MFD 12 Mibrobial Pathogenicity Flashcards
Learn a few famous diseases caused by an identified bacterium, and modern practices preventing another outbreak.
Explain what is meant by pathogenicity
the ability of an organism to cause disease
Explain what is meant by pathogenicity factors.
same as virulence factors, Bacterial virulence factors enable a host to replicate and disseminate within a host in part by subverting or eluding host defenses e.g. fimbria
What is an epidemological agent?
the bacterium ( the shit it produces maybe e.g. p.gingivalis and gingipains), god damn didn’t see that coming
What diseases does Staphylococcus Aureus
cause?
Staphylococcal meningitis, Impetigo
Pneumonia
What are the biological characteristics of Staphylococcus aureus
?
In the micrococcaceae family. ( spherical in shape, arranged in grape like structures, gram +)
Produces coagulase and has novobiocin resistance
grows at 15-45 degrees C
Is commensal and pathogenic,
What is the virulence factors of s. aureus
Produces coagulase and has novobiocin resistance
Who does S.aureus usually infect? and incidence?
3) describe distribution of MRSA infections
1) young children and elderly
2) 10-30 per 100,00 people per year
3) not even
What is encompased when describing the epidemiology of an organism?
for example how common it is in the
population, the prevalence of the diseases that it causes or any specific
outbreaks of disease due to the organism.
What is Staphylococcal meningitis?
Inflammation of the meninges – the protective membranes around the brain and spinal cord
What are the biological characteristics of Staphylococcus aureus
?
In the micrococcaceae family. ( spherical in shape, arranged in grape like structures, gram +)
Produces coagulase and has novobiocin resistance
grows at 15-45 degrees C
Is commensal and pathogenic,
Treatments of Staphylococcal meningitis:
1_ Antibiotics such as nafcillin, linezolid and cefazolin.
2_ Meningitis caused by methicillin-resistant strains (MRSA) must be treated with Vancomycin.
Symptoms of impetigo:
Red sore, itchy and painful, red sores burst to develop golden crust,
Treatments of impetigo:
Usually clears up within 2-3 weeks but topical antibiotics such as mupirocin but oral antibiotics may be used in more serious cases of the disease.
A more serious form can develop called Ecthyma which cause causes fluid and pus-filled sores which turn into deep ulcers.
Symptoms of pneumonia:
similar to that of the flu, and include: cough, chest pain, difficulty breathing, fever, loss of appetite
Treatments of pneumonia:
Treatments include antibiotics such as zanamivir and amantadine, as well as vaccinations to help with herd immunity
What are the virulence factors of S.aureus?
Catalase Hemolysins Coagulase Leukocidin Also produce proteolytic enzymes, hyaluronidase, fibrinolysin, lipase, ribonuclease, and deoxyribonuclease
What is the pathogenesis of toxic shock syndrome?
an exotoxin, produce by S.aureus, called toxic shock syndrome toxin-1 (TSST-1) a superantigen
Toxin recruits large numbers of T cells, culminating in a massive inflammatory response
What is the pathogensis of food poisening?
another superantigen, causes a form of food poisoning
Ingestion of toxin-contaminated food, the toxin stimulates T cells localized along the intestine, resulting in a massive T cell response and release of inflammatory mediators
Severe but short-lived diarrhea and vomiting
What is the pathogensis of food poisening?
another superantigen, causes a form of food poisoning
Ingestion of toxin-contaminated food, the toxin stimulates T cells localized along the intestine, resulting in a massive T cell response and release of inflammatory mediators
Severe but short-lived diarrhea and vomiting
What are the biological characteristics of Neisseria gonorrhoeae
?
gram -.
diplococcus (occurs as pairs of cocci, 2 spheres)
aerobic
catalase positive
modulates immune response, resides within neutrophils
fastiduous ( specific nutrient requirements)
How common is Neisseria gonorrhoeae
as an STI?
2nd most common STI,
What is the prevalence of the diseases that Neisseria gonorrhoeae causes ?
2) What concerns are there?
78 million new cases of gonorrhea in 2016 worldwide
44,500 new cases in 2017 in the UK alone
2) becoming resistant to antibiotics
What disease does neisseria gonorrhoeae cause?
gonorrhoeae
What are the symptoms of gonorrhoeae?
Just a rough idea is enough
In women – pain and tenderness in the abdominal area, heavier periods and pain when passing urine, unusual vaginal discharge
In men – pain or a burning sensation when urinating, swelling/ inflammation of foreskin and unusual discharge
Infection in the throat, eyes and rectum which can cause pain and swelling
Gonorrhoea can be passed from a mother to her baby during childbirth. Symptoms in babies include the eyes becoming red and swollen and eyes have a thick, pus-like discharge.
