measures are desperately needed to reduce the spread of these strains and resultant infections in the healthcare setting.

Characterization of extended spectrum β-lactamase (ESBL)-producing Escherichia coli in Asi (Orontes) River in Turkey

In this study, the presence of extended spectrum β-lactamase (ESBL)-producing Escherichia coli in aquatic environments (the Orontes River and an urban wastewater) was investigated. Fifty-four E. coli strains resistant to cefotaxime were isolated from the river waters and nearby waste water treatment plant and screened for ESBL gene variants, different classes of integrons and sulfonamide resistance genes. The ESBL-producing E. coli strains were further characterized by PhP-typing system, phylogenetic grouping and antimicrobial susceptibility testing. Of the 54 ESBL-producing strains, 14 (25.9%) belonged to four common PhP types and the remaining were of single types. CTX-M type ESBL genes were identified in 68% of the isolates. The most predominant specific CTX-M subtype identified was bla_CTX-M-15 (n = 36), followed by bla_CTX-M-1 (n = 1). None of the isolates were SHV and OXA positive. Most of the ESBL positive isolates (n = 37; 68.5%) were harboring sul gene. This study indicates a widespread distribution of CTX-M-15 producing E. coli strains in the surface waters in part of Turkey, suggesting an aquatic reservoir for ESBL genes.

Molecular screening of antibiotic-resistant determinants among multidrug-resistant clinical isolates of Proteus mirabilis from SouthWest Nigeria

BACKGROUND

Globally, and particularly in developing countries, the menace of anti-microbial resistance is an accelerating problem. In Nigeria, increase in bacterial resistance has been phenotypically established but due to high cost, few molecular studies have been reported.

OBJECTIVES

This study screened for presence of transferable resistance genes and mobile genetic elements (MGEs) such as integron among multi-drug resistant (MDR) P. mirabilis.

METHODS

A total of 108 P. mirabilis strains collected from five tertiary hospitals in SouthWest Nigeria were subjected to antibiotic susceptibility study using disc-diffusion method. Transferable resistance genes and MGEs were amplified using Polymerase chain reaction (PCR) analysis and amplicons sequenced.

RESULTS

Varied resistance was observed against all the antibiotics tested. About 56% of the isolates were MDR including those from 0-12 years old children. PCR analysis revealed the presence of aac(6')-Ib (33.3%), plasmid mediated quinolone resistance (PMQR) genes [qnrA (36.7%), acc(6')-Ib-cr (5%)], TEM (48.3%), CTX-M (6.7%) and integrons class 1 (58.3%) and class 2 (26.7%). Sequencing analysis revealed blaTEM-1, blaCTX-M-15 associated with ISEcp1 and eight different arrays of gene cassettes: aadA1, aadA1-qacH, aadB-aadA2, aadA5, dfrA7, dfrA15, dfrA17, dfrA17-aadA5.

CONCLUSION

Transferable resistance genes in association with MGEs are present in Nigerian P. mirabilis thus their potential in disseminating resistance.

Multidrug- and Extensively Drug-Resistant Uropathogenic Escherichia coli Clinical Strains: Phylogenetic Groups Widely Associated with Integrons Maintain High Genetic Diversity

