Characterisation of acid-base abnormalities in pigs experimentally infected with Chlamydia suis

Blood gases, acid-base, and metabolic alterations in calves with bronchopneumonia diagnosed via clinical signs and thoracic ultrasonography: A cross-sectional study

BACKGROUND

Bronchopneumonia (BP) in calves potentially causes systemic changes.

OBJECTIVES

To describe metabolic, arterial blood gas, and acid-base disorders in calves with BP diagnosed by thoracic ultrasound (TUS), Wisconsin score (WISC), and combinations of WISC and TUS.

ANIMALS

Two hundred thirty-one dairy preweaned dairy calves from 13 dairy farms.

METHODS

Cross-sectional study. Each calf sequentially underwent arterial blood gas evaluation, WISC score, venous sampling, and TUS. Calves were grouped based on a single diagnostic method and combination of WISC and 2 TUS cutoffs (≥1 cm; ≥3 cm) as healthy, upper respiratory tract infection, subclinical BP, and clinical BP.

RESULTS

Oxygenation and acid-base variables were unaffected. Glucose concentration in TUS-affected calves was significantly lower (P < .001) than in healthy calves (median ≥TUS1cm = 5.2 mmol/L 25%-75% interquartile range [IQR] 4.5-6.1,

CONCLUSIONS AND CLINICAL IMPORTANCE

Clinical signs indicate minor systemic disorders compared to TUS. The abnormalities detected by ultrasonographic examination were moderate and did not deviate from normal reference ranges.

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Key Words

• blood gas analysis
• calves
• clinical signs
• respiratory disease
• thoracic ultrasonography

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MESH Headings

• Animals
• Cattle
• Cross-Sectional Studies
• Cattle Diseases/diagnostic imaging
• Cattle Diseases/blood
• Bronchopneumonia/veterinary
• Bronchopneumonia/diagnostic imaging
• Bronchopneumonia/blood
• Blood Gas Analysis/veterinary
• Ultrasonography/veterinary
• Female
• Male
• Blood Glucose/analysis

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Grants

• University of Milan
• University of Milan

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Affiliation(s)

Antonio Boccardo Dipartimento di Medicina Veterinaria e Scienze Animali (DIVAS)Università degli Studi di MilanoLodiItaly
Vincenzo Ferrulli Dipartimento di Medicina Veterinaria e Scienze Animali (DIVAS)Università degli Studi di MilanoLodiItaly
Giulia Sala Dipartimento di Scienze VeterinarieUniversità degli Studi di PisaSan Piero a GradoItaly
Donatella Scavone Dipartimento di Medicina Veterinaria e Scienze Animali (DIVAS)Università degli Studi di MilanoLodiItaly
Saverio Paltrinieri Dipartimento di Medicina Veterinaria e Scienze Animali (DIVAS)Università degli Studi di MilanoLodiItaly
Laura Filippone Pavesi Dipartimento di Medicina Veterinaria e Scienze Animali (DIVAS)Università degli Studi di MilanoLodiItaly
Davide Pravettoni Dipartimento di Medicina Veterinaria e Scienze Animali (DIVAS)Università degli Studi di MilanoLodiItaly

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Seroprevalence and Risk Factors of Chlamydia Infection in Cattle in Shanxi Province, North China

The information on Chlamydia infection in cattle is limited in Shanxi Province, north China. This study aimed to investigate the seroprevalence and risk factors of Chlamydia and Chlamydia abortus infection in cattle in Shanxi Province. In November 2020, a large-scale investigation of Chlamydia seroprevalence was conducted on 981 cattle serum samples collected from 40 cattle farms in 11 cities of Shanxi Province. The seroprevalence of Chlamydia and C. abortus was examined by indirect hemagglutination assay (IHA) and enzyme-linked immunosorbent assay (ELISA), respectively. The seroprevalence of Chlamydia and C. abortus was 52.29% (513/981) and 2.96% (29/981), respectively, in cattle in Shanxi Province. Location was identified as a risk factor for Chlamydia and C. abortus infection (p < 0.05). Under different management patterns, the seroprevalence of Chlamydia and C. abortus in large-scale animal farming companies was higher than that in household animal farms and animal farming cooperatives, and only the seroprevalence of Chlamydia was significantly different in different management patterns (p < 0.01). The results showed that there was higher seroprevalence of Chlamydia in cattle in Shanxi Province, while C. abortus was not the dominant species. This study provided baseline information on Chlamydia infection in cattle in Shanxi Province, which constitutes valuable data for monitoring livestock health and preventing potential zoonoses.

