Multimode detection of β-glycosidase and pathogenic bacteria via cation exchange assisted signal amplification

A rapid strategy for the β-glycosidase (β-Gal) and Escherichia coli (E. coli) sensing is presented, which is based on selective recognition reactions of QDs using visualization/fluorescence (FL)/atomic fluorescence spectrometry (AFS)/inductively coupled plasma mass spectrometry (ICP-MS) multimode assay. CdTe QDs can selectively recognize Ag⁺ and Ag NPs with a cation exchange reaction (CER) where Ag⁺ triggers the release of Cd²⁺ and quenches the fluorescence signal of QDs. Taking advantage of the fact that β-Gal can hydrolyze 4-Aminophenyl β-D-galactopyranoside (PAPG) to produce p-aminophenol (PAP), which has the ability to reduce Ag⁺ to form Ag NPs. The β-Gal can be easily detected by visualization or FL in a turn-on manner. Furthermore, combining with the selective separation of Cd²⁺ by filter membrane, AFS and ICP-MS with higher sensitivity were used for the determination of the enzyme. Under optimized conditions, the system limits of detections (LODs) were 0.01 U/L, 0.03 mU/L, and 0.02 mU/L using FL, AFS, and ICP-MS as the detector, respectively. The relative standard deviations (RSDs, n = 7) for 0.1 U/L β-Gal were 2.2, 2.0, and 1.3% using FL/AFS/ICP-MS as the detector, respectively. And 0.1 U/L of β-Gal can be discriminated from the blank solution with the naked eye. In addition, given that the β-Gal can serve as an indicator of E. coli, we have successfully applied this strategy for the detection of E. coli with a LOD of 25 CFU/mL. Application of the method was demonstrated by analyzing human urine samples and milk samples for ultra-trace detection of E. coli. Graphical abstract The CVG-AFS/ICP-MS/visual/FL multimode β-Gal and E.coli detection via CER.

Fast and Accurate Bacterial Species Identification in Urine Specimens Using LC-MS/MS Mass Spectrometry and Machine Learning

Fast identification of microbial species in clinical samples is essential to provide an appropriate antibiotherapy to the patient and reduce the prescription of broad-spectrum antimicrobials leading to antibioresistances. MALDI-TOF-MS technology has become a tool of choice for microbial identification but has several drawbacks: it requires a long step of bacterial culture before analysis (≥24 h), has a low specificity and is not quantitative. We developed a new strategy for identifying bacterial species in urine using specific LC-MS/MS peptidic signatures. In the first training step, libraries of peptides are obtained on pure bacterial colonies in DDA mode, their detection in urine is then verified in DIA mode, followed by the use of machine learning classifiers (NaiveBayes, BayesNet and Hoeffding tree) to define a peptidic signature to distinguish each bacterial species from the others. Then, in the second step, this signature is monitored in unknown urine samples using targeted proteomics. This method, allowing bacterial identification in less than 4 h, has been applied to fifteen species representing 84% of all Urinary Tract Infections. More than 31,000 peptides in 190 samples were quantified by DIA and classified by machine learning to determine an 82 peptides signature and build a prediction model. This signature was validated for its use in routine using Parallel Reaction Monitoring on two different instruments. Linearity and reproducibility of the method were demonstrated as well as its accuracy on donor specimens. Within 4h and without bacterial culture, our method was able to predict the predominant bacteria infecting a sample in 97% of cases and 100% above the standard threshold. This work demonstrates the efficiency of our method for the rapid and specific identification of the bacterial species causing UTI and could be extended in the future to other biological specimens and to bacteria having specific virulence or resistance factors.

Sensitive electrochemiluminescence (ECL) immunoassays for detecting lipoarabinomannan (LAM) and ESAT-6 in urine and serum from tuberculosis patients

BACKGROUND

Tuberculosis (TB) infection was responsible for an estimated 1.3 million deaths in 2017. Better diagnostic tools are urgently needed. We sought to determine whether accurate TB antigen detection in blood or urine has the potential to meet the WHO target product profiles for detection of active TB.

MATERIALS AND METHODS

We developed Electrochemiluminescence (ECL) immunoassays for Lipoarabinomannan (LAM) and ESAT-6 detection with detection limits in the pg/ml range and used them to compare the concentrations of the two antigens in the urine and serum of 81 HIV-negative and -positive individuals with presumptive TB enrolled across diverse geographic sites.

