5 most common hospital acquired infections (HAIs)

5 most common hospital acquired infections (HAIs)

In this article we will the describe 5 most common hospital acquired infections (HAIs).

What is an HAI?

Hospital-acquired infections, also known as healthcare-associated infections (HAI or HCAI), are infections that occur in a healthcare setting.

They can develop either as a result of medical or surgical treatment, or from being in hospital. Doctors consider HAI if someone becomes unwell 48 hours after admissions to hospital. Some people may also become unwell after returning home.

How common are HAIs?

A 2020 study estimated a HAI incidence of 4.7% among 13.8 million adult inpatients in 2016/2017.

And 300,000 people are diagnosed with HCI in England only every year, costing the NHS an estimate of £1-2 billion yearly.

Examples of hospital acquired infections

1. Surgical site infections

Surgical site infections (SSIs) have been shown to compose up to 20% of all healthcare-associated infections. At least 5% of patients undergoing a surgical procedure develop a surgical site infection.

Surgical site infections are commonly caused by organisms that live on the skin such as Staphylococcus aureus (including methicillin resistant Staphylococcus aureus (MRSA)) and Streptococcus pyogenes (Group A Strep).

Symptoms can be recognised when the wound fails to heal, if there is pus coming out of the wound, or redness and pain around the wound site. If severe, bacteria may spread into the blood stream and cause sepsis.

2. Pneumonia

Pneumonia is an infection of lung tissue. It affects the air sacs (alveoli) of the lungs, which fill with microorganisms, fluid and inflammatory cells. It can affect people of any age but can be more serious for the very young or the elderly. Hospital-acquired pneumonia affects 0.5-1.0% of hospitalised patients and is the most common healthcare-associated infection contributing to death.

Staphylococcus aureus, Pseudomonas aeruginosa and other gram-negative bacteria are the most common causes. Hospital-acquired pneumonia is estimated to increase hospital stay by about 8 days and has a mortality of 30-70%.

These figures include hospital-acquired pneumonia that develops in people who are intubated in an intensive care unit. This is known as ventilator-associated pneumonia (VAP) and is clinically distinct from hospital-acquired pneumonia in non-intubated people.

3. Urinary tract infection

Urinary tract infections (UTIs) are caused bacteria in the urinary tract. UTIs can result in several clinical syndromes, including acute and chronic pyelonephritis (infection of the kidney), cystitis (infection of the bladder), urethritis (infection of the urethra), epididymitis (infection of the epididymis) and prostatitis (infection of the prostate gland).

Uncomplicated UTIs typically affect women, children and elderly patients who are otherwise healthy.

Complicated UTIs are usually associated with urinary catheters, urinary tract abnormalities, those with altered immune systems, or exposure to antibiotics. Infection may spread to surrounding tissues (for example, perinephric abscess) or to the bloodstream.

The most common cause for both uncomplicated and complicated UTIs is Escherichia coli (E.Coli).

4. Clostridium difficile 

Clostridium difficile infection (C.diff) is a bacteria that can cause life-threatening diarrhoea. It lives in the lining of the intestines. Usually infection with C.diff is associated with a number of factors.

1. Antibiotic use – antibiotics for other infections kill off normal bacteria in the gut. These antibiotics are not effective against C.diff. There is less competition for nutrients in the gut and therefore C.diff has lots more nutrients than normal and is able to grow and replicate. Some strains can release toxins which is very irritating to the gut wall and causes water to move from the gut wall into the bowel. This leads to watery diarrhoea and dehydration.
2. People over 65 years
3. People staying in hospitals or nursing homes– both symptomatic and asymptomatic people can shed the bacteria into the environment. There is evidence that they can live for up to 5 months in spore form. Being in a hospital is a risk for coming into contact with C.diff spores.
4. Poor hand hygiene – C.diff is not killed with alcohol gel. When coming into contact with a person with C.diff infection. Hence it is important to manually wash the hands thoroughly with soap.

5. Line-associated bloodstream infection

Lines such as cannulas, central lines, Hickmann lines etc are frequently used in a hospitals to give medicines or fluids. They are a pathway from the outside world into the bloodstream.

To mitigate staff will thoroughly clean the skin prior to introducing a line, and will regularly check the insertion site for signs of infection. Bacteria, usually ones that live harmlessly on the skin can get into the blood through the line. Some can form a biofilm – a warm sticky environment where they can replicate and cannot be harmed by antibiotics.

Summary

We have described the 5 most common hospital acquired infections (HAIs). We hope it has been helpful.

Last Reviewed on 8 March 2024