Microorganisms Flashcards

Question

What type of virulence factors help Uropathogenic Escherichia coli?

Answer 1

Siderophores - used to scavange iron from the envirnment

Answer 2

Gram negative cocci Carried in nasopharynx of approximately 5- 10% population Note Meningococcemia – sepsis

Answer 3

1. Binding and entry at the nasopharynx 2. Enters blood stream 3. Cross blood brain barrier to enter CSF

Answer 4

Hospitalized patients at great risk for new infections: Host factors- 1. Vulnerable- immunocompromised, 2. Impaired swallowing (e.g. stroke/intubation etc), surgical procedures 3. Breach in physical defences- e.g. cannulation, urinary catheterisation. 4. Prosthetic material 5. Loss of microbiome- antibiotics 6. Loss of cellular immunity- e.g. chemotherapy, underlying illness.

Answer 5

Pneumonia- **S. pneumoniae** initially then greater variation e.g. Gram negative bacteria. Surgical site infections - **S. aureus** including MRSA but also other pathogens Urinary tract infections- **E. coli** but also other pathogens e.g. proteus etc. **C. difficile** infections - loss of microbiome in bowel.

Answer 6

Yes, humans are not sterile - we have many symbiotic relationship that are important for life to function We provide nutrients, space, temperature Microbes help digest food, produce proteins, maintain the immune system and compete against each other for the Niche Some sites are heavily colonised by microbes (GI tract), others are significantly more sterile (Brain, heart, liver, Bone & bone marrow and Joints) - presence of bacteria is indicative of illness

Answer 7

Nope - technically any microorganism capable of causing disease is a pathogen Hence, although in health many commensals are beneficial under different circumstances, i.e. in disease, they may become pathogenic. Pathogenicity is not black/white – depends on site, timing, quantity, etc. Even for obligate pathogens - several factors need to fall into place in order to cause disease

Answer 8

**Commensals**: Commensal microbes act on the host's immune system to induce protective responses that prevent colonization and invasion by pathogens **Obligate**: Obligate pathogens require a host to fulfil their life cycle **Zoonotic**: A microorganism that is a colonizer of pathogen in animals - Transmitted to humans via direct vector or with direct contact with the animal or its products **Environmental**: A microorganism able to cause disease transmitted to humans from an environmental source such as water or soil

Answer 9

1. Escape from the host or reservoir - inside our body, animals, environmental sources, etc. 2. Transport to the new host - droplets, vector - mosquitos, direct contact, airborne, etc. 3. Entry - causing clinical infection 4. Escape - further spread

Answer 10

Incubation times time from infection to symptom development – highly variable Range: few hours (food poisoning) to decades: Tuberculosis The infected host can be infectious

Answer 11

Spread through the body 1. Blood 2. Lymph and blood 3. Nerves 4. Cerebrospinal fluid

Answer 12

Portal of exit is the path used by the pathogen to leave the host Usually corresponds to the **site where the pathogen is located**

Answer 13

Strategies for evading host defenses: 1. Concealment of antigens 2. Intracellular persistence 3. Colonizing privileged sites 4. Concealment by taking up host membranes or molecules

Answer 14

1. Common in students 2. Symptoms - generalised headache (not helped with analgesics), nauseated, feeling uncomforatble, muscle aches and feeling hot/shivery 3. Non-Blanching rash 4. Examination - flushed, cold, tachycardic, clear chest and neck stiffness

Answer 15

Case - Peter Symptoms - two week history of fever and shortness of breath. PMH: IVDU, unemployed and no allergies Blood cultures - gram-positive cocci Echocardiogram - vegetation in the aortic valve - bacterial colonising the valve region

Answer 16

Abigail - 60 year old - Presented with a one week history of fever, back pain (kidneys) - She also has had pain while passing urine and frequency. - She is diabetic (increased risk of UTI) E. coli - common cause of urinary tract infections - Lower urinary tract infection (bladder and urethra) - Upper UTI (ascending to ureter/kidneys) – pyelonethritis, renal abscess.

