PATHOGEN“A pathogen is a microbe or microorganism such as a virus (such as HIV), bacterium (such as staph), prion, or fungus (such as yeast) that causes disease in its animal or plant host”.First devised in 1880.
MAJOR HUMAN PATHOGENSBacillus anthracisClostridium botulinumBartonella spp.Spanish influenza virusYersinia pestisMycobacterium leprae
PATHOGENESIS“The pathogenesis of a disease is the mechanism by which the disease is caused. The term can also be used to describe the origin and development of the disease and whether it is acute, chronic or recurrent”.
OPPORTUNISTIC PATHOGEN “An infectious microorganism that is normally a commensal or does not harm its host but can cause disease when the host’s resistance is low”. OPPORTUNISTIC INFECTION “An opportunistic infection is an infection caused by pathogens, particularly opportunistic pathogens”.
OPPORTUNISTIC CONDITIONS When the immune system isn’t working properly, normal flora can overpopulate or move into areas of the body where they do not normally occur. When the balance of normal microbes is disrupted, for example when a person takes broad spectrum antibiotics. Disease can result when normal flora are traumatically introduced to an area of the body that is axenic or that they do not normally occur in.
Causes of Immunodeficiency Malnutrition Chemotherapy for cancer Skin damage Medical procedures Pregnancy Immunosuppressing agents for organ transplant recipients The concomitant presence of certain underlying diseases such as cancer, diabetes, cystic fibrosis Side effects of certain medical therapies and drugs such as corticosteroids Infection with immunity-destroying microorganisms Age, both old and young
REFERENCES TO STUDY OPPORTUNISTIC BACTERIAThere are two main references to study opportunistic bacteria:1. Opportunistic bacteria with reference to the site change. Example E.coli2. Opportunistic bacteria with reference to the immunocompromised condition. ExampleAIDS and its related opportunistic bacteria.
Pseudomonas aeruginosa as anopportunistic pathogen member of the Gamma Proteobacteria Gram-negative, aerobic rod Belongs to family Pseudomonadaceae. Oxidase-positive
Infections by Pseudomonasaeroginosa urinary tract infections, respiratory system infections, dermatitis, bacteremia, bone and joint infections, gastrointestinal infections
Infections are caused particularlyin : Patients with severe burns cystic fibrosis cancer AIDS Pseudomonas aeruginosa is primarily a nosocomial pathogen.
Characteristics contributing toits success as opportunisticpathogenNatural habitat Ubiquitous in soil and water, and on surfaces in contact with soil or water Actively swimming by means of its flagellum.Metabolism Respiratory and never fermentative Can grow in the absence of O2 if NO3 is available as a respiratory electron acceptor
Nutritional requirements Minimal nutritional requirements Simplest medium for growth consists of acetate as a source of carbon and ammonium sulfate as a source of nitrogen.
Optimum temperature for growth 37 degrees Able to grow at temp as high as 42 degreesTolerance to physical conditions Resistant to high conc. of salt, dyes, weak antiseptics and antibiotics
Resistance to antibiotics and phagocytes Naturally resistant to antibiotics due to the permeabiliity barrier afforded by its Gram- negative outer membrane. Living in association with the bacilli, actinomycetes and molds; resistant to their naturally-occuring antibiotics. Slime layer; anti-phagocytic effect
Pathogenesis of PseudomonasaeruginosaComposed of three distinct stages bacterial attachment and colonization; local invasion; disseminated systemic disease.
Attachment and colonizationIt uses Flagella Pilli Exopolysaccharide (alginate or slime)
InvasionProduce extracellular enzymes and toxins that Break down physical barriers Damage host cells and immune defence.Two exocellular proteases involved are: Elastase Alkaline proteaseSome more proteins are; hemolysins and cytotoxins
Dissemination Involves spread of infection to other parts Mediated by same extracellular products that produce localized infection
Escherichia coli (E. coli ) is aGram-negative,rod-shaped andfacultative anaerobic bacteriumCommonly found in the lower intestine of warm-blooded organisms (endotherms)Help in food digestion.
E.coli as an opportunisticbacteria:- Although it lives in a healthy micro flora of a human body, but only in specific situation, when it arrive from intestine to other organs and tissues, unfortunately, it can cause a very serious infection and illnesses. The most frequent are urinary tract and sexual organs infections.