In recent years, an increase of uropathogenic Escherichia coli (UPEC) strains with Multidrug-resistant (MDR) and Extensively Drug-resistant (XDR) profiles that complicate therapy for urinary tract infections (UTIs) has been observed and has directly impacted costs and extended hospital stays. The aim of this study was to determine MDR- and XDR-UPEC clinical strains, their virulence genes, their phylogenetic groups and to ascertain their relationship with integrons and genetic diversity. From a collection of 500 UPEC strains, 103 were selected with MDR and XDR characteristics. MDR-UPEC strains were mainly associated with phylogenetic groups D (54.87%) and B2 (39.02%) with a high percentage (≥70%) of several fimbrial genes (ecpA, fimH, csgA, and papGII), an iron uptake gene (chuA), and a toxin gene (hlyA). In addition, a moderate frequency (40–70%) of other genes (iutD, tosA, and bcsA) was observed. XDR-UPEC strains were predominantly associated with phylogenetic groups B2 (47.61%) and D (42.85%), which grouped with ≥80 virulence genes, including ecpA, fimH, csgA, papGII, iutD, and chuA. A moderate frequency (40–70%) of the tosA and hlyA genes was observed. The class 1 and 2 integrons that were identified in the MDR- and XDR-UPEC strains were associated with phylogenetic groups D, B2, and A, while the XDR-UPEC strains that were associated with phylogenetic groups B2, D, and A showed an extended-spectrum beta-lactamase (ESBL) phenotype. The modifying enzymes (aadA1, aadB, aacC, ant1, dfrA1, dfrA17, and aadA4) that were identified in the variable region of class 1 and 2 integrons from the MDR strains showed resistance to gentamycin (56.25 and 66.66%, respectively) and trimethoprim-sulfamethoxazole (84.61 and 66.66%, respectively). The MDR- and XDR-UPEC strains were distributed into seven clusters and were closely related to phylogenic groups B2 and D. The diversity analysis by PFGE showed 42.68% of clones of MDR-UPEC and no clonal association in the XDR-UPEC strains. In conclusion, phylogenetic groups including virulence genes are widely associated with two integron classes (1 and 2) in MDR- and XDR-UPEC strains.

ESBL-Producing Escherichia coli from Cows Suffering Mastitis in China Contain Clinical Class 1 Integrons with CTX-M Linked to ISCR1

The prevalence of pathogenic multi-drug resistant (MDR) extended-spectrum β-lactamase (ESBL)-producing Escherichia coli is rapidly increasing, becoming a global concern. In a veterinary context, ESBL-producing E. coli are mostly reported in poultry and pigs. Here, we report on the prevalence and characterize ESBL-producing E. coli isolated from diverse dairy farms in China. Overall, 36 (23.53%) out of 153 E. coli isolates from mastitic milk samples (n = 1252) were confirmed as ESBL-producers by double-disc synergy testing and PCR. Nucleotide analysis of PCR amplicons revealed that bla_CTX-M was the predominant ESBL gene detected in 28 (77.78%) isolates, with bla_CTX-M-15 being the major (78.57%) allele encoding for ESBLs. Also, 20 (55.56%) and 6 (16.67%) of the ESBL isolates were carrying bla_TEM and bla_SHV genes, respectively, in singlet or in combination. The majority of these isolates belonged to phylo-group A (69.44%) and D (16.67%). Strikingly, all these isolates were found to be MDR showing high resistance to cephalosporins including the fourth generation cefepime and common non β-lactams. Additionally, class 1 integrons (intI1) were found in 30 (83.33%) isolates. Analysis of the class 1 integrons variable regions indicated that they were carrying up to five different gene cassettes conferring resistance to various drugs with a predominant combination of dfrA17-aadA5 genes in tandem, conferring resistance to aminoglycosides and trimethoprim. However, no ESBL encoding genes were found in the cassettes. Interestingly, 22 (66.11%) of the ESBL isolates were also carrying insertion sequence common region 1 (ISCR1) which was found to be associated with most of the CTX-M genes. Altogether, the current study reports on the high prevalence of ESBL-positive E. coli, particularly CTX-M-15, carrying clinical class 1 integrons and ISCR1 elements are likely indicative of their rapid and wider dissemination, posing threats to veterinary and public health. To the best of our knowledge, this is the first comprehensive study to report on the alarming high occurrence of ESBL-producing E. coli from mastitic cows in China.

Abundance of Class 1 Integron-Integrase and Sulfonamide Resistance Genes in River Water and Sediment Is Affected by Anthropogenic Pressure and Environmental Factors

In this study, we determined the presence of class 1 integron-integrase gene in culturable heterotrophic bacteria isolated from river water and sediment sampled upstream and downstream of a wastewater treatment plant effluent discharge. Moreover, we quantified intI1 and sulfonamide resistance genes (sul1 and sul2) in the water and sediment using qPCR. There was no correlation between the results from water and sediment samples, which suggests integron-containing bacteria are differentially retained in these two environmental compartments. The discharge of treated wastewater significantly increased the frequency of intI1 among culturable bacteria and the gene copy number in river water, and increased the number of sul1 genes in the sediment. We also observed seasonal differences in the frequency of the class 1 integron-integrase gene among culturable heterotrophs as well as intI1 copy number in water, but not in sediment. The results suggest that the abundance of class 1 integrons in aquatic habitat depends on anthropogenic pressure and environmental factors.

