Virulence factors and genetic variability of uropathogenic Escherichia coli isolated from dogs and cats in Italy

In this study, the association between virulence genotypes and phylogenetic groups among Escherichia (E.) coli isolates obtained from pet dogs and cats with cystitis was detected, and fingerprinting methods were used to explore the relationship among strains. Forty uropathogenic E. coli (UPEC) isolated from dogs (n = 30) and cats (n = 10) in Italy were analysed by polymerase chain reaction (PCR) for the presence of virulence factors and their classification into phylogenetic groups. The same strains were characterized by repetitive extragenic palindromic (REP)- and enterobacterial repetitive intergenic consensus (ERIC)-PCR techniques. We found a high number of virulence factors such as fimbriae A, S fimbriae (sfa) and cytotoxic necrotizing factor 1 (cnf1) significantly associated with phylogenetic group B2. We demonstrated a high correlation between α-hemolysin A and pyelonephritis C, sfa, and cnf1 operons, confirming the presence of pathogenicity islands in these strains. In addition, UPEC belonging to group B2 harboured a greater number of virulence factors than strains from phylogenetic groups A, B1, and D. REP- and ERIC-PCR grouped the UPEC isolates into two major clusters, the former grouping E. coli strains belonging to phylogenetic group B2 and D, the latter grouping those belonging to groups A and B1. Given the significant genetic variability among the UPEC strains found in our study, it can be hypothesized that no specific genotype is responsible for cystitis in cats or dogs.     

Potentiation of antibiotic activity by EDTA-tromethamine against three clinically isolated Gram-positive resistant bacteria. Anin vitro investigation

Thein vitro synergistic effects of combinations of EDTA-tromethamine and five antimicrobial agents (ampicillin, cephalexin, oxytetracycline, streptomycin and sulphadimethoxine) on three clinically isolated Gram-positive bacteria (Staphylococcus aureus, Staphylococcus hominis andStreptococcus faecium) were investigated. The bacteria had been isolated from three cases of canine otitis resistant to -lactam antibiotic therapy. The antimicrobial activity was evaluated by measuring the minimal inhibitory concentration for the antibiotics alone or in combination with EDTA-tromethamine. EDTA-tromethamine potentiated the activity of cefalexin againstS. aureus andS. hominis, of oxytetracycline againstS. aureus andS. faecium and of streptomycin againstS. faecium. No significant effects were noted on the activity of oxytetracycline againstS. hominis. The remaining combinations gave a slight synergistic effect. As previously shown for Gram-negative resistant bacteria, these data suggest that the association of EDTA-tromethamine and appropriate antibiotic therapy may be useful to overcome persistent infections of soft tissues in domestic animals.Abbreviations cfu colony forming units - EDTA ethylenediaminetetraacetic acid - MIC minimal inhibitory concentration - tromethamine tris(hydroxymethyl)- aminomethane Part of this paper was communicated at the XLVI Congress of the Italian Society of Veterinary Sciences, Venice, 30 September – 3 October 1992     

Illegal Drug Treatments and Drug Metabolism: Biomarkers or Not?

Veterinary Research Communications -     

In vitro antimicrobial activity of marbofloxacin and enrofloxacin against bacterial strains isolated from companion animals

Fluoroquinolones were originally developed for the Gram-negative aerobic spectrum, but the newer generation agents are also highly effective against some Gram-positive pathogens and cause few adverse effects. Owing to these characteristics, fluoroquinolones are often used in first line therapy in small animal practice. However, their widespread use has raised concern over emerging bacterial resistance. In this study we evaluated the in vitro efficacy of two fluoroquinolones, marbofloxacin and enrofloxacin, on field strains isolated from clinical infections between 2002 and 2005. Our data show that most of the isolates are still sensitive to both antimicrobials and marbofloxacin was more effective than enrofloxacin, especially against P. aeruginosa and beta-Streptococci (P < 0.01). beta-Streptococci demonstrated the greatest resistance to the two study drugs.     

