Prevalence of bacterial resistance to quinolones and other antimicrobials among avian Escherichia coli strains isolated from septicemic and healthy chickens in Spain

Antibiotic Resistance Patterns and mcr-1 Detection in Avian Pathogenic Escherichia coli Isolates from Commercial Layer and Layer Breeder Flocks Demonstrating Colibacillosis in Greece

Objectives: The aim of this study was to investigate the antimicrobial resistance (AMR) patterns of Escherichia coli strains isolated from poultry flocks suffering from colibacillosis in Greece and to detect the presence of the mcr-1 gene in isolates being phenotypically resistant to colistin. Results: A total of 150 E. coli strains were isolated from commercial layers and layer breeder flocks in Greece and tested for antimicrobial susceptibility. A high level of susceptibility was revealed for cephalosporins, neomycin, and colistin. Susceptibility varied for other antimicrobials (tetracycline, doxycycline, lincospectin, trimethoprim/sulfamethoxazole, enrofloxacin, amoxicillin), whereas no susceptibility was reported for macrolides, tiamulin, lincomycin, oxacillin. Concerning colistin resistance, 20 E. coli strains were found to be phenotypically resistant (13 strains showed intermediate resistance pattern and 7 strains fully resistance trait). Further investigation was performed by PCR, which has revealed the presence of the mcr-1 gene in one phenotypically colistin-resistant isolate. Conclusion: AMR is prevalent in layer poultry production, including resistance against colistin confirmed by the presence of the mcr-1 gene.

Ameliorating effect of Withania somnifera root extract in Escherichia coli-infected broilers

The present study was undertaken to investigate the effect of aqueous Withania somnifera root (WSR) extract in broiler chicks experimentally infected with Escherichia coli O78 @ 10⁷ CFU/0.5 ml intraperitoneally. Clinical signs and mortality due to colibacillosis observed in infected chicks were mild and lasted for short duration in WSR extract supplemented group as compared with the nonsupplemented group. A significant increase in serum alanine transaminase, aspartate transaminase, lactate dehydrogenase, and creatine phosphokinase activities and a decrease in total protein and albumin concentrations were observed in the infected groups, though these changes were of lower magnitude in WSR extract supplemented group. A significantly higher activity of oxidative blood parameters such as superoxide dismutase, catalase, glutathione reductase, and glutathione-S-transferase enzymes were noticed in WSR extract supplemented group. The WSR extract supplemented group revealed significantly higher E. coli–specific antibody titer and enhanced lymphocyte proliferation response as compared with the nonsupplemented group. The gross and histopathological lesions of colibacillosis were mild in the WSR extract–supplemented infected group as compared with the nonsupplemented infected group. Withania somnifera root extract supplementation produced 31.48 and 34.38% protection in the gross and histopathological lesions in E. coli infected chicks, respectively. It is concluded that supplementation of 20% WSR extract @ 20 ml/L of water caused a reduction in the severity, mortality, and recovery period of E. coli infection and enhanced the humoral and cellular immune responses suggesting its protective effect on limiting the pathology of E. coli infection in broiler chickens.

Removal of Antibiotics from Water by Polymer of Intrinsic Microporosity: Isotherms, Kinetics, Thermodynamics, and Adsorption Mechanism

Traces of antibiotics within domestic and industrial effluents have toxic impact on human health as well as surrounding flora and fauna. Potential increase in antibiotic resistance of microorganisms is likely to rise due to the incomplete removal of antibiotics by traditional wastewater processing, methods such as membrane filtration and biological treatment. In this study, we investigated a novel class of material termed Polymer of Intrinsic Microporosity (PIM) that is based on amorphous microporous organic materials for the application of antibiotic removal form aqueous environments. The adsorption of four commonly used antibiotics (doxycycline, ciprofloxacin, penicillin G, and amoxicillin) was evaluated and found that at least 80% of the initial concentrations was eliminated under the optimized conditions. Langmuir and Freundlich models were then employed to correlate the equilibria data; the Freundlich model fit well the data in all cases. For kinetic data, pseudo-first and second order models were examined. Pseudo-second order model fit well the kinetic data and allowed the calculation of the adsorption rate constants. Thermodynamic parameters were obtained by conducting the adsorption studies at varied reaction temperatures. Surface potential, adsorption at various solution pHs, thermogravimetric analysis (TGA), Infrared spectroscopy (IR), and surface area experiments were conducted to draw possible adsorption mechanisms. The removal of antibiotics from water by PIM-1 is likely to be governed by both surface and pore-filling adsorption and could be facilitated by electrostatic interactions between the aromatic rings and charged functional groups as well as hydrogen bond formation between the adsorbent and adsorbate. Our work shows that the application of such novel microporous material could contribute to the removal of such challenging and persistent contaminants from wastewater with further optimizations of large-scale adsorption processes.

Autoinducer2 affects trimethoprim-sulfamethoxazole susceptibility in avian pathogenic Escherichia coli dependent on the folate synthesis-associate pathway

Avian pathogenic Escherichia coli (APEC) causes airsacculitis, polyserositis, septicemia, and other mainly extraintestinal diseases in chickens, ducks, geese, pigeons, and other avian species, and is responsible for great economic losses in the avian industry. The autoinducer 2 (AI‐2) quorum sensing system is widely present in many species of gram‐negative and gram‐positive bacteria and has been proposed to be involved in interspecies communication. In clinical APEC strains, whether or not AI‐2 affects the expression of antibiotic‐related genes has not been reported. In this study, we have reported that exogenous AI‐2 increase the susceptibility of APEC strains to trimethoprim‐sulfamethoxazole (SXT) in a folate synthesis‐dependent pathway but not in the LsrR‐dependent manner. Our results further explained that exogenous AI‐2 can down regulate the transcription of the folate synthetase encoding genes folA and folC, and the folate synthesis‐related genes luxS, metE, and metH. Gel shift assays confirmed that LsrR, the AI‐2 receptor, did not bind to the promoters of folA and folC, suggesting that exogenous AI‐2 might influence folate metabolism by a feedback inhibition effect but not in the LsrR‐dependent pathway. This study might provide further information in the search for potential drug targets for prophylaxis of avian colibacillosis and for auxiliary antibiotics in the treatment of avian colibacillosis.

Matrix-assisted laser desorption-ionization-time-of-flight mass spectrometry as a reliable proteomic method for characterization of Escherichia coli and Salmonella isolates

Aim:

Identification of pathogenic clinical bacterial isolates is mainly dependent on phenotypic and genotypic characteristics of the microorganisms. These conventional methods are costive, time-consuming, and need special skills and training. An alternative, mass spectral (proteomics) analysis method for identification of clinical bacterial isolates has been recognized as a rapid, reliable, and economical method for identification. This study was aimed to evaluate and compare the performance, sensitivity and reliability of traditional bacteriology, phenotypic methods and matrix-assisted laser desorption-ionization-time-of-flight mass spectrometry (MALDI-TOF MS) in the identification of clinical Escherichia coli and Salmonella isolates recovered from chickens.

