Classes Of Integrons Research Articles

Characterization of drug-resistance and molecular epidemiology of Enterobacter cloacae among patients with clinical infections in a teaching hospital, China

A total of 114 non-repetitive Enterobacter cloacae isolates were collected from patients with clinical infections and tested for susceptibility to 15 antimicrobials. Enterobacterrepetitive intergenic consensus (ERIC) analysis was used to determine the genetic relatedness between isolates with enzymes. Touchdown polymerase chain reaction (PCR) and single PCR were used to detecting the genes encoding beta-lactamase (single PCR rechecked) and integron, aac-(6’)-Ib, respectively. Transferability of drug-resistant was studied by conjugation experiments. 41.2% strains possessed one or two AmpC β-lactamase genes, and 29.8% isolates harbored one or more broad-spectrum beta-lactamase genes. While aac(6’)-Ib was detected in six isolates. 26 isolates were detected with class1 integron and four different gene cassettes were found in these strains. None of isolate was carbapenemase producer. Patients with these bacterial infections suffered a failure of different cephalosporin treatment in clinical. The presence of producing ESBLs, AmpC β-lactamase was correlated with the reduced susceptibility to carbapenems among E. cloacae. In addition, these genes could transmit between different species by plasmids and enhanced by insertion sequences. ERIC revealed 11 unrelated profiles, which indicated that there was scattered transmission among E. cloacae with enzymes in the hospital environment, even acrossed more than three years. Key words: Enterobacter repetitive intergenic consensus, integron, plasmid, resistance.

The Versatility of Delftia sp. Isolates as Tools for Bioremediation and Biofertilization Technologies

Two Pb(II)-resistant bacteria isolated from a soil containing 2,500 mg/kg of Pb were identified by 16S rRNA sequencing analysis as Delftia sp. and designated as 3C and 6C. Both isolates grew at a Pb(II) concentration of 62 mg/L and at the stationary phase showed a Pb(II)-sorption capability of 10 ± 1.5 (3C) and 5 ± 0.8 (6C) mg/g of biomass. Biochemical properties related to heavy metal resistance and plant growth promotion were analyzed and compared with the Cr(VI)-resistant plant growth-promoting Delftia sp. JD2, previously reported by our group. Both isolates and JD2 were resistant to Cr(VI), Pb(II) and many antibiotics, produced siderophores and the phytohormone indole-3-acetic, and showed clover growth-promoting activity in greenhouse conditions. Interestingly, the occurrence of integron class 1 was shown in all isolates. Our results add to previous reports and suggest that bacteria of the genus Delftia could be consider as good candidates for the design of technologies for cleaning up contaminated environments and/or the production of biofertilizers.

Beta-lactams resistance and presence of class 1 integron in Pseudomonas spp. isolated from untreated hospital effluents in Brazil

The aim of the present study was to investigate the resistance profile, to detect the presence of beta-lactam resistance genes, phenotypic expression of efflux pump systems and class 1 integrons in Pseudomonas spp. strains obtained from untreated hospital effluents. Effluent samples were collected from four hospitals in Porto Alegre, RS, Brazil. Pseudomonas were isolated on MacConkey agar plates and the identification was confirmed by 16S rRNA PCR and biochemical tests. Susceptibility testing was determined by disk-diffusion method using 11 different beta-lactams and MIC assays were performed on isolates resistant to imipenem and ceftazidime. The beta-lactamase genes bla (IMP), bla (VIM), bla (SPM-1), bla (OXA-23-like), bla (OXA-24-like), bla (OXA-51-like) and the intl1 gene from class 1 integron were analysed by PCR. One hundred and twenty-four isolates were recovered and the most common species was Pseudomonas pseudoalcaligenes. The resistance found among the isolates was considered high, 62 (50%) isolates were multiresistant. No isolate carrying the beta-lactamase genes tested was found among the strains. Seven isolates showed reduction of MIC for imipenem and ceftazidime in the presence of cyanide m-chlorophenylhydrazone, indicating the hyper expression of efflux pumps. From the 124 isolates, 52 (41.9%) were identified as carrying the class 1 integron gene, intI1. Untreated hospital effluents could be a source of environmental contamination due to discharge of antimicrobial resistant bacteria which can carry integron class 1 and act as a reservoir of resistance genes and have efflux pump systems.

