Diagnostic Evidence of Staphylococcus Warneri as a Possible Cause of Bovine Abortion

Following a routine necropsy of a bovine fetus aborted at 5 months of gestation, placenta, fetal tissue samples, and stomach contents were subjected to a number of laboratory tests. Staphylococcus warneri was isolated in pure culture from the lung, liver, and stomach contents, whereas the placenta yielded S. warneri and a number of contaminants. Gross evaluation of agar plates showed predominant colonies to be morphologically consistent with those of S. warneri and the identity of the agent was further confirmed on a Trek Diagnostic Systems Sensititre, gram-positive identification (GPID) plate. Microscopic evaluation of fetal tissue sections showed extensive necrotizing lesions of the tongue, lung, and placenta in which there were numerous coccoid shaped gram-positive bacteria with morphology consistent with Staphylococcus spp. These results provide strong diagnostic evidence of S. warneri as a possible cause of bovine abortion and suggest there should be further investigations into the abortivirulence of this agent.

Molecular analysis of porin gene transcription in heterogenotypic multidrug-resistant Escherichia coli isolates from scouring calves

BACKGROUND

Despite evidence that altered membrane porins may impair microbial drug uptake thereby potentially compounding efflux pump-mediated multidrug resistance, few studies have evaluated gene transcription to identify multidrug-resistance-associated porins and other potential drug targets.

METHODS

Genes that encode six membrane porins (fadL, lamB, ompC, ompF, ompW and yiaT) and two membrane proteins (tolC and ompT) were assessed by PCR and by quantitative real-time PCR (qRT-PCR) analysis of 10 multidrug-resistant (MDR) and 10 antibiotic-susceptible (AS) Escherichia coli isolates. The mean DeltaDeltaCt values for the study E. coli genes were analysed by the Wilcoxon test (P = 0.05).

RESULTS

All 20 E. coli isolates tested positive for tolC, lamB, ompC, ompF genes, while 10 MDR and 9/10 (90%) AS isolates were positive for the fadL gene. Seven out of 10 (70%) MDR and 7/10 (70%) AS isolates were positive for the yiaT gene, while 7/10 (70%) MDR and only 4/10 (40%) AS isolates were positive for the ompT gene. The mean DeltaDeltaCt values for the tolC and yiaT genes were significantly higher in MDR than in AS isolates (Wilcoxon test; P < 0.05). No significant difference was seen with respect to fadL, lamB, ompC, ompF, ompT and ompW gene transcription (Wilcoxon test; P > 0.05).

CONCLUSIONS

Findings suggest up-regulated transcription of tolC and yiaT genes in the MDR E. coli isolates. These results indirectly suggest that TolC and YiaT proteins may play some role(s) in multidrug resistance, but proteomic studies are needed before the two proteins are considered potential drug targets.

Comparative effect of direct-fed microbials on fecal shedding of Escherichia coli O157:H7 and Salmonella in naturally infected feedlot cattle

The effect of direct-fed microbials (DFM) on fecal shedding of Escherichia coli O157:H7 and Salmonella in naturally infected feedlot cattle was evaluated in a clinical trial involving 138 feedlot steers. Following standard laboratory methods, fecal samples collected from steers were evaluated for change in the detectable levels of E. coli O157:H7 and Salmonella shed in feces after DFM treatment. Sampling of steers was carried out every 3 weeks for 84 days. A significant reduction (32%) in fecal shedding of E. coli O157:H7 (P < 0.001), but not Salmonella (P = 0.24), was observed among the treatment steers compared with the control group during finishing. The probability of recovery of E. coli O157:H7 from the feces of treated and control steers was 34.0 and 66.0%, respectively. Steers placed on DFM supplement were almost three times less likely to shed E. coli O157:H7 (odds ratio, 0.36; 95% confidence interval, 0.25 to 0.53; P < 0.001) in their feces as opposed to their control counterparts. The probability of recovery of Salmonella from the feces of the control (14.0%) and the treated (11.3%) steers was similar. However, the DFM significantly reduced probability of new infections with Salmonella among DFM-treated cattle compared with controls (nontreated ones). It appears that DFM as applied in our study are capable of significantly reducing fecal shedding of E. coli O157:H7 in naturally infected cattle but not Salmonella. The factors responsible for the observed difference in the effects of DFM on E. coli O157:H7 and Salmonella warrants further investigation.

Pleiotropic phenotypes of a Yersinia enterocolitica flhD mutant include reduced lethality in a chicken embryo model

Background

The Yersinia enterocolitica flagellar master regulator FlhD/FlhC affects the expression levels of non-flagellar genes, including 21 genes that are involved in central metabolism. The sigma factor of the flagellar system, FliA, has a negative effect on the expression levels of seven plasmid-encoded virulence genes in addition to its positive effect on the expression levels of eight of the flagellar operons. This study investigates the phenotypes of flhD and fliA mutants that result from the complex gene regulation.

Results

Phenotypes relating to central metabolism were investigated with Phenotype MicroArrays. Compared to the wild-type strain, isogenic flhD and fliA mutants exhibited increased growth on purines and reduced growth on N-acetyl-D-glucosamine and D-mannose, when used as a sole carbon source. Both mutants grew more poorly on pyrimidines and L-histidine as sole nitrogen source. Several intermediates of the tricarboxylic acid and the urea cycle, as well as several dipeptides, provided differential growth conditions for the two mutants. Gene expression was determined for selected genes and correlated with the observed phenotypes. Phenotypes relating to virulence were determined with the chicken embryo lethality assay. The assay that was previously established for Escherichia coli strains was modified for Y. enterocolitica. The flhD mutant caused reduced chicken embryo lethality when compared to wild-type bacteria. In contrast, the fliA mutant caused wild-type lethality. This indicates that the virulence phenotype of the flhD mutant might be due to genes that are regulated by FlhD/FlhC but not FliA, such as those that encode the flagellar type III secretion system.

Conclusion

Phenotypes of flhD and fliA mutants are related to central metabolism and virulence and correlate with gene regulation.

