G- & G+ Anaerobic Bacteria

Gram-negative
Anaerobic Bacteria
Chapter 18
Microbiology for Surgical Technologists
Bacteroides
Obligate anaerobes
Comprise the majority of organisms that are normal flora in the digestive tract
Mostly in the terminal ileum
Opportunistic organism
Problems occur when organism escapes from the GI tract
Infections can occur in any area of the body, usually in the form of abscesses
Can cause
Peritoneal cavity and pelvic abscesses
Bacteremia
Diarrhea in children ages 1 to 5
Diarrhea in adults with inflammatory bowel disease
They are also beneficial
Uses food supply of pathogens such as salmonellae
Anaerobic metabolism provides the energy supply needed by other enterobacterias
Ferments carbohydrates
Bacteroides fragilis
Most notable pathogen
Causes 80% of anaerobic clinical infections
Non-spore forming, and motile
Do not secrete an endotoxin
Virulence is due to it’s capsule
Resistant to phagocytosis
Promotes abscess formation
Infection occurs from trauma to the GI tract
Surgery
Perforated appendix
Perforated ulcer
Blunt or sharp trauma
Diverticulitis
Inflammatory bowel disease
During first stage of infection aerobes, such as E.coli are active causing tissue destruction
Once they have used up the oxygen, B. fragilis takes over
Abscesses are the major complication
The immune system forms a fibrous membrane to isolate the infection
This actually protects the bacteria from antibiotics
If not surgically treated the abscess will continue to grow and burst causing peritonitis
Can cause sepsis and death if not treated
Death can still occur in massive infections
Treatment
Surgical intervention with antibiotic treatment
Untreated infections have a 60% mortality rate
They are resistant to most antibiotic
Drug of choice are cefoxitin and metronidazole
Procedures can be as simple as an I&D or may require a bowel resection
Drain placement may be necessary
Fusobacterium
Highly virulent anaerobe that has 20 species
Different from Bacteriodes in that they produce an endotoxin
Can cause
Head and neck infections
Chronic sinusitis
Liver and brain abscesses
Periodontitis
Abdominal cavity infections
F. nucleatum is associated with respiratory infections
F. periodonticum is a common cause of dental abscesses
Acute necrotizing ulcerative gingivitis (ANUG) is caused by Fusobacterium mixed with spirochetes…
Also called Vincent’s angina or Vincent’s infection
It is non contagious
Causes ulcerations and necrosis of the gum tissue, leaving crater-like defectes
Symptoms include fever, bone and tissue destructions and a foul odor
Associated with poor oral hygeine, malnutrition, and overcrowded conditions
Surgical Implications
The ST must learn and practice “bowel technique” for procedures that compromise the integrity of the bowel.
Gram-Positive
Anaerobic Bacteria
Chapter 19
Microbiology for
Surgical Technologists
Clostridium Bacilli
Clostridium includes all anaerobic Gram-positive bacilli that produce endospores
Found in water, soil, sewage, and is indigenous flora in the GI tract of animals and humans
Most are harmless
Others cause tetanus, gas gangrene, and botulism
Virulence
It is a hardy and strong organism due to
Spore formation
Production of enterotoxins, neurotoxins, and other toxins
Rapidly grow in oxygen-deficient but nutritionally rich environments
Clostridium perfringens
Cause severe and life threatening gas gangrene infections
Produce four lethal toxins: alpha, beta, epsilon, and iota
Categorized as types A,B,C, and D
Type A is the cause of gas gangrene, food poisoning and soft tissue infections
Clostridium perfringens
Myonecrosis (gas gangrene)
Reported mortality of 40% to 100%
Introduced in to the tissue by traumatic injury or surgery
Examination of muscle tissue reveals necrosis and gas due to metabolic activity of the dividing bacteria
Hence the name gas gangrene
Signs and symptons include
Intense pain in infected region approx 1 week after microbes are introduced into the tissue
Extensive muscle necrosis
Shock
Renal failure
Death
Gas Gangrene
C. perfringens can cause fasciitis and a less serious cellulitis
The fasciitis invades the fascia much like gas gangrene producing the same characteristic gas, but does not involve the muscle
C. perfringens fasciitis
Clostridium perfringens
Food Poisoning
Food poisoning caused by C. perfringens is common but not as common as other types of food poisoning
Toxin is produced after the spores germinate
Produce abdominal cramps, diarrhea w/o fever, nausea, and/or vomiting
Usually resolves itself within 24 hour w/o treatment
Reheating food destroys toxin
Necrotizing enteritis
Rare infection that occurs in jejunum
Mortality rate of 50%
Causes wide spread necrosis of jejunum
Symptoms are severe abdominal pain, bloody diarrhea, shock, and peritonitis from the microbes escaping into abdomen through the necrotic tissue
Clostridium botulinum
Three types
Food borne
Wound
Infant
Food borne
Uncommon in US
Caused by ingesting canned foods that are not processed properly
In the past had a mortality rate of approx 70%
This is down to 10% due to advances in treatment
Complications include neural dysfunction escalating to respiratory failure

