Neonatal Diarrheic Calves Research Articles

Enteral fluid therapy in neonatal calves and features of commercially available electrolyte solutions in Brazil

ABSTRACT: According to the World Health Organization, the development of orally replacement fluids and electrolytes was one of the most significant advances of the twentieth century, markedly reducing mortality from diarrheal children. In veterinary medicine, oral electrolyte solutions (OES) are routinely used to treat diarrheic neonatal calves in order to correct water, electrolyte and acid base imbalances. In North America, the use of OES is routine and there are at least 20 commercial alternatives. Use of OES has increased in recent years in Brazil, but just five commercial products are currently available. The OES should contain, in suitable concentrations, electrolytes, glucose and an alkalizing agent to ensure its therapeutic efficacy. This review aimed to address the therapeutic importance of OES for neonatal calves and to evaluate the compositions and characteristics of those commercially available in Brazil.

Novel Heat-Stable Enterotoxin (STa) Immunogen Based on Cationic Nanoliposomes: Preparation, Characterization and Immunization

The novelties encountered in the field of formulation have provided promising solutions for the problematic vaccine development of hapten molecules. In the current study, the novel preparation of a cationic nanoliposomal immunogen of the heat stable enterotoxin (STa) was reported. STa was produced from clinically ETEC isolate of diarrheic neonatal calves and purified using RP-HPLC. STa was loaded into the cationic vesicles which were characterized for their particle size, surface charge, morphology, STa loading, and stability. The STa loaded cationic nanoliposome was used for mice immunization and the generation of STa antibody was monitored using ELISA. Results displayed the spherical nature of the STa loaded vesicles, their suitable size and homogeneity represented by a particle size of 228.1 nm and a PDI of 0.202. The surface charge of the STa nanoliposomes was +29.9, demonstrating sufficient stability during refrigeration storage. The STa loaded cationic nanoliposome was able to elicit specific STa antibody response, and to confer effective protection against STa challenge in mice. The STa antibody binding titer and neutralization capacity were 105 and 104 mouse units/ml serum, respectively. The developed system is a one-step procedure, which overcomes the disadvantage of the complexity of generation of the hapten-carrier conjugate. In conclusion, the developed STa-cationic nanoliposomal immunogen is feasible and has the potential to improve effectiveness against ETEC, suggesting its applicability in preventing the harmful effects of ETEC infection in neonatal calves.

Isolation and identification of group A rotaviruses among neonatal diarrheic calves, Morocco.

BackgroundGroup A rotaviruses (RVA) are the main cause of neonatal calve diarrhea (NCD) in Morocco. In this study, we isolated RVA strains from NCD clinical samples in order to support RVA disease control in Morocco. This isolation process constitutes a first step toward vaccine development.MethodsThirteen fecal samples were obtained from calves with a single episode of neonate calf diarrhea at three different dairies and two samples were collected from field during a severe NCD outbreak. Diagnosis of RVA infection was based on fecal immune-chromatographic rapid test and further evaluated for their hemagglutination (HA) activity. RVA isolation was carried out on MA104 cells after inoculates were treated with different concentrations of trypsin TPCK. All RVA isolates were confirmed by LSI VetMAX™ Triplex Ruminant Rotavirus & Coronavirus Real-Time PCR kit. G and P typing were determined by direct sequencing of the VP4 and VP7 amplicons.ResultsRVA isolation was achieved for nine clinical samples following one or two passages (60 %) and was properly depended on HA activity and trypsin treatment of inoculates. The first sign of CPE detected consisted of increased cell granularity, obscure cell boundaries, cell rounding, and eventual degeneration and detachment of cells. At lower TPCK concentration (3–10 μg/inoculum), no changes at the cellular level were observed, while cells activated with 25–30 μg of trypsin/inoculums, they degenerated and trypsin cytotoxicity was enhanced. Appreciable changes in cell’s morphology were detected with optimal trypsin concentration of 15–20 μg trypsin/inoculums. Data from qRT-PCR confirmed that unsuccessful cultivations have No-Ct, and all nine isolates have Ct values ranged between 12.17 and 24.69. Analysis sequencing revealed that field isolates were of G6 P[5] serotype and isolates from the dairy NCD samples were of G10 P[14] serotype.ConclusionsTo our knowledge, this is the first study in Morocco which reports the circulation of G10P[14] in NCD on dairy farms and G6P[5] in the field. Our study constitutes a crucial and a necessary step allowing preventive and veterinary medicine to support RVA disease controls in the country.

