Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MRCOG Part 1 > Microbiology > Flashcards

Microbiology Flashcards

1
Q

RNA viruses

A

Hep A, C, D, E
Rubella
Zika
(all single stranded)

Rotavirus is double stranded

HIV is a retrovirus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

DNA viruses

A

VZV
HSV
Hep B
CMV
HPV
EBV
(all double stranded)

Parvovirus is single stranded

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Bacteria

A

Prokaryotic (no membrane-bound organelles)
Visible by light microsopy, average diameter 1μm
Cell wall made of N-acetyl glucosamine/muramic acid, peptidoglycans (penicillin binding sites, target for β-lactams), polypeptides and polysaccharides

BACTERIAL GROUPS
Gram stainable - +ve or -ve or variable
Acid-fast bacilli - cell wall has high lipid content so difficult to stain (mycobacteria, norcardia)
Unusual - no peptidoglycans (chlamydia, mycoplasma)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Taxonomy of bacteria

A

By shape - bacilli (rods) or cocci (grains)

By O2 requirement - aerobes or anaerobes (anaerobes can be facultative so capable of aerobic respiration if O2 is present, OR obligate anaerobes which die in presence of O2

By spore forming

By staining

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Gram staining

A

Stain with crystal violet, then Gram’s iodine, decolourize with acetone, then counter-stain with methyl red

Gram +ve stain blue, retaining crystal violet stain
- due to peptidoglycan, a thick polysaccharide coat that loses stain very slowly once taken up

Gram -ve stain pink, as cell wall is thinner so doesn’t retain crystal violet but does take up methyl red stain
- cell wall consists of outer layer of LPS, then periplasmic layer containing β-lactamase, then inner peptidoglycan layer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Gram +ve bacteria examples

A

Cocci
- staphylococcus (form grape-like clusters)
- streptococcus (form chains)

Bacilli
- clostridium
- listeria
- bacillus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Gram -ve bacteria examples

A

Cocci
- neisseria gonorhoeae
- neisseria meningitidis
- moraxella catarrhalis

Bacilli
- haemophilus influenzae
- klebsiella pneumoniae
- legionella
- escherichia coli

Spirochaetes
- leptospira
- borellia (lyme)
- treponema (syphilis)

Vibrio
- cholera

Can also be divided based on lactose fermentation (klebsiella, Ecoli, enterobacter) which stain orange on McConkey agar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Bacterial toxins

A

Exotoxins
- secreted by organisms
- highly antigenic, destroyed by heat
- gram +ve (or -ve) produce
- form toxoids

Endotoxins
- released on cell death and lysis
- grame -ve only eg E coli
- mainly lipid A from LPS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Bacterial antimicrobial resistance

A

Bacterial mechanisms
- drug inactivation (eg production of β-lactamase
- alteration of drug target site (eg alteration on penicillin-binding sites)
- bacterium metabolic pathway alteration
- fibronectin coat
- IgA cleaving protease

Mechanisms of transfer of resistance - horizontal (plasma DNA transfer, chromosomal mediated resistance, bacterial conjugation) or vertical

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Vaginal flora

A

Influenced by oestrogen levels
-> increased vaginal glycogen concentration
- pH 3.5-4.5 due to conversion of glycogen to lactic acid by lactobacilli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Clinical isolation of bacteria

A

Use of specific microbiological swabs
Storage at 4degrees
Preliminary lab report takes 18hours
Identification via detection of antigens, antibodies, nucleic acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Streptococcus

A

Gram +ve
Mostly facultative anaerobes (can survive in either)
Catalase negative or oxidase negative
Form chains
Produce exotoxins

3 groups based on levels of haemolysis when cultured on horse blood agar:
- non-haemolytic - E.faecalis
- partial haemolytic - S.viridans, enterococcus, pneumococcus
- complete haemolytic (β)- group A/C/G, group B, group F

