Chapter 46: Sexually Transmitted Infections – Causes & Effects

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Okay, so you handed us Chapter 46 from Porth's Essentials of

Pathophysiology, and wow, it's dense, all about sexually transmitted infections.

Yeah, it covers a huge amount of ground.

You've got everything from tiny protozoa up to really complex viruses.

Exactly.

So our mission today, we're going to slice through all that detail.

We want to pull out the core pathology, the key clinical stuff, basically the things you absolutely need to remember.

Think of this as your high yield pass through the chapter.

And it's really timely information.

The source makes the point that STI rates are actually, well, increasing, which might surprise some people.

Increasing, despite better testing.

Yeah, and the chapter points to a few key reasons.

First, there's the stealth factor.

A lot of these infections are asymptomatic, so people spread them without knowing.

Okay.

Second, you've got the viral infections, HIV, hepatitis B, HPV, herpes.

They're, well, incurable right now.

They stick around.

Right, the permanence factor.

Exactly.

And third, treatment is getting trickier.

We're seeing more and more drug resistance, especially with things like gonorrhea.

Okay, so the chapter itself is pretty well organized, thankfully.

It seems to break things down into three main chunks.

That's right.

It looks at infections mainly affecting the external genitalia first.

Then it covers infections localized to the vagina.

And finally, the ones that can spread the vaginal urogenital systemic infections.

Yeah, and that structure helps highlight a really key distinction they make early on.

The four big curable bacterial or protozoal ones.

Right, that's trachomoniasis, syphilis, gonorrhea, and chlamydia.

Versus the four major incurable viral ones.

Knowing which category an infection falls into seems pretty fundamental.

Absolutely foundational.

Okay, let's unpack this.

Starting with those infections affecting the external genitalia.

First up is condylamata acuminata.

Better known as genital warts caused by HPV, human papillomavirus, and the source says this is the most common STI.

Estimates around 20 million Americans carrying it.

Yeah, it's incredibly prevalent.

HPV is a DNA virus, and its whole deal is causing these proliferative lesions on squamous epithelium.

Skin and mucous membranes.

Right, but the really critical thing to grasp with HPV is the difference between the types.

Some cause warts, sure, but types 16 and 18?

Those are the high risk ones.

High risk because they're linked to cancer.

Cervical dysplasia, antigenital cancer.

Precisely, that's the key takeaway for HPV types.

And the warts themselves, the lesions, they can look pretty different, right?

Soft fleshy bumps, sometimes internal cauliflower -like things.

Yeah, the presentation varies.

But here's something interesting and kind of hopeful from the text.

Most HPV infections are actually transient.

Meaning they just go away on their own.

And about 90 percent of people, yes.

Within two years, the immune system often clears it.

So most infections are asymptomatic and temporary.

Okay, so if it often clears and diagnosis isn't a blood test, how do they confirm it, especially those high risk types?

Well, routine screening relies on visual inspection and PAP tests, obviously.

But for specifically detecting those high risk DNA strains, like 16 and 18, there's a specialized FDA approved test.

A solution hybridization method.

Gotcha.

And since you can't cure a persistent viral infection, prevention becomes key.

The vaccines.

Absolutely.

Gardasil, Gardasil 9, Cervarix.

They're designed specifically to protect against those main cancer causing types, 16 and 18.

And usually the common wart types, 6 and 11 too.

Okay.

Let's move to the other big viral player for external genitalia, genital herpes.

HSV.

Right, herpes simplex virus.

Type 2, HSV2 is the one we typically associate with genital infections.

But the book mentions HSV1 showing up there more often now.

Increasingly, yes.

Usually through oral to genital contact, the distinction is becoming a bit blurrier in practice.

Now you mentioned earlier the mechanism here is fascinating.

What makes HSV different?

Ah, yes.

It's a neurotropic virus.

That's the term to remember.

Yeah.

It means after the initial infection on the skin or mucosa.

It doesn't just stay there.

Nope.

It actually travels up the peripheral nerves and it sets up shop, goes dormant, establishes latency in the nerve cell bodies, specifically the sacral dorsal ganglia for genital herpes.

Whoa.

So it hides out in the nervous system where the immune system and drugs can't easily get to it?

Exactly.

It basically goes silent, changes how its genes are expressed, making it invisible to our current cures.

And then it waits.

Waits for what?

For a trigger.

Stress, illness, maybe some local trauma.

Then it reactivates, travels back down the same nerve pathway and causes another outbreak on the skin.

That's recurrence.

That explains why it keeps coming back.

So how does that first episode compare clinically to the recurrences?

Is there a difference?

Oh, a big difference.

The first episode infection is usually much more severe.

You often get systemic symptoms, fever, feeling generally unwell, swollen lymph nodes.

