Value and Interpretation of Serological Tests for the Diagnosis of Cryptococcosis

MAXIMAL SEROLOGICAL DIAGNOSIS OF CRYPTOCOCCOSIS MAY BE ACCOMPLISHED THROUGH THE CONCURRENT USE OF THREE TESTS: the latex agglutination (LA) test for cryptococcal antigen, and the indirect fluorescent antibody (IFA) and tube agglutination (TA) tests for Cryptococcus neoformans antibodies. These tests were applied to 141 serum and cerebral spinal fluid specimens from 66 culturally proven cases of cryptococcosis and to 42 sera from normal subjects and from patients with other systemic mycotic diseases. The LA test was sensitive and completely specific; of the sera from proven cases, 55% were positive. With the TA test, 37% of the specimens were positive and the test was highly specific. With the IFA test, 38% of the specimens were positive and the test appears to be the least specific of the three. Cross-reactions were most evident with blastomycosis and histoplasmosis case sera. When the three tests were used concurrently, 87% of the cryptococcosis case specimens were positive and permitted a presumptive diagnosis of C. neoformans infections in 61 (92%) of the 66 patients whose specimens were examined.     

Indirect Fluorescent-Antibody and Quantitative Agar-Gel Immunodiffusion Tests for the Serological Diagnosis of Paracoccidioidomycosis

The value of various serological tests in the diagnosis of paracoccidioidomycosis was studied. Quantitative agar-gel immunodiffusion and indirect immunofluorescent tests were performed, and the results were compared with those of complement fixation and qualitative agar-gel procedures. The quantitative immunodiffusion procedure was found to serve as the simplest and safest quantitative test that could be performed for evaluation purposes, whereas the indirect fluorescent-antibody test gave nonspecific reactions and, as such, proved unsuitable.     

Serological Diagnosis of Human Melioidosis with Indirect Hemagglutination and Complement Fixation Tests

An indirect hemagglutination (IHA) test and a complement fixation (CF) test were evaluated from test results on sera from 212 human melioidosis patients of which 119 were culturally proved cases. Significant antibody titers (IHA titers of 1:40 or greater and CF titers of 1:4 or greater) were demonstrated with either test in all except five patients. IHA and CF titers ranged as high as 1:20,480 and 1:1,024, respectively. Antibodies were usually demonstrated by both tests 1 week after onset of disease. Transient seronegative reactions during the course of disease were seen in sera of approximately 19% of the patients with either IHA and CF but rarely with both tests. High titers in either test were obtained by the third week of disease and reached maximum levels in 4 to 5 months. Titers usually were detectable for 9 or more months. Antibodies were detected by IHA and CF tests in 80 to 100% of the sera obtained at various time intervals from 9 months to 2 or more years after disease onset. Antibody persistence occurred in patients who had a short disease course, as well as in patients with prolonged, complicated infections. The IHA test had excellent specificity when evaluated with normal human sera and diverse antimicrobial sera from hyperimmunized rabbits and human patients. The CF antigen appeared to contain common antigens with some but not all types of Pseudomonas aeruginosa. The specificity of the CF antigen could be enhanced without appreciable effect on its sensitivity by use of a titer of 1:8 in lieu of 1:4 as a criterion for a significant reaction. Either test could be used advantageously for the laboratory diagnosis of melioidosis.     

Evaluation of Four Commercial Multiplex Molecular Tests for the Diagnosis of Acute Respiratory Infections

Acute Respiratory Infections (ARIs) are responsible for considerable morbidity and mortality worldwide. Documentation of respiratory specimens can help for an appropriate clinical management with a significant effect on the disease progress in patient, the antimicrobial therapy used and the risk of secondary spread of infection. Here, we compared the performances of four commercial multiplex kits used in French University Hospital diagnostic microbiology laboratories for the detection of ARI pathogens (i.e., the xTAG Respiratory Viral Panel Fast, RespiFinder SMART 22, CLART PneumoVir and Fast Track Diagnostics Respiratory Pathogen 33 kits). We used a standardised nucleic acids extraction protocol and a comprehensive comparative approach that mixed reference to well established real-time PCR detection techniques and analysis of convergent positive results. We tested 166 respiratory clinical samples and identified a global high degree of correlation for at least three of the techniques (xTAG, RespiFinder and FTD33). For these techniques, the highest Youden’s index (YI), positive predictive (PPV) and specificity (Sp) values were observed for Core tests (e.g., influenza A [YI:0.86–1.00; PPV:78.95–100.00; Sp:97.32–100.00] & B [YI:0.44–1.00; PPV:100.00; Sp:100.00], hRSV [YI:0.50–0.99; PPV:85.71–100.00; Sp:99.38–100.00], hMPV [YI:0.71–1.00; PPV:83.33–100.00; Sp:99.37–100.00], EV/hRV [YI:0.62–0.82; PPV:93.33–100.00; Sp:94.48–100.00], AdV [YI:1.00; PPV:100.00; Sp:100.00] and hBoV [YI:0.20–0.80; PPV:57.14–100.00; Sp:98.14–100.00]). The present study completed an overview of the multiplex techniques available for the diagnosis of acute respiratory infections.     

Diagnosis of Whooping Cough: Comparison of Serological Tests with Isolation of Bordetella Pertussis

Antibody titres for Bordetella pertussis in paired sera from 223 children with suspected whooping cough showed good correlation by complement fixation and agglutination techniques. The patient''s age was related to serological responses and in a different way to B. pertussis isolations: in 73 children under 6 months of age B. pertussis was isolated from nasopharyngeal secretions in 42% and serological findings were positive in 19%; in 11 patients over 1 year of age serological tests were positive in 65% and cultures in 19%.B. pertussis was isolated from 59 out of 210 patients, while rising antibody titres were found in a further 43 from whom no isolations were made; thus 102 (49%) out of 210 showed evidence of infection with B. pertussis. Serotype 1,3 was the commonest serotype isolated from both immunized and unimmunized children. Previous immunization appeared to reduce the chances of isolating B. pertussis.     