Identification, antimicrobial resistance profiles, and virulence of members from the family Enterobacteriaceae from the feces of yellow-headed blackbirds (Xanthocephalus xanthocephalus) in North Dakota

Public pressure to reduce or eliminate antimicrobials as ingredients of feed for poultry and other agricultural animals is mounting, primarily due to the fear of multidrug-resistant bacteria in clinical infections in both animals and humans. Exploration of the occurrence of antibiotic resistance in the gut flora of wildlife avian flocks that presumptively do not receive antimicrobials will determine the rate of resistance in a naïve population. Fecal samples collected from a healthy population of the yellow-headed blackbirds (YHB) (Xanthocephalus xanthocephalus) in North Dakota were cultured to determine what genera and species of gram-negative facultative anaerobic bacteria these wild birds carry in their intestinal flora and to evaluate the antimicrobial susceptibility profiles. Isolates of Escherichia coli were further characterized for the presence of putative virulence factors and for pathogenic potential using the chicken embryo lethality assay (ELA). The ELA was performed in chicken embryos with challenges at both 12 days and 16 days of incubation to determine whether the 16-day-old embryos were better able to fight the infection and subsequent disease and also to determine whether the ELA could distinguish between primary and secondary avian Escherichia coli pathogens. After screening 33 isolates from the 21 fecal samples, only two E. coli isolates were identified. The predominant genus and species of bacterium identified was Pantoea agglomerans. Collectively, 12 of the 33 isolates (36%) exhibited no resistance to any antimicrobial tested. However, several multidrug-resistant isolates of varying genera were identified. Among the antimicrobial resistances observed, the most common was to ampicillin (60%), followed by cephalothin (33%). Neither E. coli isolate belonged to serogroups that are notorious for causing major outbreaks of colibacillosis in poultry, and only one E. coli isolate retained resistance to any antibiotics; nevertheless, the ELA results indicate that at least one of these E. coli may be a primary pathogen of chickens. This study demonstrates that antibiotic resistance occurs in the gut flora of natural populations of YHB despite the absence of antibiotic pressure. In addition, these results indicate that YHB will harbor E. coli isolates that are potentially pathogenic in poultry. However, these E. coli isolates are not a significant reservoir for multiple antibiotic resistances nor are they widespread in the population of YHB surveyed in North Dakota.

A longitudinal study of Salmonella shedding and antimicrobial resistance patterns in North Dakota feedlot cattle

Salmonella is one of the most frequent causes of foodborne illness worldwide, and transmission involves foods of animal origin such as beef. The objective of this study was to monitor the prevalence of Salmonella fecal shedding in feedlot cattle during the finishing period and to assess the antimicrobial resistance patterns of the isolated salmonellae. On arrival at the feedlot, 1 (0.7%) of the 144 steers was shedding Salmonella in its feces. After 28 days on feed, shedding was detected in 8 (5.6%) of the 144 steers. At the third sampling, 19 (13%) of 143 steers were shedding, and the number of shedders continued to increase to 89 (62%) of 143 at the last sampling. Salmonella shedding was significantly influenced (P < 0.0001) by sampling time but not by herd of origin. All Salmonella isolates identified belonged to serotype Typhimurium serovar Copenhagen, a type commonly isolated from Salmonella infections in humans. Antimicrobial resistance testing of the isolates revealed five multidrug resistance patterns, two of which accounted for 104 (95.4%) of 109 of the isolates. All the isolates were susceptible to ceftiofur, and all were resistant to spectinomycin, sulfathiazole, tiamulin, florfenicol, ampicillin, penicillin, chlortetracycline, oxytetracycline, and clindamycin. Data from this study indicate that a high prevalence of antimicrobial-resistant Salmonella strains can sometimes be found in feedlot cattle in North Dakota. These data will contribute to risk assessment of Salmonella shedding by cattle in feedlots and highlight the need to continue preharvest monitoring for this organism.

Fecal shedding of Escherichia coli O157:H7 in North Dakota feedlot cattle in the fall and spring

Cattle are an important reservoir of Escherichia coli O157:H7, which can lead to contamination of food and water, and subsequent human disease. E. coli O157:H7 shedding in cattle has been reported as seasonal, with more animals shedding during summer and early fall than during winter. North Dakota has relatively cold weather, especially in winter and early spring, compared with many other regions of the United States. The objective was to assess fecal shedding of E. coli O157:H7 in North Dakota feedlot cattle over the fall, winter, and early spring. One hundred forty-four steers were assigned randomly to 24 pens on arrival at the feedlot. Samples of rectal feces were obtained from each steer four times (October and November 2003, and March and April 2004) during finishing. On arrival (October 2003), 2 (1.4%) of 144 cattle were shedding E. coli O157:H7. The shedding increased significantly to 10 (6.9%) of 144 after 28 days (November 2003), to 76 (53%) of 143 at the third sampling (March 2004), and dropped significantly to 30 (21%) of 143 at the fourth (last) sampling (March 2004) before slaughter. Unfortunately, we were unable to sample the cattle during winter because of the extreme weather conditions. Sampling time significantly (P < 0.0001) influenced variability in E. coli O157:H7 shedding, whereas herd (P = 0.08) did not. The prevalence of E. coli O157:H7 shedding in North Dakota steers in fall and early spring was comparable to what has been reported in other parts of the United States with relatively warmer weather. Further research into E. coli O157:H7 shedding patterns during extreme weather such as North Dakota winters is warranted in order to fully assess the seasonal effect on the risk level of this organism.

Comparison of two sampling methods for Escherichia coli O157:H7 detection in feedlot cattle

Two sampling methods (rectoanal swabs and rectal fecal grabs) were compared for their recovery of Escherichia coli O157:H7 from feedlot cattle. Samples were collected from 144 steers four times during the finishing period by swabbing the rectoanal mucosa with cotton swabs and immediately obtaining feces from the rectum of each individual steer. The number of steers with detectable E. coli O157:H7 increased from 2 of 144 (1.4%) cattle on arrival at the feedlot to 10 of 144 (6.9%) after 1 month, 76 of 143 (52.8%) after 7 months, and 30 of 143 (20.8%) at the last sampling time before slaughter. Wilcoxon signed-rank tests indicated that the two sampling methods gave different results for sampling times 3 and 4 (P < 0.05) but not for sampling time 2 (P = 0.16). Agreement between the two sampling methods was poor (kappa < 0.2) for three of the four sampling times and moderate (kappa = 0.6) for one sampling time, an indication that in this study rectoanal swabs usually were less sensitive than rectal fecal grabs for detection of E. coli O157:H7 in cattle. Overall, the herd of origin was not significantly associated with E. coli O157:H7 results, but the weight of the steers was. Further investigation is needed to determine the effects of potential confounding factors (e.g., size and type of swab, consistency of feces, site sampled, and swabbing technique) that might influence the sensitivity of swabs in recovering E. coli O157:H7 from the rectoanal mucosa of cattle.