A Meta-Analysis of Bovine Chlamydia Prevalence in Cattle in China from 1989 to 2020

Chlamydia bovis is a widespread infection disease caused by the mixed infection of Chlamydia psittaci, Chlamydia pecorum, Chlamydia abortus, and Chlamydia suis in cattle. Although many studies have investigated Chlamydia infection in cattle, there is no nationwide study on the prevalence of Chlamydia infection in cattle of China. We constructed the first meta-analysis to assess the infection rate and infection risk factors of Chlamydia in cattle in China, and we searched PubMed, ScienceDirect, Chinese Web of Knowledge, Wanfang, and VIP Chinese journal database for studies reporting Chlamydia infection in cattle from April 29, 2020. We collected a total of 563 publications from 1989 to 2019, and finally, 78 studies were eligible, which included 152,364 cattle from 27 provinces across the country. We estimated the pooled prevalence of Chlamydia in cattle was 14.2% (95% confidence interval [CI]: 12.2 to 16.4). The prevalence of bovine Chlamydia in China collected before 2000 (14.8%, 95% CI: 5.6 to 27.3) showed the highest prevalence rate. The highest prevalence was found in Central China (22.6%, 95% CI: 12.8 to 34.2). The prevalence of Chlamydia spp. between abortion cattle (39.1%, 95% CI: 24.6 to 54.6) and healthy cattle (8.3%, 95% CI: 3.1 to 15.2) showed significant variation (p < 0.05). In detection methods subgroup, enzyme-linked immunosorbent assay (30.5%, 95% CI: 21.5 to 40.3) showed the highest prevalence. In the age subgroup, the prevalence rate of age >1 year (16.6%, 95% CI: 12.6 to 20.9) was higher compared with age ≤1 year (9.8%, 95% CI: 6.7 to 13.3). Yaks (17.8%, 95% CI: 13.3 to 22.8) showed the highest Chlamydia prevalence among the varieties of bovine. We also estimated the potential risk factors such as feeding model, sample classification, sampling seasons, bovine gender, parity, and quality level of included studies. Our findings suggested that Chlamydia was prevalent in cattle in China. So we should pay attention to bovine Chlamydia and take necessary measures to prevent it.

Acid-base variables in acute and chronic form of nontuberculous mycobacterial infection in growing goats experimentally inoculated with Mycobacterium avium subsp. hominissuis or Mycobacterium avium subsp. paratuberculosis

In current literature, data assessing the acid-base equilibrium in animals and humans during bacterial infection are rare. This study aimed to evaluate acid-base deteriorations in growing goats with experimentally induced NTM (nontuberculous mycobacteria) infections by application of the traditional Henderson-Hasselbalch approach and the strong ion model. NTM-challenged animals were orally inoculated with either Mycobacterium avium subsp. hominissuis (MAH; n = 18) or Mycobacterium avium subsp. paratuberculosis (MAP; n = 48). Twenty-five goats served as non-infected controls. Until 51^st week post-inoculation (wpi), blood gas analysis, serum biochemical analysis, and serum electrophoresis were performed on venous blood. Fifty percent (9/18) of goats inoculated with MAH developed acute clinical signs like apathy, fever, and diarrhea. Those animals died or had to be euthanized within 11 weeks post-inoculation. This acute form of NTM-infection was characterized by significantly lower concentrations of sodium, calcium, albumin, and total protein, as well as significantly higher concentrations of gamma globulin, associated with reduced albumin/globulin ratio. Acid-base status indicated alkalosis, but normal base excess and HCO₃^- concentrations, besides significantly reduced levels of SID (strong ion difference), A_{tot Alb} (total plasma concentration of weak non-volatile acids, based on albumin), A_{tot TP} (A_tot based on total protein) and markedly lower SIG (strong ion gap). The remaining fifty percent (9/18) of MAH-infected goats and all goats challenged with MAP survived and presented a more sub-clinical, chronic form of infection mainly characterized by changes in serum protein profiles. With the progression of the disease, concentrations of gamma globulin, and total protein increased while albumin remained lower compared to controls. Consequently, significantly reduced albumin/globulin ratio and lower A_{tot Alb} as well as higher A_{tot TP} were observed. Changes were fully compensated with no effect on blood pH. Only the strong ion variables differentiated alterations in acid-base equilibrium during acute and chronic NTM-infection.

