Introduction

Definition of streptococcal infections

Streptococcal infections are caused by the bacteria of the streptococcus genus (a kind of group or class that has common characteristics), or any species of streptococcus. These are gram-positive, sphere-shaped bacteria responsible for many disorders such as strep throat, pneumonia; and wound, skin/staph, heart valve and bloodstream infections. These bacteria can spread through different modes including coughing, sneezing, contact with infected wounds/sores or direct contact with infected people.¹

Importance of understanding risk factors

Many bacterial species of streptococci live in and on the human body harmlessly. Some infectious (that can cause infection) species, when present in healthy people without symptoms, make these people carriers of these infections.² The infections caused by them affect various parts of the body such as the throat, sinuses, skin, ear, lungs, bloodstream, and heart valves. The population groups most at risk of being infected with streptococcal diseases include people with existing or underlying medical conditions, children (aged between 0 to 15 years), and the elderly. 

However, people assigned male at birth (AMAB) were reported to be more prone to get infected with it than people assigned female at birth (AFAB). The common environments responsible for infections are schools, nurseries or kindergartens, homeless shelters, hospitals, care homes and military training facilities. Low socio-economic status, skin injuries or diseases, exposure to tobacco, and smoking are additionally identified as risk factors.³ Thus identification of factors responsible for developing severe forms of these infections can aid in early intervention and prevention.

Overview of severe streptococcal infections

Streptococcal infections can be mild, causing strep throat, to severe, causing necrotising fasciitis, streptococcal toxic shock syndrome and bacteraemia.¹ The severe infections are categorised as invasive Group A Streptococcal (iGAS) infections and pneumococcal infections which are discussed here. Invasive infections are caused by pathogens that can invade the body parts, where they are not normally present, including the bloodstream, soft tissues and the meninges.

Types of severe infections

Invasive group a streptococcal (iGAS) infections

Invasive Group A Streptococcal (iGAS) infections are illnesses in which bacteria invade the body parts including blood, lungs, deep muscle (closer to bones or internal body organs), and fat tissues. The majority of the iGAS infections are mild but, in serious cases, severe or sometimes life-threatening infections can occur. The least common but the most severe type of iGAS infections are streptococcal toxic shock syndrome (responsible for low blood pressure/shock with injury to one or multiple organs) and necrotising fasciitis (impacting muscle and fat tissue).⁴

Usually, the invasive infections caused by Streptococcus pyogenes (iGAS), are called Group A Streptococcus. These have the potential for rapid progression, as well as life-threatening complications posing a significant concern for public health. They can affect individuals of all ages with different predisposing factors. It causes multiple virulence factors (molecules required to cause disease) due to bacterial pathogenesis which results in tissue invasion, a weak immune system and systemic dissemination (widespread in the body, tissue or organ).⁵

Pneumococcal infections

Pneumococcal diseases including pneumonia, meningitis, and sepsis are global public health concerns and they lead to significant clinical disease burden. These are caused by a bacteria named streptococcus pneumoniae and often affect young children, the elderly population and the immunocompromised (having a weak immune system) population. 

The most effective strategy to prevent pneumococcal disease is immunisation for public health, and some vaccines have been introduced in this regard. Although pneumococcal vaccines have had a significant role in reducing the impact of pneumococcal disease globally.⁶ Illnesses caused by pneumococcal infections include:⁷

• Pneumonia: Infection of the lungs
• Meningitis: Infection of the membrane that protects the brain and spinal cord
• Sepsis: The immune system reacts improperly to infections
• Bacteraemia: Bloodstream infection, where bacteria are present in the blood
• Otitis media: Infection in the middle ear
• Sinusitis: Inflammation of sinus tissues due to fluid buildup

Streptococcus can cause various types of infections and symptoms depend on the infected body part. Normally, the associated symptoms are similar to other bacterial infections affecting that part of the body. Symptoms of serious infections result in adverse health problems or death. Such complications in streptococcus infection do not occur in mild infections. However, many factors impact the development of streptococcal infections.

