Kinetic Modelling of [68Ga]Ga-DOTA-Siglec-9 in Porcine Osteomyelitis and Soft Tissue Infections.

BACKGROUND: [68Ga]Ga-DOTA-Siglec-9 is a positron emission tomography (PET) radioligand for vascular adhesion protein 1 (VAP-1), a protein involved in leukocyte trafficking. The tracer facilitates the imaging of inflammation and infection. Here, we studied the pharmacokinetic modelling of [68Ga]Ga-DOTA-Siglec-9 in osteomyelitis and soft tissue infections in pigs. METHODS: Eight pigs with osteomyelitis and soft tissue infections in the right hind limb were dynamically PET scanned for 60 min along with arterial blood sampling. The fraction of radioactivity in the blood accounted for by the parent tracer was evaluated with radio-high-performance liquid chromatography. One- and two-tissue compartment models were used for pharmacokinetic evaluation. Post-mortem soft tissue samples from one pig were analysed with anti-VAP-1 immunofluorescence. In each analysis, the animal's non-infected left hind limb was used as a control. RESULTS: Tracer uptake was elevated in soft tissue infections but remained low in osteomyelitis. The kinetics of [68Ga]Ga-DOTA-Siglec-9 followed a reversible 2-tissue compartment model. The tracer metabolized quickly; however, taking this into account, produced more ambiguous results. Infected soft tissue samples showed endothelial cell surface expression of the Siglec-9 receptor VAP-1. CONCLUSION: The kinetics of [68Ga]Ga-DOTA-Siglec-9 uptake in porcine soft tissue infections are best described by the 2-tissue compartment model.

Laboratory diagnostics, phylogenetic analysis and clinical outcome of a subcutaneous Mycoleptodiscus indicus infection in an immunocompetent cat.

BACKGROUND: Mycoleptodiscus indicus is a dematiaceous hyphomycete fungus found on plant leaves. It has been rarely reported as a cause of human or animal disease, possibly because it is difficult to culture and identify from clinical specimens. Infections are presumably acquired by traumatic implantation. CASE PRESENTATION: An 8-year-old non-immunosuppressed cat from Georgia, USA, presented with a left front leg swelling without lameness. Cytology from a fine needle aspirate revealed pyogranulomatous inflammation with both cytoplasmic and extracellular fungal elements. There were septate hyphae with irregularly sized segments, non-staining uneven walls, and rounded yeast-like forms from which longer hyphae arose in a hub-and-spoke pattern. A mold was isolated on agar from a fine needle aspirate collected 1 week later and identified as M. indicus by morphology, DNA sequencing and phylogenetic analysis. The cat recovered completely and uneventfully with antifungal treatment. CONCLUSIONS: We report a previously undescribed presentation of M. indicus causing a subcutaneous infection in a cat with successful antifungal treatment. In this study we highlight the potential of M. indicus to infect immunocompetent animals, and the veterinary medical community should be aware of its unusual but characteristic clinical, microbiological and cytologic presentation.

Comparison of livestock-associated and community-associated Staphylococcus aureus pathogenicity in a mouse model of skin and soft tissue infection.

Industrial hog operation (IHO) workers are at increased risk of carrying Staphylococcus aureus in their nares, particularly strains that are livestock-associated (LA) and multidrug-resistant. The pathogenicity of LA-S. aureus strains remains unclear, with some prior studies suggesting reduced transmission and virulence in humans compared to community-associated methicillin-resistant (CA-MRSA) S. aureus. The objective of this study was to determine the degree to which LA-S. aureus strains contracted by IHO workers cause disease relative to a representative CA-MRSA strain in a mouse model of skin and soft tissue infection (SSTI). Mice infected with CC398 LA-S. aureus strains (IHW398-1 and IHW398-2) developed larger lesion sizes with higher bacterial burden than mice infected with CA-MRSA (SF8300) (p < 0.05). The greatest lesion size and bacterial burden was seen with a CC398 strain that produced a recurrent SSTI in an IHO worker. The LA-S. aureus infected mice had decreased IL-1ß protein levels compared with CA-MRSA-infected mice (p < 0.05), suggesting a suboptimal host response to LA-S. aureus SSTIs. WGSA revealed heterogeneity in virulence factor and antimicrobial resistance genes carried by LA-S. aureus and CA-MRSA strains. The observed pathogenicity suggest that more attention should be placed on preventing the spread of LA-S. aureus into human populations.

