Entamoeba histolytica: A species of parasitic protozoa causing ENTAMOEBIASIS and amebic dysentery (DYSENTERY, AMEBIC). Characteristics include a single nucleus containing a small central karyosome and peripheral chromatin that is finely and regularly beaded.Entamoeba: A genus of ameboid protozoa characterized by the presence of beaded chromatin on the inner surface of the nuclear membrane. Its organisms are parasitic in invertebrates and vertebrates, including humans.Entamoebiasis: Infection with amoebae of the genus ENTAMOEBA. Infection with E. histolytica causes DYSENTERY, AMEBIC and LIVER ABSCESS, AMEBIC.Dysentery, Amebic: DYSENTERY caused by intestinal amebic infection, chiefly with ENTAMOEBA HISTOLYTICA. This condition may be associated with amebic infection of the LIVER and other distant sites.Liver Abscess, Amebic: Single or multiple areas of PUS due to infection by any ameboid protozoa (AMEBIASIS). A common form is caused by the ingestion of ENTAMOEBA HISTOLYTICA.Trophozoites: Cells or feeding stage in the life cycle of sporozoan protozoa. In the malarial parasite, the trophozoite develops from the MEROZOITE and then splits into the SCHIZONT. Trophozoites that are left over from cell division can go on to form gametocytes.Amebicides: Agents which are destructive to amebae, especially the parasitic species causing AMEBIASIS in man and animal.Amebiasis: Infection with any of various amebae. It is an asymptomatic carrier state in most individuals, but diseases ranging from chronic, mild diarrhea to fulminant dysentery may occur.Protozoan Proteins: Proteins found in any species of protozoan.Intestinal Diseases, Parasitic: Infections of the INTESTINES with PARASITES, commonly involving PARASITIC WORMS. Infections with roundworms (NEMATODE INFECTIONS) and tapeworms (CESTODE INFECTIONS) are also known as HELMINTHIASIS.Protozoan Infections: Infections with unicellular organisms formerly members of the subkingdom Protozoa.DNA, Protozoan: Deoxyribonucleic acid that makes up the genetic material of protozoa.Feces: Excrement from the INTESTINES, containing unabsorbed solids, waste products, secretions, and BACTERIA of the DIGESTIVE SYSTEM.Giardia lamblia: A species of parasitic EUKARYOTES that attaches itself to the intestinal mucosa and feeds on mucous secretions. The organism is roughly pear-shaped and motility is somewhat erratic, with a slow oscillation about the long axis.Antigens, Protozoan: Any part or derivative of any protozoan that elicits immunity; malaria (Plasmodium) and trypanosome antigens are presently the most frequently encountered.Genome, Protozoan: The complete genetic complement contained in a set of CHROMOSOMES in a protozoan.Cysteine Proteases: A subclass of peptide hydrolases that depend on a CYSTEINE residue for their activity.Lectins: Proteins that share the common characteristic of binding to carbohydrates. Some ANTIBODIES and carbohydrate-metabolizing proteins (ENZYMES) also bind to carbohydrates, however they are not considered lectins. PLANT LECTINS are carbohydrate-binding proteins that have been primarily identified by their hemagglutinating activity (HEMAGGLUTININS). However, a variety of lectins occur in animal species where they serve diverse array of functions through specific carbohydrate recognition.Genes, Protozoan: The functional hereditary units of protozoa.Acetylgalactosamine: The N-acetyl derivative of galactosamine.Parasitology: The study of parasites and PARASITIC DISEASES.Antibodies, Protozoan: Immunoglobulins produced in a response to PROTOZOAN ANTIGENS.Dientamoeba: A genus of minute EUKARYOTES that are characterized by the preponderance of binucleate over uninucleate forms, the presence of several distinct granules in the karyosome, and the lack of a cystic stage. It is parasitic in the large intestine of humans and certain monkeys.Blastocystis hominis: A species of parasitic protozoa found in the intestines of humans and other primates. It was classified as a yeast in 1912. Over the years, questions arose about this designation. In 1967, many physiological and morphological B. hominis characteristics were reported that fit a protozoan classification. Since that time, other papers have corroborated this work and the organism is now recognized as a protozoan parasite of humans causing intestinal disease with potentially disabling symptoms.Antiprotozoal Agents: Substances that are destructive to protozoans.Gerbillinae: A subfamily of the Muridae consisting of several genera including Gerbillus, Rhombomys, Tatera, Meriones, and Psammomys.Parasites: Invertebrate organisms that live on or in another organism (the host), and benefit at the expense of the other. Traditionally excluded from definition of parasites are pathogenic BACTERIA; FUNGI; VIRUSES; and PLANTS; though they may live parasitically.