Quantitative physicochemical analysis of acid-base balance and clinical utility of anion gap and strong ion gap in 806 neonatal calves with diarrhea.

BackgroundAcid‐base abnormalities in neonatal diarrheic calves can be assessed by using the Henderson‐Hasselbalch equation or the simplified strong ion approach which use the anion gap (AG) or the strong ion gap (SIG) to quantify the concentration of unmeasured strong anions such as d‐lactate.Hypothesis/ObjectivesTo determine and compare the clinical utility of AG and SIG in quantifying the unmeasured strong anion charge in neonatal diarrheic calves, and to examine the associations between biochemical findings and acid‐base variables by using the simplified strong ion approach. We hypothesized that the SIG provides a more accurate prediction of unmeasured strong anions than the AG.AnimalsEight hundred and six neonatal diarrheic calves admitted to a veterinary teaching hospital.MethodsRetrospective study utilizing clinicopathologic findings extracted from medical records.ResultsHyperphosphatemia was an important predictor of venous blood pH. Serum inorganic phosphorus and plasma d‐lactate concentrations accounted for 58% of the variation in venous blood pH and 77% of the variation in AG and SIG. Plasma d‐ and total lactate concentrations were slightly better correlated with SIG (r s = −0.69; −0.78) than to AG (r s = 0.63; 0.74).Conclusions and Clinical ImportanceStrong ion gap is slightly better at quantifying the unmeasured strong anion concentration in neonatal diarrheic calves than AG. Phosphorus concentrations should be included as part of the calculation of A tot when applying the simplified strong ion approach to acid‐base balance to critically ill animals with hyperphosphatemia.

Risk factors for the development of hypokalemia in neonatal diarrheic calves.

BackgroundNeonatal diarrheic calves have a clear negative potassium balance because of intestinal losses and decreased milk intake but in the presence of acidemia, they usually show normokalemic or hyperkalemic plasma concentrations.ObjectivesTo assess whether marked hypokalemia occurs in response to the correction of acidemia and dehydration and to identify factors that are associated with this condition.AnimalsEighty‐three calves with a clinical diagnosis of neonatal diarrhea.MethodsProspective cohort study. Calves were treated according to a clinical protocol using an oral electrolyte solution and commercially available packages of 8.4% sodium bicarbonate, 0.9% saline and 40% dextrose infusion solutions.ResultsThe proportion of hypokalemic calves after 24 hours of treatment (19.3%) was twice as great as it was on admission to the hospital. Plasma K+ after 24 hours of treatment was not significantly correlated to venous blood pH values at the same time but positively correlated to venous blood pH values on admission (r = 0.51, P < .001). Base excess on admission (Odds ratio [OR] = 0.81, 95% confidence interval [CI] = 0.70–0.94), duration of diarrhea (OR = 1.37, 95% CI = 1.05–1.80), milk intake during hospitalization (OR = 0.54, 95% CI = 0.37–0.79) and plasma sodium concentrations after 24 hours (OR = 1.12, 95% CI = 1.01–1.25) were identified to be independently associated (P < .05) with a hypokalemic state after 24 hours of treatment.Conclusions and Clinical ImportanceFindings of this study suggest that marked depletion of body potassium stores is evident in diarrheic calves that suffered from marked metabolic acidosis, have a low milk intake and a long history of diarrhea.

Effects of alkalinization and rehydration on plasma potassium concentrations in neonatal calves with diarrhea.