Materials and Methods:

A total of 110 samples (cloacal, liver, spleen, and/or gall bladder) were collected from apparently healthy and diseased chickens showing clinical signs as white chalky diarrhea, pasty vent, and decrease egg production as well as freshly dead chickens which showing postmortem lesions as enlarged liver with congestion and enlarged gall bladder from different poultry farms.

Results:

Depending on colonial characteristics and morphological characteristics, E. coli and Salmonella isolates were recovered and detected in only 42 and 35 samples, respectively. Biochemical identification using API 20E identification system revealed that the suspected E. coli isolates were 33 out of 42 of colonial and morphological identified E. coli isolates where Salmonella isolates were represented by 26 out of 35 of colonial and morphological identified Salmonella isolates. Serological identification of isolates revealed that the most predominant E. coli serotypes were O1 and O78 while the most predominant Salmonella serotype of Salmonella was Salmonella Pullorum. All E. coli and Salmonella isolates were examined using MALDI-TOF MS. In agreement with traditional identification, MADI-TOF MS identified all clinical bacterial samples with valid scores as E. coli and Salmonella isolates except two E. coli isolates recovered from apparently healthy and diseased birds, respectively, with recovery rate of 93.9% and 2 Salmonella isolates recovered from apparently healthy and dead birds, respectively, with recovery rate of 92.3%.

Conclusion:

Our study demonstrated that Bruker MALDI-TOF MS Biotyper is a reliable rapid and economic tool for the identification of Gram-negative bacteria especially E. coli and Salmonella which could be used as an alternative diagnostic tool for routine identification and differentiation of clinical isolates in the bacteriological laboratory. MALDI-TOF MS need more validation and verification and more study on the performance of direct colony and extraction methods to detect the most sensitive one and also need using more samples to detect sensitivity, reliability, and performance of this type of bacterial identification.

Serogrouping and antibiotic resistance of Escherichia coli isolated from broiler chicken with colibacillosis in center of Algeria

AIM

Colibacillosis is considered as one of the major bacterial infections in avian pathology. The excessive use of antibiotics reduced their effectiveness, which eventually led to the risk of emergence of antibiotic resistance. The aim of this study was to isolate, identify and serotype the pathogenic Escherichia coli strains and to determine their antibiotic susceptibility.

MATERIALS AND METHODS

A total of 180 samples from different organs of broilers with colibacillosis lesions were collected (liver, spleen, lung, and heart) in center of Algeria. The isolation and identification of E. coli were carried out using conventional techniques. Then, these strains were serotyped and tested over 13 antibiotics.

RESULTS

A total of 156 strains of E. coli were isolated. Serotyping results showed that 50 strains belong to 3 serotypes (23 for O1, 11 for O2, 16 for O78) which represent 32% of isolates. The antimicrobial susceptibility test, presented high level of resistance to tetracyclines (94.12%), flumequine (91.5%), sulfamethoxazole-trimethoprim (88.89%), enrofloxacin (86.27%), nalidixic acid (85.62%), ampicillin (83.01%) and doxycycline (75.81%), medium level resistance to chloramphenicol (39.22%), and amoxicillin-clavulanic acid (43.13%). All the strains were susceptible to cefotaxime, excepting three, which presented an extended spectrum β-lactamase (ESBL). In addition, the results of multi-resistance showed that all the strains were resistant at the minimum to two antibiotics and 66.66% of strains were resistant to at least seven antibiotics.

CONCLUSION

The antibiotic resistance continues to rise at an alarming rate, and the emergence of ESBL is considered as a threat for public health.

Prevalence of colibacillosis in chickens in greater Mymensingh district of Bangladesh

Aim:

This study was conducted for determination of the prevalence of colibacillosis in chicken in poultry farms in Mymensingh and Tangail districts. Isolation, identification, and antibiogram profile of Escherichia coli were also performed.

Materials and Methods:

A total of 25 chickens manifested clinical signs of colibacillosis were collected from five different poultry farms during natural outbreaks.

Results:

In broiler, the prevalence of colibacillosis was 0.84%, and in layer, prevalence was 0.80%. The prevalence of colibacillosis was 1.0% and 0.5% in 25-30 days old and 31-35 days old broiler, respectively. In case of layer birds, the prevalence was 0.6% in 40-45 days old bird and 1% in 46-50 days old bird. Identity of the E. coli isolate of chicken was confirmed by sugar fermentation, biochemical tests, and polymerase chain reaction assay. Antibiogram profile of E. coli isolate of chicken revealed that it was multidrug resistant (resistant against two antibiotics, such as ampicillin and cefalexin).

Conclusion:

Data of this study suggest that colibacillosis is prevalent in the study areas which underscore the need of implementation of prevention and control measure against this disease.

Escherichia coli strains from ostriches and their sensitivity to antimicrobial substances

Ostriches are bred especially for their high-quality meat. There is a lack of knowledge concerning the ostrich's microflora. Escherichia coli is a commensal microorganism of the poultry intestine, ostriches included. However, some strains may become pathogenic. This study was therefore undertaken to detect coliform bacteria in ostrich faeces and to test their antibiotic profile and sensitivity to enterocins. Faeces (n=54, 18 mixture samples from 3 different age groups of 140 ostriches) were sampled to isolate coliform bacteria. The counts of coliform bacteria varied from 5.69 ± 2.4 log10 CFU/g to 5.73 ± 2.4 CFU/g. Pure colonies were identified using MALDI-TOF MS mass spectrometry and confirmed by phenotypization. Seventy-one strains were allotted to the species E. coli. Sixty-four of those 71 strains caused hemolysis. They were mostly polyresistant to antibiotics. Thirty-two poly-resistant strains of E. coli were sensitive to enterocins. These strains were most sensitive to Ent 9296 (26 strains). Moreover, Ent EM41 produced by E. faecium EM41 (isolated from ostrich faeces) inhibited the growth of 20 strains, reaching activity of 100 AU/ml. Our results indicate the possibility of enterocins being used for prevention/reduction of coliforms. Of course, in vivo studies are also being processed.

Bacterial Uropathogens Causing Urinary Tract Infection and Their Resistance Patterns Among Children in Turkey

Background

Urinary tract infection (UTI) is a common problem in infants and children, as well as adults.

Objectives

The aim of this study was to assess the most common bacterial uropathogens, their susceptibility, and resistance to antibiotics in children with UTI.

Materials and Methods

This study included 7,365 urine samples sent from various departments to the Kars state hospital microbiology laboratory between January 2012 and May 2014. Bacterial isolation from clinical samples was made using standard microbiological methods. Antibiotic susceptibilities were determined by disk diffusion, according to CLSI recommendations.

Results

Bacterial growth was obtained in 1,373 samples (18.5%). The percentage distributions of the isolates were as follows: Escherichia coli, 940 (68.5%); Proteus spp, 183 (13.3%); Staphylococcus spp, 85 (6.2%); Enterococcus spp, 65 (4.7%); Klebsiella, 62 (4.5%); Pseudomonas aeruginosa, 21 (1.5%); and other Gram-negative bacteria and Gram-positive bacteria, 17 (1.2%). UTIs were more prevalent, after two years of age, among females than males (P < 0.001).

