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Detection of animal pathogens by using the polymerase chain reaction (PCR).

The polymerase chain reaction (PCR) is a nucleic acid-based technique that enables the rapid and sensitive detection of specific micro-organisms. Although this technique is widely used in veterinary research, it has not yet found applications in routine microbiological analysis of veterinary clinical samples. However, advances in sample preparation together with the increasing availability of specific gene sequences will probably lead to the more widespread diagnostic use of PCR in the future. PCR is likely to have a strong impact in the epidemiology, treatment and prevention of animal infectious diseases.

Animal Diseases↗

Tiamulin activity against fastidious and nonfastidious veterinary and human bacterial isolates: initial development of in vitro susceptibility test methods.

Tiamulin is a pleuromutilin derivative used in veterinary practice for the control and specific therapy of infections in swine. This report summarizes studies to establish standardized susceptibility testing methods, interpretive criteria, and reagent details for use in veterinary methods recently developed by the National Committee for Clinical Laboratory Standards (NCCLS) (standards M31-A and M37-A, NCCLS, Wayne, Pa., 1999). A total of 636 fastidious and nonfastidious animal and human pathogens were processed by using media and procedures described by the NCCLS. Tiamulin disk diffusion tests used a 30-microg disk concentration, and the proposed MIC breakpoints corresponding to levels achievable in animal target tissues (lung) were < or =4 microg/ml for susceptibility and > or =32 microg/ml for resistance. Correlate zone diameters for specific nonfastidious species were as follows: for Pasteurella multocida and staphylococci tested on Mueller-Hinton agar, susceptibility at > or =19 mm and resistance at < or =11 mm, and for Actinobacillus suis, Erysipelothrix rhusiopathiae, and Streptococcus suis tested on enriched chocolate Mueller-Hinton agar, susceptibility at > or =16 mm and resistance at < or =8 mm. When Actinobacillus pleuropneumoniae was tested, a susceptibility breakpoint of < or =16 microg/ml (> or =9 mm) was suggested for veterinary fastidious medium broth and enriched chocolate Mueller-Hinton agar. Absolute categorical agreement between NCCLS dilution and disk diffusion test results with these criteria ranged from 90.5 to 96.2%. Tiamulin susceptibility testing methods appear to be accurate in their categorical classification for indicated species, and their availability will allow immediate testing of animal isolates to guide therapy via appropriate levels of dosing and to monitor the development of resistance for agents in this unique class.

Humans↗

The human factor--the weakest link?

The German Animal-Laboratory-Information-System (ALIS) was used to assist the laboratory animal care program. The transmission of disease from man is a hazard to the health of laboratory animals. Mycoplasmas, Escherichia coli, staphylococci and Listeria were considered as hazards to laboratory animals. Special consideration was given to Escherichia coli strains of O groups 7 and 146 and to different lysotypes of Staphylococcus aureus. Important areas where human mistakes can be prevented are discussed. These include distance of animal quarters from processing areas, the diameter of sanitary sewers, air conditioning, noise, drinking water, cage changing procedures, wetting of animals, quarantine areas and separation of species. Training of laboratory animal technicians in Germany consists of both in-service and formal types. The formal training lasts 2 years. People selected for formal training should be tested to assure they are not allergic to laboratory animal dander.

Animal Husbandry↗

[Development of resistance in infectious agents of agricultural animals in Germany (1990-1994)--a review].

Antibiograms received from veterinary laboratories during the 1990-1994 period were recorded and evaluated with the aid of a computer program. Based on 70 tables giving information about th most important pathogens, the resistance behaviour of E. coli in cattle, swine, chicken, and turkey, that of Pasteurella haemolytica and P. multocida in cattle and swine and that of Staphylococcus aureus and Streptococcus agalactiae in cattle have been in synoptic form. Attention is drawn to the increase in resistance to enrofloxacin shown by E. coli, particularly in turkeys.

Animals↗

Listeria monocytogenes: silage, sandwiches and science.