RESULTS

LAM and ESAT-6 overall sensitivities in urine were 93% and 65% respectively. LAM and ESAT-6 overall sensitivities in serum were 55% and 46% respectively. Overall specificity was ≥97% in all assays. Sensitivities were higher in HIV-positive compared to HIV-negative patients for both antigens and both sample types, with signals roughly 10-fold higher on average in urine than in serum. The two antigens showed similar concentration ranges within the same sample type and correlated.

CONCLUSIONS

LAM and ESAT-6 can be detected in the urine and serum of TB patients, regardless of the HIV status and further gains in clinical sensitivity may be achievable through assay and reagent optimization. Accuracy in urine was higher with current methods and has the potential to meet the WHO accuracy target if the findings can be transferred to a point-of-care TB test.

Prospective study of canine leptospirosis in shelter and stray dog populations: Identification of chronic carriers and different Leptospira species infecting dogs

Dogs are highly susceptible to the leptospiral infection, notably stray and sheltered dogs. Unsanitary conditions often observed in dog shelters may predispose the introduction and spread of leptospires among sheltered populations, potentially increasing the chances for the inadvertent adoption of asymptomatically infected animals. The present work describes a longitudinal study using a multidisciplinary approach for the identification of chronically infected dogs and the characterization of potentially pathogenic strains circulating among stray and sheltered dog populations in São Paulo, Brazil. A total of 123 dogs from three populations were included. The initial evaluation consisted of blood and urine quantitative PCR testing (qPCR), the detection of specific antibodies by microscopic agglutination test (MAT), physical examination and hematological and serum biochemistry analyses. The qPCR-positive dogs were prospectively examined, and reevaluations also included culture from urine samples. Positive qPCR samples were subjected to 16S rRNA and secY gene phylogenetic analysis. The recovered strains were characterized by Multilocus Sequence Typing, polyclonal serogroup identification and virulence determination. Leptospiruria was detected in all populations studied (13/123), and phylogenetic analysis revealed that 10 dogs had L. interrogans infection. Three dogs (3/13) had L. santarosai infection. The secY phylogenetic analysis revealed that the L. santarosai sequences clustered separately from those obtained from other hosts. Ten leptospiruric dogs were reevaluated, and three dogs presented persistent leptospiruria, allowing culturing from two dogs. The strains were characterized as L. interrogans serogroup Canicola (virulent) and L. santarosai serogroup Sejroe (not virulent). Serum samples were retested by MAT using the DU92 and DU114 strains as antigens, and no increased seroreactivity was detected. Asymptomatic L. santarosai infection was observed in all populations studied, suggesting a possible role of dogs in the chain of transmission of this leptospiral species. The results suggest a genetic distinction between lineages of Brazilian L. santarosai maintained by dogs and other animal hosts. Our findings revealed that dogs could act as maintenance hosts for distinct pathogenic Leptospira, highlighting also that asymptomatically infected dogs can be inadvertently admitted and adopted in dog shelters, potentially increasing the risks of zoonotic transmission.

Pathogen-specific leptospiral proteins in urine of patients with febrile illness aids in differential diagnosis of leptospirosis from dengue

Leptospirosis and dengue are two commonly seen infectious diseases of the tropics. Differential diagnosis of leptospirosis from dengue fever is often difficult due to overlapping clinical symptoms and lack of economically viable and easy-to-perform laboratory tests. The gold standard for diagnosis is the microscopic agglutination test (MAT). In this study, the diagnostic potential of screening for pathogen-specific leptospiral antigens in urine samples is presented as a non-invasive method of disease diagnosis. In a study group of 40 patients, the serum was tested for anti-leptospiral antibodies by MAT and enzyme-linked immunosorbent assay (ELISA). Urine of these patients was screened for leptospiral antigens by ELISA using specific antibodies against LipL32, LipL41, Fla1, HbpA and sphingomyelinase. Group I patients (n = 23) were classified as leptospirosis-positive based on MAT and high titres of circulating IgM-specific anti-leptospiral antibodies. All of these patients excreted all five leptospiral antigens in the urine. The 17 MAT-negative cases included six patients with pyrexia of unknown origin (PUO; Group II) and 11 confirmed dengue patients (Group III). The latter tested negative for both serum anti-leptospiral antibodies and urinary leptospiral antigens. A salient outcome of this study was highlighting the usefulness of screening for urinary leptospiral antigens in disease diagnosis, as their presence confirmed leptospiral aetiology in two PUO patients. Immunoblots of urinary antigens identified well-defined bands corresponding to LipL32, HbpA and sphingomyelinase; the significance of the 42- and 58-kDa sphingomyelinase bands is discussed.

