10 Most Common Pathogens That Causes HAIs

Know your enemy: the 10 most common pathogens that cause hais

Healthcare-associated infections (HAIs) continue to trouble the healthcare industry. The Centres for Disease Control and Prevention (CDC) estimates that on any given day, about 1 in 31 hospital patients has at least one healthcare-associated infection (CDC, 2020), while the incidence of HAIs in Australia may be closer to 165,000 per year (Mitchel et al., 2017). Unfortunately hospitals are a great breeding ground for infections. Many patients, often with community-acquired infections, are grouped together in close quarters with those suffering suppressed immune systems, leaving those patients highly susceptible to infection (Colins, 2008). Here are 10 of the most common HAIs found in Australia.

1. Methicillin-resistant Staphylococcus Aureus (MRSA)

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MRSA is an opportunistic strain of staphylococcus aureus found in healthcare facilities that has resistance to some commonly used antibiotics (Stapleton et al., 2002). It often manifests itself in the form of skin infection in most patients like sores, boils, or abscesses (CDC, 2020).

Commonly spread by direct or indirect contact transmission e.g. from using or touching objects used by a person infected with MRSA (CDC, 2020), MRSA is very prevalent in Australia (more than 10,000 cases per year) (AIWH, 2017)and can last for several weeks to months. They are typically more common in females and may be dangerous or life-threatening in some cases.

2. Vancomycin-resistant Enterococci (VRE)

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VRE is an enterococcus with a developed resistance to the antibiotic vancomycin. It naturally lives in the intestines and can cause symptoms like an upset stomach, minor vomiting, occasional diarrhea, or more serious ailments such as peritonitis in weak patients, which is very difficult to treat (Cetinkaya, 2000),. Infections of this nature are most common in medical settings, especially when a patient is admitted to the hospital for long-term care and nursing. VRE can spread from one person to another through contact with contaminated surfaces, equipment or through person to person spread, often via contaminated hands. VRE is not spread through the air by coughing or sneezing (CDC, 2020).

3. Vancomycin-intermediate or Vancomycin-resistant Staphylococcus Aureus (VISA or VRSA)

Known in the medical community as either VISA or VRSA, these two forms of Staphylococcus are so named because they are moderately or entirely resistant to the antibiotic vancomycin (Gardete & Tomasz, 2014). As of October 2010, all VISA and VRSA isolates have been susceptible to several Food and Drug Administration (FDA)-approved drugs (CDC, 2020).  Unlike viral infections, however, bacterial infections can occur again at any time (Healthdirect, 2020). For this reason, increased vigilance is urged to those who are connected to medical devices that penetrate the skin, enter the body, and assist with daily functions like kidney function, urination, drips, etc (CDC, 2020). The spread of this type of infection can occur among people having close physical contact with infected patients or contaminated materials. Persons having close physical contact with infected patients while they are outside of a healthcare setting should keep their hands clean by washing thoroughly with soap and water, and avoid contact with other people’s wounds or materials contaminated from such wounds (CDC, 2020).

4. Pseudomonas aeruginosa

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Pseudomonas aeruginosa is an opportunistic bacterium which targets patients with weakened or suppressed immune systems.  It can cause infections in the blood, lungs (pneumonia), or other parts of the body after surgery. Due to the high concentration of potential hosts, hospitals are commonplace for Pseudomonas infections to spread. With certain strains showing resistance to beta-lactam and other antibiotics (Kong, 2010), P. aeruginosa can spread in healthcare settings from one person to another through contaminated hands, equipment, or surfaces. Those most at risk include patients in hospitals, especially those on breathing machines (ventilators), attached to medical devices such as catheters, or with wounds from surgery or burns. Healthy individuals rarely contract Pseudomonas infections Treatment of this bacterial infection is generally pursued through the prescription of high dosage antibiotics, with the problem generally easing within 24 to 48 hours of first treatment. Patients and caregivers should keep their hands clean to avoid getting sick and clean their rooms daily when in healthcare settings (CDC, 2020).

5. Clostridium difficile ( C.diff)

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Clostridium difficile, also known as Clostidioides difficile, is a spore-forming bacterium found in the intestines that causes diarrhea and can lead to the life-threatening inflammation of the colon called colitis (Hookman & Barkin, 2009). C. difficile bacteria are found throughout the environment — in soil, air, water, human and animal faeces, and food products such as processed meats. Spores from C. difficile bacteria are passed through the body by faeces and spread to food, surfaces, and objects when people who have contaminated hands do not wash them thoroughly (Mayoclinic, 2020). These spores can persist in a room for weeks or months. Infection can then occur by touching your mouth after touching a surface contaminated with C. difficilespores. Most C. difficile infections occur in people who are or who have recently been in a health care setting — including hospitals, nursing homes and long-term care facilities — where germs spread easily through direct or indirect contact transmission.

