so in this lecture we will cover chapter 14 streptococcal infections now with this lecture we're just going to touch

on the disease process that these infections cause and not necessarily the identification of these organisms we

will touch on that once we discuss them within microbiology now these first couple of slides do

contain some various terms that you should be familiar with so just be sure that you review them and

make sure that you are aware of what they mean so most of your streptococcia that

actually have the cell wall antigen that we'll take for landsfield group a are known as your streptococcus pyogenes now

we will talk a little bit more about that landfill grouping and the various streptococcusi and the different

organisms that are within this family once we are in micro class and so you'll understand a little bit more about what

the various things I'm discussing mean but for now we're mostly going to focus on

that disease process so with your strep pogenes it is the most common causative age agent of the

pharyngitis so this is what we refer to as strep throat and it can't cause other disorders

more specifically things that you may have heard or things like scarlet fever and impetigo

uh the most common type of bacteria that call it is um that actually causes the necrotizing fasciitis where you actually

have the death of the um the various tissues so if you have some sort of skin or deep tissue

infection it does cause that that that the necrotizing fasciitis that will destroy the tissue of the

the skin and the various layers of the skin all the way down through the muscle and sometimes it can even go into the

bone now most the time when someone has a strep hogenes infection within the

throat strep throat we typically think of it as something being fairly easy to treat you give the

patient antibiotic and they usually you know do well with it um however if a strep hyogenes infection

is left untreated there are various complications that can actually develop from it to include things like acute

rheumatic fever post streptococcal glomerulonephritis as well as some other things that it

kind of it can kind of disseminate out and cause things like sinusitis ear infections

um septic arthritis neonatal septicemia rare cases of pneumonia so really making sure that you get an early diagnosis

when someone has strep throat it's going to help to prevent any of these other complications for developing and so

that's again one of the reasons why it's very important that when you diagnose and treat an infection that you do take

all of those antibiotics just to prevent [Music] um

that organism from continue to grow and spread throughout the body it's also important to make sure that you you take

the proper antibiotic and dosage now one important thing to note about the actual streptococcus pathogenese

organism itself is kind of pretty much to understand that that outside membrane of that particular organism

does have some things on that cell wall surface so just like kind of how those antigens kind of poke through the

bacteria itself has has a similar process where it's got various components on that cell wall surface

that um allow that organism to actually adhere

to the human epithelium and will actually initiate that infectious process

now one of those that we refer to as an M antigen or an M protein now the M protein is a cell protein that

is found in association with the hyaluronic capsule and it actually is a major virulence factor for strep

hyogenes so some of the strands of strep progenies actually lack that in protein

so they can't actually cause an infection but there are some forms of it that do

actually have that in protein so you will see that infection actually take place now the um

the M protein what it will actually do is inhibit phagocytosis and antibody synthesized

um any antibody that is actually synthesized against that m-protein will actually provide a

type specific immunity to group a streptococci so basically that M protein is what's

going to kind of stimulate that immunity type of response to that organism so if it lacks it it it's not going to cause

the infection but if that M protein is there then you will have that infectious process that's going to take place

now once the infection does take place you have a group of extracellular products that will actually

help with that pathogenesis as well as the diagnosis of that disease but those antibodies are actually produced in

response to the substances that um that substances on the outside of that

cellular wall or that make up that cellular wall and so these substances will actually provide that evidence that

you have that streptococcal infection that's going on now there are two homologens that are to be noted that

will actually have the ability to damage the human and animal erythrocytes as well as the some of the leukocytes and

the platelets that's actually produced by this particular organism and so we're going

to talk about those in a little bit as well now morphologically once we actually get

into micro although this will make a whole lot more sense we did kind of touch on this in intro

strep pogenes is a gram-positive cocca they do present in in Chains so you can see an image there of that Gram stain

where you have those those chains of those cocca that are linked together um they are divided into the landsfield

group type A now the landsfield grouping we will discuss in microbiology and that's just basically a kit test where

