*Microbiology 1 (Lecture 1 and 2) Flashcards by B -

List of microorganisms in increasing size

Prion proteins
Viruses
bacteria
fungi
parasites

How well did you know this?

Not at all

Perfectly

What type of names do all organisms have?

A genus name and a species name

How well did you know this?

Not at all

Perfectly

What type of diseases does prion proteins cause?

Give an example.

Transmissible Spongiform Encephalopathies (brain infection)

Mad cow disease (Crutzefelt Jacob Disease)

How well did you know this?

Not at all

Perfectly

Problem with prion proteins?

Cannot be reliably removed by sterilisation

How well did you know this?

Not at all

Perfectly

What type of organism is a virus?

What is it surrounded by/

"obligate intracellular parasite"
A capsomere (protein coat)

How well did you know this?

Not at all

Perfectly

Diagnosis of viral infections?(3)

PCR
Cell culture
Serology

How well did you know this?

Not at all

Perfectly

Difference between the genetic material contained within viruses and bacteria?

Viruses = DNA or RNA
Bacteria = DNA and RNA (one double stranded chromosome with some genetic material sometimes stored within plasmids)

How well did you know this?

Not at all

Perfectly

What surrounds a bacteria in terms of walls, etc.?

Plasma membrane
Cell wall
Capsule (+/-)

How well did you know this?

Not at all

Perfectly

What does a bacteria use for adhesion and movement?

Adhesion: Pilli and fimbriae
Movement: Flagellae

How well did you know this?

Not at all

Perfectly

Bacterial shapes? (3)

Coccus
Bacillus
Spirochaetes

How well did you know this?

Not at all

Perfectly

Can spirochaetes be stained using the gram method?

No but they have a gram negative structure

How well did you know this?

Not at all

Perfectly

Gram stain reactions?

Gram positive = purple

Gram negative = pink

How well did you know this?

Not at all

Perfectly

Difference between gram positive and gram negative?

Gram positive cell wall contains a thick layer of peptidoglycan compared to a thin layer between the cytoplasmic membrane and outer membrane in gram negative bacteria

How well did you know this?

Not at all

Perfectly

What 2 organisms do not stain well?

Mycobacterium tuberculosis (causes TB, has a waxy coat)
Treponema pallidum (spirochaete that causes syphilis)

How well did you know this?

Not at all

Perfectly

Where in the body is there a natural bacterial flora? (5)

URT
Lower small intestine
Large intestine
Vagina
Skin (resident and transient flora)

How well did you know this?

Not at all

Perfectly

What is commensalism?

Where one organism benefits from the relationship without affecting the other (commensal is part of the normal flora)

How well did you know this?

Not at all

Perfectly

Opportunistic pathogen?

An organisms that will cause infection in an immunocompromised individual

How well did you know this?

Not at all

Perfectly

Virulence?

Degree of pathogenicity of an organism (i.e. how easily can an organism cause disease)

How well did you know this?

Not at all

Perfectly

How does bacteria replicate?
What do they require to replicate? (4)
How quickly can bacteria replicate in ideal growth conditions?

Binary fission
Food
Moisture
Correct temp. (usually 37 for human pathogens)
correct pH (about 7.4)
Every 20 minutes

How well did you know this?

Not at all

Perfectly

3 main types of atmosphere?

Aerobic (growth in presence of oxygen, many aerobic organisms will also grow in anaerobic conditions but less well)
Microaerophillic (reduced O2 and enriched with CO2)
Anaerobic (no O2, “anaerobes” are strict anaerobes)

How well did you know this?

Not at all

Perfectly

Why does bacteria make us ill?

2 types of these?

Many produce toxins (enzymes)
Exotoxin (mainly gram positive, produced side cell and exported out)
Endotoxin (mainly gram negative, part of GN cell wall)

How well did you know this?

Not at all

Perfectly

What do toxins produced from bacteria do?

Interact with cells of the immune system causing release of cytokines
Damage RBCs and WBCs, make small blood cells ‘leaky”, decrease BP, affect blood clotting and eventually lead to sepsis and septic shock

How well did you know this?

Not at all

Perfectly

What type of organisms tend to form spores?

2 examples

Gram positive bacilli (put DNA in thick coat = can’t replicate but can survive for long time)
Clostridium sp. (e.g. C. difficile)
Bacillus sp. (e.g. Bacillus anthracis)

How well did you know this?

Not at all

Perfectly

How does a spore develop? (3 stages)

Chromosome condenses
Septum forms
Calcium dipliconate accumulates

How well did you know this?

Not at all

Perfectly

Diagnostic methods for bacteria?

Microscopy (same day) Culture (48 hours) Detection of antigens (e.g. in urine) Detection of antibodies (e.g. serology) - same day PCR (same day) NAATs (detection of DNA/ RNA through nucleic acid amplification tests

Streptococcus pneumoniae causes?

Pneumonia and meningitis

Streptococcus viridans?

Endocarditis

Streptococcus pyogenes (group A strep.)

Skin (e.g. necrotising fascitis), throat infecitons (e.g. tonsillitis - if rash present = scarlet fever), (peurperal sepsis = severe life threaten infection and pregnant and post natal women)

Group B strep.?

