Hi, and thanks for your question.
You are right that chlamydia and gonorrhea are not present in saliva or blood and are therefore not passed this way. However, it is possible for gonorrhea and less commonly chlamydia to grow in a person’s throat. If an individual gives oral sex to a person with a penis which happens to have either gonorrhea or chlamydia, that infection can be passed via the semen into the throat and start growing there. If the person who now has an infection in the throat then gives oral sex on a penis which does NOT have an infection, that infection can be passed to the person receiving oral sex.
It really requires a direct transfer of the bacteria to a person’s throat through seminal fluid and then direct contact of a person’s genitals with the bacteria in a person’s throat for the infection to be passed this way. While it is theoretically possible, this is why we do not commonly see these infections passed through kissing on the mouth or even shallower kissing on the genital area.
It sounds like you’re already familiar with our STIs at a Glance chart! If you’re interested in seeing which STIs are commonly passed through various types of sex, check out our Know Your Chances charts found here: https://smartsexresource.com/about-stis/know-your-chances-0
Let us know if this does not answer your question or if you have any more questions or concerns.