Optimization of a flow cytometry protocol for detection and viability assessment of Giardia lamblia

Prevalence and genetic diversity of Giardia duodenalis in pet dogs from Zhengzhou, central China and the association between gut microbiota and fecal characteristics during infection

As a common zoonotic intestinal parasite, Giardia duodenalis could infect humans and various mammals worldwide, including pet dogs, leading to giardiasis. This study detected the infection of G. duodenalis in asymptomatic pet dogs in Zhengzhou, and evaluated the possibility of zoonosis and the relationship between gut microbiota and fecal characteristics. We randomly collected 448 fresh fecal samples from Zhengzhou, and G. duodenalis was screened based on the beta-giardin (bg), glutamate dehydrogenase (gdh), and triose phosphate isomerase (tpi) genes. The difference of gut microbiota between five G. duodenalis-positive and five G. duodenalis-negative samples was investigated by 16S rRNA gene sequencing. The overall prevalence of G. duodenalis was 7.1% (32/448) based on bg, gdh, and tpi locus, two G. duodenalis assemblages (C = 13, D = 14) and five (15.6%) mixed infection (C + D) were identified. Moreover, compared with the G. duodenalis-negative group, the diversity of gut microbiota increased in G. duodenalis-positive group. The decrease of Lactobacillus spp. and considerable increase of Prevotella spp. were associated with the fecal characteristics. These results show that the transmission of zoonotic giardiasis between humans and pet dogs is rare in Zhengzhou, central China, and support the use of Lactobacillus spp. as a potential probiotic agent to improve intestinal health in dogs, or even humans, by treating G. duodenalis. Therefore, the public health significance of G. duodenalis to humans, companion animals, and the environment should be further evaluated from One Health perspective.

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Prevalence of G. duodenalis was 7.1% in pet dogs in Zhengzhou, central China.

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G. duodenalis assemblage D infection is associated to higher gut microbial diversity.

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The abundance of Prevotella and Lactobacillus may affect fecal characteristics.

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Lactobacillus may be used as a potential feed additive to treat giardiasis.

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Effective strategies should be taken to minimize the threat posed by G. duodenalis.

Asymptomatic Effluent Protozoa Colonization in Peritoneal Dialysis Patients

Currently, chronic kidney disease (CKD) is a global health problem. Considering the impaired immunity of CKD patients, the relevance of infection in peritoneal dialysis (PD), and the increased prevalence of parasites in CKD patients, protozoa colonization was evaluated in PD effluent from CKD patients undergoing PD. Overnight PD effluent was obtained from 49 asymptomatic stable PD patients. Protozoa analysis was performed microscopically by searching cysts and trophozoites in direct wet mount of PD effluent and after staining smears. Protozoa were found in PD effluent of 10.2% of evaluated PD patients, namely Blastocystis hominis, in 2 patients, and Entamoeba sp., Giardia sp., and Endolimax nana in the other 3 patients, respectively. None of these patients presented clinical signs or symptoms of peritonitis at the time of protozoa screening. Our results demonstrate that PD effluent may be susceptible to asymptomatic protozoa colonization. The clinical impact of this finding should be further investigated.

Occurency of Giardia duodenalis assemblages in river water sources of Black Sea, Turkey

A total of 420 environmental water samples and 120 drinking water samples from 45 different sampling sites of the Black Sea in Turkey were collected between 2012 and 2014. Genomic DNA was isolated from all the investigated water samples and comparativelly analyzed by Loop-mediated isothermal amplification (LAMP) of the elongation factor 1 Alfa (EF1α) gene, and by nested Polymerase Chain Reaction (nPCR) of the small subunit (SSU) rRNA and semi-nested PCR (snPCR) of the glutamate dehydrogenase gene (GDH). 141 (58.7%), 125 (52.1%) and 120 (50%) samples respectivelly were positive by each method. Out of 240 environmental samples collected from 25 sites of Samsun Province have been found positive for G. duodenalis by LAMP, nPCR and snPCR, respectively. 55 (30.5%), 50 (27.8%) and 47 (26.1%) of 180 environmental samples collected from 20 other sampling sites of Giresun Province were positive for Giardia by LAMP, nPCR and snPCR, respectively. Five PCR products from different samples of the Giresun Province and 10 other samples from the Samsun Province were found positive for G. duodenalis assemblage B. Five PCR products from Giresun Province and 5 samples from Samsun Province were found positive for G. duodenalis assemblage A. This is the first report about G. duodenalis assemblages A and B from water samples investigations in Black Sea of Turkey.

