Medical microbiology Flashcards
What is epidemiology the study of
he nature, distribution, causation, transfer, prevention and control of disease (infectious/microbial in this case)
How many deaths did infection cause
1.68 billion
What vaccinations were made last century
Measels, HIV/AIDS/ hepatitis/ influenza pandemics/ respiratory viruses/ smallpox
What vaccinations have been made now and are planned to in the future
HIV/AIDS, influenza, SARS and ebola virus, Covid-19
Major global disease examples
respiratory - myobacterium tuberculosis.
Diarrheal - vibrio cholerae
What do infections involve
host, microorganisms and environment interactions
What are opportunistic pathogens
pathogens capable of causing damage and infection in a compromised host
What are obligate pathogens
causes damage and infection as part of its growth and replication
What are facultative pathogens
causes disease as one part of its lifecycle or when in a different host
What are commensal pathogens
induces either no damage or clinically inapparent damage to the host but may elicit an immune response
Obligate pathogen features
gram-positive, aerobe, phylum: actinobacteria. e.g., TB
Facultative pathogen features
gram-negative, facultative anaerobe, class: gammaproteobacterial. e.g., vibrio cholerae
Opportunistic pathogen features - pseudomonas aeruginosa
gram negative, phylum: proteobacteria, class: gammaproteobacteria.
Opportunistic pathogen features - staphylococcus aureus
gram positive, phylum: firmicutes, class: bacilli
commensal pathogen features
gram positive, phylum: firmicutes, class: bacilli e.g., epithelial or gut bacteria. Lactobacillus acidophilus
Example of how cf lung infections are diagnosed
sputum/cough swab -> microbial growth -> pure culture -> pathogen identification -> antibiotic susceptibility -> treatment and management
how can a pathogen be identified
species PCRs, sequencing, strain typing, MALDI-TOF MS
Issues to consider in medical microbiology
respiratory sample types, microorganisms present, growth media, multiple pathogens, indentification tests, useful antibiotics?, treatment strategies, pathogenic mechanisms
What knowledge do we have about different strains
knowledge of clonality or genetic identity - ribotyping, macro restriction and PFGE, PCR-fingerprinting, DNA sequencing
What are species
consist of large numbers or strains which share similar phenotypic and genetic properties (16S rRNA gene (>97% identity), gyrB or recA gene > 70% DNA-DNA hybridisation, average nucleotide identity)
What can identify a meroclone and a clone
whole-, core-, and accessory- genome multilocus sequencing type
What can identify a strain
ribosomal multilocus sequencing type
What can identify a species, lineage or clonal complex
multilocus sequencing type
What can identify phylum, class, order, family and genus
16S rRNA sequences
What does PCR genotyping and pulsed-field gel electropheresis (PFGE) identify
define strains just below the species level. Cannot work above or below this
Multilocus sequence typing (MLST)
Initially PCR based (1988). Sequence several conserved genes. Approx. 500 bp from a PCR fragment. Define genetic linkage between strains. Globally searchable strain database
MLST identified Burkholderia, how was this useful?
Burkholderia bacteria may spread between CF patients. MLST scheme established. Allowed global strain tracking. Infection control reduced spread
What are virulence factors
molecules that assist the bacterium colonize the host
virulence factor examples
acid host colonization, host destrcution, nutrient scavenging, poisoning, intracellular entry, sndotoxin, exotoxin and adhesions
What may pathogen genomes also encode
virulence factors on mobile genetic elements
what virulence factor could clostridium botulinum encode for
neurotoxin
multiple virulence factor plasmids - E.coli
enterotoxins, haemolysins, pili, urease
genomic islands
classical pathogenicity islands e.g., uropathogenic E.coli - haemolysis, serum resistance and adhesions
Intergrative conjugative element (ICE)
e.g., Tn917 system in Enterococcus faecalis. Large conjugative transposons, mobilised by a type IV secretion system
Transposable elements (TE)
e.g., V.cholerae - cholera toxin, CTX compound transposons
Linking Burkholderia epidemiology to virulence: an epidemic strain marker
The B. cepacia epidemic strain marker (BCESM). Identified in transmissible CF strains by RAPD fingerprinting. Risk marker for potential patient – to –patient spread
what is a microbiome
“the entire habitat, including the microorganisms (bacteria, archaea, lower and higher eukaryotes, and viruses), their genomes (I.e., genes), and the surrounding environmental conditions”
What are microbiota
“the assemblage of microorganism present in a defined environment”
what is an ecological niche
the functional role on organism plays within an ecosystem
What is a commensal relationship
a relationship where one organism benefits and the other is unaffected
What is a mutualistic relationship
a mutually beneficial relationship between 2 organisms
Essential roles of the human bacteriome
- Extracting energy from food
- Producing essential vitamins
- Regulating our immune system
- Regulating our glucose levels and metabolism
- Protecting us against disease-causing microbes
Role of the bacteriome in the nose
mucus production, antimicrobial compound production
Role of the bacteriome in the mouth
aid digestion, inhibit pathogens - “colonization resistance”
Role of the bacteriome in the lungs
lubricate pulmonary tissue
Role of the bacteriome in the stomach
prevents gastric complications
Role of the bacteriome in the colon
digestion of complex carbohydrates
Role of the bacteriome in sexual organs
maintain pH, produce H2O2 to kill pathogens
Role of the bacteriome in the skin
fortify immune system, scent
What are the metabolome and what do they do
the global collection of all low molecular weight metabolites that are produced by cells during metabolism, and provides a direct functional readout of cellular activity and physiological status
Why is the microbiome important when considering pathogenicity
- Reservoir of opportunistic pathogens
- Reservoir of genes
- Source of antimicrobials and stimulatory components
- Interacts with the host
What is dybiosis
any change to the composition of resident commensal microbial communities relative to the community found in healthy individuals
Which diseases are linked to gut dybiosis
obesity, type 2 diabetes, inflammatory bowel disease, irritable bowel syndrome, allergy. Asthma, cardiovascular disease, anxiety/mood disorders
What is pathobiont
any potential pathological or5ganisms which, under normal circumstances, lives as a non-harming symbiont
how many species of bacteria are in the gut alone
> 1000
Where are samples for the microbial population usually taken from
- faeces
- urine/genital swabs
- Sputum - lung