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Sporotrichoid atypical cutaneous infection caused by Mycobacterium marinum


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A case of a sporotrichoid cutaneous infection caused by Mycobacterium marinum is reported. A 53- year-old male patient presented with red, partly purulent nodular lesions on the back of his left hand, forearm, and upper medial arm that had developed consecutively during the past 4 weeks. A mycobacterial infection with M. marinum was confirmed by molecular methods in a lesional skin biopsy. The patient was treated systemically with rifampicin (750 mg/day) and clarithromycine (1,000 mg/day), and topically with sulmycin (gentamicin sulfate). After 12 weeks of treatment the nodules regressed, leaving behind erythematous patches. M. marinum is a waterborne mycobacterium that commonly infects fish and amphibians worldwide. Transmissions to humans occur occasionally, in most cases as a granulomatous infection localized to the skin, typically following minor trauma to the hands. For this reason, infections are especially common among aquarium keepers.
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Acta Dermatoven APA Vol 18, 2009, No 1
Sporotrichoid atypical cutaneous
infection caused by
F. Tigges, A. Bauer, K. Hochauf, and M. Meurer
A case of a sporotrichoid cutaneous infection caused by Mycobacterium marinum is reported. A 53-
year-old male patient presented with red, partly purulent nodular lesions on the back of his left hand,
forearm, and upper medial arm that had developed consecutively during the past 4 weeks. A mycobac-
terial infection with M. marinum was confirmed by molecular methods in a lesional skin biopsy. The
patient was treated systemically with rifampicin (750 mg/day) and clarithromycine (1000 mg/day), and
topically with sulmycin (gentamicin sulfate). After 12 weeks of treatment the nodules regressed, leaving
behind erythematous patches. M. marinum is a waterborne mycobacterium that commonly infects fish
and amphibians worldwide. Transmissions to humans occur occasionally, in most cases as a granulo-
matous infection localized to the skin, typically following minor trauma to the hands. For this reason,
infections are especially common among aquarium keepers.
C a s e r e p o r t Sporotrichoid infection caused by Mycobacterium marinum
swimming pool
Mycobacterium marinum is an ubiquitous water-
borne organism that grows optimally at temperatures
around 30 °C. It has a worldwide distribution and prima-
rily infects fish that can secondarily contaminate aquaria,
swimming pools, rivers, and seawater (1). When trans-
mitted to animals such as amphibians, fish, mice, and
bats, it can be highly prevalent in fish tanks and cause
infections and death in various fish species. A vaccine
against M. marinum infection in fish has been devel-
oped (2).
Case report
A 53-year-old patient presented at the Department
of Dermatology with reddish nodules and papulo-
pustules up to the size of a cherry on the top of the left
hand, forearm, and medial/lateral aspects of his upper
arm following lymphatic drainage in a linear fashion.
The most recent subcutaneous nodular lesions were
located in the medial upper arm (Fig. 1). No other der-
matological abnormalities were observed and other
comorbidities were excluded by laboratory tests, X-ray,
and abdominal ultrasound.
Acta Dermatoven APA Vol 18, 2009, No 1
Eight weeks before first being seen at the Depart-
ment of Dermatology, he had been treated success-
fully with Unacid PD (oral sultamicillin 375 mg) for lym-
phangitis at the left palm and left middle finger that had
developed from a cut. When asked about his hobbies,
the patient mentioned an aquarium with ornamental
fish in apparently good condition.
A biopsy taken from a nodule on the left upper arm
showed necrotizing folliculitis and perifolliculitis with
follicular rupture (Fig. 2). The nodular biopsy was sub-
jected to microscopic, culture, and molecular analysis.
Acid fast rods could not be observed by microscopic
examination. The mycobacterial culture did not show
any growth after an incubation time of about 10 weeks.
