Susceptibility of rapidly growing mycobacteria isolated from cats and dogs, to ciprofloxacin, enrofloxacin and moxifloxacin

Review canine tuberculosis - An emerging concern

Canine mycobacterial disease was first recognised over 100 years ago but is now an emerging concern. All reported cases of tuberculous disease in dogs have been caused by infection with one of three Mycobacterium tuberculosis-complex (MTBC) organisms (M. tuberculosis, Mycobacterium bovis, and Mycobacterium microti). Molecular PCR and interferon-gamma release assays offer alternative or complementary diagnostic pathways to that of specialist culture, which is limited by availability, sensitivity, and the time it takes to get a result. Optimised triple antimicrobial protocols offer an excellent chance of a successful outcome in dogs where treatment can be considered and is attempted. In this review, the clinical presentation, diagnosis, treatment, and prognosis of canine tuberculosis are discussed.

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.

Proteomic Analysis of Differentially Expressed Proteins in Mycobacterium Tuberculosis-Infected Macrophages

Background:

Mycobacterium tuberculosis (MTB) and Mycobacterium avium (MA) are intracellular parasitic bacteria. The biological characteristics of MA and MTB are very similar and need to be identified.

Objective:

The study aims to better understand how MTB survives in macrophages and the different pathogenic mechanisms of MTB and MA.

Methods:

The Tandem Mass Tag (TMT) and liquid chromatography-tandem mass spectrometry (LCMS/ MS) were used for analysis of the differentially expressed proteins in MTB-infected macrophages and MA-infected macrophages.

Results:

A total of 682 proteins were found to be differentially expressed in MTB-infected cells in comparison with MA-infected cells. Among these, 10 proteins (O60812, P06576, O43660-2, E9PL10, O00442, M0R050, Q9H8H0, Q9BSJ8, P41240 and Q8TD57-3) were down-regulated in MTB-infected cells, and M0R050, O00442, Q9H8H0, O60812 and O43660 are interactive proteins which participate in a multitude of cellular RNA processing.

Conclusion:

The five down-regulated proteins (M0R050, O00442, Q9H8H0, O60812 and O43660) might repress the synthesis of some resistant proteins in MTB-infected cells to promote MTB survival in macrophages.

Feline mycobacterial disease in northern California: Epidemiology, clinical features, and antimicrobial susceptibility

BACKGROUND

Mycobacterial infections in cats are challenging to treat and incompletely described.

HYPOTHESIS/OBJECTIVES

To describe the features of mycobacterial infections in cats from northern California.

ANIMALS

Nineteen cats, all with nontuberculous mycobacterial (NTM) infections; 4 with Mycobacterium avium infection, 15 with rapid-growing mycobacterial (RGM) infection.

METHODS

Retrospective study. Cases with positive mycobacterial culture, species identification, and susceptibility testing were included. Descriptive statistics were used. Fisher's exact test and Mann-Whitney U test were used for comparisons between M avium and RGM infections (P ≤ .05).

RESULTS

Rapid-growing mycobacterial cases included Mycobacterium smegmatis (9), Mycobacterium fortuitum (4), Mycobacterium abscessus (1), and Mycobacterium thermoresistibile (1). Mycobacterium avium infections were more likely than RGM infections to be disseminated (3/4 vs 0/15; P = .004). Disease of the skin/subcutis (15/15 vs 0/4; P < .001) and outdoor access (14/15 vs 0/4; P = .001) were primary features of RGM infections. Resistance to fluoroquinolones and aminoglycosides was common among M avium isolates. A high prevalence of resistance to third- and fourth-generation cephalosporins was noted in RGM species. Death/euthanasia was noted only in M avium cases (3/4). Twelve of 15 cats with RGM infection had available follow-up; 4 of these cats achieved remission.

CONCLUSIONS AND CLINICAL IMPORTANCE

The most prevalent RGM species isolated from cats from northern California are M smegmatis and M fortuitum. Susceptibility to prescribed antimicrobials does not appear to guarantee treatment success. Combination drug treatment is recommended. Repeat culture and susceptibility testing should be performed when disease is persistent/relapsing.

Isolation of known and potentially pathogenic tick-borne microorganisms from European ixodid ticks using tick cell lines

Ticks harbour and, in many cases transmit to their vertebrate hosts, a wide variety of pathogenic, apathogenic and endosymbiotic microorganisms. Recent molecular analyses have greatly increased the range of bacterial species potentially associated with ticks, but in most cases cannot distinguish between surface contaminants, microorganisms present in the remains of the previous blood meal and truly intracellular or tissue-associated bacteria. Here we demonstrate how tick cell lines, primary cell cultures and organ cultures can be used to isolate and propagate bacteria from within embryonic and adult Ixodes ricinus, Dermacentor marginatus and Dermacentor reticulatus ticks originating from different parts of Europe. We isolated and partially characterised four new strains of Spiroplasma from The Netherlands, Spain and Poland, two new strains of Rickettsia raoultii from Russia and Poland, one strain of Rickettsia slovaca from Spain and a species of Mycobacterium from the UK. Comparison with published sequences showed that the Spiroplasma strains were closely related to Spiroplasma ixodetis and the Mycobacterium isolate belonged to the Mycobacterium chelonae complex, while the R. raoultii and R. slovaca strains were similar to previously-validated species.