you're looking to see which of those little um antigen type markers on the surface

of those cells are present but again we'll discuss that later but for now they do type landsfield group a now if

you've ever noticed worked in the lab or any kind of Physicians office anywhere or ever had a strep test done you may

notice on those kits that it actually says strip a we have the two kits here these are

pretty common if you've worked in the lab you may have seen these at some point and what it's actually looking for

is that landfill group a which is your strep pogenes and in addition these organisms do have that ability to

cause beta-hemolysis on the blood auger so we kind of talked about in that previous slide how these organisms have

those hemolysins in them and so as you can see on this Blood auger plates here in this image

get my writing tool here so here you see in this image where the organism is grown on this Blood auger plate so

typically you have that red color of that plate and now that organism where it's growing actually has that clearing

around it so you can see where it's actually destroyed those red cells that are in that auger plates and so you have

this little zone of hemolysis where you have a complete clearing of that hemoglobin

now on the surface wall of that organism itself so you remember if it's a cocci it's just like a little ball a little

circle on that suffer surface these organisms have structures that are called fimbri and so they will actually

arise near the plasma membrane and they will project through that cell wall and capsule and so

what will happen here is that you have those MNR antigens again and so when we talk about those and we'll see another

side here we'll kind of explain that a little bit better that M1 is the one that's going to kind

of help to stick that organism to the surface of the the human epithelial cell

so here to kind of give you a visual what we've been talking about you have a single cell strap hargines organism of

course you it's like I said it's a coxa so it's a circle or a ball and then you have that cytoplasmic membrane just that

outside layer of that organism or that cell and then you actually have a capsule around it and so within that

capsule you have all of these different things that are going to help with this organism and its ability to infect the

host and again kind of point out that M protein right here where that kind of helps with that adhesion and attachment

to to the host cells then within that sale it will actually produce various enzymes and these enzymes give that

infectious component of the hemolysis and various things like that so basically the cell structure itself

is its virulence the cell structure and makeup its ability to produce these enzymes is what AIDS it in causing the

affection infection as well as survival and destruction all right so now let's go back to those

extracellular products that are produced by this organism now the first one we're going to talk about is streptolysin O so

streptolysino is an oxygen label enzyme that will bind to the red blood cell membrane and then what it will do is

actually cause this rearrangement that takes place within that membrane that will actually in the end create holes

and then that allows that hemoglobin to seep out of those cells and then it will actually happen streptolysin o is

anagenic meaning that it will produce an antibody response within the patient and then we actually look for that antibody

response through those serological test methods now the next one we're going to talk about streptolysin s

so that one is oxygen stable it is an oxygen stable enzyme that is responsible for that beta homolysis on that blood

auger plate so we'll resolve that clearing around where that organism was growing

now what streptolysin s does is it will actually disrupt the permeability of that red blood cell membrane which will

actually cause osmotic lyses now streptolysis is not anagenic the other substances that are produced

by the group a strep or strep streptococcus pyogenes will actually facilitate the spreads of

the organism through the subcutaneous or deep soft tissue and so those we have here where you have the

Halal Andres which breaks down the hyaluronic acid that you find in the host connective tissue

um so that's where you kind of start getting that breakdown of the actual layers of the skin and getting real deep

down into those tissues you also have the um

the dnase and so there are different forms of it but what the dnase actually does is it will actually degrade the DNA

within the The Host next we have streptokinase streptocinase is an enzyme that actually

dissolves clots by converting the plasminogen to plasmin and then you have

also have a couple of other extracellular products that will elicit an antibody response like the

um and I did the in a dice the um proteinase esterase and amylase so those

will all create some sort of antibody response once that organism is present within the

body and then the last one is your erythrogenic Toxin and so what this will

do is it is elaborated by Scarlet fever-associated strands and it is actually responsible for that

characteristic rash that you will see with these types of inspections when you actually have an infection that results

