Preservation of integron types among Enterobacteriaceae producing extended-spectrum beta-lactamases in a Spanish hospital over a 15-year period (1988 to 2003)

In silico and biological activity evaluation of quercetin-boron hybrid compounds, anti-quorum sensing effect as alternative potential against microbial resistance

Boronic acid compounds and the natural flavonoid compound quercetin were handled to synthesize two novel ligands encoded as B1(2,2'-(1,4-phenylenebis (benzo [1,3,2] dioxaborole-2,5-diyl)) bis (3,5,7-trihydroxy-4H- chromen-4-one) and B2(3.3.6. 3,5,7-trihydroxy-2-(2-(6-methoxypyridin-3-yl)benzo[d][1,3,2]dioxaborol-5-yl)- 4 H-chromene-4). Antioxidant activities of ligands were investigated by DPPH, ABTS and CUPRAC methods. Cholinesterase inhibition effects of ligands were determined by acetylcholinesterase and butyrylcholinesterase enzyme inhibition methods, cytotoxic effects of ligands were applied to healthy breast and colon cancer cell lines by MTT method, and urease and tyrosinase enzyme activities were determined. Antimicrobial properties of the compounds were analyzed by detecting their anti-QS potentials on Chromobacterium violaceum biosensor strain. Both compounds were found to have significant antioxidant effects compared to controls. It was determined that the compound B1 at 1-10 µg/mL was more active than the reference compounds (α-TOC and BHT). Moreover, the enzyme activity studies on ligands demonstrated that acetylchoinesterase and butyrylcholinesterase enzyme inhibitions were higher than the reference compounds. As expected, boron derivatives exhibited respectable activity against the biofilms of Escherichia coli (E. coli) and P. aeruginosa (P. aeruginosa). These results demonstrate the potential applicability of boron derivatives in the treatment of biofilm-associated infections and provide a practical strategy for the design of new boron-based antimicrobial materials. In silico molecular docking studies were performed on ligands to identify newly synthesized compounds. The binding parameter values and binding sites of the compounds were also determined. In conclusion, our studies showed that newly synthesized hybrid compounds could be solutions for antimicrobial resistance and enzyme-related disorders.

Occurrence of emerging sulfonamide resistance (sul1 and sul2) associated with mobile integrons-integrase (intI1 and intI2) in riverine systems

Global use of antibiotics has exceedingly enhanced in agricultural, veterinary and prophylactic human use in recent days. Hence, these antibiotics can easily be found in the environment. This study revealed the occurrence of emerging MDR and ESBL producing strains, pollution profile, and factors integrons (intI1 and intI2) and environmental factors associated, in the riverine systems under different ecological and geo-climatic zones were investigated. The samples were collected based on anthropogenic intervention such as discharge of domestic wastes, industrial wastes, hospital, and municipal wastes. Among 160bacterial morphotypes, 121 (75.62%) exhibited MDR trait with maximum resistance towards lincosamide (CD = 71.3%), beta-lactams (P = 70.6%; AMX = 66.3%), cephalosporin (CZ = 60.6%; CXM = 34.4%), sulfonamide (COT = 50.6%; TR = 43.8%) followed by macrolide (E = 29.4%), tetracycline (TET = 18.8%), aminoglycosides (S = 18.8%; GEN = 6.3%), fluoroquinolones (NX = 18.1%; OF = 4.4%) and carbapenem (IPM = 5.0%). IntI1 gene was detected in 73 (60.3%) of isolates, whereas intI2 was found in 11 (9.09%) isolates. Eight (6.61%) isolates carried both integron genes (intI1 and intI2). sul1 and dfrA1 genes were detected in 53 (72.6%) and 63 (86.3%) isolates, respectively. A total of 103 (85.1%) were found ESBL positive with the presence of ESBL genes in 100 (97.08%) isolates. In riverine systems most prevalent ESBL gene blaTEM (93.0%) was detected alone as well as in combination with bla genes. The data can be utilized for public awareness and regulation of guidelines by local governing bodies as an alarming threat to look-out against the prevalent resistance in environment thereby assisting in risk management during epidemics. This study is a comprehensive investigation of emerging antibiotic pollutants and its resistance in bacteria associated with factors integrons-integrase responsible for its dissemination. It may also assist in global surveillance of antibiotic resistance and policies to curtail unnecessary antibiotic use.

Characterization of antibiotic resistance integrons harbored by Romanian Escherichia coli uropathogenic strains

Because little is known about the integrons which constitute an important means of spreading resistance in bacteria circulating in Romania, this study aimed to detect antibiotic resistance gene cassettes embedded in integrons in a convenient collection of 60 ciprofloxacin-resistant Escherichia coli isolates of various phylogroups, associated with community-acquired urinary tract infections. Characterization of the integrons was accomplished by PCR, restriction fragment length polymorphism typing, and DNA sequencing of each identified type. More than half of the tested E. coli strains were positive for integrons of class 1 (31 strains) or 2 (1 strain). These strains derived more frequently from phylogenetic groups A (15 of 21 strains), B1 (10 of 14 strains), and F (3 of 4 strains), respectively. While 20 strains carried class 1 integrons which could be assigned to nine types, eleven strains carried integrons that lacked the 3’-end conserved segment. The attempts made to characterize the gene cassettes located within the variable region of the various integrons identified in this study revealed the presence of genes encoding resistance to trimethoprim, aminoglycosides, beta-lactams or chloramphenicol. The evidence of transferable resistance determinants already established in the autochthonous E. coli strains highlights the need for improved control of resistance-carrying bacteria.

