Overview

What is a chronic bacterial infection?

Chronic bacterial infections are bacterial infections that persist for a long period of time in a host, such as yourself. These infections may involve the bacteria species occupying a particular organ or type of tissue.¹

Pathophysiology of chronic bacterial infections

Mechanisms of chronic infection development

Biofilm formation

Chronic bacterial infections can cause biofilms to form within your body. However, firstly, it is important to understand what is meant by a ‘biofilm’. A biofilm is a community of microorganisms, or more specifically bacteria when discussing chronic bacterial infections. A biofilm is a community of bacteria that stick and adhere to each other and the surface of your body. Biofilms have been found in the following parts of the body:²

• Lungs
• Middle ear
• Mouth
• Stomach
• Colon
• Bone
• Cardiovascular system
• Soft tissue wounds
• Urogenital system

Now you may be asking how biofilms in your body affect you and how your body reacts to the infection.

Firstly, biofilm formation can decrease the effectiveness of antibiotic treatment you may be receiving. This can result in the chronic bacterial infection persisting and not being cured.²

Immune evasion tactics

Additionally, biofilms can help the bacterial cells to evade attack from your immune system. When your immune system initiates its immune response to attack the bacterial infection, the biofilm can protect the bacteria due to the sheer size of the biofilm and the denseness of the biofilm, meaning that your immune cells can not initiate responses such as ‘phagocytosis’. This is where your white blood cells engulf bacterial cells and destroy them.²

Genetic predisposition

Certain individuals can be more genetically susceptible to contracting a chronic bacterial infection. For example, in terms of genetics, there are genetic polymorphisms, which are individual genetic variations of certain DNA sequences between different individuals in the human population. It is believed that these differing DNA sequences can result in certain individuals not fighting chronic bacterial infections as well as other individuals. However, more research is needed to explore genetic susceptibility to chronic bacterial infections.³

Immunosuppression

Additionally, if your immune system has been weakened, and you are immunosuppressed, it may be difficult for you to fight chronic bacterial infections.(NIH)

Common chronic bacterial infections

Tuberculosis

Tuberculosis (TB) is a chronic bacterial infection caused by the bacterial species Mycobacterium tuberculosis. Other mycobacteria species can cause TB too, such as Mycobacterium bovis. TB typically affects your lungs, which can cause you to cough up blood, chest pain and a prolonged cough that can last 3 weeks or longer. TB can affect other parts of your body including your kidneys, brain and your spine. TB is transmitted from one person to another, when the infected person coughs or speaks for example, and releases the mycobacterium spores into the air. These spores are then inhaled by another individual, infecting them.(CDC)

Lyme disease

Lyme disease is a chronic bacterial infection, which is caused by the bacterial species Borrelia burgdorferi. Borrelia burgdorferi is transmitted to humans via a bite from black-legged ticks that have been infected by this bacterium.⁴ Typically, Lyme disease results in the formation of a rash known as erythema migrans. If Lyme disease goes untreated, the infection can spread to your heart, joints and your nervous system. (CDC)

Chronic urinary tract infections 

Before looking at chronic urinary tract infections (UTIs), it is important to know what the urinary tract is first. The urinary tract is your bladder, urethra and your kidneys. When bacteria from either your rectum or skin enter the urethra, this can cause urethritis. The bacteria from your urethra can travel up to your bladder, potentially causing a bladder infection (cystitis) or possibly a kidney infection if the bacteria reaches your kidneys. (CDC, NHS)

The image below shows the anatomy of the urinary tract.

The above image can be found here: https://commons.wikimedia.org/wiki/File:Urinary_System_(Male)_(cropped).png

You may ask: which bacterial species cause UTIs?

Typically, Escherichia coli (E coli) is responsible for causing UTIs, however, other bacterial species can cause UTIs, such as the following:⁵

• Klebsiella pneumoniae (K. pneumonia)
• Proteus mirabilis (P. mirabilis)
• Enterococcus faecalis (E. faecalis)
• Staphylococcus saprophyticus (S. saprophyticus)

It is important to understand that not all UTIs are chronic. A chronic UTI occurs when the infection does not go away, and short-term antibiotics are ineffective in treating the infection. The cause for a chronic UTI may be due to bacterial species entering the lining of your bladder, and this type of infection may have to be treated with long-term antibiotics.(NHS)

Helicobacter pylori infection

Helicobacter pylori is a bacterial species that infects your stomach, and the first part of your small intestine, known as the duodenum. Infection from Helicobacter pylori can result in inflammation of the stomach and duodenum. This infection can cause sores to develop in your upper digestive tract, known as peptic sores, and in more serious cases this bacterial infection can cause stomach cancer. This infection is transmitted from person to person via the mouth. However, it may also be transmitted by being in contact with faeces or vomit that contains the Helicobacter pylori bacterium.(John Hopkins Medicine)

