Infection and Microbiology Flashcards
What colour is gram positive?
Purple
What colour is gram negative?
Red/pink
Give an example of gram positive cocci?
S. anginosus
Give an example of gram negative cocci?
Veillonella species
Give an example of gram positive bacilli?
Actinomyces israelii
Give an example of gram negative bacilli?
P. intermedia
Which type of bacteria does metronidazole work on?
Strict anaerobes
What is the definition of anti-microbial resistance?
When micro-organisms change/adapt in ways which render medications used to cure the infections they cause inneffective.
What is the difference between intrinsic resistance and acquired resistance?
Intrinsic is where the micro-organism comes with a naturally occuring defence against microbials/immune cells.
Aquired is where it adapts in response to microbial/immune cell exposure, via mutaion or aquisition of new DNA.
Describe hpw bacteria can develop resistence to anti-biotics?
Altering the target site of the bacteria (Example of this is S. mitis).
Developing enzymes to inactivate the anti-biotic (Example of this is prevotella species).
Decreasing the uptake of antibiotics by creating a thick wall around the bacteria (Example of this is K. pneumoniae).
What is an ESBL?
An extended spectrum beta-lactum bacteria. Produced as a result of an ‘arms race’ between bacteria and anti-biotic.
What type of anti-biotic can be used to treat ESBLs?
Carbapenems.
Explain the two mechanisms by which oral health can cause periapical infection?
Via carious lesion, involving the pulp.
Via periodontal ligament.
What is meant by the term endogenous infection?
The infection is caused by our own micro-flora.
What is the ideal microbiology specimen for a periapical infection?
Aspirated pus, swab may be contaminated with salivary flora.
Give two examples of bacteria which are present in periodontal abscesses?
Anaeobic streptocci
Prevotella intermedia
Give to examples of bacteria present in pericoronitis?
P.intermedia
S.anginosus group
(mixed oral anaerobes)
Which bacteria can be found in alveolar osteitis?
Mixed oral flora
Which predisposing factors cause an increased risk of osteomyelitis of the jaw?
Bisphosphonates
Pagets disease
Radiotherapy
Foreign bodies (implants)
Compound fractures
Diabetes
Which micro-organisms can be found in osteomyelitis of the jaw?
Anaerobic gram negative rods, and anaerobic streptococci.
S. anginosus and S. aureus.
Which micro-organisms can be found in salivary gland infections?
S. aureus and mixed anaerobes.
What is the treatment for salivary gland infection?
Drainage
Flucloxacillin and metronidazole.
What is Ludwigs Angina?
A bilateral infection of the submandibular space, potentially from odontogenic infection.
What is SOI?
Severe Odontogenic Infection.
Which type of bacteria are typically involved in sever odontogenic infection of the submandibular space (Ludwig’s Angina)?
Anaerobic gram negative bacteria.
What is SIRS?
Systemic inflamatory Response Syndrome. A precurser to sepsis. Defined by:
- Temp <36C or >38C
- Pulse 90/min
- Resp rate >20/min
- WCC <4 or >12
(^white cell count)
What is sepsis?
A life threatening organ dysfunction caused by dysregulated host immune response to infection.
What do the S, I, and R mean on a microbiology report?
S - bacteria susceptible to antibiotic
I - bacteria susceptible at increased dose
R - bacteria resistant even with increased dose
What is the anti-biotic breakpoint?
The point where even the maximum doses of anti-biotic would no longer be able to reduce culture number.
What clinical features indicate Ludwig’s Angina?
Intraorally
Raised tongue
Difficulty breathing
Difficulty swallowing
Drooling
Extraorally
Diffuse redness
Swelling bilaterally in submandibular region
Systemically
↑ heart rate
↑ respiratory rate
↑ temperature
↑ white cell count
Which spaces can lower anterior infection spread to?
Mental/submental space
Which spaces can lower posterior infection spread to?
Buccal space
Submasseteric space
Sublingual space
Submandibular space
Lateral Pharyngeal space
Which spaces can upper anterior infection spread to?
Lip
Nasolabial region
Lower eyelid
Which spaces can upper posterior teeth spread to?
Cheek
Infra-temporal region
Maxillary Antrum
Palate
What are the main methods for managing odontogenic infection?
Establishment of drainage
Removal of source
Anti-biotic therapy (if systemic)
What micro-organisms are found in periodontal samples in healthy oral tissue?
Oral steptococci, actinomyces, veillonella.
What micro-organisms are found in periodontal samples in tissues with gingivitis?
Actinomyces, P. intermedia, bacteroides.
What micro-organisms are found in periodontal samples in tissues with gingivitis?
P. gingivalis, T. forsythia, T. denticola.
What is P. gingivalis?
Keystone pathogen in periodontal disease. Gram negative, strict anaerobe.
What are the viralence factors of P. gingivalis?
- Adhereance and invasion
- Cocktail of digestive enzymes
- Endotoxin (LPS)
- Tissue toxic metabolic birpoducts
- Capsuplar polysaccharide outer membrane vesicles.
What tools does P.gingivalis have to help it adhere to surfcaes and other cells?
Fimbrillar adhesins.
How is P. gingivalis adapted to survive from a hosts cells?
Gingipains, which break down haem to produce peptides.
What can P.gingivalis do to subvert the host immune system?
- Biofilm helps
- Gingipains degrade cytokines and innate receptors
- Produce MMPs to start tissue destruction
- Tricking host immune system
What are the system implications of periodontal disease?
