DIP Episode 459 - The Clutch STI Podcast (for Step 1-3)
Topic
Syphilis, LGV, Granuloma Inguinale, Herpes Simplex, Chancroid; STI differential diagnosis; Antibiotic management.
Key Takeaway
Differentiating STIs requires correlating the clinical presentation (pain/painless ulceration and lymphadenopathy) with specific causative organisms (T. pallidum, C. trachomatis, K. granulomatis, H. ducreyi) to guide targeted antibiotic therapy.
Episode Notes
Source / episode info
- Episode: 459
- Title: Divine Intervention Episode 459: The Clutch STI Podcast (for Step 1-3)
- Published: 2023-05-25
- Source: Episode page
One-liner
This episode provides a high-yield differential diagnosis of common ST Is, focusing on the distinct clinical triad (ulcer appearance, pain level, and lymphadenopathy status) for Syphilis, LGV, Granuloma Inguinale, Herpes, and Chancroid.
High-yield summary
- Syphilis: Caused by Treponema pallidum. Characterized by a classic triad: painless ulcer + painless regional lymphadenopathy (LAD). Primary chancre is the hallmark finding.
- LGV: Caused by Chlamydia trachomatis (L1–L3 serovars). Presents as a painless ulcer with painful LAD, often associated with intracellular inclusions on histology.
- Granuloma Inguinale: Caused by Klebsiella granulomatis. Characterized by a painless ulcer with NO regional lymphadenopathy. Histology shows granulation tissue and intracyloplasmic cysts.
- Herpes Simplex: Presents as painful vesicles/ulcers on an erythematous base, associated with painful LAD. Treatment requires Acyclovir; resistance necessitates Famciclovir (bypassing thymidine kinase).
- Chancroid: Caused by Haemophilus ducreyi. Characterized by a painful ulcer with painful LAD and often has a deep gray/black base.
- Syphilis Management Pearls: Penicillin is the drug of choice; Doxycycline can be used as an alternative, but penicillin remains mandatory for pregnant patients (requiring desensitization).
Learning objectives
- Differentiate the clinical presentations of major ST Is (Syphilis, LGV, Granuloma Inguinale, Herpes, Chancroid).
- Identify the causative organisms and key histological findings for each STI.
- Select appropriate first-line antibiotic therapy based on the specific diagnosis and patient status (e.g., pregnancy).
- Recognize potential complications of ST Is, such as neurosyphilis or leptospirosis.
- Understand the mechanism of action and resistance patterns for antiviral agents like Acyclovir.
Board exam buzzwords
| Condition | Key Finding | Association | Board Exam Tip |
| Syphilis | Painless chancre/ulcer; painless LAD | Treponema pallidum | Remember: Painless = Syphilis (or LGV, but the overall picture is key). |
| Lymphogranuloma Venereum (LGV) | Intracyloplasmic inclusions; painful LAD | Chlamydia trachomatis L1-L3 serovars | Doxycycline is preferred over Azithromycin for treatment due to lower failure rates. |
| Granuloma Inguinale | Painless ulcer; no LAD; granulation tissue base | Klebsiella granulomatis | The absence of lymphadenopathy is the key differentiator from Syphilis and LGV. |
| Herpes Simplex Virus (HSV) | Vesicles on erythematous base; multinucleated giant cells | Acyclovir/Famciclovir | If acyclovir resistance is suspected, use Famciclovir to bypass thymidine kinase deficiency. |
Rapid review table
| Topic | Key Point | Context | Exam Relevance |
| Syphilis | Painless ulcer + painless LAD | Primary stage chancre; T. pallidum | Classic board question setup for differential diagnosis. |
| LGV vs Granuloma Inguinale | LGV: Painful LAD; GI: No LAD | Differentiating the two most common STI differentials. | Focus on the pain level of the associated lymphadenopathy. |
| Herpes Treatment | Acyclovir (drug of choice) | HSV infection; Thymidine kinase activation required. | Know the alternative drug (Famciclovir) if resistance is suspected. |
| Leptospirosis | Conjunctivitis of fusion | Exposure to contaminated water/animal urine (e.g., Hawaii travel). | A high-yield "travel medicine" STI differential. |
Board-speak -> diagnosis
| Board-speak / Vignette phrase | Diagnosis / Concept | Why it fits |