BackgroundIncreased plasma potassium concentrations (K+) in neonatal calves with diarrhea are associated with acidemia and severe clinical dehydration and are therefore usually corrected by intravenous administration of fluids containing sodium bicarbonate.ObjectivesTo identify clinical and laboratory variables that are associated with changes of plasma K+ during the course of treatment and to document the plasma potassium‐lowering effect of hypertonic (8.4%) sodium bicarbonate solutions.AnimalsSeventy‐one neonatal diarrheic calves.MethodsProspective cohort study. Calves were treated according to a clinical protocol using an oral electrolyte solution and commercially available packages of 8.4% sodium bicarbonate (250–750 mmol), 0.9% saline (5–10 L), and 40% dextrose (0.5 L) infusion solutions.ResultsInfusions with 8.4% sodium bicarbonate solutions in an amount of 250–750 mmol had an immediate and sustained plasma potassium‐lowering effect. One hour after the end of such infusions or the start of a sodium bicarbonate containing constant drip infusion, changes of plasma K+ were most closely correlated to changes of venous blood pH, plasma sodium concentrations and plasma volume (r = −0.73, −0.57, −0.53; P < .001). Changes of plasma K+ during the subsequent 23 hours were associated with changes of venous blood pH, clinical hydration status (enophthalmos) and serum creatinine concentrations (r = −0.71, 0.63, 0.62; P < .001).Conclusions and Clinical ImportanceThis study emphasizes the importance of alkalinization and the correction of dehydration in the treatment of hyperkalemia in neonatal calves with diarrhea.

Changes in some serum enzymes and urea nitrogen in neonatal bovine diarrheic calves of different age groups

The present study was conducted on 100 cases of bovine calf diarrhea to monitor the activities of some serum enzymes viz., AST, ALP, GGT, CK and urea nitrogen in neonatal calves of different age groups. These calves were divided into 5 age groups viz., 1–7 day (7 calves), 8–14 days (5 calves), 15–21 days (30 calves), 22–30 days (19 calves) and 31–60 days (39 calves). The results of experimental groups were compared with normal standard values of different age groups. The diseased calves of all the age groups had significantly higher (p<0.01) serum AST activities as well as urea nitrogen as compared to control. Serum ALP activities were significantly low (p<0.01) in diseased calves of 8–14 days, 15–21 days and 31–60 days age groups. Alterations in other parameters were significant in specific age groups only.

Hematological changes in neonatal diarrheic calves of different age groups

The study was conducted on 100 neonatal calves of different age groups suffering from diarrhoea to identify any changes in the hematology. Hemoglobin levels of the affected calves of every age group were significantly decreased (p<0.01) as compared to corresponding control group. PCV values of 22–30 and 31–60 days diseased age groups were significantly (p<0.01) decreased but were not significantly different from the respective controls in other age groups. Significant leukocytosis, neutrophilia and lymphopenia were observed in diseased groups.

Direct ELISA aided coprological diagnosis of Cryptosporidium parvum infection in diarrheic neonatal calves in Mosul city, Iraq

This study was conducted for the detection of Cryptosporidium (C.) parvum infection in neonatal calves. A total of 220 fecal samples (diarrheic 110 and non-diarrheic 110) of neonatal calves were collected from Mosul city, Iraq over a period of 16 months from November 2010 to March 2012. The age of the calves ranged from 1 to 30 days. All the fecal samples were analyzed by capture direct ELISA. The infection was found in 29.0% (n=32/110) of the diarrheic calves. The infection was mostly prevalent (p<0.001) in the calves of three weeks of age. No C. parvum infection could be detected in the non-diarrheic animals.

Hyperkalemia in neonatal diarrheic calves depends on the degree of dehydration and the cause of the metabolic acidosis but does not require the presence of acidemia

Hyperkalemia is a clinically important electrolyte imbalance in neonatal diarrheic calves that has previously been associated with skeletal muscle weakness and life-threatening cardiac arrhythmias. The aim of the present retrospective analysis was to identify risk factors for hyperkalemia in a convenience sample of 832 calves (≤21d of age) with a clinical diagnosis of diarrhea admitted to a veterinary teaching hospital. Plasma potassium concentrations were most closely associated with parameters of dehydration and renal function such as serum creatinine [Spearman correlation (rs)=0.61], urea (rs=0.51), and inorganic phosphorus concentrations (rs=0.64). Plasma potassium concentrations were weakly associated with venous blood pH (rs=−0.21). Although venous blood pH was not predictive in a multivariate linear regression analysis, the odds of having hyperkalemia (>5.8mmol/L) in acidemic calves was found to be 8.6 times as high as in nonacidemic calves [95% confidence interval (CI): 4.8–15.4]. However, the presence of hyperkalemia depended on the nature of an existing acidosis, and the odds for the presence of hyperkalemia in acidemic calves with hyper-d-lactatemia (>3.96mmol/L) were only 0.15 times as high as in acidemic calves with normal d-lactate concentrations (95% CI, 0.11–0.22). Acidemia in hyperkalemic diarrheic calves was associated with hyponatremia and increased concentrations of inorganic phosphorus, l-lactate, and unidentified strong anions that presumably included uremic anions such as sulfate. We conclude that hyper-d-lactatemia in neonatal diarrheic calves is not usually associated with elevated plasma potassium concentrations. Application of the simplified strong ion acid-base model indicated that dehydration is an important contributor to the pathogenesis of hyperkalemia and acidemia in neonatal calves with diarrhea.