Neonatal meningitis

Enterococcus sp.

Gut infections, UTI

Staphylococcus aureus

Wound, skin infections, bone and joint, food poisoning etc.

Coagulase negative staphylococci e.g. Staph. epidermidis

Skin commensal, IV line infections

Corynaebacterium diphtheriae

Diptheria

Diptheroids

Skin commensal

Listeria monocytogenes

Meningitis

Bacillus cereus?

Food poisoning

Bacillus anthracis

Anthrax

Clostridium tetani

Tetanus

Clostridium perfingens

Gas gangrene

Clostridium difficile

Antibiotic related colitis

How long does a TB culture take?

4-12 weeks

2 types of fungi?

Moulds (produce spores and hyphae (allow them to invade organic tissues) Yeasts (single cells that reproduce by budding)

Most common mould infection in humans?

Aspergillus spp (do not stain)

Most common yeast infection in humans?

Candida spp. (stain as large gram positive structures)

Difference between sterilisation and disinfection?

Sterilisation destruct and removes 99.9% of micro-organisms and spores Used for anything that will come into contact with a normally sterile area of the body Disinfection removes or destructs pathogenic micro-organisms enough to make an item safe

What might sterilisation not kill?

Prion proteins

Sterilisation methods?

Steam under pressure (autoclave) Dry heat in oven at 160 degrees for greater than an hour exposure to ethylene oxide gas Irradiation

Disinfection methods (2)?

Hot water | Chemicals (e.g. hypochlorite, chlorohexidine, Povidone iodine)

What are the genus for bacteria that are gram positive cocci?

Streptococcus spp. Enterococcus sp. Staphylococcus spp.

Which out of streptococcus and staphylococcus and enterococcus grow in chains/ clusters?

Strep, entero. = chains | Staph. = clusters

How are streptococci and enterococcus differentiated? | Are they aerobic or anaerobic?

by type of haemolysis when grown on blood agar | Aerobic (although facultatively anaerobic)

Types of haemolysis?

Alpha/ partial Beta/ complete gamma/ non-haemolytic

What happens in alpha haemolysis

Enzymes denature haemoglobin inside RBC causing greenish discolouration around colony

What happens in beta haemolysis

Enzymes (exotoxins) lyse RBC = complete clearing (most pathogenic streptococci are beta)

Which species are alpha haemolytic

streptococcus pneumoniae aka "pneumococcus" | Streptococcus "viridans" (contains many different species)

Streptococcus pneumoniae: Where is this part of the normal flora What are the majority of UK strains of this sensitive to

URT | Penicillin

Where is streptococcus "viridian's" part of the normal flora?

Vagina, bowel, URT

How to tell the difference between the 2 alpha haemolytic gram positive cocci?

Streptococcus pneumoniae tends to grow in pairs or short chains Streptococcus "viridans" grows in chains

How are beta haemolytic streptococci differentiated

Based on cell wall antigenic structure

2 types of beta haemolytic streptococci?

Group A strep aka strep. pyogenes | Group B strep.

What is the most pathogenic of all the strep. | why

Group A strep. | Produces a range of exotoxins

What antibiotics are strep A sensitive to

Penicillin and amoxicillin

What is the non-haemolytic bacteria?

Enterococci e.g. enterococcus faecalis, enterococcus faecium

Where are enterococcus normally found | When do they cause problems

In the bowel flora | When they get into normally sterile sites

what are most strains of E. faecalis sensitive to

Amoxicillin

what are the antibiotic resistant strains of E. facium called

Vancomycin resistant enterococci

What test is used to distinguish staph. aureus from all the other staphlococci

Coagulase test

What does a positive coagulase test look like

Coagulase plasma clots in bottom of test tube = staph. aureus

Are coagulase negative staph. harmful | When do they cause harm

``` Not usually (don't tend to produce toxins) Produce slime (surface polysaccharide) which allows them to stick to artificial material in the body ```

Where does staph. aureus colonise in about 30% of patients

URT

What are 2 conditions staph. aureus can cause depending on exotoxin produced

Toxic shock syndrome | Panton-Valentine leukocidin (damages WBCs)

Condition staph. aureus can cause due to enterotoxins?

food poisoning

What are staph. aureus sensitive/ resistant to flucloxacillin called?

MSSA | MRSA (meticillin resistant staphylococcus aureus)

Treatment for MSSA?

Flucloxacillin

Bacteraemia?

Bacteria in the blood stream

One of the commonest causes of bacteraemia?

Staph. aureus

Microbiology tests for infection (6)

``` blood culture urine culture faeces culture swab for puss specimen for PCR Blood for serology ```

Fever?

Temperature greater than 38

In a fever, what is released to raise the body's thermal set point What WBC is involved in creating a fever

Prostoglandins | Macrophages

What happens during sepsis?

Small blood vessels become leaky and loose fluid Lower blood volume means heart has to work harder Poor tissue oxygen perfusion means blood supply to less essential organs (e.g. skin, kidneys, liver) is shut down Blood clotting cascade activated = clotting in tiny vessels = uses clotting factors = increased risk of haemorrhage

Levels of sepsis

Sepsis Severe sepsis Septic shock