Class 1 integrase, sulfonamide and tetracycline resistance genes in wastewater treatment plant and surface water

Wastewater treatment plants are considered hot spots for multiplication and dissemination of antibiotic-resistant bacteria and resistance genes. In this study, we determined the presence of class 1 integron integrase and genes conferring resistance to tetracyclines and sulfonamides in the genomes of culturable bacteria isolated from a wastewater treatment plant and the river that receives the treated wastewater. Moreover, using PCR-based metagenomic approach, we quantified intI1, tet and sul genes. Wastewater treatment caused the decrease in the total number of culturable heterotrophs and bacteria resistant to tetracycline and sulfonamides, along with the decrease in the number of intI1, sul and tet gene copies per ml, with significant reduction of tet(B). On the other hand, the treatment process increased both the frequency of tetracycline- and sulfonamide-resistant bacteria and intI1-positive strains, and the relative abundance of all quantified antibiotic resistance genes (ARGs) and intI1 gene; in the case of tet(A) and sul2 significantly. The discharge of treated wastewater increased the number of intI1, tet and sul genes in the receiving river water both in terms of copy number per ml and relative abundance. Hence, despite the reduction of the number of ARGs and ARBs, wastewater treatment selects for bacteria with ARGs in effluent.

Providencia stuartii Isolates from Greece: Co-Carriage of Cephalosporin (blaSHV-5, blaVEB-1), Carbapenem (blaVIM-1), and Aminoglycoside (rmtB) Resistance Determinants by a Multidrug-Resistant Outbreak Clone

Providencia stuartii has emerged as an important nosocomial pathogen. We describe an outbreak due to a multidrug-resistant strain over a 4-month period in a critical care unit in Athens. Molecular typing revealed each of the isolates to be clonally related with coresistance to cephalosporins, carbapenems, aminoglycosides, and quinolones. Each isolate contained a 220-kb multi-replicon (IncA/C and IncR) conjugative plasmid encoding TEM-1, SHV-5, VEB-1, and VIM-1 β-lactamases and the 16S rDNA methylase RmtB. Antimicrobial therapy was unsuccessful in 3 of 6 cases, and resistance was readily transmissible to susceptible strains of Escherichia coli by transformation and conjugation. This highlights the clinical importance of P. stuartii and its ability to disseminate critical resistance determinants to other bacterial pathogens.

Wide distribution of carbapenem resistant Acinetobacter baumannii in burns patients in Iran

Antimicrobial resistance in carbapenem non-susceptible Acinetobacter baumannii (CNSAb) is a major public health concern globally. This study determined the antibiotic resistance and molecular epidemiology of CNSAb isolates from a referral burn center in Tehran, Iran. Sixty-nine CNSAb isolates were tested for susceptibility to antimicrobial agents using the E test methodology. Multiple locus variable number tandem repeat analysis (MLVA), Multilocus sequence typing (MLST) and multiplex PCR were performed. PCR assays tested for ambler classes A, B, and D β-lactamases. Detection of ISAba1, characterization of integrons, and biofilm formation were investigated. Fifty-three (77%) isolates revealed XDR phenotypes. High prevalence of bla_OXA-23-like (88%) and bla_PER-1 (54%) were detected. ISAba1 was detected upstream of bla_ADC, bla_OXA-23-like and bla_OXA51-like genes in, 97, 42, and 26% of isolates, respectively. Thirty-one (45%) isolates were assigned to international clone (IC) variants. MLVA identified 56 distinct types with six clusters and 53 singleton genotypes. Forty previously known MLST sequence types forming 5 clonal complexes were identified. The Class 1 integron (class 1 integrons) gene was identified in 84% of the isolates. The most prevalent (33%) cassette combination was aacA4-catB8-aadA1. The IC variants were predominant in the A. baumannii lineage with the ability to form strong biofilms. The XDR-CNSAb from burned patients in Iran is resistant to various antimicrobials, including tigecycline. This study shows wide genetic diversity in CNSAb. Integrating the new Iranian A. baumannii IC variants into the epidemiologic clonal and susceptibility profile databases can help effective global control measures against the XDR-CNSAb pandemic.

