Typhoid Fever: Pathogenesis (vectors, bacteria), Symptoms, Diagnosis, Treatment, Vaccine

Summary

This video discusses typhoid fever, its causes, transmission, symptoms, diagnosis, and treatment. Typhoid fever is caused by the bacteria *Salmonella enterica* serovar typhi or paratyphi and is transmitted through contaminated food or water, especially in areas with poor sanitation. Symptoms include fever, abdominal pain, and rose spots. Diagnosis is based on exposure history and symptoms, confirmed through tests like blood and stool cultures. Treatment involves antibiotics, though resistance patterns vary. Prevention focuses on sanitation, hygiene, and vaccination. The video also covers chronic carriage and relapse in some cases.

Takeaways

• 🦠 Typhoid fever is caused by Salmonella enterica serovar Typhi or Salmonella Paratyphi, with slight variations in clinical presentation, collectively known as enteric fever.
• 🤒 Typhoid fever is transmitted between humans via direct or indirect contact, often through contaminated food or water. Children, young adults, overcrowding, and poor sanitation increase the risk.
• 🧬 The bacteria survive gastric acids, penetrate the intestinal lining, and spread through lymphoid tissue, entering the bloodstream to cause systemic symptoms.
• 🌡️ Symptoms appear 5 to 21 days after ingestion, beginning with a 'stepwise' fever in the first week, followed by abdominal pain and rose spots in the second week, and potentially intestinal bleeding and splenomegaly in the third week.
• 🩺 Diagnosis of typhoid fever is based on clinical suspicion, especially after exposure to endemic areas. Blood and stool cultures can confirm the diagnosis, though sometimes empiric diagnosis is used.
• 💊 Treatment includes antibiotics like fluoroquinolones, azithromycin, and ceftriaxone. Treatment may vary based on local resistance patterns, with multi-drug-resistant strains being a concern.
• 🔄 Relapse can occur 2 to 3 weeks after resolution, with symptoms reappearing depending on the antibiotic used and local resistance patterns.
• 👩‍⚕️ Chronic carriage happens in 1-5% of cases, especially in adult women or those with biliary diseases. Carriers can excrete the bacteria for over 12 months, with gallstones acting as bacterial reservoirs.
• 💧 Prevention of typhoid fever includes access to clean water, proper sanitation, hygiene practices, and vaccination.
• 📚 Historical reference to 'Typhoid Mary' highlights the importance of identifying chronic carriers who can spread the disease without showing symptoms.

Q & A

What causes typhoid fever?

Typhoid fever is caused by an infection with a gram-negative bacterium called *Salmonella enterica* serovar Typhi, or related bacteria like *Salmonella paratyphi*, which has subtypes A, B, and C. These bacteria lead to different clinical presentations, but they all cause typhoid fever.

How is typhoid fever transmitted?

Typhoid fever is transmitted from human to human, either through direct contact or indirectly via contaminated food or water. Poor sanitation and overcrowding are risk factors that facilitate the transmission.

What are the main risk factors for contracting typhoid fever?

The main risk factors include being a child or young adult, overcrowding, and poor sanitation. These conditions increase the likelihood of direct or indirect contact with contaminated food or water.

How do Salmonella Typhi and Paratyphi bacteria infect humans?

These bacteria are ingested orally, survive stomach acids, and enter the duodenum. They penetrate the intestinal epithelium and invade lymphoid tissue through mechanisms like entering via M cells or using the CFTR chloride ion channel.

Why might patients with cystic fibrosis be less susceptible to typhoid fever?

Cystic fibrosis patients may be less susceptible because the bacteria use the cystic fibrosis transmembrane conductance regulator (CFTR) channel to enter cells. In cystic fibrosis patients, this channel is mutated, potentially preventing the bacteria from hijacking it to infect the intestines.

What are the early symptoms of typhoid fever?

The early symptoms include a stepwise fever, which shows a gradual increase in temperature over time. This occurs in the first week of infection, along with general discomfort.

What are rose spots, and when do they appear during typhoid fever?

Rose spots are small, blanchable papules (1-5 mm) that appear on the skin during the second week of typhoid fever. These spots are a characteristic symptom of the disease.

What are the potential complications in the third week of typhoid fever?