Comparison of several challenge models for studies in avian colibacillosis

In previous studies, the embryo lethality assay (ELA) discriminated between virulent and avirulent avian Escherichia coli isolates, and also proved to be highly correlated with mortality and morbidity results of the intravenous (IV) challenge model. In the current study, the same 20 avian E. coli isolates were used in subcutaneous (subQ) and intratracheal (IT) chicken challenge models in order to determine whether the results from the prior ELA challenges and/or the IV challenge model correlate with these models. The correlation observed between the two previous ELA trials and the combined mortality/morbidity percentages of the subQ challenge model were r = 0.792, P > 0.0001 for the first ELA trial and r = 0.738, P = 0.0002 for the second ELA trial. The IV challenge results were more highly correlated with the subQ challenge results (mortality/morbidity comparison, r = 0.894, P < 0.0001). The IV challenge mortality results were slightly correlated (r = 0.4810, P=0.0319) with the IT challenge results. Several of the isolates differed in their ability to produce mortality and/or morbidity with the different challenge models. The mortality/morbidity results of the IV and subQ challenges and the mortality results of the ELA were all positively correlated with the ability of an E. coli isolate to produce Colicin V (ColV) (r = 0.7131, P = 0.0004). The IT mortality results were slightly correlated with the production of ColV (r = 0.455, P = 0.049). The IT challenge results were only slightly correlated with resulting IV mortality and ColV production. Previous results indicate that the ELA correlates extremely well with the IV challenge model. The current study demonstrates that ELA also correlates well with the subQ challenge model. Overall, the conclusion of this study is that the ELA, IV, and subQ challenge models similarly demonstrate the ability to discriminate between virulent and avirulent avian E. coli isolates.

Characterizing avian Escherichia coli isolates with multiplex polymerase chain reaction

Colibacillosis caused by Escherichia coli infections account for significant morbidity and mortality in the poultry industry. Yet, despite the importance of colibacillosis, much about the virulence mechanisms employed by avian E. coli remains unknown. In recent years several genes have been linked to avian E. coli virulence, many of which reside on a large transmissible plasmid. In the present study, a multiplex polymerase chain reaction (PCR) protocol to detect the presence of four of these genes is described. Such a protocol may supplement current diagnostic schemes and provide a rapid means of characterizing the E. coli causing disease in poultry. The targets of this procedure included iss, the increased serum survival gene; tsh, the temperature sensitive hemagglutinin gene; cvi, the ColV immunity gene; and iucC, a gene of the aerobactin operon. Organisms, known for their possession or lack of these genes, were used as a source of the template DNA to develop the multiplex PCR protocol. Identity of the amplicons was confirmed by size, DNA:DNA hybridization with specific gene probes, and DNA sequencing. When the multiplex PCR protocol was used to characterize 10 E. coli isolates incriminated in avian colibacillosis and 10 from the feces of apparently healthy birds, nine of the isolates from apparently healthy birds contained no more than one gene, while the 10th contained all four. Also, eight of the isolates incriminated in colibacillosis contained three or more genes, while the remaining two contained two of the target genes. Interestingly, the isolates of sick birds containing only two of the targeted genes killed the least number of embryos,and the isolate of healthy birds that contained all the genes killed the most embryos amongthis group. These genes were not found among the non-E. coli isolates tested, demonstrating the procedure's specificity for E. coli. Overall, these results suggest that this protocol might be useful in characterization and study of avian E. coli.

Comparison of the Intravenous Chicken Challenge Method with the Embryo Lethality Assay for Studies in Avian Colibacillosis

In previous studies, the embryo lethality assay (ELA) was able to discriminate between virulent and avirulent avian Escherichia coli isolates and to predict percent mortality of the embryos resulting from an isolate based on three traits. The abilities to resist host complement, presence of Colicin V activity, and presence of the increased serum survival gene cluster (iss), were used together in a logistic regression analysis to predict the percentage of embryo deaths resulting from each of 20 avian E. coli isolates used in the ELA. In the present study, the same 20 isolates are used in an intravenous chicken challenge model in an effort to determine whether the ELA could be used to replace chicken challenge studies. Correlations between the mortality and a combination of mortality and morbidity (the survivors at trial termination with lesions suggestive of colibacillosis) and the previous ELA results and with selected isolate traits were performed. Additionally, resulting body weights in surviving chickens were compared between groups. The highest positive correlations were observed between the ELA and the combined mortality/morbidity of the intravenous challenge (r = 0.861, P < 0.0001 for the first ELA challenge, and r = 0.830, P < 0.0001 for the second ELA challenge). The IV challenge combined mortality/morbidity results had the highest correlation coefficients with the presence of iss (r = 0.864, P < 0.0001) and the expression of ColV (r = 0.878, P < 0.0001). The presence of tsh was slightly correlated with mortality (r = 0.465, P = .0389) but demonstrated a higher correlation with the combined mortality and morbidity of the IV challenge (r = 0.558, P = 0.0106). Even though the ELA results in a higher number of nonspecific deaths, the two challenge methods exhibit similar results and a high correlation with each other. Interestingly, some of the isolates showed differences in their ability to cause mortality between the ELA and the IV challenge model. Furthermore, some isolates reflected significant differences in body weights of surviving birds at IV trial termination.