Conclusions

The identification of the most common microorganisms causing infectious diseases and regional resistance patterns is important in order to determine the antimicrobial policies and infection control guidelines of hospitals.

Tipagem molecular e resistência aos antimicrobianos em isolados de Escherichia coli de frangos de corte e de tratadores na Região Metropolitana de Curitiba, Paraná

Este estudo verificou o perfil de resistência aos antimicrobianos entre isolados de Escherichia coli de frangos de corte de criação intensiva e de subsistência e dos respectivos tratadores e a similaridade genotípica entre isolados de E.coli de frangos de corte de criação intensiva e isolados de E. coli de tratadores de frangos de criação intensiva pela técnica de Eletroforese em Gel de Campo Pulsado (PFGE). 60 amostras de fezes de frangos de criação intensiva, 60 de frangos de corte de criação de subsistência (caipira) e 20 amostras dos tratadores de frangos de criação intensiva e 20 de tratadores de frangos de criação de subsistência. E. coli foram isoladas, identificadas e submetidas ao teste de suscetibilidade a 12 antimicrobianos. Pela PFGE foram analisados 24 isolados de E. coli de frangos de corte de criação intensiva e oito de tratadores. Em isolados E. coli de frangos de criação intensiva a resistência para a ampicilina foi de 100%, cefotaxima 43%, ceftriaxona 48%, ácido nalidíxico 62%, enrofloxacina 23%, ciprofloxacina 23%, tetraciclina 83% e 45% para trimetoprim-sulfametoxazol. Nos isolados de frangos de criação de subsistência foi de 20%, 0%, 0%, 5%, 2%, 4%, 33% e 8%, respectivamente. Resistência à fosfomicina e à nitrofurantoína foi encontrada em isolados de frangos de criação de subsistência. Em isolados de E. coli de tratadores de frangos de corte de criação intensiva a resistência para ampicilina foi de 60%, para ciprofloxacina 25% e para tetraciclina 45%, enquanto nos tratadores de subsistência foram de 20%, 5% e 30%, respectivamente. Isolados de E. coli de frangos em criação de subsistência apresentaram 46,6%(28/60) de suscetibilidade a todos os antimicrobianos testados enquanto que na criação intensiva 81%(49/60) foram multirresistentes. Sete clusters de isolados de E. coli de frangos de diferentes aviários apresentaram similaridade acima de 80%, e dois destes foram superiores a 95%. Três clusters de isolados de frangos e de tratadores apresentaram similaridade superior a 80%. Somente um destes clusters foi de isolado de tratador e de frango do mesmo aviário.

Occurrence of avian pathogenic Escherichia coli and antimicrobial-resistant E. coli in red-legged partridges (Alectoris rufa): sanitary concerns of farming

Red-legged partridges (Alectoris rufa) are a significant part of the culture, diet and income for many people in central and southern Spain. Due to declining populations in the wild, intensive farming is common and 4 million juvenile partridges are released each autumn. Intensive management and high densities result in high prevalence of enteric disease and the use of antimicrobials as preventive measures on partridge farms and prior to restocking in the wild. We determined the occurrence of avian pathogenic Escherichia coli (APEC), and screened phenotypic resistance of E. coli against enrofloxacin, gentamicin and cefotaxim in farmed, restocked and wild partridges. Prevalence of APEC in farmed and restocked red-legged partridges was significantly higher than in natural populations. Phenotypic resistance against both gentamicin and enrofloxacin was significantly more frequent in farmed (75%) and restocked (43%) partridges than in wild partridges, while most E. coli isolated from natural populations were susceptible to all three antimicrobials tested (65%). This indicates that farmed and restocked partridges carry APEC that could be a reason for disease outbreaks on farms, and that E. coli carried by farmed and restocked partridges can acquire resistance to frequently used antimicrobials, thus being a concern for the environment, wild birds and consumers. Management in farms and restocking procedures may create a hazard not only for spreading APEC, but also as a potential source of resistant E. coli in the environment.

Escherichia coli isolates from sick chickens in China: changes in antimicrobial resistance between 1993 and 2013

The use of antimicrobials for the control of infectious disease has increased in recent decades. Understanding trends in antimicrobial resistance provides clues about the relationship between antimicrobial use and the emergence of resistance. We examined the resistance of 540 Escherichia coli isolates to 19 antimicrobials that represent 11 classes of antimicrobial agents. The isolates were collected from chickens between 1993 and 2013 in China. Overall, >96.7% of the isolates were resistant to at least one of the tested compounds, and 87.2% of them displayed multidrug resistance (MDR) representing five to six antimicrobial classes. A high proportion of E. coli isolates were resistant to tetracycline (90.6%), nalidixic acid (80.6%), ampicillin (77.2%), trimethoprim-sulfamethoxazole (76.9%), and streptomycin (72.8%). Only 3.0% of the isolates were resistant to nitrofurantoin, and none was resistant to meropenem. Resistance to amikacin, ampicillin, aztreonam, ceftazidime, cefotaxime, cephalothin, chloramphenicol, ciprofloxacin, fosfomycin, levofloxacin, norfloxacin, nalidixic acid, piperacillin, and trimethoprim-sulfamethoxazole significantly increased from 1993 to 2013 (P <0.01). There was an increasing trend in MDR over the 20 year period.

Genotypes and pathogenicity of cellulitis isolates reveal traits that modulate APEC virulence

We characterized 144 Escherichia coli isolates from severe cellulitis lesions in broiler chickens from South Brazil. Analysis of susceptibility to 15 antimicrobials revealed frequencies of resistance of less than 30% for most antimicrobials except tetracycline (70%) and sulphonamides (60%). The genotyping of 34 virulence-associated genes revealed that all the isolates harbored virulence factors related to adhesion, iron acquisition and serum resistance, which are characteristic of the avian pathogenic E. coli (APEC) pathotype. ColV plasmid-associated genes (cvi/cva, iroN, iss, iucD, sitD, traT, tsh) were especially frequent among the isolates (from 66.6% to 89.6%). According to the Clermont method of ECOR phylogenetic typing, isolates belonged to group D (47.2%), to group A (27.8%), to group B2 (17.4%) and to group B1 (7.6%); the group B2 isolates contained the highest number of virulence-associated genes. Clonal relationship analysis using the ARDRA method revealed a similarity level of 57% or higher among isolates, but no endemic clone. The virulence of the isolates was confirmed in vivo in one-day-old chicks. Most isolates (72.9%) killed all infected chicks within 7 days, and 65 isolates (38.1%) killed most of them within 24 hours. In order to analyze differences in virulence among the APEC isolates, we created a pathogenicity score by combining the times of death with the clinical symptoms noted. By looking for significant associations between the presence of virulence-associated genes and the pathogenicity score, we found that the presence of genes for invasins ibeA and gimB and for group II capsule KpsMTII increased virulence, while the presence of pic decreased virulence. The fact that ibeA, gimB and KpsMTII are characteristic of neonatal meningitis E. coli (NMEC) suggests that genes of NMEC in APEC increase virulence of strains.

