Week 2 Flashcards

Question

Bacterial structure

Answer 1

Prokaryotes: -lack membrane bound organelles e.g. nucleus They usually have a cell wall- peptidoglycan Protruding appendages: flagella, frimbriae

Answer 2

Theres many different phyla of bacteria and each has many classes and by definition a lot of individual species Classification is based on nucleic acid sequences But there’s also a large division of bacteria into 2 groups - gram negative or gram positive

Answer 3

Gram negative stain PINK: - they have doubled membranes -examples include: E.coli, Klebsiella Gram positive stain PURPLE: - they have single membranes -examples include: staphylococci e.g MRSA, streptococci

Answer 4

Varies loads Some bacteria invade cells (intracellular)- salmonella The pathology of disease depends upon: -bacterial activity -toxin production, direct tissue damage -host response -immune system

Answer 5

Exotoxins- proteins secreted by bacteria Synthesised for a number of reasons -destroy host cells -release cellular contents - allow invasion Clostridium botulinum: -food poisoning -lethal neurotoxin that causes paralysis Also the stuff used in Botox Symptoms: -facial nerve paralysis -dry mouth and throat -nausea and vomiting -abdominal distension -problem of urinating -double vision -slurred speech -tachycardia -muscle weakness

Answer 6

An endotoxin - found on gram negative bacteria Major immune stimulator- causes sepsis Only lipid A is toxic- major immune response There are many types possible- specificity caused by terminal repeat regions, salmonella >1000 types of LPS

Answer 7

Molecular motors used to swim Important in pathogenesis Often v. Immunogenic and cause inflammation Chemotaxis- can move bacteria towards or away from chemical attractants/repellants

Answer 8

Shorter and finer than flagella Several different functions: -attachment to host cells (UTIs) -host cell invasion -roles in conjugation Conjugation= transfer of plasmid DNA, this can drive AMR

Answer 9

Escherichia coli: bacteraemia, UTI, GI. Gm- often part flora Staphylococcus species: wound infection, bacteraemia. Gm+ often part of flora, MRSA Mycobacterium tuberculosis: tuberculosis Lung, 1/3 world carry Pseudomonas species: varied disease, Gm- environmental Streptococcus pneumoniae: RTI, Gm+ aerosol Campylobacter species: GI, Gm- 1 cause food poisoning Clostridium difficile: hospital acquired infections, sporulates overgrowth after antibiotic use Neisseria gonorrhoeae, N.meningitidis: gonorrhoea, meningitis, species specific tropism

Answer 10

AMR is a major global threat to everyone Routine surgery will become deadly due to infection 1.2 million deaths were attributable to AMR in 2019 New drugs hard to get approved - numbers declining over time Bacteria can become resistant fast: faster than the discovery rate, misuse is another reason for resistance The UN predicts up to 10 million deaths annually- as a direct result of AMR

Answer 11

Can be single cell or multicellular They are eukaryotic, similar to human cells Because of this it makes them harder to treat They have a cell wall that contains chitin Very few have been studied thought to be up to 1.5 million species Includes lots of useful things: -yeast -moulds -mushrooms

Answer 12

Numerous fungi can act as parasites or pathogens Large spread of human diseases caused by fungi: -simple infections EG. Athletes foot -serious, life threatening infections (eg aspergillus infection in the lungs) Thrush is the most common oral fungal infection: -caused by candida albicans ( a type of yeast)

Answer 13

Can be single cells but many grow as hyphae -cylindrical tubes which interconnect= mycelium Mycelium can be very large -armillaria ostoyae grows very large, malheur national forest in oregon 2,200acres Fruiting bodies and spores for reproduction- Can be carried on the wind

Answer 14

There are several other majors diseases that are caused by parasites Parasites can also include larger, complex organisms- worms (e.g. tapeworms) Protozoa can be intracellular or extracellular pathogens: malaria, trypanosomes Malaria is a major killer- 619000 deaths in 2021 Trypanosomiasis= African sleeping sickness, can be fatal without treatment

Answer 15

Pathogens constantly evolve due to competition with each other and in response to human intervention. E.g antibiotics -mutation rates and generation times high and short thus allowing for greater diversity and faster evolution Bacteria: anti microbial resistance= ticking time bomb for global health Fungi: anti-fungal resistance, new strains through evolution Viruses: anti- viral resistance, new epidemics/pandemics Infection control measures do work

