Comparison of real-time PCR with fungal culture for the diagnosis of Microsporum canis dermatophytosis in shelter cats: a field study

2017 ◽  
Vol 20 (2) ◽  
pp. 103-107 ◽  
Author(s):  
Linda S Jacobson ◽  
Lauren McIntyre ◽  
Jenny Mykusz
Keyword(s):  
Real Time ◽  
Sensitivity And Specificity ◽  
False Positive ◽  
False Negative ◽  
Microsporum Canis ◽  
Fungal Culture ◽  
Mycological Cure ◽  
Hair Samples ◽  
Culture Positive ◽  
Culture Negative

Objectives Fungal culture requires at least 14 days for a final result, compared with 1–3 days for PCR. The study compared a commercial real-time dermatophyte PCR panel with fungal culture in cats in a shelter setting for: (1) diagnosis of Microsporum canis infection; and (2) determination of mycological cure. Methods This was a cross-sectional, observational study of cats with suspicious skin lesions or suspected exposure to dermatophytosis. Hair samples were collected for fungal culture and PCR prior to treatment and at weekly intervals until two negative culture results were obtained. Results One hundred and thirty-two cats were included, of which 28 (21.2%) were culture positive and 104 (78.8%) culture-negative for M canis. PCR correctly identified all culture-positive cats and 92/104 culture negative cats; there were 12 false-positive PCR results. The sensitivity and specificity of PCR were 100% (95% confidence interval [CI] 87.7–100) and 88.5% (95% CI 80.7–93.9), respectively. Data from 17 cats were available for assessment of mycological cure. At the time of the first and second negative fungal cultures, 14/17 (82.4%) and 11/17 (64.7%) tested PCR positive, respectively. Conclusions and relevance PCR showed high sensitivity and specificity for diagnosis of M canis dermatophytosis compared with fungal culture, but was unreliable for identifying mycological cure. False-positive results were relatively common. There were no false-negative PCR results and a negative PCR test was a reliable finding in this study. The ability to rapidly diagnose or rule out dermatophytosis could be a valuable tool to increase life-saving capacity in animal shelters.

Assessment of real-time PCR cycle threshold values in Microsporum canis culture-positive and culture-negative cats in an animal shelter: a field study

2017 ◽  
Vol 20 (2) ◽  
pp. 108-113 ◽  
Author(s):  
Linda S Jacobson ◽  
Lauren McIntyre ◽  
Jenny Mykusz
Keyword(s):  
Field Study ◽  
Real Time ◽  
Real Time Pcr ◽  
Fungal Culture ◽  
Time Points ◽  
Cycle Threshold ◽  
Ct Value ◽  
Two Samples ◽  
Culture Positive ◽  
Culture Negative

Objectives Real-time PCR provides quantitative information, recorded as the cycle threshold (Ct) value, about the number of organisms detected in a diagnostic sample. The Ct value correlates with the number of copies of the target organism in an inversely proportional and exponential relationship. The aim of the study was to determine whether Ct values could be used to distinguish between culture-positive and culture-negative samples. Methods This was a retrospective analysis of Ct values from dermatophyte PCR results in cats with suspicious skin lesions or suspected exposure to dermatophytosis. Results One hundred and thirty-two samples were included. Using culture as the gold standard, 28 were true positives, 12 were false positives and 92 were true negatives. The area under the curve for the pretreatment time point was 96.8% (95% confidence interval [CI] 94.2–99.5) compared with 74.3% (95% CI 52.6–96.0) for pooled data during treatment. Before treatment, a Ct cut-off of <35.7 (approximate DNA count 300) provided a sensitivity of 92.3% and specificity of 95.2%. There was no reliable cut-off Ct value between culture-positive and culture-negative samples during treatment. Ct values prior to treatment differed significantly between the true-positive and false-positive groups ( P = 0.0056). There was a significant difference between the pretreatment and first and second negative culture time points ( P = 0.0002 and P <0.0001, respectively). However, there was substantial overlap between Ct values for true positives and true negatives, and for pre- and intra-treatment time points. Conclusions and relevance Ct values had limited usefulness for distinguishing between culture-positive and culture-negative cases when field study samples were analyzed. In addition, Ct values were less reliable than fungal culture for determining mycological cure.