| A 25-year-old male presents with a painless ulcer on his penis and non-tender inguinal nodes. | Syphilis (T. pallidum) | The combination of painless chancre and painless LAD is pathognomonic for primary syphilis. |
| A patient develops multiple shallow ulcers, associated with painful regional lymphadenopathy, and intracellular inclusions are noted in the base of the lesions. | Lymphogranuloma Venereum (LGV) | LGV is caused by specific serovars of C. trachomatis (L1-L3), which classically cause painful LAD. |
| A patient presents with multiple painless ulcers, but examination reveals no associated lymphadenopathy, and the base shows granulation tissue. | Granuloma Inguinale (K. granulomatis) | The triad of painless ulceration + absence of LAD is highly suggestive of this condition. |
| A sexually active young adult reports painful vesicles on an erythematous base with tender regional nodes. | Herpes Simplex Virus (HSV) | HSV classically causes painful lesions, and the presence of vesicles/ulcers points strongly to it. |
| The patient has a deep-seated ulceration that is acutely painful and associated with marked tenderness in the inguinal region. | Chancroid (H. ducreyi) | H. ducreyi infections are typically painful, unlike syphilis or LGV. |
| A penicillin-allergic pregnant woman diagnosed with primary syphilis requires treatment. | Syphilis Management | Penicillin is absolutely required for treating syphilis in pregnancy; desensitization protocols must be followed. |
Differential diagnosis / distinguishing features
Herpes Simplex vs Chancroid
| Key Features | Distinguishing Findings | Next Step |
| Herpes (Painful U, Painful LAD) | Vesicles on erythematous base; multinucleated giant cells. | Acyclovir/Famciclovir. |
| Chancroid (Painful U, Painful LAD) | Deep gray/black base; H. ducreyi; "School of fish" appearance. | Ceftriaxone or Azithromycin/Doxycycline. |
Leptospirosis vs Other ST Is
| Key Features | Distinguishing Findings | Next Step |
| Leptospirosis (Conjunctivitis, fever) | Exposure to animal urine; conjunctivus of fusion. | Supportive care + Doxycycline/Penicillin. |
Management pearls
- For primary syphilis, the standard treatment is Benzathine Penicillin G . If penicillin allergy exists, Doxycycline is an acceptable alternative.
- In cases of suspected LGV or Granuloma Inguinale, Doxycycline is generally preferred over Azithromycin due to better reported rates of cure and fewer treatment failures.
- HSV infections require prompt initiation of Acyclovir . If the patient has a history of acyclovir resistance (due to thymidine kinase mutation), use Famciclovir .
- For suspected Leptospirosis, prophylactic or empirical antibiotics like Doxycycline are indicated, especially in cases of conjunctivitis and fever following animal exposure.
Don't miss
Integration & clinical reasoning
- Infectious Disease/Travel Medicine: When encountering a triad of fever, conjunctivitis, and rash following travel to endemic areas (e.g., tropical regions), consider Leptospirosis alongside other bacterial causes.
- Pharmacology/Virology: Understanding the mechanism of acyclovir resistance (thymidine kinase mutation) is critical for selecting appropriate second-line antivirals like Famciclovir.
- Dermatology/GI: The differential diagnosis between ST Is and non-STI ulcers (e.g., trauma, vasculitis) must always be considered, but the specific lymphadenopathy patterns are highly suggestive of an STI source.
OMM / COMLEX integration
- Acute/Unstable Patients: In cases of suspected severe sepsis or septic shock secondary to an STI (e.g., necrotizing fasciitis from a deep ulcer), standard emergency management (IV fluids, broad-spectrum antibiotics) takes absolute priority over OMT.
- OMT Considerations: The primary focus remains on identifying the specific pathogen and initiating targeted antibiotic therapy; OMM/OMT is adjunctive only after stabilization and diagnosis are confirmed.
Concept connections / cross-references
- For a comprehensive review of general infectious disease principles, see [ Episode 37 ].
- The management of secondary syphilis complications, such as neurosyphilis and gummas, relates to systemic inflammatory processes covered in [ Episode 458 ].
