Epidemiological Survey of Candida Species Isolated from Immunocompromised Hosts at the University of Nigeria Teaching Hospital, Enugu State

Introduction

Candida species are excessively abundant in nature as free living organisms with a peculiar arrangement of nuclear materials, presence or absence of mitochondria and endoplasmic reticulum. Candida is a genus of yeast and a common cause of fungal infections worldwide [1]. Candida species are earlier confined to the human and animal reservoirs but they are now frequently recovered from the hospital environs such as from operating couches (Tables), patients’ beds, wall surfaces of wards, theatres (a square area marked out on the four corners of the walls), door handles of theatres, ICUs, pocket areas of the theatre gowns, Nurses’ uniforms and ward coats (2cm from the mouth/lid of the pocket upwards), ultra sound scan (USS) probes, laboratory benches, air samples, foods, table tops, air-conditioners, floors, walls, respirators and other medical devices and personnel [2]. These species are notorious for their resistance to the common azoles which are used in the treatment of candidiasis. This makes it pertinent to carry out a research into the isolation of Candida from the environment and humans, especially the immunocompromised patients [3].

The infection caused by Candida species is called candidiasis, though some species are harmless commensals of humans hosts [4]. However, when mucosal linings are disrupted or the immune system compromised, they can invade and cause diseases [5]. The steady increase in the problems of mucosal and systemic candidiasis reflect the enormous rise in the number of patients at risk and the increased opportunity that exists for Candida species to invade tissues that are normally resistant to invasion. Candida species are true opportunistic pathogens that exploit some normal physiological phenomena and recent technological advances to gain access to the circulation and deep tissues [6].

The incidence of Candida infections have increased substantially in recent times. Therefore, early detection of candidiasis and the correct identification of the Candida species are pre-requisites for the appropriate therapeutic intervention [7]. Candida pathogenicity is facilitated by a number of virulence factors, the most important of which are those for adherence to host tissues and medical devices, biofilm formation and secretion of hydrolytic enzymes called, proteases, phospholipases and haemolysins [8, 9].

The primary factor in the fungal colonization of human tissues is adherence to host surface; this process is controlled and induced by several cell-mediated activities induced by the fungus and environment [10]. Biofilms cause clinical problems because they increase resistance to antifungal therapy. Extracellular hydrolytic enzymes play an important role in adherence, tissue penetration, invasion and the destruction of host tissues [11]. Unfortunately, diagnosis of invasive candidiasis is still problematic because clinical symptoms are non-specific and conventional assays are not satisfactorily precise and may take several days to obtain results. Blood cultures which are assumed to be the most reliable marker of invasive candidiasis are commonly negative, whereas positive cultures form other sites may represent colonization [12]. Also, blood culture requires 2-5 days for correct identification.

The most often identified species has always been Candida albicans. However, the incidence of non-albicans Candida species has been increasing with the changing spectrum of patients and these species have also been associated with higher mortality. C. parapsilosis persists in hospital environments, thereby enhancing the chances of acquiring nosocomial infections. It colonizes the skin of patients and it is able to form biofilms on plastics resulting in candidaemia in patients with in-dwelling venous catheters [13].

Epidemiological investigations of outbreaks in hospitals are required to identify the source of infection, route of transmission and how to eradicate it. Such investigations require accurate strain typing because in candidaemia it is problematic to distinguish between endogenous and exogenous sources of infection from another infected patient(s), or even healthcare workers, as the case may be [14]. In healthy and immunocompetent individuals, Candida does not usually give rise to diseases as its growth is suppressed by other micro biota and the host defense mechanisms. However, in a situation where there is alteration in the mucosal barriers or the immune system is compromised, they can invade and cause disease [15].

Candida species are considered important pathogens due to their versatility and ability to survive in various anatomical sites [16]. In the early 1980s, fungi emerged as major causes of nosocomial infections, mainly affecting immunocompromised patients or those who were hospitalized for long periods due to serious underlying diseases. Prolonged ICU stay and hospitalization are also important. Akpan, et al. [17] evaluated the impact of invasive fungal infection in surgical patients with severe Candidal infections are a major problem, especially among the immunosuppressed people. Oral infections with yeasts are more frequent in diabetic patients, but some results remain controversial and contradictory. A great number of reports suggest that Candida albicans is the commonest species that inhabit the oral mucosa of diabetic patients and the highest rate of colonization occurs in diabetic patients with poor glycaemic control [16]. Oral candidal infection has been associated with cigarette smoking and use of dentures in adults with diabetes mellitus and reduction in salivary flow in these patients increases the incidence of oral candidiasis. The epidemiology of oral Candidal infection in diabetic patients seems to be complex, resulting from a combination of many predisposition factors [17].