Prediction of chicken embryo lethality with the avian Escherichia coli traits complement resistance, colicin V production, and presence of the increased serum survival gene cluster (iss)

Differentiating between virulent and avirulent avian Escherichia coli isolates continues to be a problem for poultry diagnostic laboratories and the study of colibacillosis in poultry. The ability of a laboratory to conduct one simple test that correlates with virulence would simplify studies in these areas; however, previous studies have not enabled researchers to establish such a test. In this study, the occurrence of certain phenotypic and genotypic traits purported to contribute to avian E. coli virulence in 20 avian E. coli isolates was correlated with the results of embryo challenge studies. This analysis was undertaken in an effort to determine which trait(s) best identified each avian E. coli isolate as virulent or avirulent. Traits selected were complement resistance, production of colicin V (ColV), motility, type F1 pili expression, presence of the temperature-sensitive hemagglutinin gene (tsh), and presence of the increased serum survival genetic locus (iss). ColV production, complement resistance, and presence of the iss genetic element were the three traits most highly correlated with high embryo lethality. A logistic regression model was used to predict the embryo lethality results on the basis of the most frequent isolate characteristics. Results indicate that ColV, complement resistance, and if are significant predictor variables for the percentage of embryo lethality resulting from challenge with a specific avian E. coli isolate. However, no single trait has the ability to predict virulent isolates 100% of the time. Such results suggest the possibility that the embryo lethality assay may prove to be the one test needed to determine if an avian E. coli isolate is virulent.

Development of resistant bacteria isolated from dogs with otitis externa or urinary tract infections after exposure to enrofloxacin in vitro

Minimum inhibitory concentrations for enrofloxacin were determined for 63 bacterial isolates from dogs with otitis externa or urinary tract infections. Development of resistant mutants was determined after exposing the isolates to enrofloxacin in vitro for up to five serial passages. Results indicated that Pseudomonas aeruginosa and Enterococcus spp isolates exposed to enrofloxacin developed resistance rapidly, whereas Klebsiella, Proteus, and Streptococcus spp were less likely to develop resistance. Despite the presence of enrofloxacin pressure, no resistant bacteria developed in the Escherichia coli and staphylococcal isolates. In many isolates, susceptibility patterns changed from susceptible to intermediate.

Location of increased serum survival gene and selected virulence traits on a conjugative R plasmid in an avian Escherichia coli isolate

Avian colibacillosis is a costly disease for the poultry industry. The mechanisms of virulence employed by the etiologic agent of this disease remain ill defined. However, accumulated evidence suggests that complement resistance and the presence of the increased serum survival gene (iss) in an avian Escherichia coli isolate may be indicative of its ability to cause disease. This association of iss with the E. coli implicated in avian disease may mean that iss and/or, perhaps, the genes associated with it are important contributors to avian E. coli virulence. For this reason, we have begun a search for iss's location in the bacterial genome. Thus far, iss in an avian E coli isolate has been localized to a conjugative R plasmid and estimated to be about 100 kilobase (kb) in size, encoding resistance to tetracycline and ampicillin. Hybridization studies have revealed that this plasmid contains sequences with homology to tsh, a gene associated with virulence of avian E coli; intI 1, a gene encoding the integrase of Class 1 integrons; and certain genes of the aerobactin- and CoIV-encoding operons. Sequences homologous to merA, a gene of the mercury resistance operon, were not identified on this R plasmid. This plasmid, when transferred into an avirulent, recipient strain by conjugation, enhanced the transconjugant's resistance to complement but not its virulence, in spite of the plasmid's possession of several putative virulence genes and traits. Such results may reflect the multifactorial nature of virulence, the degree of the recipient's impairment for virulence, or an inability of the embryo assay used here to detect this plasmid's contribution to virulence. Additionally, this plasmid contains genes encoding antimicrobial resistances, which may provide a selective advantage to virulent E. coli in the production environment. Further study will be needed to determine whether this plasmid is widespread among virulent E. coli and to ascertain the implications that this link between virulence and antimicrobial resistance genes may have for poultry management.

Complement resistance, as determined by viable count and flow cytometric methods, and its association with the presence of iss and the virulence of avian Escherichia coli

Previous work in our labs has shown that avian Escherichia coli virulence is correlated with resistance to complement. Also, our studies have revealed that the presence of the increased serum survival gene (iss), known to contribute to the complement resistance and virulence of mammalian E. coli, may predict the virulent nature of an avian E. coli isolate. This relationship warrants further research, but further clarification of the relationship among virulence, complement resistance, and iss sequences requires use of complement susceptibility assays. Such assays, unfortunately, are labor-intensive, expensive, and difficult to perform. In the present study, the results of two complement susceptibility assays for 20 E. coli isolates, 10 incriminated in avian colibacillosis and 10 from the intestinal tracts of apparently healthy birds, were compared in an attempt to determine if flow cytometric analysis was a reasonable alternative to a viable count assay. In addition, the virulence of these isolates for chick embryos was determined, and each isolate was examined for the presence of iss using amplification techniques. The flow cytometric method was found to be repeatable for most isolates, and its results showed moderate agreement with those obtained through viable counts. All intestinal isolates of healthy birds proved avirulent using the embryo lethality assay; however, not all isolates from sick birds were demonstrated to be virulent. Possible explanations of these results include that the methods originally used to isolate these organisms failed to detect the illness-inciting strains or that the virulence of these strains had declined following initial isolation. Additionally, we must consider the possibility that the embryo lethality assay of virulence used here might not be sensitive enough to detect differences between these two groups of isolates. Also, it should be noted that virulence assays, such as the one used here, fail to account for predisposing host or environmental conditions, enabling a less virulent isolate to cause disease under natural conditions. Interestingly, the complement resistance of a strain was significantly associated with its lethality in embryos, and iss-containing isolates were significantly more likely than those lacking iss to be classified as complement-resistant and virulent. Such results, at least for this group of avian E. coli, suggest that there is a compelling but imperfect relationship among complement resistance, virulence, and the presence of iss. These results also suggest that the flow cytometric assay may be a reasonable alternative to the viable count method of determining complement resistance.