Answer 17

Breast milk - Rich in human milk oligosaccharides (HMO) Bifidobacterium longum infantis contains all the enzymes required for HMO digestion This releases short chain fatty acids (SFCA), which then provide energy for intestinal cells and promotes production of anti-inflammatory molecules B. infantis also produces sialic acid required for brain development

Answer 18

1. Anything we come into contact with - share microbiota with your household, environment, pets and food 2. Altered by antibiotics 3. Reduces in variety as we age

Answer 19

Resistant starch broken down by the microbiome to SCFAs (fermentation) Produces: Butyrate, pyruvate, acetate Impact of SCFAs on physiology: 1. Butyrate main energy source for enterocyte 2. SFCAs have anti-inflammatory and anti-tumour properties 3. SFCAs stimulate production of protein YY (PYY) - Induces satiety

Answer 20

Healthy microbiome plays an important role in niche competition and nutrient depletion from invading bacteria - e.g. there is a heavy competition for colonising the epithelial surface/attachment to cell surface receptors Ways that the microbiome protects... 1. SFCAs inhibit virulence gene expression and lower pH to below optimal growth conditions 3. Microbiota produce bacteriocins - Directly kill Salmonella, Listeria, Clostridium

Answer 21

Gut brain axis - Neural connections involving central, autonomic and enteral nervous system Strong links between GI disease and brain disease, e.g. 1. Depression, anxiety and GI symptoms 2. Irritable bowel syndrome Potential involvement in CNS disorders 1. Parkinson’s 2. Alzheimer Disease 3. Multiple Sclerosis

Answer 22

Secondary bile acids have shown to have numerous impacts: Shown to activate cell surface and nuclear hormone receptors - Hepatocytes, Intestinal cells, Inflammatory cells Important in maintaining normal health: 1. Reduce gut inflammation 2. Regulate synthesis of bile acids 3. Activate vitamin D receptor Also shown to stimulates glucagon like peptide-1 - Increases insulin secretion, reduces glucagon secretion

Answer 23

A number of studies has identified associations between altered microbiome and disease: 1. Obesity 2. Type 2 diabetes mellitus 3. Inflammatory bowel disease 4. Colon cancer 5. Asthma

Answer 24

Many reasons to consider the microbiome to be important in obesity 1. Bacteria involved in energy production 2. Stimulates production of mediators that alter insulin and glucagon production 3. Involved in satiety 4. Regulate intestinal integrity and inflammation Supported by germ-free mice and microbiome transfer studies. Human studies - Lean subjects have more bacteroidetes and it is linked with more weight loss

Answer 25

Two major conditions 1. Ulcerative colitis: affects the colon 2. Crohn’s disease: can affect any part of gut from mouth to anus Both have chronic inflammation, relapsing and remitting - Usually treated by suppressing the immune system Changes in the microbiome observed 1. Decreased microbial diversity 2. Some bacteria are decreased - Firmicutes, some Clostridium species 3. Some bacteria are increased Enterobacteriaceae, including E.Coli Facultative anaerobes (increases due to increased nitrosative and oxidative stress)

Answer 26

Colon cancer linked with obesity, insulin resistance, red meat consumption, protected by fibre intake and increased exercise - could the microbiome be mediating these changes Microbiome differs in patients in colon cancer - Cause or effect? 1. Seven bacterial species consistently elevated - Bacteroides fragilis-produces a tumorigenic toxin 2. Large number of bacteria are reduced 3. Also changes in the virome

Answer 27

Metabolic output of the microbiome likely to alter risk of development and progression of colorectal cancer

Answer 28

Nope not really - maybe in type 2 diabetes.

Answer 29

Helicobacter pylori can be found in the gastric mucosa (attached) - Most common chronic bacterial infection in humans - It is estimated that 50% of human population is infected - Most commonly acquired in childhood It is able to survive in the gastric mucosa as it... - Has the enzyme urease which breaks down urea to produce ammonia which neutralizes gastric acidity

Answer 30

1. Attaches to the gastric mucosa 2. Disrupts gastric mucus layer leading to exposure of mucosa to acidic environment 3. Promotes inflammatory immune response 4. Causes chronic gastritis (inflammation of the stomach lining) - This may be asymptomatic, But can lead to peptic ulceration! - Leads to an overall increased risk of stomach cancer

Answer 31

Often asymptomatic but may cause bleeding leading to anaemia Symptoms 1. Upper abdominal pain 2. Indigestion 3. Heartburn 4. Occasionally they perforate causing severe pain