One vs two negative fungal cultures to confirm mycological cure in shelter cats treated for Microsporum canis dermatophytosis: a retrospective study

2019 ◽  
Vol 22 (6) ◽  
pp. 598-601
Author(s):  
Rebecca L Stuntebeck ◽  
Karen A Moriello
Keyword(s):  
Retrospective Study ◽  
Sampling Error ◽  
False Negative ◽  
Sampling Technique ◽  
Response To Treatment ◽  
Clinical Group ◽  
Microsporum Canis ◽  
Fungal Culture ◽  
Mycological Cure ◽  
Environmental Cleaning

Objectives The aim of this study was to determine how often one negative fungal culture (FC) was indicative of mycological cure (MC) when compared with two negative consecutive FCs in cats treated for Microsporum canis dermatophytosis. Methods In this retrospective study, weekly FC data from shelter cats treated for M canis dermatophytosis were reviewed. Results Complete records from 371 cats were reviewed. The first negative FC was indicative of MC in 335 (90.3%) cats. In this group, all cats were otherwise healthy and either had obvious lesions (n = 237) or no lesions or evidence of resolving lesions (n = 98). In the 36 cats in which the first negative culture was not indicative of MC, there were two clinical subgroups. The first consisted of healthy but lesional cats (n = 19) that had one negative FC within the first 3 weeks of treatment followed by one or more positive FCs. The most likely explanation was sampling error. These cats went on to cure and the next negative FC was indicative of MC. In the second clinical group, cats were lesional but had concurrent medical problems (n = 17). These cats showed an initial good response to treatment (lesion resolution and an initial negative FC). However, this negative FC was followed by at least one strongly positive FC (>10 colony-forming units/plate) before proceeding to cure. These cats took the longest time to cure (mean 11 weeks; range 8–28 weeks). MC occurred after resolution of the concurrent health issues. There was very good agreement between using one negative FC vs two negative FCs for the determination of MC in healthy cats (kappa = 0.903) Conclusions and relevance In cats where there has been high compliance with environmental cleaning, as well as topical and systemic treatment recommendations, two consecutive negative FCs may not be necessary to determine MC. The first negative FC in an otherwise healthy cat is likely indicative of MC. Good sampling technique is needed to avoid false-negative FC results.

Pearls and Pitfalls of Interpretation in CT Colonography

2020 ◽  
Vol 71 (2) ◽  
pp. 140-148
Author(s):  
Michael Schonberger ◽  
Philippe Lefere ◽  
Abraham H. Dachman
Keyword(s):  
Computed Tomography ◽  
Sensitivity And Specificity ◽  
False Positive ◽  
Ct Colonography ◽  
False Negative ◽  
High Sensitivity ◽  
Negative Results ◽  
False Negative Results ◽  
The Common

The accuracy of computed tomography (CT) colonography (CTC) requires that the radiologist be well trained in the recognition of pitfalls of interpretation. In order to achieve a high sensitivity and specificity, the interpreting radiologist must be well versed in the causes of both false-positive and false-negative results. In this article, we review the common and uncommon pitfalls of interpretation in CTC.

scholarly journals False positive antigen test for Dirofilaria immitis after heat treatment of the blood sample in a microfilaremic dog infected with Acanthocheilonema dracunculoides

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Viktor Szatmári ◽  
Martin Willem van Leeuwen ◽  
Christine Jantine Piek ◽  
Luigi Venco
Keyword(s):  
Heat Treatment ◽  
Blood Sample ◽  
Real Time ◽  
Real Time Pcr ◽  
False Positive ◽  
Dirofilaria Immitis ◽  
False Negative ◽  
Correct Identification ◽  
Test Results ◽  
Antigen Test

