Biomedical subjects

C L Hofacre

Publications and source records attributed to C L Hofacre.

At least 19 recordsLinked to original sources

PubMed2006

Impact of antimicrobial usage on antimicrobial resistance in commensal Escherichia coli strains colonizing broiler chickens.

Escherichia coli strains isolated from commercial broilers and an experimental flock of chickens were screened to determine phenotypic expression of antimicrobial resistance and carriage of drug resistance determinants. The goal of this study was to investigate the influence of oxytetracycline, sarafloxacin, and enrofloxacin administration on the distribution of resistance determinants and strain types among intestinal commensal E. coli strains isolated from broiler chickens. We detected a high prevalence of resistance to drugs such as tetracycline (36 to 97%), sulfonamides (50 to 100%), and streptomycin (53 to 100%) in E. coli isolates from treated and untreated flocks. These isolates also had a high prevalence of class 1 integron carriage, and most of them possessed the streptomycin resistance cassette, aadA1. In order to investigate the contribution of E. coli strain distribution to the prevalence of antimicrobial resistance and the resistance determinants, isolates from each flock were DNA fingerprinted by enterobacterial repetitive intergenic consensus sequence (ERIC) PCR. Although very diverse E. coli strain types were detected, four ERIC strain types were present on all of the commercial broiler farms, and two of the strains were also found in the experimental flocks. Each E. coli strain consisted of both susceptible and antimicrobial agent-resistant isolates. In some instances, isolates of the same E. coli strain expressed the same drug resistance patterns although they harbored different tet determinants or streptomycin resistance genes. Therefore, drug resistance patterns could not be explained solely by strain prevalence, indicating that mobile elements contributed significantly to the prevalence of resistance.

Animals↗

PubMed2005

Presence of Campylobacter jejuni in various organs one hour, one day, and one week following oral or intracloacal inoculations of broiler chicks.

Day-old broiler chicks (n=30) were obtained from a commercial hatchery and inoculated, either orally or intracloacally, with a characterized strain of Campylobacter jejuni. At 1 hr, 1 day, and 1 wk after inoculation, broilers (n = 5) from the orally and intracloacally inoculated groups along with control birds (n=4) were humanely killed by cervical dislocation. The broilers from the control and treatment groups were aseptically opened, and the thymus, spleen, liver/gallbladder, bursa of Fabricius, and ceca were aseptically removed and individually analyzed for C. jejuni. Overall, C. jejuni was isolated after oral inoculation from 13% (10/ 75), 17% (13/75), and 28% (14/50) of the 1-hr, 1-day, and 1-wk samples, respectively. Campylobacter jejuni was isolated from 10% (4/ 40), 8% (3/40), 10% (4/40), 25% (10/40), and 40% (16/40) of the thymus, spleen, liver/gallbladder, bursa of Fabricius, and ceca samples, respectively. Following the intracloacal route of inoculation, C. jejuni was recovered from 32% (24/75), 8% (6/75), and 16% (8/50) of the 1-hr, 1-day, and 1-wk samples, respectively. Campylobacter jejuni was isolated from 5% (2/40), 5% (2/40), 5% (2/40), 45% (18/40), and 40% (16/40) of the thymus, spleen, liver/gallbladder, bursa of Fabricius, and ceca samples, respectively, for all sampling periods. Campylobacter spp. were not recovered from sample sites examined from the control broilers from trial one, trial two, or trial three samples examined after 1 hr and 1 day. However, one control sample was positive from the 1-wk sampling from repetition three; therefore, those data were omitted. The rapid movement of Campylobacter to internal organs following both oral and intracloacal inoculation may be significant, particularly if it persists in these organs as reservoirs throughout the 65-wk life cycle of breeding birds.

Animals↗

PubMed2000

Elimination of early Salmonella enteritidis infection after treatment with competitive-exclusion culture and enrofloxacin in experimentally infected chicks.