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

β-haemolytic streptococci

A

Gram +ve
Subdivided by Lancefield grouping A-O

Group A, C, G - associated with toxic shock syndrome, necrotizing fasciitis, vaginitis
Group B - chorioamnionitis, neonatal sepsis, endometritis
Group F - can cause abscesses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Group A streptococcus

A

= strep pyogenes
(type of β-haemolytic gram +ve)

Virulence factor determined by presence of M protein (fimbrial protein involved in capsule formation, anti-phagocytic, responsible for organism adhesion and invasion), hyaluronidase, streptokinase, DNAse, superantigens

Causes - scarlet fever, toxic shock, rheumatic fever, glomerulonephritis, necrotizing fasciitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Group B streptococcus

A

= streptococcus agalactia
(type of β-haemolytic gram +ve)

20-35% women carry, intermittent
Maternal to fetal transmission 80%, with invasive neonatal disease 0.5/1000 births
6% neonatal mortality rate from early-onset GBS disease in UK

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Indications for antibiotic prophylaxis during labour

A
  • early-onset GBS disease in previous baby
  • GBS in vagina/urine during pregnancy
  • prolonged ROM at term (>18hr)
  • preterm labour <37weeks
  • preterm ROM with known GBS
  • intrapartum pyrexia

-> Benpen 3g IV loading dose then 1.5g IV 4hrly until delivery
(or clinda 900mg IV 8hrly, or erythromycin 500mg 6hrly, vancomycin last resort)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Streptococcus pneumoniae

A

Partial haemolytic gram +ve
Diplococcus - forms pairs
Draughtsman-shaped colonies
Optochin sensitive
Bile soluble

-> meningitis, pneumonia, primary bacterial peritonitis (pre-pubertal girls)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Enterococcus

A

Partial haemolytic gram +ve
E.faecalis or E.faecium
GI commensal organisms
Resistant to many antimicrobials

-> endocarditis, proctitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Listeria monocytogenes

A

Gram +ve bacilli
1/10,000 pregnant women
Some strains β-haemolytic
Produces flagella at room temperature, but not 37degrees

Listeriosis -> meningitis, hepatosplenomegaly, bradycardia

Transmitted in contaminated food
To the fetus via transplacental spread or ascending infection
In placenta -> miliary granuloma, focal necrosis
50% fetal mortality rate

Treatment - amoxicillin or gentamicin, 3 weeks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Staphylococcus

A

Gram +ve cocci
Facultative anaerobes
Form grape-like clusters
Classified on ability to form coagulase

-> scalded skin syndrome, toxic shock, slime in IV cannula

eg MRSA is coag +ve, DNAse +ve, catalase +ve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Actinomycetes israelii

A

Gram +ve anaerobe bacillus
Shows branching
Slow growing
In mouth, IUCDs

-> chronic granulomatous disease by produces sulphur granules in tissues

Treat with penicillin, 6-12mo therapy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Neisseria

A

Gram -ve diplococci
-> meningitis, gonorrhoea
Capnophilic (thrive in presence of high CO2)
Treat with cephalexin
Multidrug resistance is growing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Gonorrhoea

A

Neisseria gonorrhoeae (gram -ve intracellular diplococci)
Infects mucus membranes of urethra, endocervix, rectum, pharynx, conjunctiva (can also Bartholin’s)
Complications - gonococcal ophthalmia neonatorum (conjunctivitis), neonatal vaginitis/proctitis/urethritis, disseminated gonococcal infection

Treatment - IM ceftriaxone 250mg stat OR PO cefixime 400mg
Needs test of cure 3 days after treatment
40% also have concurrent chlamydia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Gardnerella vaginalis

A

Facultative anaerobe
Gram variable
Bacillus
Normal commensal organism of vagina
β-haemolytic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Bacterial vaginosis

A

Polymicrobial condition characterized by:
- depletion of protective lactobacillus species
- increase in other organisms esp anaerobes, eg G.vaginalis, mobincullus, atopobium vaginale