Emergence of Resistance to Macrolides and Rifampin in Clinical Isolates of Rhodococcus equi from Foals in Central Kentucky, 1995 to 2017.

The objective of this study was to determine the prevalence of Rhodococcus equi strains resistant to macrolides and rifampin over time in clinical samples from foals submitted to diagnostic laboratories in central Kentucky. We performed a retrospective observational study of all clinical samples from foals that were submitted to veterinary diagnostic laboratories in Kentucky between January 1995 and December 2017. Samples were included if the R. equi bacterium was cultured and tested for in vitro susceptibility to erythromycin or rifampin. In vitro susceptibility testing to erythromycin was available for 2,169 isolates of R. equi, while susceptibility testing to both erythromycin and rifampin was available for 1,681 isolates. Rifampin resistance was first detected in 2000, and erythromycin resistance was first detected in 2004. Between 1995 and 2006, the proportion of resistant isolates of R. equi was 0.7% for erythromycin and 2.3% for rifampin. There was a significant (P < 0.001) increase in the proportion of resistant R. equi between 2007 and 2017, with 13.6% of isolates being resistant to erythromycin and 16.1% being resistant to rifampin. Between 2007 and 2017, isolates of R. equi resistant to erythromycin or rifampin were significantly less likely to be isolated from feces than from the respiratory tract, other soft tissues, or musculoskeletal infections. The considerable increase in the prevalence of isolates of R. equi resistant to macrolides and rifampin since 2007 is of concern for both human and animal health.

Antimicrobial resistance in clinical Escherichia coli isolated from companion animals in Australia.

Multidrug-resistant (MDR) Escherichia coli have become a major public health concern to both humans and animal health. While the frequency of antimicrobial resistance (AMR) in clinical E. coli is monitored regularly in human medicine, current frequency of AMR in companion animals remains unknown in Australia. In this study we conducted antimicrobial susceptibility testing (AST) and where possible, determined potential risk factors for MDR infection among 883 clinical Escherichia coli isolated from dogs (n=514), cats (n=341) and horses (n=28). AST was undertaken for 15 antimicrobial agents according to the Clinical Laboratory Standards Institute (CLSI) guidelines and interpreted using epidemiological cut-off values (ECOFFs) as well as CLSI veterinary and human clinical breakpoints. The AST revealed complete absence of resistance to carbapenems while resistance to amikacin was observed at a low level in isolates from dogs (1.6%) and cats (1.5%) compared to horses (10.7%). Among dog isolates, resistance to fluoroquinolones ranged from 9.1%-9.3% whereas among cat isolates, it ranged from 3.2%-5%. Among dog isolates, the proportion showing a 3rd generation cephalosporin (3GC) non-wild type phenotype was significantly higher (P<0.05) in skin and soft tissue infection (SSTI, n=122) isolates (17.2%-20.5%) compared to urinary tract infection (UTI, n=392) isolates (9.9%-10.2%). The frequency of multidrug resistance was 18.1%, 11.7% and 42.9% in dog, cat and horse isolates, respectively. Risk factor analysis revealed that MDR E. coli isolated from UTI were positively associated with chronicity of infection and previous antimicrobial treatment. Dogs and cats with chronic UTI that had been previously treated with antimicrobials were eight times and six times more likely to be infected with MDR E. coli compared to dogs and cats with non-chronic UTI, and no history of antimicrobial treatment, respectively. This study revealed that pre-existing disease condition and prior antimicrobial use were the major risks associated with UTI with MDR E. coli in companion animals.