Inability of Some Aeromonas hydrophila Strains to Act as Recipients of Plasmid pRAS1 in Conjugal Transfer Experiments

Plasmids belonging to the IncU incompatibility group are mobile genetic elements isolated frequently from Aeromonas spp. These plasmids share structural and functional characteristics and often carry Class-1 integrons bearing antibiotic resistance genes. In this work the ability of two IncU plasmids, pAr-32 and pRAS1 to establish in different A. hydrophila strains after conjugal transfer was studied. In vitro transfer frequencies on solid surface ranged from 10(-1) to 10(-6) for pAr-32 and from 10(-3) to 10(-5) for pRAS1. While carrying out these experiments we detected four strains unable to acquire plasmid pRAS1, indicating that the genetic background of recipients affects the establishment of the plasmid. We explored the possible reasons why these strains failed to yield transconjugants after mating experiments using A. salmonicida 718 as a donor. Factors included donor cell recognition, incompatibility, surface exclusion and restriction of incoming DNA. We found that none of these factors could explain the refractivity of non-receptive A. hydrophila strains to yield transconjugants. Although we do not know the reasons of this refractivity, we may speculate that these isolates lack a product necessary to replicate or stabilize plasmid pRAS1. Alternatively, these strains could contain a product that impedes plasmid establishment.

Antimicrobial Drug Resistance in Corynebacterium diphtheriae mitis

Antimicrobial Drug Resistance in Corynebacterium diphtheriae mitis

Integron and genotype patterns of quinolones-resistant uropathogenic Escherichia coli

Uropathogenic Escherichia coli are the most common cause of urinary tract infections,and quinolones-resistant strains cause growing concern in developing countries. This study provides relevant data in relation to the molecular epidemiology of these isolateswith respect to the distribution of integron among them and in doing so, to control the infections and adopt efficient strategies. This study was performed on 96 strains of E. coliisolated from patients with community acquired urinary tract infections in Jahrom, Iran. Having determined the antibiotic susceptibility patterns, isolates were resistant to quinolones (Ciprofloxacin, Norfloxacin and Nalidixic acid) screened for integron classes by polymerase chain reaction (PCR). Then the genetic patterns of the strains were compared by pulsed field gel electrophoresis. Of the 96 samples, 30 were resistant to at least one of the above mentioned antibiotics. Integrons were detected in 20.8, 25 and 25% of the Nalidixic acid, Ciprofloxacin and Norfloxacin resistant isolates, respectively. By using pulsed field gel electrophoresis among the 30 samples, we obtained 30 genetic patterns. The patterns revealed no clonal relationships between the strains. The gene cassettes observed in class 1 and 2 integrons did not correlate completely with the quinolone resistance observed in these isolates. Key words: Quinolones-resistant uropathogenic Escherichia coli, pulsed field gel electrophoresis, integrons.

Characterization of integrons in multiple antimicrobial resistant Escherichia coli isolates from bovine endometritis

To assess the prevalence of antimicrobial resistance and three classes of integrons in Escherichia coli ( E. coli) strains ( n = 57) isolated from bovine endometritis in Inner Mongolia of China, antimicrobial susceptibility and the presence of three types of integrons were characterized. Most isolates were susceptible to ceftiofur, furazolidone, ciprofloxacin and enrofloxacin, while 57 isolates were all resistant to sulfamethoxydiazine and trimethoprim. High resistant incidence rates were exhibited to sulfadiazine, tetracycline, oxytetracycline, cefazolin, chloramphenicol. Forty-six of 57 E. coli strains were resistant to above 10 antibiotics (80.70%). The integrase gene and gene cassettes of integrons were amplified by PCR. DNA sequencing and analysis were used to identify the genetic content of the integron-variable regions. Neither class II nor class III integron was detected, while 36.8% ( n = 21) of the isolates were positive for the presence of intI1 gene. Analysis of gene cassettes revealed that six gene cassettes were found, which encoded resistance to trimethoprim ( dhfr, dhfrI, dfrA17) and aminoglycosides ( aadA1, aadA2, aadA5) . Among them, the gene cassette array dfrA17–aadA5 was found most prevalent (66.7%). The resistance profile of positive-integron isolates was relatively broad and they were resistant to more than eight antimicrobials ( n ⩾ 8). The correlation analysis revealed the incidence of integrons among the isolates were related to the multiple antibiotic resistance profile, indicating integrons play an important role in the dissemination and spread of the antimicrobial resistant strains.