Extended-Spectrum β-Lactamases among Enterobacteriaceae Isolated from Urinary Tract Infections in Gaza Strip, Palestine

Background

Extended-spectrum β-lactamase-producing organisms causing urinary tract infections are increasing in incidence and pose a major impendence to health-care facility, having limited therapeutic options. This study aimed to assess the prevalence of ESBLs in Enterobacteriaceae isolates causing urinary tract infections in Gaza strip, Palestine, and to characterize β-lactamase types and associated resistance genes.

Methods

Eighty-five Enterobacteriaceae isolates were recovered from urinary tract infections within three months in Gaza Strip hospitals. The characterization of β-lactamase genes and the genetic environments of CTX-M, the identification of associated resistance genes, and the presence and characterization of integrons were tested by PCR and sequencing.

Results

The occurrence rate of ESBL among tested isolates was 30 (35.3%), and among ESBL-positive isolates, bla_CTX-M was the highest followed by bla_TEM. ESBL-CTX-M-1 group was confirmed in 93.3%, and the remaining carried CTX-M-9 group. CTX-M-15, CTX-M-3, CTX-M-1, CTX-M-14, CTX-M-27, and CTX-M-37 enzymes were demonstrated among the isolates with the majority (73%) being CTX-M-15. ISEcp-1 was demonstrated in 27 (90%, high incidence) of ESBL isolates. Class 1 integrons have been detected in higher rates (53.3%) in ESBL-positive isolates in comparison with non-ESBL isolates (6, 33.3%). Cassettes of integron-1 contain (aadA1, aadA2, aadA5, dfrA5, dfrA7, dfrA12, and dfrA17) genes. The aac(6′)-Ib-cr gene was demonstrated in 36.7% of ESBL-positive isolates.

Conclusions

This study indicates that bla_CTX-M-15 was the most prevalent β-lactamase in this region. Our study demonstrates for the first time in Palestine the identification of bla_CTX-M-15 in P. rettgeri and S. liquefaciens, also bla_CTX-M-37 in E. cloacae. The coexpression of multiple β-lactamase genes with aac(6′)-Ib-cr and qnr in the presence of ISEcp-1 and integrons in individual strains will increase the dissemination of highly resistant strains. ESBL producers were more resistant than non-ESBLs producers for almost all tested antibiotics.

Molecular characterization of class 1, 2 and 3 integrons in clinical multi-drug resistant Klebsiella pneumoniae isolates

Background

The aim of this study was to characterize class 1,2 and 3 integrons in clinical MDR Klebsiella pneumoniae isolates in Kashan, Iran.

Methods

One hundred-eighty one Klebsiella pneumoniae were recovered from clinical specimens during November 2013 to October 2014. Antimicrobial susceptibility patterns were determined by disk diffusion method according to the Clinical and Laboratory Standards Institute (CLSI) guidelines for detection of MDR strains. Of the 181 Klebsiella pneumoniae, 146 (80.7%) of isolates were isolated from nosocomial infected patients and 150 (82.9%) identified as MDR isolates. The PCR amplification was used to show presence of class 1, 2 and 3 integrons among MDR strains. The PCR method and sequencing were used for evaluation of cassette content of integrons.

Results

Of the MDR K. pneumoniae isolates, 150 (100%) and 55 (36.7%) carried intI1 and intI2 genes, respectively. None of the MDR Klebsiella pneumoniae isolates carried class 3 integrons. Amplification of conserved segment (CS) of class 1 and class 2 integrons revealed 10 different arrays including: No. cassette; dfrA5, dfrA30; aadA2; aadA2, dfrA12; dfrA17, aadA5, aadA4; dfrA5, dfrA30, aadA2; dfrA5, dfrA30, aadA2, dfrA12, dfrA5, dfrA30, dfrA17, aadA5, aadA4; aadA2, aadA2, dfrA12; dfrA5, dfrA30, aadA2, aadA2, dfrA12 and 4 arrays including: No. cassette; aadA1; dfrA1-sat1; aadA1, dfrA1-sat1, respectively.

Conclusions

The finding of present study revealed a high prevalence of integrons especially class 1 among MDR K. pneumoniae isolates from nosocomial infections in Kashan, which led to rapid extension of MDR strains.

Integrons in Enterobacteriaceae: diversity, distribution and epidemiology

Integrons are versatile gene acquisition systems that allow efficient capturing of exogenous genes and ensure their expression. Various classes of integrons possessing a wide variety of gene cassettes are ubiquitously distributed in enteric bacteria worldwide. The epidemiology of integrons associated multidrug resistance in Enterobacteriaceae is rapidly evolving. In the past two decades, the incidence of integrons in enteric bacteria has increased drastically with evolution of multiple gene cassettes, novel gene arrangements and complex chromosomal integrons such as Salmonella genomic islands. This review focuses on the distribution, versatility, spread and global trends of integrons among important members of the Enterobacteriaceae, including Escherichia coli, Klebsiella, Shigella and Salmonella, which are known to cause infections globally. Such a comprehensive understanding of integron-associated antibiotic resistance, their role in the spread of such resistance traits and their clinical relevance especially with regard to each genus individually is paramount to contain the global spread of antibiotic resistance.