Changes in blood acid-base balance parameters and coagulation profile during diarrhea in calves

The purpose of this study was to investigate possible alterations in acid-base balance parameters and the coagulation profile in neonatal diarrheic calves. Twenty neonatal diarrheic and 20 clinically healthy neonatal calves aged between 1 week to 10 days were used. All blood samples were taken on the third day from the onset of diarrhea symptom. Venous blood samples were collected from each animal to determine platelet numbers, pH, pCO2, pO2, HCO(3-), BE, O2SAT, ctCO2 and electrolytes (K+, Na+ and Cl(-)). Plasma samples were collected from each animal for the measurement of prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), the concentrations of fibrinogen, D-dimer and the activity of antithrombin III (AT III). Blood pH (7.19), BE (-10.6 mmol/l), HCO3(-) (25.15 mmol/l), pO2 (3.33 kPa), O2SAT (24.12 %) were significantly lower and serum concentration of K+ (6.55 mmol/l) was significantly higher in diarrheic calves. These changes indicate the state of uncompensated metabolic acidosis with accompanying hyperkalemia. TT (32.05s) and APTT (39.9s) values were more prolonged in calves with diarrhea than in the control group. D-dimer (587.25 microg/l) concentrations were significantly increased while a visible drop in AT III (103.75%) activity and platelets counts (598 x10(9)/l) were observed in diarrheic group of calves. The results suggest that a consumptive type of disseminated intravascular coagulation (DIC) developed in diarrheic calves.

English

&nbsp; The&nbsp;aim&nbsp;of this study was to investigate the antimicrobial resistance and to characterize the implicated genes in&nbsp;Escherichia coli&nbsp;isolated from diarrheic calves&nbsp;during&nbsp;2008-2011. A total of 104&nbsp;samples&nbsp;were tested to&nbsp;15&nbsp;antimicrobial agents with disk-diffusion&nbsp;method.High resistance to&nbsp;amoxicillin, streptomycin, tetracycline,&nbsp;trimethoprim-sulfamethoxazoleand&nbsp;doxycycline&nbsp;was&nbsp;detected.&nbsp;A total of 13 out of&nbsp;the&nbsp;16 resistance genes were searched in this study. The principal mechanisms of resistance found in the 104 calf isolates wereblaTEM (84.6%), aadA1(73.3%), cmlA(46.2%), tet(B)(79.8%),&nbsp;sulI (74.0%) and dhfrV(54.8%). One&nbsp;kind of&nbsp;amino acid change in gyrA (four&nbsp;Ser83&rarr;Leu) and&nbsp;sixteen&nbsp;in parC (twelve&nbsp;80Ser&rarr;Arg,&nbsp;four&nbsp;80Ser&rarr;Ile) were identified in the&nbsp;20&nbsp;fluoroquinolone-resistant&nbsp;isolates.&nbsp;According to pulsed field gel electrophoresis&nbsp;(PFGE)&nbsp;results,&nbsp;clonal dissemination of&nbsp;multi-drug resistance&nbsp;(MDR)&nbsp;strains&nbsp;played an important role&nbsp;in&nbsp;the severe resistant situation among&nbsp;diarrheic neonatal calves in northeastern China. &nbsp; Key words:&nbsp;Escherichia coli,&nbsp;calf,&nbsp;antimicrobial resistance,&nbsp;resistance genes,&nbsp;clonal dissemination

Prevalence of rotaviral infection in diarrheic neonatal calves in Mosul city, Iraq

Aim: The objective of the current study was to identify the prevalence of rotaviral infection in neonatal calves in Mosul city, Iraq.

