Bacteriology 13- strict anaerobes Flashcards
Clinical case: Buddy Plott dog came for
Dyspnea
Anorexia
Collapse
PLEURAL EFFUSION
Using VINDICATE:
I= chylothorax
N= Lymphosarcoma, hemangiosarcoma
T= trauma, lung torsion
Bacterial pleuritis:
-E.coli/kelbsiella
-ancitnbacillus
-paseurella multicoda
Diagnostic test for the Plott hound who seems to have a pleural effusion would be?
CBC/Chem
-mod. leucocytosis, Left shift and tox changes to the PMNs; mod. thrombocytopenia
-decrease in GLucose– increase liver enzymes and BUN/creatine
-hypotensice
Thoracocentesis
Cytology of Pleural Fluid
-lysed PMNs, some RBS
-Many different kind of bacteria
Culture of Pleural Fluid
-NO normal flora
-culture both aerobically and anaerobically
–> yo found bacteria in both
In buddy’s case you would culture all bacteria?
NO
You diagnosis for Buddy is Pleuritis why?
Mixed bacterial infection incl. anaerobes
Why was buddy hypotensive and had hematological &biochemical changes?
Endotoximia
-vasodilation, vascular damage, thrombosis, and consumptive coagulopathy (DIC) resulting in organ disfunction
DIC=low platelets
What is an obligate anaerobes?
BActeria that does NOT like oxygen ( or not in high quantities)– but most oxygen is LETHAL to the them
Anaerobic bacteria require the Eh (oxidation-reduction potential to be less than -100mV
In normal (oxygenated) tissue the Eh is positive
In necrotic tissue (e.g., abscesses, areas of trauma etc) the Eh is often -250mV to –150mV and therefore favors the growth of anaerobes
Areas where there is a low pH are also usually anaerobic
Describe the NSF Anaerobes?
Large group of morphologically diverse bacteria
Some are Gram-
others are Gram +
Some are cocci, rods, branching rods
Where do NSF come from?
Normal flora:
skin
mucus membrane: URT, GIT, LGT
major shareholders within the normal flora
they outnumber the facultative anaerobes 5:1 on mucocutaneous surfaces
How do anaerobes grow in areas
where oxygen is present?
vary in oxygen tolerance
ecological niche
presence of physical factors e.g., mucus, tartar, skin folds
synergy with aerobes and facultative anaerobes
What is the role of the normal
flora?
Normal flora (including anaerobes) play
an important role in maintaining our
health
Act as “security bouncers” by limiting
attachment and growth of dangerous
newcomers (other bacteria!)
so problems if you get rid of them!
BUT - they can take their job too
seriously by:
overgrowing
moving out of their usual location into
nearby sterile areas
What needs to happen for disease to
occur with the NSF Anaerobes?
NSF anaerobes infection are always ____________
OPPOTUNISTIC
What factors predispose to the infections?
Breakdown of normal host defences
- e.g., penetrating F.B.
Change in association between normal flora
Overgrowth of some bacteria
Poor blood supply and tissue necrosis
Trauma, tumors, GI obstruction or stasis, hypotension
Decreased host resistance
- e.g., chemotherapy, disease (Cushing’s),
immunodeficient (e.g., FIV +)
Prior use of antibiotics
-especially narrow spectrum; directed at
aerobic
Overwhelming contamination of
normally sterile area
-e.g., aspiration pneumonia, GIT rupture causing peritonitis
Current infection with aerobes/facultative anaerobes
-Create sufficient tissue damage to allow
anaerobes to invade
Where do NSFAs cause Disease?
At/near sites where these bacteria are part of the normal flora –> they gain access in these areas
- Do they survive if it is HEALTHY, NORMAL TISSUES???
AND these sites have necrotic tissue
- these niches protect them from oxygen and provides them with nutrients
- e.g., abscesses, areas of trauma, periodontal pockets, necrotic bite wounds, necrotic lung etc., etc
How do NSF produce disease? (virulence
factors)
Tolerance of oxygen in more virulent species
of bacteria
Extracellular or cell bound enzymes
Endotoxin (gram -)
Capsule
Synergy between community members
Work as a TEAM to produce disease
When should I suspect anaerobes as
the culprits of disease?
Foul smell***
Production of gas***
Black discolouration at the site***
Location of infection
- Near where they live
History e.g. Bites wound
Mixed/filamentous organisms on smear
Failure to culture
Cat fight abscess?
MOST common infectious diseases
Organisms (normal flora of the mouth) are
inoculated into a traumatized area (bite wound = has necrosis)’
cat bites close and so don’t allow aeration and
drainage
Both facultative anaerobes and strict anaerobes (NSFA) there
FA multiply first then when O2 runs out (~2 days) NSFA go wild
Important principle: NSFA are involved 2° and
LATER in the disease process (can “date” an
infection by presence of NSFAs)!
What are the other diseases that NFA infection cause?
Periodontal diseae
-many species
-2º to other disease
-can progress root abscesses
Pleuropneumonia/pyothorax
Pyometra
Peritonitis
What are some examples of diseases they RARELY cause (NSF)
Otitis externa
Cystitis
Superficial
Pyoderma
Endometritis
in horses
but can be involved
in PYOMETRA in dogs
How do you diagnosis infections
Collect sample into
blood culture bottle
place into vacutainer
ALWAYS MAKE A SMEAR AT THE TIME
don NOT refridgerate
submit within 6 hours
How do you treat infections?
General:
Drainage of any fluid
Debridement of necrotic tissue
–>MUST DO OR DON’T BOTH WITH ANTIBIOTICS
Copious lavage
Empirical principles
-commonly used
- metronidazole
- clindamicin (NOT horse)
- penicillin + beta-lactamase inhibitor
-do NOT use aminoglycosides or old generation quiolones
-Need to also address FA bacteria
Nursing support as needed
