Introduction

Brief overview of Salmonella infection

Salmonella infections are a range of infections caused by several types of salmonella bacteria. The infections can range from salmonellosis which is associated with mild abdominal symptoms to severe diseases like enteric fever (typhoid fever). Pregnancy is a delicate time in the lives of both mother and baby. Any infection that develops during this period is usually a source of concern due to the consequences. 

Importance of awareness during pregnancy

The immune system of a pregnant woman is adapted to prevent the mother’s body from rejecting the unborn baby. Because of this, pregnant women have a reduced ability to fight infections. Therefore Salmonella infection during pregnancy can cause very severe infections to the mother. In addition, it could also affect the unborn baby leading to complications while the baby is still in the womb or after birth. To ensure good pregnancy outcomes for the mother and baby, we need to understand the risks associated with Salmonella infection during pregnancy. This understanding would help us to put in place effective prevention strategies and management. 

What is salmonella?

Salmonella is a large group of bacteria that infect the digestive system. The organism thrives in locations with reduced oxygen levels. They produce some proteins called the O, H and Vi antigens.¹ These antigens are responsible for the inflammatory damages caused by Salmonella in the digestive system and other parts of the body.

Salmonella bacteria are classified into typhoidal or non-typhoidal salmonella depending on their distinctive surface chemical structure (serotype). Typhoidal salmonella are those that cause typhoid or paratyphoid fever. These include the Typhi and Paratyphi serotypes respectively. The nontyphoidal Salmonella refers to the other Salmonella Serotypes.^2,3 

Common sources of salmonella infection

Salmonella is usually transmitted through the ingestion of contaminated food and water. You can get salmonella if you eat unhygienically processed food or ingest raw or undercooked food. Examples of such food include:

• Meat
• Eggs
• Cheese
• Milk 

Salmonella lives in the intestinal tract of animals so you can also contract salmonella if you get in contact with the excreta of animals (such as poultry, swine, cattle etc.) infected with salmonella.⁴ 

Infected food handlers can also spread salmonella. Mary Mallon, an Irish cook who lived in the USA, was a healthy carrier of Salmonella typhi and was reported to have infected several people.⁵ This earned her the nickname “Typhoid Mary”.

What is the distribution of salmonella infection?

In 2007, the reported annual incidence of salmonellosis in the US was 14.9 cases per 100,000 population.⁶  Reports show that the incidence has remained stable since 2004. Because of poor surveillance resulting in a lack of capacity, there is a lack of high-quality data on the incidence in some other countries. However, there is evidence of decreasing incidence globally. Reports by the World Health Organization show that as of 2019, there are 9 million cases of typhoid fever annually, resulting in about 110,000 deaths per year.⁷ It is not associated with particular races or gender. The very young, the elderly, those with reduced immunity and individuals with other coexisting diseases are more susceptible. 

Salmonella and pregnancy: risks

Risk to the mother

There is an increased susceptibility to salmonella in people with reduced immunity, including pregnant women whose ability to fight infection is reduced. You are more prone to salmonella during pregnancy due to the reduced ability of the pregnant woman to fight infections. The infection can cause severe dehydration, abnormality in the concentration of electrolytes in your body and blood infection and can affect multiple organs.

Risk to the baby

Salmonella can increase the risk of miscarriage and premature delivery. It can also cause the death of the baby due to bacteria being present in the blood. Reports show that it also causes a reduction in the birth weight of the baby.⁸ Bentacourt and his associates in their study found that salmonella colonisation of the placenta changes the morphology (structure) of the placenta thereby leading to reduced blood supply to the baby. This leads to a drop in the unborn baby’s weight.⁹ An animal study done by Branca and his team in pregnant mice shows that there is a higher accumulation of bacteria in the spleen and reduced production of inflammatory markers that help to control infection. They also found increased accumulation in the placenta leading to an increase in the risk of miscarriage (loss of the developing baby).¹⁰ The infection can also increase the risk of infection at birth (sepsis). This leads to the death of the newborn.¹¹ It may also lead to meningitis (inflammation of the coverings of the brain and spinal cord) in the newborn, which if not well treated may have long-term effects.

How does salmonella cause infection?

Due to the acidity of the stomach, a large number of Salmonella is needed to cause infection. Once ingested, the bacteria pass from the stomach into the small intestine, where they attach to the inner lining using tiny hair-like projections on its surface called fimbriae or pili. The bacteria are then internalised into the intestinal wall, triggering the immune system. From there, the infection can spread to other organs like the liver, spleen and bone marrow. In some individuals, it spreads to the gallbladder, leading to long-term storage in the bile. This increases the risk of asymptomatic infection and chronic carrier state. If untreated, the infection spreads to the blood within 14 days. Typhoidal Salmonella has a greater tendency to spread beyond the gut when compared to nontyphoidal Salmonella.