Discovery of a unique Mycobacterium tuberculosis protein through proteomic analysis of urine from patients with active tuberculosis

Identification of pathogen-specific biomarkers present in patients' serum or urine samples can be a useful diagnostic approach. In efforts to discover Mycobacterium tuberculosis (Mtb) biomarkers we identified by mass spectroscopy a unique 21-mer Mtb peptide sequence (VVLGLTVPGGVELLPGVALPR) present in the urines of TB patients from Zimbabwe. This peptide has 100% sequence homology with the protein TBCG_03312 from the C strain of Mtb (a clinical isolate identified in New York, NY, USA) and 95% sequence homology with Mtb oxidoreductase (MRGA423_21210) from the clinical isolate MTB423 (identified in Kerala, India). Alignment of the genes coding for these proteins show an insertion point mutation relative to Rv3368c of the reference H37Rv strain, which generated a unique C-terminus with no sequence homology with any other described protein. Phylogenetic analysis utilizing public sequence data shows that the insertion mutation is apparently a rare event. However, sera from TB patients from distinct geographical areas of the world (Peru, Vietnam, and South Africa) contain antibodies that recognize a purified recombinant C-terminus of the protein, thus suggesting a wider distribution of isolates that produce this protein.

[Characteristic of virulence potential of clinical isolates of enterococci]

AIM

Determination of virulence of enterococci strains isolated from clinical material from humans on pheno- and genotype levels.

MATERIALS AND METHODS

30 strains of enterococci isolated from wound exudate, urine, newborn skin lavage were used in the study. Strain identification was carried out by multiplex PCR. Hemolytic activity was determined by dish method, gelatinase - by dissolution of gelatin column, proteolytic--by biuret method; genes coding virulence factor synthesis (gelE, sprE, cylM, cylB, cylA, cylLs, cylL1, ESP, HYL, ASA)--by using PCR.

RESULTS

Clinical isolates of enterococci were assigned to E. faecalis and E. faecium species. Virulence factors on phenotype and genotype levels were detected in both species.

CONCLUSION

Genetic determinants of virulence are more widespread among clinical isolates of E.faecalis species. Set of genes coding virulence factors in E. faecalis depends on biotope. Gene coding hyaluronidase synthesis is characteristic for E. faecium. A correlation between phenotypic manifestation of features and enterococci genotype was detected.

Performance of a pneumolysin enzyme-linked immunosorbent assay for diagnosis of pneumococcal infections

A pneumolysin-specific enzyme-linked immunosorbent assay (PLY-ELISA) for the detection of pneumolysin in urine was developed and evaluated in comparison with the commercially available Binax Now Streptococcus pneumoniae test (Binax, Portland, ME) for the diagnosis of pneumococcal infections. Assay sensitivity was evaluated using urine from 108 patients with culture-confirmed pneumococcal infections. In adults, the sensitivity and specificity of the PLY-ELISA were 56.6% and 92.2%, respectively. In children with nasopharyngeal pneumococcal carriage, PLY-ELISA and Binax Now S. pneumoniae test sensitivities were 62.5% and 87.5%, respectively, while specificities were 94.4% and 27.8%, respectively. In children with nonnasopharyngeal pneumococcal carriage, PLY-ELISA and Binax Now S. pneumoniae test sensitivities were 68.7% and 93.7%, respectively, and test specificities were 94.1% and 41.2%, respectively. The persistence of pneumolysin in urine of pneumococcal pneumonia patients decreased significantly after 4 to 6 days of treatment. Our data suggest that combining the high specificity of the PLY-ELISA with the high sensitivity of the Binax Now S. pneumoniae test would enable pneumococcal infections to be accurately diagnosed in children.

Cloning of the gene encoding a protective Mycobacterium tuberculosis secreted protein detected in vivo during the initial phases of the infectious process