Prevalence and antimicrobial susceptibility of virulent and avirulent multidrug-resistant Escherichia coli isolated from diarrheic neonatal calves

To determine the prevalence of selected virulence genes and the antimicrobial susceptibility of multidrug-resistant (MDR) Escherichia coli isolated from diarrheic neonatal calves. 97 E coli isolates from diarrheic neonatal calves. E coli isolates were tested via PCR assay for 6 virulence genes and susceptibility to 17 drugs belonging to 9 classes. A 2-sample test of proportions was used to make comparisons between proportions of virulent and avirulent MDR isolates. 23 of 97 (23.7%) isolates were virulent, and 74 (76.3%) were avirulent. Of the 23 virulent isolates, 15 (65.2%) were positive for K99, 14 (60.9%) for F41, 12 (52.2%) for STa, 9 (39.1%) for Stx1, 6 (26.1%) for intimin, and 0 (0%) for Stx2. Twenty of 23 (87.0%) virulent isolates expressed ≥ 2 virulence genes, and 3 of 23 (13.0%) were positive for 1 virulence factor. Eight of 23 (34.8%) virulent isolates expressed STa, K99, and F41, whereas 1 of 23 (4.4%) was positive for STa, F41, intimin, and Stx1. The second most frequent gene pattern was Stx1 and intimin. Twenty of 23 (87.0%) virulent isolates were MDR; the highest prevalence of resistance was recorded for the macrolide-lincosides, followed by the tetracyclines and penicillins. Also, 17 of 23 (74.0%) virulent isolates were resistant to sulfadimethoxine, and 10 of 23 (43.5%) were resistant to trimethoprim-sulfamethoxazole. Additionally, 60 of 74 (81.0%) avirulent isolates were MDR. The prevalence of multidrug resistance was comparable for virulent and avirulent E coli isolated from diarrheic neonatal calves. Cephalosporins and aminoglycosides had reasonable susceptibility.

Clinical Evaluation of an Oral Electrolyte Solution Formulated Based on Strong Ion Difference (SID) and Using Propionate as the Organic Anion in the Treatment of Neonatal Diarrheic Calves with Strong Ion Acidosis

Background: It is postulated that the concentrations of the major strong ions (Na, K, and Cl) in oral electrolyte solutions play a major role in clinical efficacy of these solutions for rehydration and corrections of metabolic acid base derangements. Objectives: The purpose of this study was to test prospectively the efficacy of an OES (OESexp) formulated based on concentration of strong ion difference (SID) and propionate in a group of calves with naturally occurring neonatal diarrhea and clinically detectable dehydration and acid base abnormalities. Animals: Ten client owned calves of varying breeds, 2 - 22 days old, presented to a veterinary teaching hospital with a history of naturally occurring acute undifferentiated diarrhea, progressive depression and dehydration for treatment. Methods: Clinical and laboratory parameters were measured pre and post two oral electrolyte treatments to assess efficacy of the experimental OES to correct clinical and clinico pathological parameters. For the clinical trial the calves served as their own controls. For control of safety of medication 4 normal calves were force fed 4 L of OESexp and followed over a 24 hour period. Results: All calves had severe diarrhea and metabolic acidosis. The metabolic acidosis observed in the plasma of these calves and reflected by pH, HCO3- SID and base deficit was corrected significantly towards reference ranges (p < 0.05) with two 2 L feedings 12 hours apart. Dehydration was significantly corrected and all calves were discharged 1 - 3 days post admission. Conclusion and Clinical Importance: The use of SID is a valid approach when formulating oral electrolytes solutions for use in calves with acute diarrhea and metabolic derangement. Sodium propionate is valid substitute for commonly used sodium base equivalents in North America in oral electrolyte solutions.

