Which of the following statement regarding normal microbial flora present on the skin and mucous membranes is true?

Normal microbial flora are more or less constant for each species and are broadly classified as residents and transients. Residents constitute a constant population which cannot be completely removed permanently, while transient organisms vary from time to time and are not permanent. Antimicrobials cannot remove the normal flora organisms completely, only transient removal is possible. Ref: Textbook of Microbiology and Immunology By Parija, Pages 647-9; Textbook of Microbiology By Ananthanarayan, 6th Edition, Page 555