in scarlet fever and just kind of briefly cap the epidemiology it is seen mostly in

children school-aged children it is spread through contact of large droplets from the upper respiratory tract so just

um you know just children being children your hands in your mouth your pencils in your mouth using the same things

drinking after each other um you know High School Middle School students tend to Once one of them gets

it they all start kind of getting it um so basically it can be spread very easily

um you know usually if it's once you get it in your household you're doing everything that you can like changing

out two toothbrushes and not drinking after each other just to kind of avoid um a transmitting that infection from

one person to the next within your household now there are several things and complications that can come from it

we're going to talk about those a little bit more things like rheumatic fever um issues with the hearts so basically

if you've got that infection that just kind of doesn't get treated and continues to spread then you're going to

start seeing other complications and so obviously those complications are going to arise from the fact that you have all

these extracellular products that are going out within your host and causing this destruction to take place

so your streptogines infections they do have a right variety of signs and symptoms that happen and that's because

they Cause A rad variety of infections you know the most common one that we are aware of are the strep throats that are

you know causes an acute pharyngitis as well as you know upper respiratory uh upper respiratory tract types of

infections now you can also have other things where again we kind of mentioned when it starts to affect the skin things

like impetigo um you know can also affect the sinus cavities kind of spread out from there

causing things like pneumonia other complications that we see are things like scarlet fever

as well as rheumatic fever affecting various organs throughout the body actually making its

way to the kidneys and causing problems within the kidneys itself so with those upper respiratory tract

infections you know it's going to be kind of presenting what typical of a respiratory infections have where you

have that inflammation in the sinuses nasal passes coughing fever vomiting unable to eat

um just an overall feeling of not feeling well um

you also with um your strep throat that you get you know within children you're going to

have that sore throat that fever you know a child's fine and then all of a sudden something's not right it just

has kind of has that rapid progression you'll start seeing it on the tonsils you might see those little specks within

the back of the throat those swollen tonsils sometimes you can actually get little

white patches on the back of the throat so it just depends on the individual patient the particular strand

as well as how it's going to present but kind of once you realize what's what's going on when you the child comes to you

with the strep throat and you open up you start seeing those red specks it's pretty good indicator that that's

probably what is happening um let's see so with infantigo you get

these little lesions that will form on the skin that will be kind of red tender swollen they can kind of progress onto

where you get that scab like appearance um and so you can see there this image where you have that irritation on on the

on this this child here it looks like a child where you've got all of this scabby crusty looking infection that's

going on around this child's nose here with the cellulitis you can see here where the infection has reached this

individual's foot and so you've got all that redness and swelling from that cellulitis from that infection

um here in this bottom one once it kind of rolls over to that rheumatic fever

you start seeing that classic rash so you see the rash on this individual here looks like on their back and then this

child here you can see that rash on the face now this can be confusing because this rash does look very familiar with

another organism that causes something called slap cheek disease um of course there is an organism that

caused that and you'll learn more about this later but you can see all of this redness that's taken place when these

cheeks so you would definitely need to go through the test process to make sure that you roll in strep throat

and treat it and of course if you got a negative on this child I would want to confirm with an actual culture or

something else on that rapid strap because you don't want to not treat a strep

infection and then it's roll over and damage the hearts or the kidneys and I have seen this happen in children before

so it's not something that you want to play around with now again if some of these conditions go

left untreated just the toxins alone that are produced from it can be very fatal so again you know you've got the

spread of the infection to go to other other sites to cause destruction as well as producing those toxins so

making sure that you properly diagnose that strep infection very early on is very very very important

all right so for a diagnosing so traditional cultures throat cultures is traditional for as far as

in the past what we've done and a lot of Physicians will still kind of go back to this method just because it's it can be

so finicky trying to detect them on any kind of Rapid kit if you don't have enough of that organism actually on that

swab when you do that kit you can get a false negative um

if you know the child is fighting or the patient come in and they just ate a big breakfast and they had something to