FATAL SUPPURATIVE INFLAMMATION IN DAURIAN PIKAS (OCHOTONA DAUURICA) NATURALLY INFECTED WITH CASTELLANIELLA GINSENGISOLI-LIKE BACTERIA.

Fifteen Daurian pika (Ochotona dauurica) were introduced to a zoological collection in December 2011 as founders for a planned breeding colony. Despite breeding success, the colony shrunk over 37 mo to 11 animals. Mortality in 11 of 46 deceased animals, including wild-caught "founders" and captive-born offspring, was associated with a suppurative inflammation and abscess formation of the spleen, skin, peripheral and internal lymph nodes, liver, lungs, kidney, or a combination of organs. Gram-negative, non-fermenting, rod-shaped bacteria were isolated from the abscesses in all cases. Steiner Chapman silver stain identified rod-shaped bacteria in the abscesses of seven animals. The bacteria were not detected with Gram stain, acid-fast stain, or Grocott silver methenamine stain and was not detectable by periodic acid-Schiff reaction. In two cases, including the index case, the bacteria were presumptively identified as Ralstonia pickettii on the basis of conventional biochemical characterization. The bacteria in the other cases were not further classifiable with conventional methods. Matrix-assisted laser desorption/ionization time of flight mass spectrometry and 16s rDNA gene sequencing resulted in identification to the genus level as Castellaniella in 10 of 12 cases. Comparative 16S rDNA gene sequence analysis showed that these isolates and Castellaniella ginsengisoli Strain DCY36T were 99% similar. Castellaniella ginsengisoli, a gram-negative bacterium isolated from soil of a ginseng field in South Korea, has not previously been associated with disease in animals or humans. It is uncertain how the bacterium was introduced to the Daurian pika colony or how it spread.

Paravertebral masses in blue-tailed monitor, Varanus dorianus, indicative of soft-tissue infection with associated osteomyelitis.

Paravertebral osseous masses in reptiles have been attributed to Paget's disease on the basis of histology. Histologically recognized mosaic architecture and cement lines, however, lack specificity. A Varanus dorianus with this condition was subjected to standard and computerized tomography. Because the masses were extraskeletal in nature, Paget's disease could be excluded. Although interpretation of the computed tomography suggested the process to be entirely extraskeletal, standard radiographs revealed disorganized vertebral architecture characteristic of osteomyelitis, crossing intervertebral spaces. Posttraumatic myositis ossificans and calcified hematoma were confidently excluded as diagnoses. The etiology of paraspinal masses in this V. dorianus appears attributable to infection, with infection of a puncture wound hypothesized as the underlying process. If one extrapolates the findings in this one animal, it seems reasonable to suggest that consideration be given to investigating the possibility of an infectious origin when similar masses are recognized in other reptiles.

Clonal diversity, virulence-associated genes and antimicrobial resistance profile of Staphylococcus aureus isolates from nasal cavities and soft tissue infections in wild ruminants in Italian Alps.

Staphylococcus aureus is a commensal and a pathogenic bacterium that causes a wide variety of diseases in humans and animals with a high impact on public health and the livestock industry. S. aureus virulence pattern, antimicrobial resistance profile and host specialization are of great concern both in livestock and in companion animals. Concerning wild animals, S. aureus carriage and antimicrobial resistance profile has been recently investigated in free-ranging species both in aquatic and terrestrial environment. Here we report genotyping (spa typing, Multilocus Sequence Typing and SCCmec typing), virulence and antimicrobial resistance profile of four S. aureus isolated in Alpine chamois (Rupicapra r. rupicapra) and roe deer (Capreolus capreolus), euthanized due to walking impairment and signs of disorientation. S. aureus was isolated from nasal cavities in both wild ruminant species and in soft tissue infections in chamois. A marked S. aureus genetic heterogeneity was detected: spa type t1523, sequence type 45 (Clonal Complex 45), and spa type t1328, ST22 (CC22) from the nasal cavities and the liver of a chamois kid respectively, t1773, ST700 (CC130) from an adult chamois abscess, and a new sequence type, ST2712, belonging to CC97 from the roe deer nasal cavities. One of the main findings was the confirmation that the t1328, ST22 isolate, obtained from the liver of the chamois kid, was a methicillin-resistant S. aureus (MRSA) harbouring a SCCmec cassette type IV. The set of virulence marker and toxin genes investigated showed profiles characteristic of the S. aureus lineages detected, including those of the human adapted ST (CC) 22 and ST (CC) 45 isolates.