Answer 16

Coccus: pneumonia, skin infections eg streptococcus Rods: E.coli, gut commensal, diarrhoea, bloodstream infections Comma shaped: vibrio cholerae, excessive diarrhoea Spirochete (spiral shaped): treponema pallidum, syphilus

Answer 17

Allows rapid metabolism as diffusion of nutrients is not limiting Rapid turn over of sugars, amino acids, nucleotides

Answer 18

Liquid culture: quantify growth rate, study physiology Solid media: using agar, preliminary identification, quantify number of live bacteria, isolate a pure culture Selective media: isolate specific bacteria, inhibits growth of others Differential media: ability to distinguish between different bacteria

Answer 19

Selective and differential Inhibits growth of many bacteria by the presence of bile salts and crystal violet PH indicator: neutral red, below pH 6.8= pink neutral= colourless E.coli ferments lactose- drop in pH- pH indicator turns from colourless to pink Salmonella grows on the agar but cannot ferment lactose

Answer 20

Medium needs to contain: - carbon: mostly in form of glucose or other sugars, amino acids -nitrogen: anorganic (eg ammonia, nitrate) or organic (amino acids) -sulphur: essential for the amino acids cysteine and methionine -phosphorus: required for ATP, DNA, RNA taken up as inorganic phosphate PO43- Minerals Fe2+, Mg2+, Ca2+: required for enzyme function

Answer 21

Defined medium: consists of pure chemicals very reproducible Complex medium: digests of microbial, plant and/or animal products

Answer 22

PH: most pathogens exhibit optimal growth around physiological pH 7.4 Exceptions: helicobacter pylori causes stomach ulcers, grows in stomach pH 3. Creates micro-environment with higher pH through production with ammonia and bicarbonate, releases urease enzyme that breaks down urea

Answer 23

Aerobic: many pathogens can breathe (‘microbial respiration’) most effective way to create ATP Anaerobic: do not respire oxygen, aerotolerant anaerobes: can tolerate and grow in air. Obligate anaerobes:oxygen inhibits growth or kills the cells. Many obligate anaerobes can form spores, Extremely robust structures can tolerate high heat, oxygen, UV can grow out ‘germinate’ when conditions are favourable again.

Answer 24

-Lag phase: adaptation to new environment, start up metabolism (generate ATP make new ribosomes) -Exponential phase: rapid cell growth and metabolism, cells run out of one or more nutrients and/or waste products limiting growth accumulate -Stationary phase: slow/no growth, preparation for survival (sporulation) resistance to stress, production of antibiotics to kill neighbouring cells -Death phase

Answer 25

Rapid stain by crystal violet and safranin Visualise and distinguish bacteria in 2 groups: gram-negative bacteria (pink/red) and gram-positive bacteria (purple) Procedure: - flood the heat fixed smear with crystal violet for 1 min, all cells purple -add iodine solution for 1 minute, all cells remain purple -decolorize with alcohol for 20 seconds, gram + cells are purple, gram - cells are colourless - counterstain with safranin for 1-2 minutes, gram + cells are purple and gram negative cells are pink to red Reflects fundamental differences in the bacterial cell wall Gram +: thick peptidoglycan no second membrane Gram -: thin peptidoglycan , second membrane Use for rapid identification by microscopy important differences in susceptibility to antibiotics since the second outer membrane of gram- functions as a barrier to many antibiotics

Answer 26

Many different approaches Immunological and antigen assays Molecular biology assays (PCR assays, whole genome sequencing) Growth dependent microbiology

Answer 27

Direct microscopy on clinical samples; -standard light microscope -staining Very cheap very fast, very useful in low resource setting Grow sample on agar:gold standard -determine specific biochemical traits (eg growth on different carbon sources) Challenging : not all bacteria can be grown easily, identification not always correct, takes time Analyse in a matrix assisted laser desorption/ionisation TOF (MALDI-TOF) mass spectrometer Peak pattern can be compared to extensive database, microorganism identification, proteins in colony material are positively ionised accelerated and detected -> separation by m/z mass to charge ratio

