Obstetrics/perinatal infecitions

Question 1

Why are preganant motheres more susceptible to infection?

Answer 1

Changes to hormonal balance and increased demand on the mother, make her more susceptible to certain infections

Examples

Viral hepatitis – viral load fluctuates

Influenza – higher mortality during pandemics

Urinary tract infection – more common

The foetus is protected by amnion and placenta but some pathogens can get through

Question 2

What is the routes of infection from mother to child

Answer 2

Congenital, perinatal, post-natal​

Maternal infections in pregnancy

• can be more severe than usual (malaria, hepatitis)
• latent viruses can reactivate (herpes simplex virus and CMV) infect the foetus
• After delivery uterine tissue is more susceptible to pathogens – puerperal sepsis

> One infected foetus is very susceptible and even if it survives may develop abonrmalities

• maternal HIV infection often causes abortion, prematurity and low birth weight in resource poor countries

Congential Infections

• Occur when baby is in utero
• More sever infections when early in pregnancy –> development
• Often this leads to the death or congenital malformations
• Infant is below weight and fails to thrive

General transmission:

Mother infected –> pathogen in blood –> is able to pass through placenta or establishes infection in placenta invades foetus

Routine antenatal screening is important:

• can identify current asymptomatic infection e.g. Syphilis, hepatitis B or HIV antibodies
• Result in considerable anti-viral HIV therapy for mother & infant
• Previously immunised e.g. against rubella virus

Question 3

For Rubella, describe the causative agent, pathogenesis, clinical features of primary and Congenital Rubella Syndrome, and prevention

Rubella = German measles

Answer 3

• Rash similar in appearance to measles
• Mildest of the common viral skin rashes
• Can result in what is known as Congenital Rubella Syndrome

Rubella virus

• Enveloped RNA virus (Togavirus)
• One antigenic type
• Relatively unstable and easily inactivated

Pathogenesis

• Respiratory transmission
• Replication in nasopharynx and regional lymph nodes
• Viraemia 5-7 days after exposure with spread to tissues
• Placenta and foetus infected during viraemia

Clinical Features

• Generally a mild primary illness with rash and fever
• Major complication is infection early in pregnancy result in transfer to the foetus –> congential rubella syndrome

congential rubella syndrome

• reason for immunising against rubella
• Infection may affect all organs and lead to foetal death or premature delivery
• Severity of damage to foetus depends on gestational age
• Up to 85% of infants affected if infected during first trimester

Clinical consequences: Deafness, cataracts, heart defects, microcephaly, mental retardation, bone alterations, liver and spleen damage

Rubella prevention

Vaccine = live attenuated virus given with MMR or MMRV ( 2 dose schedule)

• Incidence in Australia is very low
• History of rubella means a lot of population are not immune

Question 4

For human CMV, describe the causative agent; in brief: transmission, epidemiology, pathogenesis, prevention and treatment; clinical features of primary and congenital infections

Answer 4

The human cytomegalovirus is the largest member of the Human herpes virus family, HHV-5

• Linear dsDNA, icosahedral, enveloped
• Name derived from the induction of large, multinucleated

Transmission: intimate contact; virus actively secreted in body fluids, inc. saliva, semen, urine, breastmilk

Epidemiology: CMV infection is widespread, with most people becoming infected by old age. Pathogenesis – infects immune cell

Pathogenesis: Infects immune cells (mononuclear cells) and remain for life •

• Remain latent in cell like T cells
• Can reactivate at a later stage

Congenital Cytomegalovirus Infection

Clinical features of primary infection (swollen glands, fever, lethargy)

• Often asymptomatic
• Particularly serious in immunocompromised patients e.g. AIDS

Clinical Consequences of primary maternal infection:

Can result in congenital CMV infection in the foetus (serious during the 1st trisemester of pregnancy)

Prevention and treatment = no vaccine currently; antivirals like ganciclovir and valganciclovir for congenital CMV infections

Question 5

For Listeriosis, describe the causative agent, transmission, clinical features and treatment

Answer 5

Listeria monocytogenes – Gram+ve rod, motile

• Widely distributed: cattle, pigs, rodents and birds as well as plants and soil

Transmission = through contact with with animals or by consumption of unpasteurized milk, soft cheeses or contaminated vegetables (listeria can grow at 4⁰c

Clinical features of primary Listeriosis

• Mild flu-like symptoms or asympotomatic

Major problem during pregnancy –> may cause abortion, premature delivery

Treatment

• Ampicillin
• Avoid certain foods

Question 6

For toxoplasmosis, describe the causative agent, epidemiology, transmission and life cycle, clinical features of primary and congenital infections, prevention and treatment

Answer 6

Toxoplasma gondii – a Protozoan

• Obligate intracellular parasite = complex life cycle

Epidemiology: found worldwide – T. gondii is capable of infecting virtually all warm-blooded animals

• Domestic cats are the only known definitive hosts in which the parasite can undergo sexual reproduction

Transmission

1. usually spread by eating poorly cooked and contaminated food contains cysts
2. exposure to infected cat faeces, containing oocyst
3. from a mother to a child during pregnancy if the mother becomes infected, tachyzoites pass through placenta

Coengenital Toxoplasmosis

• Clinical features of primary infections in children and adults: usually asymptomatic; mild flu-like symptoms
• Clinical feature of congenital toxoplasmosis: blindness, mental retardation, spontaneous abortions
• Symptoms more severe if infection 1st trimester
• Prevention: By properly preparing and cooking food, pregnant woman dont clean cat litter boxes
• Treatment: usually no need for healthy people
• Use folic acid if pregnant if needed

Question 7

Describe the general features of perinatal and postnatal infections and common infections, and puerperal sepsis

Answer 7

• Once foetal membranes are ruptured the foetus becomes more susceptible to bacterial infections
• Infant is frequently exposed upon passage down birth canal to maternal infections
• Neonatal septicaemia(blood poisoning) frequently progresses to bacterial meningitis which is generally fatal if not treated

Perinatal infections: Gonococcal, chlamydial conjunctivitis, E.coli, HIV, HSV

Postnatal infections: HTLV,HIV, CMV, Staphylococci

Maternal infection: Puerperal Sepsis –> Childbed fever major cause of maternal mortality prior to 20th century, acquired from doctors and midwives through poor hygiene

> largely eradicated due to modern medical practice