Risk factors for developing severe streptococcal infections

Study reports and population-based investigations have identified various probable risk factors  (age, ethnicity, alcoholism, drug use, diabetes mellitus, cardiovascular disease, HIV infection and other chronic diseases) as responsible for causing severe streptococcal infections including iGAS.⁸ It is also suggested that in adults, environmental factors and close contact with the person infected with this disease are related to the risk of community-acquired iGAS illness.

The associated environmental factors responsible for increased risk in children include household size and the proximity of a child with a patient having a sore throat or other symptoms. Thus, environmental factors reflect the significance of person-to-person contact responsible for the transmission of streptococcus bacteria.

Age

Very young children

In the 1950s, household-based studies illustrate that children (school-aged) often introduce iGAS strain or streptococcus into a household. In such cases, mothers are more prone to get infected by the bacteria than fathers. The studies also proposed that transmission of bacteria in households depends upon children’s exposure and duration of exposure to an infected person. 

Streptococcal infections including throat infection, scarlet fever and impetigo (skin infection) often occur in school-aged children. Immature immune systems can be responsible for making them more susceptible to severe infections. However, in the last few years rise in iGAS infections worldwide in children is becoming complex to diagnose and treat the infection promptly.³

Elderly

The iGAS infection can affect people of all ages. People who come in contact with an infected person remain at increased risk. The iGAS does not occur frequently but some people are more likely to get infected such as the elderly and young infants, people who consume drugs (injection) and those who had household contact with someone infected with iGAS during the past month. Elderly populations are more susceptible to the infection due to higher frequency of underlying health conditions and declining (weakened) immunity.⁴

Chronic medical conditions

A surveillance study conducted for 10 years on the population of the San Francisco Bay area revealed the relationship between iGAS infection and cardiac disease. However, the associated reasons behind the increase in the risk of iGAS disease and cardiac disease are unknown. Chronic diseases like diabetes, respiratory conditions, heart problems and liver or kidney disease contribute to a high risk of severe streptococcus disease.

A person with diabetes mellitus can have severe infections due to weak immune response and poor blood circulation.  A person with compromised cardiovascular (heart) health is also vulnerable to infections. Liver and kidney-diseased patients result in a higher risk of severe infections due to reduced ability to get rid of infections. Respiratory conditions including chronic obstructive pulmonary disease (COPD) and asthma, increase the chances of severe pneumococcal infections.

Immunosuppression

The association of severe streptococcal infections like iGAS with HIV has been identified. It suggested that immunosuppression caused by HIV contributes to a rise in the risk for iGAS disease. A study of 18–44 years old adults has shown that HIV infection and history of drug use through injection were related to invasive GAS illness. The relation of increased risk of streptococcal infection with injecting drug use is different from that of association with HIV infection.⁸

In the elderly population, heart problems, diabetes mellitus, cancer and the use of corticosteroids are associated with iGAS infection. This type of association in older adults with diabetes, cancer, and corticosteroids reveals the weakened immune system contributes to the development of this disease. Immunosuppressive medications (immunosuppressants), and immunosuppressive treatments or conditions including cancer and chemotherapy reduce the ability of the body to fight off infections.

Skin injuries or wounds

A significant portion of patients affected with iGAS disease had a cutaneous form of the disease (impacting the skin). A large proportion of those who have the cutaneous disease appear with an open sore, bruise, or burn before the beginning of iGAS symptoms. Here we see skin is an important point for the introduction of iGAS illness or severe streptococcal infection. Open wounds and trauma may serve as an entry point for bacteria and aid in increasing the risk of severe skin and soft tissue infections. Surgical incisions or post-surgical wounds also act as potential sites for invasive infection. Chronic skin conditions like eczema and dermatitis compromise the skin barrier and allow bacterial infections to enter through the skin.