Prevalence and characteristics of extended-spectrum β-lactamase genes in Escherichia coli isolated from piglets with post-weaning diarrhea in Heilongjiang province, China

OBJECTIVES

The purpose of this study was to investigate the prevalence of extended spectrum β-lactamase (ESBL) genes in Escherichia coli isolated from post-weaning diarrhea (PWD) piglets in Heilongjiang province, China.

METHODS

Of 458 E. coli isolated from 589 fecal samples from PWD piglets, a total of 198 isolates were confirmed as ESBL producers by the double-disk synergy test (DDST). Polymerase chain reaction (PCR) and sequencing were performed to identify genes for ESBL, plasmid-mediated quinolone resistance (PMQR), and integrons.

RESULTS

Of the 198 isolates, bla CTX-M and bla TEM were detected in 191 and 149 isolates, respectively. Sequencing revealed that 10 bla CTX-M subtypes were detected, and bla CTX-M-14 was the most prevalent, followed by bla CTX-M-55 and bla CTX-M-65. Of the 149 TEM-positive strains, four were bla TEM-52 and the rest were bla TEM-1. Among the 198 ESBL-positive isolates, 173 isolates were found to harbor at least one PMQR gene, with oqxAB, qnrS, qnrB, qepA, and aac(6')-Ib-cr being detected alone or in combination in 125, 114, 26, 24, and 45 strains, respectively. One hundred and fifty-five ESBL-positive isolates were also positive for class I integron (int1), and eight different gene cassette arrays were confirmed in 110 isolates by restriction fragment length polymorphism (RFLP) and DNA sequencing analyses, with predominance of dfrA17-aadA5, dfrA12-orfF-aadA2, and dfrA1-aadA1 arrays.

CONCLUSION

To the best of our knowledge, this is the first report of the bla TEM-52 gene in pig E. coli isolates in China and this is also the first description of the coexistence of the qnrB, qnrS, aac(6')-Ib-cr, qepA, and oqxAB genes in one E. coli strain.

Environmental Isolate of Rahnella aquatilis Harbors Class 1 Integron

The paper presents first description of class 1 integron in an environmental strain of Rahnella aquatilis, a rarely isolated Gram-negative bacterium of the family Enterobacteriaceae. The strain was isolated from the Warta river water, Poland. Class 1 integrase gene was detected by a PCR assay. Sequencing of the integron’s variable region showed the presence of a dfrA1-aadA1 gene cassette array. The integron was located in a 54-kbp plasmid that was transferable to Escherichia coli J-53 recipient strain in a conjugation assay. The integron-bearing R. aquatilis strain was resistant to aminoglycosides, penicillins, trimethoprim, sulfamethoxazole, and trimethoprim/sulfamethoxazole. This paper confirms that water environment play a major role in the spread of integrons and, consequently, antimicrobial resistance, among bacteria of various genera.

Molecular Identification of Resistance Determinants, Integrons and Genetic Relatedness of Extensively Drug Resistant Acinetobacter baumannii Isolated From Hospitals in Tehran, Iran

Background:

Acinetobacter baumannii has emerged as an important nosocomial pathogen. Hospital outbreaks of extensively drug resistant (XDR) A. baumannii are a great concern.

Objectives:

Aims of this study were to characterize the resistance determinants and genetic relatedness of (XDR) A. baumannii isolates in hospitals in Tehran, Iran.

Materials and Methods:

During a three-year study, clinical isolates of A. baumannii were collected from two hospitals in Tehran, Iran. Susceptibility testing to antibiotics was performed by disk diffusion method and XDR A. baumannii isolates were identified. Genes’ encoding for carbapenemase production and integrons were identified by PCR. MICs of imipenem and meropenem were determined by agar dilution. Multiple locus variable-number tandem repeat analysis (MLVA) typing was used to determine genetic relationships of XDR isolates.