Antimicrobial resistance of Escherichia coli isolated from chickens with colibacillosis in and around Harare, Zimbabwe

Colibacillosis, a disease caused by avian pathogenic Escherichia coli (APEC), can lead to great economic losses in the poultry industry. The aim of this study was to determine the prevalence of antibiotic resistance and antibiotic resistance patterns in APEC in Zimbabwe. From 503 chickens diagnosed with colibacillosis, 103 E. coli isolates were obtained. Isolation and identification of E. coli were carried out using microscopy and biochemical tests. The disc diffusion method was used to determine antibiotic susceptibility of the isolates to 8 commercial antibiotics. Many isolates exhibited resistance to more than one antibiotic. Antibiogram profiles indicated maximum resistance to tetracycline (100%), bacitracin (100%), and cloxacillin (100%) and a high prevalence of resistance to ampicillin (94.1%). However; there were high prevalences of sensitivity to ciprofloxacin (100%) and gentamycin (97.1%). The isolates showed moderate rates of sensitivity to chloramphenicol and neomycin. All isolates in this study showed multidrug resistance because they were all resistant to 3 or more antibiotics. Seven multidrug resistance patterns were observed. The most common pattern (resistance to ampicillin, bacitracin, cloxacillin, and tetracycline) was exhibited by 30 isolates. Our findings show that there is emerging drug resistance in APEC associated with colibacillosis in Zimbabwe. The observed high level of multidrug resistance could hamper the treatment of colibacillosis in Zimbabwe.

Antibiotic use in animal feed and its impact on human healt

Antibiotic resistance in bacteria that cause disease in man is an issue of major concern. Although misuse of antibiotics in human medicine is the principal cause of the problem, antibiotic-resistant bacteria originating in animals are contributory factors, with some types of resistance in some species of bacteria. Antibiotics are added to animal feeds to treat and prevent infections and to improve growth and production. Until recently, the major concerns about incorporation of antibiotics in animal feeds related to antibiotic residues in products from treated animals. Although, in 1969, the Swann (1969) report drew attention to the potential for antibiotic-resistant bacteria to spread from treated animals via the food chain, there was little response until the detection of vancomycin-resistant enterococci in animals fed a related glycopeptide, avoparcin. Subsequently, attention started to focus on the issue and other examples of transfer of resistant bacteria through the food chain, such as enterococci resistant to quinupristin-dalfopristin or to everninomicin, fluoroquinolone-resistant campylobacters and multiresistant Escherichia coli, and salmonella such as Salmonella typhimurium DT104. Reviews and committees in many countries have highlighted the need for better control of licensing of antibiotics, and codes for prudent use of antibiotics by veterinary practitioners and farmers. The continued use of antibiotic growth promoters has been questioned and there is a need to ensure that antibiotics important in human medicine are not used therapeutically or prophylactically in animals.

Resistência antimicrobiana e perfil plasmidial de Escherichia coli isolada de frangos de corte e poedeiras comerciais no Estado de Pernambuco

Embora existam linhagens de Escherichia coli não patogênicas para aves, muitas outras possuem a capacidade de causar sérios danos à saúde das mesmas, sendo capazes de ocasionar diferentes tipos de processos infecciosos. As linhagens patogênicas são denominadas Avian Pathogenic Escherichia coli (APEC), possuindo genes relacionados ao processo de patogênese em epissomos (plasmídios) ou no cromossomo. A presença de plasmídios, contendo genes de resistência a antibióticos em linhagens aviárias, patogênicas ou não, indicam a possibilidade de transferência gênica lateral entre diferentes tipos de linhagens facilitando também a transferência de genes de patogenicidade ou virulência. Objetivou-se com este estudo avaliar o perfil de sensibilidade a antibióticos (13) de diferentes amostras (35) de E. coli isoladas de aves comerciais do Estado de Pernambuco apresentando, ou não, sinais clínicos de processos infecciosos e correlacionar esta resistência com a presença de plasmídios. Os testes utilizados demonstraram que 94,28% dos isolados foram resistentes a três ou mais antibióticos, com a lincomicina apresentando o maior percentual de resistência (100%). Na Concentração Inibitória Mínima (CIM) observou-se multirresistência a vários antimicrobianos. A presença de plasmídios foi detecada em 80,0% (28/35) dos isolados, com 16 isolados apresentando plasmídios com peso molecular aproximado de 88 MDa. Também foi verificada a presença de linhagens apresentando plasmídios de vários tamanhos. Concluiu-se que isolados de E. coli resistentes a antimicrobianos utilizados na avicultura estão presentes no Estado de Pernambuco, tanto em frangos de corte quanto em poedeiras comerciais. A presença de plasmídios detectados na maioria dos isolados pode estar associada à resistência aos antimicrobianos e sugere a presença de possíveis genes relacionados à patogenicidade. Monitorar a resistência a antibióticos em bactérias isoladas de animais torna-se um fator determinante para eleição e êxito do tratamento, bem como a possibilidade de eliminação daquelas que possuem plasmídios para se evitar a transferência de genes relacionados à patogenicidade.

Molecular analysis of ciprofloxacin resistance and clonal relatedness of clinical Escherichia coli isolates from haematology patients receiving ciprofloxacin prophylaxis

OBJECTIVES

Widespread use of fluoroquinolones has led to increased levels of resistance in clinical isolates of Escherichia coli. We investigated the evolution of ciprofloxacin susceptibility and molecular epidemiology of clinical E. coli isolates in haematology patients receiving ciprofloxacin prophylaxis on the population and individual patient level.

METHODS

From August 2006 through December 2007 we collected all E. coli isolates (n = 404) from surveillance and infection-site cultures from 169 haematology patients receiving ciprofloxacin prophylaxis. Analysis of the gyrase A (gyrA) gene was performed by denaturing gradient gel electrophoresis (DGGE) in 364 isolates and clonal relatedness was determined by the single-enzyme amplified fragment length polymorphism (seAFLP) technique in 162 isolates. One hundred of these isolates were also subjected to qnrA analysis.

RESULTS

The average number of samples per patient was 2.4 (maximum 20) and 122 (30%) of 404 E. coli isolates were resistant to ciprofloxacin. In 124 patients only ciprofloxacin-susceptible strains were detected. DGGE revealed 11 different gyrA sequence patterns and, based on AFLP analysis, there was evidence of selection of ciprofloxacin-resistant strains under antibiotic pressure, as well as the occurrence of genetically indistinguishable ciprofloxacin-resistant and -susceptible E. coli isolates within one patient. Clonal dissemination of ciprofloxacin-resistant E. coli was observed, but did not predominate.

CONCLUSIONS

The genetic evolution of clinical E. coli isolates in haematology patients receiving ciprofloxacin prophylaxis is characterized by selection of ciprofloxacin-resistant strains. However, we did find evidence for de novo resistance mutation in ciprofloxacin-susceptible E. coli in individual patients under selective pressure.