In the third week, complications include intestinal bleeding, hepatosplenomegaly (enlargement of the liver and spleen), and intestinal perforation. These are serious symptoms that require medical attention.

How is typhoid fever diagnosed?

Typhoid fever is diagnosed by suspecting it based on symptoms such as fever, abdominal pain, and GI issues, especially if the patient has been in an endemic area. Blood and stool cultures are typically used for confirmation.

What are the common treatments for typhoid fever?

The treatment depends on local resistance patterns but generally includes antibiotics like fluoroquinolones, azithromycin, ceftriaxone, or carbapenems. Severe cases might also require steroids like dexamethasone.

Outlines

00:00

🦠 Introduction to Typhoid Fever: Causes and Transmission

This paragraph introduces typhoid fever, describing its bacterial causes—Salmonella enterica serovar typhi and Salmonella paratyphi—and the different clinical presentations between the two. The terms 'typhoid fever' and 'enteric fever' are often used interchangeably. The bacteria are transmitted only between humans, either through direct contact or via contaminated food or water. Risk factors include being a child or young adult, overcrowding, and poor sanitation.

05:01

🧬 Pathogenesis: How Typhoid Bacteria Infect the Body

This section explains the pathogenesis of typhoid fever. The bacteria are ingested, survive the stomach's acidic environment, and invade the small intestine's epithelial tissue through various mechanisms. Once inside, they proliferate in lymphatic tissue, causing Peyer's patch hypertrophy, and spread throughout the body via the lymphatic and circulatory systems, leading to further complications.

10:02

🤒 Symptoms of Typhoid Fever: Fever, Rose Spots, and GI Complications

The clinical presentation of typhoid fever is detailed here. Symptoms typically appear 5 to 21 days after infection, starting with a stepwise fever in the first week. In the second week, abdominal pain and rose spots develop. The third week brings severe complications, including intestinal bleeding, hepatosplenomegaly, and intestinal perforation. Other symptoms can include diarrhea or constipation, headaches, and typhoid encephalopathy, which affects mental status.

🧪 Diagnosis and Treatment of Typhoid Fever

Diagnosis of typhoid fever involves identifying symptoms and exposure to endemic areas. Blood and stool cultures are common diagnostic tools. Treatment depends on local bacterial resistance patterns, with antibiotics like fluoroquinolones, azithromycin, and ceftriaxone used. For severe cases, steroids such as dexamethasone may be added. There is a risk of relapse, typically two to three weeks after initial recovery, influenced by the antibiotic used.

💊 Chronic Carriage and Prevention of Typhoid Fever

Some individuals may become chronic carriers of the bacteria, continuing to excrete it even after treatment. This occurs in 1-5% of cases, particularly in adult women or those with gallbladder issues like gallstones. Chronic carriers may require gallbladder removal to fully eliminate the bacteria. Prevention focuses on sanitation, hygiene, and vaccination. Famous historical cases like 'Typhoid Mary' highlight the dangers of asymptomatic carriers.

🔔 Conclusion and Call to Action

The final paragraph encourages viewers to explore more content on infectious diseases, subscribe to the channel, and turn on notifications to stay updated. The creator thanks viewers for watching and hopes to see them in future videos.

Keywords

💡Typhoid Fever

Typhoid fever is an infectious disease caused by the bacteria *Salmonella enterica* serovar Typhi. It presents with symptoms like fever, abdominal pain, and gastrointestinal issues such as diarrhea or constipation. The video explains that humans are the only reservoir for this bacteria, and transmission typically occurs through contaminated food or water.

💡Salmonella enterica serovar Typhi

*Salmonella enterica* serovar Typhi is the specific bacterium responsible for causing typhoid fever. It is a gram-negative bacteria that infects the human host through ingestion, surviving the gastric acids and penetrating the intestinal lining to spread throughout the body. The bacteria's ability to proliferate in the intestines and travel through the bloodstream leads to the symptoms associated with typhoid fever.

💡Enteric Fever

Enteric fever is a term used interchangeably with typhoid fever and includes both typhoid and paratyphoid fever. It is characterized by systemic infection with symptoms like fever, gastrointestinal issues, and in severe cases, organ enlargement and intestinal perforation. The video highlights that enteric fever is caused by both *Salmonella Typhi* and *Salmonella Paratyphi* bacteria.