The lesions are typically more numerous, more painful, and you shed the virus for longer, maybe 10, 15 days.

Okay.

And the lesions themselves, what's the pattern?

You usually see painful little bumps, papules.

They quickly turn into fluid -filled blisters, vesicles.

Then those break open into wet ulcers and finally they crust over and heal.

And the recurrences?

Usually much milder.

Fewer lesions, less pain, shorter duration.

And often people get a warning sign, those prodromal symptoms.

Like a tingling or itching.

Exactly.

Little heads up that the virus is on the move again down the nerve.

So for diagnosis, given you want to know the type and it can be tricky.

Yeah.

What's the preferred?

It's way more sensitive than the old viral cultures and it can easily tell HSV1 from HSV2.

It's still no cure.

Still no cure.

Treatment is all about management.

Using antiviral drugs like valacyclovert to shorten the outbreaks, reduce how often they happen, and really importantly, decrease viral shedding to lower the risk of transmission.

All right, let's shift gears.

Group two, the vaginal infections, canadiasis, trichomoniasis, bacterial vaginosis.

These are more about disrupting the local ecosystem.

Largely, yes.

Though the source is very clear.

Only one of these three, trichomoniasis, is a definite STI requiring partner treatment.

That's a key distinction.

Let's start with candidiasis, the classic yeast infection caused by candida albicans, a fungus.

Right.

And this one is less about transmission and more about the vaginal environment getting thrown off balance.

Let's throw us it off.

Common culprits are things like antibiotic use, wiping out the good bacteria, or high hormone levels like from pregnancy or birth control pills.

Diabetes and weakened immunity also increase risk.

Okay, so if you had to paint a picture based on the text, what are the dead giveaways for candidiasis?

Two main things.

Intense itching vulvovaginal pruritus and a very characteristic discharge.

It's described as thick, white, curd -like, think cottage cheese, and importantly, it's usually odorless.

Got it.

Thick, white, curd -like, odorless discharge plus itching and diagnosis.

Usually confirmed by seeing the budding yeast or the hyphae, the little filaments, on a wet mount slide, often using KOH solution.

And because it's fungal overgrowth, not bacterial, the vaginal pH typically stays low, acidic less than 4 .5.

Okay.

And now contrast that with trichomoniasis caused by trichomonas vaginalis.

This one is an STI.

Absolutely.

It's an anaerobic protozoan a little single cell organism with a flagellum, and it's very common.

The source mentions men are often asymptomatic carriers.

Frequently, yes.

They might have it in their urethra and not know it, which makes controlling the spread pretty difficult.

But in women, it can be quite symptomatic.

What's the classic discharge description here?

It's quite different from yeast.

Think copious, a lot of it frothy, often malodorous, and typically greenish or yellow.

Frothy, smelly, yellow.

Got it.

And the book mentions a specific visual sign.

Yes.

The classic strawberry spots, tiny red hemorrhages on the cervix.

Not always seen, but very suggestive is present.

And this isn't just uncomfortable, right?

There are complications.

Definitely.

It increases the risk of getting or transmitting HIV,

can contribute to tubal infertility, and is linked to problems in pregnancy like premature birth.

So diagnosis relies on seeing the bug itself.

Yes.

The key is moutslide.

That movement is diagnostic.

And unlike Candida, Trichomonas makes the vaginal environment less acidic.

The pH is usually high, above 6 .0.

And treatment needs to be systemic and include partners.

Absolutely critical.

Oral metronidazole, or tinnitus, for both the patient and all sexual partners.

Otherwise, you just get reinfection.

Okay.

Last one in this group, bacterial vaginosis, BV.

The name is interesting vaginosis, not vaginitis.

Why that distinction?

That's a really important point.

It signals that there isn't a major inflammatory response, not like you see with Trich or Candida sometimes.

BV is more of a shift in the bacterial balance.

A polymicrobial shift, the book calls it.

Exactly.

You lose the beneficial lactobacilli, the ones that make hydrogen peroxide and keep things acidic.

And instead, you get an overgrowth of various anaerobic bacteria like Gardnerella vaginalis and others.

And the main symptom resulting from that bacterial overgrowth is?

The characteristic discharge, usually thin, grayish -white, and it has a very distinct foul fishy odor.

Ah, the fishy odor.

That's the classic sign.

It is.

And diagnosis uses what are called the AMSL criteria.

You generally need three out of four things.

That typical thin grayish discharge, the fishy odor, especially when you had a drop of potassium hydroxide, that's the WIF test, a vaginal pH above 4 .5, and finding clue cells on the wet mount.

Clue cells?

What are those?

They're vaginal epithelial cells that look kind of fuzzy or granular because they're just covered in bacteria.

Very characteristic to look under the microscope.

Okay.

