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phase2a medicine > microbiology (bacteria) > Flashcards

microbiology (bacteria) Flashcards

Information regarding bacteria that may come up as part of microbiology. (74 cards)

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1
Q

bacterial shapes

A

cocci
bacilli
vibrio
spirochaete

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2
Q

ziehl-neelsen staining

A

used for Mycobacteria

acid-fast will stain pink/red

non acid-fast will stain blue

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3
Q

catalase test

A

staphylococci is catalase positive (will generate gas bubbles); streptococci is catalase negative (no reaction)

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4
Q

coagulase test

A

Staphylococcus aureus is coagulase positive (will clot when added to plasma); other Staphylococcus spp. are coagulase negative

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5
Q

oxidase test

A

bacteria that produce cytochrome oxidase are oxidase positive - e.g. Pseudomonas and Neisseria

positive result will turn black/purple in colour

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6
Q

optochin test

A

differentiates Strep. pneumonia from other alpha haemolytic Streptococci

Streptococci pneumonia + optochin will cause lysis

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7
Q

metronidazole

A

identifies sensitive anaerobes by inhibiting their growth on culture medium

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8
Q

MacConkey agar

A

isolates and identifies enteric bacteria

contains bile salts, lactose, and pH indicator

lactose fermenting bacteria will cause red/pink colony - Escherichia coli and Klebsiella

non-lactose fermenting bacteria will leave a clear colony - Salmonella, Shigella, and Pseudomonas

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9
Q

blood agar - haemolysis

A

alpha haemolysis - green - partial RBC and Hb breakdown - viridans

beta haemolytic - clear zones - complete erythrocyte lysis

non-haemolytic - no change

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10
Q

Lancefield grouping

A

differentiates between beta haemolytic Strep by detecting surface antigens

group A: Streptococcus pyogenes

group B: Stretococcus agalactiae

group D: Enterococcus

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11
Q

exotoxin

A

produced mostly by gram +ve bacteria

actively secreted toxins with a specific action (e.g. botulinum toxin)

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12
Q

endotoxin

A

a component of the cell wall that is released when bacteria are damaged

gram +ve: lipoteichoic acid
gram -ve: lipopolysaccharides

less specific actions include septic shock

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13
Q

gram positive bacterial groups

A 
Streptococcus 
Staphylococcus
Corynebacterium 
Listeria
Bacillus
Clostridium
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14
Q

Streptococcus

A 
chains or diplococci
gram +ve
catalase negative
alpha haemolytic: oralis, sanguis, mutans, mitis
beta haemolytic: progenies, agalactiae 
non-haemolytic: Enterococcus faecalis
Aerobic
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15
Q

Streptococcus pneumoniae

A

alpha haemolytic, diplococci, commensal of upper respiratory tract in 10-30%, droplet transmission
CAP, COPD exacerbation, sinusitis, otitis media
bacterial meningitis
treat with penicillin or erythromycin

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16
Q

Streptococcus Viridans (alpha haemolytic)

A

upper respiratory tract and GI tract commensal
bacterial endocarditis
dental caries
treat with penicillin/amoxicillin (erythromycin if allergic)
bacterial endocarditis treat with penicillin and gentomycin

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17
Q

Streptococcus pyogenes (group A ß-haemolytic)

A

upper respiratory tract commensal in 5%
transmission: airborne, respiratory secretions, hands
skin: cellulitis, necrotising fasciitis, impetigo, erysipelas, wound infections, scarlet fever
URTIs: pharyngitis (strep throat), tonsillitis, acute otitis media
invasive: sepsis
post-infective: rheumatic fever and glomerulonephritis
treat with penicillin/amoxicillin (erythromycin if allergic)

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18
Q

Streptococcus agalactiae (group B ß-haemolytic)

A

faecal commensal in 30-40% of population and vaginal in 10-30%
causes neonatal septicaemia and meningitis in children
causes UTIs, post-partum sepsis, bacterial endocarditis, and septicaemia in adults

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19
Q

Enterococcus (group D non-haemolytic, MacConkey growth)

A 
GI tract commensal 
infective endocarditis
UTI
wound infections
IV catheter infection
treat with penicillin/vancomycin
treat IE with penicillin/vancomycin + gentamicin
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20
Q

Staphylococcus

A

cocci in clumps
gram positive
catalase positive
S.aureus is coagulase positive; the others are coagulase negative
S.aureus has golden yellow colonies; S.epidermidis and S.saprophyticus have white colonies
aerobic