The effect of normal avian gut flora (NAGF) and enrofloxacin administration on the early infection of young chicks by Salmonella enteritidis (SE) was determined using day-old White Leghorn chicks. Day- old chicks were divided into two groups, untreated control and NAGF-treated, and then infected with 10(6) cfu of SE per chick by oral gavage. The untreated, infected chicks were further divided into two groups and were either left untreated or medicated with a regimen of 10 mg/kg of enrofloxacin in drinking water daily for 10 d, followed by two doses of NAGF beginning at 10 and 8 wk of age in Trial 1 and Trial 2, respectively. Liver, spleen, and cecum samples were tested for the presence of SE, and immunological responsiveness was investigated up to 12 wk of age. Compared with the untreated group, the cecal colonization of SE was significantly (P < 0.05) decreased in the NAGF-treated group in Trials 1 and 2. No significant differences in organ infection were observed in the NAGF-treated vs. untreated birds. Although a significant effect of the combined treatment of enrofloxacin treatment and NAGF on the early infection was not shown in Trial 1, compared with enrofloxacin only or the untreated group, a significant reduction (P < 0.05) in the number of infected chickens and in the number of SE in the cecal contents was observed at 10 wk of age in Trial 2. The enrofloxacin treatment did not increase opportunistic colonization by SE due to the use of the antibiotic in either trial. The plasma and intestinal immunological responses were not significant at the early age (up to 12 wk) of the birds. The use of enrofloxacin, followed by NAGF, could aid the elimination of SE from young chicks persistently infected at an early age. The combined treatment, compared with enrofloxacin alone, protected chickens from reinfection by 40%.

Animals↗

PubMed2000

Combined effect of antibiotic and competitive exclusion treatment on Salmonella enteritidis fecal shedding in molted laying hens.

Salmonella Enteritidis is an important pathogen for the layer industry, primarily because of its ability to infect hens and ultimately contaminate egg contents. Studies have shown that stress situations, such as flock recycling (induced molting), can increase Salmonella Enteritidis problems in the flock. The present study examined the effect of antibiotic treatment and competitive exclusion (CE) on Salmonella Enteritidis shedding in the period following molt and 14-day feed withdrawal. In two separate trials, 48 birds after molt and feed withdrawal were divided into one group that was treated for 10 days with enrofloxacin in water followed by administration of CE culture and a group that was left untreated. Salmonella Enteritidis shedding was significantly reduced in the antibiotic-CE group. The Salmonella Enteritidis shedding rate was 33 and 25% in untreated birds versus 4 and 0% in the enrofloxacin-CE group on the two test days. These results indicate that treatment of Salmonella Enteritidis-positive laying hens after molting with enrofloxacin and CE culture can substantially reduce Salmonella Enteritidis problems due to molting and would be a possible alternative to diverting eggs for pasteurization or slaughtering the infected flock. Possible development of bacterial resistance in conjunction with antibiotic use is also discussed.

Animals↗

PubMedDate not supplied

Hypoglycemia spiking mortality syndrome in broilers with rickets and a subsequent investigation of feed restriction as a contributing factor.

Several cases of elevated mortality with neurologic signs in 14-to-16-day-old broilers were presented to the Poultry Diagnostic and Research Center from one local integrated company. Suspected of "spiking mortality" associated with hypoglycemia, blood glucose levels were <150 mg/dl overall, with several birds with blood glucose levels as low as 30 mg/dl. Tissues, submitted for histopathology, revealed rickets in 50% of the birds. Virus isolation and serology for reovirus and infectious bursal disease virus were negative. After evaluation of these cases, a brief investigation was conducted to determine the effects of feed restriction on the induction of rickets and resulting hypoglycemia. One-hundred 1-day-old broilers were randomly assigned to three treatment groups of: 1) ad libitum feed, 2) 25% restriction, and 3) 50% restriction. Restriction began on the fifth day of age and continued to 21 days of age. Samples collected during the course of the study included whole blood for blood glucose measurements and proximal tibiotarsus for histopathologic examination for rickets. We were unable to reproduce the clinical signs of spiking mortality, neurologic changes, or hypoglycemia experimentally. Histopathology of the growth plates of the proximal tibiotarsus did indicate mild changes consistent with rickets, but the changes were not significant between treatment groups.

Animal Feed↗

PubMedDate not supplied

Effect of an electrostatic space charge system on airborne dust and subsequent potential transmission of microorganisms to broiler breeder pullets by airborne dust.