Viral infections

Varicella infection (chickenpox) is an established risk factor responsible for the development of iGAS disease in children. Influenza is a viral infection that weakens the immune system and creates an environment for secondary bacterial infections. Chickenpox, particularly in children, can lead to skin lesions which may get infected with streptococcus. Viral infections such as paralysis, cirrhosis, and chickenpox can be risk factors for severe streptococcal infections including iGAS disease. However, further research is needed to establish a significant association between iGAS disease and paralysis.

Lifestyle factors

Studies have revealed a relationship between streptococcal infection, including pneumococcal disease, with cigarette smoking. Smoking not only damages respiratory tissues but also makes infections more severe. In addition to this, alcohol impairs immune function and increases the risk of invasive infections. Alcohol abuse and drug users (especially those who use injection) are also at risk of iGAS infections.

Poor nutrition or lack of nutrition weakens the immune system, and increases susceptibility to severe streptococcal infections. Healthcare settings like hospitals are at higher risk and long-term care facilities due to exposure to infected individuals are also vulnerable to such infections. However, observation of these risk factors is helpful when the preventive steps discussed below are adopted early in the disease. 

Preventive measures

Streptococcus infection can affect a person more than once. In the case of iGAS infection, vaccines are not available to prevent the infections. The prevention of iGAS is variable, but it generally focuses on three important things which are limiting exposure, limiting the spread of bacteria, and treatment of infections, along with the use of preventive antibiotics when needed. However, there are measures mentioned below that people can use to prevent it.^2,3

Good hygiene practices

The spread of streptococcal infections can be reduced by good hand washing, particularly after coughing and sneezing, while preparing meals, and before eating. Patients with sore throats should consult a physician who can diagnose the infection by performing tests. A patient with such an infection should stay home for 24 hours or more from work, school, or daycare after consuming an antibiotic. Wounds should be kept clean and watched if they have possible signs of infection such as increasing redness with pain or swelling at the wound area.

Antibiotics

Antibiotics are used to treat bacterial infections and prevent the spread of bacteria to other areas. They are helpful to prevent serious illnesses, such as rheumatic fever. Preventive antibiotics may be taken orally or as a shot into the muscle at intervals of around a few weeks as prescribed by the doctor.⁴

Serious/severe infections

In the case of serious/severe infection, antibiotics may be given to close contacts by healthcare providers if the patient is 65 years or older and has other factors or underlying illnesses that increase the risk of a serious infection.

Vaccination

Pneumococcal vaccines are recommended for children, the elderly, and those with underlying health conditions. The influenza vaccine reduces the risk of secondary bacterial infections following the flu.

Avoid close contact

People should minimise their exposure to infected individuals with active streptococcal infections. One should avoid crowded places or environments during outbreaks.

Management of chronic medical conditions

Chronic conditions can be controlled by implementing regular medical care tips. It also helps to reduce the risk of severe infections.

Infections can not always be prevented, but appropriate treatment methods aid control and management of the disease in the early stages. Lifestyle changes like handwashing, sanitising etc. are helpful in controlling its spread. Certain population groups, including children, older adults, and people with weak immune systems are prone to develop severe streptococcal infections. Further research is required to develop better treatment options for their safety.

Summary

Streptococcal infections are caused by streptococcus bacteria and usually lead to mild illness. In rare cases, the infection may become severe and can be life-threatening. Severe streptococcal infections pose a risk to people with existing or underlying medical conditions, children, and the elderly (60 years and above). The environments most responsible for facilitating the spread of infections include schools, nurseries or kindergartens, care homes, homeless shelters, hospitals, and military training facilities.

Consequently, risk factors responsible for streptococcal infections need to be identified to prevent it from further spreading. Chronic or underlying medical conditions, hygiene and lifestyle practices, age, taking immunosuppressants, and having skin and viral infections are the factors impacting severe streptococcal infections. Antibiotics as medications and vaccination for secondary viral infections, are the common clinical treatment methods. Good hygiene practices are complementary measures to prevent it.