High-yield association table
| Condition | Association | Mechanism | Clinical Significance |
| Syphilis | Painless chancre; painless LAD | Treponema pallidum (spirochete) | The classic presentation is highly suggestive, but other causes must be ruled out. |
| LGV | Intracyloplasmic inclusions; painful LAD | Chlamydia trachomatis L1-L3 serovars | Differentiates it from Syphilis and Granuloma Inguinale based on pain level. |
| Herpes Simplex Virus (HSV) | Vesicles on erythematous base; multinucleated giant cells | DNA virus; Thymidine kinase required for Acyclovir activation. | Knowing the mechanism of resistance guides drug choice (Famciclovir). |
| Leptospirosis | Conjunctivitis of fusion; fever | Leptospira interrogans | Requires consideration in patients with recent animal/water exposure, especially tropical travel. |
Key terms glossary
| Term | Definition | Context | Example |
| Painless Chancre | A non-tender ulceration at the site of primary infection. | Syphilis (Primary stage). | The initial lesion caused by T. pallidum. |
| Intracyloplasmic Bodies | Inclusion bodies found within host cells, often seen in LGV. | Histology/Diagnosis of LGV. | Helps distinguish LGV from other causes of genital ulcers. |
| Deep-gray base | The appearance of the ulcer bed, suggesting a necrotic or deep infection. | Chancroid (H. ducreyi). | A key physical exam finding differentiating it from HSV or Syphilis. |
| Desensitization | Process used to prepare an allergic patient for necessary drug administration. | Treating syphilis in pregnancy with penicillin. | Required when the mother cannot receive standard penicillin due to allergy. |
Study optimization
| Topic | Study Approach | Priority | Resources |
| STI Differential Diagnosis | Create a comparison chart based on 3 axes: Pain level, LAD status, and Base appearance. | High (Must memorize the triad). | Review board-style vignettes comparing Syphilis vs LGV vs GI. |
| Antibiotic/Antiviral Management | Focus on drug choice based on mechanism or patient status (e.g., pregnancy, allergy, resistance). | Medium-High (Clinical application). | Practice questions requiring selection of the optimal antibiotic regimen. |
| Systemic Complications | Review tertiary syphilis complications (gummas, neurosyphilis) and leptospirosis presentation. | Medium (Integration/Complication focus). | Link to Neurology/Rheumatology for systemic manifestations. |
Question pattern recognition
- Painless Ulcer + Painless LAD: Highly suggestive of Syphilis ( T. pallidum ).
- Painful Ulcer + Painful LAD, with intracellular inclusions: Suggests LGV ( C. trachomatis L1-L3 serovars).
- Painless Ulcer + No LAD: Strongly suggests Granuloma Inguinale ( K. granulomatis ).
- Vesicles on erythematous base (painful): Classic presentation of HSV, requiring immediate antiviral therapy.
Test yourself
Common mistakes to avoid
Common traps
Original transcript with highlights
Original transcript with highlights
All right welcome, my name is Divine. This is episode 459 of the Divine Intervention Podcasts. Into these podcasts I'm going to be talking about ST Ds. I'm going to be talking about ST Ds. Okay, I'm going to be talking about ST Ds. ST Ds are pretty high-oil to no-for step one, step two, and step three. And the thing about our friends and the USML is that we're actually quite good at writing the questions closely enough to will be kind of difficult to differentiate those things. So we're going to try to demystify those today and hopefully this should be a pretty short podcast. I just want to literally focus on what is high-oil to no. Because to be honest with you, you can go off in like many zebra directions with this and it doesn't really offer much of any benefit. So let's just get right into it. So what if they give you a question about a person? It's a 25-year-old male. He comes to the emergency room or comes to the office and says that, you know, for the last three days he has noticed this leisure on his penis and then you see like a penis picture on your exam and then they tell you that it's a painless leisure. Well, if you see the painless leisure as we will talk about one of the major things you should think about is syphilis. Although remember syphilis is not the only thing you should think about. It's not the only thing you should think about. So obviously this person very likely has syphilis. Remember, syphilis is caused by treponema pallidum. Treponema pallidum.