Now, here's where it gets really important, as the source says.

We're moving into that third category.

Infections that don't just stay local but can spread systemically.

Big consequences here.

Right.

Chlamydia, gonorrhea, and syphilis.

These are the ones that can cause serious long -term damage if not caught and treated.

Let's start with chlamydia, caused by Chlamydia trecomatis.

The book calls it the most prevalent reported STI in the U .S.

Why reported?

Because it's so often silent, asymptomatic.

Many cases likely go undiagnosed.

And chlamydia is tricky.

It's an obligate intracellular bacterium.

Meaning it has to live inside our cells.

Exactly.

It can't reproduce on its own outside a host cell.

It's a master of hiding.

And it has that two -part life cycle, right?

Yes, the elementary body and the reticulate body.

The elementary body is the small, tough, infectious foam that can survive briefly outside cells to spread.

Once it gets inside a cell, it transforms into the larger reticulate body, which is the metabolically active form that actually replicates, makes more chlamydia before converting back to elementary bodies to burst out and infect new cells.

Complicated and dangerous because it's often silent.

What are the major long -term problems if it's not treated?

In women, the big risk is Pelvic Inflammatory Disease, PID.

That inflammation can scar the fallopian tubes, leading to infertility or ectopic pregnancy.

It's a huge issue.

And in men?

While it can cause epididymitis, the most serious complication mentioned in the source is Reiter syndrome.

It's described as that triad, urethritis, conjunctivitis, and arthritis, particularly in the large weight -bearing joints.

Though, you know, the direct causal link is debated sometimes.

It's a classic association.

Okay.

Since chlamydia and gonorrhea often hang out together and both can be silent, how has diagnosis improved?

Diagnostics have gotten much, much better with NICETS nucleic acid amplification tests.

Like PCR?

Exactly.

They're incredibly sensitive.

They can detect the genetic material of the bacteria.

And crucially, they can often test for both chlamydia and gonorrhea from the same sample, even urine.

Makes screening much easier.

And treatment for chlamydia is relatively straightforward.

Generally, yes.

Usually a single dose of azithromycin or a course of doxycycline works well.

Okay.

Let's talk gonorrhea then, caused by Neisseria gonorrhea, a different kind of bacterium.

Yeah.

It's a pyogenic, meaning pus -forming gram -negative diplococcus.

Looks like little pairs of coffee beans under the microscope.

And this one is known for being quite virulent and spreading readily.

Spreading beyond the genitals.

Oh, yes.

Like chlamydia, it can cause PID in women, prostatitis in men, but it can also get into the bloodstream and cause disseminated gynecological infection, DGI, which can affect joints, skin, even the heart valves.

And the symptoms, are they usually obvious?

In men, often yes.

The classic presentation is urethral pain.

And that characteristic discharge, typically creamy yellow, sometimes even blood -tinged, quite noticeable.

But maybe not so much in women.

Often milder or nonspecific in women.

Maybe some vaginal discharge, pain with their menstrual period.

But yeah, a significant number can be asymptomatic or have very subtle symptoms.

Now, the big issue with gonorrhea, as you mentioned earlier, is drug resistance.

The chapter seems to really emphasize this.

It's a huge problem.

The gonococcus is just incredibly adaptable.

We've thrown so many antibiotics at it over the decades.

Sulfa drugs,

penicillin, tetracyclines, fluoroquinolones, like Cipro.

And it developed resistance to all of them.

Pretty much, yeah.

Resistance emerged relatively quickly at each class.

That's why treatment guidelines have had to change so often.

So what's the recommendation now?

Because of widespread resistance, especially to fluoroquinolones,

the current CDC standard is dual therapy.

Not just one drug, but two different ones given together.

Why two?

To hit the bug harder and from different angles, basically.

It increases the chance of cure and, hopefully, slows down the development of resistance to the remaining effect of drugs.

The standard combo now is an injectable syphilis boron, ceftriaxone, plus an oral dose of azithromycin.

Injectable plus oral.

Okay, that highlights the seriousness.

All right, the last of the big systemic three,

syphilis, trypanema pallidum.

The spirichet, a long corkscrew -shaped bacterium.

And this one is notorious, not just for its stages, but because it can cross the placenta.

Leading to congenital syphilis, which can cause severe birth defects or even stillbirth.

Exactly.

A devastating outcome.

So let's talk about the stages.

They're really distinct and crucial to know.

Stage one, primary syphilis.

What's the hallmark?

The chancre.

C -H -A -N -C -R -E.

It's typically a single ulcer that appears at the site where the bacteria entered the body.

The key features to remember are that it's usually painless and feels firm or hard to the touch, indurated.

Painless is a key word there.

Easy to ignore, maybe.

Very easy to ignore.

