Mycobacterioses in cats: ABCD guidelines on prevention and management

Mycobacterium porcinum panniculitis in a cat from northern California

Case summary

A 9-year-old male castrated domestic shorthair cat from northern California was evaluated for a 12-month history of dermal and subcutaneous dermatitis in the inguinal region. Histopathologic examination of a biopsy revealed severe, chronic, multifocal to coalescing pyogranulomatous dermatitis and panniculitis, accompanied by ulceration and central necrosis. Aerobic bacterial culture of lesions yielded mycobacterial growth. Empiric antimicrobial therapy was initiated with doxycycline and marbofloxacin pending culture and susceptibility. Culture of a biopsy followed by rpoB gene sequencing at a mycobacterial reference laboratory yielded Mycobacterium porcinum after 6 weeks. Ten months after initial antimicrobial administration, the lesions resolved.

Relevance and novel information

To date, in cats, M porcinum panniculitis has been reported from Ohio, Massachusetts and British Columbia in North America; two additional cases were reported from southeastern Australia. In humans, M porcinum infections have been reported from several states in the USA, predominantly in the Midwest and coastal south, but not from the west. This report extends the known spatial distribution of M porcinum to the western USA and strengthens its association with panniculitis in cats. It also demonstrates the need for prolonged incubation for diagnosis of some rapidly growing mycobacteria infections using culture.

Atypical presentation of disseminated mycobacteriosis due to Mycobacterium avium in an aged cat

In cats, mycobacteriosis tends to present in a syndromic manner, with cases either being due to tuberculosis (TB) (in countries where TB is endemic), one of the "leprosy-like" diseases affecting the skin and subcutis, panniculitis caused by infection of subcutaneous tissues generally with rapidly growing Mycobacteria spp. or widely disseminated granulomatous disease, which is usually caused by members of the Mycobacterium avium-intracellulare complex (MAC). Disseminated MAC disease is rare, but when it occurs, usually develops in immunocompromised hosts with defective cell-mediated immunity. This report describes a case of widely disseminated mycobacteriosis in a 10-year-old American Shorthair cat with an atypical multi-organ distribution including rarely documented thyroid gland involvement. The cat presented for a chronic history of inappetence and weight loss. Abdominal ultrasonography revealed a large mass on the left kidney, and an aspirate (FNA) from this mass showed abundant negative-staining bacilli which were confirmed to be acid-fast with Ziehl-Neelsen (ZN) staining. This was consistent with a mycobacterial aetiology. Necropsy revealed mycobacterial granulomas and/or granulomatous inflammation in the kidneys, thyroid gland, liver, spleen, lungs and left mandibular lymph node, with abundant intralesional acid-fast bacilli in all these tissues. Polymerase chain reaction (PCR) and culture on samples of all affected tissues were positive for M. avium. Collectively, the findings are consistent with disseminated mycobacteriosis due to M. avium with atypical distribution of lesions. Very likely, the cat had underlying immunodeficiency of undetermined cause, exacerbated by the administration of depot corticosteroid.

[Pulmonary Mycobacterium avium infection in 2 domestic cats]

Two domestic cats (Abyssinian and Carthusian) presented with chronic respiratory signs including cough, respiratory sounds, and polypnea. One of the cats also showed intermittent fever. Thoracic radiographs demonstrated severe changes with predominantly micronodular interstitial lung patterns, some with mineralized areas. Bronchoalveolar lavage detected high-grade pyogranulomatous airway inflammation. A cytological examination for acid-fast bacteria and a PCR for Mycobacteria species of the bronchoalveolar lavage fluid (BALF) were negative in both cats. A culture for Mycobacteria of the BALF detected Mycobacterium avium subspecies in both cats. While the clinical signs, but not the radiographic findings, could be controlled in one cat with prolonged double antibiotic therapy, the other cat developed septic peritonitis shortly after diagnosis and was euthanized. In unexplained chronic respiratory disease in cats, mycobacterial infection should be considered as a differential diagnosis. The breed of the first patient is consistent with the known predisposition for Abyssinians.