Construction and validation of a decision tree for treating metabolic acidosis in calves with neonatal diarrhea

BackgroundThe aim of the present prospective study was to investigate whether a decision tree based on basic clinical signs could be used to determine the treatment of metabolic acidosis in calves successfully without expensive laboratory equipment. A total of 121 calves with a diagnosis of neonatal diarrhea admitted to a veterinary teaching hospital were included in the study. The dosages of sodium bicarbonate administered followed simple guidelines based on the results of a previous retrospective analysis. Calves that were neither dehydrated nor assumed to be acidemic received an oral electrolyte solution. In cases in which intravenous correction of acidosis and/or dehydration was deemed necessary, the provided amount of sodium bicarbonate ranged from 250 to 750 mmol (depending on alterations in posture) and infusion volumes from 1 to 6.25 liters (depending on the degree of dehydration). Individual body weights of calves were disregarded. During the 24 hour study period the investigator was blinded to all laboratory findings.ResultsAfter being lifted, many calves were able to stand despite base excess levels below −20 mmol/l. Especially in those calves, metabolic acidosis was undercorrected with the provided amount of 500 mmol sodium bicarbonate, which was intended for calves standing insecurely. In 13 calves metabolic acidosis was not treated successfully as defined by an expected treatment failure or a measured base excess value below −5 mmol/l. By contrast, 24 hours after the initiation of therapy, a metabolic alkalosis was present in 55 calves (base excess levels above +5 mmol/l). However, the clinical status was not affected significantly by the metabolic alkalosis.ConclusionsAssuming re-evaluation of the calf after 24 hours, the tested decision tree can be recommended for the use in field practice with minor modifications. Calves that stand insecurely and are not able to correct their position if pushed require higher doses of sodium bicarbonate, if there is clinical evidence of a marked D-lactic acidosis. In those calves, determining the degree of loss of the palpebral reflex was identified as a useful decision criterion to provide an additional amount of 250 mmol sodium bicarbonate. This work demonstrates the clinical relevance of the discovery that D-lactate is responsible for most of the clinical signs expressed in neonatal diarrheic calves suffering from metabolic acidosis.

Plasma potassium-lowering effect of oral glucose, sodium bicarbonate, and the combination thereof in healthy neonatal dairy calves

Hyperkalemia is a common complication in neonatal diarrheic dairy calves and is corrected by administration of glucose or sodium bicarbonate. Although the hypokalemic effect of glucose is well established in other species, controversial results are reported for sodium bicarbonate. Our objective was to study the effect and mechanism of action of glucose and sodium bicarbonate on the potassium homeostasis of healthy neonatal dairy calves. Nine healthy neonatal Holstein-Friesian calves underwent 3 oral treatments with 2L of NaHCO3 (150mmol/L), glucose (300mmol/L), and glucose+NaHCO3 solution (300mmol/L+150mmol/L) in randomized order. Blood was obtained before treatment (T0) and at 30-min intervals thereafter. Changes between each time point and T0 were determined for all parameters. Urine was collected volumetrically to determine total renal potassium excretion over an 8-h posttreatment period. Plasma volume changes were extrapolated from changes in plasma protein concentration. Treatment and time effects were tested with repeated-measures ANOVA. Multivariate stepwise regression analysis using dummy variable coding was conducted to identify associations between changes in plasma potassium concentration ([K]) and changes in plasma glucose concentration ([glucose]), blood base excess, and plasma volume. Oral glucose and sodium bicarbonate treatments decreased [K] by 25 and 19%, respectively, whereas the combination of both compounds caused an intermediate [K] decline (22%). For the glucose treatment, the decline in [K] was only associated with changes in plasma [glucose] (partial R2=0.19). In NaHCO3-treated calves, [K] decline was associated with change of extracellular volume (partial R2=0.31) and blood base excess (partial R2=0.19). When glucose and NaHCO3 were combined, [K] decline was associated with changes in plasma volume (partial R2=0.30), BE (R2=0.22), and [glucose] (partial R2=0.03). Our results indicate that glucose lowers plasma [K] mainly through an insulin-dependent intracellular translocation of K, whereas NaHCO3 causes hypokalemia through hemodilution followed by intracellular translocation of K caused by the strong ion effect. The combination of glucose and NaHCO3 at the dosage used in this study does not have an additive hypokalemic effect. When combined, hemodilution and strong ion effect have the strongest effect on plasma [K], whereas the insulin-dependent effect of glucose appears to be blunted.

Detection of enterotoxigenic K99 (F5) and F41 from fecal sample of calves by molecular and serological methods.