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Endolimax: A genus of ameboid protozoa found in the intestines of vertebrates and invertebrates.Metronidazole: A nitroimidazole used to treat AMEBIASIS; VAGINITIS; TRICHOMONAS INFECTIONS; GIARDIASIS; ANAEROBIC BACTERIA; and TREPONEMAL INFECTIONS. It has also been proposed as a radiation sensitizer for hypoxic cells. According to the Fourth Annual Report on Carcinogens (NTP 85-002, 1985, p133), this substance may reasonably be anticipated to be a carcinogen (Merck, 11th ed).Giardiasis: An infection of the SMALL INTESTINE caused by the flagellated protozoan GIARDIA LAMBLIA. It is spread via contaminated food and water and by direct person-to-person contact.Giardia: A genus of flagellate intestinal EUKARYOTES parasitic in various vertebrates, including humans. Characteristics include the presence of four pairs of flagella arising from a complicated system of axonemes and cysts that are ellipsoidal to ovoidal in shape.Galactose: An aldohexose that occurs naturally in the D-form in lactose, cerebrosides, gangliosides, and mucoproteins. Deficiency of galactosyl-1-phosphate uridyltransferase (GALACTOSE-1-PHOSPHATE URIDYL-TRANSFERASE DEFICIENCY DISEASE) causes an error in galactose metabolism called GALACTOSEMIA, resulting in elevations of galactose in the blood.Protozoan Vaccines: Suspensions of attenuated or killed protozoa administered for the prevention or treatment of infectious protozoan disease.Galectins: A class of animal lectins that bind specifically to beta-galactoside in a calcium-independent manner. Members of this class are distiguished from other lectins by the presence of a conserved carbohydrate recognition domain. The majority of proteins in this class bind to sugar molecules in a sulfhydryl-dependent manner and are often referred to as S-type lectins, however this property is not required for membership in this class.Liver Abscess: Solitary or multiple collections of PUS within the liver as a result of infection by bacteria, protozoa, or other agents.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Iodoquinol: One of the halogenated 8-quinolinols widely used as an intestinal antiseptic, especially as an antiamebic agent. It is also used topically in other infections and may cause CNS and eye damage. It is known by very many similar trade names world-wide.Adhesiveness: A property of the surface of an object that makes it stick to another surface.BangladeshSerine O-Acetyltransferase: An enzyme that catalyzes the conversion of L-SERINE to COENZYME A and O-acetyl-L-serine, using ACETYL-COA as a donor.Host-Parasite Interactions: The relationship between an invertebrate and another organism (the host), one of which lives at the expense of the other. Traditionally excluded from definition of parasites are pathogenic BACTERIA; FUNGI; VIRUSES; and PLANTS; though they may live parasitically.Pyruvate Synthase: A ferredoxin-containing enzyme that catalyzes the COENZYME A-dependent oxidative decarboxylation of PYRUVATE to acetyl-COENZYME A and CARBON DIOXIDE.Trichomonas: A genus of parasitic flagellate EUKARYOTES distinguished by the presence of four anterior flagella, an undulating membrane, and a trailing flagellum.Suppuration: A pathologic process consisting in the formation of pus.Dysentery: Acute inflammation of the intestine associated with infectious DIARRHEA of various etiologies, generally acquired by eating contaminated food containing TOXINS, BIOLOGICAL derived from BACTERIA or other microorganisms. Dysentery is characterized initially by watery FECES then by bloody mucoid stools. It is often associated with ABDOMINAL PAIN; FEVER; and DEHYDRATION.Material Safety Data Sheets: Information or data used to ensure the safe handling and disposal of substances in the workplace. Such information includes physical properties (i.e. melting, boiling, flashing points), as well as data on toxicity, health effects, reactivity, storage, disposal, first-aid, protective equipment, and spill-handling procedures.Access to Information: Individual's rights to obtain and use information collected or generated by others.Gastroenterology: A subspecialty of internal medicine concerned with the study of the physiology and diseases of the digestive system and related structures (esophagus, liver, gallbladder, and pancreas).Bibliometrics: The use of statistical methods in the analysis of a body of literature to reveal the historical development of subject fields and patterns of authorship, publication, and use. Formerly called statistical bibliography. (from The ALA Glossary of Library and Information Science, 1983)Periodicals as Topic: A publication issued at stated, more or less regular, intervals.Journal Impact Factor: A quantitative measure of the frequency on average with which articles in a journal have been cited in a given period of time.

