classification of pathogenic bacteria, pathogens and host Flashcards

Question

what are coliforms

Answer 1

organisma which are in the family Enterobacteriaceae • Mainly commensals of the human large intestine (gut commensals) • Key example is E. coli Lactose fermentation is a useful preliminary test in classifying gram -ve bacilli (can use selective agar)

Answer 2

-gram -ve bacilli Human and animal reservoirs 160 serotypes, strains vary in terms of disease potential - Sexual virulence mechanisms: pili, capsule endotoxin and exotoxins - Major form of food borne infection - Ferments lactose - Important cause of UTI and septicaemia, also neonatal sepsis - enterotoxogenic and enterohaemorrhagic Don’t treat with antiobiotics - these could lead to more toxins being produced

Answer 3

-gram -ve bacilli - Major form of food borne infection - DOES NOT ferment lactose - Salmonella enterica: Self-limiting enterocolitis with or without bloody diarrhoea - 2nd commonest cause of bacterial diarrhoae in the UK - Can be invasive i.e. enters bloodstream

Answer 4

- gram -ve bacilli Distinct from Salmonella enterica - Cause of typhoid fever - Fever, constipation early stages fatal if untreated - Organism can be isolated from blood cultures as well as faeces Risk during foreign travel but vaccine available

Answer 5

Campylobacter spp Helicobacter pylori vibrio spp

Answer 6

curved gram -ve bacilli microaerophilic (likes low oxygen), source is domestic animals and chickens, spread via faecal-oral route, foul smelling --> bloody diarrhoea (incubation period 2-5 days), commonest cause of bacterial diarrhoea in UK , no vaccine currently, often seen in springtime, can enter the bloodstream, not treated with antibiotics unless very severe

Answer 7

curved gram -ve bacilli natural habitat is human stomach, damages mucosa and causes ulcers, strong risk factor for gastric adenocarcinoma (oncogenic organism), treat to avoid future cancer risk

Answer 8

gram -ve cocco-bacilli (mixed appearance), causes respiratory tract infection (2y to S, pneumoniae), capsulate for (type b) was formerly an important cause of meningitis in children, other no-typable forms of H. influenzae still able to cause meningitis

Answer 9

``` anaerobic gram -ve bacilli- Water and soil coloniser - drains, sinks, mops - May contaminate medical equipment - Can colonise upper resp tract - Hospital acquired cause of sepsis e.g. UTI, bacteraemia, pneumonia (rare) - Feared respiratory pathogen in CF - Multi drug resistance mechanisms Limited treatment options ```

Answer 10

- Often part of polymicrobial infection e.g. liver/brain abscess - Increasing importance and recognition - Bacteroides spp, Prevotella, Porphyromonas - Difficult to grow in the lab due to their sensitivity to oxygen Bacteroides fragilis • Part of normal colonic flora • Causes intra-abdominal abscess • May spread to other sites e.g. blood

Answer 11

- Prevotella - Porphyromonas e.g. P. gingivalis - Pasteurella spp - Capnocytophyga spp - Important in aetiology of periodontal disease and may be part of polymicrobial dental abscesses - Role in aspiration pneumonia - Human and animal bit infections

Answer 12

- Not all bacteria can be stained w/ Gram's method - Not all bacteria can be cultured by standard methods Mycobacterium spp, spirochaetes, chlamydia/chlamydophila

Answer 13

• Resistant to decolourisation by acid or alcohol after staining with carbol fuchsin Mycobacterium species are visualised with special stains e.g. ZN or auramine

Answer 14

``` • ZN or auramine phenol screening • Doesn’t identify species • Culture required for ID ○ New automated liquid culture ○ Growth in 2-4 wks Molecules detection and identification of MTB possible ```

Answer 15

• Caused by mycobacterium tuberculosis • Linked with HIV • Recommended rapid diagnostic nucleic acid amplification tests for diagnosing pulmonary (including laryngeal) TB in adults if there is: Clinical suspicion of TB disease and the person has HIV In circumstances in which rapid info about mycobacterial species would alter the person's care In a situation where a large contact tracing initiative is being exploited

Answer 16

cant be cultured, mainly India, Nepal, Brazil, parts of Africa, attacks peripheral nerves

Answer 17

mycobacteria long, spiral shaped bacteria; not easily visualised by light microscopy, very difficult to culture (never Treponema pallidum), dark ground microscopy or immunofluorescence, often diagnosed by serology Common spirochaete diseases: Treponema pallidum (syphilis), Borrelia burgdoferi (lyme disease), Leptospira interrogans (Leptospirosis)

Answer 18

spirochaete treponema pallidum 1y - non-painful skin lesion 2y - generalised systemic illness and rash, latent phase - symptomatic episodes may occur 3y -CNS, congenital syphilis: stillbirth, neonatal death or disease diagnosis - serology, nucleic acid amplification tests (NAAT), part of antenatal screening, management - antibiotics, contact tracing and screening

Answer 19

mycobacteria transmitted by ticks, stage 1: skin rash (erythema chronicum migrans) appears at the site of the tick bite, stage 2: systemic illness occurs in some patients, wks/mths later when patients suffer cardiac or neurological and muscoloskeletal symptoms, stage 3: chronic disease, occuring yrs later when patients present with chronic skin, nervous system or joint abnormalities. Diagnosed by clinical assessment and serology (antibody detection)

Answer 20

mycobacteria infects animals and concentrates in the kidneys, spread is via urine and other body fluids and tissues (zoonosis), at risk groups (sewage workers, water sports), range of clinical presentations (Weil's disease: febrile illness with systemic upset, liver and renal failure, aseptic meningitis, 10% mortality)

