Evaluation of an Immunochromatographic Test for Rapid and Reliable Serodiagnosis of Human Tularemia and Detection ofFrancisella tularensis-Specific Antibodies in Sera from Different Mammalian Species

Abstract

Tularemia is a highly contagious infectious zoonosis caused by the bacterial agent Francisella tularensis.Serology is still considered to be a cornerstone in tularemia diagnosis due to the low sensitivity of bacterial culture and the lack of standardization in PCR methodology for the direct identification of the pathogen. We developed a novel immunochromatographic test (ICT) to efficiently detect F. tularensis-specific antibodies in sera from humans and other mammalian species (nonhuman primate, pig, and rabbit). This new tool requires none or minimal laboratory equipment, and the results are obtained within 15 min. When compared to the method of microagglutination, which was shown to be more specific than the enzyme-linked immunosorbent assay, the ICT had a sensitivity of 98.3% (58 positive sera were tested) and a specificity of 96.5% (58 negative sera were tested) on human sera. On animal sera, the overall sensitivity was 100% (22 positive sera were tested) and specificity was also 100% (70 negative sera were tested). This rapid test preferentially detects IgG antibodies that may occur early in the course of human tularemia, but further evaluation with human sera is important to prove that the ICT can be a valuable field test to support a presumptive diagnosis of tularemia. The ICT can also be a useful tool to monitor successful vaccination with subunit vaccines or live vaccine strains containing lipopolysaccharide (e.g., LVS) and to detect seropositive individuals or animals in outbreak situations or in the context of epidemiologic surveillance programs in areas of endemicity as recently recommended by the World Health Organization.

Francisella tularensis: No Evidence for Transovarial Transmission in the Tularemia Tick Vectors Dermacentor reticulatus and Ixodes ricinus

“…For FISH assays, we utilized the 23S rRNA universal probe for F . tularensis W_all1448CY5 (CAACCATTCGCCAGGCCT labelled at the 5’ with the fluorochrome Cy5, absorption and emission at 650 nm and 670 nm, respectively) [ 27 ]. An additional probe, EUB338CY3 (GCTGCCTCCCGTAGGAGT labelled at the 5’ with the fluorochrome Cy3, absorption and emission at 550 nm and 570 nm, respectively), routinely used as a universal bacterial probe, was used as bacterial positive control [ 28 ].…”

The use of Matrix-assisted laser desorption ionization-time of flight mass spectrometry in the identification of Francisella tularensis

“…Laboratory diagnosis is essential for optimum treatment. Since the mortality rate is high in most severe cases, early diagnosis of tularemia is crucial [ 3 - 6 ].…”

“…Conventional culture and biochemical tests, as well as molecular methods, have been used in clinical microbiology laboratories for the identification of Francisella spp. [ 2 , 4 - 6 ]. Species and subspecies are subsequently determined by testing biochemical reactions/tests such as production of acid from carbohydrates (maltose, d-glucose, lactose, sucrose, and glycerol), citrulline ureidase activity, H 2 S production in cysteine-supplemented medium, and β-lactamase production.…”

Features of humoral answer in experimental animal tularemia with different sensitivity to infection

“…При диагностике туляремии оценка клеточного иммунитета является самым надежным методом специфической диагностики, тем не менее в обычной практической медицине наиболее распространенным остается определение специфических антител к возбудителю туляремии в сыворотке крови [4,5,15,16,17]. Традиционно в агглютинационных тестах для серодиагностики используются убитые цельные микробные клетки, однако в последние годы для выявления специфических антител чаще всего используют очищенный препарат ЛПС F. tularensis [6,10,15,16,17].…”