Hsp60 is targeted to a cryptic mitochondrion-derived organelle ("crypton") in the microaerophilic protozoan parasite Entamoeba histolytica. (1/861)

Entamoeba histolytica is a microaerophilic protozoan parasite in which neither mitochondria nor mitochondrion-derived organelles have been previously observed. Recently, a segment of an E. histolytica gene was identified that encoded a protein similar to the mitochondrial 60-kDa heat shock protein (Hsp60 or chaperonin 60), which refolds nuclear-encoded proteins after passage through organellar membranes. The possible function and localization of the amebic Hsp60 were explored here. Like Hsp60 of mitochondria, amebic Hsp60 RNA and protein were both strongly induced by incubating parasites at 42 degreesC. 5' and 3' rapid amplifications of cDNA ends were used to obtain the entire E. histolytica hsp60 coding region, which predicted a 536-amino-acid Hsp60. The E. histolytica hsp60 gene protected from heat shock Escherichia coli groEL mutants, demonstrating the chaperonin function of the amebic Hsp60. The E. histolytica Hsp60, which lacked characteristic carboxy-terminal Gly-Met repeats, had a 21-amino-acid amino-terminal, organelle-targeting presequence that was cleaved in vivo. This presequence was necessary to target Hsp60 to one (and occasionally two or three) short, cylindrical organelle(s). In contrast, amebic alcohol dehydrogenase 1 and ferredoxin, which are bacteria-like enzymes, were diffusely distributed throughout the cytosol. We suggest that the Hsp60-associated, mitochondrion-derived organelle identified here be named "crypton," as its structure was previously hidden and its function is still cryptic.  (+info)

Prevalence of intestinal parasite infections with special reference to Entamoeba histolytica on the island of Bioko (Equatorial Guinea). (2/861)

The prevalence of intestinal parasitic infections was assessed (1993 through 1995) among two different groups of persons on the island of Bioko, Equatorial Guinea. In the first group, parasitologic examinations were performed on stool specimens from a household-based sample of 557 dwellers from the rural area of the island. In the second group, 1,633 inpatients and outpatients at the General Hospital of Malabo (the capital of the country) were studied. All age groups were represented in both groups. The average prevalence of the most common protozoan and helminthic intestinal infections in rural and urban areas, respectively, was as follows: Entamoeba histolytica/E. dispar (14.9% and 32.7%, respectively), Giardia lamblia (7.2% and 8.6%), Ascaris lumbricoides (45.8% and 31.4%), and Trichuris trichiura (25.7% and 36.4%). Seventy-nine sera from patients with amebic liver abscess (suspected by ultrasonography) were studied by an immunohemagglutination assay, with 44 (56%) showing anti-E. histolytica titers > or = 1:32. Of these 79 sera, 71 were studied by an enzyme immunoassay, 86% of which were positive with titers > or = 1:64. This study showed that parasitic infections in Equatorial Guinea represent a major health problem.  (+info)

Characterization of YS-27, an axenic Korean strain of Entamoeba histolytica. (3/861)

Characterization of YS-27, an axenic Entamoeba strain, was performed by three different laboratory methods. Zymodeme analysis using starch gel electrophoresis and PCR with species-specific primers showed that YS-27 is a pathogenic Entamoeba which belongs to the group II zymodeme. Pathogenicity of YS-27 was further confirmed by observing the formation of liver abscess in Mongolian gerbils. These results showed that YS-27 is E. hisolytica.  (+info)

The TATA-box binding protein of Entamoeba histolytica: cloning of the gene and location of the protein by immunofluorescence and confocal microscopy. (4/861)