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21
Q

Staphylococcus aureus

A

coagulase positive
anterior nares in 20-30% of population
impetigo, paronychia, abscesses, cellulitis, wound/IV line infection
osteomyelitis and septic arthritis
septicaemia, conjunctivitis, IE, pneumonia
toxin mediated: toxic shock syndrome, scalded skin syndrome, and food poisoning
flucloxacillin
vancomycin for MRSA

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22
Q

Staphylococcus epidermidis

A

coagulase negative
skin and mucous membranes
foreign body infection or native valve endocarditis
treat with flucloxacillin (or vancomycin if resistant)

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23
Q

Staphylococcus saprophyticus

A

coagulase negative
UTIs in sexual active young women
treat with trimethoprim or flucloxacillin

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24
Q

Corynebacterium

A

bacilli
gram positive
aerobic
e.g. C.diptheriae

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25
Corynebacterium diphtheriae
nasopharyngeal carriers droplet spread diphtheria toxin --> epithelial cell destruction and myocardial/neural cell damage --> bull neck lymphadenopathy and pseudomembrane covering tonsils treat with erythromycin, diphtheria antitoxin and vaccination less than 5 cases per year in UK (due to vaccination)
26
Listeria
bacilli gram positive aerobic e.g. Listeria monocytogenes
27
Listeria monocytogenes
domestic animal faeces and food transmission: contact with animals, ingestions, transplacentally, perinatally miscarriage and stillbirth can cause meningitis, pneumonia, encephalitis, and sepsis in neonates, the elderly, or the immunocompromised treat with ampicillin/erythromycin and gentamicin
28
Bacillus
``` bacilli gram positive spore forming aeorbic e.g. Bacillus anthracis, B. cereus ```
29
Bacillus anthracis
infected herbivore carcasses transmission from handling infected materials (not from eating) cutaneous lesions anthrax may also be pulmonary or gastrointestinal treat with ciprofloxacin or doxycycline
30
Bacillus cereus
foods (e.g. rice) ingestion of infected foods self-limiting
31
Clostridium
``` bacilli gram positive anaerobic Clostridium tetani has terminal spores C. perfringens is brick-shaped ```
32
Clostridium perfringens
human gut commensal, skin, soil gas gangrene, intra-abdominal sepsis, anaerobic cellulitis, food poisoning, septicaemia, post-abortion infection treat with penicillin and clindamycin, and antitoxin
33
Clostridium tetani
human and animal gut commensal, soil spores entering open wounds causes tetanus treat with human tetanus immunoglobulin and benzodiazepines
34
Clostridium difficile
faecal commensal in neonates and young children spores via faecal oral route causes pseudomembranous colitis (diarrhoea following abc therapy) treat with vancomycin
35
Clostridium botulinum
human and animal GI tracts, soil and plants transmission from food ingestion and wound contamination causes botulism - descending paralysis secondary to botulinum toxin treat with vancomycin or metronidazole
36
gram negative bacterial groups
``` Neisseria Coliforms (also Enterobacteriaceae) Parvobacteria Helicobacter Vibrio Pseudomonas ```
37
Neisseria
gram negative diplococci oxidase positive aerobic e.g. Neisseria meningitidis
38
Neisseria meningitidis
nasopharynx in 5-20% or general population transmission: droplets or direction mucosal contact meningitis septicaemia with purpuric skin rash treat with benzylpenicillin or cefotaxime treat close contacts with rifampicin, ciprofloxacin, or ceftriaxone vaccine available for some strains
39
Neisseria gonorrhoeae
transmission by direct mucosal contact gonorrhoea, ophthalmia neonatorum, Reiter's syndrome (urethritis, conjunctivitis, arthritis) treat with ciprofloxacin or cefixime
40
Coliforms (enterobacteriaceae)
gram negative bacilli E.coli and Klebsiella pneumonia pink colonies on MacConkey agar Salmonella type, paratyphoid, and enteritis clear colony on MacConkey aerobic
41
Escherichia coli
colonic commensal faecal-oral route diarrhoea, UTIs, pneumonia (HAP or neonatal), neonatal meningitis, haemolytic uraemia syndrome (anaemia, thrombocytopenia, oliguria, and renal failure) treatment depends on site of infection - give trimethoprim for UTI and cephalosporins for pneumonia
42
Klebsiella pneumoniae
HAP, UTI, neonatal meningitis (rare) | treat with cephalosporins
43
Proteus mirabilis
faecal commensal UTIs in young females wound and IV catheter infection treat with trimethoprim