Pharmacodynamics of Finafloxacin, Ciprofloxacin, and Levofloxacin in Serum and Urine against TEM- and SHV-Type Extended-Spectrum-β-Lactamase-Producing Enterobacteriaceae Isolates from Patients with Urinary Tract Infections

The pharmacodynamics of finafloxacin, ciprofloxacin, and levofloxacin against extended-spectrum-β-lactamase (ESBL)-producing Enterobacteriaceae isolates were compared. Since quinolones lose activity in acidic media, and particularly in urine, their activities were tested in parallel under conventional conditions and in acidic artificial urine. For this purpose, TEM- and SHV-type ESBL-producing Escherichia coli and Klebsiella pneumoniae strains and their wild-type counterparts were exposed in a modified Grasso model to simulated concentrations of drugs in serum and urine following oral doses of either finafloxacin at 800 mg once a day (q.d.), immediate-release ciprofloxacin at 500 mg twice a day (b.i.d.), extended-release ciprofloxacin at 1,000 mg q.d., or levofloxacin at 500 or 750 mg q.d. The concentrations of the drugs in urine were fitted by compartmental modeling. Bacteria were cultivated in Mueller-Hinton broth (MHB) at pH 7.2 or 5.8 or in artificial urine at pH 5.8. Bacteria were counted every 2 h until 10 h and at 24 h; the areas under the bacterial-count-versus-time curves were calculated. It was found that finafloxacin eliminated all strains within 2 h under all the conditions studied. At all doses studied, ciprofloxacin and levofloxacin were highly active against wild-type strains in MHB at pH 7.2 but lost activity in MHB, and particularly in urine, at pH 5.8. Viable counts of ESBL producers were reduced for 6 to 8 h by 3 log10 titers, but the bacteria regrew thereafter. Ciprofloxacin and levofloxacin were almost inactive against the SHV producer grown in artificial urine. We conclude that pharmacodynamic models using artificial urine may mirror the physiology of urinary tract infections more closely than those using conventional media. In contrast to ciprofloxacin and levofloxacin, finafloxacin gained activity in this model at an acidic pH, maintained activity in artificial urine, and was active against TEM and SHV producers.

Assessment of extended-spectrum β-lactamases and integrons among Enterobacteriaceae in device-associated infections: multicenter study in north of Iran

BACKGROUND

Device-associated nosocomial infections (DA-NIs), due to MDR Enterobacteriaceae, are a major threat to patient safety in ICUs. We investigated on Extended-spectrum β-lactamases (ESBL) producing Enterobacteriaceae and incidence of integrons in these bacteria isolated from ventilator-associated pneumonia (VAP) and catheter-associated urinary tract infections (CAUTIs) in 18 governmental hospitals in the north of Iran.

METHODS

In this cross-section study, the antibiotic susceptibility test was performed using the MIC method; also, phenotypically detection of ESBL-producing bacteria was carried out by the double-disk synergy (DDS) test. Presence of ESBL-related genes and integron Classes 1 and 2 was evaluated by the PCR method.

RESULTS

Out of a total of 205 patients with DA-NIs, Enterobacteriaceae were responsible for (72.68%) of infections. The most common DA-NIs caused by Enterobacteriaceae were VAP (77.18%), CAUTI (19.46%), and sepsis due to VAP (3.35%). The most frequently Enterobacteriaceae were; Klebsiella pneumoniae 75 (24; 32% ESBL positive), E. coli 69 (6; 8.69% ESBL positive) and Enterobacter spp. 5 (5; 100% ESBL positive). Distribution of ESBL-related genes was as follows: bla-SHV (94.3%), bla-CTX (48.6%), bla-VEB (22.9%) and bla-GES (17.14%). The incidence rate of integron class 1 and class 2 was (82.92%) and (2.9%) respectively. Eight types of ESBL-producing bacteria were observed.

CONCLUSIONS

Due to the fact that the emergence rate of ESBL Enterobacteriaceae is increasing in DA-NIs, co-incidence of different types of ESBL genes with integrons in 75-100% of strains in our study is alarming for clinicians and healthcare safety managers. Therefore, regional and local molecular level estimations of ESBLs that are agents of DA-NIs are critical for better management of empiric therapy, especially for patients in ICUs.

Association of antibiotic resistance with SHV-12 extended-spectrum β-lactamase in Enterobacter cloacae

The association between antibiotic resistance and SHV-12 extended-spectrum β-lactamase (ESBL) in Enterobacter cloacae remains unknown. The aim of the present study was to investigate the prevalence of both chromosome- and plasmid-borne SHV-12 ESBL genes in Enterobacter cloacae. Transmission of the SHV-12 ESBL gene was explored, and the risk factors for antibiotic resistance in E. cloacae were analyzed. Polymerase chain reaction (PCR) results showed that 58 out of the 100 isolates carried the SHV-12 ESBL gene: 34.48% of them occurred in the chromosome, 48.28% were plasmid-borne and 17.24% appeared in both. Enterobacterial repetitive intergenic consensus-PCR tests detected 82 chromosomal genotypes. Conjugation assays showed that 70.00% of plasmid-borne SHV-12 ESBL genes were successfully transconjugated into E. coli C600 and that the antibiotic resistance phenotype of E. cloacae was partially (84%) or completely (10%) transferred. A significantly higher SHV-12 ESBL detection rate was found in patients with underlying conditions and/or complications compared with those without (P<0.05). The detection of SHV-12 ESBL-producing E. cloacae from vertical transmission varied significantly across clinical departments and age groups (P<0.05), with the highest rates in the intensive care unit and the group of patients aged ≥60 years. The present results indicate that the location and transmission efficiency of SHV-12 ESBL are closely correlated with the antibiotic resistance of E. cloacae.