60% asymptomatic
More common in black women
Aetiology unknown
Assoc with mid-trimester miscarriage, pre-term birth, ROM, endometritis

Treat with metronidazole 400mg BD for 7days

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Amsel and Hay/Ison criteria

A

AMSEL
For diagnosis of BV, need 3/4:
- vaginal discharge
- clue cells
- pH>4.5
- fishy odour with alkali on wet mount

HAY/ISON based on gram stain
- Grade 1 = normal flora, mostly lactobacilli
- Grade 2 = mixed flora
- Grade 3 = BV, absent lactobacilli

Typically fishy white/grey vaginal discharge worse after intercourse

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Syphilis microbiology and treatment

A

Gram -ve spirochaete Treponema pallidum

Cannot be cultured in lab
Serology indistinguishable from yaw and pinta

Treatment - penicillin G, doxycycline
- watch for Jarisch-Herxheimer reaction (due to release of cytokines when antibiotics kills bacteria)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Syphilis stages

A

PRIMARY
- chancre (painLESS ulcer)
- appears 10-90days post exposure, persists 4-6weeks before disappearing

SECONDARY
- 1-6months after primary infection
- symmetrical non-itchy rash on trunk, condylomata latum (white/grey lesions), mucous patches around genitals or mouth

TERTIARY
- 1-10years after initial infection
- gummas (soft rubbery growth, granuloma with necrotic centre), neurosyphilis, de Musset’s sign (head nod in time with heart beat)

Can -> endarteritis obliterans

29
Q

Test for syphilis

A

Hard to distinguish between active, and treated past infection

Non-specific tests - Veneral disease research laboratory (VDRL), rapid plasma reagin, Wasserman’s reaction, Hinton’s test

Specific tests - fluorescent treponemal antibody-absorption test (FTA-ABS), and treponema pallidum agglutination assay (TPPA)

False +ve with non-specific tests in viral infections, lymphoma, TB, malaria, pregnancy

30
Q

Mycoplasma hominis

A

In 20% of sexually active women
Can either be a primary or co-pathogen in PID
Can cause postpartum pyrexia
Can be co-pathogen in chorioamnionitis

Treat - doxycycline / clindamycin

31
Q

Chlamydia trachomatis

A

Obligate intracellular grame -ve organism

3 subgroups:
- A-C (follicular conjunctivitis)
- D-K (genital)
- L1-L3 (lymphogranuloma venereum)

Contains DNA and RNA
72hr lifecycle, elementary body -> reticular body -> inclusion body

Treatment - doxycycline / azithromycin / erythromycin / ofloxacin

Test of cure only in pregnant or breastfeeding women

32
Q

Vaginal discharge in children causes

A

Foreign body (commonest)
Strep pyogenes
Haem influenza
Shigella sonei
Pinworms
Chlamydia
N gonorrhoeae

33
Q

Wound infection

A

Usually staph aureus - give fluclox
Typically require 10^5 organisms to establish
If foreign body present, only need 10^3

34
Q

Necrotizing fasciitis

A

Type 1
- assoc with surgery, diabetes
- due to polymicrobial infection, anaerobes facultative or obligate

Type 2
- due to group A strep

Treatment
- surgical debridement
- antibiotic combination of Benpen 1.2g IV QDS, clindamycin, ciprofloxacin
- surgical re-exploration of wound

35
Q

Pelvic inflammatory disease symptoms and complications

A

Pelvic / abdominal pain
Dyspareunia
Post-coital bleeding
Discharge
Cervical tenderness
Fever

Complications
- ectopic pregnancy
- tubal infertility (12% 1st episode, 20% 2nd, 50% 3rd)
- chronic pelvic pain
- Fitz-Hugh-Curtis syndrome (adhesions causing RUQ pain and perihepatitis)

36
Q

Causative organisms and treatment of PID

A

Organisms - chlamydia, neisseria (gonorrhoea), mycoplasma hominis/ureaplasma, gardnerella, trichomonas vaginalis, GBS