Antimicrobial resistance, integrons and plasmid replicon typing in multiresistant clinical Escherichia coli strains from Enugu State, Nigeria

Eleven multiresistant Escherichia coli strains of animal and human origin were assayed for the presence of antimicrobial resistance genes, integrons and associated gene cassettes, as well as plasmid content. Ciprofloxacin-resistant strains were screened for amino acid changes in GyrA and ParC proteins. The E. coli strains were found to harbor a variety of genes including cmlA, aac (3)-II, aac (3)-IV, aadA, strA-strB, tet (A), tet (B), bla(TEM), sul1, sul2 and sul3. Four of the eight int I1-positive strains were also positive for qacE Δ1 -sul1 region and the following gene cassettes were detected: dfrA7, dfrA12 + orfF + aadA2 and bla(OXA1)+ aadA1. Five strains contained class 1 integrons lacking the qacE Δ1 -sul1 region and they showed a single type of gene cassette arrangement (estX + psp + aadA2 + cmlA + aadA1 + qacH + IS440 + sul3). The two int I2-positive strains carried the same type of gene cassette arrangement (dfrA1 + sat + aadA1). The seven ciprofloxacin-resistant E. coli strains exhibited a Ser-83-Leu substitution in GyrA protein and a Ser-80-Ile substitution in ParC protein; six of these strains presented an additional substitution in GyrA (Asp-87-Gly or Asp-87-Asn) and one strain in ParC (Glu-84-Gly). Eight different plasmid-replicon-types were detected among the 11 E. coli strains, IncF being the most frequent one detected, found in nine strains; other plasmid replicon types detected were IncX, IncI1, IncY, IncW, IncFIC, IncB/O, and IncK. Antimicrobial resistance in the E. coli strains studied was mediated by a variety of genes, some of them included in integrons, as well as by mutations gyr A and par C genes.

[Epidemiological study of Klebsiella spp. uropathogenic strains producing extended-spectrum β-lactamase in a Tunisian university hospital, 2009]

OBJECTIVE

An update on the prevalence of antibiotic resistance in extended-spectrum β-lactamase among urinary strains of Klebsiella spp. isolated from in-come and out-come patients at University Hospital, Mahdia (Tunisia).

PATIENTS AND METHODS

A retrospective survey was made over a period of twelve months (year 2009). It focused on 3564 patients with urinary tract infection confirmed by the Laboratory of Microbiology in the University Hospital, Mahdia.

RESULTS

Klebsiella spp. was involved in 5.5% (198/3564) of all cases of urinary tract infections identified. Klebsiella pneumoniae accounted for 94.9% of all Klebsiella (5.1% for Klebsiella oxytoca). The frequency of Klebsiella spp. resistance to fluoroquinolones was 19.2% and to third generation cephalosporins was 22.7%. Forty strains of Klebsiella spp. producing extended-spectrum β-lactamase witch corresponds to 20.2% of all the Klebsiella. The extended-spectrum β-lactamase strains with resistance to fluoroquinolones were 67.5% (27/40) or 13.6% of all klebsiella (27/198). No strain was resistant to imipenem. The 27 strains multiresistant (ESBL+FQ resistance) are likely to be carriers of plasmids encoding the ESBL and resistance to fluoroquinolones.

CONCLUSION

the resistance of Enterobacteriaceae, including Klebsiella spp, to fluoroquinolones has become a concern both in hospital in community medicine. The advent of this resistance mechanism involves a more rational use of fluoroquinolones, especially as first-line treatment of urinary tract infections.

SUSCEPTIBILIDADE ANTIMICROBIANA DE AMOSTRAS DE ESCHERICHIA COLI ISOLADAS DE FRANGO INDUSTRIAL (GALLUS GALLUS DOMESTICUS - LINNAEUS, 1758) COM COLIBACILOSE

RESUMO O presente estudo avaliou a susceptibilidade de amostras de Escherichia coli isoladas de quadros de colissepticemia aviária da região centro-oeste paulista pelo Laboratório de Ornitopatologia da FMVZ-UNESP/Botucatu, SP. Constatou-se um grande número de amostras multirresistentes aos antibióticos testados, onde as drogas menos efetivas foram sulfonamida e tetraciclina. Todas as amostras mostraram-se sensíveis a norfloxacina e gentamicina.

Occurrence and characteristics of class 1 and class 2 integrons in resistant Escherichia coli isolates from animals and farm workers in northeastern China

The purpose of this study was to investigate the incidence of class 1 and class 2 integrons and the presence of the gene cassettes in resistant Escherichia coli isolates from farm animals and farm workers in northeastern China during 2004-2007. Most of E. coli isolates from farm worker and animal were multiresistant and showed a high resistance to aminoglycosides, chloramphenicol, amoxicillin, doxycyline, sulfanilamide, and quinolones. Integrons were found in 57.1% of the resistant E. coli isolates from animals and farm workers. Integrase genes were detected in 58.7% (101/172), 60.4% (64/106), and 26.1% (6/23) of resistant E. coli isolates from swine, chickens, and farm workers, respectively. Class 2 integrons were detected only in resistant E. coli isolates from chickens and have one array cassette of dfrA1- sat1- aadA1- orfX. Dfr17- aadA5 was the most prevalent in resistant E. coli isolates from farm workers, swine, and chickens. Conjugative experiments demonstrated horizontal transfer of class 1 and class 2 integrons between isolates of farm worker and animals. Our data revealed that multidrug resistance and class 1 integrons were widely present in E. coli isolates obtained in northeastern China. The horizontal transfer of integrons by conjugation seems to contribute to the wide dissemination of antimicrobial resistance in E. coli isolates of human and animal origins.

Avian colibacillosis and salmonellosis: a closer look at epidemiology, pathogenesis, diagnosis, control and public health concerns

Avian colibacillosis and salmonellosis are considered to be the major bacterial diseases in the poultry industry world-wide. Colibacillosis and salmonellosis are the most common avian diseases that are communicable to humans. This article provides the vital information on the epidemiology, pathogenesis, diagnosis, control and public health concerns of avian colibacillosis and salmonellosis. A better understanding of the information addressed in this review article will assist the poultry researchers and the poultry industry in continuing to make progress in reducing and eliminating avian colibacillosis and salmonellosis from the poultry flocks, thereby reducing potential hazards to the public health posed by these bacterial diseases.