Dissemination of Class 1, 2 and 3 Integrons among Different Multidrug Resistant Isolates of Acinetobacter baumannii in Tehran Hospitals, Iran

A total of 100 non-duplicate Acinetobacter baumannii isolates were collected from different hospitals in Tehran and were confirmed as A. baumannii by conventional biochemical and API testing. Antimicrobial susceptibility of these isolates was checked by a disk diffusion method in accordance with CLSI guidelines. The isolates were then detected as carrying class 1 and 2 integron gene cassettes by PCR evaluation and then genotyped by REP-PCR. More than 50% (n = 50) of the isolates were multidrug resistant. The results showed that more than 80% of all multidrug resistant A. baumannii strains carry a class 1 integron. Distribution of IntI 1 and IntI2 among A. baumannii isolates was 58% and 14%, respectively. Analysis of a conserved segment of class 1 integron showed a range from 100 bp to 2.5 kb. REP-PCR fingerprinting showed more than 20 genotypes among A. baumannii strains. TIhere was no relationship between REP genotypes and the distribution of different classes of integrons. This is a comprehensive study on the distribution of different classes of integrons among A. baumannii in Iran. Considering the exact role of integrons in coding drug resistance in bacteria, the findings of this study could help us find antimicrobial resistant mechanisms among A. baumannii isolates in Iran.

Association between Existence of Integrons and Multi-Drug Resistance in Acinetobacter Isolated from Patients in Southern Iran

Nosocomial infections caused by multi-drug resistant Acinetobacter pose a serious problem in many countries. This study aimed at determining the antibiotic susceptibility patterns and prevalence of different classes of integrons in isolated Acinetobacter. In addition, the association between production of specific bands in PCR assay and magnitude of multi-drug resistance was investigated. In total, 88 Acinetobacter strains were isolated from patients from October 2008 through September 2009. The Minimal inhibitory concentration (MIC) of 12 antibiotics conventionally used in clinics against the isolates, was determined by E-test method. The existence of integron classes was investigated by PCR assay through the amplification of integrase genes. The most effective antibiotic against Acinetobacter was colistin with 97.7% activity, followed by imipenem (77.3%) and meropenem (72.7%). The presence ofintegron classes 1 and 2 in 47 (53.4%) isolates was confirme, However, no class 3 was detected. The proportion of class 1, compared with class 2, was high (47.7% vs. 3.4%). The association between multi-drug resistance to norfloxacin, ceftazidime, gentamicin, ciprofloxacin, cefepime and amikacin and the presence of integrons was statistically significant. However, the association was not remarkable in many of the isolates which exhibited resistance to the rest of antibiotics. This may imply that in addition to integrons, other resistance determinants such as transposon and plasmid may also contribute to resistance. To reduce the pressure on sensitive isolates, comprehensive control measures should be implemented. Furthermore, wise application of effective antibiotics could help alleviate the situation. Colistin is the most effective antibiotic in vitro against Acinetobacter.

Comparison of Acinetobacter baumannii multidrugs resistant Isolates obtained from French and Tunisian hospitals

Objectives: The aim of this study was to assess whether there are differences between the clustering of isolates collected between 2003 and 2005 from two different hospitals in Tunisia and France. Methods: A selection of 62 isolates of A. baumannii was studied; 31 from the French Hospital (Poitiers) and 31 from Tunisian Hospital (Rabta). Antibiograms were done using the disc diffusion method. The presence of integrons class 1 and 2 was studied by PCR. Molecular relationship was studied by Random Amplified Polymorphic DNA (RAPD) and Pulsed Field Gel Electrophoresis (PFGE). The sequence typing of adeB gene was determined to identify intraspecific groups. Results: The present study successfully focuses to compare epidemiologic status between two hospitals study. PFGE and RAPD methods were useful to distinguish epidemic and endemic clones in the two collections study. Sequence analysis of an 850-bp internal fragment drug efflux gene adeB revealed 9 novel sequence types (STs). Conclusion: We, statistically, found no significant difference related to the epidemiological situation. This study showed that different genetic types of A.baumannii were found in the two collection strains. Epidemics ones were essentially confined in the ICU and were persisting during the two years study. However, more control procedures had to be used on these clones for the Tunisian hospital.