C. diff bacteria is commonly found in the environment, but most cases of C. diff occur while you’re taking antibiotics or not long after you’ve finished taking antibiotics. People are 7 to 10 times more likely to get C. diff while on antibiotics and during the month after (CDC, 2020). That’s because antibiotics that fight bacterial infections by killing bad germs can also get rid of the good germs that protect the body against harmful infections, like C. diff infection (CDC, 2020).

While extremely contagious, it can be prevented by diligent hand washing after using the bathroom or toilet and especially before eating. Using separate bathrooms and toilets from patients or residents who have diarrhea also helps minimise the spread of C. difficile to others.

6. Escherichia coli (E.coli)

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Escherichia coli is a bacteria that is commonly found in the lower intestine of warm-blooded organisms (WHO, 2018) and while most are harmless, some can cause serious food poisoning. Shiga toxin-producing E. coli (STEC) is a bacterium that can cause severe foodborne disease (Paton, 1998) and is often found in undercooked meat products, raw milk or transferred while using the toilet. Verodoxin-producing E. coli destroy blood vessel walls in the large intestine, causing severe abdominal pain, and is most frequently transmitted via the consumption of contaminated food or water (Lim et al., 2010). Transmission can also occur directly from person to person, particularly in child day-care facilities, and from animal to person (Lim et al., 2010). The best ways to prevent the spread of E. coli is thoroughly cooking ground beef, avoiding unpasteurized milk, and washing hands carefully.

7. Norovirus

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Norovirus is a bacterium which causes inflammation in the lower large intestines (Robilotti et al., 2015) and is usually acquired from raw shellfish or an infected person’s vomit or faeces (CDC, 2020). Norovirus infections typically result in diarrhea, vomiting, and the long-lasting feeling of an upset stomach. These symptoms are exceedingly unpleasant and may last for several days at a time, which could lead to serious dehydration of the body (CDC, 2020). With only a few virus particles needed to infect someone, norovirus infections can spread very rapidly with billions of norovirus particles shed by those sick when infected. Norovirus is transmitted through putting your unwashed hands in your mouth after person-to-person contact or by touching contaminated surfaces (CDC, 2020). As a non-enveloped virus, it has a strong resistance against many disinfectants (Howie et al., 2008).

8. Mycobacterium abscessus

Mycobacterium abscessus is a bacterium distantly related to the ones that cause tuberculosis and Hansen’s Disease (Leprosy). It is part of a group of environmental mycobacteria and is found in water, soil, and dust and has even been known to infect medications and reside on medical equipment. Infection usually occurs in the skin and soft tissue under the skin and can result in serious lung infections. People with open wounds, those that undergo invasive medical procedures or who receive injections without appropriate skin disinfection may be at risk of infection. Anyone who touches or cares for the infected site should wash their hands carefully with soap and water, while patients should follow all instructions given by their healthcare provider following any surgical or medical procedure.

9. Influenza virus (flu)

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Influenza (commonly called the flu) is an infectious respiratory condition caused by influenza viruses. Unlike the common cold, influenza (flu) can lead to serious health complications such as pneumonia, otitis media, and even death (Australian Government Department of Health, 2021). With continual minor mutations, it brings about seasonal epidemics every year. Most experts believe that flu viruses spread mainly by tiny droplets made when infected person cough, sneeze or talk, which can then land in the mouths or noses of people who are nearby. The best prevention method is to keep up-to-date with your annual flu vaccination and wash your hands thoroughly when visiting a healthcare facility.

10. Mycobacterium Tuberculosis (TB)

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Mycobacterium tuberculosis (M. tuberculosis [TB]) is a recognised risk to patients and healthcare personnel in healthcare settings (CDC, 2020). Transmission is most likely to occur from patients who have undiagnosed pulmonary or larynx-related TB, are not on effective anti-TB therapy, and have not been placed in TB isolation. In healthcare settings, the transmission of M. tuberculosis has been associated with the close contact of those who have infectious TB, particularly during the performance of cough-inducing procedures such as bronchoscopy and sputum induction. TB can spread through the air and can travel long distances (CDC, 2020).


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