Antimicrobial resistance of Escherichia coli isolated from chickens

Aquatic environments polluted with antibiotics and heavy metals: a human health hazard

Aquatic environments often receive wastewater containing pollutants such as antibiotics and heavy metals from hospital sewage, as well as contaminants from soil. The presence of these pollutants can increase the rate of exchange of resistant genes between environmental and pathogenic bacteria, which can make the treatment of various types of bacterial infections in humans and animals difficult, in addition to causing environmental problems such as ecological risk. In this study, two tetracycline-resistant Pseudomonas aeruginosa (EW32 and EW33), isolated from aquatic environments close to industries and a hospital in southeastern Brazil, were investigated regarding the possible association between tetracycline and heavy metal resistance. The isolate EW32 presented a conjugative plasmid with coresistance to tetracycline and copper, reinforcing the concern that antibiotic resistance by acquisition of plasmids can be induced by the selective pressure of heavy metals in the environment.

Molecular analysis of antimicrobial-susceptible and -resistant Escherichia coli from retail meats and human stool and clinical specimens in a rural community setting

BACKGROUND

Foodborne antimicrobial-resistant Escherichia coli may colonize and cause infections in humans, but definitive proof is elusive and supportive evidence is limited.

METHODS

Approximately contemporaneous antimicrobial-resistant (n = 181) and antimicrobial-susceptible (n = 159) E. coli isolates from retail meats and from human stool and clinical specimens from a single rural U.S. community were compared for polymerase chain reaction (PCR)-defined phylogenetic group (A, B1, B2, or D) and virulence genotype. Meat and human isolates from the same phylogenetic group with similar virulence profiles underwent sequential two-locus sequence analysis, random amplified polymorphic DNA (RAPD) analysis, and pulsed-field gel electrophoresis (PFGE) analysis.

RESULTS

According to phylogenetic distribution, resistant stool isolates were more similar to resistant meat isolates than to susceptible stool isolates. Overall, 19% of meat isolates satisfied molecular criteria for extraintestinal pathogenic E. coli (ExPEC). Nine sequence groups included meat and human isolates, and 17 of these 64 isolates demonstrated >80% RAPD profile similarity to an isolate from the alternate source group (meat vs. human). However, PFGE profiles of the 17 isolates were unique, excepting two stool isolates from the same household.

CONCLUSION

Nearly 20% of meat-source resistant E. coli represented ExPEC. The observed molecular similarity of certain meat and human-source E. coli isolates, including antimicrobial-resistant and potentially pathogenic strains, supports possible foodborne transmission.

The expression of plasmid mediated afimbrial adhesin genes in an avian septicemic Escherichia coli strain

An Escherichia coli strain (SEPT13) isolated from the liver of a hen presenting clinical signs of septicaemia had a LD₅₀ of 4.0 × 10⁵ CFU/ml in one-day-old chickens, expressed Ia, Ib, E1, E3, K and B colicins and aerobactin. The strain was ampicillin and streptomycin resistant, and found to have fimA, csgA and tsh DNA related sequences; it could adhere to and invade HEp-2 and tracheal epithelial cells, expressed fimbriae (observed by electron microscopy), and had five plasmids of 2.7, 4.7, 43, 56, and 88 MDa. Transposon mutagenesis of strain SEPT13, with transposon TnphoA, resulted in a mutant strain named ST16 that had a LD₅₀ of 1.2 × 10¹² CFU/ml. All other biological characteristics of strain ST16 were the same as those detected for strain SEPT13 except for the migration of an 88 MDa plasmid to the 93 MDa position indicating the insertion of the transposon into the 88 MDa plasmid. The 93 MDa plasmid of strain ST16 was transferred, by electroporation assay, to non-pathogenic receptor strains (E. coli strains K12 MS101 and HB101), resulting in transformant strains A and B, respectively. These strains exhibited adhesion properties to in vitro cultivated HEp-2 cells but did not have the capacity for invasion. The adherence occurred despite the absence of fimbriae; this finding suggests that the 88 MDa plasmid has afimbrial adhesin genes.

Drug-resistant Escherichia coli, Rural Idaho

Stool carriage of drug-resistant Escherichia coli in home-living residents of a rural community was examined. Carriage of nalidixic acid–resistant E. coli was associated with recent use of antimicrobial agents in the household. Household clustering of drug-resistant E. coli was observed. Most carriers of drug-resistant E. coli lacked conventional risk factors.

