Microbiology Flashcards
What are the consequences of toxoplasmosis in pregnancy?
1) Microcephaly
2) Hydrocephalus
3) Cerebral calcifications
4) Cerebral palsy
5) Epilepsy
6) Choroidoretinitis
7) Thrombocytopenia.
When are fetal consequences most severe in toxoplasmosis?
If transmission occurs in first 10 weeks
When is there the greatest risk of transmission?
Further into the pregnancy, however although the transmission rate increases, the severity decreases with greater gestation
What does HBsAG show?
Acute infection
What does HBeAG show?
Viral replication, and therefore high infectivity
Anti-HBc shows what?
Previous or ongoing infection
Anti-HbsAb shows what?
Either vaccination or immunity following previous infection
What is the most common congenital infection?
CMV
What proportion of children with congenital CMV infection are a) symptomatic at birth? b) symptomatic in later life?
a) 10-15%
b) 10-15%
What infection causes strawberry cervix?
TV
What is the drug combination used in TB?
Rifampicin + Isoniazid + Pyrazinamide + Ethambutol
What are the S/Es of rifampicin?
Orange urine and tears
Hepatotoxicity
What are the S/Es of isoniazid?
Hepatotoxicity
Peripheral neuropathy
What are the S/Es of pyrazinamide?
Hepatotoxicity
Gout
What are the S/Es of ethambutol?
Optic neuritis
What are the polymicrobial causes of endometritis?
Ureaplasma
Gardnerella
Group B Strep
What are the alpha haemolytic streps?
Strep pneumonia
Strep viridans
Which type of bacteria produce endotoxins?
Gram -ve ONLY. Only gram -ve can produce endotoxins, whilst both gram +ve and gram -ve bacteria can produce exotoxins
What is CMV caused by?
Human herpes virus 5
What are the gram +ve bacilli?
Listerias
Clostridiums
Actinomyces’
Mycobacteriums
What are the gram +ve cocci?
Staphylococcus’
Streptococcus’
Enterococcus’
What are the gram -ve bacilli?
Escherichias Enterobacters Klebsiellas Salmonellas Shigellas Campylobacters Legionellas
What are the gram -ve cocci?
Neisserias
Which bacteria is associated with sulphur granules on coils?
Actinomyces israelis
What does the gardasil vaccine consist of?
HPV 6/11/16/18
What proportion of HPV-related cancer is caused by 16 and 18?
70%
What type of vaccine is gardasil?
Vaccine of virus-like particles (VLPs)
What oncoproteins are associated with HPV?
E6 and E7
What tumour suppressor protein is inactivated by E6?
p53
What tumour suppressor protein is inactivated by E7?
pRB
What are the ssRNA viruses?
Hep A/C/D/E
Rubella
HIV
What are the dsRNA viruses?
Rotavirus
What are the ssDNA viruses?
Parvovirus B19
What are the dsDNA viruses?
Hep B CMV HSV HPV EBV VZV
What is group A beta haemolytic bacteria?
Streptococcus pyogenes
What is a group B beta haemolytic bacteria?
Streptococcus agalactia
What is a group C beta haemolytic bacteria?
Streptococcis dysgalactiae
What is a group D beta haemolytic bacteria?
Re-classified as enterococcus
What is a group F beta haemolytic bacteria?
Streptococcus anginosus
What is a group G beta haemolytic bacteria?
No specific name - just group G streptococcus
What does group G streptococcus cause?
Toxic shock
Necrotising fasciitis
Vaginitis
What does Streptococcus anginosus cause?
Liver abscess
What does enterococcus cause?
Colitis
Endocarditis
What does Streptococcis dysgalactiae cause?
Pharyngitis
Endocarditis
Toxic shock
Necrotising fasciitis
What does Streptococcus agalactia cause?
GBS disease of the newborn
Chorioamnioitis
Endometritis
What does Streptococcus pyogenes?
Scarlet fever Rheumatic fever Tonsilitis/pharyngitis Toxic shock Necrotising fasciitis
What is the most common causative organism of cellulitis?