Occurrence and characteristics of class 1 and class 2 integrons in resistant Escherichia coli isolates from animals and farm workers in northeastern China

The purpose of this study was to investigate the incidence of class 1 and class 2 integrons and the presence of gene cassettes in resistant Escherichia coli isolates from farm animals and farm workers in northeastern China during 2004-2007. Most of the E. coli isolates from the farm workers and animals were mutiresistant and showed high resistance to aminoglycosides, chloramphenicol, amoxicillin, sulfanilamide, and quinolones. Integrons were found in 56.8% of the resistant E. coli isolates from the animals and farm workers. Integrase genes were detected in 58.7% (101/172), 60.4% (64/106), and 26.1% (6/23) of resistant E. coli isolates from the swine, chickens, and farm workers, respectively. Class 2 integrons were detected only in resistant E. coli isolates from the chickens and have one array cassette of dfrA1-sat1- aadA1- orfX. Dfr17- aadA5 was the most prevalent in resistant E. coli isolates from the farm workers, swine, and chickens. Conjugative experiments demonstrated horizontal transfer of class 1 and class 2 integrons between isolates of farm worker and animals. Our data revealed that multidrug resistance and class 1 integrons were widely present in E. coli isolates obtained in northeastern China. The horizontal transfer of integrons by conjugation seems to contribute to the wide dissemination of antimicrobial resistance in E. coli isolates of human and animal origin.

Causative agents and antimicrobial susceptibilities of urinary tract infections in the northwest of Iran

BACKGROUND

The empirical therapy of urinary tract infections (UTI) relies on the predictability of the agents causing UTI and knowledge of their antimicrobial susceptibility patterns.

METHODS

In a prospective study undertaken over a 14-month period, 5136 samples from patients suspected of having a UTI were analyzed, of which 676 were culture-positive. Isolated bacteria were identified by standard tests, and antibiotic susceptibility was determined by disk diffusion method.

RESULTS

According to our results, Escherichia coli was the most common etiological agent of UTI (74.6%), followed by Klebsiella spp (11.7%), Staphylococcus saprophyticus (6.4%), and Pseudomonas aeruginosa (2.2%). Analysis of the frequency of isolated bacteria according to the age of the patients revealed that Klebsiella infections are more prevalent in the older age groups (>10 years) and Pseudomonas infections are more prevalent in children and the elderly (<9 years and >60 years). Results of antimicrobial susceptibility analysis for E. coli, as the most prevalent cause of UTI, to commonly used antibiotics are as follows: amikacin (97.8%), gentamicin (97%), ciprofloxacin (94%), nitrofurantoin (87.1%), nalidixic acid (93.7%), trimethoprim-sulfamethoxazole (48.2%), cephalexin (76%), and ampicillin (6.9%).

CONCLUSIONS

The results show that the antimicrobial resistance patterns of the causes of UTI are highly variable and continuous surveillance of trends in resistance patterns of uropathogens is important.

Antibiotic resistance of commensal Escherichia coli of food-producing animals from three Vojvodinian farms, Serbia

Commensal bacteria of food-producing animals are considered an important reservoir of antibiotic resistance. The aim of this study was to determine the current prevalence of resistance to 18 different antibiotics in animal commensal Escherichia coli isolated from food-producing animals from three different farms with specific modes of antimicrobial use. A very high prevalence of resistance was found to tetracycline, a moderate level to streptomycin, ampicillin, cefalothin and nalidixic acid and a low of resistance to the other tested antibiotics. Resistance to two or more antibiotics was observed among all swine E. coli, 63.2% of broiler isolates and 37.5% of cattle isolates. The results show that commensals of food-producing animals from Vojvodina region are important reservoirs of resistance to older-generation antibiotics.

Antimicrobial susceptibility and molecular detection of chloramphenicol and florfenicol resistance among Escherichia coli isolates from diseased chickens

Seventy Escherichia coli isolates recovered from diseased chickens diagnosed with colibacillosis in Henan Province, China, between 2004 and 2005 were characterized for antimicrobial susceptibility profiles via a broth doubling dilution method. Overall, the isolates displayed resistance to trimethoprim-sulfamethoxazole (100%), oxytetracycline (100%), ampicillin (83%), enrofloxacin (83%), and ciprofloxacin (81%), respectively. Among the phenicols, resistance was approximately 79% and 29% for chloramphenicol and florfenicol, respectively. Molecular detection revealed that the incidence rates of the floR, cmlA, cat1, cat2 and cat3 were 29, 31, 16, 13, and 0%, respectively. Additionally, 10% of the isolates were positive for both floR and cmlA. As these antimicrobial agents may potentially induce cross-resistance between animal and human bacterial pathogens, their prudent use in veterinary medicine is highly recommended.

Chronological study of antibiotic resistances and their relevant genes in Korean avian pathogenic Escherichia coli isolates

Antibiograms and relevant genotypes of Korean avian pathogenic Escherichia coli (APEC) isolates (n = 101) recovered between 1985 and 2005 were assessed via disc diffusion test, PCR, restriction enzyme analysis, and sequencing. These isolates were highly resistant to tetracycline (84.2%), streptomycin (84.2%), enrofloxacin (71.3%), and ampicillin (67.3%), and most of the tetracycline, streptomycin, enrofloxacin, and ampicillin resistances were associated with tetA and/or tetB, aadA and/or strA-strB, mutations in gyrA and/or parC, and TEM, respectively. Class 1 integrons were detected in 40 isolates (39.6%), and a variety of gene cassettes conferring streptomycin (aadA), gentamicin (aadB), and trimethoprim (dfr) resistances were identified: aadA1a (27.5%), dfrV-orfD (2.5%), aadB-aadA1a (2.5%), dfrI-aadA1a (47.5%), dfrXVII-aadA5 (12.5%), and dfrXII-orfF-aadA2 (7.5%). In addition, several types of common promoters (P(ant)) of the gene cassettes (hybrid P1, weak P1, or weak P1 plus P2) and single-nucleotide polymorphisms in aadA1a were identified. The results of a chronological analysis demonstrated significant and continuous increases in the frequencies of resistances to several antibiotics (tetracycline, streptomycin, enrofloxacin, ampicillin, and trimethoprim-sulfamethoxazole) and of the relevant resistance genes (tetA, strA-strB, and TEM), mutations in gyrA and parC, and multidrug-resistant APEC strains during the period 2000 to 2005.

Antibiotic resistance and virulence genes in commensal Escherichia coli and Salmonella isolates from commercial broiler chicken farms

Antibiotic resistance patterns and the presence of antibiotic and virulence determinants in 74 sorbitol-negative Escherichia coli and 62 Salmonella isolates from nine different broiler chicken farms were investigated. Each farm was supplied by one of three companies that used different antimicrobial agents in feed for growth promotion. The isolates were identified by API 20E for E. coli and by serological tests for Salmonella. The susceptibility of the isolates to antibiotics was determined by Sensititre using the Clinical and Laboratory Standards Institute's breakpoints. Fifty-two E. coli isolates (70.3%) and nine Salmonella isolates (14.52%) were multiresistant to at least nine antibiotics. The multiresistant isolates were evaluated for the presence of tetracycline resistance, integron class 1, and blacMY 2 genes by PCR. Of the 74 E. coli isolates, 55 were resistant to amoxicillin and ceftiofur. Among these 55 resistant E. coli isolates, 45 (81.8%) and 22 (40.0%) were positive for blacMY-2 and qacEdeltal-Sull genes, respectively. Tetracycline resistance was found in 56 isolates (75.8%) among which 12 (21.4%) and 24 (42.9%) gave positive results for tetA and tetB, respectively. Virulence genes (iss, tsh, and traT), aerobactin operon (iucC), and the eaeA gene were detected in some E. coli strains. Among the 27 amoxicillin- and ceftiofur-resistant Salmonella isolates, the blacMY-2 gene was detected in 22 isolates. The class 1 integron gene (qacEdeltal-Sull) was not detected in any Salmonella isolates, whereas the invasin (inv) and virulence (spy) genes were found in 61 (98.4%) and 26 (42%) of the Salmonella isolates, respectively. This study indicated that multiple antibiotic-resistant commensal E. coli and Salmonella strains carrying virulence genes can be found on commercial broiler chicken farms and may provide a reservoir for these genes in chicken production facilities. Except for the presence of tetB, there was no significant effect of feed formulations on the phenotypic or genotypic characteristics of the isolates.