Molecular diagnostics comprised a genus-specific PCR
targeting the mycobacterial 16sRNA gene followed by
automated DNA-sequencing (ABI Prism 310 Sequencer,
Applied Biosystems). Results of the nucleotide BLAST
search showed a 100% homology to Mycobacterium
marinum/ulcerans (3–5).
Standard microbiological techniques including cul-
ture and common mycobacterial PCRs revealed no other
pathogens from among the huge number of other my-
cobacterial species.
In view of the clinical pattern and the clinical find-
ings, an atypical mycobacteriosis of the skin following a
sporotrichoid pattern caused by M. marinum was di-
agnosed. The patient was started on long-term antibi-
otic therapy with rifampicin 750 mg/day and clari-
thromycine 1000 mg/day (500 mg twice daily) for 12
months and synchronous topical application of sulmycin.
At the follow-up examinations after 4, 8, 12, and 22
weeks, a pronounced regression of the lesions was ob-
served (Figure 3).
M. marinum can cause superficial infections and
localized invasive infections in humans, with the hands
being the sites most frequently affected. It can be ob-
served in humans that are exposed to fish or fish tanks
through their hobbies or occupations (6).
After exposure, symptoms usually appear within 2
to 4 weeks (7). However, there are some cases report-
ing an incubation time of 2 to 4 months and longer, with
some cases reporting an incubation period as long as 9
months (8) due to the slow-growing nature of this bac-
In general, M. marinum infection in humans is com-
paratively rare; the approximate annual incidence in
the US is 0.27 confirmed cases per 100,000 inhabitants.
The temperature of human skin is advantageous for
the establishment of superficial infection, which is com-
monly preceded by minor traumatic lesions. Following
abrasions or superficial wounds, humans infected by
contaminated water develop purulent superficial or
deep granulomatous skin infections (2). Single lesions
consist of papulo-nodular, verrucous, or ulcerated granu-
lomatous inflammation with minimal purulent secre-
tions. Sporotrichoid lesions following the lymph drain-
age spread from the primary lesion, leading to linearly
arranged, inflamed, pustular lesions resembling deep
fungal infection with Sporothrix schenckii (Fig. 1 and
Mycobacterial culture from smears and tissue biop-
sies is the most important diagnostic tool for detection
of M. marinum. A positive culture significantly sup-
ports M. marinum as the causative agent for a nodular
skin lesion and makes other infectious or neoplastic
conditions less likely. In the case presented here, the
mycobacterial culture specimen was cultivated at 30
°C in the liquid culture and at 37 °C in the fixed culture.
The culture was incubated at 30 °C, but remained
sterile. The more sensitive sequence of PCR-product
detected M. marinum and M. ulcerans. Possible rea-
sons for this could be an irregular distribution in the
material or perhaps the bacteria had already been dam-
aged, so cultivation was impossible. Nevertheless, in
the past decade molecular techniques have become
highly relevant for mycobacteria detection and identifi-
cation. The 16sRNA PCR protocol used here did not
allow discrimination between M. marinum and M.
ulcerans (9). Therefore, in this particular case, the pa-
tient could only be diagnosed with a M. marinum in-
fection by evaluating anamnestic data, the clinical and
dermatological presentation, the PCR/sequencing re-
sults, and the histomorphological analysis of skin biop-
The standard treatment generally includes various
antibiotics as outlined below, with the treatment dura-
tion varying from as little as 2 weeks in some reports to
as long as 18 months, depending on the extent and
severity of the infection, the presence of underlying
disorders, and the clinical response. For superficial in-
fections, antibiotic therapy is usually given for between
6 weeks and 6 months, whereas deep infections are
treated for as long as 6 to 18 months (10). Deeper in-
fections may require adjunctive surgical debridement,
in particular when there is evidence of therapy-resis-
tant infection (11). Some reports demonstrate the suc-
cessful use of excision, curettage, and cryotherapy (12).
It is even stated that photodynamic therapy may be
useful in the treatment of M. marinum infections,
though more data are needed (13).
