Which is false regarding sexually transmitted diseases (STDs) ?

A. Since STD pathogens are susceptible to drying out, they require direct contact with mucous membranes for transmission.

B. Treponema pallidum: causative agent of syphilis

C. Diagnosis of gonorrhea: Gram-negative diplococci in male's urethral discharge

D. Tertiary syphilis: presence of chancres at site of infection containing pathogen

All the options are true.

Explanation:

STD transmitted through sexual intercourse. They transmitted by the body fluids, mucous membranes, vaginal fluids or semen. But it can't be transmitted through the dried semen or vaginal fluid and in less than 20 minutes the body fluids are dried off.

Treponema pallidum is the causative agent of syphilis. It is bacteria. The vector is always human and transmitted during sexual intercourse. Syphilis is 3 types such as primary, secondary, and tertiary syphilis. In tertiary syphilis, chancers are present at the site of infection.

Gonorrhea is another STD caused by bacteria Neisseria gonorrhoeae. It is detected from the swab from male urethral discharge. This is also a gram-negative diplococci bacteria.