Symptoms include
Weakness and dizziness 1-2 day after consuming contaminated food
Blurred vision, dilated pupils
Dry mouth
Constipation
Abdominal pain
No fever is present
As the disease progresses, bilateral flaccid weakness develops
Weakness of the peripheral muscles
Death occurs due to respiratory paralysis
Respiratory paralysis is due to toxins that bind to the cholinergic nerves and blocks neurotransmitters
Of those that survive, it may take years for the nerve endings to regenerate

Wound botulism
Extremely rare
Introduced into a traumatic wound contaminated with soil, or during surgery
Incubation period is longer than food borne botulism
Symptoms similar to to food botulism only less severe
Infant
Most common form of botulism in US
From contaminated food, in particular honey
Never feed an infant under 1 year of age honey!
Symptoms include constipation and what physicians term as “failure to survive”
Progresses to “flaccid” paralysis, and respiratory failure
But the mortality rate is very low

Treatment
The #1 treatment is respiratory support
Gastric lavage
Administration of a combination of antibiotic and trivalent botulinum antitoxin
The antitoxin binds with the toxin produced by the organism preventing it from binding to cholinergic nerve endings
Prevention
Destroying the spores in the food by canning properly
Refrigeration of food to prevent spore germination
Destroy the toxin by heating food
Clostridium tetani
Easily identified by its spore’s shape
Rounded on the end of the cell with a rod
Looks like a drum stick
The organism is widespread and found in the soil and colonizes in the GI tract of humans and animals
Anaerobic
Does not tolerate any amount of oxygen
Sporulates very rapidly to survive nature
Rare in the US due to the development of the vaccine
Most are familiar with the vaccine, it is given any time someone steps on a rusty nail, or gets some type of penetrating injury with a dirty item
More prevalent in under developed countries where the vaccine is not readily available
Mortality rate can be high
With many deaths occurring in neonates
Produces two toxins
Tetanospasmin and tetanolysin
Tetanospasmin
Produces the primary clinical symptoms
Released at cell lysis
Tetanospasmin (continued)
Blocks neurotransmitters causing spastic paralysis
Does not bind to the cholinergic nerve endings, instead binds to axonal terminals
It is irreversible and recovery depends on the regeneration of the axons
Diseases
Most common form is generalized tetanus
Trismus is commonly known as lock jaw
Effect the masseter muscles
The characteristic “smile” is the result of the contracture of these muscles called risus sardonicus
Other signs are sweating, restlessness, and chronic back spasm called opisthotonos, that can fracture the spine
A less severe form is localized tetanus
Infection remains localized to the muscles at the site of infection
A life threatening form is cephalic tetanus, infects the head and prognosis for this is very poor
Tetanus neonatorum (neonatal tetanus)
A deadly infection of the umbilical stump
Almost 100% fatal
Survivors have developmental complications
Surgical Implications
Gas gangrene and fasciitis must be aggressively treated with antibiotics in combination with surgical debridement (I&D)
The ST should be prepared with proper instrumentation and the wound is usually irrigated with an antibiotic solution
Sometimes referred to as TAB, DAB or “bug juice”
Anatomy of a Nerve
Discussion
A patient presents with abdominal pain. Upon examination and completion of diagnostic testing, it is discovered that he has a Bacteroides fragilis infection with an intra-abdominal abscess. How should this patient be treated?

You never really lose until you quit trying.
Mike Ditka