Integron content of extended-spectrum-beta-lactamase-producing Escherichia coli strains over 12 years in a single hospital in Madrid, Spain

Carrier flies of multidrug-resistant Escherichia coli as potential dissemination agent in dairy farm environment

The life cycle of synanthropic flies and their behavior, allows them to serve as mechanical vectors of several pathogens. Given that flies can carry multidrug-resistant (MDR) bacteria, this study aimed to investigate the spread of genes of antimicrobial resistance in Escherichia coli isolated from flies collected in two dairy farms in Brazil. Besides antimicrobial resistance determinants, the presence of virulence genes related to bovine colibacillosis was also assessed. Of 94 flies collected, Musca domestica was the most frequently found in the two farms. We isolated 198 E. coli strains (farm A=135 and farm B=63), and >30% were MDR E. coli. We found an association between bla_TEM and phenotypical resistance to ampicillin, or chloramphenicol, or tetracycline; and bla_CTX-M and resistance to cefoperazone. A high frequency (86%) of phylogenetic group B1 among MDR strains and the lack of association between multidrug resistance and virulence factors suggest that antimicrobial resistance possibly is associated with the commensal bacteria. Clonal relatedness of MDR E. coli performed by Pulsed-Field Gel Electrophoresis showed wide genomic diversity. Different flies can carry clones, but with distinct antimicrobial resistance pattern. Sanger sequencing showed that the same class 1 integron arrangement is displayed by apparently unrelated strains, carried by different flies. Our conjugation results indicate class 1 integron transfer associated with tetracycline resistance. We report for the first time, in Brazil, that MDR E. coli is carried by flies in the milking environment. Therefore, flies can act as carriers for MDR strains and contribute to dissemination routes of antimicrobial resistance.

Detection of Antimicrobial Susceptibility and Integrons Among Extended-spectrum β-lactamase Producing Uropathogenic Escherichia coli Isolates in Southwestern Iran

Objectives

Urinary tract infections (UTIs) are one of the most prevalent infectious diseases and can lead to a high rate of morbidity and mortality. The emergence of multiple-drug resistant strains, particularly extended-spectrum beta-lactamases (ESBLs) producing strains, has become a global healthcare concern. Our study sought to investigate the antimicrobial resistance pattern and presence of integrons and fimH determinants among uropathogenic Escherichia coli (UPEC) isolates obtained from hospitalized Iranian patients.

Methods

This cross-sectional study was performed on 121 E. coli isolates recovered from patients with clinical symptoms of UTIs, referred to Shiraz Nemazee Hospital, in 2016-17. The isolates were identified by standard microbiologic tests and confirmed by API 20E strip. Antimicrobial susceptibility testing was determined using the disk diffusion method. The presence of fimH and classes 1-3 integron encoding genes was determined using the polymerase chain reaction.

Results

Ampicillin (9.1%) and nalidixic acid (19.0%) showed the lowest level of antibiotic susceptibility. The highest level of susceptibility was toward imipenem (77.7%). The rate of ESBL-producing isolates was 42.1%. There was a significant association between production of ESBLs and higher antibiotic resistance in the tested isolates. Of the investigated virulence and resistance genes, fimH, intI1, and intI2 were positive in 98.3%, 59.5%, and 7.4% of isolates, respectively.

Conclusions

The remarkable rate of ESBL-producing UPEC isolates accompanied with the presence of integrons suggest the necessity of restricted infection control policies to prevent further dissemination of resistant strains.

Expanded spectrum β-lactamase producing Escherichia coli isolated from chickens with colibacillosis in Egypt

Throughout the world, expanded spectrum β-lactamases (ESBL) are increasing among clinical isolates of Enterobacteriaceae, both in humans and animals. Unfortunately, there is a paucity of data on ESBL or Ampicillin class C β-lactamase (AmpC) in Egypt, although antimicrobial consumption is high in this developing country. This study aims to characterize the resistance mechanisms to expanded spectrum cephalosporins among resistant veterinary Escherichia coli isolates in Egypt. We investigated 50 clinical multi-resistant E. coli strains isolated from 20 chicken farms for production of ESBL or AmpC. Antibiotic susceptibility was tested by Clinical and Laboratory Standards Institute (CLSI) disk diffusion and ESBL confirmatory tests. PCR and sequencing were performed to screen for plasmid mediated ESBL genes and genes encoding AmpC β-lactamases. All the isolates were phylogentically classified, investigated for harboring class 1 integrons, and genotyped by amplified fragment length polymorphism (AFLP). Three strains showed ESBL and 6 strains AmpC phenotypic patterns, respectively, with confirmed ESBL genes of blaTEM-57, blaSHV-12, blaCTX-M-14, and blaCMY-2 for AmpC producing strains. All ESBL strains belonged to phylogroup D with different clones isolated from different flocks, while most of the AmpC strains belonged to phylogroup B1 (4/6) and were assigned to the same genotype distributed in 2 different farms. Class 1 integrons were disseminated in 60% of all tested strains and in 100% of ESBL and AmpC strains. These results highlight the antimicrobial resistance problem in Egypt, caused in all probability by unwise use of antimicrobials in animal husbandry. The results call for a nationwide surveillance program to monitor antimicrobial resistance.

Genomic Identity of Fluoroquinolone-Resistant blaCTX-M-15-Type ESBL and pMAmpC β-Lactamase Producing Klebsiella pneumoniae from Buffalo Milk, India

We investigated the occurrence of extended-spectrum β-lactamase (ESBL) and AmpC-type β-lactamase (ACBL) producing quinolone-resistant Klebsiella pneumoniae (KP) in milk samples of apparently healthy buffaloes (n = 348) and buffaloes (n = 19) with evidence of subclinical mastitis from seven districts of West Bengal, India. In total, 12 ESBL producing KP were isolated with blaCTX-M-15 gene and 7 of them were ACBL producers, as well. The blaCTX-M-15 genes were carried by transposable element ISEcp1. The plasmid-mediated quinolone resistance genes-qnrS, qnrA, qnrB, qepA, and aac(6')-Ib-cr were detected in five, one, three, four, and one isolate (s), respectively. In addition, eight isolates carried mutation in gyrase (gyrA) and six in topoisomerase IV (parC). Resistance markers/genes for sulfonamide (sul1), tetracycline [tet(A) and tet(B)], and aminoglycoside (aacC2) were also detected in eight, four, and one isolate(s), respectively. The class I integrons identified in five isolates carried aad2/aad5 and dfrA12/dfrA17 gene cassettes. The enterobacterial repetitive intergenic consensus-PCR revealed that all the isolates were genetically diverse and comprised a heterogeneous population. Isolation of multidrug-resistant KP, a typical nosocomial pathogen from buffalo milk, reiterates the need to monitor farm animals for ESBL producing Enterobacteriaceae and emphasizes on judicious use of antibiotics in animal husbandry sector.