Asymptomatic infections with highly polymorphic Chlamydia suis are ubiquitous in pigs

Background

Chlamydia suis is an important, globally distributed, highly prevalent and diverse obligate intracellular pathogen infecting pigs. To investigate the prevalence and genetic diversity of C. suis in China, 2,137 nasal, conjunctival, and rectal swabs as well as whole blood and lung samples of pigs were collected in 19 regions from ten provinces of China in this study.

Results

We report an overall positivity of 62.4% (1,334/2,137) of C. suis following screening by Chlamydia spp. 23S rRNA-based FRET-PCR and high-resolution melting curve analysis and confirmatory sequencing. For C. suis-positive samples, 33.3 % of whole blood and 62.5% of rectal swabs were found to be positive for the C. suis tetR(C) gene, while 13.3% of whole blood and 87.0% of rectal swabs were positive for the C. suis tet(C) gene. Phylogenetic comparison of partial C. suis ompA gene sequences revealed significant genetic diversity in the C. suis strains. This genetic diversity was confirmed by C. suis-specific multilocus sequence typing (MLST), which identified 26 novel sequence types among 27 examined strains. Tanglegrams based on MLST and ompA sequences provided evidence of C. suis recombination amongst the strains analyzed.

Conclusions

Genetically highly diverse C. suis strains are exceedingly prevalent in pigs. As it stands, the potential pathogenic effect of C. suis on pig health and production of C. suis remains unclear and will be the subject of further investigations. Further study is also required to address the transmission of C. suis between pigs and the risk of 'spill-over' and 'spill-back' of infections to wild animals and humans.

Electronic supplementary material

The online version of this article (10.1186/s12917-017-1295-x) contains supplementary material, which is available to authorized users.

Effect of Intravenously Administered Crystalloid Solutions on Acid-Base Balance in Domestic Animals

Intravenous fluid therapy can alter plasma acid-base balance. The Stewart approach to acid-base balance is uniquely suited to identify and quantify the effects of the cationic and anionic constituents of crystalloid solutions on plasma pH. The plasma strong ion difference (SID) and weak acid concentrations are similar to those of the administered fluid, more so at higher administration rates and with larger volumes. A crystalloid's in vivo effects on plasma pH are described by 3 general rules: SID > [HCO3-] increases plasma pH (alkalosis); SID < [HCO3-] decreases plasma pH (alkalosis); and SID = [HCO3-] yields no change in plasma pH. The in vitro pH of commercially prepared crystalloid solutions has little to no effect on plasma pH because of their low titratable acidity. Appreciation of IV fluid composition and an understanding of basic physicochemical principles provide therapeutically valuable insights about how and why fluid therapy can produce and correct alterations of plasma acid-base equilibrium. The ideal balanced crystalloid should (1) contain species-specific concentrations of key electrolytes (Na+ , Cl- , K+ , Ca++ , Mg++ ), particularly Na+ and Cl- ; (2) maintain or normalize acid-base balance (provide an appropriate SID); and (3) be isosmotic and isotonic (not induce inappropriate fluid shifts) with normal plasma.

Chlamydia pecorum is the endemic intestinal species in cattle while C. gallinacea, C. psittaci and C. pneumoniae associate with sporadic systemic infection

To investigate the prevalence and diversity of bovine Chlamydia spp. in cattle, whole blood from dairy and beef cattle in 11 provinces of China (n=2003) and vaginal swabs, whole blood samples, feces, milk samples from cows in a Yangzhou dairy farm (n=108) were examined using genus- and species-specific PCRs. In cattle from 11 provinces, 2.4% (48/2003) of whole-blood samples were positive for Chlamydia spp., and four Chlamydia species (C. pneumoniae, 41.7%, 20/48; C. psittaci, 22.9%, 11/48; C. gallinacea, 20.8%, 10/48; C. pecorum, 6.3%, 3/48) were identified. In a further study on a Yangzhou dairy farm, 64.8% (70/108) of the cows were positive for Chlamydia spp. C. pecorum was the intestinal endemic species (51/51, 100%), and C. gallinacea was the most frequent species in vaginal swabs (24/27, 88.9%), whole blood buffy coats (5/8, 62.5%) and milk (4/6, 66.7%). C. psittaci and C. pneumoniae were infrequently detected. DNA sequencing of the ompA gene demonstrated the presence of multiple in-herd C. pecorum serovars and single C. gallinacea and C. psittaci serovars which were identical with those of poultry from Yangzhou. This is the first report of C. gallinacea and C. pneumoniae in cattle. Further study is required to address the transmission of Chlamydia spp., in particular of C. gallinacea and C. pneumoniae from their natural hosts, and their potential pathogenic effect on health and production of cattle.