A 309 bp DNA fragment from Entamoeba histolytica was amplified by PCR using primers derived from the Acanthamoeba castellanii consensus TATA-box binding protein amino acid sequence. The amplified fragment was used to isolate cDNA and genomic DNA clones containing an ORF encoding the complete E. histolytica TATA-box binding protein (Ehtbp, 702 bp, 234 aa, molecular mass 26 kDa). The EhTBP functional domain showed 55% sequence identity to that of Homo sapiens, 54% to A. castellanii and 37% to Plasmodium falciparum TBPs. In Southern blot experiments we detected a single Ehtbp band, which was transcribed as a 1.3 kb mRNA containing a 420 nt 5' untranslated region. However, the probe hybridized with the 0.8 and 1.5 Mb chromosomes, suggesting that this sequence is diploid. In situ PCR assays showed two signals in 95% of trophozoites, one located in the nucleus and another in EhkO, the novel DNA-containing organelle recently reported. The recombinant E. histolytica TATA-box binding protein was expressed in Escherichia coli. Antibodies against it recognized two proteins of 26 and 29 kDa in E. histolytica nuclear extracts. Confocal microscopy immunofluorescence analysis located the protein in both the nucleus and EhkO.  (+info)

Preparation of recombinant human monoclonal antibody Fab fragments specific for Entamoeba histolytica. (5/861)

Genes coding for human antibody Fab fragments specific for Entamoeba histolytica were cloned and expressed in Escherichia coli. Lymphocytes were separated from the peripheral blood of a patient with an amebic liver abscess. Poly(A)+ RNA was isolated from the lymphocytes, and then genes coding for the light chain and Fd region of the heavy chain were amplified by a reverse transcriptase PCR. The amplified DNA fragments were ligated with a plasmid vector and were introduced into Escherichia coli. Three thousand colonies were screened for the production of antibodies to E. histolytica HM-1:IMSS by an indirect fluorescence-antibody (IFA) test. Lysates from five Escherichia coli clones were positive. Analysis of the DNA sequences of the five clones showed that three of the five heavy-chain sequences and four of the five light-chain sequences differed from each other. When the reactivities of the Escherichia coli lysates to nine reference strains of E. histolytica were examined by the IFA test, three Fab fragments with different DNA sequences were found to react with all nine strains and another Fab fragment was found to react with seven strains. None of the four human monoclonal antibody Fab fragments reacted with Entamoeba dispar reference strains or with other enteric protozoan parasites. These results indicate that the bacterial expression system reported here is effective for the production of human monoclonal antibodies specific for E. histolytica. The recombinant human monoclonal antibody Fab fragments may be applicable for distinguishing E. histolytica from E. dispar and for use in the serodiagnosis of amebiasis.  (+info)

Down regulation of Entamoeba histolytica virulence by monoxenic cultivation with Escherichia coli O55 is related to a decrease in expression of the light (35-kilodalton) subunit of the Gal/GalNAc lectin. (6/861)

Entamoeba histolytica virulence is related to a number of amebic components (lectins, cysteine proteinases, and amebapore) and host factors, such as intestinal bacterial flora. Trophozoites are selective in their interactions with bacteria, and the parasite recognition of glycoconjugates plays an important role in amebic virulence. Long-term monoxenic cultivation of pathogenic E. histolytica trophozoites, strains HK-9 or HM-1:IMSS, with Escherichia coli serotype O55, which binds strongly to the Gal/GalNAc amebic lectin, markedly reduced the trophozoites' adherence and cytopathic activity on cell monolayers of baby hamster kidney (BHK) cells. Specific probes prepared from E. histolytica lectin genes as well as antibodies directed against the light (35-kDa) and heavy (170-kDa) subunits of the Gal/GalNAc lectin revealed a decrease in the transcription and expression of the light subunit in trophozoites grown monoxenically with E. coli O55. This effect was not observed when E. histolytica was grown with E. coli 346, a mannose-binding type I pilated bacteria. Our results suggest that the light subunit of the amebic lectin is involved in the modulation of parasite adherence and cytopathic activity.  (+info)