Abstract Background Dirofilaria immitis is responsible for heartworm disease in dogs in endemic areas worldwide. Screening for this infection is done by blood tests. Antigen testing is the most sensitive method to detect an infection with adult (female) worms. Microscopic examination of a blood smear or Knott’s test can be used to detect circulating microfilariae, the infective larvae. To increase the sensitivity of the antigen test by decreasing the false negative test results, heating of the blood sample has been recommended in recent guidelines. Heating is believed to remove blocking immune-complexes. Circulating microfilariae are not specific findings for heartworm infection, as other nematodes (among others, Acanthocheilonema dracunculoides) can also result in microfilaremia. Although the type of microfilariae cannot be determined by microscopy alone, real-time PCR can reliably identify the infecting nematode species. Correct identification of the parasite is of major importance, as an infection with D. immitis requires antiparasitic therapy, whereas A. dracunculoides is thought to be a clinically irrelevant coincidental finding. The present case report describes a microfilaremic dog where the initial antigen test for D. immitis turned positive after heat treatment, whereas real-time PCR revealed that the microfilariae were A. dracunculoides (syn. Dipetalonema dracunculoides). Results A circa 5-year old, asymptomatic Spanish mastiff dog was referred for heartworm therapy because microfilariae were found via a screening blood test. The dog was recently imported to the Netherlands from Spain, where it had been a stray dog. Antigen tests on a plasma sample for D. immitis were performed with three different test kits, which all turned out to be negative. However, heat treatment of two of these samples were carried out and both of them led to a positive antigen test result. Real-time PCR showed that the circulating microfilariae belonged to A. dracunculoides species. Three administrations of moxidectin spot-on at monthly intervals resulted in a negative antigen and a negative Knott’s tests one month after the last treatment. Conclusions We conclude that heat treatment of initially negative blood samples for D. immitis could lead to false positive antigen test results if the dog is infected with A. dracunculoides.

Parotid Tumors: Fine-Needle Aspiration and/or Frozen Section

2008 ◽  
Vol 139 (2_suppl) ◽  
pp. P42-P43
Author(s):  
Peter Zbaren ◽  
Heinz Loosli ◽  
Edouard Stauffer
Keyword(s):  
Sensitivity And Specificity ◽  
Fine Needle Aspiration ◽  
False Positive ◽  
Frozen Section ◽  
False Negative ◽  
Needle Aspiration ◽  
True Positive ◽  
True Negative ◽  
Fine Needle ◽  
Parotid Neoplasms

Objective Assess the difficulties of preoperative and intraoperative tumor typing of parotid neoplasms. Know the advantages and pitfalls of fine-needle-aspiration cytology (FNAC) and frozen section (FS) analysis in primary parotid neoplasms. Methods In 113 parotid neoplasms (70 malignancies and 43 benign tumors) preoperative FNAC as well as intraoperative FS analysis were performed. FNAC and FS findings were analyzed and compared with the final histopathologic diagnosis. Results The FNAC smear was non-diagnostic in 6 tumors. In 2 FS specimens, it was not possible to determine the tumor dignity. FNAC findings and FS findings were both available in 105 neoplasMS The FNAC findings were true positive for malignancy in 54, true negative in 36, false positive in 4, and false negative in 11 tumors. The accuracy, sensitivity, and specificity were 86%, 83%, and 90% respectively. The FS findings were true positive in 60, true negative in 38, false positive in 2, and false negative in 5 tumors. The accuracy, sensitivity, and specificity were 93%, 92% and 95% respectively. The exact histologic tumor typing by FNAC was correct, false or not mentioned in 58%, 20% and 22% true positive or true negative evaluated tumors, and by FS in 83%, 5% and 12% true positive or true negative evaluated tumors. Conclusions The current analysis showed a superiority of FS compared with FNAC regarding the diagnosis of malignancy and especially of tumor typing. FNAC alone is not prone in many cases to determine the surgical management of primary parotid carcinomas.