Infections:-Virulent strains of E. coli can cause Gastroenteritis (inflammation of stomach and small intestine) Urinary tract infections and Neonatal meningitis (colonisation of new born’s intestine)
In rarer cases, virulent strains are also responsible for Hemolytic-uremic syndrome Peritonitis (inflammation of peritoneum) Mastitis (inflammation of breast tissues) Septicemia (inflammation of whole body) and Gram-negative pneumonia.
Classification of E.coli:- Enterotoxigenic E. coli (ETEC) diarrhea (without fever) in humans, pigs, sheep, goats, cattle, dogs, and horses Enteropathogenic E.coli (EPEC) diarrhea in humans, rabbits, dogs, cats and horses Enteroinvasive E. coli (EIEC) found only in humans Enterohemorrhagic E.coli (EHEC) found in humans, cattle, and goats Enteroaggregative E.coli (EAEC) found only in humans
Serotypes Pathogenic E.coli strains can be categorised as follows:- O antigen: part of lipopolysaccharide layer K antigen: capsule H antigen: flagellin F antigen: MR fimbriae (rare) For example E.coli strain EDL933 is of the O157:H7 group.
Symptoms:- Bad stomach cramps Belly pain Vomiting Diarrhea, sometimes with blood in it Painful urination Children are more likely than adults to have symptoms. 3 or 4 days
Causes of infection:- E. coli in food During meat processing. Meat is not cooked to 160°F (71°C). Food come in contact with raw meat E. coli from person-to-person contactWhen an infected person does not washhis hands well after a bowel movement.
E. coli in water Human or animal feces infected with E. coli sometimes get into lakes, pools, and water supplies. People can become infected when a contaminated city or town water supply has not been properly treated with chlorine or when people accidentally swallow contaminated water.
Precautions:- Cook all types of beef to at least 160°F (71°C). Wash any tools or kitchen surfaces that have touched raw meat. Wash your hands properly after using washroom. Use only pasteurized milk, dairy, and juice products. Use only treated, or chlorinated, drinking water.
Summary In summary, E. coli is an opportunistic pathogen that can produce a variety of symptoms in its host. However, if precautionary measures are taken, E. coli infections can be limited or eliminated.
GENERAL INTRODUCTION OF AIDS Acquired immunodeficiency syndrome (AIDS) Human immunodeficiency virus (HIV) Retrovirus CD4 T cells, macrophages and dendrite cells. Cellular immunity is lost. leaves individuals susceptible to various opportunistic infections
Opportunistic infections association with HIV and AIDS HIV does not kill anybody directly. People with HIV can get many infections called opportunistic infections. Many of these illnesses are very serious, and they need to be treated and some can be prevented. People with advanced HIV infections are vulnerable to infections and malignancies. Opportunistic Infections are caused by various pathogenic microorganisms such as bacteria, fungi, virus and parasites.
OPPORTUNISTIC BACTERIAL PATHOGENS Bacterial pathogens are associated with the significant proportion of morbidity and mortality. The following genera of pathogens are most common in person infected with HIV. Salmonella Campylobacter Shigella Flavobacterium Staphylococcus Haemophilus Streptococcus Mycobacterium Treponema Nocardia Yersinia Pseudomonas Rhodococcus
Campylobacterr Campylobacter Campylobacter is a genus that belongs to Family Campylobacteraceae of Kingdom Bacteria. Twisted bacteria with spiral or corkscrew appearance. These are motile with either unipolar or bipolar flagella Gram-negative. Microaerophilic Oxidase positive test.
Campylobacter &AIDS Campylobacter infections are among the most common bacterial infections in humans. Diarrhoea Bacteremia C. jejuni is usually the most common cause of community-acquired inflammatory enteritis. Symptoms Includes abdominal pain, cramping, dehydration and fever.
Flavobacterium Flavobacterium is a genus that belongs to Family Flavobacteriaceae. Gram-negative bacteria. Rod shaped bacteria They maybe motile or non-motile Found in soil and fresh water
Flavobacterium & AIDS Flavobacterium spp. may play a pathogenic role in patients with advanced HIV disease Endocarditis Pneumonia Bacteremia F. meningosepticum is the most imp example of this genus.
