Microbiological aspect of liver

MICROBIOLOGICAL ASPECT OF LIVER

DR.SAUMYA SINGHP.G 2ND YR

MICROBIOLOGY Departmentdr.d.y.patil medical college

kolhapur

The liver serves as the initial site of filtration of absorbed intestinalluminal contents and is particularly susceptible to contactwith microbial antigens of all varieties.

The liver can be affected by :

(1) Spread of bacterial or parasitic infection from outside the liver;

(2) Primary infection by Spirochetal, Protozoal, Helminthic, or Fungal organisms;

(3) Systemic effects of bacterial or granulomatous infections.

4) Viruses

BACTERIAL INFECTIONS INVOLVING OR AFFECTING THE LIVER

GRAM-POSITIVE AND GRAM-NEGATIVE BACTERIA

Pyogenic Liver Abscess

Pyogenic liver abscess is a pus filled area within the liver.

Causes:

Infection in the blood( Hematogenous spread) Staphylococcus aureus or Streptococcus milleri.

An infection of biliary tract ;enteric gram – bacilli and enterococci .

Pelvic or colonic source: mixed flora incl. Aerobic and anaerobicespecially B. fragilis.

Toxic Shock Syndrome

It is a multisystem disease . Staphylococcus aureus or Group A Streptococci.

Hepatic involvement - Jaundice and extensive necrosis. Toxic shock syndrome toxins (superantigens ) cause T cell activation and massive cytokine release.

Clostridial myonecrosis

Clostridium perfringens Jaundice,abscess may develop. Exotoxin elaborated by the bacterium.

Actinomycosis

 Actinomyces israelii Jaundice,abscess may develop.

Metastatic spread from other abdominal sites.

Enteric fever Salmonella typhi Hepatic damage by S. typhi  Mediated by bacterial endotoxin  

Mesenteric adenitis Yersinia enterocoliticaThe subacute septicemic form of the disease result in abscess.

Fitz hugh curtis syndrome

Neisseria gonorrhaeHepatic complication of gonococcal infection.Perihepatitis- Direct spread of the infection from the pelvis.

Brucellosis Brucella suis, Brucella abortus, Brucella melitensis,Brucella ovis Jaundice , hepatosplenic abscesses.

Melioidosis

Burkholderia pseudomallei 

Multiple abscesses in liver.

Q Fever  Coxiella burnetii( obligate intracellular bacteria)

(granulomatous) hepatitis.

Oroya Fever

 Bartonella bacilliformis  Jaundice, hepatosplenomegaly and Centrilobular necrosis of the liver .

                        Bacillary Angiomatosis

Bartonella henselae, Bartonella quintana Peliosis hepatis or blood-filled cysts (immunodeficiency states).Infection frequently is associated withexposure to cats.

 Ehrlichiosis

Ehrlichia Chaffeensis, Ehrlichia Ewingii ( obligately intracellular pathogens  belongs to rickettsiaceae family).

Focal necrosis, fibrin ring granulomas, and cholestatic hepatitis. Liver injury is attributable to proliferation of organisms withinhepatocytes and provocation of an immune response.

Leptospirosis

Leptospira interrogans

Icteric leptospirosis-hepatic involvement.

Severe form with multi-organ involvement- Weil's disease. ( hepatorenal damage)

Lyme Disease

Borrelia burgdorferi(Tick-borne spirochete).

Acute hepatitis as a manifestation of reactivation  

Syphilis Treponema pallidium Hepatic lesions are common.

Hepatic Tuberculosis

Mycobacterium tuberculosisMycobacterium avium intracellulare ( AIDS )Tubercle bacilli reach the liver by way of hematogenous dissemination .

protozoa

Hepatic sinusoidal lymphocytosis(malaria)

P. falciparumMixed infection with P. vivaxRepeated exposure to malaria (aberrant immunologic Response)

Overproduction of B lymphocytesCirculating malarial antibodyAn increased levels of circulating immune complexes.

Visceral leishmaniasisLeishmania donovaniInfective form- flagellated promastigotesHepatocyte necrosisComplications of chronic liver disease are rare.

Amoebic liver abscesses

Entamoeba histolytica

Infective form - cystDefinitive host - man

Source of infection- cyst passing chronic patient or asymptomatic carrier.Mode of transmission-oral-fecal routeIntestinal lesions can metastasize to various other organs,commonestbeing liver(hepatic amoebiasis).Necrosis of liver cells leading to abscess formation which is typicalanchovy sauce in appearance.

Helminthic diseases

Toxoplasmosis

Toxoplasma gondii Primary host - cat Intermediate host - human Uptake of cyst by inhalation, followed by ingestion . Disseminated infection of liver occurs resulting in hepatomegaly.