Genomics Insights into Mycolicibacterium Hassiacum Causing Infection in a Cat with Pyogranulomatous Dermatitis and Panniculitis

Mycolicibacterium hassiacum (homotypic synonym: Mycobacterium hassiacum) represents an ungrouped thermotolerant rapidly growing mycobacteria (RGM) species occasionally associated with infections and disease in humans. In this report, we describe a case of pyogranulomatous dermatitis and panniculitis due to M. hassiacum in an immunocompetent adult cat. To the best of our knowledge, this represents the first report of M. hassiacum infection in animals. We also report the results of the in-depth genome characterization of the isolate using a combined short- and long-read whole-genome sequencing (WGS) approach. We observed the lack of acquired-resistance genes and no evidence of mutations in housekeeping genes associated with resistance to rifampicin and isoniazid. We detected some virulence factors in our isolate, such as some associated with the interaction of mycobacteria with host cells, and the presence of multiple copies of heavy metal resistance genes (arsB, arsR, and arsL/cadL). In conclusion, M. hassiacum should be included among the RGM species associated with feline subcutaneous atypical mycobacteriosis (SAM). A reliable and fast RGM laboratory identification and characterization is important not only for an accurate etiological diagnosis but also for a correct approach to SAM treatment options.

Doing more with less: multiple uses of a single slide in veterinary cytology. A practical approach

Veterinary cytology faced a remarkable evolution in the last 15 years, in part due to increase recognition of the advantages of the cytology by veterinary clinicians. Simultaneously, there has been a growing awareness by the owners about the importance of a complete diagnostic workup aimed at defining a proper treatment protocol. With the extended use of cytology, challenging diagnostic cases are more frequent, and more clinically useful answers are requested. In this scenario, the use of cytology specimens to perform ancillary techniques is a valid approach. Rather than being simply archived, cytology slides can be a valuable source and a good platform to carry out cytochemistry, immunocytochemistry, and molecular techniques. Therefore, several diagnostic techniques can be applied in tiny samples, thus following the "doing more with less" principle. The aim of this approach is to refine the cytologic diagnosis and provide additional prognostic and therapeutic information. Herein, we detailed this principle in veterinary cytology and reviewed the use of cytology specimens for ancillary techniques as a single procedure, i.e., using the whole slide, or multiple procedures, i.e., multiple procedures applied in the same slide.

Cutaneous Mycobacterium goodii infection in an immunocompetent cat in Louisiana: clinical presentation, molecular identification, antimicrobial susceptibility and management

Case summary

A 9-year-old spayed female domestic shorthair cat was presented to a referral hospital for management of recurring non-healing ulcerations and a subcutaneous mass on the ventral abdomen. Prior treatment included antibiotics (cefovecin followed by clindamycin), wound cleaning and surgical debulking, but the ulcerations and mass recurred 1 month after surgical removal. At this point, the cat was started on doxycycline and pradofloxacin and referred for further work-up. The culture of skin biopsy specimens obtained at the time of referral revealed a population of bacterial colonies with two distinctly different phenotypes. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and 16S rRNA gene sequencing identified both colonies as Mycobacterium goodii. A diagnosis of a cutaneous infection of rapidly growing mycobacteria was made, and treatment with oral pradofloxacin and doxycycline was initiated. The ulcerations resolved within 4 months, and the subcutaneous mass gradually decreased in size until it was no longer palpable, even 4 months after the cessation of antibiotics.

Relevance and novel information

This is the second reported feline cutaneous M goodii infection in North America. The organism was not visualized on histopathology but was successfully cultured from tissue obtained by skin punch biopsy. A phenotypic switching phenomenon affecting the susceptibility results was suspected, possibly explaining the presence of phenotypically different but genetically identical strains. This case highlights the importance of submitting aseptically obtained tissue, fluid or fine-needle aspirates for culture and species identification, as well as histopathology, when infection with higher bacteria, such as rapidly growing mycobacteria, is suspected.

Mycobacterium setense isolated from a cat with atypical mycobacterial panniculitis

Atypical mycobacterial panniculitis was diagnosed in a cat. Mycobacterium setense was identified as causative agent by 16 S rRNA gene sequence analysis. This a gram-positive rod-shaped acid-fast bacterium belonging to Mycobacterium fortuitum group was never reported before in diseased animals. Resistance to doxycycline and clarithromycin was detected. During treatment with pradofloxacin, additional resistance to fluoroquinolones developed which was due to a mutation in the gyrase gene gyrA (S90W exchange). Despite of antimicrobial treatment for 33 months the patient did not fully recover. Species identification and susceptibility testing for choosing adequate antimicrobial treatment is recommended in cases of feline mycobacterial panniculitis.

Distinguishing Between Dermatologic Disorders of the Face, Nasal Planum, and Ears: Great Lookalikes in Feline Dermatology

Facial dermatitis in cats can be caused by a broad range of infectious, allergic, immune-mediated and neoplastic disorders with very different treatments and prognoses. Baseline dermatologic diagnostics (skin scrapings for mites, cytology for infection and to characterize inflammatory infiltrate, and dermatophyte culture) are required, as well as possible further diagnostics, including therapeutic trials for parasites and feeding a hypoallergenic diet, bacterial culture, and skin biopsies for histopathology in order to achieve a diagnosis. Clinical presentations of diseases affecting different parts of the feline face are presented and discussed.

