Candida are thin-walled, small yeasts of up to four to six microns that reproduce by budding. According to Kwon-Chung and Bennett (1992), even though there are more than 150 species of Candida, no more than 10 species cause disease in humans with any frequency. Of these, Candida albicans causes almost 100% of cases of oropharyngeal candidiasis and at least 90% of cases of Thrush. Other species of Candida, apart from Candida albicans are seen with increased frequency in patients with Systemic Candidiasis.


EPIDEMIOLOGY AND ECOLOGY
Candida can be found in soil, inanimate objects, food and hospital environments. In addition, Candida species such as Candida albicans are normal commensals of man and can be isolated from many sources in normal and ill individuals. However, Candida can also produce a wide variety of infections, and distinguishing between colonization and infection can sometimes be a challenge. Even though diseases related to Candida have been known for centuries, the importance of these conditions has assumed increased relevance during the last two decades.

The epidemiology of infectious diseases has changed significantly with the advent of new chemotherapeutic agents, new immunosuppressive agents, organ transplantation, parenteral alimentation, broad-spectrum antibiotics and advanced surgical techniques. As such, fungal infections have emerged as a critical issue in a compromised host and Candida have become the most common fungal pathogens.

In the USA, Candida species infections accounted for about 78% of nosocomial fungal infections reported to the National Nosocomial Infection Surveillance System (“NNIS”) at the Centre for Disease Control, Atlanta, Georgia, USA. In addition, the ability of Candida to produce oropharyngeal candidiasis in patients with AIDS has made candidiasis the leading fungal infection in this immunosuppressed population.


FORMS OF CANDIDIASIS5
The various forms of candidiasis are the most frequent causes of fungal infection in humans. Candida can produce infections in both otherwise healthy individuals and in individuals with reduced immune system function. Candidiasis can be classified into:-

1.
Invasive Candidiasis (also known as Systemic Candidiasis)

"Invasive" implies invasion past the skin and the gastrointestinal tract. Also called Systemic Candidiasis, invasive candidiasis is a complicated collection of diseases. These forms of candidiasis are only seen in individuals with reduced function of the immune system or some other type of weakening of their defences, and almost any organ of the body may be involved. However, there are many natural barriers to this form of disease, and it only occurs in individuals who have reduced or altered host defences.
There are four forms of Systemic Candidiasis as described in Figure 6 below, the most basic of which is candidemia. It is generally thought that all other forms of Systemic Candidiasis follow an episode of candidemia. However, the episode of candidemia is not always detected. This makes the clinical diagnosis of Systemic Candidiasis difficult.


Below are examples of Systemic Candidiasis in specific organs:-

a.

intra-abdominal
- peritoneal dialysis-related Candida peritonitis
- gut-injury related Candida peritonitis

   
b.

bone and joint
- Candida osteomyelitis
- Candida arthritis
   
c.

central nervous system
- neurosurgery-related central nervous system candidiasis
   
d.

eye
- Candida endophthalmitis
   
e.

gallbladder
- billary candidiasis
   
f.

heart
- cardiac candidiasis
   
g.

lung
- Candida pneumonia
   
h.

kidney and bladder
- fungus balls in urinary tract
- insignificant funguri
   
i.

liver and spleen
- hepatosplenic candidiasis
   
j.

pancreas
- pancreatic candidiasis
   
2.
Candidiasis of skin and mucosal surfaces
Candida can both colonize (that is, be present without causing disease) and infect any body surface. "Mucosal surfaces" refer to those body surfaces that are adapted to continuous or near-continuous exposure to moisture, such as the mouth and the vagina.

The following lists the categories of candidiasis of skin and mucosal surfaces:-
    a. asymptomatic colonization;
    b. cutaneous candidiasis;
    c. chronic mucocutaneous candidiasis;
    d. esophagitis;
    e. onychomycosis;
    f. oropharyngeal candidiasis; and
    g. vulvovaginitis (or Thrush).
       
GENERAL DIAGNOSTIC STRATEGIES
The diagnosis of almost any form of Candida disease requires an integration of clinical, epidemiological, and laboratory findings. The isolation of Candida from wounds, skin, urine, sputum, or stool specimens is not diagnostic of disease. On the other hand, growth of Candida from sterile specimens such as blood or cerebrospinal fluid is almost always diagnostic of infection.

1. DoctorFungus Corporation. Candidiasis: Overview and full index. Retrieved 11 June 2002, from http://www.doctorfungus.org/mycoses/human/candid/Candida_index.htm.
2.

Beck-Sagué, C. M., W. R. Jarvis, and the National Nosocomial Infections Surveillance System. Secular trends in the epidemiology of nosocomial fungal infections in the United States, 1980?1990. The Journal of Infectious Diseases, 1993; Volume 167:1247?1251.

3. DoctorFungus Corporation. Candidiasis: Oviewview and full index. Retrieved 11 June 2002, from http://www.doctorfungus.org/mycoses/human/candid/Candida_index.htm.