Listeria monocytogenes is amongst the most intriguing and well studied of the pathogenic bacteria. However, the understanding and perspective one has of L. monocytogenes depends to a large extent on the microbiological issues with which one is faced as a part of your professional duties. The focus of the veterinary clinician or investigator is likely to be foremost on the neurologic (circling disease) and reproductive diseases L. monocytogenes causes. To the food microbiologist, the principal concern is to prevent introduction of L. monocytogenes into food products, or to identify its presence and prevent its multiplication to numbers of organisms that are likely to pose a substantial risk to humans who ingest the product. To the cellular immunologist, listeriosis represents a robust murine model that helped to elucidate many important concepts in innate and adaptive immunity, and L. monocytogenes is a potential vector for delivery of novel vaccines. To the student of molecular pathogenesis, L. monocytogenes is a powerful and well-characterized model organism for studying the cellular microbiology of an intracellular pathogen. In this brief overview, I will attempt to highlight some of the classical observations, and contemporary insights, on L. monocytogenes and listeriosis, and integrate these perspectives into a common framework. By so doing, I hope to provide those with one perspective on listeriosis with an appreciation of the broad array of problems and issues faced by those who focus on some other aspect of L. monocytogenes and its pathogenesis.

Animals↗

Protection of ewes vaccinated with A22 strain Chlamydia psittaci (ovis) against challenge in pregnancy with homologous and heterologous strains of the organism.

Fifty ewes were randomly divided into four groups. Groups A and B were vaccinated with an experimental vaccine derived from the A22 isolate of Chlamydia psittaci (ovis), an isolate known to cause ovine enzootic abortion (OEA). Groups C and D were unvaccinated controls. In mid-pregnancy, animals in group A and C were challenged with live A22 C. psittaci (ovis) and those in B and D were challenged with a field isolate of the organism (BS) against which the commercially available A22 vaccine appeared to offer poor protection. In group A, three animals showed clinical signs of OEA and six excreted chlamydiae. In group B, five ewes showed clinical signs of OEA and excreted chlamydiae. In group C, three ewes had clinical signs of OEA but seven excreted chlamydiae. In group D, all 11 ewes showed clinical signs of OEA and excreted chlamydiae in the products of parturition. This group produced only four live lambs with an average weight of viable lamb per ewe of 1.4 kg, whereas the other groups each produced 12 or 13 lambs with an average weight of viable lamb per ewe of more than 4 kg. The BS isolate was much more virulent than the A22 isolate for unvaccinated, pregnant ewes. However, the A22 vaccine offered significant protection against the heterologous BS isolate although on this occasion it did not appear to alter the course of disease produced by the less pathogenic A22 isolate.

Abortion, Veterinary↗

Corynebacterium pseudotuberculosis. A new cause of infectious and eosinophilic pneumonia.

A 28 year old veterinary medical student experienced spiking fever, cough, peripheral blood eosinophilia and an eosinophilic pulmonary infiltrate. Corynebacterium pseudotuberculosis was isolated from a transtracheal aspirate and bronchoscopy washings. C. pseudotuberculosis, a pathogen responsible for lymphadenitis in livestock, has never been reported to cause pneumonia in man. In the four cases of C. pseudotuberculosis previously reported, lymphadenitis was the chief clinical presentation. In our patient specific antibodies against the isolated C. pseudotuberculosis developed but not against the other corynebacteria. With erythromycin therapy, the peripheral blood eosinophilia and IgE anti-C. pseudotuberculosis titer decreased whereas the IgG titer continued to increase.

Adult↗

Comprehensive genomic analysis of antibiotic resistance plasmids in animal-associated Staphylococcus aureus in France.

UNLABELLED: In Staphylococcus aureus, an animal pathogen and zoonotic agent, plasmids play a pivotal role in the acquisition and spread of antibiotic resistance genes (ARGs). This study investigated the plasmid content of 329 S. aureus isolates from livestock and companion animals collected in France between 2010 and 2021. Plasmids (n = 211) were identified from 139 isolates. The major families identified-rep7a, rep20, and rep10-were associated with specific resistance genes (str, cat, blaZ, erm(C)) and exhibited widespread horizontal transfer across different S. aureus sequence types (STs) and animal hosts. In temporal analysis, the rep7a/str and rep7a/cat plasmids circulating in horses were progressively replaced by a rep7a plasmid carrying both str and cat genes. The study also highlighted the presence of mosaic plasmids, which combined elements from different bacterial species/genera, confirming the broad host range of S. aureus plasmids and their ability to acquire ARGs from diverse sources. Moreover, the occurrence of hybrid plasmids (carrying multiple rep genes) underscores the plasticity of these vectors of ARGs. This study emphasizes the need to investigate the mechanisms driving the spread and persistence of antibiotic-resistant plasmids in S. aureus, with a view to developing strategies aimed at combating antibiotic resistance. IMPORTANCE: The spread of antibiotic resistance in Staphylococcus aureus is a growing concern, particularly in animals that can serve as reservoirs for resistant strains. This study highlights the crucial role of plasmids in transmitting resistance genes among different animal hosts and S. aureus lineages. The characterization of 329 isolates collected over 10 years revealed how certain plasmid families are associated with specific resistance genes and how they evolve over time. The occurrence of mosaic and hybrid plasmids further underscores the ability of S. aureus to acquire resistance from diverse bacterial sources. These findings provide key insights into the mechanisms shaping antibiotic resistance in this pathogen and emphasize the fact that understanding plasmid-driven resistance is essential for developing effective interventions to limit the spread of multidrug-resistant S. aureus in both veterinary and human medicine.