Livestock associated MRSA (LA-MRSA) and its relevance for humans in Germany.

Livestock-associated Staphylococcus aureus (LA-MRSA) are mainly associated with the clonal complex (CC) 398. Although having its main reservoir as MRSA in livestock such as pigs, poultry or cattle LA-MRSA CC398 has no pronounced host specificity and can colonize or infect other animals such as horses and dogs and also humans. In German conventional farming systems nasal colonization of the animals and of humans occupationally exposed to them (up to 86%) are frequent. Further human-to-human dissemination in households occurs more rarely in general (∼4% of humans living on farms but without occupational exposition). Nasal colonization with LA-MRSA of humans at hospital admission is found in 0.08-0.2% for Germany in general. However, this proportion is higher in areas with a high density of livestock production such as in northwestern North Rhine-Westphalia or Lower Saxony. LA-MRSA CC398 is not less pathogenic for humans than S. aureus in general. Hence, LA-MRSA accounts for ∼15% of all MRSA isolates from deep-seated skin and soft-tissue infections in the community and for about 0.8-2% of all MRSA isolated from clinical specimens obtained in hospital settings. When introduced into the hospital it can cause postoperative wound infections and even septicemia. Differently from hospital-associated MRSA clones, LA-MRSA CC398 has obviously limited capacity to spread in the nosocomial setting so far (proportion of ∼1.8% among MRSA from nosocomial infections, the proportion among MRSA from blood cultures is ∼1%).

Subcutaneous botryomycosis due to Bibersteinia trehalosi in a Texas Longhorn steer.

A 3-year-old Texas Longhorn steer had a long history of progressive swelling of the soft tissues of the jaw and neck. At necropsy, multifocal to coalescing dermal and subcutaneous pyogranulomas were surrounded by fibrous tissue. Microscopically, the pyogranulomas contained aggregates of gram-negative coccobacilli surrounded by Splendore-Hoeppli material and were separated by bands of fibrovascular tissue (botryomycosis). Phylogenetic analysis of multilocus sequence-typing data revealed that the bacteria recovered in pure culture from swabs of submandibular tissue were most closely related to Bibersteinia [Pasteurella] trehalosi. The bacterial colonies were immunohistochemically reactive with a rabbit polyclonal anti-Pasteurella class C acid phosphatase antibody. Botryomycosis is a pyogranulomatous inflammation caused by a variety of nonbranching, nonfilamentous bacteria that elicit the formation of Splendore-Hoeppli material. This case of botryomycosis is unique for its association with Bibersteinia trehalosi.

Subcutaneous Mycoleptodiscus indicus infection in an immunosuppressed dog.

An 8-year-old dog presented with several dermal excoriations. Lesion cytology revealed pyogranulomatous inflammation with branching, septate hyphae. A mold identified as Mycoleptodiscus indicus by morphology and sequencing was cultured from fine-needle aspirates. This is the first report of a Mycoleptodiscus species as an etiologic agent in a dog.

The prevalence of carriage of meticillin-resistant staphylococci by veterinary dermatology practice staff and their respective pets.