Answer 32

Investigation 1. Urea breath test - Give carbon-14 labeled urea and detect labelled CO2 in breath 2. Stool antigen test 3. Endoscopy and biopsy Treatment 1. Proton pump inhibitor (e.g. lansoprazole) - Suppress acid secretion 2. Antibiotics 7 day course Amoxicillin and clarithromycin or metronidazole

Answer 33

Clostridioides difficile - known for causing that causes diarrhea and colitis (inflammation of the colon) Importantly, it is associated with antibiotic associated colitis: Antibiotic use results in a change in the microbiome. Given that C. Difficile is resistant, it is able to proliferate and cause disease - produces a toxin that damages the epithelium (Toxin A & B)

Answer 34

Prevention: 1. Choice of antibiotics - Some antibiotics are more likely to cause C. Diff infection e.g. ciprofloxacin, clindamycin, cephalosporins 2. Infection control measures Treatment 1. Most cases respond to antibiotic treatment e.g. **vancomycin** or **metronidazole** Note - some are resistant and/or recurrent 2. New treatment - fecal mass transplant - transplanting healty stool into a recipient - reserved for patients with recurrent disease - Delivery via - Oral capsule, nasojejunal or nasoduodenal tube, enema and colonoscopy

Answer 35

Direct contact: 1. Skin-to-skin contact, kissing, and sexual intercourse. Example a) Infectious mononucleosis (CMV) - “Kissing disease” b) Methicillin-resistant S. aureus (MRSA ) 2. Contact with soil or vegetation harbouring infectious organisms. - Hookworm contact with contaminated soil - Clostridium botulinum

Answer 36

Direct transmission - Droplet spread: Spray of relatively large, short-range aerosols produced by: sneezing, coughing, and even talking. Transmission by direct spray over a few feet, before droplets fall to the ground. Examples - Meningococcal sepsis - Bordetella pertussis – Whooping cough

Answer 37

Indirect transmission - Airborne transmission: Infectious agents are carried by dust or droplet nuclei suspended in air. Droplet nuclei: Dried residue of less than 5 microns in size. It can remain suspended in the air for long periods of time and could be blown over long distance Examples Measles Tuberculosis

Answer 38

Indirect transmission – Vehicles Vehicle passively carries a pathogen: by providing the appropriate environment in which the organism grows and multiplies Examples: 1. Food: Hepatitis A virus, norovirus 2. Water: Entamoeba histolytica, Legionella pneumophila 3. Biologic products (blood): HIV, Hepatitis B and C virus 4. Fomites (inanimate objects uch as handkerchiefs, bedding, or surgical scalpels). 5. Improperly canned foods: botulinum toxin by Clostridium botulinum.

Answer 39

Indirect transmission - Vectors: Mosquitoes, fleas, and ticks may carry an infectious agent through: 1. Mechanical means: » Fleas – Yersinia pestis – agents carrying bubonic plague 2. Biologic transmission: » Malaria: Plasmodium matures in an intermediate host before it can be transmitted to humans

Answer 40

**Controlling or eliminating the agent at the source**: 1. Antimicrobial treatment 2. Isolating the infected patient 3. Soil might be covered **Mode of transmission**: 1. Water treatment 2. Hand washing 3. Modification of air pressure / quality – filters 4. Controlling vectors – mosquitoes **Portals of entry**: 1. Use of Personal protective equipment (PPE): masks, gloves 2. Bed nets in zones of malaria **Increasing host defenses**: 1. Vaccination 2. Prophylactic use of medication - antimalarials 3. Herd immunity

Answer 41

The aim of the IPCT is to **minimise the risk of infection acquisition or transmission** through a range of activities: 1. Surveillance 2. Policy & guidance 3. Education & training 4. Advice & clinical review 5. Audit & quality improvement

Answer 42

Duty to contact public health within three days if there is an infectious disease Urgency of the matter is dependant on... 1. The nature of the suspected disease 2. Ease of transmission 3. Patient's circumstances 4. Additional guidance provided by Scottish Ministers

Answer 43

Immunity is the ability of the body to protect itself from infectious disease: It can be.... Innate or Acquired Acquired 1. Active: - Involves cellular and antibody responses - Produced by patient’s own immune system – long lasting - Can be acquired by natural disease or vaccination 2. Passive: Protection by transfer of antibodies from immune individuals across the placenta or from transfusion of blood or blood products such as immunoglobulin