scholarly journals Rapid SARS-CoV-2 antigen detection assay in comparison with real-time RT-PCR assay for laboratory diagnosis of COVID-19 in Thailand

2020 ◽  
Vol 17 (1) ◽  
Author(s):  
Chutikarn Chaimayo ◽  
Bualan Kaewnaphan ◽  
Nattaya Tanlieng ◽  
Niracha Athipanyasilp ◽  
Rujipas Sirijatuphat ◽  
...  
Keyword(s):  
Real Time ◽  
Sensitivity And Specificity ◽  
False Negative ◽  
Laboratory Diagnosis ◽  
Antigen Detection ◽  
Rt Pcr ◽  
Pcr Assay ◽  
Screening Assay ◽  
The Real ◽  
Pcr Test

Abstract Background The Coronavirus disease 2019 (COVID-19) pandemic continues to spread across the world. Hence, there is an urgent need for rapid, simple, and accurate tests to diagnose severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Performance characteristics of the rapid SARS-CoV-2 antigen detection test should be evaluated and compared with the gold standard real-time reverse transcription-polymerase chain reaction (RT-PCR) test for diagnosis of COVID-19 cases. Methods The rapid SARS-CoV-2 antigen detection test, Standard™ Q COVID-19 Ag kit (SD Biosensor®, Republic of Korea), was compared with the real-time RT-PCR test, Allplex™ 2019-nCoV Assay (Seegene®, Korea) for detection of SARS-CoV-2 in respiratory specimens. Four hundred fifty-four respiratory samples (mainly nasopharyngeal and throat swabs) were obtained from COVID-19 suspected cases and contact individuals, including pre-operative patients at Siriraj Hospital, Bangkok, Thailand during March–May 2020. Results Of 454 respiratory samples, 60 (13.2%) were positive, and 394 (86.8%) were negative for SARS-CoV-2 RNA by real-time RT-PCR assay. The duration from onset to laboratory test in COVID-19 suspected cases and contact individuals ranged from 0 to 14 days with a median of 3 days. The rapid SARS-CoV-2 antigen detection test’s sensitivity and specificity were 98.33% (95% CI, 91.06–99.96%) and 98.73% (95% CI, 97.06–99.59%), respectively. One false negative test result was from a sample with a high real-time RT-PCR cycle threshold (Ct), while five false positive test results were from specimens of pre-operative patients. Conclusions The rapid assay for SARS-CoV-2 antigen detection showed comparable sensitivity and specificity with the real-time RT-PCR assay. Thus, there is a potential use of this rapid and simple SARS-CoV-2 antigen detection test as a screening assay.

scholarly journals Evaluation of a Multiplex Real-Time PCR Assay for Detecting Major Bacterial Enteric Pathogens in Fecal Specimens: Intestinal Inflammation and Bacterial Load Are Correlated in Campylobacter Infections

2016 ◽  
Vol 54 (9) ◽  
pp. 2262-2266 ◽  
Author(s):  
Nadia Wohlwend ◽  
Sacha Tiermann ◽  
Lorenz Risch ◽  
Martin Risch ◽  
Thomas Bodmer
Keyword(s):  
Real Time ◽  
Real Time Pcr ◽  
Bacterial Load ◽  
Positive Culture ◽  
Fecal Calprotectin ◽  
Enteric Pathogens ◽  
Significant Linear Trend ◽  
Content Type ◽  
Culture Positive ◽  
Culture Negative