It has been shown that people and pets can harbour identical strains of meticillin-resistant (MR) staphylococci when they share an environment. Veterinary dermatology practitioners are a professional group with a high incidence of exposure to animals infected by Staphylococcus spp. The objective of this study was to assess the prevalence of carriage of MR Staphylococcus aureus (MRSA), MR S. pseudintermedius (MRSP) and MR S. schleiferi (MRSS) by veterinary dermatology practice staff and their personal pets. A swab technique and selective media were used to screen 171 veterinary dermatology practice staff and their respective pets (258 dogs and 160 cats). Samples were shipped by over-night carrier. Human subjects completed a 22-question survey of demographic and epidemiologic data relevant to staphylococcal transmission. The 171 human-source samples yielded six MRSA (3.5%), nine MRSP (5.3%) and four MRSS (2.3%) isolates, while 418 animal-source samples yielded eight MRSA (1.9%) 21 MRSP (5%), and two MRSS (0.5%) isolates. Concordant strains (genetically identical by pulsed-field gel electrophoresis) were isolated from human subjects and their respective pets in four of 171 (2.9%) households: MRSA from one person/two pets and MRSP from three people/three pets. In seven additional households (4.1%), concordant strains were isolated from only the pets: MRSA in two households and MRSP in five households. There were no demographic or epidemiologic factors statistically associated with either human or animal carriage of MR staphylococci, or with concordant carriage by person-pet or pet-pet pairs. Lack of statistical associations may reflect an underpowered study.

Salmonella Michigan soft tissue infection in an immunocompromised child.

A rare case of soft tissue infection due to Salmonella Michigan in an immunocompromised child is reported. The same organism was isolated from a tortoise kept in the home. Immunocompromised patients are especially susceptible to reptile-associated salmonellosis and should be advised appropriately.

Clinical efficacy of ampicillin, pivampicillin and procaine penicillin G in a soft tissue infection model in ponies.

Tissue chambers, implanted subcutaneously in ponies, were inoculated with Streptococcus zooepidemicus. The animals received either no antibiotics or one of the following treatments: pivampicillin per os (19.9 mg/kg, equivalent to 15 mg/kg ampicillin, every 12 h) for 7 or 21 days (7 and 5 ponies, respectively), procaine penicillin G intramuscularly (12 mg/kg = 12,000 IU/kg, every 24 h) for 7 days (7 ponies), or ampicillin sodium intravenously (equivalent to 15 mg/ kg ampicillin, every 8 h) for 1 day (5 ponies). Only intravenous administration was started before infection (prophylactically), the other treatments were started 20 h after infection (curatively). A total of 7 ponies received no antibiotics. In untreated controls, the infection led to abscessation of the tissue chamber in 4 to 10 days. Curative treatment with either pivampicillin or procaine penicillin G for 7 days resulted in a reduction of viable bacteria in the tissue chamber but did not eliminate the infection, resulting in abscessation in 5 to 14 days. However, administration of pivampicillin for 21 days eliminated the streptococci in five out of five ponies and prophylactic administration of ampicillin was successful in three out of five ponies.

Characterization of a sterile soft-tissue inflammation model in thoroughbred horses.

This paper describes the use of subcutaneously-placed tissue chambers as a sterile soft-tissue inflammation model in Thoroughbred horses. Acute, non-immune inflammation was initiated by injecting a sterile lambda carrageenan solution into a tissue chamber. This model was used to study the temporal changes in oxygen and carbon dioxide tensions, pH, bicarbonate, protein, albumin, prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) concentrations, cell counts and differential counts in tissue fluid from inflamed tissue chambers and control chambers. Skin temperatures over control and inflamed chambers were also compared. Carrageenan-induced inflammation resulted in significant increases in tissue-fluid carbon dioxide tension, leucocyte count, albumin, and PGE2 and LTB4 concentrations. It also resulted in a significant decrease in tissue fluid pH and HCO3-concentration. Inflammation did not result in significant changes in tissue-fluid protein concentration, differential cell counts or skin temperature over the chambers. The use of this type of tissue chamber is well-suited for studying the pathophysiology of a self-contained, non-immune inflammatory process. The model described in this paper could prove to be very useful in studies of the distribution of anti-inflammatory drugs and the effects of such drugs on various aspects of the inflammatory process.