Enterotoxigenic Escherichia coli (ETEC) is one of the major causes of neonatal calf diarrhea. Almost all ETEC bacteria are known to adhere to receptors on the small intestinal epithelium via their fimbriae, (F5 (K99) and F41).This study was undertaken to investigate the phenotypic and genotypic screening of virulence genes in E. coli K99 and F41. During January 2008 to December 2009, 298 diarrheic neonatal calves at 1–30 days old were studied by multiplex PCR, isolation, and serological grouping. Of the 298 diarrheic samples, 268 E. coli were isolated, of which 16 samples (5.3%) were positive for having the F5 (K99) fimbrial gene by PCR while all of the E. coli isolates also carried F41 fimbrial genes. Twenty-five percent of the isolates were proven not to be toxigenic as they did not possess the STa enterotoxin gene.

Molecular screening and risk factors of enterotoxigenic Escherichia coli and Salmonella spp. in diarrheic neonatal calves in Egypt

The aim of the present study was to carry out molecular epidemiological investigation on enterotoxigenic Escherichia coli (ETEC) K99 and Salmonella spp. in diarrheic neonatal calves. Fecal samples were obtained from 220 diarrheic calves at 9 farms related to four governorates in central and northern Egypt . E. coli and Salmonella spp. isolates were examined for E. coli K99 and Salmonella spp. using PCR . ETEC K99 was recovered from 20 (10.36 %) out of 193 isolates, whereas Salmonella spp. was recovered from nine calves (4.09%). Multivariable logistic regression was used to evaluate the risk factors associated with both infections. ETEC K99 was significantly affected by age ( P < 0.01; OR: 1.812; CI 95%: 0.566–1.769), colostrum feeding practice ( P < 0.01; OR: 5.525; CI 95%: 2.025–15.076), rotavirus infection ( P < 0.001; OR: 2.220; CI 95%: 0.273–1.251), vaccination of pregnant dams with combined vaccine against rotavirus, coronavirus and E. coli (K99) ( P < 0.001; OR: 4.753; CI 95%: 2.124–10.641), and vitamin E and selenium administration to the pregnant dam ( P < 0.01; OR: 3.933; CI 95%: 0.703–1.248). Infection with Salmonella spp. was found to be significantly affected by the animal age ( P < 0.05; OR: 0.376; CI 95%: 0.511–1.369), Hygiene ( P < 0.05; OR: 0.628; CI 95%: 1.729–5.612), and region ( P < 0. 01; OR: 0.970; CI 95%: 0.841–1.624). The results of the present study indicate the importance of PCR as rapid, effective and reliable tool for screening of ETEC and Salmonella spp. when confronted with cases of undifferentiated calf diarrhea. Moreover, identification of the risk factors associated with the spreading of bacteria causing diarrhea may be helpful for construction of suitable methods for prevention and control.

Genetic analysis of antimicrobial resistance in Escherichia coli isolated from diarrheic neonatal calves

This study was carried out to screen and analyze the genetic basis of antimicrobial resistance in Escherichia coli strains isolated from neonatal calf diarrhea in Egypt. A total of 182 isolates of E. coli recovered from 91 diarrheic neonatal calves were analyzed for antimicrobial susceptibilities, the presence of class 1 and class 2 integrons and antimicrobial resistance genes. Nineteen isolates (10.4%) showed multidrug resistance phenotypes and harbored at least three antimicrobial resistance genes. PCR screening detected class 1 integrons in 19 isolates (10.4%) and class 2 integrons in 2 isolates (1.1%). The identified antimicrobial resistance genes within class 1 integrons were dihydrofolate reductase types: dfrA1, dfrA12, dfrA15 and dfrA17, which confer resistance to trimethoprim; aminoglycoside adenyltransferase types: aadA1, aadA2, aadA5, aadA7 and aadA23, which confer resistance to streptomycin and spectinomycin; and aminoglycoside acetyltransferase gene, aac(3)-Id, which confers resistance to gentamicin and sisomicin. Furthermore, many β-lactamases encoding genes, plasmid-mediated quinolone resistance genes and florfenicol resistance gene were identified in this study. To the best of our knowledge, this is the first report for molecular characterization of antimicrobial resistance in E. coli isolated from diarrheic neonatal calves in Africa.