Characterization of a plasmid-encoded adhesin of an avian pathogenic Escherichia coli (APEC) strain isolated from a case of swollen head syndrome (SHS)

An avian pathogenic Escherichia coli (APEC) strain designated SHS4, isolated from a chicken with clinical signs of swollen head syndrome (SHS), adhered to but did not invade Hep-2 and tracheal epithelial cells. The PCR amplified fimA, csgA and tsh gene sequences. It produced Ia, Ib, E1, E3, K, and B colicins, but not colicin V and aerobactin. It harboured two plasmids of 60 and 98MDa and was resistant to streptomycin and tetracycline. Conjugation with a nalidixic acid (Na) resistant K-12 recipient strain (MS101) showed that the 98MDa plasmid did not transfer, whereas transfer of the 60MDa plasmid resulted in concomitant transfer of adhesion to Hep-2 and tracheal epithelial cells, production of the colicins Ia, E1, E3, and K, and the tsh-related DNA sequence. Transposon (TnphoA) mutagenesis of strain TR4 gave rise to strain Mut23, which lost its adhesive capacities, but was still able to express the same colicins as did strain TR4. PCR was able to amplify the tsh-related DNA sequence in this strain and a molecular probe based on transposon TnphoA indicated that the transposon was inserted in the 60MDa plasmid. Based on these results, we suggest that the 60MDa plasmid have adhesion genes, which may be responsible for the initial colonization of the upper respiratory tract of chickens.

Efficacy of phosphomycin in the control of Escherichia coli infection of broiler chickens

Seventy-five 25-day-old broilers were divided into three groups: group I unmedicated and challenged with E. coli O78:K80; group F infected and treated with 150 ppm of phosphomycin in their drinking water, and group C acted as a control. Their weights, feed intake, clinical signs, macroscopic lesions, E. coli reisolation, and serum biochemistry were compared. Group F showed fewer symptoms and gross lesions than those from group I while the average daily gain, bodyweight, and feed intake were similar to the control group. E. coli was reisolated in 32 per cent of the livers and spleens from group I, compared with 4 per cent of liver and 8 per cent of spleens from group F. There was an increase in the levels of total protein and globulins in group I but not in group F. These results provide evidence of the therapeutic efficacy of phosphomycin in the control of an experimental E. coli infection in broiler chickens.

Characterization of two Escherichia coli isolates associated with poult enteritis and mortality syndrome

Two colonial types (1 and 2) of Escherichia coli are represented predominantly in cultures isolated from turkey poults with poult enteritis and mortality syndrome (PEMS). Biotype codes determined using two systems (BBL: 36570 and 34560 for colony types 1 and 2, respectively; API-20E: 5144572 and 5144512 for colony types 1 and 2, respectively) clearly establish these organisms as E. coli. These isolates were not clearly divergent from the general profile for E. coli, but colony type 2 differs from colony type 1 with regard to its negative reactions for ornithine decarboxylase and the fermentation of dulcitol, rhamnose, sucrose, and melibiose, suggesting that it is atypical. Colony type 1 is nonserotypable and nonmotile, whereas colony type 2 is serotyped as O136: motile because it has H antigens associated with flagella. Capsular antigens were not found, but thin capsules were seen on cells from both colony types in stained preparations. Cultural morphology was different with colony type 1 having a circular, mucoid, raised morphology and colony type 2 having an irregular, flat, rough morphology. Colony type 1 has a doubling time at 37 C of about 20 min, whereas colony type 2 doubles in 30 min. Furthermore, colony type 1 is a potent colicin producer, but colony type 2 is not a colicin producer. Both E. coli isolates have resistance profiles for multiple antibiotics. Each strain responds to third generation fluoroquinolone antibiotics by changing their biotypes and become resistant after culturing once in their presence. These E. coli are proposed as possible etiological links in the complex series of events that take place in poults susceptible to PEMS.

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

Antimicrobial therapy is an important tool in reducing the enormous losses in the poultry industry caused by Escherichia coli infections (colibacillosis). However, resistance to existing antimicrobials is widespread and of concern to poultry veterinarians. Antimicrobial resistance testing of 468 avian E. coli strains isolated in Spain showed very high levels of resistance to trimethoprim-sulfamethoxazole (67%) and the new fluoroquinolones (13 to 24%). As these antimicrobial agents may cause cross-resistance with human enteric pathogens, prudent use of them in veterinary medicine is highly recommended.

In vitro susceptibility of Escherichia coli strains isolated from diarrhoeic lambs and goat kids to 14 antimicrobial agents

The in vitro activities of 14 anti-microbial agents were determined against 92 strains of E. coli isolated from lambs (60 strains) and kids (32 strains) affected by neonatal diarrhoea. The overall percentage of resistant strains to streptomycin, sulphadimethoxine and tetracycline was very high (above 70%). A high level of resistance (from 30% to 50%) to ampicillin, kanamycin, neomycin and chloramphenicol was also detected. The E. coli strains were highly susceptible to cephalosporins, polymyxin and quinolones. Most of the strains showed multiresistance: 77.2% of isolates were resistant to at least two antibiotics, 55.4% were resistant to at least four antibiotics and 33.7% were resistant to at least six antibiotics. A total of 34 antibiotypes could be distinguished.