Evaluation of a new rapid fluorescence immunoassay for the diagnosis of dengue and Zika virus infection

BACKGROUND

Dengue (DENV) and Zika virus (ZIKV) are important mosquito-transmitted viruses.

OBJECTIVES

To investigate the performance of Standard F, Fluorescence Immunoassay (FIA, SD Biosensor Inc., Suwon, South Korea) providing results in 15 min to detect DENV IgG, IgM and NS1Ag, and ZIKV IgG, IgM, and Ag.

STUDY DESIGN

A well-characterized panel of patient samples (11 acute DENV, 11 acute ZIKV, 10 past DENV, 10 past ZIKV infection, 36 with other conditions) were tested with the FIA test.

RESULTS

In acute DENV infection, the combination of FIA-NS1Ag and/or IgM positivity showed a sensitivity of 100%. In past DENV, FIA-IgG test showed a sensitivity of 70%. Specificity of FIA-DENV NS1Ag, IgG, and IgM was 87.5%, 83.5%, and 91.7%, respectively. The sensitivity of FIA-ZIKV IgM and FIA-ZIKV Ag, in confirmed acute infection, was 72.7% and 9.1%, respectively. FIA-ZIKV Ag did not improve the sensitivity in detecting acute ZIKV infection, being positive only in one IgM positive sample. In past ZIKV infection (32-183 days after symptom onset), FIA-ZIKV IgG and IgM showed a sensitivity of 40% and 80% respectively, generating an overall 90% sensitivity. Specificity of FIA-ZIKV Ag, IgM, and IgG was 92.6%, 100%, and 97%, respectively.

CONCLUSION

FIA test, a rapid and easy to perform assay, showed high sensitivity to detect acute DENV infection, but lower in acute ZIKV infection. In past ZIKV infections, the best performance of FIA test is obtained by combining detection of IgG and IgM.

Mycobacterium monacense sp. nov

Four bacterial strains were isolated from independent clinical specimens in different countries and their genotypic and phenotypic characters support their classification in a novel species within the genus Mycobacterium. One strain was clearly responsible for a severe, post-traumatic wound infection in a healthy boy. The novel species, for which the name Mycobacterium monacense sp. nov. is proposed, is yellow-pigmented, non-photochromogenic and grows in less than a week on solid medium. Based on phenotypic investigations alone, distinction of these four strains from known scotochromogenic rapidly growing strains is problematic. However, the novel strains differ from any other mycobacterium in each of the molecular species markers investigated: the 16S rRNA gene, the 16S-23S rRNA gene internal transcribed spacer and the hsp65 gene. Of the strains investigated, two different sequevars were detected for the hsp65 region. Phylogenetic analysis revealed that these four strains were most closely related to Mycobacterium doricum. The type strain of Mycobacterium monacense sp. nov. is B9-21-178T (=DSM 44395T=CIP 109237T).

Mycobacterium sherrisii isolation from a patient with pulmonary disease

The characterization of 2 clinical isolates of Mycobacterium sherrisii provides further phenotypic and genotypic information beyond that reported in the article that originally described this species. One of our strains was responsible for pulmonary disease in a middle-aged non-HIV patient; thus, confirming the potential pathogenicity of this species previously reported only in an HIV-positive patient.

Successfully treated spondylodiscitis due to a previously unreported mycobacterium

A non-tuberculous mycobacterium was isolated, following a vertebral needle aspiration, from the blood of a patient with severe spondylodiscitis. The strain turned out to be different from any known mycobacterial species and was quite drug-susceptible in vitro. The patient improved markedly following treatment with meropenem, clarithromycin and amikacin.

Infections due to the newly described species Mycobacterium parascrofulaceum

We report on four cases of infection by the recently described species Mycobacterium parascrofulaceum. In two cases the mycobacterium was isolated from AIDS patients, while in the others it was responsible for pulmonary disease in elderly men. Our findings suggest that M. parascrofulaceum is an opportunistic pathogen, like many other nontuberculous mycobacterial species.

Taxonomic and phylogenetic status of non-tuberculous mycobacteria in a Caribbean setting

This report describes detailed taxonomic and phylogenetic analysis of 15 non-tuberculous mycobacteria (NTMs) isolated from human pathological specimens in a Caribbean setting (12 slow-growers and three rapid-growers) that were not identified by cultural and biochemical tests and drug-susceptibility results. These isolates were further studied using PCR restriction fragment length polymorphism analysis (PRA) of a 441bp hsp65 fragment, as well as the sequencing of 16S rDNA and hsp65 DNA, and HPLC of the mycolic acids. Our results showed that taxonomic position of well-defined NTMs was resolved by PRA and sequencing of hsp65, nonetheless, it was not suitable to investigate rarely observed or new strains that required 16S rDNA sequencing and HPLC for a definite response. Unrooted neighbor-joining phylogenetic trees were drawn based upon the 16S rDNA and hsp65 sequences of the 15 NTMs compared with those from described species (73 for 16S rDNA and 45 for hsp65). For most of the NTMs not showing an exactly matching sequence with either hsp65 or 16S rDNA in the GenBank, the phylogenetic tree was able to provide with useful indications about their relatedness to known species. In such a case, a concording HPLC pattern with the sequence data and the place of the strain within the tree could lead to a potential identification. We also identified three identical isolates that define a new mycobacterial species within the group of M. simiae-related mycobacteria. The isolation and characterization of mycobacteria from new settings may lead to identify potential pathogens that may propogate in future because of increased human migration, travels, and climatic and ecological changes of the modern world.

