Fundamentals II 10-11:00Scribe: Jennifer Grimes

Wednesday, October 28, 2009Proof: Kristina Hixson

Dr. MoserAnaerobic BacteriaPage1 of 7

Introduction [S1]:
I’m going to talk about anaerobic bacteriology and some of the clinical syndromes. This is mostly a dental issue. Our mouths are full of anaerobes that we’ll talk about (normal flora distribution).
For the most part, they are opportunistic organisms. If you give them a chance, they will cause infections.
Reading Assignment [S2]
Somehow, I got chapter 38 in there, it is supposed to be chapter 40. These are some of the chapters that relate to anaerobes plus chapter 9 is a general one about normal flora, which includes anaerobes. I suggest you look at these if you haven’t used this book. It’s very concise; has a lot of boxes with important information that summarize things for you.
Categories Based Upon Gaseous Requirements [S3]
First of all, many of the bacteria that you have probably discussed to date are Facultative organisms.
Facultative bacteria can grow with or without oxygen. Those are enterobacteria, staph aureus, streptococci, so these are the majority of organisms that we have discussed.
There is a spectrum for those that require oxygen and those that cannot grow in the presence of oxygen. In between there, there are a number of things. There are different requirements.
Some require oxygen in reduced quantity (can’t take atmospheric oxygen). Some require increased carbon dioxide, so they will be happy when global warming happens.
There’s a spectrum among anaerobic bacteria. Some are aerotolerant such as the bacteria on your skin (proprionibacteria, which is considered an anaerobe but is really aerotolerant).
Some examples here: some of Carbon Dioxide, some of the Neiserria and haemophilous, and campylobacter fall in this category of reduced oxygen.
So there are examples of organisms that we are interested in, and many of them that we will be interested in will be facultative organisms.
Physiology and Growth Conditions [S4]
So why are they anaerobes?
There are a couple things that they need, both pH and oxidation-reduction potential. They lack certain things like cytochrome systems. Most lack superoxide dismutase and catalase, so what these are for is to detoxify the toxic byproducts of oxygen metabolism. You get a lot of high energy oxygen radicals produced, and you have to neutralize those, so that is what those things do.
Obligate anaerobes, they don’t have any of this.
Aerotolerant anaerobes produce some of these but in small quantities. As far as facultative, their machinery will work equally well with or without oxygen, so they have a full complement of these enzymes.
It is really a matter of what enzymes they have and their ability to detoxify these.
Anaerobic Bacteria Diagram [S5]
This is a cartoon to demonstrate this. Their ability to detoxify these byproducts of oxygen metabolism.
So, here you have metabolism and you have all these high energy radicals and hydrogen peroxide, and if you don’t have these particular things present, bacteria will die. Otherwise, they’re harmless as molecular oxygen and water.
This is the difference between organisms that are obligate anaerobes and then you get put in between aerotolerant that have some of these enzymes, but they don’t produce them at enough quantity to be considered true facultative organisms.
Oxidation – Reduction Potential and Anatomic Site [S6]
What drives where they live?
There are 2 categories of anaerobes: normal flora (many infections from anaerobes are from your own organisms that you already have) and environmental organisms (classical examples like clostridial disease that we’ll also talk about).
There are both environmental and endogenous examples. Those that live with us live down in this region (negative millivolts). In other words, they have to be on the negative side of this redox potential. That includes the plaque, colon, that sort of thing. You’re not going to find them in highly oxygenated areas of the body. In fact, sometimes from a therapeutic standpoint, although this is not universally accepted, hyperbaric chambers, which increase your oxygen content of the tissues, are sometimes used to treat these kinds of infections.
Anaerobic Bacteria of Clinical Importance [S7]
This is just a way of organizing these. These are the major organisms. Like all bacteria, they are primarily classified by their shape and their gram reaction. Very few are cocci in the anaerobes. They do exist, but the majority is either in the gram positive rods or gram negative rods.
If you look over here where they live normally, we are all carrying these around.
Some of them are fairly unique (only found in certain areas, such as proprionic bacteria from the skin, also found in the GI tract, and the vagina, mouth, etc.).
You’re teeming with anaerobes. When we do a fecal culture, we look for salmonella and other facultative organisms. Those are only 0.1% of the microbial flora of the stool. The rest are these guys. Normally, with one exception, they don’t cause infectious problems in the colon.
So for the most part, we just carry them around and there are no problems associated with that.