Antimicrobial therapy includes antibiotics such as
cotrimoxazole, minocycline, doxycycline, trimetho-
prim/sulfamethoxazole, quinolones, ethambutol,
rifampicin, and clarithromycine (6, 8, 11, 14, 15). At this
point, a combination of ethambutol and rifampicin has
been extensively used and is regarded as standard regi-
men, particularly for deep infections (10), but the po-
tential for ocular toxicity has made this regimen unat-
Sporotrichoid infection caused by Mycobacterium marinum C a s e r e p o r t
Acta Dermatoven APA Vol 18, 2009, No 1
tractive for treating less serious superficial infections.
With no controlled clinical trials existing for the treat-
ment of M. marinum infections because of the small
number of affected patients, treatment success was seen
with minocycline, particularly well-documented in the
dermatology literature, even in cases complicated by
delayed diagnosis and systemic immunosuppression
(16). Reports suggest that minocycline may be the most
effective treatment option, despite the underlying simi-
larity in the mechanism and sensitivities of different
second-generation tetracyclines (6).
More recently, newer macrolide antibiotics such as
clarithromycine have been shown to represent a treat-
ment option for cutaneous M. marinum infection, es-
pecially if used in combination with rifabutin and
ciprofloxacin (17). Although clinical experience is so
far limited, clarithromycine is stated to have been used
successfully alone and in combination with ethambutol
and ciprofloxacin, thus being a promising therapy (10).
Finally, in some recent reports the opinion is mentioned
that clarithromycine is the optimal first agent in combi-
nation treatment of M. marinum (18, 19), assuming
that ethambutol and rifampicin represent reasonable
second line agents (11).
The type and duration of antimicrobial therapy var-
ies considerably in the literature, with no single agent or
combination of agents clearly shown to be the treat-
ment of choice. The clinical response and the results of
in vitro sensitivity tests should be used to guide any
subsequent modification of the antibiotic regimen; there-
fore, a combined therapy is advised, particularly in deep
infections like that of our patient (20).
Infections due to M. marinum are uncommon, but
not rare. An association of the infection with domestic
tropical fish tanks or other aquatic exposures is known.
The diagnosis requires both a detailed history as well as
sophisticated microbiological and PCR-based investiga-
tions. No large systemic studies have been performed
to determine the optimal treatment regimen. In most
cases a combination of antibacterial drugs such as
clarithromycine and rifampicin should be given as well
as long-term therapy depending on the duration and
severity of infection.
Fish-tank exposure is the source of most cases of
cutaneous M. marinum infections and may be pre-
vented by the use of waterproof gloves by persons
with acute or chronic open skin lesions.
C a s e r e p o r t Sporotrichoid infection caused by Mycobacterium marinum
Fig. 1. Subcutaneous nodular lesions located in
the medial upper arm.
Fig. 3. Pronounced regression of the lesions at
the follow-up.
Fig. 2. Necrotizing folliculitis and perifolliculitis
with follicular rupture. (HE)
Acta Dermatoven APA Vol 18, 2009, No 1
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Frauke Tigges, MD, Department of Dermatology, Medical University
of Dresden, Germany, corresponding author,
Andrea Bauer, MD, MPH, Department of Dermatology, same address
Kristina Hochauf, MD, Department of Microbiology, same address
Michael Meurer, MD, Professor, Head of the Department, Department
of Dermatology, same address
Sporotrichoid infection caused by Mycobacterium marinum C a s e r e p o r t
... Reduction of human tuberculosis is one of the targets of the Millennium Development Goal (Arend et al. 2001;Brutus et al. 2001;Nakamura et al. 2001;Villella et al. 2001;Lidar et al. 2003 (Anonymous 1997;De Smet 2008;Tigges et al. 2009). ...
