Opportunistic Infections in the Immunocompromised Host and Infection Control Challenges

By Dr. Hafiz Ahmad (PhD – AIIMS, PDF- NIH, U.S.), Assistant Professor & Clinical Microbiologist,Department of Medical Microbiology and Immunology, RAK College of Medical Sciences, RAKMedical & Health Sciences University; and Adjunct Clinical Microbiologist, RAK Hospital

The risk of transmission of pathogens and subsequent infection in healthcare facilities is substantial. Pathogens may be transmitted from other patients (cross infection), the hospital personnel, and/or the hospital environment leading to Health Acquired Infections (HAIs). The risk is variable and depends on a patient’s immune status, the local prevalence of various pathogens, and the infection control practices and antimicrobial stewardship utilised during hospitalisation. Apart from the well-established pathogens (bacteria/fungi/viruses) causing Ventilator Associated Pneumonia (VAP), Catheter related Blood stream Infections (CRBSI), Urinary Tract Infections and drug resistant Methicillin Resistant Staphylococcus aureus (MRSA), there exist some less established opportunistic pathogens.  

Opportunistic Infections

Opportunistic infections (OI) are caused by pathogens of low virulence, which are usually non-pathogenic in a healthy individual. These are bacterial/viral/fungal/parasitic infections contained by immunocompetent hosts which cause progressive disease in immunocompromised patients (Human Immunodeficiency Virus (HIV)/Acquired Immunodeficiency Syndrome (AIDS)) and are often characterised by latency and reactivation. 

The Immunocompromised Host 

An immunocompromised host is a person who does not have the ability to respond normally to an infection due to an impaired, weakened or defective immune system, predisposing him to infections, often life-threatening, which would not otherwise occur. This inability to fight infection can be caused by a number of disease conditions: HIV/AIDS, malnutrition, cancer therapy with Immunosuppressive drugs etc. 

Epidemiology 

According to World Health Organization (WHO), major OIs include: Acquired Immunodeficiency Syndrome (AIDS) caused by HIV, Tuberculosis (TB), Pneumocystis jiroveci pneumonia (PCP), herpes infections, Cytomegalovirus (CMV), candidiasis, cryptococcal meningitis and cerebral toxoplasmosis in different chronology depending on multiple factors. 

Immunocompromised patients are at high risk for opportunistic infections. Traditionally, there are infections that arise from endogenous reactivation of latent infections, and nosocomial transmission. Therefore, it is deemed likely that special infection control (IC) interventions are required to prevent transmission in healthcare settings. 

Reinfection with pathogenic organisms in new cases of immunocompromised population can occur possibly by means of airborne transmission and nosocomial spread especially with respect to tuberculosis. Most studies support the view that infectious complications in immunocompromised patients are exogenous in origin and more epidemiological studies are needed to define the risk of nosocomial spread and need for better infection control practices to prevent these infections. 

The fact that infectious complications in immunocompromised patients are often predictable and can be prevented, makes infection control practices a very important step in the improvement of the quality of care provided to the immunocompromised patients. In addition, by reducing infectious morbidity, infection control practices will contribute significantly to cost savings. 

Tuberculosis – (Pulmonary TB) 

TB is caused by Mycobacterium tuberculosis and is an airborne disease, transmitted from person to person through aerosols route. It is a highly communicable disease that can be spread while talking, sneezing, coughing and shaking hands. The UAE being a cosmopolitan country with a dynamic influx of people from more than 200 nationalities poses a major challenge to the control of tuberculosis. As per 2018 census, of the total 9.54 million UAE population, majority, 8.4 million (88.5 per cent) is constituted by a floating population of expatriates. Immigrants from India, Sri Lanka, Pakistan and Bangladesh are major contributors to this OI. Thankfully, the incidence has been reduced due to stringent visa control measures implemented by the Ministry of Health and Prevention in the UAE.

Although the prevalence of TB in UAE is fairly low, the rising incidence among expatriates poses a major challenge. An increasing number of cultures have confirmed TB and multi-drug-resistance tuberculosis (MDR-TB) among native and expatriate patients, necessitating improved vigilance in case detection, effective management and prevention of MDR and XDR-TB emergence in the country. 

HIV and TB Co-infection - A Major Infection Control Challenge 

HIV/TB co-infection is another major challenge especially in MDR-TB cases. Although HIV incidence is very low in UAE and restricted to expatriates and in transits from high prevalence African countries, treatment cost and medical management poses a challenge for the hospital in terms of infection control, patient isolation, clinical management and care. 

The incidence of other OIs like CMV, PCP and Herpes, fungal and parasitic infections are very low in the UAE and only rare cases have been reported. 

Transplant and Immunosuppressive Therapy

There is a growing number of immunocompromised patients because of the use of intensive therapeutic regimens in patients with cancer and organ transplantation, besides those with HIV infection. 

Post-surgery, an organ transplant patient is at his most vulnerable state. The immunosuppressive medications enable them to avoid rejection of the new organ, but at the price of a defenseless immune system. ICU patients, neonates, HIV-positive patients and the elderly - each of these groups are at a higher risk of infection than the average hospital occupant. It is the infection control staff’s duty to assess the risk factors, minimise as many as possible and annihilate infectious organisms that take advantage of the situation. 

Improvements in patient survival have been observed in all categories, but the risks of infection related to immunodeficiency continue to be substantial by either resident or environmental bacterial, fungal, viral, and protozoal parasites. Even low-virulence microbes (opportunistic pathogens) may invade, proliferate, and cause disease in the immunodeficient host. Furthermore, newer organisms previously considered as contaminants or harmless colonisers have now emerged as significant human pathogens in the immunocompromised host.

Handwashing, Self-hygiene and Standard Precautions

Hands are the most common vehicle for transmission of organisms. It is estimated that 30-40 per cent of hospital acquired infections are related to contamination of healthcare workers hands. Proper “hand hygiene” along with standard universal precautions likes gloves, gown, mask, shoe and head cover are the single most effective means of preventing the horizontal transmission of infections among hospital patients and health care personnel. Limiting visitation by patient attendants, routine floor cleaning with disinfectants, cleanliness of the hospital staff and nurses is paramount in infection control.

Adenosine triphosphate (ATP) level and fluorescent markers have been used as surrogates of contamination to assist monitoring of cleaning especially in ICU’s for monitoring protective microbial contamination and reducing chances of OIs in immunocompromised patients, but their role in determining surface microbial contamination is controversial. On the other hand, infections like TB are airborne infections and can be only controlled using tight fitting doors and negative pressure isolation ventilations. Protection using N-95 respirator mask should be practiced before entering isolation room. 

There is an elemental role of the microbiology laboratory and Infection Control officer in the prevention and control of infections and for providing awareness and training. Direct observation and feedback of cleaning services including an education component ideally can result in change in behaviour and goes a long way in implementation of good infection control practices. 

Prevention of infection, prompt diagnosis and treatment remain the cornerstones of management of OIs. The importance of basic infection control measures cannot be over-emphasised. In addition, appropriate prophylactic agents, rapid diagnostic techniques and the early institution of appropriate therapy are essential for good infection control practices.