In vitro effect of ethylenediaminetetraacetic acid-Tris on the efficacy of hatchery disinfectants

Solutions of ethylenediaminetetraacetic acid (EDTA)-Tris showed synergistic or additive effects on gram-negative bacteria when combined with hatchery disinfectants consisting of phenol and detergent (Magnaphen-100), quaternary ammonium compound (QAC) and glutaraldehyde (Synergize), QAC (BioSentry 904), and hydrogen peroxide. The gram-positive bacteria reacted less favorably, with reaction mixtures showing all three levels of potentiation (synergistie, additive, and antagonistic). Combinations of EDTA-Tris and a commercial glutaraldehyde solution (Glutracide), when mixed with the test organisms, showed mostly antagonistic effects. Solutions of EDTA-Tris decreased the concentration of hatchery disinfectants required for bacterial killing by 75% in those situations in which synergistic potentiation occurred. EDTA-Tris is nontoxic to 12-day-old embryos. Serial passage of the test organisms in solutions of EDTA-Tris did not result in the development of resistant forms.

Chicken embryo lethality assay for determining the virulence of avian Escherichia coli isolates

Multiple isolates of Escherichia coli from clinical cases of colibacillosis and E. coli from the intestinal tracts of normal broilers at slaughter were assayed by the embryo lethality test to determine their virulence. The assay was repeated five times in order to establish reproducibility and determine the statistical parameters of the test. This study showed that the inoculation of approximately 100 colony-forming units in the allantoic cavity of 12-day-old embryos discriminated between virulent and avirulent E. coli isolates. Gross lesions included cranial and skin hemorrhages in addition to encephalomalacia in embryos inoculated with virulent isolates. Abnormalities were observed by microscopic examination of the heart, brain, and liver in embryos inoculated with virulent isolates. Analysis of data indicated that the length of the test should be 4 days. In the virulent group, day 2 postinoculation had the most significant death patterns. Sample size calculations indicated that 11 embryos are sufficient for the assay. On the basis of death rates, isolates considered to be avirulent had an embryo death rate of <10%, moderately or secondary pathogens had a 10%-29% death rate, and virulent isolates had a death rate of >29%. An important aspect of this assay is the accessibility of good-quality fertile embryonated eggs.

Normal hematologic and serum biochemical reference intervals for juvenile wild turkeys

Blood samples taken from 48 4-mo-old wild turkeys (Meleagris gallopova silvestris) were used to establish reference intervals for hematology and serum chemistry values. The study was conducted during September and October 1996. Packed cell volume, total and differential white cell counts, total protein, albumin, glucose, calcium, uric acid, triglyceride concentrations, as well as aspartate transaminase (AST) and lactate dehydrogenase (LDH) activities were assayed. Reference intervals from wild turkeys are similar to those reported for domestic turkeys.

Inhibition of Salmonella typhimurium in the chicken intestinal tract by a transformed avirulent avian Escherichia coli

An avirulent, wild-type avian Escherichia coli (E. coli Av) was electrotransformed with a plasmid coding for the production of microcin 24 (pGOB18) and was designated E. coli AvGOB18. The transformant inhibited the growth of seven serotypes of Salmonella commonly associated with colonization and contamination of poultry products and seven strains of E. coli O157:H7 in the in vitro colicin/microcin assay. The transformant did not inhibit the replication of multiple isolates of Listeria monocytogenes or Campylobacter jejuni in similar assays. The transformant is nonconjugative, indicating that the plasmid would not be transmitted to other intestinal microflora in the environment. The transformant also survived in sterile tap and deionized water incubated at 25 C and 37 C in the laboratory for 30 days and was recovered from drinkers and birds in in vivo floor pen studies. In in vivo studies, E. coli AvGOB18 did not colonize the intestinal tract of broiler chicks when given as a single or multiple dose and did not reduce the Salmonella load in the broilers. But Salmonella typhimurium was reduced significantly in the intestinal tracts of broiler chickens when E. coli AvGOB18 was administered continually in the water supply.

Mutation rate of avian intestinal coliform bacteria when pressured with fluoroquinolones

The purpose of this study was to determine the rate at which resistance developed in avian coliform bacteria when exposed to nalidixic acid, sarafloxacin, or enrofloxacin. In in vitro studies, the rates of mutation of avian isolates of Escherichia coli and Salmonella were determined following nalidixic acid, sarafloxacin, or enrofloxacin pressure. The rates of mutation were similar for nalidixic acid and sarafloxacin, whereas a lower rate of mutation was seen after enrofloxacin pressure. In in vivo studies, the quinolones were administered in the drinking water to broiler chickens at a concentration of 40 ppm for five consecutive days. Samples of feces were inoculated onto appropriate media and the frequency of resistance was determined. The frequency rates of resistance to nalidixic acid and sarafloxacin were similar. Enrofloxacin-medicated birds did not develop enrofloxacin-resistant coliform bacteria. The in vitro and in vivo data appear to correlate.

Colonization of the chicken trachea by an avirulent avian Escherichia coli transformed with plasmid pHK11

Recombinant plasmid pHK11 was transformed into an avirulent, wild-type avian Escherichia coli (E. coli Av) in order to study the plasmid's effect on colonization of the chicken trachea. The transformant (E. coli Av + pHK11) produced colicin V (ColV), had type F1 fimbriae, and was motile. The E. coli Av recipient possessed type F1 fimbriae but was nonmotile; it did not produce ColV. Four-day-old chicks were inoculated in the trachea with 100 microliters of an overnight culture (approximately 10(8) colony-forming units) of E. coli Av, E. coli Av + pHK11, or sterile brain-heart infusion (BHI) broth. A group of uninoculated chicks was also included. Samples of the trachea were taken on days 4 and 10 postinoculation and compared histologically and bacteriologically. Birds inoculated with E. coli Av + pHK11 had enhanced tracheal colonization and showed increased histologic changes as compared with those inoculated with E. coli Av or BHI broth or uninoculated controls. These results indicate that production of ColV and motility enhance the colonization of the trachea and may be involved in the cause of pathologic lesions.