Mycobacterium florentinum sp. nov., isolated from humans

Eight mycobacterial strains isolated during an 11 year period from the sputum of independent patients with various pulmonary disorders and, in one case, from a lymph node of a young girl, were found to present identical features. Phenotypic and genotypic characteristics revealed that the most closely related species to these test isolates were Mycobacterium triplex and Mycobacterium lentiflavum. However, the lipids of the cell wall of the test isolates differed from those of the latter species by TLC and presented unique profiles by both GC and HPLC. Genotypic analysis showed that they had unique 16S rRNA gene and internal transcribed spacer (ITS) sequences, and could be differentiated from all other mycobacterial strains by PCR restriction analysis of hsp65. The strains presented high resistance to antimycobacterial drugs. The name Mycobacterium florentinum sp. nov. is proposed for this taxon, with strain FI-93171T (=DSM 44852T=CIP 108409T) as the type strain.

Mycobacterium triplex pulmonary disease in immunocompetent host

Mycobacterium triplex, a recently described, potentially pathogenic species, caused disease primarily in immunocompromised patients. We report a case of pulmonary infection due to this mycobacterium in an immunocompetent patient and review the characteristics of two other cases. In our experience, Mycobacterium triplex pulmonary infection is unresponsive to antimycobacterial chemotherapy.

Mycobacterium lentiflavum as an emerging causative agent of cervical lymphadenitis

A lymph node excision was performed on a 45-year-old woman with left cervical swelling. The disorder which developed after the patient had undergone oral surgery for a severe periodontal disease failed to respond to antimicrobial chemotherapy. A mycobacterial strain subsequently identified by high-performance liquid chromatography analysis of cell wall mycolic acids as Mycobacterium lentiflavum grew from the excised specimen. This case and previously published reports highlight the relevance of M. lentiflavum as an emerging causative agent of mycobacterial cervical lymphadenitis.

Proposal to elevate the genetic variant MAC-A, included in the Mycobacterium avium complex, to species rank as Mycobacterium chimaera sp. nov

The possibility that the strains included within the Mycobacterium avium complex (MAC), but not belonging either to M. avium or to Mycobacterium intracellulare, may be members of undescribed taxa, has already been questioned by several taxonomists. A very homogeneous cluster of 12 strains characterized by identical nucleotide sequences both in the 16S rDNA and in the 16S–23S internal transcribed spacer was investigated. Similar strains, previously reported in the literature, had been assigned either to the species M. intracellulare on the basis of the 16S rDNA similarity or to the group of MAC intermediates. However, several phenotypical and epidemiological characteristics seem to distinguish these strains from all other MAC organisms. The unique mycolic acid pattern obtained by HPLC is striking as it is characterized by two clusters of peaks, instead of the three presented by all other MAC organisms. All of the strains have been isolated from humans and all but one came from the respiratory tract of elderly people. The clinical significance of these strains, ascertained for seven patients, seems to suggest an unusually high virulence. The characteristics of all the strains reported in the literature, genotypically identical to the ones described here, seem to confirm our data, without reports of isolations from animals or the environment or, among humans, from AIDS patients. Therefore, an elevation of the MAC variant was proposed and characterized here, with the name Mycobacterium chimaera sp. nov.; this increases the number of species included in the M. avium complex. The type strain is FI-01069T (=CIP 107892T=DSM 44623T).

Evaluation of INNO-LiPA MYCOBACTERIA v2: improved reverse hybridization multiple DNA probe assay for mycobacterial identification

INNO-LiPA MYCOBACTERIA (Innogenetics, Ghent, Belgium) is a reverse hybridization DNA probe assay that has been recently improved by increasing the number of identifiable mycobacterial species to 16. Our assessment, performed with 197 mycobacteria belonging to 81 taxa, revealed 100% specificity and sensitivity for 20 out of 23 probes. The probes specific for Mycobacterium fortuitum complex, for the Mycobacterium avium-intracellulare-scrofulaceum group, and for Mycobacterium intracellulare type 2 cross-reacted with several mycobacteria rarely isolated from clinical specimens. The overall sensitivity was 100%, and the overall specificity was 94.4%.

Mycobacterium elephantis: not an exceptional finding in clinical specimens

Following the recent report of new 16S rDNA sequences of Mycobacterium elephantis, three clinical strains suspected to belong to such species were investigated using biochemical and cultural tests, high performance liquid chromatography of cell wall mycolic acids and genetic sequencing. Antimicrobial susceptibility was also determined. The findings confirmed recent data concerning human isolates of this new mycobacterium and identified a new 16S rDNA sequevar for this species.

Evaluation of the BDProbeTec ET system for direct detection of Mycobacterium tuberculosis in pulmonary and extrapulmonary samples: a multicenter study

We evaluated the BDProbeTec ET system (Becton Dickinson, Sparks, Md.), a strand displacement amplification-based technique, for direct detection of Mycobacterium tuberculosis in 867 clinical samples. Of 294 extrapulmonary specimens, 52 had positive results by both BDProbeTec ET and culture and 209 had negative results by both methods; sensitivity and specificity were 76.5 and 95.9%, respectively. After resolution of discrepancies, the sensitivity rose to 77.8%.

Multicenter evaluation of the new HIV DUO assay for simultaneous detection of HIV antibodies and p24 antigen

A multicenter survey was performed to evaluate a new semi-automated human immunodeficiency virus fourth generation antibodies and antigen simultaneous assay. This assay showed a sensitivity of 100% and specificity of 99.6% among sera obtained from hospitalized patients or blood donors. Sera obtained from commercially available as well as in-house seroconversions were tested showing that HIV DUO is able to reveal an infected state in 11 out of 14 cases earlier than conventional tests. This new assay improves old test performances in terms of sensitivity, maintaining specificity at very high levels.