A total of 1,056 native or Cary-Blair-preserved stool specimens were simultaneously tested by conventional stool culturing and by enteric bacterial panel (EBP) multiplex real-time PCR forCampylobacter jejuni,Campylobacter coli,Salmonellaspp., and shigellosis disease-causing agents (Shigellaspp. and enteroinvasiveEscherichia coli[EIEC]). Overall, 143 (13.5%) specimens tested positive by PCR for the targets named above; 3 coinfections and 109 (10.4%)Campylobacterspp., 17 (1.6%)Salmonellaspp., and 20 (1.9%)Shigellaspp./EIEC infections were detected. The respective positive stool culture rates were 75 (7.1%), 14 (1.3%), and 7 (0.7%). The median threshold cycle (CT) values of culture-positive specimens were significantly lower than those of culture-negative ones (CTvalues, 24.3 versus 28.7;P< 0.001), indicating that the relative bacterial load per fecal specimen was significantly associated with the culture results. InCampylobacterinfections, the respective median fecal calprotectin concentrations in PCR-negative/culture-negative (n =40), PCR-positive/culture-negative (n =14), and PCR-positive/culture-positive (n =15) specimens were 134 mg/kg (interquartile range [IQR], 30 to 1,374 mg/kg), 1,913 mg/kg (IQR, 165 to 3,813 mg/kg), and 5,327 mg/kg (IQR, 1,836 to 18,213 mg/kg). Significant differences were observed among the three groups (P< 0.001), and a significant linear trend was identified (P< 0.001). Furthermore, the fecal calprotectin concentrations andCTvalues were found to be correlated (r= −0.658). Our results demonstrate that molecular screening ofCampylobacterspp.,Salmonellaspp., andShigellaspp./EIEC using the BD Max EBP assay will result in timely diagnosis and improved sensitivity. The determination of inflammatory markers, such as calprotectin, in fecal specimens may aid in the interpretation of PCR results, particularly for enteric pathogens associated with mucosal damage and colonic inflammation.

scholarly journals Efficacy of itraconazole oral solution using an alternating-week pulse therapy regimen for treatment of cats with experimental Microsporum canis infection

2017 ◽  
Vol 20 (10) ◽  
pp. 869-874 ◽  
Author(s):  
Christopher Puls ◽  
Aaron Johnson ◽  
Karrie Young ◽  
Jonathan Hare ◽  
Kelly Rosenkrans ◽  
...  
Keyword(s):  
Clinical Cure ◽  
Pulse Therapy ◽  
Oral Solution ◽  
Controlled Study ◽  
Microsporum Canis ◽  
Fungal Culture ◽  
Mycological Cure ◽  
Therapy Regimen ◽  
Treatment Groups ◽  
Cure Rates

Objectives The objective of this study was to evaluate itraconazole 10 mg/ml oral solution for the treatment of Microsporum canis infection using an alternating-week pulse therapy regimen in a controlled laboratory setting. Methods Eighty cats with experimentally induced infections were randomly assigned to treatment (itraconazole vs control [sterile water]), administered 5 mg/kg PO q24h for 1 week on alternate weeks for 5 weeks, followed by a 4 week follow-up period. Topical therapeutic treatment was not administered. Cats were individually housed in stainless steel cages that were cleaned and disinfected daily. Study measures included weekly fungal cultures, clinical lesion scores, Wood’s lamp examination and periodic laboratory monitoring. Mycological cure was defined as two consecutive negative cultures. Results Itraconazole-treated cats had significantly greater ( P = 0.0003) mycological cure compared with untreated controls (24/40 [60%] vs 1/40 [2.5%], respectively) and all of these reached clinical cure and had negative final Wood’s lamp examinations. Furthermore, 36/40 (90%) treated cats had at least one negative fungal culture by the end of the study vs only 3/40 (7.5%) control cats. For both treatment groups, prevalence of clinical cure peaked at the end of the study (week 9), with 39/40 (97.5%) itraconazole-treated cats and 6/40 (15%) control cats achieving clinical cure. Wood’s lamp negative examination rates were significantly greater ( P <0.0001) for itraconazole-treated cats compared with controls (39/40 cats [97.5%] vs 6/40 [15%], respectively) and followed the same pattern of improvement as primary clinical lesions. Conclusions and relevance In this controlled study, orally administered itraconazole using a 5 mg/kg pulse-dose treatment regimen reduced the time to mycological cure and increased both mycological and clinical cure rates compared with untreated controls.