Results:

Using PCR for amplification of bla_OXA-51, 93.9% (123.131) of isolates were identified as A. baumannii and 24.4% (30.123) were XDR. These isolates were resistant to gentamicin, ciprofloxacin, amikacin, cotrimoxazole, cefepime, cefotaxime, aztreonam and ceftazidime. Thirty percent of the isolates were resistant to tigecycline. All isolates were susceptible to colistin and polymyxin-B, while 93.3% (28.30) possessed bla_OXA-23-like and 6.7% (2.30) possessed bla_OXA-24-like. All isolates possessed insertion sequence (ISAba1) in the upstream region of the _OXA-23-like gene. Almost 96.7% (29.30) of the isolates were positive for class I integron and 43.3% (13.30) for class II. These isolates were also positive for class I. Class III integron was not detected. MLVA typing of XDR isolates showed seven clonally complexes and 16 singletons.

Conclusions:

The population structure of the A. baumannii isolates in our hospitals was genetically diverse. A significant association between XDR pattern and presence of class 1 integron (P < 0.001) was found indicating that many antibiotic resistance determinants are involved in development of XDR strains.

Class 1 integrons and antibiotic resistance of clinical Acinetobacter calcoaceticus-baumannii complex in Poznań, Poland

Sixty-three clinical isolates of Acinetobacter calcoaceticus-baumannii complex were analyzed for the presence of integrons and antimicrobial resistance. Class 1 integrons were detected in 40 (63.5 %) isolates. None of them had class 2 or class 3 integrons. The majority of the integrons contained aacC1-orfA-orfB-aadA1 gene cassette array. The presence of integrons was associated with the increased frequency of resistance to 12 of 15 antimicrobials tested, multi-drug resistance phenotype, and the overall resistance ranges of the strains.

An investigation of total bacterial communities, culturable antibiotic-resistant bacterial communities and integrons in the river water environments of Taipei city

The intensive use of antibiotics may accelerate the development of antibiotic-resistant bacteria (ARB). The global geographical distribution of environmental ARB has been indicated by many studies. However, the ARB in the water environments of Taiwan has not been extensively investigated. The objective of this study was to investigate the communities of ARB in Huanghsi Stream, which presents a natural acidic (pH 4) water environment. Waishuanghsi Stream provides a neutral (pH 7) water environment and was thus also monitored to allow comparison. The plate counts of culturable bacteria in eight antibiotics indicate that the numbers of culturable carbenicillin- and vancomycin-resistant bacteria in both Huanghsi and Waishuanghsi Streams are greater than the numbers of culturable bacteria resistant to the other antibiotics tested. Using a 16S rDNA sequencing approach, both the antibiotic-resistant bacterial communities (culture-based) and the total bacterial communities (metagenome-based) in Waishuanghsi Stream exhibit a higher diversity than those in Huanghsi Stream were observed. Of the three classes of integron, only class I integrons were identified in Waishuanghsi Stream. Our results suggest that an acidic (pH 4) water environment may not only affect the community composition of antibiotic-resistant bacteria but also the horizontal gene transfer mediated by integrons.

Epidemiological characterizations of class 1 integrons from multidrug-resistant acinetobacter isolates in Daejeon, Korea

Background

Multidrug-resistant (MDR) Acinetobacter spp. acquire antimicrobial agent-resistance genes via class 1 integrons. In this study, integrons were characterized to investigate the antimicrobial resistance mechanisms of MDR Acinetobacter isolates. In addition, the relationship between the integron type and integron-harboring bacterial species was analyzed by using epidemiological typing methods.

Methods

Fifty-six MDR Acinetobacter spp.-A. baumannii (N=30), A. bereziniae (N=4), A. nosocomialis (N=5), and A. pittii (N=17)-were isolated. The minimum inhibitory concentrations (MICs) were determined on the basis of the results of the Epsilometer test (Etest). PCR and DNA sequencing was performed to characterize the gene cassette arrays of class 1 integrons. Multilocus sequence typing (MLST) and repetitive extragenic palindromic sequence (REP)-PCR were performed for epidemiological typing.

Results

Class 1 integrons were detected in 50 (89.3%) of the 56 isolates, but no class 2 or 3 integron was found within the cohorts. The class 1 integrons were classified into 4 types: 2.3-kb type A (aacA4-catB8-aadA1), 3.0-kb type B (aacA4-blaI_MP-1-bla_OXA-2), 3.0-kb type C (bla_VIM-2-aacA7-aadA1), and 1.8-kb type D (aac3-1-bla_OXA-2-orfD). Type A was most prevalent and was detected only in A. baumannii isolates, except for one A. bereziniae isolate; however, type B was amplified in all Acinetobacter isolates except for A. baumannii isolates, regardless of clone and separation time of the bacteria.

