PCP Outbreak and News Report (a dramatization)

by Matt Jorgensen

This last weekend an outbreak of Pneumocystis pneumonia was reported at St. Matthew’s Hospital in St. John’s, Minnesota. The disease has been found in the intensive care unit (ICU) and oncology floors of the hospital. The first case was documented around late Saturday night, with seven more cases popping up in the same department early Sunday morning. As of right now, there have not been any reported deaths caused by this outbreak, and all of us here at the station are hoping that continues. Based off studies on the disease, I advise all of you at home not to panic, however, you should understand the seriousness of this disease in a hospital setting. In order to lessen your worries and give you a better understanding of what is occurring, I am giving you all the information you will need to know about Pneumocystis pneumonia and help explain how the outbreak occurred.

To begin, I would like to make you familiar with the causative agent of Pneumocystis pneumonia (or PJP), Pneumocystis jiroveci, and why it’s important. P. jiroveci, although once thought to be a protozoan until 1988, was found to be a fungus that resides in the environment (1). Infection of P. jiroveci leads to PJP due to the colonization, or accumulation, of the fungus in the lower respiratory tract of the host (1). This is a very serious process and can lead to death. In fact, PJP is one of the leading causes of both morbidity and mortality in HIV patients, and is also the most common opportunistic infection in AIDs patients in the US (1, 2). The fungus is an opportunistic pathogen for humans, especially those who are diagnosed with HIV/AIDS (1). To be clear, an opportunistic pathogen is only able to infect human hosts who are immunocompromised, or when their immune system is weakened. Due to this, I suggest you not to worry at home and I will address this idea later in this article.

This may leave you asking “How does a deadly fungus like P. jiroveci get into a sanitized hospital?” It’s a fair question. You may not have known it at the time, but as children a majority of you were exposed to P. jiroveci while simply spending time outdoors, whether it be hiking, swimming, or playing sports. Also, P. jiroveci is commonly found in the environment, specifically in soil and water, and has the ability to infect human hosts/relocate itself through airborne fungal spores (2, 3). Therefore, the likely reasoning behind P. jiroveci accessing the patients in St. Matthew’s Hospital is through infection of an immunocompromised host through inhalation of airborne spores (which explains the outbreaks occurring in the ICU and oncology floors for those patients are all immunocompromised). The terrifying thing about P. jiroveci human to human transmission is it can infect another immunocompromised host up to 8 meters in distance away in hospitals (3). This leads to serious outbreaks in hospitals, like the one seen last weekend.

The severity of PJP is associated with the symptoms seen in infected human hosts, which everyone should be aware of and look for if need be. These symptoms can be mistaken for an average cold, and include weight loss, coughing, fever, dyspnea (or difficulty breathing), night sweats, and wheezing (4, 5). In terms of what happens inside the infected individual, the P. jiroveci goes through a cycle of trophozoites, precysts, and cysts stages (4). These cysts adhere to the epithelium, or outer layer, of the lung of the host, and can be seen by CT scans colonizing the lung (5). For those who are interested, I have attached CT scans from Kanne et al. depicting cyst formation along with ground-glass opacity below. These hazy, ground-glass opacities are nonspecific formations that show infection of the lung (6). (Left= cyst colonization, Right = ground-glass opacity) Theses cysts, especially when in high densities, lead to a triggered immune response by those who are infected, thus causing inflammation, irritation, and damage to the lungs. This is why the main symptoms associated with P. jiroveci infection are coughing and dyspnea, and therefore are what should be looked for when diagnosing infection.

There is good news, however, for there are medicines that can be used to fight PJP. Antimicrobials, like tri-methoprim-sulfamethoxazole (TMP-SMX), are the main treatment of choice when fighting a PJP infection (2). Also, corticosteroids, like glucocorticoids, have been shown to be effective in decreasing the inflammatory response of the host, and therefore lessening the likelihood of mortality (2). Luckily, the staff at St. Matthew’s recently received a shipment of both drug types, and therefore have been promptly administering the needed dosages.