Diagram [S8]
However, if they get loose or the host itself is modified, you can end up with a brain abscess, and there are a whole host of dental infections and abscesses because they’re really abundant in the oral cavity. People who have aspiration pneumonia, the classic thing there is alcoholic passes out, aspirates, and what you get is oral flora in the lungs, a lot of debris from foreign objects, food, that sort of stuff, and they can set up housekeeping in the lungs. Aspiration pneumonia is often caused by a mixture of organisms.
A lot of this is surgically caused, such as appendicitis. If the appendix bursts, obviously there are a lot of bacteria.
They also play a role in diabetics such as decubitis and foot ulcers due to poor circulation in that area.
Human bites are bad, sometimes worse than animal bites. A bite can cause cellulitis. We carry them in our oral cavity, GI tract, skin, and if given the opportunity, they can cause a whole host of problems.
Vincent Angina [S9]
This shows cooperation and synergism. It may be a little hard to tell from the back, but these are all gram negative organisms from this plaque right here. Some are very thin and curved, and some are long and pointed, short and fat. This is a group of organisms that if they are allowed to propagate up to large numbers, they can cause tissue destruction of the gums called Vincent Angina.
This is a result of poor oral hygiene. You are allowing this to progress to this point.
This also points out that most anaerobic infections are not a single organism; they are mixed (all the players may not have an equal responsibility in pathology, but in general because of the source they come from, you might suspect that there would be multiple organisms present).
Adult Periodontitis [S10]
This is the same idea, but this is in a different family of infections. This is not acute like the previous slide. This happens to be a chronic condition: adult periodontitis. This is a continuing of the receding of the gums, and if you culture up here in the gums, you would find certain anaerobic bacteria predominantly.
Anaerobic Brain Abscess [S11]
They can form an abscess, and this is not just exclusive to the brain. This does not have a good outcome.
You should appreciate that the bacteria aren’t all the same shape. All of these cells are polynucleosides, so we have a lot of gram positive organisms, some coccal, some rods, some gram negatives, again emphasizing the fact thatanaerobic infections are usually mixed (not usually the same organism). So if you see a gram stain like this from an abscess, you would definitely know that anaerobic bacteria are present and you would select antimicrobial therapy.
Anaerobic Polymicrobic Cellulitis [S12]
This is what would happen in a diabetic. This is a polymicrobial infection. You have lesion here that is contaminated probably with fecal material, and you have devitalized tissue. Once you have devitalized tissue, microorganisms love that, not just anaerobes. Bacteria will use this as a foothold and will expand and cause further problems. If you have this in a person who has poor circulation whose neutrophils are not functioning quite right like a diabetic, then you would experience this. Most of us in this room would not experience this.
Anaerobic Infections Gram-negative Bacilli [S13]
One of the major groups of organisms: Bacteroides, Prevotella, and Porphyromonas.
These are the gram negative bacilli that are anaerobic. Any time you hear gram negative, you don’t have spores. Spores are only made by gram-positive rods, one being an aerobe (bacillus) and one being and anaerobe (clostridius). These are distributed as normal flora throughout. There are a couple that are more important than others. Even though we have mixed infections, bacteria such as Bacteroides fragilis and Prevotella melaninogenica are common to most infections for anaerobes.
When you have an infection below the diaphragm, the fragilis group is involved. When you have an infection above the diaphragm, the melaninogenica group is involved. Others have a particular niche in which you find them. The female genital tract has these 2 other species are found.
That doesn’t mean they are all causing disease; that is just where they colonize and exist. If they do cause disease, the common thing is abscess formation and polymicrobic (mixed) infection.
They also have facultative species especially when you get into the abdominal cavity. When you have a breech like appendicitis or surgery, you have a spill of intestinal contents where you have facultative organisms as well. So you can have E.coli mixed in with anaerobes.
Necrotizing Fasciitis, Bacteroides fragilis [S14]
Sometimes knowing just where the problem is might give you an idea of what the infection is caused by. This is not common, but it can cause Necrotizing Fasciitis, which is more commonly associated with streptococcal disease.
This is obviously a nasty disease, and these organisms have to be introduced into the system (cannot cross the skin). These can happen in people that have been in car accidents or some other type of trauma like compound fractures and then have exposure to environmental (possibly from soil).
Necrotizing Fasciitis, Bacteroides fragilis [S15]
The way you treat this is that you have to get rid of the dead tissue. You can see this area down here is all dead, so this individual must be taken back to the OR to get rid of this tissue in order to get rid of the infection. They will leave them laid open for the oxygen exposure.
The bacteroides is an important group, especially Bacteroides fragilis (most important member of that group since it is the most common one found in infections).