First report of nodular skin lesions caused by Mycobacterium nebraskense in a 9-year-old cat

Case summary

A 9-year-old cat was referred with multiple, raised, ulcerative skin nodules in the region of the neck and dorsal head. Histopathological findings of a biopsied nodule were granulomatous dermatitis and panniculitis without multinucleated giant cells or caseous necrosis. In addition, by Ziehl–Neelsen staining numerous acid-fast intracellular bacilli were observed within the lesions. Mycobacterial culture showed growth of rough scotochromogenic colonies after 3 weeks of incubation. Molecular characterisation of the isolate identified Mycobacterium nebraskense as the cause of the infection. No phenotypic resistance was detected for the antimycobacterial agents tested. The cat was successfully treated with a combination of surgical excision and a 12 week course of antimicrobial therapy, including rifampicin combined with clarithromycin.

Relevance and novel information

To our knowledge, this is the first documented case of mycobacterial granulomatous dermatitis and panniculitis due to M nebraskense infection in a cat. The successful surgical and antimycobacterial treatment regimen is described.

Use of computed tomography imaging during long-term follow-up of nine feline tuberculosis cases

Case series summary Feline tuberculosis is an increasingly recognised potential zoonosis of cats. Treatment is challenging and prognosis can vary greatly between cases. Pulmonary infection requires extended courses of antibiotics, but methodologies for sensitively monitoring response to treatment are currently lacking. In this case series, we retrospectively examined the serial computed tomography (CT) findings in nine cats that had been diagnosed with tuberculosis. Changes in pathology (where applicable to tuberculosis) were correlated with the clinical presentation of each of the cats, the treatment protocol, and previous and contemporary diagnostic investigations. This study found that changes in CT findings during the medium- to long-term management of feline tuberculosis were highly variable between cats. The majority of cats had reduced pathology at re-examination during anti-tuberculous therapy, but pathology only resolved in a minority of cases. In some cases recurrence of pathology detected by CT imaging preceded clinical deterioration, allowing for rapid therapeutic intervention. Relevance and novel information When considered in combination with clinical findings, CT studies can aid in decision making regarding tapering of antibiotic protocols, or reintroduction of therapy in cases of recurrence or reinfection. This series also highlights that, in some cases, persistent abnormalities can be detected by CT, so complete resolution of CT pathology should not always be a goal in the management of feline tuberculosis.

Mycobacterioses in dogs and cats from Buenos Aires, Argentina

Mycobacterioses can produce nonspecific clinical signs in dogs and cats that make diagnosis difficult. Furthermore, the full characterization of mycobacterial agents is not always possible or practical. We characterized mycobacteria detected through cytology in 12 dogs and 7 cats with generalized clinical signs from the province of Buenos Aires in Argentina. In dogs, molecular testing confirmed the presence of Mycobacterium avium subsp. hominissuis (MAH) in 8 cases and M. fortuitum in 1 case. All dogs were Miniature Schnauzers, suggesting that this breed may be more susceptible to M. avium than other dog breeds. The cat isolates were 2 M. bovis, 1 M. fortuitum, and 1 MAH. Mycobacterial interspersed repetitive unit-variable-number tandem repeat patterns suggested possible links with cattle, swine, and humans studied previously in Argentina. The results show that pets may act as susceptible hosts with the potential risk of transmitting the infection to humans and other animals.

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.

Ulcerated and nonulcerated nontuberculous cutaneous mycobacterial granulomas in cats and dogs

BACKGROUND

Mycobacterial granulomas of the skin and subcutis can be caused by one of a number of pathogens. This review concentrates on noncultivable species that cause diseases characterized by focal granuloma(s), namely leproid granuloma (in dogs) and feline leprosy (in cats). Clinically indistinguishable lesions can be caused by tuberculous organisms (Mycobacterium bovis and Mycobacterium microti) and members of the Mycobacterium avium complex. Rapidly growing mycobacterial species that cause infection of the subcutaneous panniculus associated with draining tracts are not discussed. Disease caused by Mycobacterium ulcerans is an important emerging differential diagnosis for ulcerated cutaneous nodules in certain localized regions. CLINICAL LESIONS: Lesions comprise one or multiple nodules in the skin/subcutis. These are generally firm and well circumscribed, and typically become denuded of hair. They may or may not ulcerate, depending on the virulence of the causal organisms and the immune response of the host.

DIAGNOSIS

The most inexpensive, noninvasive means of diagnosis is by submission of methanol-fixed, Romanowsky-stained smears to a Mycobacterium Reference Laboratory after detecting negatively stained or acid-fast bacilli on cytological smears. Scrapings of material from slides usually provide sufficient mycobacterial DNA to enable identification of the causal organism using sequence analysis of amplicons after PCR using specific mycobacterial primers.

THERAPY

Therapy relies upon a combination of marginal resection of easily accessible lesions and treatment using two or three drugs effective against slowly growing mycobacteria, choosing amongst rifampicin, clarithromycin, clofazimine and pradofloxacin/moxifloxacin.