drink and they noticed that their throat was hurting while they were drinking their morning coffee well they've washed

all of those um you know those fresh organisms that are on that epithelial that are built up

and grew during the night they've washed them away um so the sample itself just may not get

enough organism on that swab to actually be able to be detectable so there are a lot of factors that can cause those

false negatives so what a lot of places will do is when they're collecting that rapid strap they'll get two swabs one

goes for the rapid strep test the other gets sent for culture and so they're looking on that culture to look for the

presence of this organism and do further testing in addition if there's something else that's causing that infection in

the throat then you've you can grow that that's not going to be detected on that group a strep kit

um there are some direct molecular methods that are out there now that's actually going to use the DNA probes to

detect it so these are going to be similar to like your flu tests and things like that that you might do

by those molecular test methods um looking for those toxins so we did talk about those various toxins and

those extracellular products that are produced and so looking for those in some of these various test kits or or an

example of how we use these to actually do some of that testing

so really truly there are so many ways out there now to kind of detect strep there's really no reason why some of

these things the progression of these things should be the way they are other than

patients and Physicians not recognizing signs and symptoms and getting them treated or not properly finishing

antibiotics or not recognizing when you have individuals that are carriers and things like that so these

are all things that we'll kind of talk about a little bit more once we reach micro but for now you're kind of seeing

and understanding the disease process of just this one particular organism so it kind of helps you understand the

importance of the lab and actually having some early diagnosis that early diagnosis is going to be key

to treatment and key to prevention of some of these complications that come with it

streptocoxol a toxic shock syndrome so most of you probably already heard about this at some point in your life and it

depended on your age you might remember a time frame there where the tampon boxes came with this insert that was

just loaded with information on toxic socks toxic shock syndrome so let's talk a little bit about that

and what it is to hopefully give you a little bit better understanding of what it actually does and how this process

takes place so once you actually have the streptococcus that has entered

into the patient um again we've kind of heard over the years

the use of tampons to actually introduce the strep infection to the patients

so once that strep infection is actually introduced then what's going to happen is you're going to have

um have it kind of invade and then from there it's just going to kind of spread out so it's going to invade somewhere

through some sort of injured skin cups a cut a scrape surgical wound something there's somewhere Something's Happened

that it gets introduced through the skin so through some sort of injury then from there what's going to happen

is it's going to actually start producing these pyogenic exotoxins that will cause a fever within the hose and

then from there it actually helps to start to induce Shock by lowering the threshold of those exogeneous endotoxins

so those streptococcal pyrogenic exotoxins A and B will actually be introduced to a human mononuclear seal

to synthesize not only the tumor necrosis Factor but also the intralucon 1 Beta And interleukron 6. so this is

suggesting that the tissue necrosis Factor could actually mediate the fever the shock the tissue injury that we

actually see in this patient population now in protein contributes to the invasiveness this is due to its ability

to actually impede that phagocytosis of the streptococci so it's kind of What's blocking it from actually being

destroyed then you have these other things called superantigens that will actually bind to

the alpha and beta T cell receptors and the major histability complex class II molecules and then they will actually

start to activate a percentage of those T cells and then it'll start creating the level of those cytotoxins so you can

see how this process just keeps building and building and building and then you start reaching a point where it's

actually going to produce some of those shock-like symptoms now the symptoms of the toxic shock

syndrome can include things like the shock fever rash redness and swelling of the area that's infected

um so you're basically looking for those signs of infection that inflammatory

process that's taking place the average incubation period for that organism is actually about two to three days before

you kind of start seeing or two to three days after that actual minor trauma before that organism

actually starts kind of reaching the point that it's starting to produce these symptoms so you know recognizing

those symptoms very early on is important to in order to prevent all of those

exotoxins and things from you know creating all of these symptoms that you know are basically gonna

put this patient in a predicament where um where they could ultimately die so you've really got to kind of

the positions or the clinicians have to be able to recognize these things to catch it very early on because it can go