... An inherent problem (Roth, Reischl, Streubel, Naumann, Kroppenstedt, Habicht, Fischer & Mauch 2000;Pakarinen et al. 2007) in the development of genus-wide mycobacterial assays is that of cross-reaction with closely related bacterial species. On testing of DNA extracted from a broad taxonomic panel of non-mycobacterial species, - 2011,34,[235][236][237][238][239][240][241][242][243][244][245][246] positive signals were experienced with only two bacteria closely related to mycobacteria. Analysis of DNA extracted from Nocardia asteriodes and R. erythropolis cultures resulted in Ct values of 21.95 and 26.75, respectively. ...
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Mycobacterial infections in fish are invariably referred to as piscine tuberculosis or mycobacteriosis, irrespective of the specific identity of the causal Mycobacterium sp. The disease is largely sub-acute to chronic in nature and affects fish in fresh-, brackish- and sea- water. The disease may cause both external and internal lesions, which can easily be confused with other diseases unless mycobacteria-specific diagnostic tools are employed to detect the pathogen. Sensitive and truly genus-wide real-time polymerase chain reaction (real-time PCR) and immunohistochemical diagnostic tools, which are applicable both in disease diagnosis and research, were established (Paper I). Mycobacterium salmoniphilum was found to be an important fish pathogen of both gadoid and salmonid fishes. The clinical and pathological features of mycobacteriosis caused by M. salmoniphilum were characterized in farmed Atlantic salmon (Paper II), burbot (Paper III) and Atlantic cod (Paper IV). The mycobacterial infection described in burbot (Paper III) is the first of its kind. The infection study in Atlantic cod has shown that mycobacteriosis is a prospectively important future disease in farming of this fish species. Pathological lesions characterized by severe granuloma formation were identified in cod and burbot infections, while this type of lesion was identified as either mild or even absent in Atlantic salmon. Granulomatous lesions attributed to mycobacterial infection in Atlantic cod showed a series of developmental stages, the identification and characterisation of which comprise important knowledge in relation to assessment of disease progression and estimation of time of infection. Prior to the present study, very few studies have been performed relating to piscine mycobacteriosis in aquaculture in Norway. Reports of piscine mycobacteriosis were at best sporadic and were mainly from ornamental and wild fish. These diagnoses were limited to Ziehl-Neelsen (ZN) staining of tissue sections and basic phenotypical testing of bacterial isolates on the rare occasions that the responsible bacterium was cultured. The prevalence of the disease and associated losses in Atlantic salmon and a cold-water gadoid fish species i.e. burbot and Atlantic cod identified in the present study, may indicate a wider distribution of the disease both in terms of host range and climate range than previously considered. Although an epidemiological study on a larger scale is required to more accurately describe the prevalence, particularly in farmed fish, the previously insignificant numbers of reports from Norway may be due in part, to low awareness of the clinical features of piscine mycobacteriosis in different fish species. Current diagnostic practices for mycobacteriosis depend to a greater or lesser reliance on the presence of granulomatous lesions. In salmonids, therefore, the infrequency or absence of „typical‟ mycobacterial related pathological changes combined with the less sensitive diagnostic tools currently available in most fish disease investigation laboratories and the dominance of other differential diagnostically important diseases, there is a risk that mycobacterial related disease may be overlooked. The present study has broadened the knowledge base related to mycobacterial infections of fish, particularly in cold water environments. The results should, therefore, draw the attention of fish pathologists and other fish health professionals to the possibilities of mycobacterial infections in fish; thereby increasing the likelihood of further diagnosis of the disease and implementation of loss minimization strategies.
... Multidrug therapy is recommended for more extensive infections with the involvement of deeper structures or for severe infections with a sporotrichoid distribution pattern (clarithromycin associated with rifampicin or ethambutol) [1,6]. The treatment is prolonged, taking between 6 weeks and 6 months (at least 2 months after the clinical remission [6] and in deep infections taking 18 months [4,8]). Surgical treatment is usually reserved for cases of subcutaneous tissue (tendons or bone) involvement [1]. ...