Chlamydia gallinacea, not C. psittaci, is the endemic chlamydial species in chicken (Gallus gallus)

To investigate the prevalence and diversity of Chlamydia spp. in domestic birds in China, oral and cloacal swabs of healthy chickens, ducks, geese and pigeons were collected nationwide from live-animal markets and examined by Chlamydia spp. 23 S rRNA gene FRET-PCR followed by high-resolution melting curve analysis and confirmatory sequencing. Overall, 26.2% of the birds (602/2,300) were positive for Chlamydia spp. and five Chlamydia spp. were identified. While occasional detection of C. suis and C. muridarum in poultry is reported here for the first time, the predominant chlamydial agent was C. gallinacea representing 63.8% of all positives (384/602) and 81.2% of positive chickens (359/442). Analysis of the C. gallinacea ompA phylogeny revealed at least 13 well segregated variants (serovars). Seven-month monitoring of C. gallinacea-infected chickens indicated that the infection was persistent. C. gallinacea-infected chickens remained without overt clinical disease, but showed body weight gains significantly reduced by 6.5-11.4% beginning in week 3 post-infection. This study indicates that C. gallinacea is the endemic chlamydial species in chickens, whereas C. psittaci dominates only in pigeons. Further studies are required to address the specific conditions under which C. gallinacea could act as an avian pathogen and possibly also a zoonotic agent.

Evaluation of the presence and zoonotic transmission of Chlamydia suis in a pig slaughterhouse

Background

A significant number of studies on pig farms and wild boars worldwide, demonstrate the endemic presence of Chlamydia suis in pigs. However, the zoonotic potential of this pathogen, phylogenetically closely related to Chlamydia trachomatis, is still uninvestigated. Therefore, this study aims to examine the zoonotic transmission in a Belgian pig abattoir.

Methods

Presence of Chlamydia suis in pigs, contact surfaces, air and employees was assessed using a Chlamydia suis specific real-time PCR and culture. Furthermore, Chlamydia suis isolates were tested for the presence of the tet(C) gene.

Results

Chlamydia suis bacteria could be demonstrated in samples from pigs, the air and contact surfaces. Moreover, eye swabs of two employees were positive for Chlamydia suis by both PCR and culture. The tet(C) gene was absent in both human Chlamydia suis isolates and no clinical signs were reported.

Conclusions

These findings suggest the need for further epidemiological and clinical research to elucidate the significance of human ocular Chlamydia suis infections.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0560-x) contains supplementary material, which is available to authorized users.

Clinical utility of serum biochemical variables for predicting acid-base balance in critically ill horses

BACKGROUND

Profiles from serum biochemical analyzers include the concentration of strong electrolytes (including l-lactate), total carbon dioxide (tCO2 ), and total protein. These variables are associated with changes in acid-base balance. Application of physicochemical principles may allow predicting acid-base balance from serum biochemistry without measuring whole blood pH and pCO2 .

OBJECTIVES

The purpose of the study was to determine if the acid-base status of critically ill horses could be accurately predicted using variables included in standard serum biochemical profiles.

METHODS

Two jugular venous blood samples were prospectively obtained from critically ill horses and foals. Samples were analyzed using a whole blood gas and pH analyzer (BG) and a serum biochemistry multi analyzer system (AMAS). Linear regression, Deming regression, and Bland-Altman plots were used for method comparison and P < .05 was considered significant.

RESULTS

Values from 70 horses and foals for Na, K, Cl, and total protein concentrations, and consequently the calculated variables used for acid base interpretation, were different between the AMAS and BG analyzer. Using physicochemical principles, BG results accurately predicted pH, whereas the AMAS results did not when a fixed value for pCO2 was used.

CONCLUSIONS

Measurement of pCO2 is required in critically ill horses for accurate prediction of whole blood pH. Differences in the measured values of Na and Cl concentration exist when measured in serum by the AMAS and in whole blood or plasma by BG, indicating that the accurate prediction of whole blood pH is analyzer-dependent. Application of physicochemical principles to plasma or serum provides a practical method to evaluate analyzer accuracy.