Diagnosis of chronic bacterial infections

Clinical presentation and history-taking

A medical history examination will review any previous illnesses, any allergies you may possess, and your family medical history.⁵ The questions asked during your medical history may differ depending on if a chronic bacterial infection is suspected, or if you have had one in the past and are showing symptoms. For example, if TB is suspected, the medical history exam may focus on any risk factors for TB, and previous history for this disease. Additionally, you may be asked if you have been in contact with anyone who has TB. (CDC)

A physical examination aims to examine your overall health and well-being and involves the following being examined, however, other areas may be examined depending on the symptoms you are presenting:

• Eyes
• Lymph nodes
• Ears
• Nose
• Throat
• Heart
• Lungs
• Abdomen
• Extremities
• Skin

Examining these areas allows a doctor to see which physical symptoms are being presented and aids them in making a diagnosis. (CDC)

Laboratory diagnostics

Microbiological cultures

A sample of bacteria, that is suspected to be responsible for the infection is taken and added to a culture medium. A culture medium contains water and nutrients, as well as added growth factors for the bacteria to grow into a visible culture. The culture is examined by microbiologists so that the bacteria responsible for the infection can be identified.⁷

Molecular techniques

Molecular diagnostic techniques have become favoured over bacterial cultures, as molecular diagnostic techniques can detect if multiple pathogens are present in a patient’s sample. In addition, molecular diagnostic techniques can also analyse the genes of the bacteria causing the infection, to see if the bacteria has any resistant genes to certain antibiotics used to treat the bacteria. This allows for more effective and targeted treatment to be administered.

Imaging

Often imaging scans such as computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound are used to detect inflammation within the body and aid diagnosis. However, these imaging techniques do not distinguish which sites of inflammation are caused by bacteria and which are not.⁹

Management strategies

Antibiotic therapy

Chronic bacterial infections can be treated and managed using antibiotics. However, the type of antibiotic and duration of antibiotic therapy varies depending on the infection, which is discussed below.

Tuberculosis

If you have an active form of TB, which means you are presenting symptoms, you may be given a course of two antibiotics, called isoniazid and rifampicin for 6 months.

Lyme disease

Antibiotic therapy for Lyme disease can vary. Typically it is given as a pill for 10-14 days. However, in some cases, the antibiotic may be delivered as an injection directly into the vein. The common antibiotics used to treat Lyme disease are the following:

• Doxycycline
• Amoxicillin
• Cefuroxime axetil

Chronic UTIs

Chronic UTIs are treated with antibiotics that you take at a low dosage for a prolonged period, approximately 6 months. Examples of some antibiotics you may be prescribed include the following:

• Trimethoprim and sulfamethoxazole
• Fosfomycin
• Nitrofurantoin
• Cephalexin
• Ceftriaxone

Helicobacter pylori

Helicobacter pylori infection can be treated with a course of 2 antibiotics, to be taken twice a day for one week. The antibiotics that are typically prescribed include two of the following:

• Amoxicillin
• Metronidazole
• Clarithromycin

Anti-inflammatory agents

Tuberculosis

Non-steroidal anti-inflammatory drugs (NSAIDs) such as oxyphebutazone have been used to manage active TB by managing the inflammation caused by the infection.¹⁰

Lyme disease

Lyme disease, if left untreated, can result in Lyme arthritis, which can be managed with NSAIDs, such as ibuprofen and aspirin.

Chronic UTIs

Additionally, NSAIDs can be used to reduce the symptoms caused by UTIs.¹¹ However, for chronic UTIs the best treatment is low dose long term antibiotics.

Helicobacter pylori

Unlike the previous common chronic bacterial infections discussed, Helicobacter pylori infection is not treated with NSAIDs, due to them resulting in peptic ulcers and gastritis.¹²

Summary

• Chronic bacterial infections are bacterial infections that persist for a long time within the host
• It can be hard for your immune system to attack chronic bacterial infections as bacteria tend to form a biofilm within your body, forming a matrix of bacteria, which is harder for your immune system to destroy
• Common chronic bacterial infections include chronic urinary tract infections, tuberculosis, Helicobacter pylori infection, and Lyme disease
• Diagnosis of chronic bacterial infections requires a multidisciplinary approach, with a combination of bacterial cultures, molecular techniques and scans
• Treatment and management of chronic bacterial infections involves antibiotics and in some chronic bacterial infections non-steroidal anti-inflammatory medication