What is Legionella Bacteria

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What is Legionella Bacteria?

Understanding what is Legionella bacteria is vital for public health. Legionella bacteria cause Legionnaires’ disease and Pontiac fever, which are significant health concerns worldwide, especially in the United Kingdom.

This detailed review explains what is Legionella bacteria in terms of its biological features, how it causes disease, its spread, and its environment. It also looks at the current UK rules, including the Health and Safety at Work etc. Act 1974 and the Control of Substances Hazardous to Health (COSHH) Regulations, highlighting the important role of the Approved Code of Practice (ACOP) L8 in reducing risks linked to what is Legionella bacteria in water systems.

Background Information

To understand what is Legionella bacteria, we need to look at its history and importance. Legionella bacteria, first found after a 1976 outbreak in Philadelphia, USA, are rod-shaped bacteria that cause a group of breathing illnesses called legionellosis.

The most serious form, Legionnaires’ disease, is a potentially deadly type of pneumonia, while Pontiac fever is a milder, short-lasting flu-like illness.

Legionella Bacteria - 1970S Philadelphia

In the UK, knowing what is Legionella bacteria is crucial, as it’s a significant public health issue. The Health and Safety Executive (HSE) reports an average of 200-250 confirmed cases of Legionnaires’ disease each year, showing the need for strict control measures and following regulations.

Taxonomy and Characteristics

When exploring what is Legionella bacteria, it’s important to understand its classification and unique features. Legionella belongs to the Legionellaceae family. There are over 60 types of Legionella, with Legionella pneumophila being the main one that makes humans sick, causing about 90% of legionellosis cases.

These bacteria are typically 0.3-0.9 μm wide and 2-20 μm long, with a single tail-like structure for movement. Genetically, what is Legionella bacteria can be identified by its unique genetic makeup, which helps in classifying and finding it in labs. Understanding these characteristics is crucial for effective detection and control strategies.

How Legionella Causes Disease

Understanding what is Legionella bacteria involves looking at how it causes illness. When someone breathes in contaminated water droplets, Legionella bacteria are taken up by immune cells in the lungs. Unlike most bacteria, Legionella can avoid being destroyed inside these cells and instead multiply.

This process is controlled by a special system in the bacteria that injects over 300 proteins into the host cell, changing how it works to help the bacteria survive and grow.

In Legionnaires’ disease, the growth of bacteria in lung cells leads to severe inflammation and damage, causing pneumonia. Pontiac fever, on the other hand, is thought to be caused by the body’s quick reaction to Legionella proteins without the bacteria actually growing, which is why it doesn’t last as long.

Understanding these mechanisms is crucial for developing effective treatment strategies and preventive measures against what is Legionella bacteria.

Spread of the Disease

To fully grasp what is Legionella bacteria, we need to look at how it spreads and its impact around the world.

In the UK, doctors must report legionellosis cases to health authorities. Public Health England data shows that Legionnaires’ disease cases in the UK have slowly increased over the last ten years, with about 0.5-0.7 cases per 100,000 people each year.

Notable UK outbreaks include one in Barrow-in-Furness in 2002, which caused 7 deaths, and another in Edinburgh in 2012, affecting 92 people.

Globally, the World Health Organisation estimates that Legionella bacteria causes 2-15% of community-acquired pneumonia cases needing hospital care in Europe and North America. However, the true number is likely higher because it’s often hard to diagnose and report. This underscores the importance of continued research and monitoring efforts to fully understand the spread of Legionella bacteria.

How Legionella Spreads

What is Legionella bacteria’s way of spreading? Legionella bacteria are common in natural water sources but rarely cause disease there. People usually get infected by breathing in contaminated water droplets from man-made water systems.

Common sources include cooling towers, evaporative condensers, hot and cold water systems, spa pools, and indoor fountains.

The risk of Legionella bacteria spreading is affected by several factors:

Water temperature: It grows best between 20°C and 45°C.
Stagnant water: Areas with low water flow help bacteria grow.
Presence of nutrients: Including sediments, limescale, and other microbial growth.
Biofilm formation: Provides protection and food for Legionella.
Creation of water droplets: Necessary for breathing in and getting infected.

Legionella doesn’t spread from person to person, which is why controlling the environment is crucial for prevention.

Legionella in the Environment:

Understanding what is Legionella bacteria requires knowledge of how it lives and survives in the environment. Legionella bacteria live inside single-celled organisms called amoebae in natural water sources. This relationship provides food for bacterial growth and protects against harsh conditions and disinfectants. In man-made water systems, Legionella can grow in biofilms, which are complex communities of microorganisms that stick to surfaces.

The best conditions for what is Legionella bacteria to grow include:

Temperatures between 20-45°C, growing fastest at 35-37°C.
pH levels between 5.5-9.2, with best growth at 6.8-7.0.
Dissolved oxygen levels of 6.0-6.7 mg/L.
Presence of essential nutrients, including iron and L-cysteine.

Understanding these preferences is crucial for implementing effective control strategies in water systems and reducing the risks associated with Legionella bacteria.