Investigation of Class I, II, and III Integrons Among Acinetobacter Baumannii Isolates from Hospitalized Patients in Isfahan, Iran

Objectives

This study aimed to determine the prevalence of class I, II, and III integrons among clinical Acinetobacter baumannii isolates collected from hospitalized patients.

Methods

This cross-sectional study was conducted at two teaching hospitals in Isfahan, Iran, from October 2015 to October 2016. A total of 147 non-duplicate A. baumannii isolates were collected from clinical specimens and identified as A. baumannii using standard microbiological methods and confirmed by genotyping. Antimicrobial susceptibility was determined using disc diffusion method, and the presence of integron genes was performed using the polymerase chain reaction.

Results

Out of 147 confirmed A. baumannii isolates, 97.3% of isolates were extensive drug-resistant (XDR) and 2.7% were multidrug-resistant (MDR). Class I and II integrons were detected in 63.9% and 78.2% of the A. baumannii, respectively. Class III integron was not detected in any of the isolates.

Conclusion

Our results show a high prevalence of classes I and II integrons which may play a key role in the acquisition of MDR and XDR phenotype among A. baumannii isolates in our region. Therefore, use of appropriate infection control in clinical settings and implementation of treatment strategies is necessary for our hospitals.

Extended Spectrum Beta-Lactamase (ESBL)-producing bacteria isolated from hospital wastewaters, rivers and aquaculture sources in Nigeria

Untreated wastewater is a risk factor for the spread of antibiotic resistance in the environment. However, little is known about the contribution of untreated wastewater to the burden of antibiotic resistance in the Nigerian environment. In this study, a total of 143 ceftazidime-/cefpodoxime-resistant bacteria isolated from untreated wastewater and untreated wastewater-contaminated surface and groundwater in Nigeria were screened for extended-spectrum β-lactamase (ESBL) genes, integrons and integron gene cassettes by PCR. The genetic environment of bla _CTX-M-15 was mapped by PCR and potentially conjugative plasmids were detected among the isolates by degenerate primer MOB typing (DPMT). ESBL production was confirmed in 114 (79.7%) isolates and ESBL genes (bla _SHV, bla _CTX-M-15 and bla _TEM) were detected in 85 (74.6%) ESBL-producing isolates. bla _CTX-M-15 was associated with ISEcp1 and with orf477 in 12 isolates and with ISEcp1, IS26 and orf477 in six others. To the best of our knowledge, this is the first report of bla _CTX-M-15 in hand-dug wells and borehole serving as sources of drinking water and a first report of the genetic environment of bla _CTX-M-15 in environmental bacteria from Nigeria. The results of this study confirm untreated wastewater as an important medium for the spread of ESBL-producing bacteria within the Nigerian environment. Hence, the widespread practice of discharging untreated wastewater into the aquatic ecosystem in Nigeria is a serious risk to public health.

Worldwide Phylogenetic Group Patterns of Escherichia coli from Commensal Human and Wastewater Treatment Plant Isolates

Escherichia coli is an important microorganism in the gastrointestinal tract of warm-blooded animals. Commensal populations of E. coli consist of stable genetic isolates, which means that each individual has only one phylogenetic group (phylogroup). We evaluated the frequency of human commensal E. coli phylogroups from 116 people and observed that the majority of isolates belonged to group A. We also evaluated the frequency of phylogroups in wastewater samples and found a strong positive correlation between the phylogroup distribution in wastewater and human hosts. In order to find out if some factors, such as geographical location, and climate could influence the worldwide phylogroup distribution, we performed a meta-analysis of 39 different studies and 24 countries, including different climates, living areas, and feeding habits. Unexpectedly, our results showed no substructuring patterns of phylogroups; indicating there was no correlation between phylogroup distribution and geographic location, climate, living area, feeding habits, or date of collection.

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.

Emergence of class 1 to 3 integrons among members of Enterobacteriaceae in Egypt

In spite of the role of integrons as the main contributor to multidrug resistance worldwide, their prevalence in Egypt is still underestimated. In this work, we announce the emergence of class 2 and 3 integrons among Enterobacteriacae isolates from Mansoura University Hospitals. Ninety-three clinical isolates were obtained from different clinical sources, among which 70% of E. coli, 94.8% of K. pneumoniae and 85.7% of Enterobacter spp. were assigned to be multidrug resistant (MDR). Subsequently, the occurrence of class 1-3 integrons was confirmed by multiplex PCR. Class 1 integron was the most predominant being harbored by 42.8%, 90% and 25% of MDR E. coli, K. pneumoniae and Enterobacter spp. isolates, respectively. This was followed by class 2 and 3 integrons which were, for the first time, reported in these hospitals. Also, coexistence of integrons 1and 2 was revealed in 36.9% of integron positive isolates. A significant association was noticed only between resistance to gentamicin and integron prevalence among MDR E. coli isolates (P = 0.02). In conclusion, this work represents the first report for detection of class 2 and 3 integrons, beside the previously detected class 1 integrons. This highlights the high incidence of integrons among MDR Enterobacteriacae isolates which indicates the selective pressure of antibiotics in these hospitals. Moreover, this study confirms the possibility of the use of integrons as markers for MDR identification.

Investigation and characterization of β-lactam resistance in Escherichia coli strains isolated from bamboo rats (Rhizomys sinensis) in Zhejiang province, China

This study was undertaken to investigate drug resistance in Escherichia coli (E. coli) strains isolated from bamboo rats in Zhejiang province of China. One hundred and fifty-four E. coli strains were isolated from dead bamboo rats. Polymerase chain reaction (PCR) was used to detect the representative genes encoding resistance to commonly used β-lactam antibiotics. Highest resistance was observed for cefradine (24.03%), followed by penicillin (20.78%) and ceftazidime (20.13%). The isolation rates of β-lactam resistance genes were 53.25, 48.70, 15.58 and 14.29% for bla _TEM, bla _CTX-M, bla _OXA and bla _SHV, respectively, while 62 (40.26%) E. coli isolates harbored multiple β-lactam resistance genes. These results also suggested that long term use of these antibiotics leads to antibimicrobial resistance. We believe that this study will provide a guideline for veterinarians and a research basis for examining resistance-encoding genes in other food animals like bamboo rats.

Detection of Class I and II integrons for the assessment of antibiotic and multidrug resistance among Escherichia coli isolates from agricultural irrigation waters in Bulacan, Philippines

Contaminated irrigation water may greatly affect not only the quality of produce but also the people exposed to it. In this study, agricultural irrigation waters in Bulacan, Philippines were assessed and found to be contaminated with Escherichia coli (E. coli) ranging from 0.58 to 4.51 log₁₀ CFU/mL. A total of 79 isolates of E. coli were confirmed through polymerase chain reaction (PCR) amplifying the uidA gene and were tested for phenotypic resistance using 10 antimicrobials through the Kirby-Bauer disc diffusion method. Forty-six isolates (58.22%) were noted to be multidrug resistant (MDR) with high resistance rate to cephalothin, tetracycline, streptomycin, ampicillin, trimethoprim, nalidixic acid, and chloramphenicol. Moreover, this study also examined the prevalence of Class I and II integrons accounting to 67.39% and 17.39%, respectively, of the MDR E. coli strains using multiplex PCR. The results imply that the agricultural water used in Bulacan is contaminated with the fecal material of man or other animals present in the area, and the presence of MDR bacteria, which pose a potential threat to individuals in these areas, is alarming. In addition, detection of integrons could be a good marker for the identification of MDR isolates. Lastly, this study could develop strategies for the proper management of farming sites leading to the detection of food-borne pathogens and prevention of infectious diseases.

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.

Plasmid-mediated resistance to cephalosporins and quinolones in Escherichia coli from American crows in the USA

American crow (Corvus brachyrhynchos) faeces were tested for Escherichia coli with plasmid-mediated quinolone resistance (PMQR), extended-spectrum beta-lactamases (ESBL) and AmpC beta-lactamases. A total of 590 faecal samples were collected at four roosting sites in the USA and cultivated on selective media. Pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST) were performed to assess clonality. Transferability of resistance genes was studied using conjugation and transformation bioassays. In total, 78 (13%, n = 590) cefotaxime-resistant isolates were obtained, of which 66 and 12 displayed AmpC and ESBL phenotypes, respectively. Fifty-four AmpC-producing isolates carried bla_CMY-2 . Isolates producing ESBLs contained genes bla_CTX-M-27 (5 isolates), bla_CTX-M-15 (4), bla_CTX-M-14 (2) and bla_CTX-M-1 (1). Ninety isolates (15%, n = 590) with reduced susceptibility to ciprofloxacin were obtained, among which 14 harboured PMQR genes aac(6')-Ib-cr (4 isolates), qnrB19 (3), qnrS1 (2), qnrA1 (2), qnrB2 (1), qnrB6 (1) and qnrD3 (1). High genetic diversity was revealed by PFGE and MLST. Epidemiologically important E. coli clones (e.g., ST131, ST405) were identified. Plasmids carrying bla_CMY-2 were assigned predominantly to IncA/C (8 plasmids), IncI1/ST23 (5) and IncI1/ST12 (3). The study demonstrates a widespread occurrence of E. coli with ESBL, AmpC and PMQR genes associated with clinically important multidrug-resistant clones and epidemic plasmids, in American crows.

Distribution of Integrons and Phylogenetic Groups among Enteropathogenic Escherichia coli Isolates from Children <5 Years of Age in Delhi, India

Integrons by means of horizontal gene transfer carry multidrug resistance genes (MDR) among bacteria, including E. coli. The aim of this study was to determine the antibiotic resistance profiles and the genes associated with them, to gain insights in the distribution of phylogroups, prevalence, and characterization of class 1, 2 and 3 integrons among Enteropathogenic E. coli (EPEC) isolates, from children upto 5 years of age from Delhi and National Capital Region (NCR), India. A total of 120 E. coli isolates, including 80 from diarrheagenic E. coli (cases) and 40 from healthy isolates (controls) were recruited in this study. After isolation of E. coli, screening for EPEC was done by conventional multiplex PCR. Antibiotic suseptibility test was performed using disk diffusion method and further confirmed by minimum inhibitory concentration (MICs) by E-test. The presence and characterization of integrons and antimicrobial resistance genes were performed by PCR and DNA sequencing. Phylogeny determination was carried out by quadruplex PCR. EPEC strains were found in 64 of the 80 diarrheagenic cases, out of which 38 were MDR. In the 40 healthy controls, 23 were found to be EPEC strain, out of which only 2 were MDR. Amongst 80 diarrheagenic cases, class 1 integron were observed in 43 isolates, class 2 integron in 12 isolates and 9 isolates were found with co-existence of both. Similarly, in healthy controls; class 1 integron in 9 and class 2 integron in 7 isolates were observed with co-existence in 3 isolates. None of the isolates included class 3 integron. The dfr was the most commonly identified gene cassette within the integron-positive isolates. Phylogenetic studies showed considerable representation of phylogroup B2 in both diarrheagenic cases and healthy controls. This study reiterates the importance of class 1 integron predominantly for acquisition of antibiotic resistance genes among EPEC isolates. Furthermore, it also ascertains the possible association between multidrug resistance and presence of integrons. Approximately 91% of isolates were easily assigned to their respective phylogroups. Assessment of the relationship between antibiotic resistance and dominant phylogroups detected was also attempted. This study also highlights the increased burden of antimicrobial resistance in healthy controls.

Comparison of rates of fecal colonization with extended-spectrum beta-lactamase-producing enterobacteria among patients in different wards, outpatients and medical students

Because asymptomatic carriage of extended-spectrum beta-lactamase (ESBL) producers is a risk factor for infection, data on colonization dynamics are important when planning infection control. This study investigated fecal colonization with ESBL producers among inpatients, outpatients and medical students and compares the characteristics of ESBL producers among these groups. Carriage rates were investigated in 5581 fecal samples; 4343 from inpatients (330, 1397, 619 and 1864 from adult ICUs [intensive care units], adult non-ICUs, pediatric ICUs and pediatric non-ICUs, respectively), 814 from outpatients and 424 from screening of medical students. ESBL producers were characterized by co-resistance, integrons carried, and aminoglycoside resistance and ESBL genes. Dynamic regression models were built to identify relationships between combinations of time series of monthly antibiotic consumption, prevalence of carriers and infected subjects. Inpatients, ICU patients and adults showed higher prevalence than outpatients, non-ICU patients or children (7.4%, 9.3% and 12.0% vs. 3.1%, 6.1% and 4.1%, respectively). Klebsiella pneumoniae was more frequent in ICU patients; dominance of CTX-M-15 producers was more marked in adult than in pediatric inpatients. ESBL carriage was shown to be a consequence of infection in adults in the time-series analysis; antibiotic consumption had little effect. The epidemiology of colonization with ESBL producers differed between pediatric ICU, adult ICU and adult non-ICU patients. In adults, carriage of ESBL producers seems to be the consequence of infection, especially in ICU patients; the main source of colonization is nosocomial acquisition. In contrast, children are less likely to acquire colonizer strains in hospitals; importation of ESBL producers by colonized children seems to be significant.

Fitness costs associated with the acquisition of antibiotic resistance

Acquisition of antibiotic resistance is a relevant problem for human health. The selection and spread of antibiotic-resistant organisms not only compromise the treatment of infectious diseases, but also the implementation of different therapeutic procedures as organ transplantation, advanced surgery or chemotherapy, all of which require proficient methods for avoiding infections. It has been generally accepted that the acquisition of antibiotic resistance will produce a general metabolic burden: in the absence of selection, the resistant organisms would be outcompeted by the susceptible ones. If that was always true, discontinuation of antibiotic use would render the disappearance of resistant microorganisms. However, several studies have shown that, once resistance emerges, the recovery of a fully susceptible population even in the absence of antibiotics is not easy. In the present study, we review updated information on the effect of the acquisition of antibiotic resistance in bacterial physiology as well as on the mechanisms that allow the compensation of the fitness costs associated with the acquisition of resistance.

Prevalence of class 1 and 2 integrons among the multidrug resistant uropathogenic strains of Escherichia coli

Background

Multidrug resistance is a serious problem in the treatment of urinary tract infections. Horizontal gene transfer, directed by strong selective pressure of antibiotics, has resulted in the widespread distribution of multiple antibiotic resistance genes. The dissemination of resistance genes is enhanced when they are trapped in integrons.

Objectives

To determine the prevalence of integrons among multidrug resistant Escherichia coli strains collected from regional hospitals and private clinical laboratories in Alborz province.

Methods

The susceptibility of 111 clinical Escherichia coli isolates was tested using a Kirby–Bauer disk diffusion method for common antibiotics. Isolates were screened for the production of extended spectrum β-lactamases (ESBLs) using a double disk synergy test. The existence of integrons was confirmed by amplification of the integrase gene and their class determined via analysis of PCR products by PCR-RFLP.

Results

Isolates showed the highest resistance to amoxicillin. Nitrofurantoin, amikacin, and ceftizoxime were the most effective antibiotics in vitro. Eighty-eight isolates of 111 (79%) were resistant to more than three unrelated drugs. We found 30% of the multidrug resistant isolates harbor integrons. Class 1 and 2 integrons were detected in 25 and 1 isolates, respectively. ESBL screening of strains showed 45 isolates (40%) were positive; 22% of the ESBL-positive isolates carried class 1 integrons and the frequency of MDR in ESBLpositive isolates was 93%.

Conclusion

The existence of integrons in only 29.5% of multidrug resistant isolates showed that besides integrons, antibiotic resistance genes were probably carried on other transferable elements lacking integrons, such as transposons or plasmids.

Occurrences and Characterization of Antibiotic-Resistant Bacteria and Genetic Determinants of Hospital Wastewater in a Tropical Country

Wastewater discharged from clinical isolation and general wards at two hospitals in Singapore was examined to determine the emerging trends of antibiotic resistance (AR). We quantified the concentrations of 12 antibiotic compounds by analysis using liquid chromatography-tandem mass spectrometry (LC-MS/MS), antibiotic-resistant bacteria (ARB), the class 1 integrase gene (intI1), and 16 antibiotic resistance genes (ARGs) that confer resistance to 10 different clinically relevant antibiotics. A subset of 119 antibiotic-resistant isolates were phylogenetically classified and tested for the presence of ARGs encoding resistance to β-lactam antibiotics (bla_NDM, bla_KPC, bla_SHV, bla_CTX-M), amikacin [aac(6')-Ib], co-trimoxazole (sul1, sul2, dfrA), ciprofloxacin (qnrA, qnrB), and the intI1 gene. Among these resistant isolates, 80.7% were detected with intI1 and 66.4% were found to carry at least 1 of the tested ARGs. Among 3 sampled locations, the clinical isolation ward had the highest concentrations of ARB and the highest levels of ARGs linked to resistance to β-lactam (bla_KPC), co-trimoxazole (sul1, sul2, dfrA), amikacin [aac(6')-Ib], ciprofloxacin (qnrA), and intI1 We found strong positive correlations (P < 0.05) between concentrations of bacteria resistant to meropenem, ceftazidime, amikacin, co-trimoxazole, and ciprofloxacin and abundances of bla_KPC, aac(6')-Ib, sul1, sul2, dfrA, qnrA, and intI1 genes.

Dissemination of Trimethoprim-Sulfamethoxazole Drug Resistance Genes Associated with Class 1 and Class 2 Integrons Among Gram-Negative Bacteria from HIV Patients in South India

The antibiotic, trimethoprim-sulfamethoxazole (TMP-SMX), is generally used for prophylaxis in HIV individuals to protect them from Pneumocystis jiroveci infection. Long-term use of TMP-SMX develops drug resistance among bacteria in HIV patients. The study was aimed to detect the TMP-SMX resistance genes among gram-negative bacteria from HIV patients. TMP-SMX-resistant isolates were detected by the Kirby-Bauer disc diffusion method. While TMP resistance genes such as dfrA1, dfrA5, dfrA7, and dfrA17 and SMX resistance genes such as sul1 and sul2 were detected by multiplex PCR, class 1 and class 2 integrons were detected by standard monoplex PCR. Of the 151 TMP-SMX-resistant bacterial isolates, 3 were positive for sul1 alone, 48 for sul2 alone, 11 for dfrA7 alone, 21 for sul1 and sul2, 1 for sul1 and dfrA7, 23 for sul2 and dfrA7, 2 for sul2 and dfrA5, 41 for sul1, sul2, and dfrA7, and 1 for sul2, dfrA5, and dfrA7. Of 60 TMP-SMX-resistant isolates positive for integrons, 44 had class 1 and 16 had class 2 integrons. It was found that the prevalence of sul genes (n = 202; p < 0.001) was higher compared with dfr genes (n = 80; p < 0.001), and 87.4% (n = 132; p < 0.001) of TMP-SMX-resistant isolates also were positive for β-lactamase production. This type of study is reported for the first time from HIV patients in India. Therefore, this study indicates that dissemination of TMP-SMX resistance genes and class 1 and class 2 integrons along with β-lactamase production among gram-negative bacteria in HIV patients will certainly make their treatment to bacterial infections more complicated in clinical settings.

Characterization of Integrons and qnr Genes in Proteeae from a Teaching Hospital in China

BACKGROUND

Proteeae isolates displaying multidrug-resistance (MDR) are the second most common causes of hospital-associated infections. The aim of this study was to screen class 1-3 integrons and plasmid-mediated quinolone resistance (PMQR) genes in Proteeae isolates from the First Affiliated Hospital of the Wenzhou Medical University.

MATERIALS AND METHODS

176 Proteeae isolates were collected from clinical specimens of inpatients between January 2011 and December 2013. Susceptibility testing was determined by the agar dilution method. Class 1-3 integrons and PMQR genes were amplified by polymerase chain reaction, and the variable regions of integrons were determined by restriction fragment length polymorphisms.

RESULTS

68.2% Proteeae isolates exhibited MDR phenotypes: 46.6 and 10.8% Proteeae isolates were positive for intI1 and intI2, respectively. The resistance rate of integron-positive isolates to aminoglycosides, fluoroquinolones, and trimethoprim/sulfamethoxazole was significantly higher than integron-negative isolates. Sequence analysis revealed that dfrA1-sat2-aadA1, dfrA1-catB2-sat2-aadA1, and sat2-aadA1 were first detected in Morganella morganii strains isolated from China. PMQR was determined by qnrD in 40 strains (22.7%).

CONCLUSION

Our results indicate that class 1 and 2 integrons are common among Proteeae isolates. Meanwhile, qnrD are highly prevalent in Proteeae isolated from our hospital.

The Molecular Epidemiology of Resistance in Cefotaximase-Producing Escherichia coli Clinical Isolates from Dublin, Ireland

In view of continued high clinical prevalence of infections involving extended-spectrum β-lactamase (ESBL)-producing Escherichia coli, this study sought to characterise the blaCTX-M genes, their associated mobile genetic elements and the integrons present in 100 ESBL-producing E. coli isolates collected in a Dublin hospital and associated community healthcare facilities. Polymerase chain reaction (PCR) mapping and sequencing was used to detect blaCTX-M alleles, their associated insertion sequences (ISs) and class 1 and 2 integrons in the collection. ESBL plasmids were characterised by PCR-based replicon typing and replicon sequence typing (RST). Cefotaximases were harboured by 94% of isolates (66 blaCTX-M-15, 8 blaCTX-M-14, 7 blaCTX-M-1, 4 blaCTX-M-3, 3 blaCTX-M-9, 2 blaCTX-M-27, 2 blaCTX-M-55, 1 blaCTX-M-32 and 1 blaCTX-M-2). An ISEcp1 promoter was linked to a group 1 blaCTX-M gene in 45% of isolates. A further 34% of isolates contained blaCTX-M-15 downstream of IS26, an arrangement typical of epidemic UK strain A. Class 1 integrons were found in 66% of isolates, most carrying trimethoprim/aminoglycoside resistance genes. CTX-M plasmids were primarily of multireplicon IncF or IncI1 type, but IncN and unidentified types were also found. Novel IncF RSTs F1:A-:B-, F45:A1:B-, F45:A4:B- and a novel IncI1 sequence type, ST159, were identified. CTX-M plasmids and integrons resembled those identified recently in animal isolates from Ireland and Western Europe. The molecular epidemiology of CTX-M-producing E. coli in Dublin suggests that horizontal spread of mobile genetic elements contributes to antimicrobial resistant human infections. Further investigations into whether animals or animal products represent an important local reservoir for these elements are warranted.

Community fecal carriage of broad-spectrum cephalosporin-resistant Escherichia coli in Tunisian children

The spread of extended spectrum β-lactamases (ESBL) and plasmid mediated AmpC β-lactamases (pAmpC) was evaluated in Escherichia coli strains collected from the intestinal microbiota of healthy children in Tunisia. The carriage rate of CTX^RE. coli was 6.6% (7 of 105 samples) and one strain/sample was further characterized (7 isolates). These isolates harbored bla_CTX-M-1 (n = 4), bla_CTX-M-15 (n = 2), and bla_CMY-2 gene (n = 1), which were usually located on FIB replicon type and carried class 1 integrons. The acc(6')-Ib-cr variant was identified in one isolate that harbored bla_CTX-M-15. CTX^RE. coli isolates were genetically unrelated and belonged to B1 (n = 3/ST155/ST398/ST58), D (n = 2/ST117/ST493), B2 (n = 1/ST127), and A (n = 1/ST746) phylogroups. Strain virulence scores varied from 3 to 12, and frequently harbored the pathogenicity island PAI IV₅₃₆. The intestinal tract of healthy children constitute an important reservoir of ESBL producing E. coli. Thus, improvement of hygiene measures mainly in the school environment and rational use of antibiotics would be of great help in preventing selection and diffusion of resistant strains from intestinal microbiota.

Salmonella enterica resistant to antimicrobials in wastewater effluents and black-headed gulls in the Czech Republic, 2012

We investigated the presence and epidemiological relatedness of Salmonella isolates from a wastewater treatment plant (WWTP) in Brno, Czech Republic and from nestlings of black-headed gulls (Chroicocephalus ridibundus) at the Nove Mlyny waterworks, situated 35 km downstream from the WWTP. During 2012, we collected 37 wastewater samples and 284 gull cloacal swabs. From wastewater samples, we obtained 89 Salmonella isolates belonging to 19 serotypes. At least one resistant strain was contained in 89% of those samples. Ten different serotypes of Salmonella were detected in 38 young gulls, among which 14 (37%) were resistant to antimicrobials. Wastewater isolates were mostly resistant to sulphonamides and tetracycline, gull isolates to tetracycline and ampicillin. We detected the occurrence of blaTEM-1,tet(A), tet(B), tet(G), sul1, sul2, sul3, floR and strA resistance genes. For the first time, we identified a class 1 integron with the dfrA12-orfF-aadA2 gene cassette in S. Infantis. Using pulsed-field gel electrophoresis, we confirmed the presence of identical clusters of S. Agona, S. Enteritidis PT8, S. Infantis and S. Senftenberg in wastewater and black-headed gulls, thus indicating the possibility of resistant Salmonella isolates spreading over long distances in the environment.

Carriage of Class 1 and 2 Integrons in Quinolone, Extended-Spectrum-β-Lactamase-Producing and Multi Drug Resistant E.coli and K.pneumoniae: High Burden of Antibiotic Resistance

PURPOSE

The study aimed at assessing any association between quinolone resistance, MDR and ESBL production and their relation with the presence of integrons in Esherichia coli and Klebsiella pneumoniae.

METHODS

E.coli and K.pneumoniae isolated from various clinical infections were fully identified and analyzed for being quinolone resistant. These isolates were further tested for ESBL production, multi drug resistance and carriage of integrons.

RESULTS

In total, 135 isolates were confirmed as quinolone resistant. K.pneumoniae was observed as potent ESBL producer in comparison to E.coli. Ciprofloxacin resistance in both organisms was related significantly with the presence of integron class 1, co-presence of class 1 and 2 as well as to the presence of ESBL production (p< 0.001). However, nalidixic acid resistance was related significantly (p< 0.01) with only integron class 1 and to the presence of ESBL production. Class 1 and 2 integrons were found in 73.5% of MDR isolates with 13.2% of them possessing both intI1 and intI2 genes.

CONCLUSION

Prevalence of quinolone resistance together with ESBL production and MDR in E.coli and K.pneumoniae has contributed to the emergence of antibacterial resistance burden. The higher integron prevalence in our isolates advocates the potentiality of these isolates as a source for dissemination of resistance determinants.

Prevalence of class 1 and 2 integrons in multi-drug resistant Escherichia coli isolated from aquaculture water in Chaharmahal Va Bakhtiari province, Iran

BACKGROUND

Integrons play important role in the spread and maintenance of antimicrobial resistance among strains of Escherichia coli (E. coli) and other species of Enterobacteriaceae. This study investigated the prevalence of class 1 and 2 integrons among E. coli strains isolated from aquaculture water of fish fields in Iran.

METHODS

One hundred and fifty water samples from different geographical regions in Chaharmahal Va Bakhtiari province were examined over a 2 months period. Isolation was through culture and biochemical tests. Integrons were identified through polymerase chain reaction (PCR) using oligonucleotide primers specific for class 1 and 2 integrons. Antimicrobial susceptibility testing was carried out using disc diffusion methods.

RESULTS

Eighteen percent of the water samples were positive for E. coli. All the strains were multi-drug resistant; 100% to ciprofloxacin, chloramphenicol, gentamycin, ampicillin and tetracycline and least resistant to imipenem (7.2%). Ten (50%) of the most resistant strains were positive for class 1 (40%) and class 2 (10%).

CONCLUSIONS

Escherichia coli in aquaculture in Iran carried integrons class 1 and 2 which could be of public health concern since they could play a role in the spread and maintenance of antimicrobial resistance among bacterial population in the region and should be constantly monitored.

Prevalence of Class 1 Integrons and Extended Spectrum Beta Lactamases among Multi-Drug Resistant Escherichia coli Isolates from North of Iran

Background:

Extended spectrum beta lactamases (ESBLs) are an important cause of transferable multidrug resistance (MDR) in gram-negative bacteria. The most described ESBL genes are generally found within integron-like structures as mobile genetic elements. The aim of this study was to identify the accompanying of class 1 integrons and ESBLs in the MDR E. coli isolates.

Methods:

Susceptibility to antimicrobial agents was determined for 33 E. coli strains by the disk diffusion method. Double-disk synergy test was applied for screening ESBL. To identify the strains carrying integrons, the conserved regions of integron-encoded integrase gene intI1 were amplified. For detection of gene cassettes, 5′CS and 3′CS primers were used.

Results:

All E. coli isolates were identified as multi-drug resistant. More than 50% of the isolates were resistant to tetracycline, cephalothin, cefuroxime, amoxicillin-clavulanic acid, and third generation cephalosporines. Nearly all of the isolates displayed sensitivity to piperacillin. There was a significant correlation between production of ESBL and resistance to all antibiotics except for ciprofloxacin and piperacillin (P < 0.01). Thirty two MDR strains (97%) included class 1 integron, and some isolates that included integrons were similar in the size of gene cassettes. The isolates were different in the resistance profiles; however, some others had similar resistance profiles. Of eight ESBL positive isolates, seven (87.5%) carried class 1 integrons.

Conclusion:

Class 1 integrons were frequent in MDR and also ESBL-producing E. coli isolates. High prevalence of class 1 integrons confirms that integron-mediated antimicrobial gene cassettes are important in E. coli resistance profile.

Phylogeny and Comparative Genomics Unveil Independent Diversification Trajectories of qnrB and Genetic Platforms within Particular Citrobacter Species

To gain insights into the diversification trajectories of qnrB genes, a phylogenetic and comparative genomics analysis of these genes and their surrounding genetic sequences was performed. For this purpose, Citrobacter sp. isolates (n = 21) and genome or plasmid sequences (n = 56) available in public databases harboring complete or truncated qnrB genes were analyzed. Citrobacter species identification was performed by phylogenetic analysis of different genotypic markers. The clonal relatedness among isolates, the location of qnrB genes, and the genetic surroundings of qnrB genes were investigated by pulsed-field gel electrophoresis (PFGE), S1-/I-CeuI-PFGE and hybridization, and PCR mapping and sequencing, respectively. Identification of Citrobacter isolates was achieved using leuS and recN gene sequences, and isolates characterized in this study were diverse and harbored chromosomal qnrB genes. Phylogenetic analysis of all known qnrB genes revealed seven main clusters and two branches, with most of them included in two clusters. Specific platforms (comprising pspF and sapA and varying in synteny and/or identity of other genes and intergenic regions) were associated with each one of these qnrB clusters, and the reliable identification of all Citrobacter isolates revealed that each platform evolved in different recognizable (Citrobacter freundii, C. braakii, C. werkmanii, and C. pasteurii) and putatively new species. A high identity was observed between some of the platforms identified in the chromosome of Citrobacter spp. and in different plasmids of Enterobacteriaceae. Our data corroborate Citrobacter as the origin of qnrB and further suggest divergent evolution of closely related qnrB genes/platforms in particular Citrobacter spp., which were delineated using particular genotypic markers.

Occurrence of bla CTX-M-1, qnrB1 and virulence genes in avian ESBL-producing Escherichia coli isolates from Tunisia

Avian ESBL-producing Escherichia coli isolates have been increasingly reported worldwide. Animal to human dissemination, via food chain or direct contact, of these resistant bacteria has been reported. In Tunisia, little is known about avian ESBL- producing E. coli and further studies are needed. Seventeen ESBL-producing Escherichia coli isolates from poultry feces from two farms (Farm 1 and farm 2) in the North of Tunisia have been used in this study. Eleven of these isolates (from farm 1) have the same resistance profile to nalidixic acid, sulfonamides, streptomycin, tetracycline, and norfloxacine (intermediately resistant). Out of the six isolates recovered from farm 2, only one was co-resistant to tetracycline. All isolates, except one, harbored bla_CTX-M-1 gene, and one strain co-harbored the bla_TEM-1 gene. The genes tetA and tetB were carried, respectively, by 11 and 1 amongst the 12 tetracycline-resistant isolates. Sulfonamides resistance was encoded by sul1, sul2, and sul3 genes in 3, 17, and 5 isolates, respectively. The qnrB1 was detected in nine strains, one of which co-harbored qnrS1 gene. The search for the class 1 and 2 integrons by PCR showed that in farm 1, class 1 and 2 integrons were found in one and ten isolates, respectively. In farm 2, class 1 integron was found in only one isolate, class 2 was not detected. Only one gene cassette arrangement was demonstrated in the variable regions (VR) of the 10 int2-positive isolates: dfrA1- sat2-aadA1. The size of the VR of the class 1 integron was approximately 250 bp in one int1-positive isolate, whereas in the second isolate, no amplification was observed. All isolates of farm 1 belong to the phylogroup A (sub-group A0). However, different types of phylogroups in farm 2 were detected. Each of the phylogroups A1, B2₂, B2₃ was detected in one strain, while the D2 phylogroup was found in 3 isolates. The virulence genes iutA, fimH, and traT were detected in 3, 7, and 3 isolates, respectively. Two types of gene combination were detected: iutA+fimH+traT in 3 isolates and iutA+fimH in one isolate. The isolates recovered in farm 1 showed the same profile of PFGE macro-restriction, while isolates of farm 2 presented unrelated PFGE patterns. We conclude that these avian ESBL-producing E. coli isolates show homo- and heterogenic genetic background and that plasmids harboring ESBL genes could be involved in the dissemination of this resistance phenotype.

Distribution of Integrons and Gene Cassettes Among Uropathogenic and Diarrheagenic Escherichia coli Isolates in Iran

Integrons are considered to play a significant role in the evolution and spread of antimicrobial resistance genes. A total of 200 uropathogenic (UPEC) and diarrheagenic Escherichia coli (DEC) isolates from outpatients were investigated for antimicrobial susceptibility and the presence of class 1, 2, and 3 integron-associated integrase (intI) genes and gene cassettes. Conjugal transfer and Southern hybridization were performed to determine the genetic localization of class 1 integrons. One hundred ninety-two (96%) isolates were resistant to one or more antimicrobial agents. Antimicrobial resistance among DEC isolates was higher compared with the UPEC. Integrons were highly prevalent in both pathotypes (92.5%). Comparison of integrons among UPEC and DEC showed that DEC isolates harbored integrases (94% for intI1, 8% for intI2) with a slightly higher frequency than in UPEC isolates (87% for intI1, 7% for intI2) (p>0.05). Dihydrofolate reductase (dfrA) and aminoglycoside adenyl transferase (aad) gene cassettes were found most frequently in intI1-positive isolates. All isolates carried their class 1 integrons on conjugative plasmids. These results indicate that class 1 integrons are widespread among E. coli isolates. Therefore, appropriate surveillance and control measures are essential to prevent the further spread of integron-producing isolates.

Phenotypic and molecular characterization of extended-spectrum beta-lactamase-producing Escherichia coli in Bangladesh

Background

Resistance to cephalosporins in Enterobacteriaceae is mainly due to the production of extended-spectrum beta-lactamase (ESBL). Little is known about ESBL-producing bacteria in Bangladesh. Therefore, the study presents results of phenotypic and molecular characterization of ESBL-producing Escherichia coli from hospitals in Bangladesh.

Methods

A total of 339 E. coli isolated from patients with urinary tract and wound infections attending three different medical hospitals in urban and rural areas of Bangladesh between 2003–2007 were screened for ESBL-production by the double disk diffusion test. Isolates with ESBL-phenotype were further characterized by antibiotic susceptibility testing, PCR and sequencing of different β-lactamase and virulence genes, serotyping, and XbaI-macrorestriction followed by pulsed-field gel electrophoresis (PFGE).

Results

We identified 40 E. coli with ESBL phenotype. These isolates were resistant to ceftriaxone, ceftazidime, cefotaxime, aztreonam, cefepime, and nalidixic acid but remained susceptible to imipenem. All but one isolate were additionally resistant to ciprofloxacin, and 3 isolates were resistant to cefoxitin. ESBL genes of blaCTX-M-1-group were detected in all isolates; blaTEM-type and blaOXA-1-type genes were detected in 33 (82.5%) and 19 (47.5%) isolates, respectively. Virulence genes that are present in diarrhoeagenic E. coli were not found. Class-1 integron was present in 20 (50%) isolates. All the ESBL-producing E. coli isolates harbored plasmids ranging between 1.1 and 120 MDa. PFGE-typing revealed 26 different pulsotypes, but identical pulsotype showed 6 isolates of serotype O25:H4.

Conclusion

The prevalence of multidrug-resistant ESBL-producing E. coli isolates appears to be high and the majority of the isolates were positive for bla_CTX-M. Although there was genetic heterogeneity among isolates, presence of a cluster of isolates belonging to serotype O25:H4 indicates dissemination of the pandemic uropathogenic E. coli clone in Bangladesh.

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.

Molecular characterization of integrons in clinical isolates of betalactamase-producing Escherichia coli and Klebsiella pneumoniae in Iran

Integrons are considered to play a significant role in the evolution and spread of antibiotic resistance genes. A total of 349 clinical isolates of Escherichia coli and Klebsiella pneumoniae were investigated for molecular characterization of integrons and betalactamases. Antimicrobial susceptibility testing was also performed as the Clinical and Laboratory Standards Institute (CLSI) guidelines. The frequency of extended spectrum betalactamases (ESBL) or metallo-betalactamases (MBL)-producing isolates, patient demographics, and the susceptibility to various antimicrobial agents were described. BlaCTX-M was the most frequently detected betalactamase in all isolates. Moreover, MBL producing K. pneumoniae carried blaIMP and blaVIM at 100 and 41·6%, respectively but no MBL-positive E. coli was detected. Class 1 integrons were more frequent among E. coli and K. pneumoniae isolates in comparison with class 2 integrons and the frequency of intI2 in K. pneumoniae was significantly higher than E. coli isolates. Five different resistance gene arrays were identified among class 1 integrons. Dihydrofolate reductase (dfrA) and aminoglycoside adenyltransferase (aad) gene cassettes were found to be predominant in the class 1 integrons. These results indicate that class 1 integrons are widespread among ESBL-producing isolates of K. pneumoniae and E. coli and appropriate surveillance and control measures are essential to prevent further dissemination of these elements among Enterobacteriaceae in our country.

Antimicrobial-resistant Enterobacteriaceae from humans and wildlife in Dzanga-Sangha Protected Area, Central African Republic

Antimicrobial resistance is a worldwide concern of public health. Unfortunately, resistant bacteria are spreading to all ecosystems, including the strictly protected ones. We investigated antimicrobial resistance in gastrointestinal Enterobacteriaceae of wild mammals and people living within Dzangha-Sangha Protected Areas, Central African Republic, with an emphasis on extended-spectrum β-lactamase (ESBL) and plasmid-mediated quinolone resistance (PMQR) genes. We compare resistance genes found in microbiota of humans, gorillas habituated and unhabituated to humans and other wildlife. In gorillas, we additionally investigate the presence of ESBL resistant isolates after treatment by ceftiofur. We found a considerable prevalence of multiresistant Enterobacteriaceae isolates with ESBL and PMQR genes in humans (10% and 31%, respectively). Among wildlife the most significant findings were CTX-M-15-producing Klebsiella pneumoniae in a habituated gorilla and a multiresistant Escherichia coli isolate with gene qepA in an unhabituated gorilla. Other isolates from wildlife were mostly represented by qnrB-harboring Citrobacter spp. The relatedness of resistant E. coli was investigated in a PFGE-based dendrogram; isolates from gorillas showed less than 80% similarity to each other and less than 80% similarity to human isolates. No ESBL-producing isolates were found in animals treated by ceftiofur. Although we did not detect any bacterial clone common to wildlife and humans, we detected an intersection in the spectrum of resistance genes found in humans and gorillas, represented by blaCTX-M-15 and qepA.

Extended-spectrum β-lactamase- and AmpC-producing enterobacteria in healthy broiler chickens, Germany

During 2010, we evaluated the presence of extended-spectrum β-lactamase– and AmpC-producing enterobacteria in broiler chickens at slaughter. Samples (70 carcasses and 51 ceca) from 4 flocks were analyzed by direct plating and after enrichment. Extended-spectrum β-lactamase producers were found in 88.6% and 72.5% of carcasses and ceca, respectively; AmpC producers were found in 52.9% and 56.9% of carcasses and ceca, respectively. Most isolates were identified as Escherichia coli; Enterobacter cloacae (cecum) and Proteus mirabilis (carcass) were found in 2 samples each. Molecular characterization revealed the domination of CTX-M genes; plasmidic AmpC was CIT-like. Phylogenetic grouping of E. coli showed types A (31.5%), B1 (20.2%), B2 (13.5%), and D (34.8%). These findings provide evidence that healthy broilers in Germany are a source for the dissemination of transmissible resistance mechanisms in enterobacteria brought from the rearing environment into the food chain during slaughtering.

Commensal Enterobacteriaceae as reservoirs of extended-spectrum beta-lactamases, integrons, and sul genes in Portugal

Bacteria colonizing the human intestine have a relevant role in the spread of antimicrobial resistance. We investigated the faecal carriage of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae in healthy humans from Portugal and analyzed the distribution of sul genes and class 1 and 2 integrons. Faecal samples (n = 113) were recovered from healthy persons (North/Centre of Portugal, 2001-2004) and plated on MacConkey agar with and without ceftazidime (1 mg/L) or cefotaxime (1 mg/L). Isolates representing different morphotypes/plate and antibiotic susceptibility patterns (n = 201) were selected. Isolates resistant to sulfonamides and/or streptomycin, gentamicin, and trimethoprim were screened (PCR and sequencing) for sul genes (sul1, sul2, sul3) and class 1 and 2 integrons. Presence of ESBLs was inferred using the double disk synergy test (DDST) and further confirmed by PCR and sequencing. ESBL producers were selected for clonal analysis, plasmid characterization and conjugation assays by standard methods. ESBL-producing isolates were found in 1.8% (2/113) of samples, corresponding to Escherichia coli of phylogroups A (n = 1) and B1 (n = 1) carrying transferable bla CTX-M-14 and the new bla TEM-153, respectively. A 80kb IncK plasmid bearing bla CTX-M-14 was found, being highly related to that widely spread among CTX-M-14 producers of humans and animals from Portugal and other European countries. sul genes were found in 88% (22/25; sul2-60%, sul1-48%, sul3-4%) of the sulfonamide resistant isolates. Class 1 integrons were more frequently found than class 2 (7%, 14/201 vs. 3%, 6/201). Interestingly, gene cassette arrangements within these platforms were identical to those commonly observed among Enterobacteriaceae from Portuguese food-producing animals, although aadA13 is here firstly described in Morganella morganii. These results reinforce the relevance of human commensal flora as reservoir of clinically relevant antibiotic resistance genes including bla ESBLs, and highly transferable genetic platforms as IncK epidemic plasmids.

The novel CTX-M-116 β-lactamase gene discovered in Proteus mirabilis is composed of parts of the CTX-M-22 and CTX-M-23 genes

The novel β-lactamase gene bla(CTX-M-116) was identified in a Proteus mirabilis nosocomial isolate recovered from the urine of a patient in Moscow in 2005. DNA sequence analysis showed bla(CTX-M-116) to be a hybrid gene consisting of 5' bla(CTX-M-23) (nucleotides 1 to 278) and 3' bla(CTX-M-22) (nucleotides 286 to 876) moieties separated by an intervening putative site of recombination (GTTAAAT). A retrospective analysis of available bla(CTX-M) genes in the GenBank database revealed 19 bla(CTX-M) genes that display the same hybrid structure.