Interaction of mammary bovine ABCG2 with AFB1 and its metabolites and regulation by PCB 126 in a MDCKII in vitro model

The ATP‐binding cassette efflux transporter ABCG2 plays a key role in the mammary excretion of drugs and toxins in humans and animals. Aflatoxins (AF) are worldwide contaminants of food and feed commodities, while PCB 126 is a dioxin‐like PCB which may contaminate milk and dairy products. Both compounds are known human carcinogens. The interactions between AF and bovine ABCG2 (bABCG2) as well as the effects of PCB 126 on its efflux activity have been investigated by means of the Hoechst H33342 transport assay in MDCKII cells stably expressing mammary bABCG2. Both AFB1 and its main milk metabolite AFM1 showed interaction with bABCG2 even at concentrations approaching the legal limits in feed and food commodities. Moreover, PCB 126 significantly enhanced bABCG2 functional activity. Specific inhibitors of either AhR (CH233191) or ABCG2 (Ko143) were able to reverse the PCB 126‐induced increase in bABCG2 transport activity, showing the specific upregulation of the efflux protein by the AhR pathway. The incubation of PCB 126‐pretreated cells with AFM1 was able to substantially reverse such effect, with still unknown mechanism(s). Overall, results from this study point to AFB1 and AFM1 as likely bABCG2 substrates. The PCB 126‐dependent increased activity of the transporter could enhance the ABCG2‐mediated excretion into dairy milk of chemicals (i.e., drugs and toxins) potentially harmful to neonates and consumers.     

The Comparative Effects of Subchronic Administration of Triphenyltin Acetate (TPTA) on the Hepatic and Renal Drug-Metabolizing Enzymes in Rabbits and Lambs

Nebbia, C., Dacasto, M., Ceppa, L., Gennaro Soffietti, M., Spinelli, P., Bergo, V. and Di Simplicio, P., 1997. The comparative effects of subchronic administration of triphenyltin acetate (TPTA) on the hepatic and renal drug-metabolizing enzymes in rabbits and lambs. Veterinary Research Communications, 21 (2), 117-125The purpose of this study was to determine whether subchronic (70 days) oral exposure to moderate to high levels of triphenyltin acetate (TPTA), an organotin derivative used worldwide, would affect the microsomal hepatic and renal drug-metabolizing enzymes in rabbits and lambs. Rabbits were offered a diet containing 0, 15, 75 or 150 ppm TPTA, while lambs were daily given 0, 1.5 or 7.5 mg TPTA per kg bw. The tin content in the liver and kidneys was measured by atomic absorption spectrophotometry. In the rabbits' livers, TPTA failed to affect the cytochrome P450 content, or the oxidative, hydrolytic (carboxylesterase) or conjugative (UDPG-transferase) enzyme activities studied. In contrast, a striking dose-related increase in both P450 content and carboxylesterase activity (up to 280%) was detected in the rabbits' kidneys, but the ECOD and EROD activities were respectively unchanged or moderately depressed. None of the enzymes studied showed statistically significant changes in the ovine hepatic or renal subfractions. The results suggest that repeated exposure to TPTA could lead to the induction of a particular P450-isoenzyme in rabbit kidneys which is concerned with the metabolism of endogenous compounds (e.g. steroids, prostaglandins, thromboxanes). The lack of significant tissue- and species-related differences in the concentration of tin supports the hypothesis that the changes observed in the rabbits' kidneys may not have been caused solely by the accumulation of the metal in the tissues.     

Pathologic changes, tissue distribution, and extent of conversion to ethylenethiourea after subacute administration of zinc ethylene-bis-dithiocarbamate (zineb) to calves with immature rumen function.