Streptococcus pyogenes
What is the most common causative organism of skin/superficial wound/SSI?
Staphylococcus aureus
What are the treatments for anogenital warts?
1) Podophylline paint
2) 5-FU
3) Trichloracetic acid
4) Liquid nitrogen cryotherapy
5) Imiquimod 5% cream
6) LASER
What are the treatments for anogenital warts not suitable in pregnancy?
Podophylline paint and 5-FU
What is the cause of gas gangrene?
Clostridia perfringens
How is toxoplasmosis treated?
Spiromycin
How is toxoplasmosis diagnosed?
PCR/immunoglobulins, or ring-enhancing lesions on MRI/CT
When are Abx not needed in a GBS +ve pregnancy?
In a planned elective section, in the absence of labour where the membranes are intact
What is the FVS risk in the first 12 weeks of gestation?
0.4%
What is the FVS risk in weeks 13-20/40?
2%
What are the consequences of FVS?
1) hypoplasia of 1 limb
2) CNS abnormalities
2) Eye abnormalities
What is the incidence of listeriosis in pregnancy?
12/100,00. It is 20x more likely in pregnancy
How is listeria treated?
2-3/52 amoxicillin
What does listeriosis in pregnancy cause?
1) Chorioamnionitis
2) Placental necrosis
3) Granuloma formation
What is the fetal mortality of listeria?
20-30%
What infection is blueberry muffin rash associated with?
Congenital rubella syndrome
What is the HIV testing regime of formula fed infants?
During hospital admission
2 weeks post cessation of prophylaxis (age 6 weeks)
2 months post cessation (age 12 weeks)
HIV Ab testing for seroreversion at 18 months
When should children breast-fed by HIV mothers be tested?
As above, but tests additionally every month.
What is the incubation of chickenpox?
14 (10-21)
What is the incubation of rubella?
14 (12-23)
What is the incubation of influenza?
1-3
What is the incubation of parvovirus (fifth disease)?
4-20
What is the incubation of CMV?
3-12/52
What is the risk of congenital CMV with primary infection in pregnancy?
30-40%
What is the risk of congenital CMV with recurrent infection in pregnancy?
1-2%
Which organism causes lymphogranuloma venereum?
Chlamydia trachomatis L1–L3
Which organism causes ocular trachoma?
Chlamydia trachomatis A–C
What type of fungus is Candida albicans?
Yeast-like fungus
How does listeria monocytogenes circumvent the immune system?
It is an intracellular pathogen and ‘hides’ within phagocytic cells
What is the route through which CMV is most commonly transmitted?
Breastfeeding
What proportion of people whom are admitted to hospital develop and hospital-acquired infection?
10%
What pressure do theatre air systems generate and why?
Generates positive air pressure in order to draw air away from the patient so that it may be filtered for airborne infections
How are gram -ve organisms usually spread?
Aerosol route
What may cause sudden deterioration in a Hep B infection?
Delta-virus super-infection, esp. in IVDU’s
Which microorganism most commonly causes catheter-associated UTIs?
Pseudomonas
What is leptospirosis also called?
Well’s disease. It is caused by leptospira which is a spirochaete
What are the zoonoses?
Anthrax (cattle, goats) Listeriosis (pets) Leptospirosis (rats) Toxocara (cats) Toxoplasmosis (dogs) Tapeworms (dogs) Brucella (sheep) TB (cattle)
What type of organism is actinomyces israelii?
Gram positive, cast-forming, non-acid-fast, non-spore-forming anaerobic bacillus
How is actinomyces israelii treated?
Penicillins/cephalosporins. In those that are penicillin allergic, tetracyclines may be used
What are the notifiable diseases?
Food poisoning Haemolytic uraemic syndrome Meningitis Meningococcal septicaemia Rubella Malaria Mumps Measles TB
What bacteria can cause osteomyelitis?