Now, you need to know that syphilis causes what a painless ulcer. The ulcer is painless and people that have syphilis, they will usually have lymphatic neuropathy. And that lymphatic neuropathy will also be painless as well. So they have a painless ulcer with a painless lymphatic, painless ulcer with painless lymphatic. And typically the way you treat penicillin is with, I mean, you treat syphilis is with penicillin. Again, many times you can just use benzethin penicillin and you're pretty much good to go. You're pretty much good to go. Although, you know, penicillin will lose a cell wall inhibitor and some people they just don't do very well with cell wall inhibitors. They have like allergies to these beta lactams. So in those circumstances, one good option you can actually explore is doxycycline. Remember, doxycycline is a tetracycline, some of those 30s inhibitors. Don't forget that these 30s inhibitors, they can be used for acne, sorry, they can be used for acne, and then they can be killeted by antacids. So if you're taking an antacid, you're taking a tetracycline, that tetracycline is not going to work. Remember, these tetracyclines actually have this ability to, they actually have this association with idiopathic intracranial hypertension. So they give you a question about a person on doxy therapy and then they've been having headaches, blurry vision, things of that nature.
You really want to, especially in an obese female, you want to think about idiopathic intracranial hypertension. So again, for person's penicillin, allergic and they have syphilis, quite a lot of them with some doxycycline, but there is an exception to that role. If a person has syphilis and they're pregnant, the only drug you can give them is penicillin. So what are you going to do for those people? You're going to desensitize them to penicillin and they're still going to give them that penicillin. So just something to kind of keep in mind. And in general, we know that syphilis kind of has steiges. So there's primary syphilis. That's usually the pinless shanker, right? That pinless also with pinless and infaddenopathy. And many times there's no test other than dark field microscopy. That'll be positive in that primary syphilis. But then syphilis, you can then go to the secondary stage. The secondary stage of syphilis, that's classically where you have the rash from the palms and soaps, the rash from the palms and soaps. And you know, you can also have like condiloma lada, you can have condiloma lada. Those are like work-like regions. And usually in the secondary phase of syphilis and actually in the tertiary phase, then you can start using these exotic tests. You can typically start off with a non-traponimo test for screening, something like RPR or VDRO. And then you can confirm the diagnosis with something like FTA ABS or MHATP. FTA ABS or MHATP.
So that's how you cannot confirm. But again, remember if you treat a person for syphilis, if you want to see if they've been cured, the smart move actually is also to check their RPR VDRO. Those are very good tests of cure for syphilis. For syphilis. I remember in tertiary syphilis, there are a bunch of problems you can get, like a retiredist that can present with the already dissection. They can also get gommas, they can have TBSTOR-SALES with they pretty much mess up their DORSO columns. Again, remember in general for TBSTOR-SALES is the DORSO columns you mess up. So you're going to have a positive rumberg test. You're not necessarily going to have any scrubs with, you're not necessarily going to have any scrubs with lateral corticospinal tract. Because sometimes people kind of mix this up with B2 of deficiency. B2 of deficiency causes a subacute combined degeneration of the spinal cord, a subacute combined degeneration of the spinal cord. So it's the in B2 of deficiency, you're going to have a positive rumberg because the DORSO columns are scored up. But basically, the thing that's scored up is not just the only DORSO columns, but also your lateral corticospinal tract in B12 deficiency, right in B12 deficiency. And you know, also another thing they can test with syphilis, you know, pressing gets penicillin and in hours after they get penicillin, it's not having fevers, myeloges, chills, that's pretty easier. That's the gyresh-hexheimer reaction.
That's the gyresh-hexheimer reaction. Typically, so what if care is all you need, but you know, they are trying to press you to give something. You can give them fluids, you can give them insets. Basically, what happened there is you give a cell wall inhibitor, exploded all these, Trappinima pallidum, and then all the stuff they have inside them, they released it, your mountain, powerful immune response against it, they get a hot water. And by the way, sometimes, instead of putting Trappinima pallidum as the answer for syphilis question, they'll just put spirochitis. I don't know for whatever bizarre reason, the USMEL is kind of fond of doing stuff like this. So it's just something you want to be mindful of, something you definitely want to be mindful of, right? Sometimes, they start of literally putting T-pallidum as an answer, they'll boost spirochitis as an answer. They also love to do that for Borrelia Bokdo-Freak, the thing that causes line disease because that's also spirochitis. Or if you get a question about like a person that goes to Hawaii and they have conjunctivus of fusion, that's obviously going to be leptospirosis, caused by leptospirin terrrogans. That's another high-yield spirochitis to keep in mind, for example. Okay, and then the next one I guess I'm just going to go to is lymphogram loma venereal, right? lymphogram loma venereal.