Volatile Organic Compounds: Upcoming Role in Diagnosis of Invasive Mould Infections

Purpose of Review

Breath testing for fungal respiratory infections has great promise as samples can be obtained by non-invasive, repeatable techniques that can be done on a wide range of patients including children, the confused and from those in the intensive care unit (ICU). We have reviewed progress toward development of test applicable to clinical practice.

Recent Findings

Many volatile organic compounds (VOCs) have been identified, especially from key pathogens such as Aspergillus fumigatus, but very few clinical trials have been performed. The most convincing of these demonstrated that Aspergillus species could be identified by gas chromatography with mass spectrometry in breath samples of at risk patients with high sensitivity (94%) and specificity (93%) compared with the European Organization for Research and Treatment of Cancer/Mycosis Study Group (EORTC/MSG) gold standard.

Summary

Significant progress has been made but further studies are needed to validate these recent findings and identify VOCs from other pathogenic fungi using GC-MS, and clinical trials performed using faster and less demanding analytic platforms that could be used in clinical laboratories.

     

Comparison of Three Serological Tests in Gonococcal Infection

Three serological tests used in the diagnosis of gonococcal infection were compared with cultural techniques in 857 females attending the Prenatal and Gynaecology Clinics at the Winnipeg General Hospital. The tests evaluated were the microflocculation technique (MFT), the indirect fluorescent-antibody technique (IFAT), and the complement-fixation technique (CFT). One hundred six patients had positive cultures for Neisseria gonorrhoeae. In this population, the MFT was reactive in 80 patients (75.4%), the IFAT was reactive in 74 (69.8%), and the CFT was reactive in 33 (31.1%). In the 751 patients with negative cultures, the MFT was positive in 11.4%, the IFAT was positive in 17.4%, and the CFT was positive in 10.5%. Sera from 9 of 10 patients with gonococcal arthritis were positive with the MFT.     

Studies on Serological Cross-Reaction in Sequential Flavivirus Infections

Acute- and convalescent-phase sera from patients with dengue (DEN) hemorrhagic fever (DHF) and Japanese encephalitis (JE) that contained pre-existing flavivirus antibodies were tested for cross-reacting antibodies to DEN, JE and yellow fever (YF) viruses by a neutralization (N) test. A fourfold or greater rise in N antibody titer in the convalescent-phase was considered significant. Of 39 DHF cases, obtained at Chiang Mai University Hospital, Thailand, 15 (38.5%) showed a rise in DEN antibody titer, while another 15 (38.5%) showed a significant rise in both DEN and JE N antibody titers. On the other hand, eight (61.5%) of 13 JE cases obtained at the same Hospital, showed a significant rise in JE antibody titer, while two (15.4%) showed a significant rise in both DEN and JE antibody titers. Sucrose gradient centrifugation and fractionation of these two cross-reactive JE sera revealed that IgM class antibody was specific for JE, while IgG class antibody was cross-reactive. Of three JE cases with pre-existing YF antibody obtained in Okinawa, Japan, two showed a significant rise in YF and JE antibodies. Both IgM and IgG class antibodies to YF virus were elevated. These results indicate that the cross-reactivity among flaviviruses in different subgroups (complexes), was observed quite often, even by the N test, in sequential flavivirus infection.     

Update on the Evolving Role of MALDI-TOF MS for Laboratory Diagnosis of Fungal Infections

MALDI-TOF MS is a recent technique, which revolutionized bacterial species identifications, due to its simplicity, accuracy and speed of analysis. The same efficiency of species identification for fungi is highly sought. This review aims to discuss the evolving role of MALDI-TOF MS in the laboratory diagnosis of fungal infections. Yeast identifications are increasingly being performed with MALDI-TOF MS in a routine setting with good results. A further extension of the libraries will further increase its potential. Direct identification of yeast in blood cultures and MALDI-TOF MS susceptibility testing are new promising applications. The identification of filamentous fungi on MALDI-TOF MS is still challenging, but knowledge and experience is taking huge leaps forward.     

Invasive Mold Infections in Patients with Chronic Lymphoproliferative Disorders

Purpose of the Review

This review summarizes data about epidemiology, treatment, and risk factors for invasive fungal infections (IFI) in patients affected by chronic lymphocytic leukemia (CLL), multiple myeloma (MM), and indolent non Hodgkin lymphoma (iNHL).

Recent Findings

Despite advances in the prognosis and treatment of hematological malignancies in recent years, susceptibility to infection remains a significant challenge to patient care. A large amount of data regarding patients with acute leukemias have been published while little information is available on incidence of IFI in chronic lymphoproliferative disorders (CLD).

Summary

The overall incidence of IFI in CLL patients is reported from 1.3 to 7.8% and the main risk factors are related to disease status (high-risk in relapsed/refractory disease), number of previous chemotherapy regimens, and Ig levels.In MM, most of the IFI occurred during refractory or progressive disease. The rate of IFI ranges from 0.5 to 12.3%. Neutropenia is the main risk factor in MM and risk seems to be related to its duration and severity. The overall incidence of IFI in iNHL ranges from 0.5 to 4% and the most important risk factors are disease status (high-risk in relapsed/refractory and advance stage disease) and type of treatment (high-risk for steroid administration, intensive chemotherapy with prolonged neutropenia, use of monoclonal antibodies and purine analogs).