High levels of dust and microorganisms are known to be associated with animal confinement rearing facilities. Many of the microorganisms are carried by dust particles, thus providing an excellent vector for horizontal disease transmission between birds. Two environmentally controlled rooms containing female broiler breeder pullets (n = 300) were used to evaluate the effectiveness of an electrostatic space charge system (ESCS) in reducing airborne dust and gram-negative bacteria levels over an 8-wk period (starting when the birds were 10 wk old). The ESCS was used to evaluate the effectiveness of reducing airborne microorganism levels by charging airborne dust particles and causing the particles to be attracted to grounded surfaces (i.e., walls, floor, equipment). The use of the ESCS resulted in a 64% mean reduction in gram-negative bacteria. Airborne dust levels were reduced an average of 37% over a 1-wk period in the experimental room compared with the control room on the basis of samples taken every 10 min. The reductions of airborne dust and bacteria in this study are comparable with earlier results obtained with the ESCS in commercial hatching cabinets and experimental caged layer rooms, suggesting the system could also be applied to other types of enclosed animal housing.

Air Microbiology↗

PubMedDate not supplied

Effect of electrostatic space charge on reduction of airborne transmission of Salmonella and other bacteria in broiler breeders in production and their progeny.

Salmonella in birds is a concern because of the human foodborne illness associated with the consumption of poultry meat and eggs. One of the methods of transmission of Salmonella within a flock can be by the air. Therefore, we used reduction of transmission of Salmonella to monitor the effectiveness of the electrostatic space charge system (ESCS). During the average broiler breeder laying cycle of 40 wk, a large amount of dust becomes airborne and accumulates on walls, ceiling, and equipment. Many microorganisms adhere to these dust particles, making dust an excellent vector for horizontal disease transmission between birds. We used two environmentally controlled rooms containing commercial broiler breeders to evaluate the effectiveness of an ESCS that produced a strong negative electrostatic charge to reduce airborne dust and, subsequently, microorganism levels. The ESCS caused the dust to become negatively charged, therefore moving to the grounded floor in the treatment room. The use of the ESCS resulted in a significant reduction (P < 0.0001, 61% reduction) in airborne dust concentration levels, which resulted in a significant reduction (P < 0.0001, 76% reduction) in total airborne bacteria and gram-negative bacteria (48% reduction) in the treatment room. Significant reductions (P < 0.05) of gram-negative bacteria (63% reduction) on the egg collection belts were also recorded in the treatment room, which resulted in a significant reduction (P < 0.0001) of gram-negative bacteria (28% reduction) on the eggshell surface. The ESCS treatment resulted in fewer Salmonella enteritidis-positive hens and their progeny from the treatment room due to reductions of dust and airborne bacteria. In addition, this significant reduction in bacteria on the eggshell surface should result in less bacteria in the day-old chicks, therefore better early chick livability. There was no significant difference (P > 0.05) in egg production, male or female body weights, mortality, or reproductive performance in the ESCS room compared with the control room.

Air Microbiology↗

PubMedDate not supplied

Presence of fluoroquinolone-resistant coliforms in poultry litter.

Litter was collected from four turkey farms (eight houses) with a history of fluoroquinolone (FQ) treatment failure, 10 adult broiler breeder chicken farms (43 houses) with one having a history of FQ treatment, and 30 broiler chicken farms (110 houses) with 24 having a history of FQ treatment. In the turkey litter, the percentage of nalidixic acid-resistant (at 100 microg/ml) coliforms/total number of coliforms ranged from 0.6% to 61.9%. Two of the four farms had houses containing coliforms resistant to the two FQs, enrofloxacin (1 microg/ml) and sarafloxacin (1 microg/ml). There was also multiple resistance to other antimicrobials on all four turkey farms (ampicillin, tetracycline, chloramphenicol, kanamycin). The level of total coliforms from the adult broiler breeder litter was low, and there were no nalidixic acid-resistant isolates from any of the 10 farms. In the broiler chickens, 7 of 91 houses with a history of FQ usage contained coliforms resistant to nalidixic acid; however, 2 of the 19 houses on farms with no history of FQ usage had nalidixic acid-resistant coliforms. All of the broiler farms with nalidixic acid-resistant isolates were also resistant to the FQ sarafloxacin, whereas only 3 of the 24 treatment history farms and 1 of the no-treatment history farms exhibited enrofloxacin-resistant coliforms in the litter.

Animal Husbandry↗

PubMedDate not supplied

Monitoring Mycoplasma gallisepticum and Mycoplasma synoviae infection in breeder chickens after treatment with enrofloxacin.

