Preface

Candidiasis is an infection caused by *Candida* spp., mostly *Candida albicans*. Although *Candida* species, a yeast, normally exists in the human body on the skin and in the mouth, throat, gut, and vagina, it does not cause infection; however, sometimes yeast proliferation occurs, and *Candida* spp. can cause several infections, such as an oral infection affecting the mouth and throat, called oropharyngeal candidiasis (thrush), as well as vulvovaginal, oesophageal, intestinal, and invasive candidiasis. Oesophageal candidiasis is a common infection in HIV/AIDS patients. The pathogenesis of candidiasis in humans is not completely understood. Infection caused by *Candida* spp. creates a serious problem in humans because of drug resistance. Investigation of new and effective active substances against pathogenic *Candida* spp. and a better understanding of the molecular mechanisms involved in the formation of antifungal resistance will help prevent *Candida* infection among individuals with immunological deficiency and will make antifungal therapy much more effective. This book provides a comprehensive overview of the latest information on *Candida* spp. and candidiasis, and will be useful to biologists, mycologists, chemists, molecular biologists, geneticists and agriculturists.

In the first section of the book, the history and taxonomic hierarchy, diversity, sexual reproduction, invasion biology, antifungal resistance, identification and genetic structure of *Candida* spp., novel and natural compounds for candidiasis treatment, and interactions between *Candida* spp. and cancer development are discussed. Molecular mechanisms and biofilm-related factors responsible for development of antifungal drug resistance in *Candida* species, together with antifungal drug resistance, multi-drug resistance, and related resistance mechanisms are reviewed. The second section examines the molecular identification of targeted DNA regions, and the advantages and disadvantages of each approach, as well as prospective new advances brought about by modern technology. Traditional and molecular laboratory methods for diagnosing candidiasis are reviewed, with a discussion of PCR-based and non-PCR-based methods. The third section reviews pathogenicity, signalling pathways, and drug delivery systems that have the ability to accelerate the accumulation of drugs in different cutaneous layers. The final section considers antibiofilm activity against *Candida* spp., and the new molecules capable of preventing the formation of biofilms or eradicating them. This section also discusses changes in fungal physiology, host-pathogen interactions between cells and antibiotics during the treatment of COVID-19 infection using proteomic studies to identify proteins associated with fungi, and antifungal activity of propolis as an alternative natural treatment method for *Candida* species.

I would like to thank IntechOpen for offering me the opportunity to participate in this project, which could not have been successfully concluded without a strong support group. First of all, my husband and my daughter supported me with love and understanding. Thanks for your unwavering support. Second, I am grateful to all the authors and my colleagues around the world who have collaborated with me on this

book project and have provided original photographs, figures and graphics related to the subjects discussed. Finally, my sincere thanks go to Ms. Marica Novaković for her guidance and to other members of the IntechOpen staff for their help with this book project.

#### **Tulin Askun**

Section 1

*Candida* spp. Growth

Development, Invasion

Biology Drug Resistance

Genes and Molecular

Mechanisms

Professor, Department of Biology, Faculty of Science and Art, Balikesir University, Balikesir, Turkey

## Section 1

*Candida* spp. Growth Development, Invasion Biology Drug Resistance Genes and Molecular Mechanisms

### **Chapter 1**