Animals↗

Efficacy of extended ceftiofur intramammary therapy for treatment of subclinical mastitis in lactating dairy cows.

Little research has focused on treatment of cows with subclinical mastitis during lactation. Ceftiofur is a new broad-spectrum, third-generation cephalosporin antibiotic for veterinary use that inhibits bacterial cell wall synthesis by interfering with enzymes essential for peptidoglycan synthesis. Ceftiofur should be effective against a wide range of contagious and environmental mastitis pathogens. Objectives of the present study were to evaluate the efficacy of ceftiofur for treatment of subclinical mastitis in lactating dairy cows, and to determine if extended therapy regimens enhanced efficacy of ceftiofur. Holstein and Jersey dairy cows (n = 88) from 3 dairy research herds were used. Cows were enrolled in the study based on milk somatic cell counts >400,000/mL and isolation of the same mastitis pathogen in 2 samples obtained 1 wk apart. Cows with one or more intramammary infections (IMI) were blocked by parity and DIM and allocated randomly to 1 of 3 different ceftiofur treatment regimens: 2-d (n = 49 IMI), 5-d (n = 41 IMI), and 8-d (n = 38 IMI) treatment regimens. For all groups, 125 mg of ceftiofur hydrochloride was administered via intramammary infusion. Eighteen cows with 38 IMI were included as an untreated negative control group. A bacteriological cure was defined as a treated infected mammary quarter that was bacteriologically negative for the presence of previously identified bacteria at 14 and 28 d after the last treatment. Efficacy of ceftiofur therapy against all subclinical IMI was 38.8, 53.7, and 65.8% for the 2-, 5-, and 8-d ceftiofur treatment regimens, respectively. Four of 38 (10.5%) IMI in control cows were cured spontaneously without treatment. All 3 ceftiofur treatment regimens were significantly better than the negative control, and the 8-d extended ceftiofur treatment regimen treatment group was significantly better than the standard 2-d treatment group. Pathogen groups had significantly different cure rates from one another. The cure rate for the 8-d extended ceftiofur treatment regimen was 70% for Corynebacterium bovis, 86% for coagulase-negative Staphylococcus species, 36% for Staph. aureus, 80% for Streptococcus dysgalactiae ssp. dysgalactiae, and 67% for Strep. uberis.

Animals↗

[Occurrence and diagnostic relevance of virulence-associated factors in Streptococcus suis].

Streptococcus suis (Sc. suis) can cause very different clinical entities. In contrast to Sc. suis-associated pneumonia, the induction of meningitis, septicemia, and polyarthritis by certain Sc. suis strains requires the expression of virulence factors that contribute to the invasiveness of the pathogen. In the presented study, we examined the occurrence of known virulence-associated factors in Sc. suis isolates from samples sent to the Institute of Microbiology, School of Veterinary Medicine Hannover, in order to evaluate their significance as potential virulence factors in different disease complexes in Northern Germany. The results show that (i) MRP + EF + serotype 2 and MRP* EF-serotype 9 strains are statistically significant associated with the disease complex meningitis/septicemia/arthritis and, thus, have to be considered invasive strains, (ii) serotyping alone is not sufficient for identification of virulent strains, (iii) there is a remarkable heterogeneity among pneumonia-associated Sc. suis strains and (iv) activity of haemolysin or suilysin appears to be not appropriate as virulence marker. Finally, it has to be noted that at present only half of the Sc. suis isolates from pigs with meningitis/septicemia/poyarthritis can be characterised by the detection of virulence-associated factors. Thus, the identification and characterisation of additional, serotype independent virulence factors of Sc. suis is a very important issue in future studies.