Three experimental strains of breeder chickens were accidentally exposed to Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS), presumably from a newly introduced group of leghorn-type pullets. The experimental strains subsequently became infected and were diagnosed positive for MG and MS by the serum plate agglutination (SPA) test and confirmed by the hemagglutination inhibition (HI) test and the polymerase chain reaction (PCR) of tracheal swabs. Treatment with 10 mg/kg enrofloxacin via drinking water for 14 days was elected. Before and after initiation of treatment, MG and MS were monitored for changes by SPA, HI, PCR, and culture, with sampling intervals ranging from 1 wk to 7 wk. MG and MS SPA, HI, PCR, and culture were performed at each sampling period, with the exception of weeks 1.0 and 6.5. Week 1.0 included SPA and His for MG and MS. Week 6.5 included PCR and culture for MG and MS. The MG and MS SPA results were positive throughout the 29-wk trial period. MG HI titers declined until the last sampling, whereas the MS HI titers did not decline significantly. PCR for MG yielded only one positive result, which occurred before treatment. MS PCR remained positive throughout the trial period. MG was never isolated from any sample; however, one MS organism was isolated during treatment. The treatment regimen was effective for MG on the basis of PCR results. Treatment with enrofloxacin did not eliminate SPA reactions during the 29-wk trial period. MG HI titers remained in the suspicious range throughout the remainder of the trial period. Four weeks after the treatment ended, MG HIs were reduced by approximately 40%, with MS HIs remaining high throughout the 29-wk period. PCR appeared to be a sensitive and specific test on the basis of correlation with HIs. On the basis of the isolation of MS during treatment and continued subsequent PCR positive reactions, the treatment for MS with enrofloxacin was not as efficacious as for MG.

Agglutination Tests↗

PubMedDate not supplied

Characterization of antibiotic-resistant bacteria in rendered animal products.

Antibiotics are used in food animal production to treat diseases and also to improve performance. Antibiotics are not used on all farms, and antibiotic resistance is occasionally found on farms that do not use antibiotics. Rendered animal protein products are often included in poultry feeds and could potentially serve as a source of antibiotic-resistant bacteria. One hundred sixty-five rendered animal protein products from cattle, poultry, and fish were aseptically collected from poultry feed mills. Fifty-five percent of the poultry meal samples had detectable levels of gram-negative bacteria ranging from 40 to 10,440 colony-forming units/g of sample. Poultry meal and meat and bone meal had the greatest number of samples with bacteria resistant to five or more antibiotics. A high percentage of feed samples (85%) contained bacteria resistant to amoxicillin, ampicillin, clavulanic acid, or cephalothin, whereas few samples contained bacteria resistant to ciprofloxacin, kanamycin, or trimethoprim/sulfamethoxazole. Acinetobacter calcoaceticus, Citrobacter freundii, and Enterobacter cloacae were the most commonly isolated antibiotic-resistant bacteria. Isolation for Salmonella was also performed, with 14% of the meat and bone meal samples containing Salmonella sp. Only one of the meat and bone meal isolates, Salmonella livingstone, was resistant to five or more antibiotics. Many of the antibiotic-resistant bacteria contained integrons, genetic elements that mediate multiple drug resistance.

Animal Feed↗

PubMedDate not supplied

A small round virus associated with enteritis in turkey poults.

In a natural outbreak of enteric disease in turkey poults, Salmonella, group D rotavirus, astrovirus, and a small (18-24 nm) round virus were detected in the gut contents. Except for the small virus, the pathogenic potential of the other agents is recognized. In experiments, the small round virus was shown to be transmissible and pathogenic in specific-pathogen-free turkey poults.

Animals↗

PubMedDate not supplied

Evaluation of Pasteurella multocida mutants of low virulence. I. Development and pathogenicity.

Mutagenesis of the Clemson University (CU) vaccine strain of Pasteurella multocida with N-methyl-N-nitro-N-nitrosoguanidine resulted in temperature-sensitive mutants that grew at 37 C but not at 42 C. Seven such mutants were evaluated for immunogenicity in turkeys. From these seven, only two, PM#1 and PM#3, provided turkeys with a level of protection against challenge with a virulent serotype 3 P. multocida strain (P-1059) comparable to the protection provided by the CU strain. Intravenous (IV) inoculation of PM#1, PM#3, or CU was used to assess differences in virulence. PM#1 and PM#3 resulted in lower rates of mortality and lameness than the CU strain. Histopathological evaluation of spleens 24, 48, and 72 hours after IV inoculation demonstrated that the CU strain induced significantly more fibrinoid necrosis of the spleen than either PM#1 or PM#3.

Animals↗

PubMedDate not supplied

Evaluation of Pasteurella multocida mutants of low virulence. II. Immunologic response of turkeys.