The dissemination mode of drug-resistant genes in Enterobacter cloacae

BACKGROUND

Enterobacter cloacae (E. cloacae) infection has the highest mortality rate among Enterobacter infections. This study aimed to determine the prevalence and the transmission route of the class I integron, qnr genes, and CTX-M ESBLs genes in clinical isolates and to analyse the association between the prevalence of MDR genes and the antibiotic resistance of E. cloacae.

MATERIALS AND METHODS

The antibiotic susceptibility was tested the agar dilution method. The class I integron, qnr genes, and CTX-M ESBLs genes were detected by polymerase chain reaction (PCR). The prevalence data were analysed with the Chi-square test.

RESULTS

In the 100 clinical isolates, the class I integron-positive rate was 65%, with 12% on chromosome, 15% on plasmids and 38% on both. The positive rate of qnr genes was 37% with plasmid location. The positive rates for qnrA, qnrB and qnrS were 6%, 23% and 8%, respectively. The CTX-M ESBLs-positive rate was 34%. For CTX-M-1 ESBLs, 15% were on chromosome, 6% on plasmids and 4% on both; for CTX-M-9 ESBLs, 1% was on chromosome and 7% on plasmid; for CTX-M-25 ESBLs, 3% were on chromosome and 1% on plasmid.

CONCLUSION

Antibiotic resistance genes may be horizontally and vertically disseminated among E. cloacae, which helps multidrug-resistant (MDR) strains of E. cloacae to be successful nosocomial agents.

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 characterization of multidrug-resistant Klebsiella pneumoniae isolates

Klebsiella pneumoniae is an important cause of healthcare-associated infections worldwide. Selective pressure, the extensive use of antibiotics, and the conjugational transmission of antibiotic resistance genes across bacterial species and genera facilitate the emergence of multidrug-resistant (MDR) K. pneumoniae. Here, we examined the occurrence, phenotypes and genetic features of MDR K. pneumoniae isolated from patients in intensive care units (ICUs) at the First Affiliated Hospital of Xiamen University in Xiamen, China, from January to December 2011. Thirty-eight MDR K. pneumoniae strains were collected. These MDR K. pneumoniae isolates possessed at least seven antibiotic resistance determinants, which contribute to the high-level resistance of these bacteria to aminoglycosides, macrolides, quinolones and β-lactams. Among these isolates, 24 strains were extended-spectrum β-lactamase (ESBL) producers, 2 strains were AmpC producers, and 12 strains were both ESBL and AmpC producers. The 38 MDR isolates also contained class I (28/38) and class II integrons (10/38). All 28 class I-positive isolates contained aacC1, aacC4, orfX, orfX' and aadA1 genes. β-lactam resistance was conferred through bla SHV (22/38), bla TEM (10/38), and bla CTX-M (7/38). The highly conserved bla KPC-2 (37/38) and bla OXA-23(1/38) alleles were responsible for carbapenem resistance, and a gyrAsite mutation (27/38) and the plasmid-mediated qnrB gene (13/38) were responsible for quinolone resistance. Repetitive-sequence-based PCR (REP-PCR) fingerprinting of these MDR strains revealed the presence of five groups and sixteen patterns. The MDR strains from unrelated groups showed different drug resistance patterns; however, some homologous strains also showed different drug resistance profiles. Therefore, REP-PCR-based analyses can provide information to evaluate the epidemic status of nosocomial infection caused by MDR K. pneumoniae; however, this test lacks the power to discriminate some isolates. Thus, we propose that both genotyping and REP-PCR typing should be used to distinguish genetic groups beyond the species level.

Integron, Plasmid and Host Strain Characteristics of Escherichia coli from Humans and Food Included in the Norwegian Antimicrobial Resistance Monitoring Programs

