Diagnosis of Bacterial Infections Flashcards
True or False: fever, pain, heat, swelling, loss of function, and discharge are all pathgonomic clinical signs for a bacterial infection.
False
Non-infectious agents are capable of producing inflammation.
Not all pathogenic bacteria cause disease through induction of inflammation.
True or False: increased (or decreased with toxic changes) total WBC count w/ neutrophilia, increased fibrinogen, and hyperglobulinemia are pathognomic clinicopathological signs for a bacterial infection.
Fibrinogen = a protein produced by the liver. This protein helps stop bleeding by helping blood clots to form
False
Non-infectious conditions can result in these findings.
What is a presumptive diagnosis?
A diagnosis based on a patient’s history, signalement and clinical signs.
What is a definitive diagnosis?
etiological diagnosis
A diagnosis that is required in order to identify the causative agent of the infection or disease and potentially perform antibiotic susceptibility testing.
Susceptibility testing is used to determine which antimicrobials will inhibit the growth of the bacteria causing a specific infection
What are 2 situations during which you can make a presumptive diagnosis?
- Px is showing pathognomic clinical signs for an infection whose tx is standard
- When a client cannot afford further diagnostic testing
Uncomplicated bacterial cystitis in dogs, cat bite abscesses, and surface & superficial pyoderma in dogs are all infections that can be treated with what?
Empirical therapy
When the presumptively diagnosed infection typically responds well to a specific antibiotic/treatment
My patient’s infection is not responding to my original treatment plan. What should I do?
Pursue further diagnostics (culture sampling, swabbing, biopsy, etc.) in order to make a definitive diagnosis and target the exact cause of the infection.
My patient has a suspected infection in a diffult-to-treat site (brain, bone, joint). Why must I make a definitive diagnosis?
Because if I do not treat the specific cause of this infection, I risk inducing secondary infections and complications, which can lead to serious consequences.
E.g., neurons are uncapable of regenerating
What type of diagnostic test is appropriate for identifying the bacteria in a deep pyoderma?
Pyoderma: bacterial skin infection
Culture
What type of diagnostic test is appropriate for diagnosing Leptospirosis?
Serology
How does a smear allow for identifying bacteria?
Direct visualization of the organisms
What is a very common site that is often incorrectly sampled from?
Draining tracts
Draining tracts or fistulous tracts are tract lesions that connect with a central area or focus of inflammation to the skin’s surface
Why is it imperative to collect samples at the earliest course of disease process as possible, in both acute and chronic cases?
As an infection/disease progresses, tissue begins to necrose. This causes some of the bacteria to die, or be overgrown by saphrocytes.
If you are unable to collect a sample before the start of antimicrobial therapy, when can proceed you collect a sample?
At trough concentration of the drug (~2-5 days after the last administration)
What is the rule of thumb for collecting samples from deceased animals?
Within 4 hours of death
What is the best way to maximize the accuracy of how likely the sampled bacteria are the causative agents?
By sampling directly from the site of infection
True or False: microorganisms isolated from an infected site are often very similar to those found in the normal flora.
True
Emphasizes the importance of collecting directly from site of infection
I have determined that the site of infection is a sterile site. How must I go about collecting my sample?
In a way that avoids both contamination with nearby flora and contamination with external bacteria (e.g., table, hands, floor, etc.)
Why is it imperative to determine if strict anaerobes may be causing the infection?
Determined by site of infection (GIT lumen, mm of gums, etc.)
Because it affects how the sample is collected, transported to a lab, and cultered by the lab tech.
What is a common error when collecting a sample?
Not getting a sufficient enough volume of sample//getting a sufficient volume without contamination
Why is a swab collection the least preferred method for sampling?
Swabs collect inadequate amounts of sample; bacteria can absorb into the swab fibers –> decreased effective sample volume; samples are prone to desiccation
Identify the different types of swabs:
- Guarded (cultures in deep body cavities; e.g., uterus)
- Transport media (avoid desiccation)
- Transport media (avoid desiccation)
- Dry
- Anaerobic
What are the best collection methods for bacterial isolation?
FNA, catheterization, biopsy; ALL must be aseptically prepped
I need a sample from the cerebral spinal fluid. How should I collect it?
FNA
What are the main cons to tissue biopsy samples?
invasive and expensive
Why must different parts of the skin be sampled differently?
The surface = non-sterile, while the superficial and deep parts are sterile
What type of bacteria primarily make up the microbiome of the surface of skin and of the pinna and externical canals of the ears?
Gram (+) cocci, and yeast
What is a tracheal wash used for?
To collect bacteria from the lower respiratory tract (sterile) to evaluate for infection (pneumonia)
A mare has endometritis. What is the required sample?
Guarded uterine swab, or culture from endometrial biopsy.
Why must you evaluate a sample for suitabiltity via microscope examination prior to laboratory submission?
To identify…
1. the presence of host inflammatory response (essential) (neutrophilic inflammation)
2. the presence of a pathogen(s)
3. the predominant pathogen, if it is a mixed infection
4. any evidence of contamination (and therefore unsuitable for culture)
Why might you be able to make a definitive diagnosis when micrscopically examining your collected sample?
Simple staining methods alow for direct visualization of bacterial morphology and arrangement, heloing narrow down list of possible etiologies (i.e.,antimicrobial therapy targeted at spore-forming rods vs staphylococcus spp.)
What are the principles of transportation in order to maintain the integrity of your sample when sending off to a lab?
- Get the sample to the lab in the same state it was in when you collected it (same # and type) (prevent contamination)
- Use the approproate transport media that support survival, not growth
- Transport ASAP (the bacteria are not viable forever in these media)
- Transport in cool temperature (prevent growth; exceptions = suspected salmonella spp. or anaerobic spp.)
What is differential media like blood agar used for?
To grow a wide range of pathogens, and to grow fastidious bacteria
Fastidious bacteria: require specific nutrional requirements, and have slower growth
What is selective media like mannitol salt used for?
To inhibit the growth of some microorganisms, but allow others to grow; specifically, to allow staphylococci (gram +) to grow.
What is differential media like MacConkey agar used for?
To grow gram (-) bacteria, and differentiate between lactose-fermenting vs non-lactose-fermenting bacteria
E.g., E. coli
What is the 4-Point Rule for sterile sites?
Must always be applied when interpreting results of samples obtained from sample sites.
- Sample must be collected in an appropriate fashion, directly from the site of infection
- There must be evidence of inflammation in the sample
- Attempt to identify evidence of bacteria in the sample
- The bacteria isolated must have to opportunity to, and be capable of, causing the disease process from which the sample was collected.
True or False: If the 4-Point Rule system is upheld, then the bacteria you have isolated are likely to be clincally significant.
True
and should be addressed in your therapeutic plan(s)!
