Yesterday I read the results from the new research on Doxy-PEP. It surprised me to find that doxycycline is quite effective in preventing gonorrhea when it is has become so ineffective in treating it - and also the pervious pilot studies on Doxy-PreP demonstrated that it was ineffective when it comes to gonorrhea. This brought up a broader question for me about how aniti-biotics work. One time a doctor told me: "We do not treat the disease - we treat the patient," when I asked him a question about antibiotic resistant bacteria strains. Does this mean that antibiotic resistance is not just a function of bacterial adaptation, but also depends on each individuals immune-system functioning, so that antibiotic resistance is best pictured as a bacteriaXimmunsystem interaction? In a similar vein, I was wondering if antibiotic resistance is a categorical phenomena vs. a matter of degree, so that bacteria are more or less resistant to a given antibiotic vs. not resistant or completely resistant? Further, I am often confused whether antibiotic resistance occurs on the level of community or on an individual level. I always thought that it happens on a community level. But sometimes it is implied that taking too many antibiotics may make the individual that takes them antibiotic resistant (or more prone to acquiring anti-biotic resistant infections) - which would again lead us to the first question of whether the patient or the disease is treated. I would like to have answers to these questions because I think it can inform my choices in regards to when and what antibiotics to take for PEP when it seems indicated - and when the risks of taking antibiotics might outweigh the risks of not taking them, vice versa. Thank you very much for reading and considering my questions :) 

Regarding doxy-PEP let me start by pointing out that the protective effect against gonorrhea seen in some studies was not expected.  In addition doxy-PEP was not nearly as impactful for gonorrhea prevention as it was for prevention of chlamydia and syphilis infections.  This outcome is explained by the fact that the proportion of gonorrhea strains resistant to doxycycline is always higher than any resistance of chlamydia or syphilis to doxycycline.  In addition, the proportion of gonorrhea strains with doxycycline resistance is geographically variable so it is expected that due to regional variation in doxycycline susceptibility, doxy PEP will be more effective for gonorrhea in some areas than others and that due to continuing evolution of the bacteria resistance will likely increase with more and more use of doxycycline.  Part of this continued development of resistance over time will depend on how much doxycycline is used- the more widespread use is, the more rapidly resistance is to develop.

In general, some of the effect of doxy-PEP is due to the fact that it, as a generalization, takes less antibiotic to prevent an infection than to cure it.  Thus doxy-PEP may be preventing some infections that would not be cured by the same antibiotic.  

The human immune system controls infections even without antibiotics some of the time but not always and not before infections can cause complications and/or are passed to others.  Infections occurring in persons who have depressed immunity, as a generalization, as harder to treat than infections in persons with healthy immune systems.  Antibiotics work better in persons with healthy immune systems.

Regarding antibiotic resistance, as bacteria become resistant to antibiotics, they do not convert from always being effectively treated by the drug to never being effectively treated; rather the proportion of persons who fail treatment increases.  

I hope I've addressed your questions. Doxy-PEP is a powerful tool for STI prevention in those at highest risk for infection.   The more it is used however, the more likely it is that its use will select for development of resistance-.  EWH  

I have one additional question. Because in the past year, I have experienced symptoms of a urethrits (burning sensation while peeing, sometimes strong, and elevated WBC (5-10) and few bacteria in standard urine test - while PCR urine tests didn't detect any STI). In these cases I took Cotrim for 5 days (2 x 960mg), after which the symptoms disappeared and the urine went back to normal. However, the last two times Cotrim didn't do the job, and it only disappeared after taking Cefdinir (2 x 300mg) for 3 days. So I have been wondering: 1. How frequently does condom-less sex trigger a urethritis in men? 2. Is a burning sensation while peeing a reliable indicator for an uretheral infection that requires treatment? And: 3. How big is the concern of antibiotic resistance of bacteria (like E. coli) that can cause UTIs and that are not part of the typical group of STI bacteria (like chlamydia and ghonorrhea). 

I must admit that I get super-anxious at any sign of a urethritis and test my urine about once per month, and perhaps end up over-using antibiotics, because about 5 years ago, I had a terrible acute bacterial prostatitis that required 2 months of antibiotic treatment (and the urologist told me that he was very worried about sepsis - he also said that he didn't think it was caused by an STI - although initially I had tested positive for chlamydia at that time). 

1. How frequently does condom-less sex trigger a urethritis in men? 

During sex bacterial can be introduced into the urethra.  Many of these bacteria are normal and cause no irritation.  Sometimes however the body reacts to the introduction of "unfamiliar" bacteria to result in burning and other signs of inflammation such as WBCs in the urine.  This irritation is called non-gonococcal urethritis (NGU) and can be due to a number of bacteria, some of which can be transmitted to others (chlamydia for instance) and some of which, other than causing irritation do not cause problems for partners (this includes oral and rectal bacteria).  When caused by a partners normal oral or rectal bacteria antibiotics may hasten resolution but typically such problems also go away by themselves.

2. Is a burning sensation while peeing a reliable indicator for an uretheral infection that requires treatment?

Sometimes, not always. Certainly all typical STIs (e.g. gonorrhea, chlamydia, can also be totally asymptomatic)

3. How big is the concern of antibiotic resistance of bacteria (like E. coli) that can cause UTIs and that are not part of the typical group of STI bacteria (like chlamydia and ghonorrhea). 

Typically antibiotic resistance is no a problem in such situations

EWH