The toxicity of zinc ethylene-bis-dithiocarbamate (zineb), a widely used fungicide, was studied in four 4-week-old Friesian calves with immature rumen function. Calves were first subjected to liver biopsy, and thereafter, 3 of them were orally administered 200 mg of zineb/kg of body weight daily for 80 days, whereas the fourth calf served as control and remained untreated. Clinical, hematologic, and pathologic (including ultrastructural) findings were recorded. The distribution in body fluids and tissues of the parent compound and one of its main metabolites, ethylenethiourea (ETU), also was examined. Treated calves had unthrifty appearance and reduction in weight gain. They also had remarkable impairment of thyroid function, as reflected by reduction in serum concentrations of triiodothyronine and thyroxine and increase in weight of the thyroid gland associated with epithelial vacuolization and foci of hyperplasia. Moderate increase in liver glycogen content and impairment in maturation of germ cells were recorded consistently. Whereas zineb was widely distributed in body tissues, ETU accumulated mainly in the liver and the thyroid gland, although noticeable concentrations also were attained in muscle. Data were consistent with involvement of ETU mainly in the pathogenesis of thyroid gland lesions, and indicate that unweaned calves given zineb develop a clinicopathologic syndrome that does not differ qualitatively from that already described in adult cattle exposed to zineb.     

Associations between dogs that were serologically positive for Rickettsia conorii relative to the residences of two human cases of Mediterranean spotted fever in Piemonte (Italy)

A geographic information system and K-function analysis were used to evaluate the spatial association of canine serological results for Rickettsia conorii, the causative agent of Mediterranean spotted fever (MSF), and clinical cases of MSF in humans in Piemonte, northwest Italy. The residences of dog owners were clustered in two rural villages in the province of Cuneo, where two human cases of MSF occurred in 1997 and 1998. Eighteen out of 116 dogs examined were positive by indirect immunofluorescent assay (IFA+, titre > or =1:160) for MSF. K-functions were compared for IFA+ dogs and for all dogs sampled. Monte Carlo and bootstrap simulations demonstrated that clustering of IFA+ dogs was significantly greater than clustering of all dogs, at distances of less than 0.6 km from human cases of MSF. Logistic regression analysis indicated that the risk of being IFA+ was highest for dogs residing within the first quartile of distance (0.7 km) from human cases of the disease, and for dogs that were not confined. However, year and season of blood collection were not associated with IFA status. It was concluded that a relatively high dog population density along with a rural or semi-rural environment favours the occurrence of emergent foci of MSF in the province of Cuneo.     

Oxidative monensin metabolism and cytochrome P450 3A content and functions in liver microsomes from horses, pigs, broiler chicks, cattle and rats

The oxidative metabolism of monensin, an ionophore antibiotic extensively used in veterinary practice as a coccidiostat and a growth promoter, was studied in hepatic microsomal preparations from horses, pigs, broiler chicks, cattle and rats. As assayed by the measurement of the amount of the released formaldehyde, the rate of monensin O-demethylation was nearly of the same order of magnitude in all species, but total monensin metabolism, which was estimated by measuring the rate of substrate disappearance by a high-performance liquid chromatography (HPLC) method, was highest in cattle, intermediate in rats, chicks and pigs, and lowest in horses. When expressed as turnover number (nmol of metabolized monensin/min nmol cytochrome P450-1), the catalytic efficiency (chick > cattle > pig approximately rat > horse) was found to correlate inversely with the well known interspecies differences in the susceptibility to the toxic effects of the ionophore, which is characterized by an oral LD50 of 2-3 mg/kg bodyweight (bw) in horses, 50-80 mg/kg bw in cattle and 200 mg/kg bw in chicks. Chick and cattle microsomes also displayed both the highest catalytic efficiency toward two P450 3A dependent substrates (erythromycin and triacetyloleandomycin) and the highest immunodetectable levels of proteins cross-reacting with anti rat P450 3A1/2. Further studies are required to define the role played by this isoenzyme in the oxidative biotransformation of the drug in food producing species.