Deconjugated Bile Salts Produced by Extracellular Bile-Salt Hydrolase-Like Activities from the Probiotic Lactobacillus johnsonii La1 Inhibit Giardia duodenalis In vitro Growth

Giardiasis, currently considered a neglected disease, is caused by the intestinal protozoan parasite Giardia duodenalis and is widely spread in human as well as domestic and wild animals. The lack of appropriate medications and the spread of resistant parasite strains urgently call for the development of novel therapeutic strategies. Host microbiota or certain probiotic strains have the capacity to provide some protection against giardiasis. By combining biological and biochemical approaches, we have been able to decipher a molecular mechanism used by the probiotic strain Lactobacillus johnsonii La1 to prevent Giardia growth in vitro. We provide evidence that the supernatant of this strain contains active principle(s) not directly toxic to Giardia but able to convert non-toxic components of bile into components highly toxic to Giardia. By using bile acid profiling, these components were identified as deconjugated bile-salts. A bacterial bile-salt-hydrolase of commercial origin was able to mimic the properties of the supernatant. Mass spectrometric analysis of the bacterial supernatant identified two of the three bile-salt-hydrolases encoded in the genome of this probiotic strain. These observations document a possible mechanism by which L. johnsonii La1, by secreting, or releasing BSH-like activity(ies) in the vicinity of replicating Giardia in an environment where bile is present and abundant, can fight this parasite. This discovery has both fundamental and applied outcomes to fight giardiasis, based on local delivery of deconjugated bile salts, enzyme deconjugation of bile components, or natural or recombinant probiotic strains that secrete or release such deconjugating activities in a compartment where both bile salts and Giardia are present.

Evaluation of Giardia duodenalis viability after metronidazole treatment by flow cytometry

Giardia duodenalis (syn. lamblia; syn. intestinalis) susceptibility testing is not routinely performed because the classical culture methods are very time-consuming and laborious. We developed a novel flow cytometry (FC) assay to evaluate the susceptibility of G. duodenalis trophozoites to metronidazole (MTZ). Different concentrations of MTZ were added to cultures of trophozoites (10 5 /mL) and the cultures were incubated for different periods. The 50% inhibitory concentration was calculated and propidium iodide (PI) was used to quantify the number of dead cells. After treatment, PI-positive trophozoites increased with increasing drug concentration and exposure time. An excellent correlation was found between FC and the classical method. A novel, accurate and reliable method is now available to evaluate G. duodenalis viability.

Specific detection of Pneumocystis jirovecii in clinical samples by flow cytometry

Pneumocystis jirovecii is an opportunistic pathogen responsible for severe pneumonia in immunocompromised patients. Flow cytometry (FC) is a method widely used in different areas of clinical diagnosis like hematology and immunology. Recently it has started to be used in microbiology with a great potential for diagnosis of emergent microorganisms in clinical samples, especially when present in low numbers. The detection of Pneumocystis jirovecii in respiratory samples can be performed by FC, using specific monoclonal antibodies. Considering clinical diagnosis as a reference method, we previously showed FC to be 100% sensitive and specific when compared to immunofluorescence. Being an automated method, it is faster and less subject to human error than microscopic evaluation.

A novel flow cytometric assay for rapid detection of extended-spectrum beta-lactamases

The rapid detection of extended-spectrum beta-lactamases (ESBLs) is a challenge for most clinical microbiology laboratories because inaccurate identification of ESBL producers has important clinical implications for both antibiotic treatment and infection control. The aim of our study was to develop a rapid detection assay of ESBL producers based upon flow cytometric analysis. Antimicrobial susceptibility testing followed by molecular characterization of bla(TEM) , bla(SHV) or bla(CTX-M) genes was performed on clinical isolates (41 ESBL positive and 20 ESBL negative) and isolates expressing well-characterized beta-lactamases, including ESBLs (n = 13), plasmid AmpCs (n = 3), oxacillinases (n = 5) and carbapenemases (n = 3). Additionally, two ATCC strains recommended by CLSI for susceptibility testing were used as controls. The flow cytometry analysis protocol involved an incubation of bacterial cells with different concentrations of ceftazidime (1, 2 and 4 mg/L) and cefotaxime (4, 8 and 16 mg/L) for 1 and 2 hours, in the presence and absence of clavulanic acid; subsequently, cells were stained with the fluorescent dye Bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC(4) (3)], a lipophilic anion able to diffuse across depolarized membranes. Additionally, CFU counts were performed. Susceptible isolates displayed increased fluorescence after 1 hour of incubation; conversely, the increase of the depolarized population was only observed after incubation with clavulanic acid associated with ceftazidime or cefotaxime in ESBL producers. An excellent correlation was obtained between the number of non-depolarized bacteria quantified by flow cytometry and by conventional CFU assays. A novel, accurate and fast flow cytometric assay is available to detect the presence of ESBLs.