💡Transmission

Transmission of typhoid fever occurs through direct or indirect contact with contaminated food or water. The bacteria spread from infected individuals to others, and overcrowded conditions or poor sanitation increase the risk of transmission. The video explains that humans are the only known reservoir for the bacteria, meaning it can only spread from person to person.

💡Stepwise Fever

Stepwise fever refers to the characteristic pattern of fever progression in typhoid fever. The fever rises in stages, with each rise plateauing before increasing again. This symptom usually appears in the first week after infection. It is one of the key indicators of typhoid fever described in the video.

💡Rose Spots

Rose spots are small, blanchable red papules (1–5 mm in size) that appear on the skin of patients with typhoid fever, typically in the second week of infection. These spots are a hallmark symptom and help in the clinical diagnosis of the disease. The video mentions these as part of the progression of typhoid symptoms.

💡Peyer's Patches

Peyer's patches are lymphoid tissue located in the small intestine that become hypertrophied (enlarged) during typhoid fever. The bacteria proliferate within these tissues, leading to inflammation and potentially causing severe symptoms like intestinal perforation. The video describes this process as part of the pathogenesis of the disease.

💡Relapse

Relapse in the context of typhoid fever refers to the recurrence of symptoms two to three weeks after the initial resolution of the fever. This can happen if the treatment was not fully effective, often due to resistance patterns in the bacteria. The video mentions relapse as a common complication that can occur even after treatment.

💡Chronic Carriage

Chronic carriage is when a person who has recovered from typhoid fever continues to harbor the bacteria and excrete it in their stool for more than 12 months. These carriers, although asymptomatic, can spread the disease to others. The video uses the historical example of Typhoid Mary, a chronic carrier who infected many people despite not showing symptoms herself.

💡Antibiotic Resistance

Antibiotic resistance refers to the ability of bacteria to resist the effects of drugs that once killed or inhibited them. In the case of typhoid fever, strains of *Salmonella Typhi* can develop resistance to multiple drugs, which makes treatment more challenging. The video mentions multi-drug resistant (MDR) and extensively drug-resistant (XDR) strains, which influence the choice of antibiotics for treatment.

Highlights

Typhoid fever is caused by a Gram-negative bacterium, Salmonella enterica serovar Typhi, or related bacterium, Salmonella Paratyphi.

Humans are the only reservoir for typhoid fever bacteria, and it is transmitted through contaminated food or water, or direct contact.

Risk factors for contracting typhoid fever include being a child or young adult, overcrowding, and poor sanitation.

Typhoid fever bacteria survive gastric acids and invade intestinal epithelium, using CFTR chloride ion channels for entry.

Patients with cystic fibrosis may be protected from typhoid fever due to mutations in the CFTR chloride ion channel.

Once inside the body, the bacteria proliferate in the submucosa, causing Peyer's patch hypertrophy and disseminating through the lymphatic and blood systems.

The clinical presentation of typhoid fever includes stepwise fever, abdominal pain, and rose spots during the first two weeks of infection.

In the third week, symptoms worsen with intestinal bleeding, hepatosplenomegaly, and possible intestinal perforation.

Both diarrhea and constipation are equally common in typhoid fever, along with headaches, disordered sleep, and typhoid encephalopathy.

Diagnosis is based on clinical suspicion, particularly in those exposed to endemic areas, and confirmed through blood, stool, or bone marrow cultures.

Treatment depends on local resistance patterns, with first-line antibiotics including fluoroquinolones, azithromycin, ceftriaxone, or carbapenems.

Relapse occurs in some patients two to three weeks after resolution of fever, often depending on the antibiotic used.

Chronic carriers, usually adult women or those with biliary diseases, can excrete the bacteria for more than 12 months after recovery.

Prevention of typhoid fever includes ensuring clean water, sanitation, hygiene, and vaccination.

Cholecystectomy is recommended for chronic carriers as bacteria often form biofilms on gallstones in the gallbladder.