Detection and Diagnosis:

To effectively manage what is Legionella bacteria, proper detection and diagnosis are crucial. Laboratory detection of Legionella involves several methods:

Culture: Growing the bacteria in a special medium.
Polymerase Chain Reaction (PCR): Quickly detecting Legionella DNA.
Direct Fluorescent Antibody (DFA) staining: For seeing the bacteria in clinical samples.
Urinary Antigen Test: Quickly detecting a specific type of Legionella.

Diagnosing Legionnaires’ disease requires both symptoms (like high fever, cough, shortness of breath) and laboratory confirmation. In the UK, confirming Legionella bacteria infection includes finding pneumonia on a chest X-ray and at least one of the following: isolating Legionella from respiratory samples, detecting Legionella in urine, or a significant increase in specific antibodies in the blood.

UK Rules and Definitions

Understanding what is Legionella bacteria is essential for following regulations. The UK has strict rules for Legionella control, based on the following regulations:

Health and Safety at Work etc. Act 1974: Provides the main legal framework for workplace health and safety.
Control of Substances Hazardous to Health (COSHH) Regulations 2002: Requires employers to assess and control risks from dangerous substances, including what is Legionella bacteria.
Management of Health and Safety at Work Regulations 1999: Requires risk assessments and implementation of appropriate control measures.

A key document for Legionella control is the Approved Code of Practice (ACOP) L8: ‘Legionnaires’ disease: The control of Legionella bacteria in water systems’. This provides practical guidance on following health and safety laws regarding risks associated with what is Legionella bacteria. Key aspects include:

Risk assessment requirements and methods.
Management responsibilities and competence.
Control measures for various water systems.
Monitoring and record-keeping protocols.

People responsible for buildings, including employers, landlords, and those in control of premises, have specific duties under UK law regarding what is Legionella bacteria:

Identify and assess sources of risk.
Prepare a plan for preventing or controlling the risk.
Implement and manage precautions.
Keep records of precautions taken.
Appoint a competent person with sufficient authority and knowledge to help implement the control measures.

Prevention Strategies

Knowing what is Legionella bacteria helps in implementing effective prevention strategies. Controlling Legionella in water systems involves several approaches:

Temperature control: Keep hot water above 60°C and cold water below 20°C.
Regular flushing of outlets: Prevent water from standing still.
Proper design and maintenance of water systems: Minimise areas of low water flow.
Water treatment: Including use of disinfectants, UV light, or copper-silver ionisation. See more below.
Regular cleaning and disinfection of water systems.
Monitoring and record-keeping: Including temperature checks and Legionella testing.

Treatment of Legionella in Water Systems

Understanding what is Legionella bacteria is crucial for effective remediation in water systems. Treatment methods include:

Temperature Control: – Maintain hot water above 60°C and cold water below 20°C.
Chemical Treatment: Chlorine, chlorine dioxide, or copper-silver ionization.
Physical Methods: UV light disinfection and filtration.
Cleaning and Disinfection: Regular cleaning of high-risk systems and removal of sediment and biofilm.
System Design and Maintenance: Eliminate areas of low water flow and ensure proper insulation.

Treatment typically involves an initial shock treatment followed by ongoing maintenance. The choice of method depends on the system type, size, and contamination level. Often, a combination of methods is most effective.

Regular monitoring and testing are essential, as complete eradication of what is Legionella bacteria is often not possible. Any treatment program should be part of a comprehensive water management plan, as outlined in the ACOP L8 guidelines.

References:

Health and Safety Executive. (2013). Legionnaires’ disease: The control of Legionella bacteria in water systems. Approved Code of Practice and guidance on regulations (L8). HSE Books.
Public Health England. (2020). Legionnaires’ disease in England and Wales: 2019. Health Protection Report, 14(21).
Khodr, A., et al. (2016). Molecular epidemiology, phylogeny and evolution of Legionella. Infection, Genetics and Evolution, 43, 108-122.
Correia, A. M., et al. (2016). Probable Person-to-Person Transmission of Legionnaires’ Disease. New England Journal of Medicine, 374(5), 497-498.
Parr, A., et al. (2015). Legionellosis on the Rise: A Review of Guidelines for Prevention in the United Kingdom. Journal of Public Health Management and Practice, 21(5), E17-E28.
Whiley, H., et al. (2014). Legionella detection by culture and qPCR: Comparing apples and oranges. Critical Reviews in Microbiology, 40(3), 304-313.
Abdel-Nour, M., et al. (2013). Biofilms: The Stronghold of Legionella pneumophila. International Journal of Molecular Sciences, 14(11), 21660-21675.
Borella, P., et al. (2005). Legionella infection risk from domestic hot water. Emerging Infectious Diseases, 11(10), 1641-1647.
Steinert, M., et al. (2002). Legionella pneumophila: an aquatic microbe goes astray. FEMS Microbiology Reviews, 26(2), 149-162.
World Health Organization. (2007). Legionella and the prevention of legionellosis. WHO Press.