This one, typically, these people, they're going to have shallow ulcers, they're going to have shallow ulcers, and some of those ulcers will progress to like a booboo. So boobles are like just these big ginormous things. You can look up pictures of this online. But basically, the critical thing to know here is that they're going to have a painless ulcer with painful lymphadenopathy. Remember, we said for syphilis, we're T-paladum. They have a painless ulcer with painless lymphadenopathy. People that have lymphogram loma venereal, they're going to have a painless ulcer with pain full lymphadenopathy, right? And typically, this is caused by chlamydia trachometis. Remember chlamydia trachometis has all these fancy cerevars, right? The ones that cause lymphogram loma venereal, right? So remember the L in lymphogram loma venereal. So if you remember, the L1 to L3 cerevars. The L1 to L3 cerevars. And typically, right, when you do like your stology, you're going to see these intracidoplasmic bodies. Because these things, they are truly tracelola organisms. So in general, chlamydia does not gram sting. In fact, they love to play this party trick on your symelis with chlamydia, where I personally have like UTI symptoms or they have STI symptoms. And you do a gram sting and you don't see squat. That's a chlamydia infection right there. It's an intracellula organism. It's an intracellula organism. And how do we trick chlamydia?
One example, we're going to trick chlamydia with doxycycline. Doxycycline is the first line drug for treating chlamydia infections. It is preferred over zythromycin because the thing is in general, doxycycline is just associated with fewer treatment failures compared with zythromycin. So there's something I want to keep, keep in mind, something I want to keep in mind. Okay, how about the next one where we should talk about? Let's talk about gramoloma in venal. Sometimes they all call these dolovanosis on exams, dolovanosis on on exams. Now, these people also have a painless ulcer. They'll have a painless ulcer, but so you'll be like, come on, divine. Like, he learned that T-ballidoma has painless ulcer. You said LGV has painless ulcer. How about gramoloma in venal? They actually have a painless ulcer as well, but you have no lymphadenopathy. Right, so let's summarize here. T-ballidoma we said painless ulcer with painless lymphadenopathy. Lymphogranoloma venerium we said painless ulcer with pain full lymphadenopathy. Now, dolovanosis, which is gramoloma in granuloma, we said this is going to be a painless ulcer with no lymphadenopathy. Literally, painless ulcer with no lymphadenopathy. And this one is caused by kleptial agrar gramolumates. Right, and typically if you look at the base of the ulcers, you're going to see granulation, you're going to see granulation tissue. And this stuff, sometimes they'll tell you that, oh, in histology, you see these intracidoplasmic cysts.
You see these intracidoplasmic cysts. Right, and for this, you can use, again, doccycline or zythromycin, either one is completely fine. Doccycline or zythromycin is completely fine. Right, and one thing I will just maybe go ahead and say here is sometimes our friends at the endgame is they'll give you questions where they want you to pick out an antibiotic. And typically you notice that sometimes they can give you like two different macrolids. You're like, geez, how many people pick one macrolid from the other? And generally, if you ever get a question of two macrolids, pick zythromycin. Pick zythromycin. Is zythromycin is just very well studied, is very, very effective, and generally doesn't have as many side effects as we see with some of the other macrolids, like a rythromycin, for example. Remember, rythromycin is one of these fancy drugs that we can use for diabetic astroparases because it has the ability to activate motillin receptors. So one thing I'm going to say is if you're a person that loves the way I integrate things, you may be interested in some of the classes I have to offer. I offer step one classes, step two classes, and one big class that's coming up. I actually have a social sciences and ethics class that also covers quality improvement, professionalism, communications, that's taking place this Saturday. If you're interested, you should check my email through the website. And then I have this model load class. It's a 500 question class.