Antimicrobial resistant Escherichia coli (n=331) isolates from humans with bloodstream infections were investigated for the presence of class 1 and class 2 integrons. The integron cassettes arrays were characterized and the findings were compared with data from similar investigations on resistant E. coli from meat and meat products (n=241) produced during the same time period. All isolates were obtained from the Norwegian monitoring programs for antimicrobial resistance in human pathogens and in the veterinary sector. Methods used included PCR, sequencing, conjugation experiments, plasmid replicon typing and subtyping, pulsed-field-gel-electrophoresis and serotyping. Integrons of class 1 and 2 occurred significantly more frequently among human isolates; 45.4% (95% CI: 39.9-50.9) than among isolates from meat; 18% (95% CI: 13.2 -23.3), (p<0.01, Chi-square test). Identical cassette arrays including dfrA1-aadA1, aadA1, dfrA12-orfF-aadA2, oxa-30-aadA1 (class 1 integrons) and dfrA1-sat1-aadA1 (class 2 integrons) were detected from both humans and meat. However, the most prevalent cassette array in human isolates, dfrA17-aadA5, did not occur in isolates from meat, suggesting a possible linkage between this class 1 integron and a subpopulation of E. coli adapted to a human host. The drfA1-aadA1 and aadA1 class 1 integrons were found frequently in both human and meat isolates. These isolates were subjected to further studies to investigate similarities with regard to transferability, plasmid and host strain characteristics. We detected incF plasmids with pMLST profile F24:A-:B1 carrying drfA1-aadA1 integrons in isolates from pork and in a more distantly related E. coli strain from a human with septicaemia. Furthermore, we showed that most of the class 1 integrons with aadA1 were located on incF plasmids with pMLST profile F51:A-:B10 in human isolates. The plasmid was present in unrelated as well as closely related host strains, demonstrating that dissemination of this integron also could be attributed to clonal spread. In conclusion, among the systematically collected isolates from two different sources, some significant differences concerning integron prevalence and integron variants were observed. However, closely related plasmids as vehicles for specific class 1 integrons in isolates from meat and from a human with bloodstream infection were found. The occurrence of similar multi-resistance plasmids in bacteria from a food source and from a human clinical sample highlights the possible role of meat as a source of resistance elements for pathogenic bacteria.

High Prevalence of Class 1 to 3 Integrons Among Multidrug-Resistant Diarrheagenic Escherichia coli in Southwest of Iran

OBJECTIVES

Horizontal transfer of integrons is one of the important factors that can contribute to the occurrence of multidrug-resistant (MDR) bacteria. This study aimed to determine the prevalence of integrons among MDR Escherichia coli strains isolated from stool specimens and investigate the associations between the existence of integrons and MDR properties in the southwest of Iran.

METHODS

There were 164 E. coli strains isolated from January 2012 to June 2012. Fecal specimens identified as E. coli by the conventional methods. Subsequently the antibiotic resistance was assessed using Clinical and Laboratory Standard Institute criteria. The presence of class 1-3 integrons and embedded gene cassettes was verified using specific primers by multiplex polymerase chain reaction assay.

RESULTS

Among a total of 164 studied samples, 69 (42.07%) isolates were multidrug resistant. Class 1 and class 2 integrons were present in 78.26% and 76.81% MDR isolates, respectively. For the first time in Iran, class 3 integron was observed in 26.09% MDR isolates. Significant correlations were identified between: class 1 integron and resistance to amikacin, gentamicin, chloramphenicol, ampicillin, tetracycline, nalidixic acid, and co-trimoxazole; class 2 integron and resistance to aminoglycosides, co-trimoxazole, cefalexin, ampicillin, and chloramphenicol; and class 3 integron and resistance to gentamicin, kanamycin, and streptomycin.

CONCLUSION

Our results indicate that integrons are common among MDR isolates and they can be used as a marker for the identification of MDR isolates. Therefore, due to the possibility of a widespread outbreak of MDR isolates, molecular surveillance and sequencing of the integrons in other parts of the country is recommended.

Correlation of Multi-drug Resistance, Integron and blaESBL Gene Carriage With Genetic Fingerprints of Extended-Spectrum β-Lactamase Producing Klebsiella pneumoniae

Background:

Some genetic and phenotypic variables are associated among distinct microbial populations.

Objectives:

The associations between multi-drug resistance (MDR) phenotypes, prevalence of antibiotic resistance integrons (ARIs), bla_SHV, bla_TEM and bla_CTX-M gene carriage and genetic fingerprints of random amplified polymorphic DNA (RAPD), confirmed by pulsed field gel electrophoresis (PFGE), were investigated among extended-spectrum β-lactamases (ESBL)-producing nosocomial isolates of Klebsiella pneumoniae.

Materials and Methods:

Susceptibility of 35 ESBL-producing K. pneumoniae nosocomial isolates to 22 antimicrobial agents was determined. Integron carriage was detected using specific primers for intI1, intI2 and intI3 genes by PCR.

Results:

All isolates were resistant to piperacillin and susceptible to imipenem. MDR phenotype was observed in 91.4% of the isolates. Class 1 integrons were detected in 21 (60%) and class 2 integrons in 3 (8.57%) of the isolates. Two of the isolates carried both classes and none harbored class 3 integrons. Significant correlations were observed between resistance to aminoglycosides, fluoroquinolones and sulfonamides, and between genotype groups with carriage of ARIs, MDR phenotype and bla_SHV gene carriage. ARI carriage was also significantly associated with MDR phenotype.

Conclusions:

Our findings suggest the possible co-carriage of some bla_SHV genes and ARIs on the same plasmids harboring the MDR genes. Possible role of integrons in dissemination of ESBL-encoding bla_SHV genes among ESBL-producing K. pneumoniae nosocomial isolates may be inferred.