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Introduction.Mycobacterium marinum is a non-tubercular mycobacterium residing in fresh or salt water (in tropical or temperate areas); it is a fish and human pathogen, and in immunocompromised patients can cause severe cutaneous and subcutaneous infections. Case presentation. A 46-year-old white man who underwent immunosuppressive therapy was admitted to our department in May 2016 for skin lesions previously diagnosed as ‘unusual erysipelas’. We rejected the hypothesis of erysipelas, due to the clinical features, and our diagnostic hypotheses were oriented towards sporotrichosis, atypical mycobacteriosis, cutaneous tuberculosis and cutaneous sarcoidosis. Histological examination performed after a skin biopsy was compatible with a diagnosis of sporotrichosis. However, PCR performed on fresh tissue demonstrated the presence of M. marinum. Conclusion. The case reported is interesting for the unusual clinical localization and modality of infection. The patient became infected by contact with contaminated remains or in the sea, in a geographical area not endemic for M. marinum. The previous state of immunosuppression favoured infection; however, the presence of M. marinum in this area suggests a possible tropicalization of the water of the Mediterranean Sea. To our knowledge, this case is the only one reported in the literature with this modality of infection and in that geographical area.
... The predilection for the extremities is due to inhibition of growth of M. marinum at 37 ℃ so the organisms tends to infect the cooler parts of the body including the extremities [57] . The granuloma usually presents as a solitary, erythematous papule or nodule and may be mistaken for sporotrichosis or leishmaniasis [58,59] . Disseminated infection is rare, although a case of disseminated Mycobacterium that presented as erythema nodosum was previously described in a 12-year-old girl [60] . ...
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Numerous manuscripts have described dermatologic conditions commonly seen in swimmers. This review provides an update on water dermatoses and discusses newly described conditions such as allergic contact dermatitis to chemical ingredients like potassium peroxymonosulate in pool water. In order to organize water related skin conditions, we have divided the skin conditions into a number of categories. The categories described include infectious and organism-related dermatoses, irritant and allergic dermatoses, and sun-induced dermatoses. The vast majority of skin conditions involving the water athlete result from chemicals and bacteria in the differing aquatic environments. When considering the effects of swimming on the skin, it is also useful to differentiate between exposure to freshwater (lakes, ponds and swimming pools) and exposure to saltwater. The risk of melanoma amongst swimmers is increased, and the use of SPF 30 or greater sunscreen and protective clothing is highly recommended. Swimmers should be reminded to generously apply sunscreen and be instructed on proper sunscreen usage. This review will serve as a guide for dermatologists, athletes, coaches, and other medical professionals in recognition and treatment of these conditions. We also intend for this review to provide dermatologist with a basic framework for the diagnosis and treatment of a few rarely described dermatological conditions in swimmers.
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Tigecycline and imipenem are important antimicrobial agents for the treatment of serious infections, therefore correct MIC (minimum inhi - bitory concentration) determination is important. Imipenem is one of the therapeutic options against extended spectrum ß lactamase (ESBL) producing Gram negative bacilli (GNB) and tigecycline, one of the remaining options against extensively drug resistant (XDR) GNB. While tigecycline Etest strips from bioMerieux and Liofilchem have been compared with each other [6], there are neither studies that investigated the effect of aerobic or anaerobic cultivation on the MICs, nor studies that compared the imipenem commercially available Etest strips from bioMerieux and Liofilchem.