Analysis of plasmids cloned from a virulent avian Escherichia coli and transformed into Escherichia coli DH5 alpha

Three of four plasmids from a virulent wild-type avian Escherichia coli were cloned or transformed into an avirulent laboratory recipient E. coli DH5 alpha and tested for the ability to confer a virulence phenotype. The three plasmids transformed into E. coli DH5 alpha were 5, 6, and 56 kb. A fourth plasmid of 64 kb was not successfully transformed. Parameters used to measure virulence included presence of type 1 pili and a smooth lipopolysaccharide (LPS) layer, motility, production of Colicin V, resistance to host complement, and embryo lethality. The 5-kb plasmid encoded for ampicillin resistance, whereas the 6-kb plasmid encoded for tetracycline resistance. The 56-kb plasmid encoded for streptomycin, sulfisoxazole, and tetracycline resistance. Twelve-day embryos inoculated with 467 colony-forming units of E. coli DH5 alpha containing the 56-kb plasmid had increased death rates (45%) in the embryo lethality assay and a decreased weight of surviving embryos with cranial hemorrhages as compared with embryos inoculated with similar amounts of E. coli DH5 alpha (0%) and phosphate-buffered saline (0%). Embryos inoculated with the wild-type virulent E. coli had 90% deaths. The 56-kb plasmid also had homology with a probe for Colicin V production (cvaC). No differences in LPS layer, complement resistance, motility, Colicin V activity, type 1 pili, cell-free supernatant proteins, or outer membrane proteins were observed in the transformants when compared with nontransformed E. coli DH5 alpha.

Antimicrobial effect of combinations of EDTA-Tris and amikacin or neomycin on the microorganisms associated with otitis externa in dogs

Combinations of EDTA-Tris and two aminoglycoside antibiotics (amikacin and neomycin) were tested for synergistic activities against the microorganisms associated with otitis externa in dogs and for the solutions' stability over time. Synergistic activity was observed when EDTA-Tris plus amikacin and EDTA-Tris plus neomycin were tested against Staphylococcus intermedius, Proteus mirabilis, Pseudomonas aeruginosa, and Escherichia coli, but not against Candida albicans. Stability studies over a 3-month period indicated that the test solutions were stable at room temperature and that their antimicrobial activity was maintained.

Analysis and characterization of Mycoplasma gallisepticum isolates from Pennsylvania

Because Mycoplasma gallisepticum F strain vaccine can be pathogenic in chickens and is pathogenic in turkeys, we monitored the spread of MG F strain into unvaccinated flocks by screening field and experimental isolates. Thirteen MG isolates obtained from various sources in Pennsylvania were screened using several techniques capable of differentiating between MG strains. DNA restriction enzyme analysis (REA), Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) protein profiles, non-isotopic DNA probes, and a monoclonal antibody specific for F strain were used to characterize each of the 13 isolates. Three of the 13 isolates were identical to F strain; two of these were obtained from challenge studies, and one was a field isolate from a multiple-age commercial egg farm where the F strain vaccine had been used in the past. The remaining 10 isolates were different from MG F strain but were quite similar if not identical to each other according to REA; SDS-PAGE protein profiles show similarities between the 10 isolates. The results suggested that F strain vaccine is not a major cause of field outbreaks of MG in Pennsylvania.

Effect of normal intestinal flora of chickens on colonization by virulent colicin V-producing, avirulent, and mutant colicin V-producing avian Escherichia coli

Colonization of the intestinal tracts of newly hatched chicks with Escherichia coli was attempted by swabbing test organisms onto the air-shell of 19-day-old embryos. Test organisms consisted of two virulent E. coli isolates, one avirulent isolate, and one laboratory-derived mutant of the avirulent isolate carrying a recombinant plasmid coding for Colicin V production. Chicks were cultured weekly for 3 weeks for total E. coli and for the test organisms using selective media. Control chicks were sampled on weeks 1 and 5, and the normal E. coli intestinal microflora were examined for the production of colicins. The two virulent E. coli isolates maintained colonization of the chicks for the 3-week test period, with titers decreasing from 10' to 10'- colony-forming units (CFU)/g of intestine. The avirulent isolate and laboratory mutant did not consistently colonize the intestinal tracts. The majority of intestinal samples taken from the control chicks at 1 and 5 weeks had colicin-producing E. coli that were inhibitory to the test organisms.

Phenotypic expression of recombinant plasmids pKT107 and pHK11 in an avirulent avian Escherichia coli

An avirulent wild-type avian Escherichia coli strain (Av) was electrotransformed with plasmids coding for complement resistance (pKT107) and Colicin V (ColV) production (pHK11) in order to study the effects of complement resistance and ColV production on virulence. Transformants were also compared with the wild type for embryo lethality, uptake by macrophages, motility, growth rate, plasmid content, and hemolysis. Growth rates and complement resistance patterns of strain Av and transformant Av+pHK11 were similar, but Av+pHK11 caused a significantly greater number of deaths in embryos and acquired motility. Transformant Av+pKT107 had a lower rate of phagocytosis, a slower growth rate, and a greater sensitivity to complement, and it changed from being non-hemolytic to expressing alpha-hemolytic action. The 35-kb plasmid present in the wild type was not present in the transformants. Although some of the results demonstrate the difficulties encountered in using wild-type organisms as recipients in virulence studies, the results with Av+pHK11 indicate that ColV production plus the acquisition of motility contributes to the virulence of avian E. coli.

Association of K-1 capsule, smooth lipopolysaccharides, traT gene, and Colicin V production with complement resistance and virulence of avian Escherichia coli

A group of complement-resistant, virulent avian Escherichia coli isolates were compared with a group of complement-sensitive, avirulent avian isolates for the presence of K-1 capsule, smooth lipopolysaccharides (LPS), the traT gene, and Colicin V (ColV) production. These parameters were selected because of their reported association with complement resistance and virulence in E. coli. Lethality in chicken embryos has also been shown to be correlated with virulence of avian E. coli for chickens. The complement-resistant, virulent E. coli isolates did not possess a K-1 capsule. Production of ColV and the presence of smooth LPS were significantly correlated with embryo lethality. There was no correlation between the presence of traT and embryo lethality. These results suggest that complement resistance and virulence in avian E. coli are associated with ColV production and smooth LPS but not with K-1 antigen or traT.