Class 1 integrons in urinary isolates of extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae in Southern China during the past five years

We analyzed extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (226) and Klebsiella pneumoniae (53) collected from urine specimens during 2005-2009 for the presence of ESBL genes, class 1 integrons, and characterization of gene cassettes. TEM and CTX-M β-lactamase genes were the most prevalent. One hundred and forty-four E. coli and 35 K. pneumoniae were positive for the class 1 integrase gene; among them, 99 E. coli and 14 K. pneumoniae detected gene cassettes. Gene cassette regions were identified by restriction fragment length polymorphism and DNA sequencing analysis. Eleven distinct gene cassette arrays were found in E. coli isolates, and seven distinct gene cassette arrays were found in K. pneumoniae isolates. The cassette array aacA4-catB8-aadA1 was first found in E. coli and dfrA1-orfC was first reported in K. pneumoniae. Most of the gene cassettes found in this class 1 integrons were for aminoglycoside resistance. Enterobacterial repetitive intergenic consensus-polymerase chain reaction fingerprint patterns revealed the isolates carrying gene cassettes were genetically unrelated. In conclusion, we studied the class 1 integrons among urinary isolates of ESBL-producing E. coli and K. pneumoniae in Southern China during the past 5 years and found that class 1 integrons were widely disseminated and played a major role in antibiotic resistance.

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.

Prevalence and characterization of multidrug-resistant and extended-spectrum beta-lactamase-producing Escherichia coli from pediatric wards of a Malaysian hospital

The emergence of Escherichia coli resistant to extended-spectrum cephalosporins (ESCs) is of concern as ESC is often used to treat infections by Gram-negative bacteria. One-hundred and ten E. coli strains isolated in 2009-2010 from children warded in a Malaysian tertiary hospital were analyzed for their antibiograms, carriage of extended-spectrum beta-lactamase (ESBL) and AmpC genes, possible inclusion of the beta-lactamase genes on an integron platform, and their genetic relatedness. All E. coli strains were sensitive to carbapenems. About 46% of strains were multidrug resistant (MDR; i.e., resistant to ≥3 antibiotic classes) and almost half (45%) were nonsusceptible to ESCs. Among the MDR strains, high resistance rates were observed for ampicillin (98%), tetracycline (75%), and trimethoprim/sulfamethoxazole (73%). Out of 110 strains, bla(TEM-1) (49.1%), bla(CTX-M) (11.8%), and bla(CMY-2) (6.4%) were detected. Twenty-one strains were ESBL producers. CTX-M-15 was the predominant CTX-M variant found and this is the first report of a CTX-M-27-producing E. coli strain from Malaysia. Majority (3.1%) of the strains harbored class 1 integron-encoded integrases with a predominance of aadA and dfr genes within the integron variable region. No gene cassette encoding ESBL genes was found and integrons were not significantly associated with ESBL or non-ESBL producers. Possible clonal expansion was observed for few CTX-M-15-positive strains but the O25-ST131 E. coli clone known to harbor CTX-M-15 was not detected while CMY-2-positive strains were genetically diverse.

Virulence properties and integron-associated antibiotic resistance of Klebsiella mobilis strains isolated from clinical specimens

This study examined Klebsiella mobilis isolates cultured from clinical specimens for virulence-associated properties and antibiotic resistance. The strains produced a number of siderophores, including enterobactin, aerobactin and yersiniabactin. All isolates were able to adhere to and invade epithelial cells. They had cytotoxic activity, which caused destruction of human laryngeal epithelial HEp-2 cells and evoked lysis of murine macrophage J774 cells. Analyses of HEp-2 and J774 cellular morphology and DNA fragmentation in the cells showed features typical of cells undergoing apoptosis. Some K. mobilis strains harboured class 1 integrons carrying the aadA1 gene encoding an aminoglycoside adenyltransferase.

Association of composite IS26-sul3 elements with highly transmissible IncI1 plasmids in extended-spectrum-beta-lactamase-producing Escherichia coli clones from humans

The association of an IS440-sul3 platform with Tn21 class 1 integrons carried by IncI1 plasmids encoding extended-spectrum β-lactamases (ESBLs; mainly SHV-12 and CTX-M-14) among worldwide Escherichia coli clones of phylogroups A (ST10, ST23, and ST46), B1 (ST155, ST351, and ST359), and D/B2 (ST131) is reported. An in silico comparative analysis of sul3 elements available in the GenBank database shows the evolution of sul3 platforms by hosting different transposable elements facilitating the potential genesis of IS26 composite transposons and further insertion element-mediated promoted arrangements.

Observation on integron carriage among clinical isolates of Klebsiella pneumoniae producing extended-spectrum beta-lactamases

PURPOSE

Klebsiella pneumoniae is considered an important pathogen causing nosocomial and community-acquired infections and is often associated with the production of extended-spectrum beta-lactamases (ESBL) belonging to SHV and CTX-M families, which are frequently described as a part of complex integrons, facilitate their horizontal transfer to other related as well as unrelated microbes. The present study was undertaken to investigate the occurrence and characterization of integrons among K pneumoniae isolates producing ESBL in a tertiary referral hospital.

MATERIALS AND METHODS

A total of 136 clinical isolates of K pneumoniae were investigated for the presence of ESBL. Their ESBL genes were characterized by multiplex polymerase chain reaction (PCR). Integrase gene PCR was performed to detect the presence of integron. The isolates were further typed by random amplification of polymorphic DNA (RAPD).

RESULT

Out of 136 K pneumoniae isolates, 63 (46%) were confirmed to be ESBL producers. SHV (68%) and CTX-M (67%) ESBL genes were the most common in our study. Of the 63 ESBL-positive isolates, 58 (92%) strains carried integrons; 52 strains (82%) carried only class 1 integron, whereas 6 (9%) isolates harboured both class 2 integrons and the class 1 gene. However, in ESBL negatives, only 29 (40%) strains were positive for class 1 integron and none for class 2 integron.