Antimicrobial resistance patterns and prevalence of class 1 and 2 integrons in Shigella flexneri and Shigella sonnei isolated in Uzbekistan

BackgroundShigella is a frequent cause of bacterial dysentery in the developing world. Treatment with effective antibiotics is recommended for shigellosis, but options become limited due to globally emerging resistance. One of the mechanisms for the development of resistance utilizes integrons. This study described the antibiotic susceptibility and the presence of class 1 and 2 integrons in S. flexneri and S. sonnei isolated in Uzbekistan.ResultsWe studied 31 isolates of S. flexneri and 21 isolates of S. sonnei isolated in Uzbekistan between 1992 and 2007 for the susceptibility or resistance to ampicillin (Am), chloramphenicol (Cl), tetracycline (Te), co-trimoxazole (Sxt), kanamycin (Km), streptomycin (Str), gentamicin (Gm), cefazolin (Czn), cefoperazone (Cpr), cefuroxime (Cur), ceftazidime (Ctz), nalidixic acid (NA) and ciprofloxacin (Cip). Am/Str/Cl/Te and Am/Str/Cl/Te/Sxt resistance patterns were found most frequently in S. flexneri. Single isolates were resistant to aminoglycoside, quinolones and cephalosporins. The resistance patterns were different in the two species. Integrons were detected in 93.5% of S. flexneri (29/31) and 81.0% of S. sonnei (17/21) isolates. In addition, 61.3% of S. flexneri (19/31) isolates and 19.0% of S. sonnei (4/21) isolates carried both classes of integrons. In 29.0% of S. flexneri (9/31) isolates, only class 1 integrons were identified. In S. flexneri isolates, the presence of class 1 integrons was associated with resistance to ampicillin and chloramphenicol. Only Class 2 integrons were present in 61.9% of S. sonnei (13/21) isolates.ConclusionsOur study documents antibiotic resistance among Shigella spp. in Uzbekistan. Ninety percent of Shigella strains were resistant to previously used antibiotics. Differences among S. flexneri and S. sonnei isolates in patterns of antimicrobial resistance to routinely used shigellosis antibiotics were observed. The majority of S. flexneri were resistant to ampicillin, chloramphenicol, tetracycline and streptomycin. Class 1 and 2 integrons were widely present in these Shigella strains. Resistance to ampicillin/chloramphenicol was associated with the presence of class 1 integrons. Though several mechanisms are possible, the resistance of Shigella isolates to ampicillin/chloramphenicol may be associated with the expression of genes within class 1 integrons.

Quantitative multiplex real-time PCR for detecting class 1, 2 and 3 integrons

Integrons are bacterial genetic elements that can capture and express genes contained in mobile cassettes. Integrons have been described worldwide in Gram-negative bacteria and are a marker of antibiotic resistance. We developed a specific and sensitive Taqman probe-based real-time PCR method with three different primer-probe pairs for simultaneous detection of the three main classes of integron. Sensitivity was assessed by testing mixtures of the three targets (intI integrase genes of each integron class) ranging from 10 to 10(8) copies. Specificity was determined with a panel of integron-containing and integron-free control strains. The method was then applied to clinical samples. The PCR method was specific and had a sensitivity of 10(2) copies for all three genes, regardless of their respective quantities. The method was quantitative from 10(3) to 10(7) copies, and was able to detect integrons directly in biological samples. We have developed a rapid, quantitative, specific and sensitive method that could prove useful for initial screening of Gram-negative isolates, or clinical samples, for likely multidrug resistance.

Acquisition of extended-spectrum β-lactamase producing Escherichia coli strains in male and female infants admitted to a neonatal intensive care unit: molecular epidemiology and analysis of risk factors

