A Rapid, High-Throughput Viability Assay for<i>Blastocystis</i>spp. Reveals Metronidazole Resistance and Extensive Subtype-Dependent Variations in Drug Susceptibilities

Mirza, Haris; Teo, Joshua D. W.; Upcroft, Jacqueline; Tan, Kevin S. W.

doi:10.1128/aac.00900-10

Cited by 74 publications

(89 citation statements)

References 63 publications

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“…On the other hand, ST7-B is relatively resistant to LL-37 and is also rare in terms of being detected in human populations. This ST is also resistant to a number of drugs, including metronidazole (13,48), and is capable of downregulating the expression of nitric oxide synthase (14), which is an essential element in the innate immune response. Isolates of ST7 have also been found to cause epithelial barrier disruption and have more adhesive properties in cell cultures (49), thereby making this ST potentially more pathogenic than the rest of the STs.…”

Section: Discussionmentioning

confidence: 99%

Blastocystis Isolate B Exhibits Multiple Modes of Resistance against Antimicrobial Peptide LL-37

2016

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Blastocystis is one of the most common eukaryotic organisms found in humans and many types of animals. Several reports have identified its role in gastrointestinal disorders, although its pathogenicity is yet to be clarified. Blastocystis is transmitted via the fecal-to-oral route and colonizes the large intestines. Epithelial cells lining the intestine secrete antimicrobial peptides (AMPs), including beta-defensins and cathelicidin, as a response to infection. This study explores the effects of host colonic antimicrobial peptides, particularly LL-37, a fragment of cathelicidin, on different Blastocystis subtypes. Blastocystis is composed of several subtypes that have genetic, metabolic, and biological differences. These subtypes also have various outcomes in terms of drug treatment and immune response. In this study, Blastocystis isolates from three different subtypes were found to induce intestinal epithelial cells to secrete LL-37. We also show that among the antimicrobial peptides tested, only LL-37 has broad activity on all the subtypes. LL-37 causes membrane disruption and causes Blastocystis to change shape. Blastocystis subtype 7 (ST7), however, showed relative resistance to LL-37. An isolate, ST7 isolate B (ST7-B), from this subtype releases proteases that can degrade the peptide. It also makes the environment acidic, which causes attenuation of LL-37 activity. The Blastocystis ST7-B isolate was also observed to have a thicker surface coat, which may protect the parasite from direct killing by LL-37. This study determined the effects of LL-37 on different Blastocystis isolates and indicates that AMPs have significant roles in Blastocystis infections. Blastocystis is an intestinal protistan parasite commonly detected in humans and many types of animals (1, 2). This organism is classified under the stramenopiles, although it lacks chloroplasts or structures for locomotion, which are common features of many members of this group. Blastocystis is widely distributed throughout the world. Parasitological surveys usually place Blastocystis as the most common eukaryotic parasite detected (3,4). This organism has a global distribution and has numerous animal hosts. There is little host specificity for this organism, and there are reports indicating the zoonotic potential of Blastocystis (5). This organism, in its cyst form, is transmitted via the fecal-tooral route. It then colonizes the large intestine and is excysted to its various forms. These forms may appear vacuolar, multivacuolar, avacuolar, or granular under a light microscope. Blastocystis has been implicated in a number of intestinal disorders, although its pathogenesis is yet to be elucidated. There are few reports associating it with gastrointestinal disease, the most common symptoms of which are diarrhea, vomiting, nausea, and urticaria (1, 5-7). Blastocystis is a species complex that is comprised of up to 19 subtypes (STs), with ST1 to ST9 having been isolated from humans (8). Recently, a report found that ST12 and another possible novel ST also in...

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Section: Discussionmentioning

confidence: 99%

Blastocystis Isolate B Exhibits Multiple Modes of Resistance against Antimicrobial Peptide LL-37

2016

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“…It is certainly not surprising that subtypes differ in their susceptibility to drugs, given the large genetic differences that exist between them (Mirza et al, 2011), and in vitro drug resistance has been generated successfully in the laboratory (Dunn et al, 2012).…”

Section: Case Studiesmentioning

confidence: 99%

Recent Developments in Blastocystis Research

Clark

Giezen

Alfellani

et al. 2013

Advances in Parasitology

251

216

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Abstract:Blastocystis is a common parasite of the human large intestine but has an uncertain role in disease. In this review, we appraise the published evidence addressing this and its weaknesses. Genetic diversity studies have led to the identification of numerous subtypes within the genus Blastocystis and, recently, methods for studying variation within subtypes have been developed, with implications for our understanding of host specificity. The geographic distribution of subtypes is summarised and the impact this may have on investigations into the role of the organism in disease is discussed. Finally, we describe the organelle and nuclear genome characteristics and look to future developments in the field.