It's all multiple choice questions. And we're going to like very, very deeply dive into a lot of MDME topics. It's actually going to be going from June 1st to June 11th. I believe there will be one day we don't meet. But it's going to be a 50 hour course. You're starting next week. If you want to reserve a spot, just go ahead and shoot me an email and I can give you some more information. I actually made a separate podcast on that, on that class. Okay, let's go ahead and continue. So what do they give you a question about a person? They tell you that, you know, it's a 25 year old male and he comes in because he's going to have a lot of tenderness around his growing and then you see some vesicular lesions, right? Or you won't see some ulcers. You see some ulcers in his penis, like around his penile area. If you see something like that, obviously, this is going to be herpes. Right? It's going to be herpes. Remember herpes is pretty, pretty classic. And then you're going to see a painful ulcer on an aerothermatoid's base. Now, I mean painful vesicle on an aerothermatoid's base. Now, sometimes you may actually, in fact, the use in it is there. Why is it not everyone that has herpes that's going to have vesicles? Just be careful of all that. Especially the people that I know compromise like HIV patients, they know they necessarily have those painful vesicles, right? But classically, describe painful vesicles on an aerothermatoid's base.
And many times the classification here, you're going to see painful ulcers with painful lymphadenopathy. You can see painful ulcers with painful lymphadenopathy. And many times, if you were to do some histone, although most times for herpes, you're going to do nucleic acid amplification testing. But remember, you're going to see many times more tiny cleavage giant cells with herpes. You're going to see more tiny cleavage giant cells with herpes. And remember, in general, we're going to treat the stuff with acyclovere. Acyclovere is the drug of choice for treating herpes infections. Acyclovere is the drug of choice for treating herpes infections. Obviously, the person has herpes that is resistant to acyclovere. Then in that case, you're going to maybe consider using something more along the lines of false carnage. The thing is acyclovere needs a fine-meeting kinase to get activated. So if that fine-meeting kinase is mutated, then acyclovere will not be activated. And it's literally not going to work. So if it doesn't work, obviously, that's not a good good thing. So we're going to treat it with acyclovere. But again, if you're acyclovere resistant, you're going to go with false carnage. False carnage is a pyrophosphate animal. It's almost like it's been activated before you even give it. So it can basically bypass that family-team kinase step. So that's pretty, pretty helpful. So now, let's compare and contrast herpes with shankroid.
This probably last one I'm going to talk about, right? Shankroid. Shankroid also causes a painful ulcer. But this ulcer has a deep-grace base. Deep-grace base. And this one is also, so you may be like, well, divine, this one is also a painful ulcer like herpes. And to be honest, we feel this one will also have painful infadenopathy. So it's a painful ulcer with painful infadenopathy. But one very critical thing that will help you differentiate. Shankroid from herpes is that shankroid, the lymphadenopathy is usually superitive. So it's going to bring out posts. And also, you know, shankroid is a gram-negative infection. Obviously, herpes is not going to gram state. So shankroid is caused by hemophlos ducryl. Many of you have heard of this, knowing that hemophlos ducryl makes you cry. But basically, hemophlos ducryl is a gram-negative organism. So it's going to stain on, you know, with gram-staining. And typically on histology, you're going to see the school of fish appearance. You're going to see the school of fish appearance. And in many ways, you can actually treat shankroid. You can treat it with tetraaxone, tetraaxone, it's a pretty good drug for mostly mouth-loss species. And then you can also use a macrolid, right? Or you can use super-floxacid. Although in general, remember we're trying to avoid super-floxacid in certain people, right? Just in general, we try to avoid super-floxacid in these days.
You know, because you can kind of rupture your Achilles, which is maybe not a good thing, especially if you're a basco-bopler, or you can also prolong your QT interval. Remember, phyloquinolones have very, very strongly associated with prolongation of the QT interval. And obviously, if you're pregnant, you should also not be taking a phyloquinolone. So I would say for a person that has hemophlos ducryl, the smart thing you want to do in exams is just give them tetraaxone or give them some kind of macrolid. Now, let me just do a quick summary so that you have the big key point takeaways from this podcast. And all I'm just going to discuss is the ulcer pattern and the lymphodernopathy. You want all the other details, again, just take it from the top list into it again. This is going to be a short, short podcast. But again, remember, safely strap your nemapalidum causes a painless ulcer with painless lymphodernopathy. Lymphogram luma-vineerial, which is caused by the L1-L3 cerevars of chlamydia tracometis causes a painless ulcer with painful lymphodernopathy. And then, granulone in winali, which is also called dunovernosis, remember it's caused by Klepsiala granulomades, that one causes a painless ulcer with no lymphodernopathy. Painless ulcer with no lymphodernopathy. And then herpes those painful ulcer, painful lymphodernopathy, but the lymphodernopathy is not supportive and herpes those not gramps. Versus chancroid, chancroid causes a painful ulcer, it has a grache base.