Extended-spectrum beta-lactamases (ESBLs) are bacterial enzymes that confer resistance to advanced generation cephalosporins and can lead to therapeutic failures. There has been no analysis of factors associated with the risk of acquisition of ESBLs in neonates in an intensive care unit from northern India. The CTX-M ESBL enzymes impart resistance against advanced generation cephalosporins (e.g. cefotaxime) and CTX-M variants have become the most prevalent ESBLs worldwide. The CTX-M-15 enzyme in particular is increasingly being reported from Escherichia coli isolates from northern India together with TEM-1. Moreover, E. coli is the most common cause of neonatal sepsis. Accordingly, this study aimed to: (i) characterize the mode of transmission of bla(CTX-M) and bla(TEM) among ESBL-producing E. coli strains isolated from patients admitted to a neonatal intensive care unit (NICU), and (ii) identify factors associated with the acquisition of the said strains in male and female neonates. A total of 97 ESBL-producers was identified among 266 E. coli strains isolated from 238 neonates. The isolates were screened for bla(CTX-M), bla(TEM), armA, rmtA and rmtB, the last three genes being responsible for aminoglycoside resistance. PCR amplified bla(CTX-M) genes were cloned and sequenced. Five bla(CTX-M-15), two rmtB, two bla(TEM-1) and thirteen class1 integrons were detected. All the bla(CTX-M-15) positive isolates, except one, were clonally related. Both univariate and multivariate analyses of factors for the acquisition of the said strains were performed with respect to the sex of the neonates. 'Length of stay in the NICU' was found to be the single independent factor associated with ESBL acquisition. In conclusion, our data suggest that male neonates who are colonized or infected by ESBL-producing E. coli have a longer stay in the NICU compared to their female counterparts. This prolonged stay may be due to male neonates becoming colonized/infected earlier than their female counterparts. Plasmid-mediated-conjugal transfer was found to be the mechanism of transfer of the bla(CTX-M-15) resistance marker in the described setting.

Molecular Characterisation of Trimethoprim Resistance in Escherichia coli and Klebsiella pneumoniae during a Two Year Intervention on Trimethoprim Use

BackgroundTrimethoprim resistance is increasing in Enterobacteriaceae. In 2004-2006 an intervention on trimethoprim use was conducted in Kronoberg County, Sweden, resulting in 85% reduction in trimethoprim prescriptions. We investigated the distribution of dihydrofolate reductase (dfr)-genes and integrons in Escherichia coli and Klebsiella pneumoniae and the effect of the intervention on this distribution.Methodology/Principal FindingsConsecutively isolated E. coli (n = 320) and K. pneumoniae (n = 54) isolates phenotypicaly resistant to trimethoprim were studied. All were investigated for the presence of dfrA1, dfrA5, dfrA7, dfrA8, dfrA12, dfrA14, dfrA17 and integrons class I and II. Isolates negative for the seven dfr-genes (n = 12) were also screened for dfr2d, dfrA3, dfrA9, dfrA10, dfrA24 and dfrA26. These genes accounted for 96% of trimethoprim resistance in E. coli and 69% in K. pneumoniae. The most prevalent was dfrA1 in both species. This was followed by dfrA17 in E. coli which was only found in one K. pneumoniae isolate. Class I and II Integrons were more common in E. coli (85%) than in K. pneumoniae (57%). The distribution of dfr-genes did not change during the course of the 2-year intervention.Conclusions/SignificanceThe differences observed between the studied species in terms of dfr-gene and integron prevalence indicated a low rate of dfr-gene transfer between these two species and highlighted the possible role of narrow host range plasmids in the spread of trimethoprim resistance. The stability of dfr-genes, despite large changes in the selective pressure, indirectly suggests a low fitness cost of dfr-gene carriage.

Occurrence and Characteristics of Class 1 and 2 Integrons in Clinical Bacterial Isolates from Patients in South China

Recent studies have shown that integrons play a major role in spreading antibiotic resistance genes in clinical settings, as antibiotic resistance genes are frequently found located at gene cassettes. Polymerase chain reaction (PCR) analyses were carried out for the detection of the integrase genes of the three classes of integrons, and their gene cassettes were characterized in 118 clinical strains, including both gram-positive and gram-negative bacteria, isolated from a hospital in Guangzhou, China during 2004. Class 1 and 2 integrons were detected in 76.3% (90/118) and 0.8% (1/118) of the tested clinical isolates, respectively. Moreover four isolates were positive for both the integrons and no class 3 was detected. Some of them were first reported, such as Enterococcus faecalis, Enterococcus faecium, Alcaligenes sp., and Flavobacterium sp. Seven different arrays of gene cassettes of class 1 integron were found, and a high prevalence of dfrA12-orfF-aadA2 genes was observed. In addition, we identified a new none-open reading frame (ORF) cassette in a class 1 integron positive clinical coagulase-negative Staphylococcus strain GH69. The none-ORF cassette, a 700 bp sequence containing a 441 bp ORF and a 59-base element, is first characterized in this study. All class 2 integrons carried an array of gene cassettes dfrA1-sat2-aadA1. Moreover bacteria contain more than one integrons were also found in this study. Resistance to trimethoprim-sulfamethoxazole was frequently found to be encoded within integrons. Therefore, it is important that guidelines for the prudent use of antimicrobial agents are adopted and surveillance programs are established.

