Edgardo Rodríguez

Role and clinical course of verotoxigenic Escherichia coli infections in childhood acute diarrhoea in Argentina

The aim of this study was to investigate the role and clinical course of verotoxigenic Escherichia coli (VTEC) infections in children with acute diarrhoea from Argentina, the country with the highest worldwide incidence of haemolytic uraemic syndrome (HUS). To accomplish this objective, 437 samples from children up to 6 years old with acute diarrhoea were collected and processed. More than 60 % of the children studied presented watery or mucous diarrhoea without blood, and in 25.2 % of the cases the samples contained blood. In a first screening, a multiplex PCR was performed to detect the presence of the vt(1), vt(2), eae, ehxA and saa virulence genes. The strains were then isolated and analysed to characterize their serotypes, virulence genes, antibiotic susceptibility profiles and verotoxin (VT) production. Forty-four of the 437 samples (10.1 %) were positive for VTEC virulence genes. VTEC-infected patients presented different types of diarrhoea (27.3 % belonged to the non-bloody type). Several serotypes and virulence genotypes were found. Isolates belonged to the serotypes O157 : H7, O145 : H(-), O26 : H11, O121 : H19, O111 : H2 and O118 : H2. HUS developed in 16 (36.4 %) patients positive for VTEC virulence genes. All of the VTEC isolates produced a cytopathic effect on Vero cell monolayers, confirming the ability to express VT. Despite most strains being sensitive to all of the antimicrobials studied, a positive association between clinical progression to HUS and antibiotic therapy was observed for the total number of patients studied, as well as for the VTEC(+) group. In conclusion, the data obtained in this study increase our knowledge of the role and clinical course of VTEC infection in childhood acute diarrhoea beyond bloody diarrhoea, and might be considered for the prevention, diagnosis and management of this disease. It is possible that the optimal approach for VTEC diagnosis could be using multiplex PCR to search for the presence of the vt(1), vt(2), eae and ehxA genes.

Detection of Integrase Gene in E. coli Isolated from Pigs at Different Stages of Production System

Integrons are one of the genetic elements involved in the acquisition of antibiotic resistance. The aim of the present research is to investigate the presence of integrons in commensal Escherichia coli (E. coli) strains, isolated from pigs at different stages of production system and from the environment in an Argentinian farm. Five sows postpartum and five randomly chosen piglets from each litter were sampled by rectal swabs. They were sampled again at day 21 and at day 70. Environmental samples from the farm were also obtained. E. coli containing any integron class or combination of both integrons was detected by polymerase chain reaction in 100% of sows and in piglets at different stages of production: farrowing pen stage 68.1%;, weaning 60%, and growing/finishing 85.8%, showing an increase along the production system. From environmental samples 78.4% of E. coli containing any integron class was detected. We conclude that animals and farm environment can act as reservoirs for potential spread of resistant bacteria by means of mobile genetic elements as integrons, which has a major impact on production of food animals and that can reach man through the food chain, constituting a problem for public health.

The effect of mare's age on multiple ovulation rate, embryo recovery, post-transfer pregnancy rate, and interovulatory interval in a commercial embryo transfer program in Argentina

Advanced maternal age is an important predisposing factor on the reduction of reproductive efficiency. The aim of this study was to evaluate the effect of donors age on several reproductive parameters in a commercial equine embryo transfer program. Donors were classified into 3 age groups: Group 1=fillies (3 and 4 years old), Group 2=middle age mares (aged 5-10) and Group 3=old mares (aged 13-25). Embryo recovery, multiple ovulation and pregnancy rates and interovulatory intervals were compared amongst age groups. Group 1 (171/244, 70.1%) and Group 2 (774/1081, 71.6%) had a higher (P<0.005) embryo recovery rate than Group 3 (385/701, 54.9%). Groups 2 and 3 were 2.5 and 3.4 times more likely to have multiple ovulations than Group 1 (P<0.05), respectively. The effect of age group on pregnancy rate was not significant (P>0.05). The interovulatory intervals length was influenced by individual mare (P<0.001), age (P<0.04), Day of flushing (P=0.009) and by month (P<0.012). The overall mean interovulatory interval of Group 1 (16.4±0.17 days) and Group 2 (16.6±0.12 days) was not different (P>0.05), but was shorter than the one of Group 3 (17.4±0.15 days; P<0.04). The embryo recovery rate of flushings from Groups 1 and 2 was influenced by the length of the previous interovulatory interval (P=0.03).

Variation in the Distribution of Putative Virulence and Colonization Factors in Shiga Toxin-Producing Escherichia coli Isolated from Different Categories of Cattle

Shiga toxin-producing Escherichia coli (STEC) are pathogens of significant public health concern. Several studies have confirmed that cattle are the main reservoir of STEC in Argentina and other countries. Although Shiga toxins represent the primary virulence factors of STEC, the adherence and colonization of the gut are also important in the pathogenesis of the bacteria. The aim of this study was to analyze and to compare the presence of putative virulence factors codified in plasmid -katP, espP, subA, stcE- and adhesins involved in colonization of cattle -efa1, iha- in 255 native STEC strains isolated from different categories of cattle from different production systems. The most prevalent gene in all strains was espP, and the less prevalent was stcE. katP was highly detected in strains isolated from young and rearing calves (33.3%), while subA was predominant in those isolated from adults (71.21%). Strains from young calves showed the highest percentage of efa1 (72.46%), while iha showed a high distribution in strains from rearing calves and adults (87.04 and 98.48% respectively). It was observed that espP and iha were widely distributed throughout all strains, whereas katP, stcE, and efa1 were more associated with the presence of eae and subA with the eae-negative strains. A great proportion of eae-negative strains were isolated from adults -dairy and grazing farms- and from rearing calves -dairy and feedlot-, while mostly of the eae-positive strains were isolated from dairy young calves. Data exposed indicate a correlation between the category of the animal and the production systems with the presence or absence of several genes implicated in adherence and virulence of STEC.

