Microbiology Flashcards
When does Rubella infection not cause infection?
Rubella infection that occurs after 16 weeks gestation does not typically cause fetal abnormalities.
When should the rubella vaccine be given to a pregnant woman?
Rubella vaccine is live and should not be given during pregnancy. The mother should be offered vaccination after giving birth.
Is the MMR vaccine safe in breastfeeding?
Yes
Rubella key facts
Caused by rubella virus - a togavirus.
Single stranded RNA genome
Transmission primarily via the respiratory route.
Infection in children and adults usually mild
Where does rubella viral replication occur?
In the nasopharynx and lymph nodes
What is the incubation period of Rubella?
12-23 days (average 14 days)
Congenital rubella infection symptoms?
Congenital rubella infection teratogenic with poor prognosis and significant complications:
Sensorineural deafness
Cataracts
Cardiac abnormalities - most common.
Treatment for rubella congenital infection?
No specific treatment. Key prevention through vaccination programme.
Rubella vaccination in pregnancy?
Vaccination is via live attenuated virus so cannot be given to pregnant women who are found to be non-immune.
What percentage of infants with congenital CMV infection are symptomatic?
10-15% at birth, 10-15% will develop symptoms in later life.
Features of congenital CMV infection
Sensorineural Hearing loss
Visual impairment
Microcephaly
Low birth weight
Seizures
Cerebral palsy
Hepatosplenomegaly with jaundice
Thrombocytopenia with petechial rash
Cytomegalovirus (CMV) Key points
> 50% women seropositive
Congenital CMV infection refers to infection during the perinatal period and tends to effect mothers who have their first CMV infection during pregnancy.
Risk of congenital infection with primary infection of CMV during pregnancy?
30-40%
Risk of congenital infection with recurrent CMV infection during pregnancy?
1-2%
Can CMV be transmitted in breastmilk? T/F
True
What is the incubation period for CMV>
3-12 weeks.
How is fetal CMV infection diagnosed?
Via amniocentesis
When should amniocentesis be performed in fetal CMV infection?
Amniocentesis should be not be performed for at least 6 weeks after maternal infection and not until the 21st week of gestation.
What is the mortality rate of treated disseminated neonatal herpes?
30%
Herpes simplex in pregnancy key facts
- Type 1 and 2 (type 2 accounts for 70% of genital herpes infections)
- Double stranded DNA virus
How is herpes simplex virus transmitted?
HSV infection may be transmitted to neonates. Transmission is typically due to the neonate coming into contact with infected maternal secretions during delivery (transplacental infection reported but very rare).
When is the risk of primary herpes infection highest?
Highest risk with primary herpes infection within 6 weeks of delivery. Viral shedding can continue after lesions have healed.
How common is neonatal herpes?
Rare - UK incidence 3/100,000 live births
What are the 3 types of neonatal herpes?
- Restricted to skin/superficial infection (eye/mouth) - least severe.
- CNS infection (mortality with antiviral treatment 6% neurological sequelae 70%)
- Disseminated infection (mortality with antiviral treatment 30% neurological sequelae 17%)
- 70% of cases are disseminated or CNS involvement
Management 1st or 2nd trimester acquisition of genital herpes (Joint BASHH/RCOG guidance Oct 2014)
- Initial episode treated aciclovir 400mg TDS for 5 days.
- Following 1st or 2nd trimester acquisition, daily suppressive aciclovir 400mg TDS from 36 weeks of gestation reduces HSV lesions at term and hence the need for delivery by c-section
Management of 3rd trimester acquisition of genital herpes (from 28 weeks)
- Initiate aciclovir 400mg TDS and continue until delivery
- C-section delivery is advised for these patients in whom this is a 1st episode of HSV.
Anogenital wart contraindicated treatment in pregnancy?
Podophylline paint and 5-fluorouracil- teratogenic.
HPV Vaccine
Gardasil - is quadrivalent vaccine against HPV types 6,11,16 and 18
What types of HPV is responsible for HPV related cancers?
HPV types 16 and 18 are responsible for 70% of cases of HPV related cancers.
What types of cancers are HPV types 16 and 18 responsible for?
Cervical cancer and oropharynx and anogenital region
How does HPV cause cancer?
HPV is thought to induce cancer via onco-proteins. The primary onco-proteins are E6 and E7 which inactivate two tumour suppressor proteins, p53 (inactivated by E6) and pRb (inactivated by E7).
How does HPV cause cancer?
HPV is thought to induce cancer via onco-proteins. The primary onco-proteins are E6 and E7 which inactivate two tumour suppressor proteins, p53 (inactivated by E6) and pRb (inactivated by E7).