Vaccination of turkeys by administering Pasteurella multocida mutant PM#1 or PM#3, either by the oculo-nasal-oral method or in the drinking water, induced a level of protection comparable to vaccination with the Clemson University (CU) strain or the M-9 vaccine. The level of protection was not altered when PM#1, PM#3, or the CU strain was grown in brain-heart infusion (BHI) broth or BHI agar. Under extremely severe challenges, the CU strain provided a greater level of protection than PM#1, PM#3, or the M-9 vaccine. It also was apparent from this study that the less-virulent mutant organisms and the M-9 vaccine require a higher concentration of organism per vaccine dose than the CU strain to provide similar protection.

Animals↗

PubMedDate not supplied

Necrotic enteritis in cage-reared commercial layer pullets.

Necropsy of five 12-week-old pullets from a flock of 99,300 suffering from an increased mortality rate revealed enlarged, gas-filled intestines, the mucosal surfaces of which had the "dirty turkish towel" appearance typical of necrotic enteritis. Although the pullets had been raised entirely in cages, intestinal scrapings revealed the presence of Eimeria maxima. Histopathological findings were compatible with necrotic enteritis. Clostridium perfringens was isolated by anaerobic culture from the intestines. Mortality returned to normal after bacitracin and amprolium were added to the feed.

Animal Husbandry↗

PubMedDate not supplied

Subcutaneous clostridial infection in broilers.

A flock of 12,500 broilers 36 days of age experienced a sudden increase in mortality. Post-mortem lesions were emphysema, severe enteritis, and a serosanguineous fluid in the subcutaneous tissue of the breast and thighs; there was no evidence of a loss in the integrity of the skin. Clostridium perfringens and C. septicum were isolated from the affected subcutaneous tissue. Histopathological and serological examination indicated previous infection with infectious bursal disease virus. The subsequent immunosuppression and severe enteritis may have permitted the clostridia access to the circulatory system, with localization in the subcutaneous areas of the breast and thighs. Mortality returned to normal 48 hours after potassium penicillin G was administered via the drinking water.

Animals↗

PubMedDate not supplied

Comparison of vaccination protocols of broiler breeder hens for Pasteurella multocida utilizing enzyme-linked immunosorbent assay and virulent challenge.

A commercial enzyme-linked immunosorbent assay (ELISA) to detect serological response to vaccination and virulent challenge with type 1 (X-73) Pasteurella multocida was used to determine the best vaccination protocol for broiler breeders against fowl cholera. Birds vaccinated twice, at 10 and 19 weeks of age, with the avirulent Clemson University (CU) strain both times, with a commercial bacterin first and the CU strain second, or with the CU strain first and bacterin second had the highest survival rates (98-100%) following challenge at 25 weeks. The two groups that received the CU strain and bacterin also produced the highest mean ELISA antibody titers (greater than 10,000). Birds vaccinated once, at 10 weeks, with the CU strain had the same survival rate as birds vaccinated twice with bacterin (90 and 91%). Under the conditions of this experiment, an ELISA titer greater than or equal to 1000 resulted in at least a 92% survival rate after virulent challenge (23% survival in nonvaccinates).

Animals↗

PubMedDate not supplied

Newcastle disease vaccination of broilers with high- and low-titered commercial vaccines.

The virus titers of seven commercial B1 strain Newcastle disease vaccines were evaluated. A 2 log difference in virus content was found between the vaccine with the highest titer (10(8.8) EID 50/ml) and the one with the lowest titer (10(6.8) EID 50/ml). Broiler chickens were vaccinated with the high- and low-titered vaccines to compare hemagglutination-inhibition (HI) antibody and challenge responses. The effect of vaccination at different ages on the HI titers was also examined. There were no significant differences between vaccine groups in HI antibody response or resistance to challenge. However, the high-titered vaccine may provide a margin of safety with the currently used methods of mass vaccination.

Animals↗

PubMedDate not supplied

A serotypic survey of Pasteurella multocida isolated from poultry.

One hundred forty-eight Pasteurella multocida isolates from four southeastern states and California were serotyped by a gel diffusion precipitin test. The isolates were predominantly from turkeys and chickens. Sixty-eight percent of the isolates had antigenic characteristics of serotypes 3 and 4 (3 X 4). In turkeys, 76% of the isolates were 3 X 4, and serotype 3 was second (17%) in frequency. In chickens, 54% of the isolates were 3 X 4 and 19% were serotype 1.

Animals↗