44
Salmonella typhi and paratyphi (A, B, and C)
faecal-oral route typhoid and paratyphoid (enteric fever) treat with ciprofloxacin
45
Salmonella enteritidis
commensal of animal GI tracts - infection from inadequately cooked food contaminated with animal faeces gastroenteritis ± bacteraemia self-limiting
46
Shigella dysenteriae
faecal-oral bacillary dysentery ciprofloxacin
47
Parvobacteria
gram negative bacilli aerobic e.g. Haemophilus influensa, Bordatella pertussis, Campylobacter, Legionella pneumophila
48
Haemophilus influenzae
type B (Hib) is most pathogenic but is now rare due to vaccine upper respiratory tract commensal acute epiglottis, meningitis, osteomyelitis, cellulitis, otitis media, septic arthritis, pneumonia treat with cefotaxime or ceftriaxone
49
Bordatella pertussis
non-commensal inhalation of airborne droplet whooping cough treat with erythromycin
50
Legionella pneumophila
warm water inhalation or aerosolised droplet Legionnaire's disease: severe pneumonia and high fever Pontiac fever: flu-like illness treat with erythromycin, in severe cases give rifampicin or ciprofloxacin
51
Campylobacter jejune and coli
``` contaminated poultry or pork or unpasteurised milk gastroenteritis ±dysentery reactive arthritis Guillain-Barré syndrome self-limiting if severe, treat with ciprofloxacin ```
52
Helicobacter
curved/spiral bacilli gram negative aerobic e.g. H.pylori
53
Helicobacter pylori
``` faecal oral route chronic gastritis duodenal and gastric ulcers increased gastric cancer risk treat with clarithromycin and amoxicillin or metronidazole - also with PPI (omeprazole) ```
54
Vibrio
vibrio shaped, gram negative aerobic e.g. Vibrio cholerae
55
Vibrio cholerae
water, seafood, faecal-oral cholera: rice water diarrhoea (up to 25 litres of fluid lost per day) treat with rehydration and ciprofloxacin for severe cases
56
Pseudomonas
gram negative bacilli oxidase positive aerobic e.g. P. aeruginosa
57
Pseudomonas aeruginosa
``` moist environments, fruit and veg, faeces hand borne and direct contact pneumonia (esp. in CF pts) wound, burn, and IV catheter infections external otitis folliculitis UTIs (esp. with catheters) treat with gentamicin or IV ceftazidime treat with ciprofloxacin for children with CF and adults with bronchiectasis ```
58
Chlamydia
no distinct bacterial shape gram negative intracellular e.g. Chlamydia trachomatis, C.psittaci
59
Chlamydia trachomatis
``` mucosal contact chlamydia Trachoma: chronic follicular keratoconjunctivitis Reiter's syndrome pelvic inflammatory disease treat with doxycycline or azithromycin ```
60
Chlamydia psittaci
pigeon fancier's lung, atypical pneumonia | treat with tetracycline
61
Coxiella
no staining - diagnosis by serology intracellular e.g. Coxiella burnetti
62
Coxiella burnetti
cattle and sheep, inhaled in dust, unpasteurised milk, infected carcasses, droplet spread Q-fever: flu-like illness, hepatitis ±splenomegaly treat with tetracycline or doxycycline
63
Rickettsia
no staining intracellular e.g. R.prowazeki, rickettsii, conorii, typhi, akari transmission via arthropods (e.g. ticks) causes typhus treat with doxycycline, chloramphenicol, or tetracycline
64
mycobacteria
acid fast bacilli ziehl-neelson staining pink/red Lowenstein-Jensen culture medium (up to 12 weeks) e.g. M. tuberculosis, M. leprae
65
Mycobacterium tuberculosis/africanum/bovis
aerosol droplets tuberculosis treatment: rifampicin and isoniazid for 6 months, ethambutol and pyrizinamide for first 2 months
66
Mycobacterium leprae
aerosol droplet spread leprosy treat with rifampicin and dapsone
67
Treponema
spirochaete no staining e.g. T. pallidum
68
Treponema pallidum
sites of broken mucosa during sexual contact, congenital, blood transfusion syphilis treat with penicillin or doxycycline
69
Borrelia
spirochaete no staining e.g. B. burdorferi
70
Borrelia burdorferi
tick bites Lyme disease treat with doxycycline
71
Leptospira
spirochaete no staining e.g. L. interrogans
72
Leptospira interrogans
water and animals open wounds, mucous membranes, conjunctivae Leptospirosis ranges from fever to Weil's disease treat with doxycycline, benzylpenicillin, or amoxicillin
73
Mycoplasma
no staining very small organism without a cell wall aerobic or facultative anaerobe e.g. M. pneumoniae
74
Mycoplasma pneumoniae
``` droplet tranmission atypical pneumonia (commonly in young adults) treat with erythromycin or doxycycline ```

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