Activation of thymocyte deoxyribonucleic acid degradation by endogenous glucocorticoids

Immature lymphocytes in the thymus gland are killed by treatment with exogenous glucocorticoids. This steroid-mediated lymphocytolysis is preceded by numerous alterations in lymphocyte metabolism, including a DNA-degrading process in which the genome is cleaved at internucleosomal intervals. To date, this process has only been characterized by treating lymphocytes in vitro with glucocorticoids or by exogenous treatment of whole animals with adrenal steroids. To determine whether thymocyte DNA degradation could be activated by endogenous glucocorticoids, 4-wk-old chicks were treated with porcine adrenocorticotropic hormone (ACTH). This procedure elevated serum corticosterone levels approximately 80-fold within 2 h of hormone treatment. Following ACTH administration, thymocyte DNA was isolated and analyzed by agarose gel electrophoresis. The ACTH activated a DNA-degrading process that generated internucleosomal fragments of DNA identical in size to those observed following exogenous treatment with synthetic or naturally occurring glucocorticoids. Furthermore, this response could be inhibited by the glucocorticoid antagonist RU486 (17 beta-hydroxy-11 beta, 4-dimethylaminophenyl-17 alpha-propynl-estra-4,9,diene-3-one), indicating that adrenal steroids activate this process via the glucocorticoid receptor. These results demonstrate that lymphocyte DNA degradation does not result solely from exogenous glucocorticoid treatment; moreover, endogenous glucocorticoids can mediate this process and may thereby play an important role in thymic gland function.

Glucocorticoid-mediated activation of DNA degradation in avian lymphocytes

Little information is known about the molecular mechanism of programmed cell death in the avian species. In the current study we have analyzed this process in chickens using a glucocorticoid-lymphocyte model system. Three-week-old male broiler chicks were treated in vivo with the synthetic glucocorticoid, dexamethasone. Following this treatment genomic DNA was isolated from thymocytes and analyzed by agarose gel electrophoresis. Dexamethasone activated a DNA degrading process in which the genome was specifically cleaved at internucleosomal intervals. This steroid-induced response occurred prior to thymocyte cell death and was time and glucocorticoid dose dependent, as well as tissue and steroid specific. Only the glucocorticoid class of steroid hormones could elicit this response and DNA degradation was only detectable in lymphoid tissues that contained immature lymphocytes. Internucleosomal DNA degradation could also be elicited via administration of adrenocorticotrophic hormone, a treatment that elevates endogenous glucocorticoids. Based on these data, glucocorticoid-activated DNA degradation of the avian thymocyte genome appears to be a steroid receptor-mediated process which involves the activation of an endogenous nuclease that cleaves the genome at internucleosomal sites. Degradation of the thymocyte genome occurs prior to cell death and may represent an initial event in a cascade of hormone-mediated processes that culminate in a type of cellular suicide referred to as programmed cell death.

Glucocorticoid activation of deoxyribonucleic acid degradation in bursal lymphocytes

Treatment of animals with exogenous adrenal steroids or elevation of endogenous glucocorticoids results in a profound involution of lymphoid tissue. In rodent species, this lymphoinvolution is accompanied by lymphocyte cell death and extensive degradation of the genome prior to lymphocytolysis. In the present study, this process was investigated in the bursa of Fabricius of domestic fowl. Four-wk-old chicks were treated with a single injection of dexamethasone, and bursal regression and cell viability were monitored over a 72-h period. Following hormone treatment, DNA was extracted from bursal lymphocytes and analyzed by agarose gel electrophoresis. Dexamethasone treatment resulted in a rapid regression of bursal tissue that could be detected as soon as 6 h posttreatment, but lymphocyte viability was not altered until 24 h afterward. The DNA isolated from bursal lymphocytes of glucocorticoid-treated birds appeared to be degraded at internucleosomal sites and generated a "ladder" of discrete DNA fragments when analyzed by agarose gel electrophoresis. This form of hormone-induced cell death, referred to as programmed cell death, may play a key role in glucocorticoid-mediated immunosuppression.

Transient paralysis of the diaphragm following radical neck surgery

We have observed transient diaphragmatic paralysis with high alveolar to arterial oxygen partial pressure difference following radical neck surgery. Patients required supplemental oxygen for maintenance of arterial oxygenation. Patients following radical and neck surgery should be followed with chest roentgenograph to exclude pneumothorax and diaphragmatic paralysis and arterial blood gases in the immediate postoperative period.

Evidence for acute cellular changes in human hepatocytes during anesthesia with halogenated agents: an electron microscopic study

Liver biopsy specimens of 24 patients who had elective laparotomies were studied by electron microscopy for evidence of anesthesia-related toxic changes. All patients were initially anesthetized with nitrous oxide, barbiturate, and narcotic until the laparotomy incision was completed and an initial preanesthesia liver biopsy specimen was taken. Patients were then give, in randomized fashion, maintenance inhalational anesthesia for the duration of the procedure with halothane, fluroxene, or enflurane. Control patients were continued on nitrous oxide, barbiturate, and narcotic. After approximately 60 minutes a second postanesthesia liver biopsy specimen was taken. For each patient, the preanethesia and postanesthesia liver biopsy specimens were compared, in blinded fashion, for evidence of morphologic changes resulting from anesthesia. Ultrastructural changes consistent with hepatic toxicity were present in more than 25% of the cells examined in the postanesthesia specimens in all of the seven patients given halothane, five of the six patients given fluroxene, and one of the five patients given enflurane. None of the six nitrous oxide-barbiturate-narcotic control patients showed toxic changes in postanesthesia specimens. The most prominent toxic change was dilatation of endoplasmic reticulum. Accumulation of intracellular inclusions occurred in some cells, and a small percentage of cells also showed lipid accumulation and mitochondrial swelling. Evidence suggested that exposure to halogenated anesthetics is related to acute toxic subcellular changes in hepatocytes.