Chitinase secretion by encysting Entamoeba invadens and transfected Entamoeba histolytica trophozoites: localization of secretory vesicles, endoplasmic reticulum, and Golgi apparatus. (7/861)

Entamoeba histolytica, the protozoan parasite that phagocytoses bacteria and host cells, has a vesicle/vacuole-filled cytosol like that of macrophages. In contrast, the infectious cyst form has four nuclei and a chitin wall. Here, anti-chitinase antibodies identified hundreds of small secretory vesicles in encysting E. invadens parasites and in E. histolytica trophozoites overexpressing chitinase under an actin gene promoter. Abundant small secretory vesicles were also identified with antibodies to the surface antigen Ariel and with a fluorescent substrate of cysteine proteinases. Removal of an N-terminal signal sequence directed chitinase to the cytosol. Addition of a C-terminal KDEL peptide, identified on amebic BiP, retained chitinase in a putative endoplasmic reticulum, which was composed of a few vesicles of mixed sizes. A putative Golgi apparatus, which was Brefeldin A sensitive and composed of a few large, perinuclear vesicles, was identified with antibodies to ADP-ribosylating factor and to epsilon-COP. We conclude that the amebic secretory pathway is similar to those of other eukaryotic cells, even if its appearance is somewhat different.  (+info)

Intestinal mucins in colonization and host defense against pathogens. (8/861)

Intestinal mucins are key components of the first line of host defense against intestinal pathogens. These large glycoconjugates secreted by specialized exocrine goblet cells form viscous gels that trap microorganisms and irritants and limit their diffusion to the intestinal epithelium. Moreover, they allow for colonization by indigenous bacterial flora that prevents attachment of pathogenic microbes. The interaction between microbes and mucins involves mucin carbohydrate side chains and microbial adhesin molecules. Certain microorganisms and disease states may alter mucin biochemistry or expression. Although these alterations most likely contribute to disease processes, the full impact of these phenomena are still unclear. The development of mucin-secreting cell lines has facilitated the study of mucin biology and aided our understanding of mucin-microbial interactions.  (+info)