And it's teeming with spirichetes, so it's highly infectious.

But then it heals up completely on its own, usually within a few weeks.

Even without treatment.

Yes.

Which is dangerous because the person might think they're cured, but the bacteria have just moved on.

Into the bloodstream, leading to stage two, secondary syphilis.

Right.

This is the systemic stage.

It usually shows up weeks or months after the chancre heals.

People might feel generally unwell, fever, sore throat, fatigue, swollen glands.

But the classic sign is a rash.

What kind of rash?

It's often widespread.

It can be macular, papular, sometimes pustular.

But the really characteristic location is on the palms of the hands and the soles of the feet.

That's a major clue for secondary syphilis.

Palms and soles.

Got it.

Any other lesions?

Yes.

You can also see moist, wort -like lesions called condylamatolata in warm, damp areas like the groin or underarms.

And these are also highly infectious.

And like the chancre, these secondary symptoms, they also resolve on their own.

Eventually, the disease then enters a latent phase, which can last for years, even decades, with no symptoms at all.

Until potentially stage three, tertiary syphilis.

This is the late destructive stage.

It doesn't happen to everyone with untreated syphilis, maybe about a third, but it's devastating when it does.

It can manifest in a few ways.

Like what?

You can get gummas.

These are localized rubbery necrotic lesions that can occur in skin, bones, organs, pretty much anywhere.

You can get cardiovascular syphilis, particularly affecting the aorta, leading to aneurysms.

Or you can get neurosyphilis.

Affecting the brain and spinal cord.

Yes.

Leading to things like dementia, personality changes, blindness, paralysis,

really severe neurological damage.

Wow.

So diagnosis for syphilis relies on?

Primarily on blood tests,

serology.

There are screening tests like the VDRL or RPR, and then more specific confirmatory tests like the FTA, ABS.

And treatment,

is it still penicillin?

Amazingly, yes.

After all this time, treponema pallidum has remained largely sensitive to penicillin.

Long -acting injectable penicillin G is still the treatment of choice for all stages, assuming no allergy.

Okay.

We've hit the big bacterial and viral players.

The chapter also briefly touches on a few other things, like molluscum contagiosum, but it also includes Zika virus.

That feels a bit different.

It is different, and its inclusion shows how our understanding of SDIs evolves.

Zika is primarily spread by 80s mosquitoes, we know that.

Right.

But it's now well documented that it can also be transmitted as sexually vaginal, anal, even oral sex, and from mother to fetus during pregnancy.

And the illness itself is usually pretty mild, isn't it?

Fever, rash, joint pain?

Generally, yes.

Many people might not even realize they have it.

So why is it such a big deal in this context?

What's the major concern?

The concern isn't the acute illness in the adult.

It's the devastating impact it can have if a pregnant person gets infected.

It's teratogenic.

Meaning it causes birth defects.

Severe ones.

The most well -known is microcephaly.

The baby is born with a very small head and underdeveloped brain.

But there are other serious brain defects, eye problems, impaired growth, a whole constellation of issues termed congenital Zika syndrome.

And there's no vaccine or specific treatment right now.

Not yet.

So prevention is absolutely everything.

That means mosquito control, avoiding travel to affected areas if pregnant or planning pregnancy, and using barrier methods like condoms during sex, especially if a partner has traveled to an area with Zika.

That really underscores the expanding definition of STIs.

Okay, that brings us near the end of this really comprehensive chapter walkthrough.

If we boil it down, what are the absolute core concepts?

I think we've hit them.

Understanding viral latency, like how herpes hides in the nerves.

Grasping the ecological shift in BV.

Recognizing the distinct stages of syphilis, from the painless checker to tertiary gummas.

And definitely appreciating the challenge of drug resistance, especially with gonorrhea needing dual therapy.

It really comes down to understanding the why behind the disease process and the treatment strategy.

Yeah.

And remembering those key details, HPV 16 and 18 for cancer risks, the rash on palms and soles for secondary syphilis, Reiter syndrome as a potential chlamydia complication, the need for partner treatment in trichomoniasis.

It's a lot, but connecting the pathogen to the pathology helps.

Absolutely.

Knowledge application starts with understanding the mechanism.

So what does this all mean for you listening?

Well, consider how STIs are constantly evolving.

Rates are up, resistance is growing.

Even definitions are changing with things like Zika.

Makes you wonder, doesn't it?

Beyond just finding the right antibiotic or antiviral for the individual,

what bigger systemic changes in public health, in global health, do we need to really tackle these often silent infections that cause such serious long -term harm?

That's a really important question to think about.

Definitely something to mull over.

Well, thank you for sharing this chapter with us.

It was a thorough exploration.

We hope this deep dive helps you synthesize this crucial information.

Thanks for joining us and we'll see you next time.