Infected foot ulcers in male and female diabetic patients: a clinico-bioinformative study

BackgroundThe study aimed at (i) characterizing the mode of transmission of blaCTX-M and blaTEM-1 among extended-spectrum-β-lactamase (ESBL)-producing Escherichia coli strains isolated from infected diabetic foot ulcers, and (ii) identifying the risk factors for "sex-associated multidrug resistant Gram-negative bacterial (MDRGNB)-infection status" of the ulcers.MethodsSeventy-seven diabetic patients having clinically infected foot ulcers were studied in a consecutive series. The E. coli strains isolated from the ulcers were screened for blaCTX-M, blaTEM-1, armA, rmtA and rmtB during the 2-year study-period. PCR amplified blaCTX-M genes were cloned and sequenced. Enterobacterial repetitive intergenic consensus (ERIC)-PCR was used for the analysis of genetic relatedness of the ESBL-producers. Risk factors for "sex-associated MDRGNB-infection status" of ulcers were assessed. Modeling was performed using Swiss-Model-Server and verified by Procheck and verify3D programmes. Discovery Studio2.0 (Accelrys) was used to prepare Ramachandran plots. Z-scores were calculated using 'WHAT IF'-package. Docking of cefotaxime with modeled CTX-M-15 enzyme was performed using Hex5.1.ResultsAmong 51 E. coli isolates, 14 (27.5%) ESBL-producers were identified. Only 7 Class1 integrons, 2 blaCTX-M-15, and 1 blaTEM-1 were detected. Ceftazidime and cefotaxime resistance markers were present on the plasmidic DNA of both the blaCTX-M-15 positive strains and were transmissible through conjugation. The residues Asn132, Glu166, Pro167, Val172, Lys234 and Thr235 of CTX-M-15 were found to make important contacts with cefotaxime in the docked-complex. Multivariate analysis proved 'Glycemic control at discharge' as the single independent risk factor.ConclusionsMale diabetic patients with MDRGNB-infected foot ulcers have poor glycemic control and hence they might have higher mortality rates compared to their female counterparts. Plasmid-mediated conjugal transfer, albeit at a low frequency might be the possible mechanism of transfer of blaCTX-M-15 resistance marker in the present setting. Since the docking results proved that the amino acid residues Asn132, Glu166, Pro167, Val172, Lys234 and Thr235 of CTX-M-15 (enzyme) make important contacts with cefotaxime (drug) in the 'enzyme-drug complex', researchers are expected to duly utilize this information for designing more potent and versatile CTX-M-inhibitors.

Prevalence and Diversity of Integrons and Associated Resistance Genes inEscherichia coliIsolates from Poultry Meat in Tunisia

Fifty-five Escherichia coli isolates were acquired from chicken and turkey meat obtained from two slaughterhouses in Tunis. Eighty-nine percent, 80%, 78%, 67%, 45%, 27%, 7%, 4%, and 2% of these isolates showed resistance to tetracycline, trimethoprim/sulfamethoxazole, streptomycin, nalidixic acid, ampicillin, chloramphenicol, ciprofloxacin, colistine, and gentamicin, respectively. No resistance was detected to cefotaxime, ceftazidime, or amikacin. bla(TEM) gene was found in 22 of 25 ampicillin-resistant isolates, and 1 isolate harbored bla(OXA-1) gene. Tetracycline resistance was predominately mediated by the tetA gene. The sul1, sul2, and sul3 genes, alone or combined, were detected in 46 of 48 sulfonamide-resistant isolates, and sul1 and sul3 were included in class 1 integrons in some cases. Sixty percent of isolates harbored integrons (class 1, 30 isolates; class 2, 5 isolates). Class 2 integrons contained in all cases the dfrA1-sat1-aadA1-orfX gene cassette arrangement. Nine gene cassette arrangements have been detected among class 1 integrons, containing different alleles of dfrA (five alleles) and aadA (2 alleles) genes, which encode trimethoprim and streptomycin resistance, respectively. An uncommon gene cassette array (sat-psp-aadA2-cmlA1-aadA1-qacH-IS440-sul3) has been identified in three class 1 integron-positive isolates, and one additional isolate had this same structure with the insertion of IS26 inside the aadA1 gene (included in GenBank with accession no. FJ160769). The 55 studied isolates belong to the four phylogenic groups of E. coli, and phylogroups A and D were the most prevalent ones. At least one virulence-associated gene (fimA, papC, or aer) was detected in 44 of the 55 (80%) studied isolates. E. coli isolates of poultry origin could be a reservoir of antimicrobial-resistance genes and of integrons, and its evolution should be tracked in the future.