Effect of the combination of crude extracts of Penicillium griseofulvum and Fusarium graminearum containing patulin and zearalenone on rumen microbial fermentation and on their metabolism in continuous culture fermenters

Six single-flow continuous cultures were used to study the effects of the mycotoxins patulin (PAT) and zearalenone (ZEN) alone or in combination on rumen microbial fermentation. In each of the four 7-d periods, the fermenters were supplemented in a 2 × 3 factorial arrangement with two levels of PAT (0 and 20 mg/l) and three levels of ZEN (0, 5 and 10 mg/l). The treatments did not affect the apparent and true digestibility of organic matter. PAT alone decreased the digestibility of neutral detergent fibre (NDF) and acid detergent fibre (ADF) (p < 0.01), but in the presence of 5 or 10 mg/l of ZEN, there were no effects of PAT. In contrast, the digestibility of NDF and ADF was decreased at 10 mg/l of ZEN in the absence of PAT (p < 0.05). The pH of the fermenters increased after 2 and 3 d of PAT treatment (p < 0.01). PAT decreased the concentration of total volatile acids (VFA), the molar proportion of acetate and the acetate:proportionate ratio (p < 0.01). The molar concentrations of other VFA were unchanged. Ammonia N (NH3–N) flow increased (p < 0.05) and there was a tendency to a higher NH3–N concentration (p < 0.1) in fermenters with PAT. Total N, non-ammonia N and bacterial N as well as efficiency of microbial protein synthesis and efficiency of N utilisation were not affected by treatments. PAT was nearly completely degraded during incubation. The mean recovery of ZEN, α-zearalenol and β-zearalenol expressed as a proportion of administered ZEN was less than 50% in effluents from fermenters receiving only ZEN and ZEN plus PAT, respectively. With exception of fibre digestion, the co-administration of PAT and ZEN did not elicit interaction effects on most measured parameters of rumen metabolism.

Effect of Cynara scolymus and Silybum marianum extracts on bile production in pigs

ABSTRACT Many of the beneficial effects on productive performance observed when vegetable extracts are incorporated as feed additives in intensive farming can be explained by an increase in bile production. An experiment was conducted to study choleretic and cholagogue effect of a Cynara scolymus extract formulation and of silymarin in pigs. Pigs were cannulated with a T-tube catheter in the bile duct. Bile production was continuously measured and re-infused to the duodenum through Oddi’s sphincter at the same production rate. Treatments: Group A (n = 6), commercial feed; Group B (n = 6), C. scolymus extract (300 g/tonne) and Group C (n = 6), silymarin (300 g/tonne). Bile production was recorded hourly for each animal during 24 h. Total bile acids’ concentrations in bile, just before and one hour after meals were evaluated. Average daily bile production for pigs in group B was 66% higher than for pigs in groups A or C (P < .05). When bile acids’ concentrations before and after meals were compared, only pigs from group B exhibited an increase (P = .0023). From this study, it was concluded that neither choleretic nor cholagogue effects are attained with silymarin supplementation. On the contrary, C. scolymus extract increases bile production and secretion in pigs.

Reproductive Characteristics in Old and Young Subfertile Mares: Are They Really Different?

Abstract Physiological and pathological mechanisms that determine subfertility (pregnancy failure, irregular cycles, and abnormalities in reproductive tract) in old mares (OM) have being studied by many authors. However, some young mares also share this reproduction condition although no previous reports have being published. We decided to investigate reproductive parameters of young subfertile mares (YSM) in order to understand the basis of their reproductive behavior. Forty‐nine subfertile mares were classified and separated into 2 groups: YSM (3–10 years old; n = 28) and OM (13–23 years old; n = 21). Different number of cycles (1–8) was used for data analysis on the embryo recovery rate (ERR), interovulatory interval (IOI), multiple ovulation rate (MOR) and plasmatic progesterone. Embryo quality was evaluated by gene expression through RNAm analysis. Effluent samples were taken for bacteriological and cytological evaluation and endometrial biopsies were performed to evaluate the presence of inflammatory cells and endometrial progesterone receptors (PR). There was no significant differences in ERR (P = .1230) on the percentage of each embryonic stage found on the different days of flushing (P > .05); on embryo gene expression (P > .05); on MOR (P = .1218); and on plasmatic progesterone at day 8 PO (P = .1230). However, differences were found on the percentage of positive cytologies (P = .0122) and bacteriological cultures (P = .0023); the amount of mononuclear cells in biopsies (P < .05) and distribution of PR on endometrial localization. In conclusion, YSM share some physiopathological mechanisms with OM that could explain their reproductive performance’s similarities. HighlightsWe compare reproductive behavior between two age groups of subfertile mares.Young subfertile mares have similar reproductive behavior to old mares.In old mares, we found additional alterations related to uterine function which could be responsible for embryonic loss.