A comparison of traditional and quantitative analysis of acid-base imbalances in hypoalbuminemic dogs

OBJECTIVE

To compare the traditional (HH) and quantitative approaches used for the evaluation of the acid-base balance in hypoalbuminemic dogs.

DESIGN

Prospective observational study.

SETTING

ICU of a veterinary teaching hospital.

ANIMALS

One hundred and five client-owned dogs.

MEASUREMENTS AND MAIN RESULTS

Jugular venous blood samples were collected from each patient on admission to determine: total plasma protein (TP), albumin (Alb), blood urea nitrogen (BUN), glucose (Glu), hematocrit (HCT), Na(+) , Cl(-) , K(+) , phosphate (Pi ), pH, PvCO2, bicarbonate (HCO3 (-) ), anion gap (AG), adjusted anion gap for albumin (AGalb ) or phosphate (AGalb-phos ), standardized base excess (SBE), strong ion difference (SID), concentration of nonvolatile weak buffers (Atot ), and strong ion gap (SIG). Patients were divided in 2 groups according to the severity of the hypoalbuminemia: mild (Alb = 21-25 g/L) and severe (Alb ≤20 g/L). All parameters were compared among groups. Patients with severe hypoalbuminemia showed significant decrease in TP (P = 0.011), Atot (P = 0.050), and a significant increase in adjusted AG (P = 0.048) and the magnitude of SIG (P = 0.011) compared to animals with mild hypoalbuminemia. According to the HH approach, the most frequent imbalances were simple disorders (51.4%), primarily metabolic acidosis (84.7%) associated with a high AG acidosis. However, when using the quantitative method, 58.1% of patients had complex disorders, with SIG acidosis (74.3%) and Atot alkalosis (33.3%) as the most frequent acid-base imbalances. Agreement between methods only matched in 32 cases (kappa < 0.20).

CONCLUSIONS

The agreement between the HH and quantitative methods for interpretation of acid-base balance was poor and many imbalances detected using the quantitative approach were missed using the HH approach. Further studies are necessary to confirm the clinical utility of using the quantitative approach in the decision-making process of the severely ill hypoalbuminemic patients.

Evaluation of pulmonary dysfunctions and acid-base imbalances induced by Chlamydia psittaci in a bovine model of respiratory infection

Background

Chlamydia psittaci (Cp) is a respiratory pathogen capable of inducing acute pulmonary zoonotic disease (psittacosis) or persistent infection. To elucidate the pathogenesis of this infection, a translational large animal model was recently introduced by our group. This study aims at quantifying and differentiating pulmonary dysfunction and acid–base imbalances induced by Cp.

Methods

Forty-two calves were grouped in (i) animals inoculated with Cp (n = 21) and (ii) controls sham-inoculated with uninfected cell culture (n = 21). For pulmonary function testing, impulse oscillometry, capnography, and FRC (functional residual capacity) measurement were applied to spontaneously breathing animals. Variables of acid–base status were assessed in venous blood using both (i) traditional Henderson-Hasselbalch and (ii) strong ion approach.

Results

Both obstructive and restrictive pulmonary disorders were induced in calves experimentally inoculated with Cp. Although disorders in respiratory mechanics lasted for 8–11 days, the pattern of spontaneous breathing was mainly altered in the period of acute illness (until 4 days post inoculation, dpi). Expiration was more impaired than inspiration, resulting in elevated FRC. Ventilation was characterised by a reduction in tidal volume (−25%) combined with an increased percentage of dead space volume and a significant reduction of alveolar volume by 10%. Minute ventilation increased significantly (+50%) due to a compensatory doubling of respiratory rate. Hyperventilatory hypocapnia at 2–3 dpi resulted in slightly increased blood pH at 2 dpi. However, the acid–base equilibrium was additionally influenced by metabolic components, i.e. the systemic inflammatory response, all of which were detected with help of the strong ion theory. Decreased concentrations of albumin (2–10 dpi), a negative acute-phase marker, resulted in a decrease in the sum of non-volatile weak acids (A_tot), revealing an alkalotic effect. This was counterbalanced by acidic effects of decreased strong ion difference (SID), mediated by the interplay between hypochloraemia (alkalotic effect) and hyponatraemia (acidic effect).