Herpes tends to have more of an erythematos base. This one tends to have a grache base. The ulcer is tend to be saucer shaped as well for people that have chancroid. Remember, chancroid again is going to be a painful ulcer with painful lymphodernopathy that is operative. And again, it is gram negative. Okay, so I'm going to go ahead and pause here. Again, I do offer one on one tutoring for all the USMEL exams. Step one to step three. Preclinical med school exams, 30-ish-elf exams. And if you're interested in any of my review courses, I have a 25-hour step one course in July. I have a 20-hour step two step three course that actually is going to be in June. And then I have an NVME test-taking strategy course that's two and a half hours long, a four hour biostatistics class, and a five hour social sciences ethics, quality improvement, and healthcare systems class. And in the 50 hour class, taking place from June 1st to June 11th. If you're interested in any of these classes, should be an email through the website. I'll give you some more information. I have this podcast on Apple, on Google, on Spotify, I have a You Tube channel, the Vine Intervention USMEL podcast and videos. And then finally, I have a website known as divineinterventionlifelessons.com. I'm in your funeral, I'm a Christian, so I have this separate website. And I basically upload two podcasts a week from a biblical perspective. I try to address a life lesson.
Many people have listened to those and found them to be helpful. So again, and that actually has an Apple podcast associated with it called the Divine Intervention Life Lessons podcast. So thank you for listening to me today. Have a wonderful rest of your day. I will see you next time. God bless you. Bye for now. Thank you.
Practice questions — USMLE style
Question 1 — Dermatology/Infectious Disease
A 25-year-old male presents to the clinic with a lesion on his penis that has been present for several days. The ulcer is described by the patient as being painless, and upon physical examination, the accompanying inguinal lymph nodes are also non-tender and painless. Laboratory testing confirms the presence of Treponema pallidum. Which of the following statements regarding this condition is most accurate?
- A) Treatment should involve ceftriaxone due to its gram-negative nature.
- B) The primary diagnostic test for screening should be a direct fluorescent antibody (DFA) microscopy, and treatment is penicillin.
- C) The characteristic finding is a painful ulcer with associated suppurative lymphadenopathy.
- D) Due to the risk of systemic spread, prophylactic antibiotics are recommended regardless of symptoms.
Answer: B. Explanation: Syphilis, caused by Treponema pallidum, classically presents as a painless chancre (ulcer) and is often accompanied by painless lymphadenopathy. The podcast notes that DFA microscopy is a key diagnostic tool for primary syphilis. Penicillin (specifically benzathine penicillin) remains the drug of choice for treatment. Option A describes chancroid (H. ducreyi), which is gram-negative but causes painful lesions. Option C describes chancroid or potentially LGV, not typical syphilis.
Question 2 — Infectious Disease/Pharmacology
A pregnant patient with a history of suspected syphilis presents to the emergency department. Due to her pregnancy status, standard treatment protocols are highly restricted. The infectious disease specialist must administer an antibiotic that is safe for both the mother and fetus while effectively treating Treponema pallidum. Which drug class should be used, and what procedure is necessary if the patient has a known penicillin allergy?
- A) Doxycycline; desensitization to allow oral administration.
- B) Ceftriaxone; immediate discontinuation of all antibiotics.
- C) Penicillin; cross-reactivity testing followed by desensitization.
- D) Azithromycin; avoidance due to potential QT prolongation.
Answer: C. Explanation: The podcast explicitly states that if a person has syphilis and is pregnant, the only drug that can be given is penicillin. If there is an allergy concern (like a beta-lactam allergy), the standard procedure is not simply to avoid it but to desensitize the patient so they can still receive the necessary treatment. Doxycycline is contraindicated in pregnancy due to risks of tooth discoloration and bone growth issues, making Option A incorrect.
Question 3 — Dermatology/Infectious Disease
A young adult presents with multiple genital ulcers. The lesions are painful, have a deep-gray base, and are associated with markedly tender, swollen inguinal lymph nodes (lymphadenopathy). Gram stain reveals numerous gram-negative coccobacilli. Histological examination shows characteristic "school of fish" appearance. What is the most likely diagnosis, and what is the preferred initial antibiotic treatment?