Symptoms of salmonella infection

Salmonella usually causes infection in the digestive system but it can also affect the urine, blood, joints, bones and even some parts of your nervous system. Symptoms such as diarrhoea, pain in your abdomen and fever may suggest that you have salmonella infection. Other symptoms include headache, weakness, dry cough and vomiting. You may also develop some red spots on the trunk (rose spots). This is due to the spread of bacteria to the skin.

When to seek medical attention

It is recommended that as a pregnant woman, you should seek medical care once you develop any of these symptoms. Other groups that should seek help early include those with weakened immune systems, the elderly, children, and those with other concomitant diseases.

Diagnosis and treatment

How is salmonella infection diagnosed during pregnancy?

The diagnosis of salmonella in pregnancy is not different from non-pregnant patients. To make the diagnosis, your stool samples will be collected and sent to the laboratory for culture, if there is suspicion of spread to the blood, blood samples can be collected as well.² The diagnosis is confirmed if the culture detects salmonella in the stool and blood.

Treatment options and considerations for pregnant women

You may recover from uncomplicated non-typhoidal salmonella infection without any treatment, especially if you are not pregnant. Intake of fluids is needed while the diarrhoea lasts to prevent dehydration. In severe diseases, antibiotic treatment would be prescribed by your doctor. Intravenous fluids (drips) may be needed to combat dehydration

Drugs like ampicillin and cotrimoxazole have been used in the past, but newer and better forms of antibiotics like cephalosporins are currently preferred. This is due to increased drug resistance and side effects associated with some of the medications. Your doctor will use the culture sensitivity results to determine the best antibiotics for you.

The treatment of Salmonella during pregnancy is controversial. It recommended that antibiotic treatment should be reserved for diseases that have spread beyond the intestine (invasive disease)⁶. Salmonella can sometimes cause intestinal perforation or affect organs like the heart (endocarditis) and the bone (osteomyelitis) or lead to abscess formation. In such cases, surgical treatment may be prescribed by your doctor. 

As part of the treatment, a doctor will also monitor your baby to make sure they are in good condition. This is very important if you have a severe infection. Monitoring may involve checking the baby’s heart rate and performing periodic ultrasound scans.

Preventing salmonella infection during pregnancy

To prevent salmonella there is a need to take dietary precautions and to pay close attention to food safety and hygiene. 

Food safety tips for pregnant women

The food safety tips include:

• Avoid unpasteurised (not heated at a controlled temperature) foods.
• Keep raw meat and poultry separate from other foods
• Wash raw fruits very well before eating 
• Avoid eating raw eggs
• Prevent cross-contamination of surfaces with raw food  
• Cook and preserve food at the appropriate temperatures

Hygiene practices to minimise infection risk

Hygiene practices include:

• Wash your hands regularly before and after eating
• Wash your hands after contact with animals 
• Minimise contact with animals that have diarrhoea
• Avoid eating near animals
• Keep food preparation areas clean by washing kitchen utensils and surfaces
• Avoid the cross-contamination of surfaces with raw food

Vaccination

The typhoid vaccine is not mandatory in many countries but may be required when travelling to areas with a high risk of typhoid fever. The typhoid conjugate vaccine is safe during pregnancy. It is recommended to receive it two weeks before the planned trip. The vaccine does not provide lifelong immunity and is 50-80%effective.

What to do if exposed to salmonella during pregnancy

Steps to take if exposed to salmonella

If you develop symptoms that look like that of salmonella during pregnancy, you should take a lot of fluids and rest. In most cases, the symptoms may resolve on their own and fluids will help to replace those lost through diarrhoea. However,  it’s advisable to consult your doctor early on.  

When to contact a healthcare provider

You should contact your health provider if symptoms persist or worsen. If the infection becomes severe, a doctor who specialises in the treatment of infectious diseases (an infectious disease specialist) will be needed to take care of you.

Conclusion

Salmonella infection is a relatively common infection. In most cases, it causes mild, self-limiting infection. In some cases, it can lead to severe disease that would require antibiotics and even hospitalisation. Pregnant women are particularly susceptible due to reduced immunity and the infection can also affect the baby by causing miscarriage or even the death of the newborn. Seeking early management will lead to a reduction in complications. Healthcare providers and educators are very critical in the management as they play an important role in educating pregnant women about the risks of Salmonella infection including preventive and management strategies. 

FAQs

What happens if a person gets salmonella?

You may develop diarrhoea, fever and abdominal cramps. This may last for a few days and may resolve without antibiotic treatment. However, it may progress to severe infection in some cases.

How should I treat salmonella?

The disease is usually mild (associated with mild abdominal symptoms) and resolves with non-specific treatment. Severe infections would require antibiotic treatment (prescribed by your doctor) and even hospitalisation.

Can salmonella harm my unborn baby?

Yes, Salmonella can harm an unborn baby. It may lead to complications such as miscarriage, preterm labour, or low birth weight.

Does drinking water flush out salmonella?

Drinking water does not flush out salmonella but it helps you to keep hydrated