Transcripts

hey everyone this lesson is on typhoid

fever in the summer type of what causes

typhoid fever all chuckle the

pathogenesis signs and symptoms

diagnosis and treatment of typhoid fever

so typhoid fever is caused by an

infection with a gram-negative bacteria

Salmonella enterica serovar typhi or

simply seminal a type ii or a related

bacteria Salmonella parrot IV which has

different subtypes a B or C both of

these bacteria cause slightly different

clinical presentations but we generally

call infections by both of these typhoid

fever there's also the term we use

enteric fever which describes both the

typhoid paratyphoid fever so we can use

typhoid fever or enteric fever

interchangeably house typhoid fever

transmitted well humans are actually the

only reservoir for this type of bacteria

so it has to come from a human to

another human

so either can this can be through direct

contact or indirect contact via

contaminated food or water now the risk

factors for contracting typhoid fever

include being a child or young adult

children and young adults are more

susceptible to typhoid fever

another one is overcrowding so you can

imagine if there's lots of people if

anybody's infected they can easily

transmit it through direct or indirect

contact and poor sanitation is also

another risk factor so again through

contaminated food water if there's poor

sanitation with regards to food or water

it's easier to transmit this so how does

Seminole at I fee and Seminole apéritif

II infect us and make us sick to cause

typhoid fever

well these bacteria are ingested orally

and they actually survive the gastric

acids and then enter into the duodenum

which is the first part of the small

intestine when they enter the duodenum

they actually can penetrate through

intestinal epithelium and invade into

lymphoid tissue and they do so by a

couple of different mechanisms one is

through an EM cell which is part of the

mucosal associated lymphoid tissue

system or mult system and the second way

that this bacteria can actually

penetrate into the epithelium is through

direct penetration into an epithelial

cell via CFTR or cystic fibrosis

transmembrane conductance regulator

which is a chloride ion channel so may

be thinking cystic fibrosis

transmembrane conductance regulator what

does this mean well this is actually the

chloride ion channel that is mutated in

patients with cystic fibrosis so

essentially what happens is the seminal

type your parrot IP

utilize or hijack this chloride ion

channel and use it to enter into

intestinal epithelial cells so what's

very interesting is that because this

channel is mutated in patients with

cystic fibrosis cystic fibrosis patients

may actually be protected against

typhoid fewer infections or infections

by the bacteria that cause typhoid fever

so again very interesting another thing

that happens is that the seminal type II

bacteria once it penetrates into the

epithelium will actually proliferate in

the submucosa causing peyer's patch

hypertrophy peyer's patch is lymphatic

tissue in the intestines that becomes

hypertrophy because the bacteria

actually proliferate s' inside to cause

that hypertrophy and eventually the

bacteria will disseminate through the

body by the lymphatic system and

hematogenous lead through the blood to

cause many of the symptoms were talked

about in the next slide

so the clinical presentation of typhoid

fever can be summed up by a fever and

abdominal pain but more specifically

with this infection there's a symptom

onset that occurs in roughly 5 to 21

days after ingestion of the bacteria

when the symptoms occur depends on the

age of the patient the health of the

patient the gastric acidity of the

patient's stomach and the number of

organisms that are ingested in the first

week of infection we have what we call a

stepwise fever this is the first symptom

you're gonna see stepwise fever is

called that because we see a gradual

step like increase in fever so you'll

see a temperature it'll bump up to a

higher level and it will Plateau and

then it'll bump up to another higher

level and plateau at that so that's why

we call it stepwise in the second week

of infection this is when we see the

abdominal pain and we also see what we

call rose spots row spots are small

usually one to five millimeters in size

Blanche able papules so you're gonna see

these on the skin of an infected

individual there Blanche evils so that

means that if you actually push on them

they will disappear but then will

reappear so those are what we call it

rose spots and in the third week you're

gonna see some of the worsening symptoms

you're gonna see intestinal bleeding so

you might see hematochezia Molina you're

also gonna get a paddle splenomegaly so

an enlargement of the liver and the

spleen and you can also see intestinal

perforation so essentially because of

all that

proliferating bacteria within the

submucosa may actually cause an

intestinal perforation other symptoms of

typhoid fever are due to the GI system

being affected so you can see diarrhea

or constipation these seem to occur with

equal frequency so about 50% of the time

you'll have diarrhea with typhoid fever

the other 50% of the time you'll have

constipation you can also see headaches

disordered sleep patterns and you can

also get what we call typhoid

encephalopathy typhoid encephalopathy

causes an altered Mental Status

confusion delirium and even acute