Answer 21

obligate intracellular bacteria, cultured only in cell lines, can be diagnosed by serology, respiratory infection (chlamydophila pneumoniae, Chlamydophila psittaci (psittacosis) - contact with birds), ophtalmic and genital tract infection Chlamydia trachomatis: trachoma (tropical eye infections), genital and neonatal infection, diagosis: NAAT on 1st void urine or vulval/vaginal swabs, often asymptomatic in women, can lead to pelvic inflammatory disease and infertility

Answer 22

organism which is part of the normal flora e.g. E. coli in the gut, S. aureus in the nose

Answer 23

organism which can cause disease

Answer 24

infectivity and virulence

Answer 25

ability to become established on or within a host ○ Attachment: E. coli (P-fimbriae, receptor on uroepithelial cells) Acid resistance: Helicobacter pylori - lives in the stomach and causes gastritis and gastric ulcers (urease, makes ammonia from urea)

Answer 26

capacity to cause harmful effects (disease) once established ○ Conferred by virulence factors: genetically determined microbial components § Invasiveness, toxin production, evasion of immune system □ INVASIVENESS: Streptococcus pyogenes (Group A streptococci), necrotising fasciitis, cellulitis, connective tissue breakdown (hyaluronidase, collagenase), fibrinolysis (streptokinase) Specific to strains, not species

Answer 27

released extracellularly by the microorganism

Answer 28

exotoxins which act on the GI tract

Answer 29

e.g. SUPERANTIGENS: Certain exotoxins of S. pyogenes and S. aureus. Able to stimulate division of T cells in the absence of specific antigen. Overwhelming cytokine production causes toxic shock

Answer 30

CHOLERA: Vibrio cholera, colonises S intestine, enterotoxin production (increases cAMP levels, inhibits uptake of Na+ and Cl- ions, stimulates secretion of Cl- and HCO3- ions. Passive (massive) outflow of water, causes death by dehydration, treated by rehydration

Answer 31

structurally part of the gram -ve cell wall

Answer 32

Lipopolysaccharide (Lipid A, oligosaccharide core, specific polysaccharide chain), E. coli and other gram -ve bacilli, Neisseria meningitidis, induces severe uncontrolled host response (cytokine production, fever, rigors, hypotension, tachycardia, collapse

Answer 33

- Certain exotoxins of S. pyogenes and S. aureus - Able to stimulate division of T cells in the absence of specific antigen - Overwhelming cytokine production causes toxic shock

Answer 34

- Virus infects cells of the respiratory tract - Destruction of respiratory epithelium which can lead to secondary bacterial infections - Altered cytokine expression leading to fever • Non-human host for influenza a play a key role in generating new virus types through antigenic shift

Answer 35

minor changes, in the genes of flu viruses, occurs gradually over time to generate antigenic variants leads to a generation of novel influenza viruses

Answer 36

(abrupt major changes in antigenic structure) | leads to generation of novel influenza viruses

Answer 37

- Poliomyelitis (poliovirus) - Aseptic meningitis (many enteroviruses) - Myocarditis (coxsackie B viruses) - Pancreatitis (coxsackie B viruses) Respiratory infections (many enteroviruses)

Answer 38

herpes simplex virus - cold sores (type 1) and genital lesions (type 2)

Answer 39

- E.g. papillomaviruses - cervical carcinoma, Retroviruses - lymphomas and leukaemias Human T - lymphotropic virus 1 (HTLV-1): transmission by blood and mother to child, infects T cells, modifies host cell gene expression using a transactivating protein, variety of diseases including leukaemia (adult T cell lymphoma-leukaemia), directly responsible for the tumour

Answer 40

``` natural/artificial antigen stimulates immune response long term immunity immunological memory no immediate effect but faster and better response to next antigenic encounter ```

Answer 41

attenuation of a pathogenic organism by repeated passage in cell culture or non-human host usually promote a full, long-lasting antibody response after one or two doses reversion to wild-type organism may occur contraindicated in some individuals require refrigeration until administration

Answer 42

inactivated pathogenic organism reversion to wild type organism doesnt occur promote weaker immune responses in comparison to live vaccines - multiple doses may be required some inactivated vaccines contain adjuvants possible side effects of producing inflammatory responses

Answer 43

substances that enhance the antibody response

Answer 44

MMR, BCG, polio, varicella zosterm, yellow fever

Answer 45

polio, hep A, rabies

Answer 46

toxin treated with formalin toxin retains antigenicity but has no toxic activity only induces immunity against the toxin and not the organism that produced it

Answer 47

tetanus, diphtheria

Answer 48

type of infection that may occur after an acute episode; the organism is present but symptoms are not; after time the disease can reappear

Answer 49

patient is a carrier for a disease or infection but experiences no symptoms

Answer 50

innate and acquired immunity phagocytosis antibodies and complement cell mediated immunity

Answer 51

physical defences | phagocytic cells

Answer 52

specific response to antigen leads to immunological memory humoral and cellular

Answer 53

polymorphs (neutrophils, eosinophils, basophils) and monocytes in blood mononuclear phagocytic system: spleen, liver and regional lymph nodes other white cells

Answer 54

involves immunoglobulins neutralised toxin, neutralised virus, prevents adherence of microorganisms, opsonises capsulate organisms, useful in diagnosis humoral immunity: mostly bacterial infection, extra-cellular, acute inflammation, neutrophilia

Answer 55

combat intracellular infection | macrophages present antigen and stimulate T cells, cytokines produced and control the response

Answer 56

commonest cause of traveller's diarrhoea (contaminated water)

Answer 57

more severe form, bloody diarrhoea, haemolytic uraemic syndrome (HUS) associated w/ E. coli O157

Answer 58

``` not lactose fermenting low infective dose faecal-oral spread bacillary dysentery some strains produce toxin 4 species ```