Growing ornamental fish industry is associated with public health concerns including extensive antibiotic use accompanied by increasing antibiotic resistance. The aim of this study was to analyze Aeromonas isolates from imported tropical ornamental fish and coldwater koi carps bred in the Czech Republic to assess the potential risk of ornamental fish as a source of plasmid-mediated quinolone resistance genes (PMQR) and antibiotic resistance plasmids. A collection of Aeromonas spp. with reduced susceptibility to ciprofloxacin (MIC≥0.05mg/L) was selected for the detection of PMQR genes. Isolates harbouring PMQR genes were further analyzed for the additional antibiotic resistance, integron content, clonality, biofilm production and transferability of PMQR genes by conjugation and transformation. Comparative analysis of plasmids carrying PMQR genes was performed. Fifteen (19%, n=80) isolates from koi carps and 18 (24%, n=76) isolates from imported ornamental fish were positive for qnrS2, aac(6')-Ib-cr or qnrB17 genes. PMQR-positive isolates from imported ornamental fish showed higher MIC levels to quinolones, multiresistance and diverse content of antibiotic resistance genes and integrons compared to the isolates from the carps. Related IncU plasmids harbouring qnrS2 and aac(6')-Ib-cr genes were found in Aeromonas spp. from imported ornamental fish and koi carps from various geographical areas. Ornamental fish may represent a potential source of multiresistant bacteria and mobile genetic elements for the environment and for humans.
Atypical mycobacteria comprise an uncommon heterogenous non-tuberculous group of acid-fast bacteria that rarely involve skin. The pattern of atypical mycobacterial cutaneous infections (AMCI) has not been previously studied in Egypt. The aim of this study was to describe the clinical characteristics, pathological features and species profile of AMCI among Egyptian patients. A retrospective study included 46 cases, diagnosed with AMCI during the period 2002 to 2012. The study included 34 males (73.9%) and 12 females (26.9%). The average age of patients was 39 years while the average duration of lesions was 15 months. The lesions were mostly located on the extremities (91.3%) and there was predominance of single (65.2%) and nodular (41.4%) lesions. History of trauma was confirmed in 91.3%. Histologically, the granulomas were mostly superficial (67.4%) with predominance of nodular suppurative pattern (84.8%). Other significant histological findings included epidermal hypertrophy (100%), presence of large-sized multinucleated giant cells (87%) and intrafollicular neutrophilic abscesses (84.8%). The diagnosis was proved by direct smear in 6.5%, skin biopsy in 10.9%, tissue culture in 47.8% and polymerase chain reaction (PCR) in 34.8%. Isolated species included Mycobacterium marinum (84.8%), Mycobacterium fortuitum (10.9%) and Mycobacterium kansasii (4.3%). Although the results of this study recommend that the diagnosis of AMCI is based mainly on culture and PCR, other clinicopathological features such as history of trauma, acral location of the lesion and suppurative granulomatous reaction with intrafollicular abscesses could be helpful clues in suspecting AMCI.
We sought to synthesize important information from recent literature on mycobacterial infections of the hand and wrist. A PubMed search for recent literature (published between 2008 and the present) concerning mycobacterial infections of the hand and wrist was done. The recent literature on mycobacterial infections of the hand and wrist consists entirely of case series and case reports. Although there is some agreement among authors, no consensus exists regarding optimal diagnosis or treatment of these infections. Mycobacterial infections of the hand and wrist are rare, and diagnosis is typically delayed as more common processes are assumed. Certain types of vocational exposure and immunocompromise may be risk factors. Mycobacterial infection may present in a similar fashion to that of more typical organisms and may produce otherwise aseptic pathology including tenosynovitis, trigger-finger, and carpal tunnel syndrome. Treatment with long pharmaceutical courses is common. Surgery is reserved for refractory cases.
Identification of the pathogenic microbe is essential for selection of the most appropriate treatment in the majority of cutaneous infections. Historically, the diagnosis of cutaneous pathogens has been based on the results of immunological studies, lesional culture, and/or microscopic examination of tissue samples, in combination with histochemical stains (i.e., PAS, Gram) or immunohistochemical studies. Microscopic review of clinical specimens allows for rapid microbe detection. However, this method lacks sensitivity and specificity, and typically results in a preliminary determination only. In addition, not every pathogen is identifiable by microscopic analysis, and special stains are often less sensitive than culture methods. Thus, definitive characterization requires growth of the pathogen in culture, which remains the gold-standard methodology for laboratory diagnosis of microbial infection. While the latter generally demonstrates improved sensitivity and specificity as compared with histopathological examination, microbe growth may require days to weeks of culture, delaying both diagnosis and the institution of appropriate therapy. Further complicating matters is the fact that not all pathogens grow outside of their host.