Treatment:
OP
- ofloxacin 400mg BD + metronidazole 400mg BD for 14 days OR
- IM ceftriazone 250mg then PO doxy 100mg BD + metro 400mg BD for 14 days

37
Q

Reiter’s syndrome

A

Reactive arthritis caused by bacterial infection
Can’t pee, see, climb a tree:
Urethritis, uveitis, arthritis

Causative organisms - salmonella, yersinia, shigella, campylobacter, chlamydia, gonorrhoea

38
Q

Fungi

A

Multicellular eukaryotic (membrane-bound organelles)
Aerobic
Cell walls have no peptidoglycans but contain ergosterol
Contain - fibrils, chitins, mannan, glucan
Asexual and sexual reproduction
Secrete keratinase

MOULDS - multicellular, branching filament (hyphae/mycelia), reproduce by spores, eg aspergillus
TRUE YEASTS - unicellular, reproduce by budding, eg cryptococcus
YEAST LIKE - eg candida
DIMORPHIC - grows as yeast at 37degrees, as mycelia at 20degrees, eg histoplasma

39
Q

Protozoa

A

Unicellular, eukaryotic, free-living organisms
Include trichomonas vaginalis, toxoplasma gondii, giardia, cryptosporidium, plasmodium
Asexual or sexual reproduction

True protozoa and helminths (fluke = trematode, tape = cessatode, ring = nematode)

40
Q

Trichomonas vaginalis

A

Flagellate protozoon
Venereal transmission (STI)
Diagnose - wet prep, PCR, culture

Symptoms - discharge, intense itching and irritation, strawberry cervix, preterm delivery

Treatment - metronidazole or tinidazole

41
Q

Toxoplasma gondii

A

Zoonotic infection - mainly cats
Diagnosis - IgA/M avidity, serial samples taken 3weeks apart
Affects muscle, neural tissue, placenta
Transmission via placenta in primary infection, greatest risk at 26-40weeks BUT the earlier the infection occurs the more severe the disease in the newborn
Maternal risk of chorioretinitis and encephalitis
Congenital infection - stillbirth, cerebral calcification, microcephaly/hydrocephalus, choroidoretinitis, cerebral palsy, epilepsy, hepatosplenomegaly, thrombocytopenia

Toxoplasma IgM persists for 3years after eradications

42
Q

Malaria

A

From female Anopheles mosquito vector
Infects RBCs
Plasmodium falciparum / vivax / ovale / malariae / knowlesi
Severe malaria if parasitaemia >2%

Clinical features - fever, resp distress/pulm oedema, arthralgia, retinal damage, splenomegaly, hepatomegaly, haemoglobinuria and renal failure, coma, convulsions, 20% mortality in non-pregnant but 50% in pregnant
Biochemical abnormalities -hypoglycaemia, anaemia, thrombocytopenia, acidosis, hyperlacatataemia
Fetal effects - miscarriage, stillbirth, prem, placental parasitaemia

43
Q

Diagnosis and management of malaria

A

Diagnosis via thin and thick blood films

Management:
- vector control - insecticides, mosquito nets, skin repellents
- chemo-prophylaxis - mefloquine, doxycycline, malarone, quinine
- treatment - quinine, chloroquinine, artermisinin

44
Q

Viruses

A

No organelles
Depend on host for energy metabolism and protein synthesis
Genetic material is either RNA or DNA
Viral coat = capsid
Fetal transmission rate increases with gestational age
Incubation period usually 21days ish

45
Q

CMV

A

Part of herpes family
50-80% women are seropositive
Feto-maternal transmission 40%, symptomatic in 10%
Maternal infection diagnosed with IgG avidity (high = old infection)

Congenital defects - sensorineural hearing loss, retinitis, cerebral palsy, hepatosplenomegaly, hyperbilirubinaemia, intracranial calcification, thrombocytopenia, FGR, microcephaly