Non-tuberculous Mycobacteria can Cause Disseminated Mycobacteriosis in Cats

Mycobacteriosis caused by non-tuberculous mycobacteria (NTM) is a rising concern in human medicine both in immunocompromised and immunocompetent patients. In cats, mycobacteriosis caused by NTM is considered mostly to be a focal or dermal infection, with disseminated disease mostly caused by Mycobacterium avium. We describe three cases of disseminated mycobacteriosis in cats, caused by Mycobacterium malmoense, Mycobacterium branderi/shimoidei and M. avium, with no identified underlying immunosuppression. In all cases, extracellular mycobacteria were seen in the pulmonary epithelium, intestinal lumen and glomerular tufts, which could affect the shedding of the organism. The present study highlights the importance of mycobacteriosis as a differential even in immunocompetent animals. Considering the close relationship of owners and pets and the potential presence of free mycobacteria in secretions, cats should be considered as a possible environmental reservoir for mycobacteria.

Felis Punctatis: Cat Claw-induced Punctures

Animal-induced conditions in humans predominantly present as infectious zoonoses. However, trauma-associated injuries from the teeth or claws can also occur. Several zoonotic infections can be transmitted by cats, a common household pet, to their owners. The clinical features of a woman who developed multiple sites of trauma-induced cutaneous punctures from her cat’s paws while it was kneading on her clothes-covered abdomen are described. The repetitive insertion and withdrawal of the sharp tips of the cat’s claws created distinctive groups of erythematous punctures on the patient’s skin. We suggest that Latin nomenclature be used to designate the name for this claw-induced dermatosis that includes not only the causative animal (felis for cat) but also a descriptive term for the skin lesions (punctatis for punctures): felis punctatis.

Mycobacterial panniculitis caused by Mycobacterium thermoresistibile in a cat

CASE SUMMARY

A domestic shorthair cat was evaluated for chronic, bilateral, ulcerative dermatitis affecting the inguinal region and lateral aspects of both pelvic limbs. Histopathologic examination of skin biopsies collected throughout the course of disease revealed chronic pyogranulomatous ulcerative dermatitis. Aerobic bacterial skin cultures yielded growth of a methicillin-resistant Staphylococcus aureus and Corynebacterium amycolatum. Upon referral the clinical findings were suggestive of a non-tuberculous Mycobacterium species infection. Previously obtained skin cultures failed to yield growth of mycobacterial organisms. A deep skin biopsy was collected and submitted for mycobacterial culture. At 5 weeks of incubation Mycobacterium thermoresistibile was isolated. In previous reports, M thermoresistibile has been isolated after 2-4 days of incubation, suggesting that this strain may have been a slower growing variant, or other factors (such as prior antimicrobial therapy) inhibited rapid growth of this isolate. The cat was hospitalized for intravenous antibiotic therapy, surgical debridement of wounds, vacuum-assisted wound closure therapy and reconstruction procedures. The wounds were ultimately primarily closed and the cat was discharged to the owner after 50 days of hospitalization. Seven months after hospitalization, the ulcerative skin lesions had healed.

RELEVANCE AND NOVEL INFORMATION

To our knowledge, only two cases of M thermoresistibile panniculitis have been reported in cats. In the only detailed report of feline M thermoresistibile panniculitis, treatment was not attempted. The second case only reported detection of M thermoresistibile by PCR without a clinical description of the case. In our case report, severe chronic skin infection with M thermoresistibile was addressed using prolonged specific antibiotic therapy, surgical debridement and reconstructions, and treatment of secondary bacterial infections.

An outbreak of bovine tuberculosis in a fallow deer herd (Dama dama) in Sicily

Wild ruminants have an important role in the epidemiology of bovine tuberculosis (bTB). This study describes an outbreak of bovine tuberculosis occurring in a fallow deer herd in Sicily. In 2012 a Sicilian herd of 47 animals was referred for cachexia. Pathological examination of 2 dead animals revealed disseminated granulomas predominantly involving the skin and subcutaneous tissues. Tissue samples were submitted for histological analysis, bacteriological culture, and biomolecular assay. PCR analysis identified Mycobacterium strains. Genotyping by spoligotyping and MIRU-VNTR profiles identified Mycobacterium bovis spoligotype SB0120 in both animals. In 2014, bTB skin testing of 28 fallow deer from the same group was positive in 4 and inconclusive in another 4. All 8 positive/inconclusive reactors were euthanized. Disseminated granulomatous lesions were noted in 6 of these animals, 3 of which (2 positive and 1 negative to skin tests) also presented cutaneous lesions. M. bovis spoligotype SB0120 was identified from all animals in which tuberculous-like lesions were observed, including 2 negative reactors. Many of the animals involved in this outbreak presented diffuse skin lesions, a potential route of transmission of M. bovis infection. Given the epidemiological role wildlife play in the maintenance of bTB infection and its potential risk for humans, a comprehensive monitoring plan for this zoonosis in wildlife species in Sicily is needed.