Answer 28

1. Antigen is bound to well 2.blocking agent is added 3. Sample added; if antibody is present it binds to the antigen 4. Unbound sample is washed away 5. Antihuman enzyme linked antibody is added 6. Unbound antihuman antibody is washed away 7. Substrate is added, if present enzyme converts substrate to coloured product

Answer 29

Specific components of pathogenic bacteria Proposed for the diagnosis of cerebrospinal fluid CSF for antigens of classic bacterial meningitis: latex agglutination tests Not always easy to interpret, no clear benefit over gram stain of CSF for rapid screening

Answer 30

Widely used for COVID-19 rapid testing lateral flow tests can be used to rapidly detect antigens Antigens bind to antibodies conjugated with a label Antigen is also recognised by a second antibody test Control line contains antibodies that recognises the conjugate-labelled antibodies in the test

Answer 31

Rapid amplification of DNA by polymerase chain reaction PCR Uses primers (complementary to target DNA) and dNTPs (nucleotides in DNA) and polymerase (Taq) in multiple cycles Visualise PCR products on an agarose gel in presence of dye binding to double stranded DNA separation by size can be used to identify bacteria Quantitative PCR, SYBR green binds to double stranded DNA Taqman: release of fluorescent label Taq has 5’ nuclease activity: chews up DNA in its path Advantages: rapid 4-6 hrs from clinical sample; growing bacteria on a plate takes 24 hrs. Particularly useful when culture is difficult or will take a very long time Limitation: primers determine what you will find , Solution: sequence all DNA in a sample to rapidly identify all microbes present

Answer 32

They parasitise all biomolecular aspects of life They depend on the host cell for raw materials and energy Replication can only occur within a host cell They exist as either an extracellular virion containing DNA or RNA virus genome or as nucleic acid inside the host cell

Answer 33

1. Adsorption 2. Entry 3.capsid transport to nucleus 4. Transcription 5. Translation 6. Replication 7. Capsid assembly 8. Glycosylation 9. Glycoprotein export to cell surface 10. Endocytosis of glycoprotein containing plasma membrane 11. Envelopment 12. Virus release

Answer 34

Segmented negative sense single stranded RNA virus (8 segments- code 1/2 proteins only) Each RNA segment codes for separate proteins

Answer 35

Three types of human influenza viruses A,B,C A: pandemics; infects humans, birds, pigs, horses etc B: seasonal epidemics; infects only humans C: mild respiratory illness: infects humans and pigs D: infects pigs and cattle Divided into subtypes based upon 2 viral proteins: -Haemagglutinin (H1-H18) -Neuraminidase (N1-N11) Can be classified as avian, swine or other types of animal influenza Haemagglutinin HA mediates entry into target cells binds to alpha 2,6 sialic acid Neutralising antibodies inhibit the interaction between HA and sialic acid

Answer 36

Host survival from an acute infection usually results in protective immunity Yet acute infections caused by some viruses occur repeatedly eg rhinoviruses, influenza virus RNA virus is unstable

Answer 37

Small changes in the genes of influenza virus that happen continually over time as the virus replicates Accumulate over time Eventually generate proteins no longer recognised by the immune system Neutralising antibodies to Haemagglutinin block influenza binding to cells Mutations alter epitopes in Haemagglutinin so that neutralising antibody no longer binds

Answer 38

RNA viruses must replicate their genomes using RNA polymerase RNA polymerase lacks the proofreading ability of DNA polymerase RNA viruses have a much greater mutation rate than DNA viruses RNA viruses can rapidly alter antigenic epitopes targeted by the immune system

Answer 39

Viruses can produce a large number of progeny: - in vitro a single cell infected with poliovirus can yield 10^5 virus particles -in Vivo an HIV infected person may produce 10^9 virus particles/day a hepatitis B infected person up to 10^11 virus particles a day Replication of RNA viruses is prone to errors: - replication of RNA viruses average one mistake/ 10^4-10^5 nucleotides (HIV genome is about 10^4 nucleotides) -influenza average 1 mistake/ 10^3-10^4 nucleotides -influenza genome = 13500nt therefore 1.35 to 13.5 mutations/genome

