Slide 1

Mekanisme System Immun Sal. CernaOleh :

Efrida Warganegara

IntroductionMicrooragnism (parasites or pathogens) where their presence in the body is often associated with pathological changes and they are rarely found in healthy individuals identification of these m.o. is important indication of actual or potential disease state

The other organisme (in this chapter) may cause diasease under certain circumstances :a) Newborn; b) Stressed; c) Traumatized, ord) Imunocompromizes individualisbut usually co-exist quite peacefully in a balanced relationship with their hostMany of m.o. this form what is termed the indigenous or normal flora of the body, a collection of spesies routinely in the normal, healthy individualSome of this species are positively benefecial to the hostM.O. that benefit from this association without harming the host are referred to as commensals

IntroductionTerm flora is used because the majority of the m.o. are bacteria.Antibiotic therapi can eliminated normal flora, but is not possible to eliminate the normal flora of the skin or intestine antibiotica can drastically reduce their number to a minimumThe host may then be overun by introduce patogens or by overgrowth of m.o. normally present in small numberIntroductionCommensalismThe normal flora (commensals) is aquired rapidly during and shortly after birth and changes continously throughout life.It has been estimated that human have approximately 1013 cells in the body and something like 1014 bacteria associated with them, the majority in the large bowel.Virus, fungi and protozoa can also be found in healthy individuals, although these form only a minor component of the total population or resident organismBefore birth the fetus is essentially in a steril environment, but at delivery m.o. come into contact with the infantSome of these m.o. are derived from the mother or others who come into contact with the infantConstituent organism present at any given time reflect the age, nutrition and environmet of the individual concernedCommensalismMost m.o. are transient paserby that are destroyed by conditions in the host, but others establish themselves and produce microcolonies colonized the host microflora establishedNot all area of the body are occupied by commensal spesiesThere are appreciable numbers of m.o. in the : Upper Resp. Tract, lower intestinal tract, and skin Esophagus, urinary tract and stomach contain few m.o. The blood, spinal fluid, urine and endothelial tissues are normally steril CommensalismMicroflora remain with the host for life, with only minor changes resulting disease, diatery alteration, or hormonal changes

The factors that influence the kind and number of m.o. at any body site are :1. The availabiliy or unavailability oxygen2. The availability of appropriate receptor sites for attachment3. The pH of the host site4. The availability of nutrient5. The influence exerted by other m.o. at the site, and6. The immunological respone of the host to the presence of the m.o.CommensalismMany of the flora normal may be important in maintaining the health of the host, for example : 1) some m.o. in intestinal capable sinthesizing vitamin (pathothenic acid, riboflavin, B12, vit. k) certain vitamine deficiencies in human diet can be remedied by bacterial vitamin synthesis in the inteswtinal tract ; 2) some flora normal produce metabolic product that are effective in preventing invasion by parasites (flora normal in intestinal tarct produce fatty acid that inhibit ingested bacteria that attempt to colonize the hostAdvantages of Flora Normal3) Gut bacteria release a number of factors with antibacterial activity (bacteriocin, colicin) and metabolic waste product, which, together with lack of available oxygen, prevent the establishment of other species4) Vaginal lactobacilli maintain an acid environment that supresses growth of other organism Advantages of Flora NormalDisadvantages of Flora normalDisadvantages of Flora normal lie primarily in the potential for spread into previously streile parts of the body.This may happen under a variety of circumstance : when intestine perforated or skin is broken, during extraction of teeth, E. coli from the perianal skin ascend the urethraOvergrowth by potentially pathogenic members of the normal flora can occur when the composition of the flora normal changes (after antibiotics), when the local environment chabges (increases in stomach or vaginal pH) or when the immune system becomes ineffective (AIDS)Under these conditions, potential pathogens take the opportunity to increase their population size or invade tissues, so becoming harmful to the hostA). Distibution of flora normalCommensals in Intestinal TractMany m.o. can enter the intestinal tract by ingestion of food and drinkThe density of m.o. increases as one passes along the GIT from stomach to the large intestineStomach contents harbour only transient organism, the acidic pH providing an unfavorable environment and forming an effective barrier.However, the gastric mucosa may be colonized by acid tolerant lactobacilli and streptococcusThe upper intestine is only lightly colonized (104 organism per gram) but population increase markedly in the ilium, where streptococci, lactobacilli, enterobacteria and Bacteroides spp. may all be presentIn the large bowel bacterial number are very high (estimated at 1011 per gram) and many different species can be found. The vast majority (95-99%) are anaerobes, Bacteroides being especially common and a major component of fecal materialCommensals in Intestinal TractB). Commensals in Intestinal TractHelicobacter pyloriOleh :