scholarly journals Evaluation of the Multiplex Real-Time PCR DermaGenius® Assay for the Detection of Dermatophytes in Hair Samples from Senegal

2021 ◽  
Vol 8 (1) ◽  
pp. 11
Author(s):  
Mouhamadou Ndiaye ◽  
Rosalie Sacheli ◽  
Khadim Diongue ◽  
Caroline Adjetey ◽  
Rajae Darfouf ◽  
...  
Keyword(s):  
Real Time ◽  
Real Time Pcr ◽  
Melting Curve ◽  
Diagnostic Methods ◽  
Melting Curve Analysis ◽  
Microsporum Canis ◽  
Molecular Tools ◽  
Pcr Assay ◽  
Epidermophyton Floccosum ◽  
Hair Samples

For the successful treatment of dermatophytoses, especially tinea capitis, there is a need for accurate and rapid diagnostic methods. A lot of recent literature has focused on the detection of dermatophytes directly on sample material such as nails, hair and skin scrapings. Molecular tools offer the ability to rapidly diagnose dermatophytosis within 48 h. This study aimed to compare the results of a commercial real-time PCR (real-time PCR) assay DermaGenius®(DG) 2.0 complete multiplex kit with those of conventional diagnostic methods (direct microscopy and culture). A total of 129 hair samples were collected in Dakar (Senegal) from patients suspected of dermatophytosis. DG was applied for the molecular detection of Candida albicans, Trichophyton rubrum/soudanense, T. interdigitale, T. tonsurans, T. mentagrophytes, T. violaceum, Microsporum canis, M. audouinii, Epidermophyton floccosum, T. benhamiae and T. verrucosum. Dermatophytes species and C. albicans were differentiated by melting curve analysis. The sensitivity and specificity of the PCR assay were 89.3% and 75.3%, respectively. DG PCR was significantly more sensitive than culture (p < 0.001). DG PCR is fast and robust to contamination. In this paper, the main questions discussed were the replacement of culture by a broad-spectrum fungal real-time PCR and the implementation of DG PCR into a routine laboratory in Senegal.

The prevalence of immediate and delayed type hypersensitivity reactions to Microsporum canis antigens in cats

2003 ◽  
Vol 5 (3) ◽  
pp. 161-166 ◽  
Author(s):  
KA Moriello ◽  
DJ DeBoer ◽  
J Greek ◽  
K Kuhl ◽  
M Fintelman
Keyword(s):  
Immune Response ◽  
Cellular Immune Response ◽  
Spontaneous Recovery ◽  
Delayed Type Hypersensitivity ◽  
Microsporum Canis ◽  
Hypersensitivity Reactions ◽  
Intradermal Testing ◽  
Cellular Immune ◽  
Culture Positive ◽  
Culture Negative

Spontaneous recovery from Microsporum canis infections in cats is thought to be dependent on the development of a competent immune response. The purpose of this study was to determine the prevalence of positive delayed type hypersensitivity reactions in cats with and without dermatophytosis. Four groups of cats were intradermally skin tested with M canis extract and test sites were evaluated both subjectively and objectively at 0, 24 and 48 h after injection. Delayed intradermal testing (IDT) reactions were absent in cats not exposed to dermatophytosis ( n=20); infected–recovered cats ( n=38 culture negative lesion negative and n=43 lesion negative but culture positive) had significantly larger IDT reactions than unexposed cats and cats that were still actively infected ( n=18). Based on the results of this study, IDT with M canis extract can be used to assess the cellular immune response of cats with dermatophytosis.

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