Due to high production of progesterone during pregnancy, the normal functioning of neutrophils is impaired which in turn increases Candida colonization and infection. In addition, high production of oestrogen during pregnancy has its own impact on immunoglobulin secretion in the vagina which results in mucosal surface defense failure [5]. Generally, the main reason for increased vaginal candidiasis in pregnant women is due to elevation of reproductive hormones during pregnancy. High levels of reproductive hormones during pregnancy provide an increased amount of glycogen in the vagina which enhances growth of Candida species because glycogen serves as a carbon source for Candida growth. In addition, oestrogen enhances adherence of yeast to the vagina by reducing immunoglobulin secretion and fungal inhibition activity of the epithelial cells [18]. The clinical manifestation of the disease is characterized by vaginal pruritis, thick curd/cheese-like vaginal discharge, itching, redness, burning, swelling and pain during walking and urination [19]. These clinical signs and symptoms, though not specific, are important for the diagnosis of vaginal candidiasis. Pregnant women with such clinical manifestations should be treated as early as possible because candidiasis is reported as a risk factor for pre-term birth. In complicated candidiasis, non-albicans Candida species are common and the disease is commonly seen in diabetic, debilitated or immunocompromised women. The outcome of complicated vaginal candidiasis is psychosexual problems (e.g. feeling unclean or not wanting to have sex) and depression [20].

A neonate is a baby who is 4 weeks old or younger. A neonate is also called a new born. The neonatal period is the first 4 weeks of a child’s life. It is a time when changes are very rapid. Systemic fungal infections, previously considered to be a rare complication, occur in as many as 5% low birth weight babies. They are even more frequently diagnosed in very low-birth weight babies (VLBW) receiving intensive care. About 20% of babies weighing less than 1000g develop invasive fungal infections. The overall mortality rate for disseminated fungal infections in this group of babies is very high, often approaching 50% [21].

Evidences abound to show that Candida species can be acquired from both clinical and environmental sources. The understanding of the epidemiology of candidiasis has grown appreciably over the past years. Rapid changes in the rates of infection, potential risk factors and emerging new species in the aetiologic frequencies demand continued and close surveillance in our hospitals and environs. Recent studies, performed years ago have broadened the epidemiologic understanding of nosocomial candidiasis from a single endogenous infection to one that may be exogenously acquired through the hands of health care givers, biomaterials and inanimate environment including the walls of theatres, wards and the wears of health care givers. While these information are documented and very well at hand in developed countries, the knowledge in developing countries including Nigeria is either conflicting, biased, inadequate or completely inexistent. It is therefore pertinent that studies are undertaken to define more accurately the emergence of new species, specificity of old ones, reservoirs, mode of transmission, relationship with immunocompromised patients, the best method of identifying these Candida species and their exact extent of involvement in nosocomial infection in this country and South East Nigeria, in particular.

Therefore, there is need to carry out this research to unravel the extent of damage these Candida species have caused in our environment due to misdiagnosis and the unavoidable contact of the organism (Candida) with the patients or the healthcare giver or even medical devices that in turn transmit these organisms to the patients in form of re-infection in the course of healthcare delivery. Therefore, this study is aimed at determining the prevalence and distribution pattern of Candida species from clinical and environmental sources of each of the Healthcare facilities and to assess the risk factors involved.

Results

315 clinical specimens (sputum, urine, HVS and stool samples) from 4 immunocompromised conditions (HIV/ AIDS, Diabetes mellitus, Pregnancy and Neonates) and 150 swab samples from the hospital environments which included the theatres, wards, ICUs, Laboratories, air samples and other health care delivery materials from the hospital in the South Eastern Nigeria were screened for the presence of Candida species. This is to ascertain to what extent the patient environment helps in the infection and re-infection of the patients especially the immunocompromised.