Efrida WarganegaraIntroduction -- ClassificationCampylobacter spp. are curved or S-shaped, Gram negatif rods, oxidative-positive, nonsporeforming, micro-aerophilic, motile by lopotrichous flagellum from 1950s until 1970s they not recoqnized as a common human pathogen

Today, Genus Campylobacter is recoqnized as one of the causes of bacterial diarrhoea in humans worldwide

One of species : Campylobacter pylori, in the last 10 years then transfferred to the new genus / now reclassified as Helicobacter pylori is an important cause of gastritis and gastric/duodenal ulcers

Helicobacter pylori was first isolated from human gastric mucosa in 1983

The mechanism of pathogenicity has still to be identified although production of cytotoxinns has been described

Introduction -- ClassificationPathogenesisThe organism appears to be spread by close familial contact but the route of transmission is nor known.

The incidence of infection increases after the age of 7 years

The pathogenic mechanism of helicobacter pylori are as yet poorly defined

The organism colonized only gastric-type epithelium, apparantely by adhesive pilli.The organism produces urease and it has been postulated that this compound acts as a protective device.

Ammonia is a product of urease activity and it could protect the m.o. from stomach acidity

High concentration of ammonia produced by large numbers of bacteria could also be responsible for the inflamatory condition in the stomach

Chronic inflammation often remains clinically silentPathogenesisHelicobacter pylori can colonize the duodenum as well as the stomach and may be responsible for peptic ulcer. Several studies have pointed to an association between Helicobacter pylori and carcinoma of the stomach

When individuals with peptic ulcer are treated with acid-reducing therapies, there is temporary cure

Once the treatment is stopped, the ulcers reappear in about 70 percent of patients

If these individuals are later treated with antimisrobials against Helicobacter pylori, ulcer recurrences are reduced significantly

PathogenesisDiagnosisDiagnosis is usually ;

1. made on the basis of stained, culture, histological examination of the biopsi spesimen for the presence of bacteria, or

2. detection of urease activity in bopsy specimens

Collection by gastric biopsy transported immediately to the laboratory in sterile saline solution, processed by grinding, and plated without delay.

If short delayed are expected, the specimen can be keep at 4oC without a significant loss in viability of Helicobacter pylori.

If more than 6 hours is required before processing of the specimen, Stuart transport medium has been shown to increase survival of the organisms for up to 48 hours, especially if storage temperatures are below 15o CSpecimen collection and ProcessingGrowth RequirementsTo isolate Helicobacter pylori, biopsy specimen should be inoculated onto choccolate agar, incubated as for enteric campylobacter at 37o C, and examined daily for 5 days.

The ideal selective medium not yet been develop.

Several laboratorium have had success utilizing Skirrow medium in addition to the nonselective media.Regardless of the medium utilized, Helicobacter pylori grows best on fresh, moist media in a humid environment

Cultures for Helicobacter pylori should be placed in an environment with increased humidity

A wet paper towel added to the jar or bag is helpful

Plates should be examine for at least 5 days.Growth RequirementsCultural CharacteristicHelicobacter spp. are Gram-negative rods, which , in addition to appearing like campylobacters, can be straight cells

Their size is also similar to the campylobacters

Two of the spesies, H. cinaidi and H.fennelliae, are motile by means of a single polar flagellum, Helicobacter pylori is usually lopotrichous

Colonies are 1 to 2 mm in diameter, smooth, convex, and transluscent

Two colony type : a) non hemolytic, round, and raised and 2) non hemolytic, flat, and spread along the streak lineBiochemical IdentificationHelicobacter pylori can be identified presumptively by oxidase activity , and the presence of strong urease activity, and urea hydrolysis.

The organism produce large amounts of urease, probably a useful strategy for survival in the acid environment of the gastric mucosa

In Christensen medium a color change is usually observed in as little as10 minutes

It should be noted that this urease enzyme permitts noninvasive diagnosis of Helicobacter pylori infectionSerologiesSerological diagnosis may in future play a valuable part in investigation of patients thereby avoiding invasive procedures

ELISA is the most common serological test and can be used to monitor eradication of helicobacter pylori.TreatmentTreatment with combination of bismusth salts with metronidazole or tinidazole with amoxicillin or tetacyclin, is successful but relapse is common

At present the epidemiology of Helicobacter pylori is unknown and it is impossible to distinguish between relaps due to the failure of treatment to eradicate all organism from the GIT, or due to reinfection from an external source

Daftar kepustakaanMimsBoydBarbara J HowardTerima Kasih