Conclusions

Although class 1 integron can be transferred horizontally between unrelated isolates belonging to different species, certain types of class 1 integrons tend to transfer horizontally and vertically among A. baumannii or non-baumannii Acinetobacter isolates.

Phylogenetic and molecular insights into the evolution of multidrug-resistant porcine enterotoxigenic Escherichia coli in Australia

This study investigated the phylogeny and molecular epidemiology of Australian porcine enterotoxigenic Escherichia coli (ETEC) isolates (n=70) by performing multilocus sequence typing (MLST), random amplified polymorphic DNA (RAPD) analysis, virulence gene analysis, plasmid, bacteriocin, integron and antimicrobial resistance gene typing, and antimicrobial susceptibility phenotyping. Isolates of the most commonly observed O serogroup (O149) were highly clonal with a lower frequency of antimicrobial resistance compared with the less common O141 serogroup isolates, which were more genetically diverse and resistant to a greater array of antimicrobials. The O149 and O141 isolates belonged to sequence types (STs) ST100 and ST1260, respectively. A small number of new STs were identified for the least common serogroups, including O157 (ST4245), O138 (ST4244), O139 (ST4246) and O8 (ST4247). A high frequency of plasmid replicons was observed among all ETEC isolates. However, O149 isolates predominantly carried IncFIB, I1, HI1 and FIC, whereas O141 isolates carried a more varied array, including IncI1, FIB, FIC, HI1, I1, Y and, most significantly, A/C. O141 isolates also possessed a greater diversity of bacteriocins, with almost one-half of the isolates carrying colicin E3 (44.4%; 12/27) and E7 (48.1%; 13/27). This study shows that Australian porcine ETEC are distinct from isolates obtained in other parts of the world with respect to the MLST profile and the absence of resistance to critically important antimicrobials, including third-generation cephalosporins and fluoroquinolones.

Extended-spectrum β-lactamase producing Escherichia coli in hospital wastewaters and sewage treatment plants in Queensland, Australia

We investigated the prevalence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli in untreated hospital wastewaters and 2 sewage treatment plants (STPs). A collection of 252 ESBL-producing E. coli isolates from hospital wastewater and STPs were typed and tested for resistance to 17 antimicrobial agents and for the presence of integron-associated integrases (intI gene) and ESBL genes. Eighty-nine percent (n = 176) of the ESBL-producing E. coli strains from hospital wastewater were found in more than 1 sample (common types), with 1 common type accounting for 35% of isolates, found in all samples. These strains were also resistant to up to 9 non-β-lactam antibiotics and showed the same pattern of resistance in all samples. More than 73% of the hospital wastewater isolates possessed SHV-type ESBL as opposed to isolates from STPs that carried only CTX-M-type ESBL genes. The prevalence of the intI gene did not differ between the sources of the isolates. Certain ESBL-producing E. coli were dominant in hospital wastewaters. These strains possessed β-lactamase genes that were different from isolates found in STPs. From a public health point of view, the presence of such a high level of ESBL-producing E. coli strains in hospital wastewaters is of great importance.

Novel cassette array in a class 1 integron in clinical isolates of Acinetobacter baumannii from central Iran

Antibiotic resistance in Acinetobacter baumannii is a major problem in the hospital and outbreaks caused by this organism have been reported frequently. The present study aimed at determining the antibiotic susceptibility patterns, the prevalence of different classes of integrons and the characterization of integron class 1 gene cassettes in Iranian A. baumannii isolates. A total of 63 non-duplicate A. baumannii isolates were collected from clinical and environmental specimens in the Vali-Asr hospital in the central province of Iran (March to September, 2011). The antimicrobial susceptibility for 15 antibiotics which are used conventionally was determined by disk diffusion. The presence of different integron classes was investigated by PCR and the size of gene cassettes in class 1 integrons was then determined by PCR as well. Moreover, integron cassette arrays of isolates were delineated by RFLP and sequencing amplicons with different lengths. Of 63 isolates 62 (98.4%) carried a class 1 integron. The prevalence of IntI2 was 15.9% and the length of the amplicons ranged from 500 bp to 3 kb. Sequencing of integrons of class 1 revealed the presence of many resistance genes (aadA, aacA, aacC, dfrA, bla(GES) and bla(IMP)). We identified a completely new gene cassette which contained aacA7-qacF-aadA5-bla(IMP), this cassette has not been reported previously in A. baumannii.