Animals↗

Clinical characteristics and predictors of mortality for Cryptococcus gattii infection in dogs and cats of southwestern British Columbia.

Since 1999, Cryptococcus gattii has emerged as an important pathogen of humans and animals in southwestern British Columbia. Historically thought to be restricted to the tropics and subtropics, C. gattii has posed new diagnostic and treatment challenges to veterinary practitioners working within the recently identified endemic region. Clinical reports of canine and feline cryptococcosis caused by C. gattii diagnosed between January 1999 and December 2003 were included in this case series. The most common manifestations of disease were respiratory and central nervous system signs. Multivariate survival analysis revealed that the only significant predictor of mortality was the presence of central nervous system signs upon presentation or during therapy. Case fatality rates in both species were high. Further investigation into effective treatment regimes is warranted.

Animals↗

[Discovery of viroids and possible relationship with human and veterinary medicine].

The researches of DIENER and co-workers and those of the SEMANCIK'S group, have recently established that some plant diseases, such as potato spindle tuber, citrus exocortis disease and chrysanthemum stunt, are caused by a new class of pathogens, named viroids. These are the smallest known agents (they are smaller than viruses) having a molecular weight of ca 10(5) daltons, and composed of a highly structured RNA, rich in guanine-cytosine base pairs without a capsid. Little is known about the origin, replication model and pathogenic mechanism of viroids and until now only speculations are possible on these subjects. Some properties of the unknown agents of slow virus diseases (scrapie, Kuru, Creutzfeldt-Jakob disease and mink transmissible encephalopathy), suggest that these alterations in the central nervous system are caused by a sort of animal viroid.

Animals↗

Shared vector-borne zoonoses of the Old World and New World: home grown or translocated?

Humans inhabiting the Old World and New World share a wide variety of pathogens. Processes that result in the disjunct biogeographic distribution of pathogens with common vertebrate reservoirs or vectors are more difficult to unravel than those influencing the distribution of infections spread only through human-to-human transmission. The origins of species and complexes of tick-borne bacteria are unclear. The agent of Lyme borreliosis may have speciated in the New World following geographical isolation of ticks harboring ancestral spirochetes; the subsequent spread to Europe of B. burgdorferi sensu stricto may have occurred within historical times. Other tick-borne agents, such as the ehrlichiae causing human granulocytic ehrlichiosis, are genetically very similar in the Old World and New World. As the taxonomic distinctions among these related agents of human and veterinary importance appear increasingly blurred, the processes leading to the current discontinuous geographic distributions will also become the source of continuing speculation. Accumulating data suggest an Old World origin for a group of bacteria that include B. elizabethae, a human pathogen first identified from the New World. The potential public health significance of these newly described organisms is undefined, but of international interest as their vertebrate reservoir has been introduced throughout the world.

Animals↗

Antimicrobial susceptibility and molecular characterization of avian pathogenic Escherichia coli isolates.

Ninety-five avian pathogenic Escherichia coli (APEC) isolates recovered from diagnosed cases of avian colibacillosis from North Georgia between 1996 and 2000 were serotyped and examined for typical virulence-factors, susceptibility to antimicrobials of human and veterinary significance, and genetic relatedness. Twenty different serotypes were identified, with O78 being the most common (12%). The majority of the avian E. coli isolates (60%), however, were non-typeable with standard O antisera. Eighty-four percent of isolates were PCR positive for the temperature-sensitive hemagglutinin (tsh) gene and 86% positive for the increased serum survival (iss) gene. Multiple antimicrobial-resistant phenotypes (> or =3 antimicrobials) were observed in 92% of E. coli isolates, with the majority of isolates displaying resistance to sulfamethoxazole (93%), tetracycline (87%), streptomycin (86%), gentamicin (69%), and nalidixic acid (59%). Fifty-six E. coli isolates displaying resistance to nalidixic acid were co-resistant to difloxacin (57%), enrofloxacin (16%), gatifloxacin (2%), and levofloxacin (2%). DNA sequencing revealed point mutations in gyrA (Ser83-Leu, Asp87-Tyr, Asp87-Gly, Asp87-Ala), gyrB (Glu466-Asp, Asp426-Thr), and parC (Ser80-Ile, Ser80-Arg). No mutations were observed in parE. Twelve of the quinolone-resistant E. coli isolates were tolerant to cyclohexane, a marker for upregulation of the acrAB multi-drug resistance efflux pump. Quinolone-resistant isolates were further genetically characterized via ribotyping. Twenty-two distinct ribogroups were identified, with 61% of isolates clustering into four major ribogroups, indicating that quinolone resistance has emerged among multiple avian pathogenic E. coli serogroups and chromosomal backgrounds.