Mycobacterium marinum belongs to the non-tuberculous or "atypical" mycobacteria. The reservoirs for these ubiquitous and slowly growing bacteria are both fresh water and salt water. In particular, aquaria should be considered as important source of hobby-related infections especially of fingers, hands and forearms. Affected are both immunosuppressed patients and persons with an intact immune system. Distinctive are erythematous plaques and nodules with tendency for hyperkeratosis, crusting, and superficial ulcerations, sometimes as sporotrichoid lymphocutaneous infection. The histology shows non-caseation granulomas containing epithelioid cells and Langhans giant cells. Using the Ziehl Neelsen staining, typical acid-fast rods are not always detectable. The molecular biological detection of mycobacterial DNA using polymerase chain reaction represents the standard method of diagnosis. Cryotherapy is frequently used as first treatment. For the often long-term tuberculostatic therapy, rifampicin, ethambutol, and clarithromycin are the most used agents.
Mycobacteriosis in fish is a chronic progressive ubiquitous disease caused by Mycobacterium marinum, M. gordonae and M. fortuitum in most cases. The aim of this study was to describe the morphology and distribution of lesions in 322 freshwater ornamental fish across 36 species. Granulomatous inflammation was diagnosed by gross examination and histopathology testing in 188 fish (58.4%); acid-fast rods (AFR) were determined in only 96 (51.1%) fish from 19 species after Ziehl-Neelsen staining. The most often affected organs with AFR were the kidney (81.2%), digestive tract (54.1%), liver (48.2%), spleen (45.9%) and skin (21.2%); sporadically, AFR were found in the branchiae (9.4%) and gonads (4.7%). In 14 randomly selected fish originating from four different fish tanks, the distribution of mycobacterial infection was studied by culture examination of the skin, gills, muscle tissue, digestive tract, liver, spleen and kidney. In 12 fish, the species M. marinum, M. gordonae, M. fortuitum, M. triviale, and M. avium subsp. hominissuis (serotypes 6 and 8 and genotype IS901- and IS1245+) were detected; mixed infection caused by different mycobacterial species was documented in five of them.
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The BLAST programs are widely used tools for searching protein and DNA databases for sequence similarities. For protein comparisons, a variety of definitional, algorithmic, and statistical refinements permits the execution time of the BLAST programs to be decreased substantially while enhancing their sensitivity to weak similarities. A new criterion for triggering the extension of word hits, combined with a new heuristic for generating gapped alignments, yields a gapped BLAST program that runs at approximately three times the speed of the original. In addition, a method is described for automatically combining statistically significant alignments produced by BLAST into a position-specific score matrix, and searching the database using this matrix. The resulting Position Specific Iterated BLAST (PSLBLAST) program runs at approximately the same speed per iteration as gapped BLAST, but in many cases is much more sensitive to weak but biologically relevant sequence similarities.
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Oligonucleotides specific at a genus, group, or species level were defined by a systematic comparison of small-subunit rRNA sequences from Mycobacterium tuberculosis, M. bovis, M. africanum, M. bovis BCG, M. avium, M. kansasii, M. marinum, M. gastri, M. chelonae, M. smegmatis, M. terrae, M. nonchromogenicum, M. xenopi, M. malmoense, M. szulgai, M. scrofulaceum, M. fortuitum, M. gordonae, M. intracellulare, M. simiae, M. flavescens, M. paratuberculosis, M. sphagni, M. cookii, M. komossense, M. phlei, and M. farcinica. On the basis of the defined oligonucleotides, the polymerase chain reaction technique was explored to develop a sensitive taxon-specific detection system for mycobacteria. By using M. tuberculosis as a model system, fewer than 10 bacteria could be reliably detected by this kind of assay. These results suggest that amplification of rRNA sequences by the polymerase chain reaction may provide a highly sensitive and specific tool for the direct detection of microorganisms without the need for prior cultivation.