CT scan showing P. jiroveci cyst colonization (white arrows) of infected patient.

http://www.ajronline.org/doi/full/10.2214/AJR.11.7329    

CT scan showing ground-glass opacity (black arrows) in lung of infected patient.

http://www.ajronline.org/doi/full/10.2214/AJR.11.7329

Many concerned family members and friends have called in asking about the status of their loved ones. I want to reiterate that the P. jiroveci fungus is an opportunistic pathogen, and therefore you should not be concerned if your loved one does not have a weakened immune response. To be more precise, previous studies have shown that the immunocompromised, especially those with HIV, have a much higher risk of PJP (7). The study showed that for patients with HIV, 100% of them were male and in their late 30s, while patients that were immunocompromised without HIV were equally male and female and in their 50s (7). This information is shown in Table 1. from the article Li et al, which I attached below.

These experimental characteristics are similar to the observed characteristics reported by the head administrator of clinical practice at St. Matthew’s, John Adams, of those impacted in the current outbreak. Of those with HIV in the ICU, almost 100% of them are male, and those who are immunocompromised on the oncology floor. The names of the patients impacted are private information, but family members have been contacted by St. Matthew’s officials.

Now that you are experts in P. jiroveci and PJP, I hope that you understand that although it is a very serious outbreak, there is no need to panic. Remember that P. jiroveci is an opportunistic pathogen, and therefore can only infect those who are already immunocompromised. Also, remember that all of us have already encountered P. jiroveci as children, and that the fungus is most likely all around us while we are outside in the environment. Now, that does not mean as readers you must ignore P. jiroveci, and its seriousness. There are more ways to be immunocompromised other than having HIV or receiving chemotherapy, like in the unfortunate case at St. Matthew’s, that lead to a weakened immune response and susceptibility to P. jiroveci infection. I have attached another table from Morris et al. that outlines certain risk factors that may lead to P. jiroveci infection due to a weakened immune response below. (PCP = the former name of PJP; COPD = Chronic Obstructive Pulmonary Disease)

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3346301/ 

I ask you to please take the time to look over these risk factors, to think about those being affected at St. Matthew’s currently, and to hold onto what you have learned today about the very serious and important fungus P. jiroveci. As a community, having knowledge about P. jiroveci may potentially save many lives. However, there is no current need to panic, for you are most likely not in any situation or state to be infected by P. jiroveci.

There will be updates concerning the outbreak throughout the week, here at Eukaryotic Microbiology News. I want to thank you as readers for taking the time to learn more about the significant microbe P. jiroveci, and I hope you won’t forget it.

Article References:

1.     Vanspauwen et al. Molecular epidemiology of Pneumocystis jiroveci in human immunodeficiency virus-positive and –negative immunocompromised patients in The Netherlands. Journal of Medical Microbiology. Pgs. 1294-1302, 2014.

2.     Morris et al. Colonization by Pneumocystis jiroveci and Its Role in Disease. Clinical Microbiology Reviews. Pgs. 297-317, 2012.

3.     Coyle et al. Rising incidence of Pneumocystis jiroveci pneumonia suggests iatrogenic exposure of immune-compromised patients may be becoming a significant problem. Journal of Medical Microbiology. Pgs. 1009-1015, 2012.

4.     Kaur et al. Pneumocystis pneumonia in HIV patients: a diagnostic challenge till date. Medical Mycology. Pgs. 587-592, 2015.

5.     Kanne et al. Pneumocystis jiroveci Pneumonia: High-Resolution CT Findings in Patients With and Without HIV Infection. Cardiopulmonary Imaging. 2011.

6.     Knipe et al. Ground-glass opacification. Radiopaedia.org, online website. Accessed 2 December, 2016. Pgs 1-2.

7.     Li et al. Pneumocystis jiroveci pneumonia in immunocompromised patients: Delayed diagnosis and poor outcomes in non-HIV-infected individuals. Journal of Microbiology, Immunology, and Infection. Pgs. 42-47, 2014.