Animals↗

Nucleotide sequence and construction of an infectious cDNA clone of an EMCV strain isolated from aborted swine fetus.

A full-length cDNA clone of an Encephalomyocarditis virus (EMCV) strain (2887A) isolated from aborted swine fetus was constructed and sequenced. Sequence comparison showed more than 99% nucleotide and amino acid sequence identity with two other EMCV strains, EMCV-PV21 and -R. However, the 2887A genomic sequence showed only about 84% nucleotide identity and 96% amino acid identity with EMCV-B, -D and -PV2 variants. RNA synthesized by in vitro transcription of this cDNA clone was infectious upon transfection of BHK21 cells, as shown by cytopathic effects and identification by neutralization test, and by propagation of the virus released into the culture media. The transcript RNA led to the production of infectious particles despite the presence of two nongenomic nucleotide residues at the 5' end, the short poly(C) tract (C(10)TCTC(3)TC(10)), the short poly(A) tail (7A), and the presence of six nongenomic nucleotides at the 3' end. The rescued virus was also found to be highly pathogenic for mice by intra-peritoneal inoculation producing a fatal disease indistinguishable from that of wild-type virus. An important finding concerning the molecular basis of infectivity was that the in vitro synthesized EMCV RNA transcript is infectious, although it contains a very short poly(A). The availability of the infectious cDNA clone of the reproductive failure strain of EMCV should prove to be useful for studying the molecular basis of the pathogenicity of EMCV in pig.

Abortion, Septic↗

In vitro and in vivo pharmacodynamic properties of the fluoroquinolone ibafloxacin.

The pharmacodynamic properties of a new veterinary fluoroquinolone antimicrobial agent, ibafloxacin, were evaluated. Minimal inhibitory concentrations (MIC), time-kill kinetics, postantibiotic effect (PAE) and postantibiotic subminimal inhibitory concentration effects (PA-SME) were determined against pathogenic canine Gram-negative and Gram-positive bacterial isolates from dermal, respiratory and urinary tract infections. The synergistic interactions between ibafloxacin and its main metabolite, 8-hydroxy-ibafloxacin were investigated. Finally, the efficacy of ibafloxacin was tested in in vivo canine infection models. Ibafloxacin had good activity against Pasteurella spp., Escherichia coli, Klebsiella spp., Proteus spp. and Staphylococcus spp. (MIC90=0.5 microg/mL), moderate activity against Bordetella bronchiseptica, Enterobacter spp. and Enterococcus spp. (MIC50=4 microg/mL) and low activity against Pseudomonas spp. and Streptococcus spp. The time-killing analysis confirmed that ibafloxacin was bactericidal with a broad spectrum of activity. The PAE and PA-SME were between 0.7-2.13 and 1-11.5 h, respectively. Finally, studies in dog models of wound infection and cystitis confirmed the efficacy of once daily oral ibafloxacin at a dosage of 15 mg/kg. Additional studies are needed to better define the importance of AUC/MIC (AUIC) and Cmax/MIC ratios on the outcome of fluoroquinolone therapy in dogs.

Animals↗

Needlestick injury in clothing industry workers and the risks of blood-borne infection.

This paper identifies the hazard of a hollow needle device used extensively in the clothing industry and assesses the risk of transmission for HIV, Hepatitis B and Hepatitis C. A substantial risk of transmission is suggested and measures have been advised for its control. Occupational Health Physicians are advised to be aware of hollow needles in other industrial processes and where risks of cross-infection exist, the same safety considerations should be applied as in clinical medicine and veterinary work to avoid needlestick injuries. Needle sharing must be avoided.

Blood-Borne Pathogens↗