CMV IgM persists for months/years

46
Q

Herpes simplex

A

Type 1 - 30% genital infections in UK
Type 2 - 70%

Fetal transmission >30% if primary infection in 3rdT
- 2% if secondary episode during labour
High fetal mortality, so relative indication for caesarean if maternal lesions present within 6 weeks of birth, as long as no ROM

21 day incubation
Affects skin, eyes, mouth, CNS

47
Q

Varicella Zoster

A

Part of herpes family
- contagious 48hr pre rash, incubates 10-21 days

Fetal transmission (congenital fetal varicella syndrome) only in first 20weeks
- overall rate 1%, higher at 13-20weeks
- CNS anomaly (microcephaly, cortical atrophy), limb hypoplasia, cicatricial scarring, eye defects (microphthalmia, cataracts, chorioretinitis)

Risk of neonatal varicella if maternal infection within 10days of delivery
Maternal complications - pneumonitis, encephalitis, hepatitis

Treatment
- maternal infection -> aciclovir
- exposed to VZV -> prevention of disease with VZIgG

48
Q

Rubella

A

RNA virus
aka German measles
Togavirus
Single-stranded RNA genome enclosed in capsid
Spreads via droplets

Congenital - eye (cataracts, glaucoma), heart (PDA, VSD, pulm stenosis), sensorineural hearing loss, haematological (thrombocytopenic purpura, haem anaemia, lymphadenopathy), ‘blueberry muffin’ rash

Feto-maternal transmission rate 90% in 1stT, 30% in 2ndT
In 1stT, 90% of those infected develop defects. >20 weeks no increased risk to fetus.

49
Q

Parvovirus B19

A

DNA virus
aka fifth disease / slapped cheek syndrome / erythema infectiosum
Incubation 4-14 days

60% women are immune
Causes miscarriage (10%), hydrops fetalis
NO congenital defects
Fetal transmission 30% in 1stT
Treat with intrauterine fetal blood transfusion

Virus attacks P blood group antigen (globiside) on RBCs and fetal heart

50
Q

HIV

A

Lentivirus (RNA retrovirus)
Primarily infects Th cells (CD4 esp), macrophages, dendritic cells, via gp120 glycoprotein
AIDS is when CD4 count <200. Complications include Kaposi’s sarcoma, pneumocystis carinii pneumonia, Non-Hodgkin’s lymphoma, dementia
Transmission is sexual, blood products, perinatal
+ possibly from saliva, tears or urine - negligible risk
0.17% of UK antenatal population are +ve
Fetal transmission rate is 15% without treatment, <1% with
- increased vertical transmission if high maternal viral load, low CD4 count, PROM, chorioamnionitis, co-morbid viral infection, breastfeeding, pre-term
- ALL mothers advised not to breastfeed
- increased risk miscarriage, preterm, IUGR

51
Q

HIV structure

A

120nm diameter
2 copies of single-stranded RNA enclosed by capsid
Capsid is viral protein p24 and matrix of viral protein p17
Viral envelope surrounds the matrix, composed of phospholipids and glycoprotein
Glycoprotein enables virus to attach to and fuse with target cells

52
Q

HPV

A

5 groups: α / β / γ / Nu / Mu-papillomaviruses

α-papillomaviruses have 2 subtypes:
- low-risk 6 and 11 -> non-malignant change
- high-risk 16, 18, 31, 33, 45 (via E6 and E7 oncogenes) -> malignant change

Only infect epithelial cells
Structure is 75 capsomeres, each consist of 5 molecules of L1 co-protein, containing circular DNA
- genome of early and late proteins
- causes inactivation of p53 and pRB
- incubation period 2-8months
- regresses spontaneously via cell-mediated immunity (70% within 1 year)
- treatment - podophyllotoxin, imiquimod, cryotherapy