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“…Clinical (39) as well as in vitro (26) and in vivo (12,13) studies suggest strain-to-strain variations in Blastocystis pathogenicity as well as antibiotic susceptibility (27). Variations in pathogenicity of the parasite strains are often proposed as a possible explanation for the large number of asymptomatic Blastocystis infections (42).…”

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confidence: 99%

A Metronidazole-Resistant Isolate of Blastocystis spp. Is Susceptible to Nitric Oxide and Downregulates Intestinal Epithelial Inducible Nitric Oxide Synthase by a Novel Parasite Survival Mechanism

et al. 2011

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Blastocystis, one of the most common parasites colonizing the human intestine, is an extracellular, noninvasive, luminal protozoan with controversial pathogenesis. Blastocystis infections can be asymptomatic or cause intestinal symptoms of vomiting, diarrhea, and abdominal pain. Although chronic infections are frequently reported, Blastocystis infections have also been reported to be self-limiting in immunocompetent patients. Characterizing the host innate response to Blastocystis would lead to a better understanding of the parasite's pathogenesis. Intestinal epithelial cells produce nitric oxide (NO), primarily on the apical side, in order to target luminal pathogens. In this study, we show that NO production by intestinal cells may be a host defense mechanism against Blastocystis. Two clinically relevant isolates of Blastocystis, ST-7 (B) and ST-4 (WR-1), were found to be susceptible to a range of NO donors. ST-7 (B), a metronidazole-resistant isolate, was found to be more sensitive to nitrosative stress. Using the Caco-2 model of human intestinal epithelium, Blastocystis ST-7 (B) but not ST-4 (WR-1) exhibited dose-dependent inhibition of Caco-2 NO production, and this was associated with downregulation of inducible nitric oxide synthase (iNOS). Despite its higher susceptibility to NO, Blastocystis ST-7 (B) may have evolved unique strategies to evade this potential host defense by depressing host NO production. This is the first study to highlight a strain-to-strain variation in the ability of Blastocystis to evade the host antiparasitic NO response.Blastocystis is an extracellular and noninvasive unicellular enteric parasite with zoonotic potential (28,41,42). It is among the most common parasites found in the human intestine, with prevalence ranging between 10% of the population in developed countries and 50% in developing countries (42). It is a species complex belonging to the Stramenopile group. According to a recent classification, it is divided into 11 subtypes, 9 of which are known to infect humans. Other common hosts are chickens, rats, pigs, reptiles, and insects (41). Despite recent advances in our understanding of the parasite's classification and pathobiology, several questions concerning the parasite's biology remain unanswered. The parasite's pathogenicity is also controversial owing to asymptomatic carriage, coinfection with other pathogens, and nonresponsiveness to conventional chemotherapeutic agents.Blastocystis infections or blastocystosis present with common intestinal symptoms, such as abdominal pain, vomiting, and bloating, as well as mucous and watery diarrhea (42). Dermatological disorders (15,45) and irritable bowel syndrome (39) are also frequently associated with Blastocystis infections. It is transmitted through the feco-oral route, and metronidazole is the treatment of choice for Blastocystis infections. The parasite has a high prevalence in immunocompromised individuals (17,29,43). In immunocompetent individuals, Blastocystis infections are often asymptomatic (7, 39) or self-limi...

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A Rapid, High-Throughput Viability Assay forBlastocystisspp. Reveals Metronidazole Resistance and Extensive Subtype-Dependent Variations in Drug Susceptibilities

Cited by 74 publications

References 63 publications

Blastocystis Isolate B Exhibits Multiple Modes of Resistance against Antimicrobial Peptide LL-37

Blastocystis Isolate B Exhibits Multiple Modes of Resistance against Antimicrobial Peptide LL-37

Recent Developments in Blastocystis Research

A Metronidazole-Resistant Isolate of Blastocystis spp. Is Susceptible to Nitric Oxide and Downregulates Intestinal Epithelial Inducible Nitric Oxide Synthase by a Novel Parasite Survival Mechanism

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