Sodium intake alters the effects of norepinephrine on the renin system and the kidney

To examine the interactions between sodium intake and the sympathetic nervous system and their influences on the blood pressure control system we studied eight normotensive men after high (800 mEq/d) and low (10 mEq/d) sodium intake. We measured blood pressure, arterial, venous and urinary norepinephrine (NE), glomerular filtration rate (GFR), renal blood flow (RBF), plasma renin activity (PRA) and aldosterone (PA), and the fractional excretion of sodium (FENa) and potassium (FEK) before and during incremental infusion of norepinephrine. High salt intake influenced the sensitivity to NE as well as subsequent pressor responses. The NE-induced decrease in RBF and GFR was not different on high and low sodium intakes. A significant decrease in FENa (p less than 0.05) with NE infusion could only be seen during high sodium intake. A significant increase in PRA (p less than 0.01) and PA (p less than 0.05) was induced by NE only during the low sodium period. These observations reveal previously unrecognized qualitative and quantitative interactions between sodium homeostasis and norepinephrine which are capable of influencing blood pressure in man.

Sodium intake alters the effects of norepinephrine on blood pressure

To examine the interactions between sodium balance and the sympathetic nervous system, we studied eight normotensive men after high (800 mEq/day) and low (10 mEq/day) sodium intake. We measured blood pressure (BP), arterial, venous, and urinary norepinephrine (NE) before and during incremental infusion of NE. We found significant direct, linear relationships (p less than 0.001) between the dose of NE infused and arterial and venous NE levels, and with mean arterial BP at both levels of sodium balance. In addition. the sensitivity was greater and the threshold of pressor response to NE as well as the basal concentrations of NE in arterial and venous plasma significantly lower (p less than 0.05) after the high sodium period. These observations expose heretofore unrecognized qualitative and quantitative interactions between sodium balance and NE that are capable of influencing BP in man.

Reduction of enflurane-induced spike activity by scopolamine

The possibility of enflurane-induced spike activity being related to a cholinergic mechanism was investigated. Thirty mongrel dogs were anesthetized with an inspired enflurane concentration of 3.5 +/- 0.09% (mean +/- SD) to obtain a sustained EEG spike activity. Scopolamine, in 0.04 mg/kg to 0.4 mg/kg IV doses, significantly decreased the spike activity (p less than 0.05). We speculate that a central cholinergic muscarinic mechanism is at least partly responsible for the EEG spike activity produced by enflurane.

Significance and application of blood gas determinations from the left atrial catheter

Left atrial catheters are used to measure left heart filling pressure in patients after open-heart surgery. It was observed that in some patients blood gases obtained from the left atrial catheters had a markedly higher PO2 as compared to PaO2 in the presence of severe hypoxemia. Twenty-five patients were studied consecutively; pulmonary venous admixture calculated from arterial blood was higher in 19 patients and lower in 5 as compared with that calculated from blood withdrawn from the left atrial catheter. These differences in venous admixture are due to regional changes in the lungs. This observation can be utilized in concentrating respiratory therapy to the regions of the lungs involved with significant therapeutic benefit to the patient.

Vascular compartmentalization of plasma norepinephrine in normal man: the relationships between venous and arterial norepinephrine concentration and the urinary excretion of norepinephrine

To examine whether the concentration of NE in human plasma is dependent on the vascular source of the sample and to examine the contribution of the kidney to urinary NE, 14 normal men were studied. Plasma samples were obtained from a superficial forearm vein, and radial artery and urine samples were obtained during 1 hr of recumbency and 1 hr of upright posture. The Vne was greater than Ane during both recumbency and upright posture in black males. Such differences were not seen in age-matched white subjects. Stimulation of the sympathetic nervous system by upright posture increased both Vne and Ane in all subjects. NE concentrations in simultaneously obtained arterial and venous samples were different during the time of cardiovascular adjustments to upright posture. The urinary Xne increased after standing. Endogenous CCr decreased, whereas apparent NE clearance, calculated from the Ane, increased after standing, suggesting that a major portion of the augmented urinary Xne induced by upright posture was from an intrarenal source. We conclude that the concentration of NE in human blood is related to the specific vascular bed from which the sample is obtained, and that urinary NE is not solely derived from plasma by glomerular filtration but also arises from an unidentified renal source.

Acquired right-to-left intracardiac shunts and severe hypoxemia

Critically ill hypoxemic patients without significant radiological changes on the chest x-ray present a diagnostic and therapeutic problem. Three patients with patent foramen ovale and a patient with a spontaneously closed congenital ventricular septal defect which reopened due to ischemic changes in the ventricular septum are presented. In reviewing the literature, we could not find this type of presentation. Their hypoxemia was associated with right-to-left intracardiac shunts demonstrated by dye dilution cardiac output curves. Because of the risk of systemic embolism associated with a right-to-left intracardiac shunt, air bubbles and particulate material in the intravenous infusion should be avoided. Use of anticoagulants may be beneficial. High inspired oxygen concentration may not correct the associated hypoxemia. The detection of these shunts is easily done at the bedside.

The anesthetic and perioperative management of a patient with documented hereditary angioneurotic edema

A patient with documented hereditary angioneurotic edema was admitted for elective surgical extraction of 3 impacted 3rd molars under local anesthesia. In order to increase his C'1-INH level, he was prepared for operation with 2 units of fresh-frozen plasma 24 hours preoperatively. Postoperatively, he was observed in the ICU for 24 hours and on the ward for 2 days, and was discharged without any complications from the surgical trauma.

Hypocalcaemia during rapid blood transfusion in anaesthetized man

In anaesthetized patients, administration of citrated whole blood for 5 min at controlled rates of 50, 100 and 150 ml/70 kg/min resulted in decreases in the calcium ion concentration (Ca2+) of 14, 31 and 41%, respectively. Ca2+ returned rapidly to the control values after termination of the transfusion. Reciprocal changes in serum citrate concentrations occurred, suggesting that the transient hypocalcaemia was a result of redistribution of citrate and hepatic or renal clearance from the vascular space. The total serum calcium concentration did not change significantly during rapid blood administration. Normal saline infusion at 100 ml/70 kg/min caused no change in Ca2+; however, plasma protein administration at this rate resulted in an 18% decrease in Ca2+, presumably as a consequence of the binding of calcium ions to anionic sites on plasma protein. Hypocalcaemia accompanying blood transfusion is a transient phenomenon, dependent on the total dose of citrate administered and the rate of infusion. Rational calcium replacement therapy during massive blood transfusion may now be based on direct Ca+ measurement.