Detection of Legionella pneumophila on clinical samples and susceptibility assessment by flow cytometry

Culture in selective media represents the standard diagnostic method to confirm Legionella pneumophila infection, despite requiring a prolonged incubation period; antigen detection by immunofluorescence (IFS) and molecular techniques are also available, but they do not allow antimicrobial susceptibility evaluation. Our objective was to optimise flow cytometry (FC) protocols for the detection of L. pneumophila in respiratory samples and for susceptibility evaluation to first-line drugs. In order to optimise the FC protocol, a specific monoclonal antibody, conjugated with fluorescein isothiocyanate (FITC), was incubated with type strain L. pneumophila ATCC 33152. The limit of detection was established by analysing serial dilutions of bacterial suspension; specificity was assayed using mixtures of prokaryotic and eukaryotic microorganisms. The optimised FC protocol was used to assess 50 respiratory samples and compared with IFS evaluation. The susceptibility profile to erythromycin, ciprofloxacin and levofloxacin was evaluated by FC using propidium iodide and SYBR Green fluorescent dyes; the results were compared with the Etest afterwards. The optimal specific antibody concentration was 20 μg/ml; 10(2)/ml Legionella organisms were detected by this protocol and no cross-reactions with other microorganisms were detected. The five positive respiratory samples (10 %) determined by IFS were also detected by FC, showing 100 % correlation. After 1 h of incubation at 37 °C with different antimicrobials, SYBR Green staining could discriminate between treated and non-treated cells. A novel flow cytometric approach for the detection of L. pneumophila from clinical samples and susceptibility evaluation is now available, representing an important step forward for the diagnosis of this very relevant agent.

ECC-RT-PCR: a new method to determine the viability and infectivity of Giardia cysts

BACKGROUND

Giardia sp is a major cause of diarrheal illness worldwide, and millions of people are infected each year. Rapid methods to determine the infectivity and virulence of isolates are critical for the development of intervention strategies to control the transmission of Giardia sp cysts, which occurs through contaminated surfaces, food, and water. However, determining the viability, infectivity, and virulence of Giardia sp cysts using molecular methods is a technical challenge because of the lack of a cell culture model.

METHOD

This study was designed to evaluate mRNA expression in trophozoites and to assess trophozoite attachment to cell monolayer and changes in transcellular resistance as an indicator of Giardia sp viability and infectivity. Heat shock mRNA in Giardia cysts and variant-specific protein (VSP) mRNA in trophozoites were quantified by reverse transcription polymerase chain reaction (RT-PCR). C2bb (Caco-2) cells were grown on transwell chambers to study the attachment of trophozoites, changes in transcellular resistance, and expression of VSP in trophozoites.

RESULTS

The results of these molecular and cell culture studies indicate a direct linear correlation between the viability and infectivity of fresh stocks of Giardia sp cysts. The attachment of trophozoites to cell monolayer, expression of VSP, and change in the transcellular resistance was directly correlated with their infectivity in neonatal mice. PCR was successfully combined with the electrophysiological analysis of cell culture (ECC-RT-PCR) post-trophozoite attachment.

CONCLUSION

This study shows that the ECC-RT-PCR, a new integrated cell culture assay, can be used as a rapid and cost-effective tool for assessing the viability and infectivity of environmental isolates of Giardia sp cysts.