Association between the presence of class 1 integrons, virulence genes, and phylogenetic groups of Escherichia coli isolates from river water

Ninety-six class 1 integron-positive and 96 integron-negative Escherichia coli isolates cultured from the water of the Warta River, Poland, were characterized for their phylogenetic group affiliation and for the presence of genes associated with virulence. Most strains belonged to phylogenetic group A, but phylogenetic group affiliation was not related with the presence of integrons. The occurrence of heat-stable toxin gene of enterotoxigenic E. coli, S fimbriae subunit gene sfaS, and siderophore receptor genes, fyuA and iutA, was associated with the presence of class 1 integrons. Moreover, virulence factor score (the total number of virulence-associated genes) was associated with the presence of integrons in groups. The results bring new insight into relations between the presence of integrons in E. coli, virulence traits, as well as phylogenetic group affiliation.

Increased frequency of integrons and β-lactamase-coding genes among extraintestinal Escherichia coli isolated with a 7-year interval

We analyzed the level of antimicrobial resistance, and the presence of integrons and β-lactamase-coding genes in 69 clinically relevant Escherichia coli strains originating from extraintestinal infections isolated in 1999–2001 and 2008–2010. Comparison of the two groups showed significant differences in drug resistance frequency, and the presence of integron and β-lactamase-coding genes. The frequency of resistance to all antimicrobials beside imipenem, streptomycin, piperacillin/tazobactam, and sulfamethoxazole increased significantly, especially towards aminoglycosides, β-lactams and fluoroquinolones. Similarly, we noticed an increase in the number of strains with integrons from 31.6 to 80.7 %. The presence of integrase genes was associated with elevated frequency of resistance to each antimicrobial tested besides imipenem, piperacillin/tazobactam and ceftazidime. The presence of integrons was also associated with multidrug resistance phenotype. The genetic content of integrons comprised genes determining resistance toward aminoglycosides, sulfonamides and trimethoprim. Moreover, we noticed a significant increase in the frequency of bla_CTX-M β-lactamases, with appearance of bla_CTX-M-15 variant and newer plasmid-encoded β-lactamases like CMY-15 and DHA. The emergence of strains resistant to several classes of antimicrobials and carrying integrons, ESBL and AmpC β-lactamase-coding genes may predict the spread of isolates with limited treatment options.

Multiresistant Enterobacteriaceae with class 1 and class 2 integrons in a municipal wastewater treatment plant

In this study, 1832 strains of the family Enterobacteriaceae were isolated from different stages of a municipal wastewater treatment plant, of which 221 (12.1%) were intI-positive. Among them 61.5% originated from raw sewage, 12.7% from aeration tank and 25.8% from the final effluent. All of the intI-positive strains were multiresistant, i.e. resistant to at least three unrelated antimicrobials. Although there were no significant differences in resistance range, defined as the number of antimicrobial classes to which an isolate was resistant, between strains isolated from different stages of wastewater treatment, for five β-lactams the percentage of resistant isolates was the highest in final effluent, which may reflect a selective pressure the bacteria are exposed to, and the possible route of dissemination of β-lactam resistant strains to the corresponding river. The sizes of the variable part of integrons ranged from 0.18 to 3.0 kbp and contained up to four incorporated gene cassettes. Sequence analysis identified over 30 different gene cassettes, including 24 conferring resistance to antibiotics. The highest number of different gene cassettes was found in bacteria isolated from the final effluent. The gene cassettes were arranged in 26 different resistance cassette arrays; the most often were dfrA1-aadA1, aadA1, dfrA17-aadA5 and dfrA12-orfF-aadA2. Regarding the diversity of resistance genes and the number of multiresistant bacteria in the final effluent, we concluded that municipal sewage may serve as a reservoir of integron-embedded antibiotic resistance genes.