53
Q

Hepatitis viruses

A

Hep A - maternal-fetal transmission rare

Hep B - incubation 6w-6mo
- antigen detection with time progresses surface -> core -> eAntigen
- antibody production (IgM) core -> eAntigen -> surface
- immunity confirmed with anti-surface IgM
- vertical transmission via pregnancy, labour and lactation. Rates depend on viral load and antigen profile
- if e-antigen +ve then 90% transmission, if surface-antigen +ve then 20%
- mostly in 3rdT
- can treat with Interferon α or Lamivudine
- give neonate propyhlactic hepB vaccine and IgG

Hep C - increased risk obstetric cholestasis, 3-5% vertical transmission

Hep E - 5% maternal mortality, fulminant hepatic failure in pregnancy 20%

54
Q

Hepatitis B serology

A

HBsAg (surface antigen)
+ve in acute and chronic infection, -ve if immune or post vaccination

HBeAG (e antigen)
+ve in acute early infection, -ve in chronic/immune/post vaccination

IgM anti-core antibody
+ve in acute infection, -ve in chronic /immun/post vaccination

IgG anti-core antibody
+ve in acute, chronic and immune, negative post vaccination

HepB virus DNA
+ve in acute early and chronic (high infectivity) but -ve in acute resolving, chronic (low infectivity), immune or post vaccination

Anti-HBe Ab
-ve in acute early and post vaccination, can be +ve or -ve otherwise

Anti-HBs Ab
-ve in acute and chronic infection, +ve post vaccination

55
Q

HTLV

A

= human T-lymphotropic virus
0.25% in UK
Feto-maternal transmission via breast milk
Manifestations of congenital infections occur after 10-30 years with T-cell leukaemia, or tropical spastic paraparesis

56
Q

Antibiotic mode of action

A

Penicillins
- Beta-Lactam inhibit peptidoglycan cross-links in bacterial cell wall
- Amoxicillin, Phenoxymethylpenicillin, Flucloxacillin

Cephalosporins
- Beta-Lactam inhibit peptidoglycan cross-links in bacterial cell wall
- Cefalexin,
Ceftriaxone,
Cefuroxime

Macrolides
- Peptidyltransferase Inhibitor
- Erythromycin, Clarithromycin, Azithromycin

Quinolones
- DNA Gyrase Inhibitor
- Ciprofloxacin, Levofloxacin, Moxifloxacin

Tetracyclines
- Bind to 30S subunit of microbial ribosomes blocking attachment of aminoacyl-tRNA to the A site on the ribosome
- Lymecycline, Oxytetracyline, Doxycycline

Nitrofurantoin
- Damages bacterial DNA via multiple reactive intermediaries

Trimethoprim
- Dihydrofolate Reductase Inhibitor

57
Q

Molloscum contagiosum

A
  • viral infection of the skin and occasionally mucous membranes
  • most on trunk, arms, groin, and legs
  • DNA poxvirus MCV, has no non human reservoir
  • spread from person to person by touching the affected skin
  • RFs - sexually active, immunodeficient
  • contagious until the bumps are gone. Some growths may remain for up to 4 years if not treated
  • lesions are flesh-colored, dome-shaped, and pearly in appearance, 1–5 mm in diameter, with a dimpled center, generally not painful, but they may itch or become irritated
  • treatment is supportive
58
Q

Toxic shock syndrome

A

Rare, life-threatening sudden inflammatory response syndrome with fever, rash, hypotension, multi-organ involvement
- assoc with tampons
- usually Staphylococcus aureus -> endotoxin TSST-1
- also streptococcus pyogenes exotoxin A (SPEA) and S pyogenes exotoxin B (SPEB) by group A beta-hemolytic streptococci
- toxins activate production of cytokines, such as tumor necrosis factor, interleukin-1, M protein, and gamma-interferon and induction of nitric oxide production which contributes to hypotension