CONCLUSION

The presence of class 2 integron amongst ESBL-producing K pneumoniae is being described for the first time in this part of the world. The findings of this study strongly suggest that integrons have a role in the dissemination of ESBL-mediated resistance among the nosocomial isolates of K pneumonia.

[Extended-spectrum beta-lactamases in enterobacteria other than Escherichia coli and Klebsiella]

Methods for detecting ESBL-producing Enterobacteriaceae begin by a correct interpretation of the susceptibility profiles, applying the usual criteria for interpretative reading of the antibiogram. Appropriate confirmatory methods will be consequently chosen, based on the inhibition of the enzyme by betalactamases inhibitors, generally clavulanic acid. In case of non-AmpC-producing Enterobacteriaceae, at least two substrates should be used -cefotaxime or ceftriaxone and ceftazidime- to detect enzymes with a low hydrolytic activity against both substrates. Cefepime or AmpC-inhibitors should be recommended for AmpC-producing microorganisms. The identification of the enzymes responsible for the confirmed ESBL phenotype can be performed, either in the clinical laboratory or in reference centres, following a protocol of biochemical and molecular reactions able to detect and characterize, at least, those genes more frequently related to the predominant phenotypic profiles in our region. It is important to know which are the most prevalent combinations enzyme-microorganism, the vehicles for the genetic transmission involved in their dissemination, and the main epidemiological characteristics of the infections that they produce, in order to establish the dimensions of the problem and conduct surveillance studies, with the aim of achieving measures to control the wide spread.

The profile of antibiotics resistance and integrons of extended-spectrum beta-lactamase producing thermotolerant coliforms isolated from the Yangtze River basin in Chongqing

The spreading of extended-spectrum beta-lactamases (ESBL)-producing thermotolerant coliforms (TC) in the water environment is a threat to human health but little is known about ESBL-producing TCs in the Yangtze River. We received 319 ESBL-producing stains obtained from the Chongqing basin and we investigated antibiotic susceptibility, bla gene types and the presence of integrons and gene cassettes. 16.8% of TC isolates were ESBL-producing bacteria and bla(TEM+CTx-M) was the predominant ESBL type. 65.2% of isolates contained class 1 integrons, but only 3 carried intI 2. Gene cassettes were amplified and sequenced. aadA, drfA, cmlA, sat1, aar3 and two ORF cassettes were found. In conclusion, Yangtze River is heavily polluted by ESBL-producing TC bacteria and the combined bla gene type could enhance antibiotic resistance. Class 1 integrons were widespread in ESBL-producing isolates and play an important role in multi-drug resistance. Characterization of gene cassettes could reveal the dissemination of antibiotic resistance genes.

The occurrence of antimicrobial resistance and class 1 integrons among commensal Escherichia coli isolates from infants and elderly persons

Background

The aim of our study was to compare the presence of the intI1 gene and its associations with the antibiotic resistance of commensal Escherichia coli strains in children with/without previous antibiotic treatments and elderly hospitalized/healthy individuals.

Methods

One-hundred-and-fifteen intestinal E. coli strains were analyzed: 30 strains from 10 antibiotic-naive infants; 27 from 9 antibiotic-treated outpatient infants; 30 from 9 healthy elderly volunteers; and 28 from 9 hospitalized elderly patients. The MIC values of ampicillin, cefuroxime, cefotaxime, gentamicin, ciprofloxacin, and sulfamethoxazole were measured by E-test and IntI1 was detected by PCR.

Results

Out of the 115 strains, 56 (49%) carried class 1 integron genes. Comparing persons without medical interventions, we found in antibiotic-naive children a significantly higher frequency of integron-bearing strains and MIC values than in healthy elderly persons (53% versus 17%; p < 0.01). Evaluating medical interventions, we found a higher resistance and frequency of integrons in strains from hospitalized elderly persons compared with non-hospitalized ones. Children treated with antibiotics had strains with higher MIC values (when compared with antibiotic-naive ones), but the integron-bearing in strains was similar. In most cases, the differences in resistance between the groups (integron-positive and negative strains separately) were higher than the differences between integron-positive and negative strains within the groups.

Conclusion

The prevalence of integrons in commensal E. coli strains in persons without previous medical intervention depended on age. The resistance of integron-carrying and non-carrying strains is more dependent on influencing factors (hospitalization and antibiotic administration) in particular groups than merely the presence or absence of integrons.