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Previous studies have indicated that the conventional tests used for the identification of mycobacteria may (i) frequently result in erroneous identification and (ii) underestimate the diversity within the genus Mycobacterium. To address this issue in a more systematic fashion, a study comparing phenotypic and molecular methods for the identification of mycobacteria was initiated. Focus was given to isolates which were difficult to identify to species level and which yielded inconclusive results by conventional tests performed under day-to-day routine laboratory conditions. Traditional methods included growth rate, colonial morphology, pigmentation, biochemical profiles, and gas-liquid chromatography of short-chain fatty acids. Molecular identification was done by PCR-mediated partial sequence analysis of the gene encoding the 16S rRNA. A total of 34 isolates was included in this study; 13 of the isolates corresponded to established species, and 21 isolates corresponded to previously uncharacterized taxa. For five isolates, phenotypic and molecular analyses gave identical results. For five isolates, minor discrepancies were present; four isolates remained unidentified after biochemical testing. For 20 isolates, major discrepancies between traditional and molecular typing methods were observed. Retrospective analysis of the data revealed that the discrepant results were without exception due to erroneous biochemical test results or interpretations. In particular, phenotypic identification schemes were compromised with regard to the recognition of previously undescribed taxa. We conclude that molecular typing by 16S rRNA sequence determination is not only more rapid (12 to 36 h versus 4 to 8 weeks) but also more accurate than traditional typing.
Mycobacterium marinum is a saprophytic atypical mycobacteria capable of causing soft tissue infections in humans, generally acquired via inoculation. M. marinum resides in aquatic environments both fresh and salt water and has a worldwide distribution. The commonest source of infection presently, however, is from a home aquarium and the disease is known as "Fish Tank Granuloma". The typical clinical features are of a nodule, which may be warty or ulcerated, predominantly on the upper limbs. Sporotrichoid spread where further nodules develop adjacent to the initial infection via lymphatic spread is characteristic. M. marinum, similarly to other atypical mycobacteria, is resistant to standard anti-tuberculous therapy. Various treatment regimens have been reported to be effective including rifampicin, co-trimoxazole and tetracyclines.
This paper has presented a compilation of facts gained from the study of 290 cases of skin infections produced by Mycobacterium balnei. All of these infections apparently stemmed from a common source. We are unable to trace the introduction of the infectious organism into the particular swimming pool in question. We have related the clinical, bacteriological, and public health aspects of this epidemic as recorded by private physicians, a private bacteriologic laboratory of a philanthropic institution, and a state public health department.
Cutaneous infections by nontuberculous mycobacteria (NTM) are not usual but their relative importance has changed during the last few years and still further changes are expected. This study comprised 13 patients from whom NTM were recovered from skin biopsy specimens, sinus exudates or cutaneous abscesses. All samples were processed according to standard methods, and the isolates were identified by biochemical testing. Skin biopsy specimens, when available, were processed for histopathological study. The clinical records of the patients were reviewed, and the relevant clinical, microbiological and epidemiological data collected. The clinical manifestations were noted to be relatively nonspecific and consisted of draining sinuses, abscesses, ulcers and nodules with multicentric or sporotrichoid patterns. Tissue culture isolated Mycobacterium fortuitum complex in nine patients, M. avium in three, and M. marinum in one. In the nine patients studied by histopathology, various patterns were observed. These included dermo-hypodermal abscesses, suppurative granulomas, tuberculoid granulomas and granulomas with a perifollicular distribution. Cutaneous lesions can thus be the first and the only sign of NTM disease, and culture still remains the definitive diagnostic procedure.
Atypical mycobacterial infections of the skin present a diagnostic and therapeutic challenge to dermatologists in many instances. We report on a patient who was diagnosed with atypical mycobacteriosis in its rarer, sporotrichoid form. Possible differential diagnoses are discussed. Efficient therapy using minocycline is demonstrated.