Answer 40

An abrupt, major change in the influenza A viruses resulting in new Haemagglutinin and or new Haemagglutinin and neuraminidase proteins Results in a new influenza A subtype People do not have immunity to the new (eg novel) virus

Answer 41

Antigenic shift: - RNA segments are exchanged between viral strains in a secondary host -no cross protective immunity to virus expressing a novel Haemagglutinin

Answer 42

Enveloped dsDNA virus Family hepadnaviridae 8 viral genotypes Dane particle; 42nm diameter, 3.2kb DNA

Answer 43

HBV is extremely infectious (50-100 x more infectious than HIV) It remains infectious outside the body for up to 7 days Transmission: -perinatal transmission (mother to child at birth) -parenteral transmission (blood, blood products) -needle stick injury, tattooing, piercing -sexual -infected body fluids (saliva, menstrual, vaginal, seminal fluids) -medical/surgical/dental instruments

Answer 44

Health care workers Men who have sex with men/multiple sex partners/sex workers Blood transfusion recipients I.V drug users Infants of HBV carrier mothers Recipients of solid organ transplants

Answer 45

Incubation period: 30-180 days, mean 75 days Acute infection: usually mild, particularly in children. 30-50% adults present with jaundice and hepatitis severity: asymptomatic subclinical to fulminant fatal Chronic infection: -infants: 80-90% infected during first year of life, 30-50% children infected before age 6 -adults: <5% of otherwise healthy adults, 20-30% who are chronically infected will develop cirrhosis and/or liver cancer

Answer 46

Acute: -HBV DNA and HBeAg early markers of HBV infection, effective host response: -loss of HBeAg -appearance of HBe antibodies -clearance of HBV DNA and HBsAg Chronic: -continued viral replication -viral DNA, HBsAg and HBeAg in serum -elevated serum alanine and aspartate aminotransferase (ALT/AST) levels

Answer 47

Enveloped ssRNA virus Genus hepacivirus, family flaviviridae 55-65nm diameter Electron micrograph: Virus particles plus lipid

Answer 48

Bloodborne Transmission: -injecting drug use/ sharing injection equipment -reuse or inadequate sterilisation of medical/surgical/dental equipment (esp syringes/needles) -transfusion of unscreened blood and blood products -sexual practices that lead to exposure to blood -perinatal transmission (mother to child at birth) less common

Answer 49

Incubation period: 2 weeks to 6 months Acute infection: 80% asymptomatic, 20% fever, fatigue, decreased appetite, nausea, vomiting, abdo pain, dark urine, joint pain, jaundice Severity: asymptomatic subclinical to fulminant fatal Chronic infection: infants 50-60%, adults 50-90%, 20-30% who are chronically infected will develop cirrhosis and/or liver cancer

Answer 50

Approx 2.3 million people 6.2% of the estimated 3.7million living with HIV have serological evidence of past or present HCV infection Chronic liver disease major cause of morbidity and mortality in persons living with HIV

Answer 51

1. Antibody testing- historical infection 2. Viral nucleic acid testing- current infection 3. Check for cirrhosis

Answer 52

Aged 18 and above: pan-genomic DAA regimens for persons with chronic HCV Aged 12-17 years: sofosbuvir/ledipasvir 12 weeks genotypes 1,4,5,6,. sofosbuvir/ribavirin, 12 weeks, genotype 2 sofosbuvir/ribavirin, 24 weeks, genotype 3 Aged <12 years: defer treatment until 12 years

Answer 53

1.Herpes simplex virus 1 (HSV-1) 2. Herpes simplex virus 2 (HSV-2) 3. Human cytomegalovirus (HCMV) 4. Varicella-zoster virus (VZV) 5. Epstein Barr virus (EBV) 6. Human herpesvirus 6A/6B (HHV-6A/6B) 7. Human herpesvirus 7 (HHV-7) 8. Kaposi’s sarcoma-associated herpesvirus (KSHV/HHV-8)

Answer 54

Family: herpesviridae Subfamilies: alpha, beta, gamma, herpesvirinae Size: 180-200nm Enveloped Genome: linear ds DNA range 120kb to 230kb Glycoproteins: host cell specificity, virus attachment/fusion Tegument: evasion of innate immunity