Integron Class 1 Reservoir among Highly Resistant Gram-Negative Microorganisms Recovered at a Dutch Teaching Hospital

Integrons play an important role in the dissemination of resistance genes among bacteria. Nearly 70% of highly resistant gram-negative bacteria isolated at a tertiary care hospital harbored an integron. Epidemiologic analysis suggests that horizontal gene transfer is an important mechanism of resistance spread and has a greater contribution than cross-transmission to levels of resistance in settings where highly resistant gram-negative bacteria are endemic.

Pathotype and Antibiotic Resistance Gene Distributions of Escherichia coli Isolates from Broiler Chickens Raised on Antimicrobial-Supplemented Diets

The impact of feed supplementation with bambermycin, monensin, narasin, virginiamycin, chlortetracycline, penicillin, salinomycin, and bacitracin on the distribution of Escherichia coli pathotypes in broiler chickens was investigated using an E. coli virulence DNA microarray. Among 256 E. coli isolates examined, 59 (23%) were classified as potentially extraintestinal pathogenic E. coli (ExPEC), while 197 (77%) were considered commensal. Except for chlortetracycline treatment, the pathotype distribution was not significantly different among treatments (P > 0.05). Within the 59 ExPEC isolates, 44 (75%) were determined to be potentially avian pathogenic E. coli (APEC), with the remaining 15 (25%) considered potentially "other" ExPEC isolates. The distribution within phylogenetic groups showed that 52 (88%) of the ExPEC isolates belonged to groups B2 and D, with the majority of APEC isolates classified as group D and most commensal isolates (170, 86%) as group A or B1. Indirect assessment of the presence of the virulence plasmid pAPEC-O2-ColV showed a strong association of the plasmid with APEC isolates. Among the 256 isolates, 224 (88%) possessed at least one antimicrobial resistance gene, with nearly half (107, 42%) showing multiple resistance genes. The majority of resistance genes were distributed among commensal isolates. Considering that the simultaneous detection of antimicrobial resistance tet(A), sulI, and bla(TEM) genes and the integron class I indicated a potential presence of the resistance pAPEC-O2-R plasmid, the results revealed that 35 (14%) of the isolates, all commensals, possessed this multigene resistance plasmid. The virulence plasmid was never found in combination with the antimicrobial resistance plasmid. The presence of the ColV plasmid or the combination of iss and tsh genes in the majority of APEC isolates supports the notion that when found together, the plasmid, iss, and tsh serve as good markers for APEC. These data indicate that different resistant E. coli pathotypes can be found in broiler chickens and that the distribution of such pathotypes and certain virulence determinants could be modulated by antimicrobial agent feed supplementation.

Persistence of Multiple Antibiotic Resistant Strains ofAcinetobacter baumanniiCarrying Class 1 Integron in a Hospital Setting

Forty-nine strains of multiresistant Aceinetobacter baumannii isolated from intensive care unit patients in Royal Brisbane and Women Hospital (RBWH) between 2001 and 2003 and four epidemiologically unrelated strains from three other hospitals were tested (n = 53) for their genetic relatedness using pulsed-field gel electrophoresis (PFGE) and for the presence of different classes of integrons. With PFGE, these strains were divided into three common (C) but closely related types (i.e., C1, C1a, and C1b) and eight single (S) types (S1-S8). C1 contained 40 isolates, while C1a and C1b contained 5 and 2 isolates, respectively. All isolates from Royal Brisbane and Women Hospital (RBWH) were resistant to 12 or more antibiotics. Four common pattern of antibiotic resistance (PAR) was observed among the isolates. The dominant PAR contained 39 strains from RBWH, isolated during 2000 (n = 6), 2001 (n = 16), and 2002 (n = 17) and were resistant to 14 antibiotics. Of these, 36 strains (92%) had identical PAR/PFGE types. Class 1 integrase genes were detected in all of the 53 isolates with 5 isolates also having class 2 integrase gene. No class 3 integrase gene was detected among the isolates. Our data suggest the presence of a dominant and persistent clone of multiresistant A. baumannii strain carrying class 1 integron in this hospital setting.