  • Due to their mobile nature, some EhSINE copies may occupy different genomic locations among isolates of E. histolytica possibly affecting adjacent gene expression. (omicsonline.org)
  • We also review our current understanding of the diversity of Entamoeba histolytica clinical isolates in Japan, based on polymorphic genetic markers, clinical representations, and in vivo virulence, using an animal model. (elsevier.com)
  • To investigate the possible existence of invasive and noninvasive strains as one factor, the ability to differentiate individual isolates of E. histolytica is necessary. (lshtm.ac.uk)
  • Use of multiple loci collectively allowed differentiation of a majority of the 13 isolates studied, and we believe that these loci have the potential to be used as polymorphic molecular markers for investigating the epidemiology of E. histolytica and the potential existence of genetically distinct invasive and noninvasive strains. (lshtm.ac.uk)
  • June 14: According to the World Health Organization (WHO), Entamoeba histolytica is the third-leading cause of morbidity and mortality due to parasitic disease in humans. (indiaties.in)
  • A total of 94% of patients treated with nitazoxanide were free of Entamoeba histolytica in two post-treatment stool specimens compared with only 43% of patients receiving placebo. (oncologynurseadvisor.com)
  • The adherent mucous gel layer lining the colonic epithelium is the first line of host defense against invasive pathogens, such as Entamoeba histolytica . (asm.org)
  • The release of a histolytic cysteine proteinase from E. histolytica correlates with the pathogenicity of both axenic strains and recent clinical isolates as determined by clinical history of invasive disease, zymodeme analysis, and cytopathic effect. (jci.org)
  • It inhibits many of the key enzymes that are involved in the metabolism and virulence of the parasite Entamoeba histolytica through S-nitrosylation of essential cysteine residues. (asm.org)
  • An important virulence factor, a 27-kDa cysteine protease, was also enriched in early and late endosomes of E. histolytica . (unl.edu)
  • Allicin from garlic strongly inhibits cysteine proteinases and cytopathic effects of Entamoeba histolytica. (asm.org)
  • E. histolytica secreted products were examined for mucinase activity utilizing mucin metabolically labeled with [ 35 S]cysteine as a substrate. (asm.org)
  • These results are the first to show that E. histolytica cysteine proteinases alter the protective function of the mucous barrier by disrupting the structure of the MUC2 polymer. (asm.org)
  • A number of studies have shown that peptidases and in particular cysteine peptidases constitute major pathogenicity factors in Entamoeba histolytica . (biomedcentral.com)
  • Cysteine peptidases are considered to play a major role for the pathogenicity of E. histolytica as suggested by a large number of in vitro and in vivo studies [ 1 - 9 ]. (biomedcentral.com)
  • The library was screened with rabbit polyclonal anti-E. histolytica serum. (pnas.org)
  • We demonstrate that E. histolytica acquires and displays human cell membrane proteins through trogocytosis and that this leads to protection from lysis by human serum. (asm.org)
  • Here, we demonstrate for the first time that E. histolytica acquires and displays human cell membrane proteins by taking "bites" of human cell material in a process named trogocytosis ("trogo-" means "nibble"), and that this allows amoebae to survive in human serum. (asm.org)
  • Western blots using excretory-secretory antigen (ESA) collected from axenically grown Entamoeba histolytica were probed with the above serum samples. (asm.org)
  • The RIDASCREEN® Entamoeba histolytica IgG test is an enzyme immunoassay for the qualitative determination of IgG antibodies against Entamoeba histolytica in human serum. (r-biopharm.com)
  • To interrupt transmission of the parasite and to avoid progression of infected individuals to invasive disease, treatment of E. histolytica carriers has been recommended ( 36 ). (asm.org)
  • W hile an estimated 90% of E. histolytica infections are asymptomatic, prospective studies of asymptomatic carriers indicate a risk of invasive disease of 5/56 (9%) over the course of 6-12 months ( 26 ). (antimicrobe.org)
  • Accordingly, the risk of developing invasive disease, as well as decreased transmission, are rationales for treating asymptomatic carriers of E. histolytica , however WHO recommends against treatment of asymptomatic patients when only a morphologic diagnosis by stool examination is available (i.e. (antimicrobe.org)
  • The adherent mucous gel layer lining the colonic epithelium is the first line of host defense against invasive pathogens, such as Entamoeba histolytica . (asm.org)
  • E.histolytica always elicits a serological response whether it is invasive or whether the person is asymptomatic -- only 10 precent do develop serious disease. (parasite.org.au)
  • Please feel free to email us at the email address below with any insights, coments, or questions about entamoeba histolytica. (entamoebahistolytica.org)
  • A gamma gt11 cDNA library was constructed from poly(U)-Sepharose-selected Entamoeba histolytica trophozoite RNA in order to clone and identify surface antigens. (pnas.org)
  • E. histolytica has a lectin that binds to galactose and N-acetylgalactosamine sugars on the surface of the epithelial cells, The lectin normally is used to bind bacteria for ingestion. (wikipedia.org)
  • The adherence of Entamoeba histolytica to colonic mucins and to host cells appears to be predominantly mediated by a 170-kDa surface lectin of the amoebae. (pnas.org)
  • From the matrix-assisted laser desorption ionization-two-stage time of flight (MALDI-TOF/TOF) analysis, the proteins were identified as heavy subunits of E. histolytica lectin and E. histolytica pyruvate phosphate dikinase, respectively. (asm.org)
  • Use of the E. histolytica lectin for diagnosis of ALA has been well reported by researchers and is being used in commercialized kits. (asm.org)
  • To begin to identify the role of Rab GTPases in E. histolytica , an oligonucleotide approach was employed to screen an E. histolytica cDNA library for genes encoding Rab-like proteins. (unl.edu)
  • Phylogenetic analysis and alignment of EhRab11 with other Rab proteins demonstrated that EhRab11 shared significant homology at the amino acid level with Rab 11-like proteins from a number of other eukaryotes, suggesting that EhRab11 is a Rab11 homolog for E. histolytica . (unl.edu)
  • We have assigned putative function to 3,788 proteins (46% of the predicted proteome) based on the annotation of predicted gene families, and have identified 58 protein families of five or more members that share no homology with known proteins and thus could be entamoeba specific. (pubmedcentralcanada.ca)
  • Children homozygous for the R223 allele were 4 times more likely to have E. histolytica diarrhea than those homozygous for the wild-type Q223 allele. (asm.org)