The existence of therapeutic agents and the bacille Calmette-Guérin (BCG) vaccine have not significantly affected the current tuberculosis pandemic. BCG vaccine protects against serious pediatric forms of tuberculosis but not against adult pulmonary tuberculosis, the most common and contagious form of the disease. Several vaccine candidates, including Mycobacterium tuberculosis recombinant proteins formulated in newer adjuvants or delivered in bacterial plasmid DNA have recently been described. An attractive source of vaccine candidates has been M. tuberculosis Ags present in culture supernatants of the initial phases of the bacterial growth in vitro. In this study we describe an Ag discovery approach to select for such Ags produced in vivo during the initial phases of the infection. We combined RP-HPLC and mass spectrometry to identify secreted or shed M. tuberculosis proteins eliminated in animal urine within 14 days after the infection. A peptide containing sequence homology with a hypothetical M. tuberculosis protein was identified and the recombinant protein produced in Escherichia coli. The protein was recognized by Ab (IgG2a and IgG1) and T cells (Th1) of mice infected with M. tuberculosis and by lymphoid cells from healthy donors who had a positive purified protein derivative skin test but not from tuberculosis patients. Moreover, this Ag induced protection in mice against M. tuberculosis at levels comparable to protection induced by BCG vaccine. These results validate the Ag discovery approach of M. tuberculosis proteins secreted or shed in vivo during the early phases of the infection and open new possibilities for the development of potential vaccine candidates or of markers of active mycobacterial multiplication and therefore active disease.

Evaluation of a standardized F1 capsular antigen capture ELISA test kit for the rapid diagnosis of plague

Rapid detection of soluble F1 capsular antigen in serum, bubo fluid or urine of patients proved to be a valuable tool in the presumptive diagnosis of plague. We evaluated a F1 capsular antigen capture ELISA resembling a commercially available test kit. The minimal detectable concentration was 4 ng/ml. The specificity was 100% when investigating 47 sera from healthy Malagasy subjects and 98.4% when 365 sera from German blood donors were studied. Sensitivity was determined on sera (n=11) and buboes (n=18) from bacteriologically confirmed Malagasy plague patients. Sensitivity was 90.1% for serum and 100% for buboes. A standardized F1 capsular antigen capture ELISA test kit might be well suited for the early detection of plague particularly in non-endemic areas where clinical microbiological laboratories have only limited access to alternative techniques for rapid identification of Yersinia pestis.

Potential serological use of a recombinant protein that is a replica of a Mycobacterium tuberculosis protein found in the urine of infected mice

The recent availability of numerous well-characterized Mycobacterium tuberculosis recombinant proteins has revived interest in the serological diagnosis of tuberculosis. Several promising results have been reported, particularly when more than one antigen is used in the test. However, thus far these antigens have not been used in routine diagnostic tests because they lack sufficient sensitivity. In addition, with the exception of one antigen, most recombinant M. tuberculosis proteins do not identify the majority of tuberculosis patients coinfected with human immunodeficiency virus (HIV). Here, we report a newer M. tuberculosis protein that is a promising candidate for increasing the sensitivity of the serological tests, in particular for patients coinfected with HIV. The protein was found in the urine of mice during the early stages of infection with M. tuberculosis (10 to 14 days), thus suggesting that the antigen is abundantly released during the in vivo growth of the mycobacterium. Reverse genetics was used to produce the recombinant protein, which we named U1 (for urine protein 1). Using a conventional enzyme-linked immunosorbent assay (ELISA), antibody to U1 could be detected in 60% of patients with pulmonary tuberculosis with no signs of coinfection with HIV (n = 83). Conversely, anti-U1 antibody was detected in 87% of the sera from tuberculosis patients coinfected with HIV (n = 47). Out of 12 HIV-infected nontuberculosis patients' sera, 9 did not react with U1 and three sera gave borderline ELISA signals (signal/cutoff of < or =1.75). These results suggest that the high efficiency of U1 in identifying tuberculosis patients coinfected with HIV may be related to abundant release of this protein during the initial phase of the HIV coinfection. The immediate availability of the antigen at a time point in which the patient's immune system is still competent would lead to a secondary immune response to U1 that persists for months in the patient's serum.

Early diagnosis of bubonic plague using F1 antigen capture ELISA assay and rapid immunogold dipstick

Plague is still prevalent in more than 20 countries. Two F1 antigen diagnostic assays (an immunocapture ELISA and an immunogold chromatography dipstick) were evaluated using bubo aspirates, serum and urine specimens from patients suspected with plague. The specificity of the two F1 assays was found 100%. Using bacteriology as a gold reference diagnostic assay, 52 patients were Yersinia pestis culture positive and 141 negative. The sensitivity of the F1 ELISA test was 100% in bubo, 52% in serum and 58% in urine specimens. In culture negative patients, the F1 antigen could be found in 10% bubo aspirates, 5% serum and 7% urine specimens of culture negative patients for whom a seroconversion for anti-F1 antibodies was also observed. The sensitivity of the dipstick assay was 98% on bubo aspirates specimens. Compared to the ELISA test, the agreement rate was 97.5% and the correlation coefficient tau = 0.90 (p < 10(-3)). In conclusion, the diagnosis of bubonic plague has to be performed on bubo fluid rather than on serum or urine specimens. Both the F1 ELISA and the dipstick assays are valuable tools for an early diagnosis and for the surveillance of plague.