downhill very quick so using those various serological tests to kind of confirm that the patient does

actually have that group a strep infection is going to help them when they can help

the clinician when they can actually see that there are rises in those things like the streptolysino and the dnase B

because that means that that's an active infection that's continuing to produce these things so you see in that level go

up up and up then you know that hey this this infection is really active and this patient is about to be really really

really sick so you're definitely looking for all of that to take place now there are some patients in which

there are some renal involvement that is indicated because you have the presence of that hemoglobin in the urine

as well as you've got those serum creatinine values that are are starting to increase you know that these kidneys

are having problems and so looking for other lab tests to kind of help aid in that diagnosis

um is is what you're going to need so again just because you've been work you work in one Department that does not

mean that one little thing that you might report out does not Aid in the diagnosis of a condition that another

part department might be working on um so just because the patient is getting a culture and micro doesn't mean

that you're creatinine values or are not as valid as diagnosing that culture and figuring out what organism

it is because those creatinine values are going to indicate that hey this infection is systemic and it's affecting

organs now now if a patient reaches the toxic shock syndrome State then you know

intervention immediate treatment is is crucial so making sure those patients stay hydrated with IV fluids giving them

medications to maintain blood pressure um you know just monitoring those symptoms looking for progression

treating those patients with Penicillin and beta-lactin antibiotics which we'll learn a little

bit more about that once we reach micro you know that's going to help to keep that bacteria from continuing to grow

and spread which is going to lessen those products toxins that are pre you know being produced around the clock

from more and more organisms that are replicating and just growing a number after recovery once you've kind of

started treating that infection you can start seeing issues with the skin and so sometimes the surgery may be

needed to actually clear away some of that dead stuff that dead skin and work on that wound healing from that

point on so one other organism that I do want to mention within this unit is the

streptococcus agolecti so this is Group B so pyogenes was group a in that landfill group and

this is a group b organism and so these infections can actually cause a substantial morbidity and mortality

within adults and neonates so actually about 30 percent of women can carry this organism asymptomatically in their

genital URI tract with this particular organism it does have a fatality rate of about 26

to 70 percent among men and non-pregnant women that actually have the Group B strep disease

and despite lots of measures that have been put into place to actually try to prevent this infection it does still

remain the leading cause of early onset neonatal sepsis within the United States so one of those early measures is to

actually do a screening of the pregnant mothers around 35 to 37 weeks of gestation and so what we're looking for

is to actually see if the mother has the group Group B strep colonization and so the clinician will actually take

a culture about that time to see if if that Group B strep is is growing so you may if you're already working a lab you

may have already seen this or if you've ever had a baby you might remember maybe maybe not them doing a culture swab

of the vaginal area just to check and see if the that Group B strep is present within that that female patient

now if those cultures do come back positive for group E strep then that Mom will go through an antibiotic

prophylaxis once she's there for delivery to hopefully kind of reduce the possibility

of that Group B strep being presented to that newborn during that birthing process

so again this being a strip it is a gram-positive coxon strip do usually form chains

um it causes invasive disease primarily in infants pregnants or postpartum women older adults with the highest incidence

being young the the young infants and that's just due to that exposure from the maternal aspects

so typically if you think you're dealing with a group being infection most commonly as far as you know if a patient

is septic chromic you're going to recover it from the blood sometimes spinal fluids using serological

identification identification like latex agglutination for Group B antisera is also available

doing those cultures molecular methods there are a lot of molecular methods that are out there now

rapid techniques for finding that Group B strep by using an enrichment broth and then subculture in it to look for those

organisms including DNA probes nucleic acid test amplification PCR testing

so there are a lot of things out there to kind of again try to detect this this particular

organism very early on to hopefully prevent it from being passed to the infant but occasionally you do still

have cases where um that doesn't work or maybe the mother didn't get prenatal care

and so she comes in and delivers without that prenatal care and that infant is still exposed but we do try to do

everything that we can to kind of prevent it very early on