Discussion

Scholars have over time studied and opined that the infective process initiated by Candida species has been upgraded by a number of notable virulence factors that confers on them certain immuno-invasive potentials in order to thrive in their host(s) and perpetrate health challenges. Such factors include adhesins for attachment to the host’s tissues and medical equipment, the formation and settling of biofilms on medical devices found within the patient’s environment and the ability to secrete hydrolytic enzymes that attack and break down the host’s defense mechanisms in a bid to initiate an infection. This concern underscores the aim of this study; trying to isolate and identify Candidal isolates from both the immunocompromised patients and their intimate environment. However, the pressing need to rightly identify the isolates has not been without limitations that common with the conventional methods of identification, thereby compounding the problems of misdiagnosis and the unchecked re-infection.

Table 1 shows the results obtained from culturing the specimens collected from the immunocompromised patients in University of Nigeria Teaching Hospital (UNTH), Enugu South Eastern Nigeria. Out of the 315 specimens collected from these human sources, 158(50.2%) yielded fungal growth, while 157(49.8%) yielded no obvious growth of any Candida species. The identification of the aforementioned isolates was from conventional methods which corroborates with the work of Pfaller, et al. [13] where he recorded that immunosuppression is a favorable condition for fungal colonization in immunocompromised patients. Additionally, the study confirms that immunosuppression supports the isolation of fungal species from most of the specimens as seen in UNTH Enugu, where 66 (51.9%) out of the 127 HIV patients used for the study, yielded Candida isolates. Pappas, et al. [16] said something to support this notion. He was of the opinion that Candida species are opportunistic, hence maximize every and any opportunity to gain access into deep tissues when the immune responses are jeopardized.

In Table 2, the Candida species were isolated using conventional methods from the environmental sources; the medical devices and other environmental surfaces around the patient within the healthcare facility. Out of the 150 samples collected from the wards, theatres, ICUs, wears, laboratories and other medical devices at UNTH Enugu, 34 samples yielded Candida species which represents (22.7%) of the samples size used for this study. From this study, it was recorded that a good percentage of the environmental samples yielded Candida species, except the air samples obtained from the ICU. That means, the air current in these wards where these patients are attended to can become a potential source of infection and can induce the re-infective processes commonly seen among immunocompromised patients. These findings so much agrees with the work of Pfaller, et al. [13]: he reported that additional infections do arise by reasons of exogenous contamination through the healthcare workers, medical devices, biomedical instruments and the very immediate surroundings of these immunocompromised patients. He continued by saying that this can bring about hospital-acquired infections, especially among patients’ with any of the debilities considered in this study.

However, the methodology adopted in this study slightly veered off course from the normal in identifying the species of Candida species isolated using Chrom Agar. Owing to the fact that way before now, most of the authors who worked on related studies identified C. albicans as the common culprit associated with candidiasis. This study identified C. tropicalis as the most offending Candida species followed by C. albicans and C. metapsilosis from the studied samples.

Nevertheless, this study focused on the infective significance of the Candida species found within the immediate surroundings of these immune-debilitated patients which can possibly cause infection or initiate re- infections due to continuous contact with the patient’s external environment via the healthcare givers or from medical devices. Either ways, thoughts about the infective significance of viable biofilms that can initiate an infective process in an immunocompromised patient was considered than the high percentage of isolates that exist as fomites or as aerosols that cannot cause any infections even in the immunocompromised patients understudied herein.

Evidences abound putting forth that the non-albicans candidiasis has gotten enough points as aetiologic agents of infections and re-infection. Also, a better understanding of potential reservoirs of these Candida species and their modes of transmission to the immunocompromised patients had been established before now. These findings are essential as they will help in developing effective preventive and therapeutic strategies against invasive candidiasis from the C. albicans and non-albicans Candida (NAC) pathogens.

In all, 5 different fungal organisms were isolated from both clinical specimens with different percentage occurrence. From analysis, Candida metapsilosis occurred 1(12.5%), C. albicans 1(12.5%), C. parapsilosis 2(25%), C. orthopsilosis 2(25%), and C. tropicalis 2(25%). From Table 3 above, it is observed that Candida tropicalis has the highest frequency in both clinical specimens. Since these samples are from the immediate environment of the patient, cross infection may be possible in the patients who have compromised immunity hence, the preponderance of nosocomial infection due to Candida species among hospitalized patients.

The findings of this study is corroborated by the 2015 study of Colombo, et al. [20] which stated that C. tropicalis is one of the most common colonizers of the human skin, female genitourinary tract and can be transmitted between healthcare workers and patients especially in environments such as hospitals [19]. It is the second most virulent Candida species and can significantly affect by spreading through the weakened immune system host.