59
Q

MRSA treatment

A

Best responds to vancomycin or teicoplanin
Resistant to penicillins

Controlled by chlorhexadine wash and mupirocin ointments

60
Q

Beta-lactam antibiotics

A

eg penicillins and cephalosporins (cefalexin, ceftriaxone)
- inhibit bacterial cell wall synthesis by interfering with linking of soluble peptidoglycan precursors
- analogues of d-alanyl-d-alanine
- effective against all gram positive bacteria and gram negative cocci
- excreted by the kidneys
- resistance mainly via beta-lactamase production

61
Q

Glycopeptide antibiotics

A

Vancomycin and teicoplanin
- inhibit bacterial cell wall synthesis by binding to d-alanyl-d-alanine at the end of a pentapeptide chain, preventing the incorporation of new subunits
- cannot penetrate gram negative cell wall, only work against gram positive bacteria
- not absorbed from the GI tract. Oral administration used to treat Clostridium difficile diarrhoea
- potentially ototoxic and nephrotoxic - vancomycin should be administered slowly to prevent ‘red-man’ syndrome. Teicoplanin is less toxic and can be given bolus

62
Q

Aminoglycoside antibiotics

A

Gentamicin, tobramycin, netilmicin, streptomycin
- inhibit bacterial protein synthesis - interfere with the binding of formylmethionyl-transfer RNA to the ribosomes, preventing the formation of the initiation complex
- not absorbed from the GI tract. Do not cross the blood-brain barrier
- not active against streptococci. Active against gram negative bacteria
- excreted via the kidneys
- potentially ototoxic and nephrotoxic
- production of aminoglycoside modifying enzymes is the most important mechanism of acquired bacterial resistance - usually plasmid mediated

63
Q

Tetracycline antibiotics

A

Doxycycline
- inhibit bacterial protein synthesis by preventing aminoacyl tRNA from entering the acceptor site on ribosomes
- absorbed from the gut
- penetrate tissues well and are active against intracellular bacteria
- effective against chlamydial, mycoplasma and rickettsiae infections
- cross placenta - interferes with bone development and cause brown discolouration of teeth - contraindicated in pregnancy and children
- widespread resistance as a result of their use as growth promoters in animal feed - resistance gene carried on a transposon

64
Q

Chloramphenicol

A
  • inhibits bacterial protein synthesis by blocking peptidyl transferase
  • well absorbed from the gut
  • active against a wide range of bacteria. Main indication is the treatment of Salmonella typhi
  • causes REVERSIBLE dose-dependent bone marrow suppression
65
Q

Macroglide antibiotics

A

Erythromycin, azithromycin, clarithromycin and spiramycin
- inhibit bacterial protein synthesis by binding to 23S rRNA, blocking translocation
- well absorbed from the gut; penetrate tissues well and are active against intracellular organisms
- erythromycin is concentrated in the liver and excreted via bile

66
Q

Clindamycin

A

In group of Lincosamides
- binds to 50S ribosomal subunit, inhibiting peptide bond formation.
- similar antibiotic spectrum to erythromycin, excreted by the liver, active in faeces for up to 5 days after a dose
- more active against anaerobes than erythromycin. Clostridium difficile is resistant and may be selected, causing pseudomembranous colitis

67
Q

Iodine

A
  • excellent activity against gram positive and most gram negative bacteria
  • excellent activity against TB, viruses
  • good activity against fungi
  • poorer activity against endospores and markedly affected by organic matter
  • not suitable for use as surgical scrub but can be used for skin prep. Can burn skin so should be removed after several minutes
  • not suitable for use on mucous membranes
  • iodine may be absorbed by the neonate and affect thyroid function
68
Q

Chlorhexadine

A
  • excellent activity against gram positive bacteria but less effective against most gram negative bacteria
  • excellent activity against viruses
  • poor activity against TB and fungi, no activity against endospores
  • only slightly affected by organic matter
  • useful as surgical scrub and skin prep – has high persistent activity
  • suitable for use on mucous membranes
  • toxic to ears and eyes
  • combination with detergents highly effective for hand disinfection.

MRCOG Part 1 (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions