T_11 Protozoários urogenitais e intestinais ★ Flashcards
Como podemos dividir os Parasitas?
Protozoários – Parasitas unicelulares.
Metazoários - Pluricelurares
Qual é o protozoário urogenital que conheces?
TRICHOMONAS VAGINALIS
Caracteriza a estrutura e epidemiologia do Trichomonas vaginalis.
Physiology and Structure
T. vaginalis is not an intestinal protozoan; rather, it is the cause of urogenital infections.
The organism’s four cilia and short, undulating membrane are responsible for motility.
T. vaginalis exists only as a trophozoite and is found in the urethras and vaginas of women and the urethras and prostate glands of men.
Epidemiology
This parasite has worldwide distribution, with sexual intercourse as the primary mode of transmission.
Occasionally, infections have been transmitted by fomites (toilet articles, clothing), although this transmission is limited by the lability of the trophozoite form.
Infants may be infected by passage through the mother’s infected birth canal.
The prevalence of T. vaginalis in developed countries is reported to be 5% to 20% in women and 2% to 10% in men.
Em que formas podemos encontrar o Trichomonas vaginalis?
Só existe sob a forma de trofozoíto (forma vegetativa, forma e tamanho parecidos com um leucócito, mas com flagelos, permitindo o movimento e a sua distinção).
Qual é a manifestação clínica da infeção pro Trichomonas vaginalis?
A principal manifestação clínica, como o nome indica, é a vaginite, embora muitas infeções sejam assintomáticas.
Raramente, no homem, pode causar uretrite ou prostatite.
Most infected women are asymptomatic or have a scant, watery vaginal discharge.
Vaginitis may occur with more extensive inflammation and erosion of the epithelial lining that is associated with itching, burning, and painful urination.
Infection has also been associated with premature rupture of membranes, premature birth, other adverse pregnancy outcomes, and posthysterectomy cuff infections.
Men are primarily asymptomatic carriers who serve as a reservoir for infections in women.
However, men occasionally experience urethritis, prostatitis, and other urinary tract problems.
Neonates can acquire the organism via passage through the birth canal and reports have documented T. vaginalis as a cause of neonatal pneumonia and conjunctivitis.
Como é feito o diagnóstico da infeção por Trichomonas vaginalis?
O diagnóstico faz-se através da mobilidade da Trichomonas.
A colheita do exsudado vaginal é feita com zaragatoa e observa-se a mobilidade da Trichomonas.
Pode também ser utilizada a cultura, também com observação da mobilidade.
A imunofluorescência raramente é utilizada.
Também pode ser utilizada biologia molecular (PCR).
The microscopic examination of vaginal or urethral discharge for characteristic trophozoites is the diagnostic method of choice.
Stained (Giemsa, Papanicolaou) or unstained smears can be examined.
The diagnostic yield may be improved by culturing the organism (93% sensitivity) or using monoclonal fluorescent antibody staining (86% sensitivity).
A nucleic acid probe assay also is available commercially.
Serologic tests may be useful in epidemiologic surveillance.
Como é feito o tratamento da trichomoníase?
The drug of choice is metronidazole. Both male and female sex partners must be treated to avoid reinfection.
Resistance to metronidazole has been reported and may require retreatment with higher doses.
More recently, tinidazole has received FDA approval for treatment of trichomoniasis in adults and may be used as a first-line agent or for cases refractory to metronidazole.
Personal hygiene, avoidance of shared toilet articles and clothing, and safe sexual practices are important preventive actions.
Elimination of carriage in men is critical for the eradication of disease.
Quais são os protozoários intestinais que conheces?
- Entamoeba histolytica
- Giardia spp. (duodenalis) (lamblia e intestinalis)
- Dientamoeba fragilis
- Neobalantidium coli
- Sarcocystis spp.
- Cryptosporidium spp.
- Cyclospora spp.
- Cytoisospora belli
A negrito os referidos na aula
A itálico referidos como causadores de doença no imunodeprimido e crianças mas não taõ relevantes para nós (últimos 3)
Qual é a principal via de contaminação dos protozoários intestinais?
Fecal-oral
Caracteriza a epidemiologia da Entamoeba histolytica
- Mais prevalente em países em desenvolvimento com climas tropicais.
- Dada a transmissão fecal oral, o mau saneamento básico e reservatórios contaminados são fatores predisponentes à transmissão do parasita.