Staphylococcus
Haemophilus influenzae
Salmonella
P. aeruginosa
What happens when blood agar exposed to staph aureus?
Haemolysis
What is the mechanism of action of ciprofloxacin?
Interferes with DNA synthesis by disrupting the function of DNA gyrase
With what stain is toxoplasmosis identified?
Giemsa stain
What is the mechanism of action of glycopeptides (for example, vancomycin)?
Inhibit cell wall synthesis through steric hindrance of peptidoglycans
Which organism causes lymphogranuloma venereum?
Chlamydia
What family of viruses does EBV belong to?
Herpes virus
What are the predominant organisms of the vagina?
Lactobacilli
What is the pH of the vagina during a woman reproductive life?
3.5-4.5
What is the pH of the vagina after menopause?
7 (the bacterial flora become more like the skin again)
What causes the cuboidal epithelium lining the vagina of a child to turn into the stratified squamous epithelium found in the vagina of a woman of reproductive years?
Puberty and the influence of oestrogen
What are the constituents of physiological discharge?
- Desquamated epithelial cells
- Mucus from the cervical glands
- Bacteria - mainly lactobacilli
- Transudate from through the vaginal wall (major constituent)
What are the types of vaginal candidia?
C. albicans - 80% of affected women
C glabrata, C krusei, C tropicalis - remaining 20% of affected women
What factors predispose to vaginal candidiasis?
- Immunosuppression
- DM
- Vaginal douching
- Increased oestrogen levels - e.g. pregnancy
- Broad spec Abx therapy
- Skin conditions
What treatment should be given fro candidiasis in pregnancy?
Clotrimazole 100mg/day pessaries for 7/7. Oral therapies NOT recommended
What is the pH of the vagina in BV?
4.5-7.0 due to the loss of lactobacilli
What are the Amsel criteria for diagnosis of BV?
1) Fishy smell
2) pH>4.5
3) Clue cells
4) Characteristic discharge O/E
What are the complications of BV?
1) Increased risk of second-trimester miscarriage
2) Increased risk of preterm delivery
What medium should be used for culture of TV?
Feinberg-Whittington medium
Which serovars of chlamydia cause LGV?
L1-L3
What is the ‘gold standard’ method of diagnosis of PID?
Laparoscopy
What is Reiter syndrome?
Disseminated infection with chlamydia trachomatis resulting in asymmetrical oligoarthritis of the large joints of the lower limbs, uveitis and a rash
Which is HLA is associated with Reiter syndrome?
HLA B27
What can chlamydia and/or gonorrhoea cause in newborns?
Opthalmia neonatorum - causes keratoconjunctivitis, corneal scarring and blindness. They may also cause pneumonitis in the first few months of life and so newborns with opthalmia neonatorum should recieve systemic therapy with erythromycin
What causes yaws?
Treponema pallidum pertenue
What causes pinta?
Treponema pallidum carateum
What causes bejel (endemic syphillis)?
Treponema pallidum endemicum
Over what period does a chancre appear in syphillis?
3-6/52
What are the conseqences of syphillis for a neonate?
Fetal death
Eight-nerve deafness
Interstitial keratitis
Mulberry teeth
What may be seen on dark-field microscopy in syphillis?
Spirochaetes
What is the Jarisch-Herxheimer reaction?
An exacerbation in symptoms +/- fever that may occur 24 hours after the start of treatment of syphillis. It is due to the release of proinflammatory cytokines following death of organisms.
This reaction may induce preterm labour in a woman with a high organism load when treated in pregnancy.
What disease is ‘groove sign’ associated with?
Lymphogranuloma venereum (LGV) - occurs when the enlargement of LNs in the groin region form buboes which are then compressed by the inguinal ligament
What infection causes chancroid?
Haemophilus ducreyi
What is more common - HIV1 or HIV2?
HIV1
How does HIV gain access to a cell?
The viral outer membrane protein gp120 binds to the CD4 receptors present on T lymphocytes, macrophages etc.
What is the proportion of vertical transmission of HIV if no intervention is made?