A real-time RT-PCR method to detect viable Giardia lamblia cysts in environmental waters

Currently, USEPA Method 1623 is the standard assay used for simultaneous detection of Giardia cysts and Cryptosporidium oocysts in various water matrices. However, the method is unable to distinguish between species, genotype, or to assess viability. Therefore, the objective of the present study was to address the shortcomings of USEPA Method 1623 by developing a novel molecular-based method that can assess viability of Giardia cysts in environmental waters and identify genotypes that pose a human health threat (assemblage groups A and B). Primers and TaqMan(®) probes were designed to target the beta-giardin gene in order to discriminate among species and assemblages. Viability was determined by detection of de-novo mRNA synthesis after heat induction. The beta-giardin primer/probe sets were able to detect and differentiate between Giardia lamblia assemblages A and B, and did not detect Giardia muris (mouse species) or G. lamblia assemblages C, D, E and F (non-human), with the exception of Probe A which did detect G. lamblia assemblage F DNA. Additionally, DNA or cDNA of other waterborne organisms were not detected, suggesting that the method is specific to Giardia assemblages. Assay applicability was demonstrated by detection of viable G. lamblia cysts in spiked (assemblage B) and unspiked (assemblage A and B) reclaimed water samples.

Evaluation of antifungal susceptibility using flow cytometry

Flow cytometry has found wide applications in areas like haematology and immunology, but also presents great potential in microbiology. The susceptibility of clinical isolates of Candida and Cryptococcus to antifungal compounds can be assayed by flow cytometry using fluorescent probes like FUN-1, propidium iodide and JC-1, with several advantages. Following 1 or 2 h of incubation, depending on the antifungal compound, versus 48 h of the classical methods, it is possible to establish the different susceptibility profiles. Additionally, it provides information regarding the mechanisms of action and might infer about resistance mechanisms.

A new method for the detection of Pneumocystis jirovecii using flow cytometry

Pneumocystis jirovecii is an opportunistic pathogen responsible for severe pneumonia in immunocompromised patients. Its diagnosis has been based upon direct microscopy either by classic staining (Gomori Grocott) or by epifluorescence microscopy (immunofluorescence staining, IFS), both of which are time-consuming and low on sensitivity. Our aim was to develop a flow cytometric (FC) protocol for the detection of P. jirovecii on respiratory samples. In our study, 420 respiratory samples were analysed in parallel by IFS and FC, and compared from clinical diagnosis to its resolution upon specific anti-Pneumocystis therapy. The optimum specific antibody concentration for FC analysis was determined to be 10 microg/ml, without any cross-reactions to bacteria or fungi. All positive cases detected by IFS were positive by FC; however, FC classified eight samples to be positive which were classified as negative by routine technique. These samples were obtained from patients with respiratory symptoms who responded favourably to Pneumocystis-specific therapy and were subsequently considered to be true-positives. Using clinical diagnosis as a reference method, FC showed 100% sensitivity and specificity, whereas IFS showed 90.9% sensitivity and 100% specificity. According to our results, a new diagnostic approach is now available to detect P. jirovecii in respiratory samples.

Cytometric approach for detection of Encephalitozoon intestinalis, an emergent agent

Encephalitozoon intestinalis is responsible for intestinal disease in patients with AIDS and immunocompetent patients. The infectious form is a small spore that is resistant to water treatment procedures. Its detection is very important, but detection is very cumbersome and time-consuming. Our main objective was to develop and optimize a specific flow cytometric (FC) protocol for the detection of E. intestinalis in hospital tap water and human feces. To determine the optimal specific antibody (Microspor-FA) concentration, a known concentration of E. intestinalis spores (Waterborne, Inc.) was suspended in hospital tap water and stool specimens with different concentrations of Microspor-FA, and the tap water and stool specimens were incubated under different conditions. The sensitivity limit and specificity were also evaluated. To study spore infectivity, double staining with propidium iodide (PI) and Microspor-FA was undertaken. Distinct approaches for filtration and centrifugation of the stool specimens were used. E. intestinalis spores stained with 10 microg/ml of Microspor-FA at 25 degrees C overnight provided the best results. The detection limit was 5 x 10(4) spores/ml, and good specificity was demonstrated. Simultaneous staining with Microspor-FA and PI ensured that the E. intestinalis spores were dead and therefore noninfectious. With the stool specimens, better spore recovery was observed with a saturated solution of NaCl and centrifugation at 1,500 x g for 15 min. A new approach for the detection of E. intestinalis from tap water or human feces that ensures that the spores are not viable is now available and represents an important step for the prevention of this threat to public health.