- A maioria dos indivíduos infetados são assintomáticos, e funcionam como reservatórios da doença.
- Dado o perfil do sistema digestivo humano o trofozoíto não sobrevive a ingestão e passagem no estômago, daí a forma infetante ser o quisto.
- Transmissão sexual, por práticas anais-orais, também encontra a sua prevalência em áreas endémicas deste parasita.
- O trofozoíto em situações raras, pode causar amebíase cutânea, por inoculção direta, nomeadamente em encontros sexuais.
Cyst and trophozoite forms of E. histolytica are detected in fecal specimens from infected patients.
Trophozoites can also be found in the crypts of the large intestine. In freshly passed stools, actively motile trophozoites can be seen, whereas in formed stools, the cysts are usually the only form recognized.
For the diagnosis of amebiasis, distinguishing between the E. histolytica trophozoites and cysts and those of commensal amebae, such as E. coli, is important.
E. histolytica has a worldwide distribution.
Although it is found in cold areas such as Alaska, Canada, and Eastern Europe, its incidence is highest in tropical and subtropical regions that have poor sanitation and contaminated water.
The average prevalence of infection in these areas is 10% to 15%, with as
many as 50% of the population infected in some areas.
Many of the infected individuals are asymptomatic carriers who represent a reservoir for the spread of E. histolytica to others.
Patients infected with E. histolytica pass noninfectious trophozoites and the infectious cysts in their stools.
The trophozoites cannot survive in the external environment or in transport through the stomach if ingested. Therefore the main source of water and food contamination is the asymptomatic carrier who passes cysts.
This is a particular problem in hospitals for the mentally ill, military and refugee camps, prisons, and crowded day-care centers.
Flies and cockroaches also can serve as mechanical vectors for the transmission of E. histolytica cysts. Sewage containing cysts can contaminate water systems, wells, springs, and agricultural areas in which human waste is used as fertilizer.
Finally, cysts can be transmitted by oral-anal sexual practices, with amebiasis prevalent in homosexual populations.
Direct trophozoite transmission in sexual encounters can produce cutaneous amebiasis.
Quais são as formas estruturais da Entamoeba histolytica? Distingue-as caracterizando o processo patogénico da infeção por este organismo.
- A forma de quisto (infetante) entra no organismo (via oral) e desce até ao estômago. {o trofozoíto até pode entrar, mas vai morrer no ambiente ácido do estômago}
- O baixo pH vai estimular mudanças no quisto, que, aos chegar ao duodeno, liberta os trofozoítos (forma patogénica - que causa a doença)
- Estes seres vão causar a necrose do intestino grosso
- Também causam a lise de células do SImune, como os neutrófilos, por alterações da permeabilidade da membrana dos mesmos levando a, um aumento da [Ca2+] intracelular, e consequente lise, com libertação de mediadores inflamatórias e exponencialização da destruição tecidual local.
- Causam úlceras em forma de frasco (triangulares, base larga e vértice (luminal) mais apertado)
- Tudo o que for Amebíase extraintestinal, vai ser sempre causada por trofozoítos.
- Amebae are found only in environments that have a low oxygen pressure because the protozoa are killed by ambient oxygen concentrations.
Cyst and trophozoite forms of E. histolytica are detected in fecal specimens from infected patients.
Trophozoites can also be found in the crypts of the large intestine. In freshly passed stools, actively motile trophozoites can be seen, whereas in formed stools, the cysts are usually the only form recognized.
For the diagnosis of amebiasis, distinguishing between the E. histolytica trophozoites and cysts and those of commensal amebae, such as E. coli, is important.
After ingestion, the cysts pass through the stomach, in which exposure to gastric acid stimulates the release of the pathogenic trophozoite in the duodenum.
The trophozoites divide and produce extensive local necrosis in the large intestine. The basis for this tissue destruction is incompletely understood, although it is attributed to production of a cytotoxin.
Attachment of E. histolytica trophozoites to host cells via a galactose-inhibitable adherence protein is required for cytolysis and tissue necrosis to occur.
The lysis of colonic epithelial cells, human neutrophils, lymphocytes, and monocytes by trophozoites is associated with a lethal alteration of host cell membrane permeability, resulting in an irreversible increase in intracellular calcium levels.
The release of toxic neutrophil constituents after the lysis of neutrophils may contribute to the tissue destruction.
Flask-shaped ulcerations of the intestinal mucosa are present with inflammation, hemorrhage, and secondary bacterial infection.
Invasion into the deeper mucosa with extension into the peritoneal cavity may occur. This can lead to secondary involvement of other organs, primarily the liver but also the lungs, brain, and heart.
Extraintestinal amebiasis is associated with trophozoites.
Amebae are found only in environments that have a low oxygen pressure because the protozoa are killed by ambient oxygen concentrations.
Lectin binding, zymodeme analysis, genome deoxyribonucleic acid (DNA) analysis, and staining with specific monoclonal antibodies have been used as markers to identify invasive strains of E. histolytica.
It is now recognized that the ameba morphologically identified as E. histolyticais actually four distinct species.
The pathogenic species is E. histolytica, and the nonpathogenic species are E. dispar, E. moshkovskii, and E. bangladeshi.
The zymodeme profiles and biochemical, molecular, and immunologic differences are stable and support the existence of four species. Of note, these four species are morphologically indistinguishable from one another.
Qual é o local extraintestinal primordial da Amebíase?
Fígado, causa abcessos hepáticos, e o responsável é sempre o trofozoíto.
Porquê?
Os trofozoítos no sangue são removidos pelo fígado alojando-se aí.
Os abcessos tendencialmente formam-se no lobo direito, causndo dor no hipocôndrio direito, hepatoesplenomegália e elevação do diafragma.
Caracteriza a clínica da Entamoeba histolytica
Infeção por Entamoeba histolytica, vamos ter 3 possíveis outcomes:
* Portador (assintomático), a maioria
* Amebíase Intestinal = Disenteria amebiana
* Amebíase Extraintestinal
Para ser portador:
1. A estirpe de E.histolytica tem de ter baixa virulência
2. Inocular pouca quantidade
3. O SImune estar intacto
A Disenteria amebiana causa sintomas relacionados com a destruição local do intestino grosso:
* Dor abdominal
* Cólica
* Colite com diarreia
* Nos casos mais severas, grandes quantidades de fezes sanguinolentas
Amebíase extraintestinal, caracteriza-se por uma disseminação sistémica do trofozoíto e terá como consequências:
* Febre
* Leucocitose
* Rigor
O principal órgão extraintestinal afetado é o fígado
The outcome of infection may result in a carrier state, intestinal amebiasis, or extraintestinal amebiasis.
If the strain of E. histolytica has a low virulence, if the inoculum is low, or if the patient’s immune system is intact, the organisms may reproduce, and cysts may be passed in stool specimens with no clinical symptoms.
Although infections with E. histolytica may be asymptomatic, most asymptomatic individuals are infected with the noninvasive E. dispar or
E. moshkovskii, as characterized by specific isoenzyme profiles (zymodemes), DNA-based assays, their susceptibility to complement-mediated lysis, and their failure to agglutinate in the presence of the lectin concanavalin A.
Detection of carriers of E. histolytica in areas with a low endemicity is
important for epidemiologic purposes.
Patients with intestinal amebiasis develop clinical symptoms related to the localized tissue destruction in the large intestine.
These include abdominal pain, cramping, and colitis with diarrhea.
More severe disease is characterized by numerous bloody stools per day.
Systemic signs of infection (fever, leukocytosis, rigors) are present in patients with extraintestinal amebiasis.
The liver is primarily involved because trophozoites in the blood are removed as they pass through this organ.
Abscess formation is common. The right lobe is most commonly involved. Pain over the liver with hepatomegaly and elevation of the diaphragm is observed
Extra - Dx laboratorial e tratamento da Amebíase
The identification of E. histolytica trophozoites and cysts in stools and trophozoites in tissue is diagnostic of amebic infection.
Care must be taken to distinguish between these amebae and commensal amebae, as well as between these amebae and polymorphonuclear leukocytes.
Microscopic examination of stool specimens is inherently insensitive because the protozoa are not usually distributed homogeneously in the specimen, and the parasites are concentrated in the intestinal ulcers and at the margins of the abscess, not in the stool or the necrotic center of the abscess.
For this reason, multiple stool specimens should be collected.
Extraintestinal amebiasis is sometimes diagnosed using scanning procedures for the liver and other organs.
Specific serologic tests, together with microscopic examination of the abscess material, can confirm the diagnosis.
Virtually all patients with hepatic amebiasis and most patients (more than 80%) with intestinal disease have positive serologic findings at the time of clinical presentation.
This may be less useful in endemic areas in which the prevalence of positive serologic results is higher.
Examinations of stool specimens are frequently negative in extraintestinal disease.
In addition to conventional microscopic and serologic tests, researchers have developed several immunologic tests for the detection of fecal antigen, as well as polymerase chain reaction (PCR) and DNA-probe assays for the detection of pathogenic strains of E. histolytica (versus nonpathogenic E. dispar and E. moshkovskii). These newer diagnostic approaches are now commercially available.
Acute, fulminating amebiasis is treated with metronidazole, followed by iodoquinol, diloxanide furoate, or paromomycin.
Asymptomatic carriage can be eradicated with iodoquinol, diloxanide furoate, or paromomycin.
As already noted, human infection results from the ingestion of food or water contaminated with human feces or as a result of specific sexual practices.
The elimination of the cycle of infection requires the introduction of adequate sanitation measures and education about the routes of transmission.
The chlorination and filtration of water supplies may limit the spread of these and other enteric protozoal infections but are not possible in many developing countries.
Physicians should alert travelers to developing countries about the risks associated with the consumption of water (including ice cubes), unpeeled fruits, and raw vegetables. Water should be boiled and fruits and vegetables thoroughly cleaned before consumption.
Caracteriza o Neobalantidium coli
- Protozoário intestinal
- 2 formas: Quisto-infetante , Trofozoíto- patogénica
- Trofozoíto é ciliado!
- Distribuição universal, sendo o porco o principal reservatório e a transmissão fecal oral
- Clínica - Disenteria (semelhante à amebíase, com a diferença de não ter entidade clínicas extraintestinais
- Diagnóstico faz-se por obsevação microscópica de quistos e trofozoítos nas fezes, sendo que estes são maiores e ciliados em relação aos outros protozoários intestinais
- Tratamento - tetraciclina, com possível alternativa de Metronidazol + iodoquinol
The intestinal protozoan N. coli is the only member of the Ciliophora group that is pathogenic for humans.
Disease produced by N. coli is similar to amebiasis because the organisms elaborate proteolytic and cytotoxic substances that mediate tissue invasion and intestinal ulceration.
Physiology and Structure
The life cycle of N. coli is simple, involving ingestion of infectious cysts, excystation, and invasion of trophozoites into the mucosal lining of the large intestine, cecum, and terminal ileum.
The trophozoite is covered with rows of hairlike cilia that aid in motility.
Morphologically more complex than amebae, N. coli has a funnel-like primitive mouth called a cytostome, which is a large and small nucleus involved in reproduction, food vacuoles, and two contractile vacuoles.
Epidemiology
N. coli is distributed worldwide. Swine and (less commonly) monkeys are the most important reservoirs. Infections are transmitted by the fecal-oral route; outbreaks are associated with contamination of water supplies with pig feces.
Person-to-person spread, including through food handlers, has been implicated in outbreaks. Risk factors associated with human disease include contact with swine and substandard hygienic conditions.
Clinical Syndromes
As with other protozoan parasites, asymptomatic carriage of N. coli can exist.
Symptomatic disease is characterized by:
* abdominal pain and tenderness,
* tenesmus,
* nausea,
* anorexia, and
* watery stools with blood and pus.
Ulceration of the intestinal mucosa, as with amebiasis, can be seen; a secondary complication caused by bacterial invasion into the eroded intestinal mucosa can occur.
Extraintestinal invasion of other organs is extremely rare in neobalantidiasis.
Laboratory Diagnosis
Microscopic examination of feces for trophozoites and cysts is performed. The trophozoite is very large, varying in length from 50 to 200μm and in width from 40 to 70μm. The surface is covered with cilia, and the prominent internal structure is a macronucleus. A micronucleusalso is present.
Two pulsating, contractile vacuoles also are seen in fresh preparations of the trophozoites. The cyst is smaller (40 to 60 μm in diameter), is surrounded by a clear refractile wall, and has a single nucleus in the
cytoplasm. N. coli is a large organism compared with other intestinal protozoa and is readily detected in fresh, wet microscopic preparations.
Treatment, Prevention, and Control
The drug of choice is tetracycline; iodoquinol and metronidazole are alternative antimicrobials. Actions for prevention and control are similar to those for amebiasis. Appropriate personal hygiene, maintenance of sanitary conditions, and the careful monitoring of pig feces are all important preventive measures.