Haemophilus Haemophilus is a genus that belongs to the Pasteurellaceae family Gram-negative bacteria. Pleomorphic bacteria (wide range of shapes they occasionally assume) Aerobic or facultatively anaerobic. The genus includes commensal and pathogenic organisms
Haemophilus & AIDS Meningitis is one of the most common bacterial infections occurring in persons infected with HIV caused by Haemophilus influenzae, Pneumonia Upper respiratory tract infections, such as otitis and sinusitis Genital infections. Recently HIV infection increases the risk of acquiring invasive H. influenza infection.
OPPORTUNISTIC BACTERIALPATHOGENS Oppertunistic infections are also caused by abnormal immune system of host Because of this reason such infections are most common in person infected with HIV. We will discuss the effect of five bacterial genera as oppertunistic pathogens due to weak immune system of the host
Nocardia Nocardia is a gram positive actinomycete. Human infection is rare and contracted through inhalation. Infection is more common among immunocompromised patients, especially those with impaired cell mediated immunity. The patient may have other infections e.g tuberculosis.
Rhodococcus Pneumonia is the most common manifestation of Rhodococcus infection. Very most of cases originally reported were in patients who were immunocompromised due to malignancies, immunosuppressive. Pulmonary infection occurs by the inhalation of the Rhodococcus particularly Rhodococcus equi
Salmonella Salmonella infection has an increased incidence in HIV infected populations. Salmonellosis and bacteremia are occurring at an increased rate in person with HIV. A characteristic feature of Salmonellosis in AIDS is the relapses that occur during appropriate antibiotic therapy. S. typhimurium and S. enteridis are the two most common serotypes isolated from the blood of patients with AIDS in the United States
Yersinia Yersinia is responsible for causing plague in peoples infected with AIDS Y. pestis is a gram-negative, facultatively aerobic rod it is primarily a rodent pathogen. The vactor for this bacterium is a rat flea , Xenopsylla cheopis. Rat flea is actually an insect which transmits that bacterium between two hosts.
Mycobacterium Tuberculosis is an unquestionably, the most potent opportunistic bacterial infection complicating HIV infection caused by Mycobacerium tuberculosis. It is responsible for more than 2 million deaths and 8 million new cases annually In India, tuberculosis is the most common opportunistic infection. About a third of the HIV positive population worldwide is coinfected with M. tuberculosis.
General characteristics facultatively anaerobic Non-lactose fermenting non-motile Infection spread from human to human via the fecal-oral route major cause of diarrheal disease HIV-infected persons are at increased risk for infection
StaphylococcusTaxonomy Genus Staphylococcus Family StaphylococcaceaeMorphology spherical 1 µm in size thick cell wall Gram-positive
General characteristics facultative anaerobe immobile Coagulase Positive Are resistant to 122 °F temperatures high salt concentrations (<10%) drying Infection common flora: skin, nasal cavity, pharynx, gastrointestinal tract, genitourinary tract
A bacteremia may result in seeding other internal abscesses, other skin lesions, or infections in the lung, kidney, heart, skeletal muscle or meninges. common cause of community-acquired (CA) or hospital-acquired (HA) bacterial skin and soft- tissue infections among patients with HIV infection.
Pseudomonas aeruginosa Taxonomy genus Pseudomonas family Pseudomonadaceae Morphology rod-shape 1-5 µm long and 0.5-1.0 µm wide monoflagellated
gram-negative Infection it often colonizes immuno compromised patients, like those with cystic fibrosis, cancer, or AIDS . takes advantage of an individuals weakened immune system . produces tissue-damaging toxins. causes urinary tract infections, respiratory system infections, dermatitis, soft tissue infections, bone and joint infections, gastrointestinal infections .
Streptococcus pneumoniae Taxonomy Genus Streptococcus family Streptococcaceae. Morphology Cocci 0.5-1.2um often Arranged in Pairs or Chains Gram-positive
General characteristics Non motile Carbohydrates fermenters Infection spontaneously cause disease in humans, monkeys, rabbits, horses, mice and guinea pigs. Patients with HIV infection are at increased risk for bacterial pneumonia
Treponema pallidum Taxonomy genus Treponema family Spirochaetaceae. Morphology spiral-shaped 0.2 µm in diameter and 6- 15 µm in length Gram negative
General characteristics mobile endoflagella Infection transmitted by direct contact Infection is initiated when T. pallidum penetrates dermal micro abrasions or intact mucous membranes. Neurosyphilis is most common in patients with HIV infection. headache, meningeal irritation and nerve abnormalities.