Hyperinfection syndrome

Strongyloides stercoralis Common - immunocompromised patients. Infective form - filariform larvae. Route of entry - intact skin,lungs,intestine. Dissemination of filariform larvae into tissues(liver) that usually are not infected.

TrichinosisTrichinella spiralisMode of transmission - raw or undercooked pork bearing larvaeRoute - in the small intestine, penetrate the mucosa, and disseminatethrough the systemic circulation to other organs and liver resulting injaundice.

Hepatic CapillariasCapillaria hepatica  Mode of infection - ingesting soil, food, or water contaminated withembryonated eggs. Larvae released in the ceacum penetrate the intestinal mucosa, enter theportal venous circulation, and lodge in the liver.

Adult worms disintegrate, releasing eggs into the hepatic parenchymaand producing an intense inflammatory reaction.

Ectopic Ascariasis

Ascaris lumbricoides Mode of infection - contaminated food ,drink or fingers. Definitive host - man Infective agent - embryonated egg Site of localisation - small intestine Migration of adult worm to liver causes liver abscess

Toxocara canis,Toxocara catisMode of transmission - contaminated food or soil.Route of transmission - intestine,penetrate the wall ,carried in blood toliver forming nodules.

Viseral larva Migrans

Echinococcosis (hydatid cyst)

Echinococcus granulosus Definitive host - dogIntermediate host – man

Mode of infection - contaminated food and drink Infective agent - embryonated eggs.

The eggs hatch in the small intestine and liberate oncospheres that penetrate the mucosa and migrate via vessels or lymphatics to distant sites, liver being the most common destination (70%) and forms cyst known as hydatid cyst.

The early stage of infection is generally asymptomatic. As the cystenlarges, symptoms of a space-occupying lesion develop.

The great danger lies in the rupture of the cyst causing the escape ofhydatid fluid and hydatid sand anaphylactic shock escapedprotoscolices can form new hydatid cysts.

E. multilocularis is highly invasiveInfection leads to formation of solid masses in the liver .E. vogeli has clinical features intermediate between those of infectionscaused by the other two species and is characterized by multiple fluidfilled cysts.Superinfection of the hepatic cysts can lead to pyogenic liver abscesses in up to 20% of patients with hepatic disease.

Schistosomiasis (Bilharziasis)

Schistosoma mansoni, S. haematobium,S.japonicum.Infective form - cercariaeSource of infection - contaminated freshwater

Intermediate host-Snail Definitive host -humansHepatic granulomas

Its due to immunologic reactions to Schistosoma eggs trapped in tissues.Antigens released from the egg stimulate a granulomatous reaction involving T cells, macrophages, and eosinophils

Clonorchiasis Clonorchis sinensisSource of infection - raw or inadequately cooked fresh fish infected withmetacercariae of clonorchis.Definitive host - manFirst intermediate host - snailSecond intermediate host - crypinoid fishHepatic parenchymal damage

Fasciolosis

Fasciola hepatica,Fasciola giganticaDefinitive host - humansIntermediate host - freshwater snailsInfective form - metacercariaReservoir host - sheepSource of infection - raw aquatic vegetation contaminated with encystedmetacercaria such as lettuce and green salad.Painful enlargement of liver, obstruction and inflammation of bile duct .

Fungal diseases

Disseminated Candidiasis

Candida species Predisposing factor - immunocompromised persons,leukemic patients

undergoing high-dose chemotherapy. Hepatic involvement.

Disseminated histoplasmosis 

Histoplasma capsulatum

  Portal of entry - respiratory tract . Predisposing factor- Severely immunocompromised persons . The liver can be invaded in both acute and chronic progressive disseminated histoplasmosis

Viruses

Hepatitis A

RNA Virus

Source of infection - Faeces

Route of transmission - Fecal-oral

Infects the liver, causing inflammation. Although it may cause acute

symptoms, it rarely results in severe or chronic liver disease. 

Hepatitis B

DNA Virus

Source of infection-Blood/blood derived body fluid

Route of transmission- : parenterally, low vertical and sexual transmission

Hepatocellular necrosis occurs due to the body’s reaction to the virusrather than due to the virus itself

Hepatitis C (the silent epidemic)

RNA virus

Source of infection-Blood/blood derived body fluid

Route of transmission- Parenterally, low vertical and sexual transmission

Cirrhosis

Hepatocellular carcinoma

Hepatitis D

Defective virus which requires hepatitis B as a helper virus in order toreplicate.Infection therefore only occurs in patients who are already infected withhepatitis B.

Increased severity of liver disease in hepatitis b carriers.

Hepatitis ERNA virus similar to hepatitis A

Source of infection - faecesRoute of transmission-Fecal-oral

Cause of enterically transmitted non-a,non-b hepatitis(acute).Fulminant hepatitis in pregnant women.

Hepatitis GRNA virus

0.2% acute hepatitis

Exact role not known, probably not a pathogen