Histological and subcellular distribution of 65 and 70 kD heat shock proteins in experimental nephrotoxic injury

The cellular distribution of 65 and 70 kD heat shock proteins (HSPs) was studied in the normal rat kidney and after acute tubular necrosis (ATN) induced by inorganic mercury (HgCl2). In the normal kidney the 65 kD HSP was found in the cytoplasm of podocytes and proximal convoluted tubules, whereas the 70 kD HSP was located in nuclei and cytoplasm of podocytes, cortical convoluted, and collecting tubules. The distribution of both HSPs along ATN changed as a function of time. In the early phase, before evidence of histological damage, both HSPs were found in the pielocaly ceal epithelium and medullary collecting tubules. During the necrotic phase, HSPs coexisted with sites of severe damage (i.e. cortical tubules). With immunoelectron microscopy damaged cells showed an abundance of 65 kD HSP-I in mitochondria, as well as in chromatin and nucleoli, while 70 kD HSP-I was overexpressed in the cytoplasm, mito chondria, lysosomes, cytoskeleton, chromatin, and nucleoli, and coincided with urinary excretion of HSPs. In the postregenerative phase, the distribution of HSPs was similar to that found in the normal kidney. HSPs of 65 and 70 kD were encountered constitutionally and their immunolabeling is correlated with the magnitude of cell injury.

Distribution of virulence factors in Escherichia coli isolated from urine of cystitis patients

The distribution of 7 urovirulence factors, such as type 1 pilus (pil), pilus associated with pyelonephritis (pap), S fimbriae (sfa), afimbrial adhesin I (afaI), hemolysin (hly), aerobactin (aer) and cytotoxic necrotizing factor 1 (cnf1) was examined by a DNA colony hybridization test among 194 Escherichia coli strains isolated from the urine of cystitis patients and in 80 strains isolated from the stool specimens of healthy adults. All virulence factors examined, except pil, were significantly more frequently detected among the cystitis isolates than among the fecal isolates. When individual virulence factors were analyzed against the others, an association was discernible which was not apparent when all 7 virulence factors were considered collectively. There was an apparent correlation between the genotypes and serotypes of the E. coli strains from the cystitis patients. From the data presented, it was proposed that genetic detection of virulence factors would be useful for rapid diagnosis of cystitis, especially in patients without severe pyuria or bacteriuria.

Production and purification of Escherichia coli hemolysin

Eight strains of Escherichia coli, isolated from patients with a urinary tract infection were investigated for production of hemolysin. Six of these produced hemolysin and one revealed maximum hemolytic activity. Three urinary and two faecal isolates were positive for mannose-resistant hemagglutination. One isolate positive for hemagglutination and giving maximum hemolytic activity was then used. Hemolysin was present in the supernatant broth and the medium of choice to obtain the optimum yield was the alkaline meat extract broth followed by brain heart infusion broth. The highest yield appeared in the exponential phase of growth. Hemolysin is a heat-labile protein, being produced optimally at pH 8. A three-stage procedure was the best method for its purification.

Protein G: a powerful tool for binding and detection of monoclonal and polyclonal antibodies

Protein G is an immunoglobulin (IgG)-binding bacterial cell wall protein recently isolated from group G streptococci. We have investigated the avidity of protein G for various monoclonal and polyclonal Ig of the IgG class, and compared it with the binding properties of protein A, the staphylococcal Fc-binding protein. Radiolabeled Ig were mixed with Sepharose-coupled protein G or protein A, and the amounts of radioactivity bound to the matrix-coupled bacterial proteins were determined. The avidity was found to be greater for protein G than for protein A for all examined Ig. Protein G bound all tested monoclonal IgG from mouse IgG1, IgG2a, and IgG3, and rat IgG2a, IgG2b, and IgG2c. In addition, polyclonal IgG from man, cow, rabbit, goat, rat, and mouse bound to protein G, whereas chicken IgG did not. The binding property of protein G was additionally exploited in the Western blot assay, in which iodine-labeled protein G was used successfully for the detection of a rat monoclonal antibody against ovalbumin, and for the detection of rabbit and goat polyclonal whole antisera against human urinary proteins. In these experimental situations, protein G was found to be a powerful reagent for the detection of IgG, and consequently the antigen against which these antibodies are directed.