Answer 55

3.7 billion people under 50 (67%)have HSV-1 infection globally 491 million people 15-49 13% have HSV-2 infection globally Herpes infections are most contagious when symptoms are present Transmission via oral to oral contact HSV-1; genital to genital contact HSV-2; oral to genital HSV-1/2 via sores, saliva, surfaces in or around the mouth/genitals Most oral and genital herpes infections are asymptomatic Transmissions during asymptomatic outbreaks The frequencies of reoccurrence varies from person to person

Answer 56

HSV-1 primary infection (stomatitis) Lytic cycle: Infection of mucoepithelial cells Replication in mucoepithelial cells Infectious virus released Latency: Immunologically silent infection Reactivation Replication in mucoepithelial cells Infectious virus released HSV-1 invades sensory nerve endings Establishes latency in Trigeminal ganglion

Answer 57

HSV1/2 invade sensory neurones and establish latency in ganglia Latency: -HSV-1: Trigeminal ganglion -HSV-2: sacral ganglia Neurovirulence: -invade and replicate in the CNS -profound disease - severe neurologic devastation - meningitis/encephalitis

Answer 58

Lytic cycle: virus DNS replication, new progeny viruses made, full range of virus proteins expressed, highly immunogenic Latency: no virus protein expression (modified protein expression), episomal DNA replicated with host cell DNA, immunologically silent

Answer 59

Transplant: -severity directly related to type of immunosuppressive therapy -pneumonitis, oesophagitis, gastritis HIV/AIDS: -more exaggerated -more frequent -more resistant to antivirals

Answer 60

Primary infection: chickenpox Reactivation: shingles Complications: -infants, adolescents, adults, pregnant women, people with HIV/AIDS or cancer, patients who have had transplants, people on chemotherapy, immunosuppression, long term steroids Serious complications include: -bacterial infections of the skin and soft tissues including group A streptococcal infections (necrotising fasciitis) -pneumonia -encephalitis, cerebellar ataxia -haemorrhagic complications -sepsis

Answer 61

Transmission: body fluids, blood products, organ donation,bone marrow Primary infection: usually asymptomatic, up to 8% symptomatic, fever, mononucleosis, hepatitis Congenital CMV: in utero infection of multiple systems; pneumonia, hepatitis, encephalitis Immunocompromised: -transplant (solid and hematopoietic stem cell): pneumonitis, oesophagitis, gastritis, enterocolitis, hepatitis, retinitis, GRAFT-VERSUS-HOST disease -HIV/AIDS: retinitis, oesophagitis, gastritis, enterocolitis, pneumonitis, hepatitis Primary maternal CMV infection- 40% transmission to foetus

Answer 62

Transmission: saliva Primary infection: usually asymptomatic, 4-7 week incubation period, replication in oropharyngeal epithelial cells and B cells, usually during childhood, up to 95% world population infected by adulthood Symptomatic primary infection: delayed infection can result in infectious mononucleosis (glandular fever), fever, pharyngitis, swollen lymph nodes, hepatitis

Answer 63

Site of EBV latency= b cells Expression of: viral proteins, non coding RNAs, miRNAs, viral oncogenes B cell malignancies: Burkitt lymphoma, Hodgkin lymphoma Epithelial cell malignancies: nasopharyngeal carcinoma, gastric carcinoma 10% T and NK cell malignancies: extranodal NK/T cell lymphoma, NK leukaemia

Answer 64

EBV- associated post transplant malignancies: -post transplant lymphoproliferative disease -hodgkin lymphoma EBV associated post transplant diseases: -encephalitic/ myelitis -pneumonia -hepatitis EBV and HIV related lymphoma: -Burkitt lymphoma -diffuse large B cell lymphoma - primary CNS lymphoma -hodgkin lymphoma, plasmablastic lymphoma, primary effusion lymphoma

Answer 65

Genome assembly and several genes are homologues of EBV Latency in B cell and endothelial cells Kaposi sarcoma in immunosuppression AIDS- endothelial cellen lytic and latent gene expression i kaposi’s sarcoma Primary effusion lymphoma PEL - B cell Multicentric castleman’s disease MCD- B cell

Week 2 Flashcards

(89 cards)