Which are the low risk HPV genotypes?
6 and 11 are low risk and cause anogenital warts
What percentage of HPV infections are cleared?
Typically 70% of HPV infections are cleared within 1 year and 90% are cleared within 2 years.
What is chancre?
A hallmark of primary syphillis.
Chancres are painless ulcers that typically develop around 3 weeks after sexual contact with an infected individual. They range from 3mm to 3cm in size.
What is Syphillis?
Caused by the bacteria Traponema pallidum
Primary syphilis facts:
Time from primary infection: 3-90 days.
Symptoms: Chancre and lymphadenopathy
Secondary syphilis facts:
Time from primary infection: 4-10weeks
Symptoms: Widespread rash typically affecting hands and soles of feet. Wart lesions (condyloma latum) mucus membranes.
Latent syphilis facts:
Time from primary infection: Early <1year after secondary stage. Late >2 yrs after secondary stage.
Asymptomatic
Tertiary syphilis facts:
3+ years after primary infection
Symptoms: Gummas OR Neurosyphilis OR Cardiovascular syphilis
Chicken pox incubation period (days)
14 (10-21)
Rubella incubation period (days)
14 (12-23)
Influenza incubation period (days)
1-3
Parvovirus (fifth disease) incubation period (days)
4-20
Streptococcus pyogenes (Scarlet fever) incubation period (days)
1-7
When may congenital fetal varicella syndrome occur?
If there is maternal varicella infection (chickenpox) during the 1st 20 weeks of gestation.
What is the risk of fetal varicella syndrome?
To mothers who have chickenpox during the first 20 weeks gestation is 0.4% (1-12 weeks) - 2.0% (13-20weeks)
When is there a risk of neonatal varicella infection?
If a mother has chickenpox in late pregnancy (5 days prior to delivery). Risk may be severe.
What abnormalities can fetal varicella syndrome cause?
Hypoplasia of one limb
Cicatricial lesions with a dermatomal distribution
CNS abnormalities
Eye abnormalities
What virus causes chicken pox and shingles?
Varicella Zoster
Should VZIG be used in pregnant women who developed a chickenpox rash?
No - no therapeutic benefit (Green top guidelines)
Who should be given intravenous aciclovir?
All pregnant women with severe chickenpox
When should oral aciclovir be given to pregnant women?
If they present within 24 hours of the onset of the rash and if they are 20+0 weeks of gestation or beyond. Use of aciclovir before 20+0 weeks should also be considered.
According to NICE what should be used for wound cleaning for the first 48 hours postoperatively?
Sterile saline
When may patients shower after surgery?
After 48 hours.
What should be used to clean a wound if the surgical wound has separated/has been surgically opened to drain pus after 48 hours?
Tap water
Antimicrobial agents and surgical wounds
Do not use antimicrobial agents for wounds that are healing by primary intention to reduce the risk of surgical site infection.
What is recognised as the most frequent cause of severe early onset infection in newborns?
Group B streptococcus (streptococcus agalactiae) - early onset (<7 days old)
How should women with a previous baby with neonatal GBS disease be treated?
Intrapartum antibiotics should be offered (even if current swabs are negative for GBS).
IV benzylpenicillin is 1st line. A cephalosporin or vancomycin is advised if penicillin allergic.
Listeriosis key points
Listeria monocytogenes causative organism
Source usually food, typically soft cheeses or cold meats.
Fetus can be infected via transplacental or ascending spread
Typically mild illness in adults unless immunocompromised
Incidence of listeriosis?
Incidence in pregnancy is around 12 per 100,000
20x more likely in pregnancy than in general population 0.7 per 100,000
Listeriosis side effects in pregnancy?
Causes chorioamnioitis and placental necrosis and granuloma formation.
Miscarriage, still birth and meningitis can result from listeria infection during pregnancy
What is fetal mortality rate in listeriosis?
Quoted at 20-30%. (up to 50%)
How is listeriosis treated?
Typically with amoxicillin for 2-3 weeks.
Gram positive obligate anaerobe?
Clostridium
Gram negative obligate anaerobe?
Bacteroides (also called prevotella)
Other obligate anaerobes? (less clinically relevant)?
- Porphyromonas gingivalis causes gingivitis
-Peptostreotococcus typically commensal - Actinomyces mostly facultative, one strain is an obligate anaerobe
Gram positive cocci?
- Staphylococcus facultative anaerobes
- Streptococcus facultative anaerobes
Gram positive bacilli OR rods?
- Corynebacterium facultative anaerobe
- Listeria non-spore forming FA
- Bacillus spore forming FA
- Clostridium spore forming obligate anaerobe
- Actinomyces spore forming FA