psychosis so how do we make the

diagnosis and how do we treat typhoid

fever diagnosis of typhoid fever is

through usually suspecting it in the

first place so you suspect the typhoid

fever if there's exposure to an endemic

area and if you have been exposed to an

area that has a lot of typhoid fever

you're gonna suspect it even more if

there's three days or more fever and GI

symptoms like the diarrhea in the

constipation and the abdominal pain we

talked about or the hepatosplenomegaly

or the intestinal bleeding and then once

you have suspected it you can do some

tests you can do blood and stool

cultures could do a bone marrow test but

that's not gonna be something that you

are gonna do and a lot of times it can

be an empiric diagnosis you're gonna see

the symptoms you're gonna see that

they've been in an endemic area they're

not vaccinated and then you're going to

say you know what this is probably a

diagnosis of typhoid fever and the

treatment of typhoid fever depends on

local resistance pattern so in some

parts of the world you're gonna have

different strains of Salmonella typhi or

perro typing there could be multi-drug

resistance or MDR strains or even

extensively drug resistant or XDR

strains of this bacteria and that's

gonna change which antibiotic you're

gonna use generally speaking the first

line of antibiotics that you're going to

use for typhoid fever include

fluoroquinolones azithromycin

ceftriaxone or carbapenems in for severe

illness you might want to add on a

steroid like dexamethasone now other

considerations of typhoid fever include

what we call relapse so a state of

relapse generally occurs two to three

weeks after resolution of the fever so

what happens is the symptoms of typhoid

fever come back after about two to three

weeks after

having resolution of the fever so this

is what we call relapse and this risk of

relapse generally depends on the

antibiotic that you used and again with

the local resistance patterns you're

gonna want to keep an eye on which

antibiotic depending on the resistance

patterns in that area another

consideration for typhoid fever includes

what we call chronic carriage chronic

carriage is what happens when you have a

person that's had typhoid fever you

given them right antibiotic they were

treated they no longer have symptoms or

asymptomatic

and it only happens in a few rare

individuals one to five percent of

patients generally speaking and what

chronic Harwich means is that they have

been treated they're a cinematic they're

feeling better but they are still

excreting the organism even for more

than twelve months and that's generally

what we call chronic carriage so they

could be an acute carrier that gets me

still excreting the organism like the

Seminole of Taif your parrot i fee even

after being treated but when they've are

still excreting the organism even more

than twelve months after the resolution

of the acute illness we call that

chronic carriage so these people could

just have this with them for a long time

the risk factors for chronic carriage

include the following includes generally

adult women biliary tract disease like

having cholelithiasis so gall stones the

reason for this is because the seminole

of bacteria hides out in the gall

bladder so if there's any gallbladder

stones in there

they generally concede in and cause a

biofilm on those gall stones to stay

there because the seminal bacteria cause

biofilms and stay within the person's

gall bladder the only way we can get rid

of them is actually to get rid of the

gall bladder so I'll call Asustek t'me

is the treatment for chronic carriers

and another consideration for typhoid

fever is prevention of typhoid fever in

the first place and this can occur

through having fresh water sanitation

and hygiene remember a lot of times this

is transmitted from contaminated waters

and there's also a vaccination for

typhoid fever so having a vaccine for

typhoid fever and having fresh water and

sanitation and hygiene can help a lot in

preventing this in the first place

so to summarize the other considerations

of typhoid fever we need to worry about

a few things

first we need to worry about relapse so

even if we've treated a patient with

typhoid

fever we might not have picked the right

antibiotic other consideration with

typhoid fever is the state of chronic

carriage and this is again an

asymptomatic state and this is where

that person or individual will excrete

seminal Atty for your parrot IV into

their environment for extended periods

of time this is what actually happened

with typhoid mary she was a chronic

carrier she wasn't symptomatic but she

was passing and excreting this organism

and infecting many other individuals and

again the risk factors for chronic

carriage include adult women and those

with biliary tract diseases especially

cholelithiasis because gallstones act as

a source of that bacteria and again the

most important thing to take from all of

this is prevention of typhoid fever in

the first place again we want to have

fresh water sanitation and hygiene that

is critical to prevent the spread of

typhoid fever in there's a vaccination

for typhoid fever that can actually

reduce or eliminate it or help prevent

individuals from contracting typhoid

fever so if you want to learn more about

other infectious diseases please check

out my infectious disease playlist and

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