- A) Syphilis; Penicillin G
- B) Lymphogranuloma Venereum (LGV); Doxycycline
- C) Chancroid; Ceftriaxone or Azithromycin
- D) Herpes Simplex Virus (HSV); Acyclovir
Answer: C. Explanation: The clinical picture—painful ulcers, deep-gray base, and painful/suppurative lymphadenopathy—is classic for chancroid, caused by Haemophilus ducreyi. The podcast notes that this organism is gram-negative. Treatment options include ceftriaxone or macrolides (like azithromycin). Option B describes LGV (C. trachomatis), which typically presents with painless ulcers and painful LAD. Option D describes HSV, which involves vesicles on an erythematous base.
Question 4 — Microbiology/Differential Diagnosis
A patient is diagnosed with a sexually transmitted infection characterized by multiple shallow genital ulcers. The causative organism is known to be an intracellular pathogen that does not stain well with Gram stain. Furthermore, the diagnosis requires specialized testing because the bacteria are obligate intracellular parasites. Which of the following statements accurately reflects the microbiology and management of this condition?
- A) The organism is Treponema pallidum; treatment should involve benzathine penicillin.
- B) The organism is Chlamydia trachomatis; doxycycline is preferred over azithromycin for treatment due to lower failure rates.
- C) The organism is Klebsiella granulomatis; the primary diagnostic method involves identifying intracellular cysts in tissue samples.
- D) The organism is Haemophilus ducreyi; diagnosis relies on visualizing gram-negative coccobacilli directly from the ulcer base.
Answer: B. Explanation: This scenario describes LGV, caused by Chlamydia trachomatis. The podcast emphasizes that C. trachomatis is an intracellular pathogen and does not stain well with Gram stain (a "party trick"). Doxycycline is highlighted as the preferred first-line treatment for chlamydia because it has been associated with fewer treatment failures compared to azithromycin. Option A describes syphilis. Option C describes granuloma inguinale, which involves Klebsiella but typically lacks significant lymphadenopathy.
Quick fire review
What is the organism responsible for syphilis?
Treponema pallidum.
Describe the classic presentation of primary syphilis.
Painless chancre (ulcer) with painless lymphadenopathy.
Which STI causes a painful ulcer with painful lymphadenopathy, and what is its causative agent?
Chancroid; caused by Haemophilus ducreyi.
What key finding differentiates LGV from syphilis regarding lymphadenopathy?
LGV has painful lymphadenopathy, whereas syphilis has painless lymphadenopathy.
Which antibiotic is the first-line treatment for Chlamydia infections and why is it preferred over Azithromycin?
Doxycycline; associated with fewer treatment failures compared to Azithromycin.
What specific finding on histology is characteristic of HSV infection?
Multinucleated giant cells (or tiny cleavage giant cells).
Syphilis presentation (ulcer/LAD)?
Painless ulcer and painless lymphadenopathy.
LGV presentation (ulcer/LAD)?
Painless ulcer and painful lymphadenopathy.
Granuloma Inguinale presentation (ulcer/LAD)?
Painless ulcer with NO lymphadenopathy.
What is the drug of choice for HSV?
Acyclovir.
Which organism causes chancroid, and what is its key physical feature?
Haemophilus ducreyi; Deep-gray base (or saucer-shaped).
If a patient with syphilis is pregnant, what must be used for treatment?
Penicillin (requires desensitization protocol).
What class of antibiotics should be avoided in pregnancy due to potential side effects like QT prolongation?
Fluoroquinolones.
Quick recall / Anki-style questions
Syphilis presentation (ulcer/LAD)?
Painless ulcer and painless lymphadenopathy.
LGV presentation (ulcer/LAD)?
Painless ulcer and painful lymphadenopathy.
Granuloma Inguinale presentation (ulcer/LAD)?
Painless ulcer with NO lymphadenopathy.
What is the drug of choice for HSV?
Acyclovir.
Which organism causes chancroid, and what is its key physical feature?
Haemophilus ducreyi; Deep-gray base (or saucer-shaped).
If a patient with syphilis is pregnant, what must be used for treatment?
Penicillin (requires desensitization protocol).
What class of antibiotics should be avoided in pregnancy due to potential side effects like QT prolongation?
Fluoroquinolones.