Genetics of antimicrobial resistance

Antimicrobial resistant strains of bacteria are an increasing threat to animal and human health. Resistance mechanisms to circumvent the toxic action of antimicrobials have been identified and described for all known antimicrobials currently available for clinical use in human and veterinary medicine. Acquired bacterial antibiotic resistance can result from the mutation of normal cellular genes, the acquisition of foreign resistance genes, or a combination of these two mechanisms. The most common resistance mechanisms employed by bacteria include enzymatic degradation or alteration of the antimicrobial, mutation in the antimicrobial target site, decreased cell wall permeability to antimicrobials, and active efflux of the antimicrobial across the cell membrane. The spread of mobile genetic elements such as plasmids, transposons, and integrons has greatly contributed to the rapid dissemination of antimicrobial resistance among several bacterial genera of human and veterinary importance. Antimicrobial resistance genes have been shown to accumulate on mobile elements, leading to a situation where multidrug resistance phenotypes can be transferred to a susceptible recipient via a single genetic event. The increasing prevalence of antimicrobial resistant bacterial pathogens has severe implications for the future treatment and prevention of infectious diseases in both animals and humans. The versatility with which bacteria adapt to their environment and exchange DNA between different genera highlights the need to implement effective antimicrobial stewardship and infection control programs in both human and veterinary medicine.

Class 1 integrons and their conjugal transfer with and without virulence-associated genes in extra-intestinal and intestinal Escherichia coli of poultry

Multiple-drug resistance in enteric bacteria is frequently associated with integrons. To determine whether integrons may play a role in avian pathogenic Escherichia coli, isolates of extra-intestinal (n = 27) and intestinal (n = 40) E. coli from dead chicks and turkey poults were analysed for the presence of class 1 integrons and of the virulence-associated genes iss, tsh and colV. Eleven extra-intestinal strains possessed a 1.0 kb class 1 integron with a variable region of aadA1 and were resistant to tetracycline. These traits were indicative of the presence of the Tn21 transposon, which was confirmed by polymerase chain reaction. All extra-intestinal strains had the colV, iss and tsh genes, but none of these genes were cotransferred with the 1.0 kb integron when conjugal transferability was tested. The integron content of the intestinal strains showed considerable variability: one or two of four different class 1 integrons, which varied from 1.0 to 2.4 kb in size, were detected in the 11 strains. The aadA7 gene of the 1.0 kb integron, the dfrA1-aadA1 genes of the 1.6 kb integron and the folA-catB3-aadA5 genes of the 2.4 kb integron were identical to those described by other workers. However, the orfIN682-dhfrV-orfD gene cassette arrangement of the 1.5 kb integron of an intestinal strain of serogroup O5 had no similarity to any previously reported integrons. Conjugal transfer of the 1.6 and 2.4 kb integrons was successful, and in a serogroup O33 intestinal E. coli strain the iss gene was apparently cotransferred with a 1.6 kb integron. The 1.0 and 1.5 kb integrons were not transferable. Our data suggest that intestinal E. coli strains of poultry may be a reservoir for emerging multiresistant strains of avian pathogenic E. coli.

Vertical transmission of a fluoroquinolone-resistant Escherichia coli within an integrated broiler operation

The epidemiology of an enrofloxacin-resistant Escherichia coli clone was investigated during two separate outbreaks of colibacillosis in the Danish broiler production. In total five flocks were reported affected by the outbreaks. Recorded first-week mortalities were in the range of 1.7-12.7%. The clone was first isolated from dead broilers and subsequently demonstrated in samples from associated hatchers and the parent flock with its embryonated eggs, suggesting a vertical transmission from the parents. The second outbreak involved two broiler flocks unrelated to the affected flocks from the first outbreak. However, the clone could not be demonstrated in the associated parent flock. Furthermore, samplings from grand-parent flocks were negative for the outbreak clone. The clonality was evaluated by plasmid profiling and pulsed-field gel electrophoresis. None of the recognized virulence factors were demonstrated in the outbreak clone by microarray and PCR assay. The molecular background for the fluoroquinolone-resistance was investigated and point mutations in gyrA and parC leading to amino-acid substitutions in quinolone-resistance determining regions of GyrA and ParC were demonstrated. Vertical transmission of enrofloxacin-resistant E. coli from healthy parents resulting in high first-week mortality in the offspring illustrates the potential of the emergence and spreading of fluoroquinolone-resistant bacteria in animal husbandry, even though the use of fluoroquinolones is restricted.

Antimicrobial resistance of Shiga toxin (verotoxin)-producing Escherichia coli O157:H7 and non-O157 strains isolated from humans, cattle, sheep and food in Spain

A total of 722 Shiga toxin-producing Escherichia coli (STEC) isolates recovered from humans, cattle, ovines and food during the period from 1992 to 1999 in Spain were examined to determine antimicrobial resistance profiles and their association with serotypes, phage types and virulence genes. Fifty-eight (41%) out of 141 STEC O157:H7 strains and 240 (41%) out of 581 non-O157 STEC strains showed resistance to at least one of the 26 antimicrobial agents tested. STEC O157:H7 showed a higher percentage of resistant strains recovered from bovine (53%) and beef meat (57%) than from human (23%) and ovine (20%) sources, whereas the highest prevalence of antimicrobial resistance in non-O157 STEC was found among isolates recovered from beef meat (55%) and human patients (47%). Sulfisoxazole (36%) had the most common antimicrobial resistance, followed by tetracycline (32%), streptomycin (29%), ampicillin (10%), trimethoprim (8%), cotrimoxazole (8%), chloramphenicol (7%), kanamycin (7%), piperacillin (6%), and neomycin (5%). The multiple resistance pattern most often observed was that of streptomycin, sulfisoxazole, and tetracycline. Ten (7%) STEC O157:H7 and 71 (12%) non-O157 strains were resistant to five or more antimicrobial agents. Most strains showing resistance to five or more antimicrobial agents belonged to serotypes O4:H4 (4 strains), O8:H21 (3 strains), O20:H19 (6 strains), O26:H11 (8 strains eae-beta1), O111:H- (3 strains eae-gamma2), O118:H- (2 strains eae-beta1), O118:H16 (5 strains eae-beta1), O128:H- (2 strains), O145:H8 or O145:H- (2 strains eae-gamma1), O157:H7 (10 strains eae-gamma1), O171:H25 (3 strains), O177:H11 (5 strains eae-beta1), ONT:H- (3 strains/1 eae-beta1) and ONT:H21 (2 strains). Interestingly, most of these serotypes, i.e., those indicated in bold) were found among human STEC strains isolated from patients with hemolytic uremic-syndrome (HUS) reported in previous studies. We also detected, among non-O157 strains, an association between a higher level of multiple resistance to antibiotics and the presence of the virulence genes eae and stx(1). Moreover, STEC O157:H7, showed an association between certain phage types, PT21/28 (90%), PT23 (75%), PT34 (75%), and PT2 (54%), with a higher number of resistant strains. We conclude that the high prevalence of antimicrobial resistance detected in our study is a source of concern, and cautious use of antibiotics in animals is highly recommended.