25-40% - mainly through transmission from breastfeeding
What should happen if varicella develops at the end of pregnancy?
It may be that the fetus is exposed to infection without the benefit of passive maternal antibodies. Therefore, if maternal infection occurs 7 days before or after pregnancy VZIG should be given to prevent severe infection
What proportion of pregnancies does CMV affect?
0.5%
How is transmission rate and severity related in CMV?
Transmission rate increases the further along the pregnancy, but severity decreases the further along the infection is acquired
What are the possible USS features of CMV?
1) Ventriculomegaly
2) Pseudocysts
3) Microcephaly
4) Intra-cranial calcification
5) Abnormalities of cerebellum
6) Echogenic bowel
7) IUGR
8) Splenomegaly
9) Cardiomegaly/pericardial effusion
10) Hydrops
What are the only infections to be routinely screened for at booking?
HIV
Hep B
Rubella
Syphillis
How do you tell the difference between gram +ve and gram -ve bacteria?
Gram +ve bacteria retain the colour violet dye
Gram -ve bacteria do not retain the violet dye’s colour and instead turn pink with the addition of a counter stain
What are obligate aerobes?
Require the presence of O2 to grow
What are facultative anaerobes?
Can tolerate aerobic and anaerobic conditions
What are obligate anaerobes?
Require the exclusion of O2 to grow
What type of bacteria is listeria?
Gram +ve, rods, facultative anaerobes
What are the 2 types of listeriosis?
Early - occurs within 2 days postpartum, they usually present septic with disseminated organ involvement. mortality is 60%
Late - occurs more than 5 days postpartum, usually as meningitis
What are enterobacteriaceae?
Gram -ve rods that ferment glucose - 2 types, gut commensals and overt bacteria
What are the enterobacteriaceae gut commensals?
E.coli Klebsiellas Proteus Enterobacter Citrobacter
What are the enterobacteriaceae overt bacteria?
Salmonellas
Shigella
Campylobacter
What are the complications of severe malaria?
- Severe anaemia
- Acute pulmonary oedema
- Hypoglycaemia
- Cerebral malaria - reduced GCS and seizures
- DIC
- Acute renal failure - blackwater fever due to intravascular haemolysis
What haematological characteristic is associated with increased incidence of malaria?
Duffy antigen
Are bacteria visible using light microscopy?
Yes
What are the mechanisms of bacterial antimicrobial resistance?
- Drug inactivation
- Alteration of drug target site
- Alternation in the bacteria’s metabolic pathway
- Fibronectin coast
- IgA cleaving protease
How many of the Amsel criteria are required for diagnosis of BV?
3/4
What are Argyll Robertson pupils?
Small, irregularly shaped, difficult to dilate pupils, that may occur as a result of neurosyphillis
What is mycoplasma hominis?
May be a primary or co-pathogen in PID, or a co-pathogen in chorioamnionitis
Which types of chlamydia causes genital chlamydia?
D-K
What is the serology process for diagnosing syphillis?
IgM/FTA-ABS –> IgG –> TPPA –> VDRL
How many organism are required to develop a wound infection?
10 to power 5 (usually), 10 to power 3 in the presence of a foreign body
What is the difference between type 1 and type 2 necrotising fascitis?
Type 1 = associated with surgery/diabetes. Polymicrobial
Type 2 = due to group A streptococcus
What culture does chlamydia grow on?
McCoy’s culture
What are the different types of, and examples of, fungal groups?
- Mould - e.g. aspergillus
- True yeast - e.g cryptococcus
- Yeast-like - e.g. candida
- Dimorphic - e.g. histoplasma
What are the 2 types of protozoa?
- Protozoa
2. Helminths
What are the 3 groups of helminths?
- Fluke
- Tape
- Worm
At what CD4 count foes AIDS occur?
<200
What proportion of Hep B feto-maternal transmissions occur in the 3rd trimester?
90%
What is the Hep B feto-maternal transmission rate when mother is HBeAg positive?
90%