Conclusions

This bovine model was found to be suitable for studying pathophysiology of respiratory Cp infection and may help elucidating functional host-pathogen interactions in the mammalian lung.

Dose-dependent effects of Chlamydia psittaci infection on pulmonary gas exchange, innate immunity and acute-phase reaction in a bovine respiratory model

The respiratory pathogen Chlamydia psittaci naturally occurs in bovine herds and was recently shown to impair calf health in a dose-dependent manner. The aim of this study was to determine whether the functional consequences and immunological reactions of infection were dose related by quantifying the consequences of acute respiratory chlamydial infection on respiratory signs, disturbances of pulmonary gas exchange, response of the innate immune system, and acute-phase reaction. Fourteen calves were challenged intrabronchially with different C. psittaci doses (from 10(6) to 10(9)inclusion-forming units (ifu) per animal). Ten controls received either UV-inactivated chlamydiae or cell culture medium. Compared to the controls, all animals challenged with live C. psittaci developed hypoxaemia linked to reduced haemoglobin oxygen saturation, increased alveolar-arterial oxygen partial pressure difference (A-aO2) and pulmonary shunt, with symptoms following a dose-dependent pattern. Increases in lipopolysaccharide-binding protein (LBP) and leukocytes were also dose-dependent and accompanied by a regenerative left shift in neutrophil granulocytes. With the exception of LBP, which reflected the load of chlamydial cell components in the host, pathophysiological reactions were only detected in calves challenged with viable chlamydiae. These results indicate that the pathophysiological consequences of respiratory C. psittaci infections are strongly dependent on the challenge dose of chlamydiae. For further studies, challenge doses between 10(6) and 10(8)ifu/calf are recommended.

Pharmacokinetics of tildipirosin in porcine plasma, lung tissue, and bronchial fluid and effects of test conditions on in vitro activity against reference strains and field isolates of Actinobacillus pleuropneumoniae

The pharmacokinetics of tildipirosin (Zuprevo(®) 40 mg/mL solution for injection for pigs), a novel 16-membered-ring macrolide for the treatment for swine respiratory disease (SRD), was investigated in studies collecting blood plasma and postmortem samples of lung tissue and bronchial fluid (BF) from swine. In view of factors influencing the in vitro activity of macrolides, and for the interpretation of tildipirosin pharmacokinetics in relation to minimum inhibitory concentrations (MIC), additional experiments were conducted to study the effects of pH, carbon dioxide-enriched atmosphere, buffers, and serum on tildipirosin MICs for various reference strains and Actinobacillus (A.) pleuropneumoniae field isolates. After single intramuscular (i.m.) injection at 4 mg/kg body weight, maximum plasma concentration (Cmax) was 0.9 μg/mL observed within 23 min (Tmax ). Mean residence time from the time of dosing to the time of last measurable concentration (MRTlast) and terminal half-life (T1/2) both were about 4 days. A dose-response relationship with no significant sex effect is observed for area under the plasma concentration-time curve from time 0 to the last sampling time with a quantifiable drug concentration (AUClast) over the range of doses up to 6 mg/kg. However, linear dose proportionality could not be proven with statistical methods. The time-concentration profile of tildipirosin in BF and lung far exceeded that in blood plasma. In lung, tildipirosin concentrations reached 3.1 μg/g at 2 h, peaked at 4.3 μg/g at day 1, and slowly declined to 0.8 μg/g at day 17. In BF, tildipirosin levels were 14.3, 7.0, and 6.5 μg/g at days 5, 10, and 14. T1/2 in lung was ∼7 days. Tildipirosin is rapidly and extensively distributed to the respiratory tract followed by slow elimination. Culture media pH and carbon dioxide-enriched atmosphere (CO2 -EA) had a marked impact on in vitro activity of tildipirosin in reference strains of various rapidly growing aerobic and fastidious bacteria including Histophilus (H.) somni ATCC 700025 and A. pleuropneumoniae ATCC 27090. For A. pleuropneumoniae ATCC 27090 testing conditions without CO2 -EA resulted in reduced acidification of culture media pH and a reduction in the minimum inhibitory concentrations compared to standard in vitro test conditions by 2 log2 dilution steps (4-fold) from 8 to 2 μg/mL. Supplementary buffering of standard culture media resulted in a reduction in the A. pleuropneumoniae (n = 8) MIC range by 4 log2 dilution steps (16-fold) from 8-16 to 0.5-1 μg/mL. Incremental supplementation of culture media with 50% serum resulted in noticeable shifts to lower minimum or maximum MICs by at least 2 log2 dilution steps (≥4-fold) in all aerobic and fastidious reference strains tested except for Pasteurella (P.) multocida. The MIC of A. pleuropneumoniae ATCC 27090 decreased by 2-4 log2 dilution steps (4 to 16-fold) from 8 to 0.5-2 μg/mL when 50% serum was added to the standard assay. Considering a higher presence of serum and the rather neutral pH conditions maintained in vivo, it is suggested to take the influence of these factors on in vitro activity into account when interpreting tildipirosin MICs for A. pleuropneumoniae in relation to pharmacokinetics.

Importance of the effective strong ion difference of an intravenous solution in the treatment of diarrheic calves with naturally acquired acidemia and strong ion (metabolic) acidosis

BACKGROUND

The effect of sodium bicarbonate on acid-base balance in metabolic acidosis is interpreted differently by Henderson-Hasselbalch and strong ion acid-base approaches. Application of the traditional bicarbonate-centric approach indicates that bicarbonate administration corrects the metabolic acidosis by buffering hydrogen ions, whereas strong ion difference theory indicates that the co-administration of the strong cation sodium with a volatile buffer (bicarbonate) corrects the strong ion acidosis by increasing the strong ion difference (SID) in plasma.

OBJECTIVE

To investigate the relative importance of the effective SID of IV solutions in correcting acidemia in calves with diarrhea.

ANIMALS

Twenty-two Holstein-Friesian calves (4-21 days old) with naturally acquired diarrhea and strong ion (metabolic) acidosis.

METHODS

Calves were randomly assigned to IV treatment with a solution of sodium bicarbonate (1.4%) or sodium gluconate (3.26%). Fluids were administered over 4 hours and the effect on acid-base balance was determined.

RESULTS

Calves suffered from acidemia owing to moderate to strong ion acidosis arising from hyponatremia and hyper-D-lactatemia. Sodium bicarbonate infusion was effective in correcting the strong ion acidosis. In contrast, sodium gluconate infusion did not change blood pH, presumably because the strong anion gluconate was minimally metabolized.

CONCLUSIONS

A solution containing a high effective SID (sodium bicarbonate) is much more effective in alkalinizing diarrheic calves with strong ion acidosis than a solution with a low effective SID (sodium gluconate). Sodium gluconate is ineffective in correcting acidemia, which can be explained using traditional acid-base theory but requires a new parameter, effective SID, to be understood using the strong ion approach.

Relationship between the response to the corneal reflex (depth of narcosis) and specific parameters in the slaughter blood of pigs narcotised with CO2

There has been insufficient research into CO2 stunning with regard to its effect on pigs being slaughtered. This lack of knowledge may be at least partly responsible for the partial rejection of CO2-stunning methods. During routine slaughter work, 598 pigs (average carcase weight: 94 kg) were evaluated. The stunning procedure was carried out in industrial stunning chambers with 90% CO2 by volume and an exposure time of either 120 or 90 s. The corneal reflex response was evaluated immediately prior to bleeding in order to determine the depth of narcosis. Blood was taken at slaughter (slaughter blood) to determine the partial pressure of breathing gases and the acid-base status. We found that CO2 stunning mainly produced hypoxaemia, but also normoand hyperoxaemia, in arteriovenous slaughter blood. No further positive reflex responses occurred at a pO2 threshold of ≤ 1.6 kPa. PCO2 increased to values of 40 kPa and above. This extreme hypercapnia resulted in a decrease of the slaughter blood pH with values of less than 7.00 (ie, strong respiratory acidosis). Starting with threshold values from pCO2 > 23 kPa and pH < 6.85, stunned pigs revealed only a few or no positive reflex responses, respectively. The non-respiratory Stewart-variable serum [SID3] was elevated to alkaline values of 65 mmol L−1 and above, in comparison to the normal values of 45 (± 2) mmol L−1. We conclude that the use of cut-off points such as the pH and/or pO2 in routine sampling of slaughter animals (eg by application of ion-sensitive electrodes) would establish the depth of narcosis in pigs destined for slaughter. The efficiency of monitoring could thereby be improved during slaughter, in line with the demands of animal welfare.