Emergence of plasmid-mediated resistance to quinolones in Enterobacteriaceae

Although quinolone resistance results mostly from chromosomal mutations in Enterobacteriaceae, it may also be mediated by plasmid-encoded Qnr determinants. Qnr proteins protect DNA from quinolone binding and compromise the efficacy of quinolones such as nalidixic acid. Qnr proteins (QnrA-like, QnrB and QnrS) have been identified worldwide with a quite high prevalence among Asian isolates with a frequent association with clavulanic acid inhibited expanded-spectrum beta-lactamases and plasmid-mediated cephalosporinases. The qnrA genes are embedded in complex sul1-type integrons. A very recent identification of the origin of QnrA determinants in the water-borne species Shewanella algae underlines the role of the environment as a reservoir for this emerging threat. It may help to determine the location of in vivo transfer of qnrA genes. Further analysis of the role (if any) of quinolones for enhancing this gene transfer may be conducted. This could prevent the spread, if still possible, of this novel antibiotic resistance mechanism.

Patterns of antimicrobial resistance observed in Escherichia coli isolates obtained from domestic- and wild-animal fecal samples, human septage, and surface water

A repeated cross-sectional study was conducted to determine the patterns of antimicrobial resistance in 1,286 Escherichia coli strains isolated from human septage, wildlife, domestic animals, farm environments, and surface water in the Red Cedar watershed in Michigan. Isolation and identification of E. coli were done by using enrichment media, selective media, and biochemical tests. Antimicrobial susceptibility testing by the disk diffusion method was conducted for neomycin, gentamicin, streptomycin, chloramphenicol, ofloxacin, trimethoprim-sulfamethoxazole, tetracycline, ampicillin, nalidixic acid, nitrofurantoin, cephalothin, and sulfisoxazole. Resistance to at least one antimicrobial agent was demonstrated in isolates from livestock, companion animals, human septage, wildlife, and surface water. In general, E. coli isolates from domestic species showed resistance to the largest number of antimicrobial agents compared to isolates from human septage, wildlife, and surface water. The agents to which resistance was demonstrated most frequently were tetracycline, cephalothin, sulfisoxazole, and streptomycin. There were similarities in the patterns of resistance in fecal samples and farm environment samples by animal, and the levels of cephalothin-resistant isolates were higher in farm environment samples than in fecal samples. Multidrug resistance was seen in a variety of sources, and the highest levels of multidrug-resistant E. coli were observed for swine fecal samples. The fact that water sample isolates were resistant only to cephalothin may suggest that the resistance patterns for farm environment samples may be more representative of the risk of contamination of surface waters with antimicrobial agent-resistant bacteria.

Antimicrobial susceptibility and molecular characterization of avian pathogenic Escherichia coli isolates

Ninety-five avian pathogenic Escherichia coli (APEC) isolates recovered from diagnosed cases of avian colibacillosis from North Georgia between 1996 and 2000 were serotyped and examined for typical virulence-factors, susceptibility to antimicrobials of human and veterinary significance, and genetic relatedness. Twenty different serotypes were identified, with O78 being the most common (12%). The majority of the avian E. coli isolates (60%), however, were non-typeable with standard O antisera. Eighty-four percent of isolates were PCR positive for the temperature-sensitive hemagglutinin (tsh) gene and 86% positive for the increased serum survival (iss) gene. Multiple antimicrobial-resistant phenotypes (> or =3 antimicrobials) were observed in 92% of E. coli isolates, with the majority of isolates displaying resistance to sulfamethoxazole (93%), tetracycline (87%), streptomycin (86%), gentamicin (69%), and nalidixic acid (59%). Fifty-six E. coli isolates displaying resistance to nalidixic acid were co-resistant to difloxacin (57%), enrofloxacin (16%), gatifloxacin (2%), and levofloxacin (2%). DNA sequencing revealed point mutations in gyrA (Ser83-Leu, Asp87-Tyr, Asp87-Gly, Asp87-Ala), gyrB (Glu466-Asp, Asp426-Thr), and parC (Ser80-Ile, Ser80-Arg). No mutations were observed in parE. Twelve of the quinolone-resistant E. coli isolates were tolerant to cyclohexane, a marker for upregulation of the acrAB multi-drug resistance efflux pump. Quinolone-resistant isolates were further genetically characterized via ribotyping. Twenty-two distinct ribogroups were identified, with 61% of isolates clustering into four major ribogroups, indicating that quinolone resistance has emerged among multiple avian pathogenic E. coli serogroups and chromosomal backgrounds.

Isolation and molecular characterization of fluoroquinolone-resistant Escherichia coli from poultry litter

Nineteen fluoroquinolone-resistant Escherichia coli strains were isolated from poultry litter. Sixteen of the 19 strains were serotyped to groups 6, 8, 53, 56, 153, and 174. Three strains were not serotyped to any known group. All isolates were resistant to multiple antibiotics. Most strains were resistant to gentamicin, kanamycin, chloramphenicol, and streptomycin. Ribotyping of the multidrug-resistant isolates with restriction enzyme PvuII showed 5 different ribogroups, suggesting independent development of resistance instead of clonal spread. Quinolone resistance was associated with mutations of the quinolone resistance-determining region (QRDR) of the gyr A gene in all cases. To determine the incidence of gyr A mutations in fluoroquinolone-resistant E. coli isolates, a rapid PCR-based assay was used by amplifying a 164-bp region of the gyr A gene containing the mutation sites followed by digestion of the PCR product with restriction enzyme HinfI. A higher level of resistance to ciprofloxacin [minimum inhibitory concentration (MIC) >4 microg] was associated with double mutations, but the mutants with a low level of resistance (MIC <2 microg) had only a single mutation. Those strains that were ciprofloxacin-resistant (MIC <2 microg) had a single mutation of a C-to-T transition at position 248 (Ser 83-->Leu) or a G-to-A transition at position 259 (Asp 87-->Asn). The ciprofloxacin-resistant (MIC >4 microg) isolates had mutations at both positions. Fluoroquinolone resistance was present among different serotypes and ribotypes, and drug resistance profiles suggest that the incidence of resistance does not indicate a clonal population in avian E. coli.