Anaerobic infections Gram-negative Bacilli [S16]
There is also this fusobacterium. When I showed you that Vincent Angina, there are these long pointed rods; those are fusobacterium. There was also bacteroides species, and the little curvy thing is treponine (normal flora). You might think hmmm…syphilis, but that is not the case. This is why you cannot scrape an ulcer in the mouth and do a dark field examination thinking you can diagnose syphilis because there are normal treponines in the mouth.
So this group again is somewhat pleomorphic; in fact that is a characteristic on anaerobes. You can take a single colony and they won’t be the same organisms like those nice cocci you’d see in staph or strep. They can vary in shape.
Present in the upper and lower respiratory tract and they are associated with very severe disease.
These can cause Lemierre’s syndrome, which can result in jugular vein thrombosis and death. It dissects down the back and around the jugular vein. This is considered a medical emergency.
So some of these are fairly mild infections, abscess forming that you can just drain and probably get rid of.
Pulmonary Abscess [S17]
What you’ll get often is a big abscess with air pockets.
Fusobacterium [S18]
If you were to stick a needle in that and culture it, and let’s say you only find fusobacterium, this is what you would see. There’s nothing distinctive about these colonies other than the fact that they are obligate anaerobes.
You can plate them, and once you isolate them anaerobically you plate them aerobically to see if they don’t grow. That’s why you’ll see that in culture results from anaerobic cultures; normally from facultative organisms you’ll get your results in 24-48 hours. We’re talking now 48-72 hours or even longer because of the complexity of the number of organisms and how you have to deal with them and prove that they’re anaerobes.
Anaerobic Infections Gram-positive Bacilli [S19]
Other gram positive bacilli. This is sort of classic. Actinomycese is the most common, but there are other species.
These are really slow-growing, branching gram-positive rods. These include normal flora of the oral cavity and probably the GI tract. They do cause extensive tissue damage. If they get established as an abscessed tooth or aspiration pneumonia or a consequence of abdominal surgery, they are unique in that when they do cause infection, they don’t stay isolated; they move to different tissues (it would be on the jaw if it was from a tooth, the chest if it was from a lung, etc). They cause a lot of damage based on that fact.
What you will see from those draining sinus tracts, you will see “sulfur granules” since they are yellow. They are very small (1-2 mm) concretions. They are composed of nucleus of the organism (microcolony) and the host materials are coated around it.
So you can find these, crush them, and do a gram stain and diagnose them from that.
There is an associate with the copper coil IUD’s that colonize, not so much infect, the tissue.
Dacryocystitis [S20]
I show this because there are still children who don’t get the haemophilis influenza B vaccine.
Children who have haemophilis infections can look like this. Actinomyces make bacilloconcretions, and these block the lacrimal glands and you get swelling like this. Treatment is simply to manipulate it and to get that stone out of there.
Today, most children are getting these vaccines (however coverage by a vaccine is not 100%). You’ll find people who don’t have access to health care or who can’t afford it, who for one reason or another are afraid of ingredients in the vaccine or have religious reasons against getting them.
Actinomycosis “Lumpy Jaw” [S21]
This is a classic disease.
Don’t get confused, even though it is named –mycosis (usually indicates fungal); it is not a fungal infection.
When they first saw it, they thought it was fungal due to its morphology. It is actually a bacterial gram-positive branching rod infection. It causes this lumpy jaw appearance. This gentleman is asymmetric. You see how swollen he is over here.

Actinomycosis [S22]
This is not him, but it is the same process. You have an abscess in the molar here, and you can see that there is destruction of the bone and the root. If you leave this alone, it does this (comes out; wants to make a draining sinus tract). Now they’ve opened it up, and this is pus here. You put gauze over it to absorb the liquid, and you can actually find sulfur granules present and you would crush them to do an examination.
“Sulfur” Granules [S23]
If you do that, this is what it looks like here. They are just barely visible (1-2mm). If you crush it and do a gram stain, this is what it looks like under high power. They are thin, branching, gram positive rods. In the absence of the sulfur granules or any other information, there are really 2 bacteria that look like this in a gram stain. One is a nocardia, which is closely related to the mycobacteria. It is a strict aerobe. The other is actinomyces & are strict anaerobes. It is pretty easy to distinguish between the two, but upon primary isolation without the draining sinus or other information, you could not tell the difference.
Actinomyces israelii [S24]
This is a close look. The colonies are slow-growing. In fact, the laboratory needs to be told that you want to include that in detection because it may take 5 days to grow. If it is exposed to oxygen early on, the culture will die. You have to leave it in an anaerobic environment for 3-5 days before examination. This is why they thought it was a fungus. If you look at fungi, these look like hyphae, but these are bacterial size.