If left untreated, it can cause infertility.
Patients complain of an initial burning sensation in the mouth. Within 1-2days the mouth becomes acutely painful and the sub-mandibular lymph nodes enlarge. Oral functions such as speech and swallowing become very painful.
What are the virulence factors of Neisseria gonorrhoeae ?
1) Pilli – Piliated gonoccoci are usually virulent, whereas nonpiliated strains are avirulent.
2) Lipooligosaccharides (LOS)
3) Outer membrane proteins and Opa proteins e.g Porin A:
4) lgA protease
Pilli is a virulence factor of neisseria gonorrhoeae, how does it cause disease? (Pathogenic mechanism)
Pilli mediate attachment to mucosal cell surfaces and also are antiphagocytic.
Lipooligosaccharides (LOS) is a virulence factor of neisseria gonorrhoeae, how does it cause disease? (Pathogenic mechanism)
like LPS but low molecular weight form, has non-pathogenic role and also is an endotoxic and initiates host immune response
Outer membrane proteins and Opa proteins e.g Porin A, is a virulence factor of neisseria gonorrhoeae, how does it cause disease? (Pathogenic mechanism)
Mediates invasion of the epithelial cells.
lgA protease is a virulence factor of neisseria gonorrhoeae, how does it cause disease? (Pathogenic mechanism)
It hydrolyzes secretory lgA, which could otherwise block attachment to the mucosa.
What are the essential biological characteristics of Legionella pneumophila?
gram -, aerobic, fastidious, have a pilli so are motile, rod or coccoid shape, optimal temperature for in-vitro growth is 36°C
Falcultative intracellular parasite (can reproduce outside and within a cell)
Epidemology of legionella pneumophila:
1) outbreaks?
2) environment found in
1) Legionnaires’ disease , 1976, Philadelphia convention of the american legion
2) air-conditioning and water distribution systems
What diseases are caused by legionella pneumophilia?
Legionnaire’s disease
Pontaic fever
What are the symptoms of Legionnaires’ disease?
cough,shortness of breath, highfever, chest pains (as leads to pneumonia), headaches, nausea, vomiting and diarrhoea. It feels like a severe flu.
What is the treatment for Legionnaires’ disease?
antibiotics (venous), oxygen administration and respiratory ventilator. Antibiotic prophylaxis not effective
What are the symptoms of Pontaic fever?
cute, nonfatal respiratory that causes a mild upper respiratory infection. It resolves spontaneously and often goes undiagnosed
What traditional virulence factors doe L.pneumophila have?
includes lipopolysaccharide (LPS), flagella, pili, a type II secretion system , and outer membrane proteins.
What additional virulence factor does L.pneumophila have
2) What does it do?
3) How does this cause damadge to the host cell, and result in disease?
type 4 secretion system,
2) its secretes proteins when within a cell (alveolar macrophage) allowing the bacterium to exsist within a vesicle similiat to the ER,
3) this legionella containing vacoule prevents the host cell signalling for help, allowing further replication to take place
What is the essentional biology of Clostridium Difficile?
gram +, spore forming,
saccharolytic and proteolytic metabolism,
thrives in dysbiotic environemtn (where colonic microfloura have been altered)
What is the effect of the toxins TcdA and TcdB produced by Clostridium difficile
Disrupts GTPases, causing cell rounding and eventually death.
Both toxins enter the cell by endocytosis, where they are then cleaved, activating them.
Toxin A disrupts colonic mucosal cell adherence to colonic basement membrane and damages villous tips
Toxin B triggers apoptosis
They target GTPases – proteins involved in epithelial barrier function and host immune response
Both toxins stimulate monocytes and macrophages causing release of interleukin 8, resulting in tissue infiltration with neutrophils
what are the virulence factor of Clostridium difficile?
1) Produces toxin TcdA and TcdB
2) Has fimbriae/pilus (they are the same thing)
3) has adhesins
4) Colonisation upregulates genes for fermentation
What sort of hosts does clostridium difficle infect?
2) Where is there an increased incidence rate?
1) as an opportunistic pathogen, usually infects young children and elderly
2) young children and elderly
What does clostridium difficile cause?
infectious diarrhoea
Why would you prescribe metronidazole or vancomycin for C.diff infections? Which one would you use?
. Although neither drug has clearly been superior in head-to-head comparisons, some clinicians feel that vancomycin is the “stronger drug.” However, because of vancomycin’s expense and the ever-present worry about drug resistance, current guidelines recommend reserving vancomycin for patients with severe disease.
What conditon does Clostridium difficile cause?
2) symptoms?
Clostridium difficile colitis (infection of the colon)
2) symptoms of C. difficile colitis are fever, diarrhea, and abdominal pain