International spread and persistence of TEM-24 is caused by the confluence of highly penetrating enterobacteriaceae clones and an IncA/C2 plasmid containing Tn1696::Tn1 and IS5075-Tn21

TEM-24 remains one of the most widespread TEM-type extended-spectrum beta-lactamases (ESBLs) among Enterobacteriaceae. To analyze the reasons influencing its spread and persistence, a multilevel population genetics study was carried out on 28 representative TEM-24 producers from Belgium, France, Portugal, and Spain (13 Enterobacter aerogenes isolates, 6 Escherichia coli isolates, 6 Klebsiella pneumoniae isolates, 2 Proteus mirabilis isolates, and 1 Klebsiella oxytoca isolate, from 1998 to 2004). Clonal relatedness (XbaI pulsed-field gel electrophoresis [PFGE] and E. coli phylogroups) and antibiotic susceptibility were determined by standard procedures. Plasmid analysis included determination of the incompatibility group (by PCR, hybridization, and/or sequencing) and comparison of restriction fragment length polymorphism (RFLP) patterns. Characterization of genetic elements conferring antibiotic resistance included integrons (classes 1, 2, and 3) and transposons (Tn3, Tn21, and Tn402). Similar PFGE patterns were identified among E. aerogenes, K. pneumoniae, and P. mirabilis isolates, while E. coli strains were diverse (phylogenetic groups A, B2, and D). Highly related 180-kb IncA/C2 plasmids conferring resistance to kanamycin, tobramycin, chloramphenicol, trimethoprim, and sulfonamides were identified. Each plasmid contained defective In0-Tn402 (dfrA1-aadA1, aacA4, or aacA4-aacC1-orfE-aadA2-cmlA1) and In4-Tn402 (aacA4 or dfrA1-aadA1) variants. These integrons were located within Tn21, Tn1696, or hybrids of these transposons, with IS5075 interrupting their IRtnp and IRmer. In all cases, blaTEM-24 was part of an IS5075-DeltaTn1 transposon within tnp1696, mimicking other genetic elements containing blaTEM-2 and blaTEM-3 variants. The international dissemination of TEM-24 is fuelled by an IncA/C2 plasmid acquired by different enterobacterial clones which seem to evolve by gaining diverse genetic elements. This work highlights the risks of a confluence between highly penetrating clones and highly promiscuous plasmids in the spread of antibiotic resistance, and it contributes to the elucidation of the origin and evolution of TEM-2 ESBL derivatives.

Gene cassettes and cassette arrays in mobile resistance integrons

Gene cassettes are small mobile elements, consisting of little more than a single gene and recombination site, which are captured by larger elements called integrons. Several cassettes may be inserted into the same integron forming a tandem array. The discovery of integrons in the chromosome of many species has led to the identification of thousands of gene cassettes, mostly of unknown function, while integrons associated with transposons and plasmids carry mainly antibiotic resistance genes and constitute an important means of spreading resistance. An updated compilation of gene cassettes found in sequences of such 'mobile resistance integrons' in GenBank was facilitated by a specially developed automated annotation system. At least 130 different (<98% identical) cassettes that carry known or predicted antibiotic resistance genes were identified, along with many cassettes of unknown function. We list exemplar GenBank accession numbers for each and address some nomenclature issues. Various modifications to cassettes, some of which may be useful in tracking cassette epidemiology, are also described. Despite potential biases in the GenBank dataset, preliminary analysis of cassette distribution suggests interesting differences between cassettes and may provide useful information to direct more systematic studies.

Genetic characterisation of CTX-M-15-producing Klebsiella pneumoniae and Escherichia coli strains isolated from stem cell transplant patients in Tunisia

Characterisation of extended-spectrum beta-lactamase (ESBL) genes and their genetic environments as well as the presence of integrons were analysed in nine Klebsiella pneumoniae and two Escherichia coli ESBL-positive isolates recovered in the Centre of Bone Marrow Transplantation of Tunisia. All strains harboured the bla(CTX-M-15) gene and presented minimum inhibitory concentrations for cefotaxime and ceftazidime of 256-1024 mg L(-1) and 16-512 mg L(-1), respectively, and eight of them showed different pulsed-field gel electrophoresis patterns. The bla(OXA-1) and bla(TEM-1) genes were detected in eight and ten strains, respectively. In addition, bla(SHV-1), bla(SHV-11) and bla(SHV-27) were found in six, one and one K. pneumoniae strains, respectively. The new variant bla(SHV-103) was characterised in one K. pneumoniae strain. The intI1 gene was detected in eight K. pneumoniae strains and the dfrA5+ereA2 and aadA gene cassettes were found in one and five strains, respectively. All strains harboured a 70 kb plasmid, and its transference in addition to bla(CTX-M-15), bla(TEM-1b) and bla(OXA-1) genes was demonstrated from three K. pneumoniae to E. coli. ISEcp1 and orf477 were located upstream and downstream, respectively, of the bla(CTX-M-15) gene in 10 strains. The occurrence of the bla(CTX-M-15) gene in unrelated strains might have originated from the dissemination of mobile genetic elements in which ISEcp1 may have played an important role.

Prevalence and spread of extended-spectrum beta-lactamase-producing Enterobacteriaceae in Europe

Extended-spectrum beta-lactamases (ESBLs) represent a major threat among resistant bacterial isolates. The first types described were derivatives of the TEM-1, TEM-2 and SHV-1 enzymes during the 1980s in Europe, mainly in Klebsiella pneumoniae associated with nosocomial outbreaks. Nowadays, they are mostly found among Escherichia coli isolates in community-acquired infections, with an increasing occurrence of CTX-M enzymes. The prevalence of ESBLs in Europe is higher than in the USA but lower than in Asia and South America. However, important differences among European countries have been observed. Spread of mobile genetic elements, mainly epidemic plasmids, and the dispersion of specific clones have been responsible for the increase in ESBL-producing isolates, such as those with TEM-4, TEM-24, TEM-52, SHV-12, CTX-M-9, CTX-M-14, CTX-M-3, CTX-M-15 and CTX-M-32 enzymes.