Susceptibility of rapidly growing mycobacteria isolated from Australian cats to ivermectin, moxidectin, ceftiofur and florfenicol

OBJECTIVES

Rapidly growing mycobacteria (RGM) infections in cats typically manifest as a panniculitis, requiring long-term antimicrobial therapy for resolution. The search for novel antimicrobial therapies to reduce treatment duration and improve the rate of clinical resolution is imperative. Accordingly, RGM isolates underwent susceptibility testing to some avermectins and other antibacterial drugs currently available.

METHODS

Five Mycobacterium fortuitum and six Mycobacterium smegmatis isolates obtained from Australian cats underwent susceptibility testing by microbroth dilution to ivermectin, moxidectin, ceftiofur and florfenicol.

RESULTS

All isolates were resistant to the highest concentrations of ivermectin, moxidectin and ceftiofur tested (1024 µg/ml, 256 μg/ml and 32 μg/ml, respectively). All isolates of M fortuitum were resistant to the highest concentration of florfenicol tested (128 µg/ml). The minimum inhibitory concentration range of florfenicol that inhibited growth of M smegmatis isolates was 32-64 µg/ml.

CONCLUSIONS AND RELEVANCE

All drugs appear to have no efficacy in vitro for the treatment of RGM infections.

In vitro interaction of some drug combinations to inhibit rapidly growing mycobacteria isolates from cats and dogs and these isolates' susceptibility to cefovecin and clofazimine

OBJECTIVES

To investigate whether selected drug combinations used to treat rapidly growing mycobacteria (RGM) have drug-drug interactions that affect efficacy and to investigate each isolate's susceptibility to cefovecin and clofazimine, individually.

DESIGN

In vitro susceptibility testing of bacterial isolates.

METHODS

Initially, five feline isolates and one canine isolate from both Mycobacterium fortuitum and M. smegmatis clusters (n = 12) underwent microbroth susceptibility testing to individual drugs to establish minimum inhibitory concentrations (MIC) of cefovecin, ciprofloxacin, clarithromycin, clofazimine, doxycycline, enrofloxacin, trimethoprim and sulfanilamide (the latter two as a combination). Checkerboard assays were then performed for susceptible M. smegmatis isolates for the following combinations: clarithromycin (one isolate only) versus enrofloxacin, clarithromycin vs doxycycline, clarithromycin vs trimethoprim/sulfanilamide; enrofloxacin vs doxycycline (six isolates); enrofloxacin vs trimethoprim/sulfanilamide (six isolates). Susceptible M. fortuitum isolates were tested against enrofloxacin versus doxycycline (four isolates only).

RESULTS

All six M. fortuitum isolates were susceptible to enrofloxacin, but only four of six were susceptible to doxycycline. All six M. smegmatis isolates were susceptible to doxycycline, enrofloxacin and trimethoprim/sulfanilamide. A single isolate from the 12, a M. smegmatis isolate, was susceptible to clarithromycin. The fractional inhibitory concentration of each drug ranged from 0.64 to 1.84, indicating that neither synergism nor antagonism was evident. All 12 isolates were resistant to cefovecin. The clofazimine MIC50 to inhibit isolate growth was approximately 3.3 μg/mL for both strains.

CONCLUSION

Drugs commonly used for treatment of RGM, when tested as combinations, do not appear to antagonise one another in vitro. Cefovecin is not efficacious for treatment of RGM infections.

Something old, something new: Update of the 2009 and 2013 ABCD guidelines on prevention and management of feline infectious diseases

OVERVIEW

The ABCD has published 34 guidelines in two Special Issues of the Journal of Feline Medicine and Surgery (JFMS): the first in July 2009 (Volume 11, Issue 7, pages 527-620) and the second in July 2013 (Volume 15, Issue 7, pages 528-652). The present article contains updates and new information on 18 of these (17 disease guidelines and one special article 'Prevention of infectious diseases in cat shelters'). For detailed information, readers are referred to the guidelines published in the above-mentioned JFMS Special Issues.