Increase risk of cardiovascular disease
Suggested risk of rheumatoid arthritis
Increased risk of diabetes
What is an endodontic infection?
Infection of the pulp, derived from endogenous microflora. Typical opportunistic infections.
What are the four most common micro-organisms found in an endodontic infection?
S. mutans
C. albicans
E. faecalis
Actinomyces
What is the microbial difference between primary endodontic infections and secondary endodontic infections?
Secondary infections are 9 times more likely to contain E.faecalis than primary infections.
What are the virulence factors for a micro-organism?
- Endotoxins
- Adhesins
- Collagenases
- hyaluronidase
- Immune evasion
What is E.faecalis?
A gram positive coccus, facaultive anaerobe.
Describe the mechanism by which bacteria in caries break down teeth.
A bacterial biofilm absorbs fermentable carbohydrates, and produces weak acids. This then demineralizes tooth tissue over time, leading to dental caries.
What is the progression by which caries happens?
Adhesion
Survival and Growth
Biofilm formation
Complex plaque
Acid production
Caries
What is the key pathogen thought to be involved in caries?
S. mutans, but there can be a large mixed population of bacteria contributing to caries.
What is important about understanding the caries microbiome?
It may help to predict risk.
What bacteria are associated with periodontal disease?
P. Gingivalis
A. Actinomycetemcomitans
P. Intermedia
B. Forsythus
What bacteria are associated with caries?
S. Mutans, lactobacillus species
What bacteria are associated with root canal infections?
P. Endodontalis
F. Nucleatum
What methods are there to detect a bacterial strain?
- Microbiological culture on agar medium
- Molecular detection from DNA probes and PCR
What agar plate should be used for gram positive bacteria?
Fastidious Anaerobe Agar (FAA)
What agar plate should be used for gram negative bacteria?
Fastidious Anaerobe Agar (FAA) with vancomycin
How can you identify a bacteria?
- Metronizadole disc sensitivity
- Gram stain
- Rapid API 32
What RNA gene is found in all bacteria?
16S ribosomal RNA gene. Necessary for bacteria’s survival.
How would you collect a microbiological sample from a child?
A minimally invasive saliva swab.
Why would you not isolate bacteria in a study with a large sample size?
May take too much time to differentiate diverse colonies.
What molecular sequencing methods are available to identify bacteria?
Next-gen sequencing and microbiome analysis of 16s rDNA.
What is the purpose in identifying the levels of carriage of a bacteria with regards to public health?
- Establish a baseline with data
- Inform oral health measures
- Compare with other data internationally
If you were investigating a patients gingivitis, what biological sample could you take and how would you take it?
Subgingival plaque biofilm taken with a paper point from the gingival crevice on site of inflammation.
What methods could you use to identify the culprit organism in a patient with gingivitis?
Selective agars, PCR, NGS, sensitivity testing.
Does the knowledge of what bacteria is involved change what your treatment would be clinically?
what bacteria is involved change what your treatment would be clinically?
Probably not for a dentist, may be useful in selecting which systemic anti-biotic to prescribe.
What is the cause of denture stomatitis?
Denture associated biofilm.
What micro-organisms are associated with denture stomatitis?
C. Albicans, C. Glabrata, any oral bacteria. Bacteria use candida as scaffold to stick.
What types of specimens can be taken from a patient with denture stomatitis?
Oral rinse/swab from the localised area, foam pad for imprint.
Why is it important to identify which species of candida are present in a patient with stomatitis?
G. Glabrata is resistant to azoles, so you what anti-fungal you prescribe would depend on which strain is present.
What are the systemic complications of a poorly maintained denture?
Possibility of aspiration pneumonia, and possible links to cardiovascular disease.
What microbiological sample would you take from a patient with a dental abscess and systemic infection?
Pus sample with needle aspiration.
What are the common micro-organisms found in the pus of a dental abscess?
Any oral anaerobes, s. aureus
What are some constraints when taking a pus sample?
Bacteria in question are usually obligate anaerobes, so getting them to the lab with little oxygen exposure is key. Think about packing and lab turn around time.
What are the systemic implications if a dental infection is not managed?
Spreading odontogenic infections, possibility of sepsis.
What are the signs of sepsis?
- Feeling dizzy or faint.
- A change in mental state - like confusion or disorientation.
- Diarrhoea.
- Nausea and vomiting.
- Slurred speech.
- Severe muscle pain.
- Severe breathlessness.
What are the risk factors for developing candidiasis?
Immuno-compromised
HIV infection
Central venous catheter
Dialysis
Diavetes
Trauma patient
Burn patient
Long-term corticosteroid use
What types of infection can be caused by candida?
- Perio
- Dental implants
- Denture stomatitis
- Ventilator associated pneumonia
- Osteomyelitis
- Sutures
- Endocarditis
What are some examples of erythemous candida infections?
Denture stomatitis, atrophic (HIV related)
What is an example of a pseudomembranous candida infection?
Thrush
What is an example of hyperplastic candida infection?
Candida leukoplakia.
What generalized candida infection can have oral manifestations?
Chronic mucocutaneous infection
What are some of the signs of denture stomatitis?
Inflamed mucosa
Burning sensation
Discomfort
Bad taste in mouth
What are candida?
Opportunistic pathogenic yeasts.
Give two examples of candida species?
Candida albicans, and Candida glabrata.
Which genes are key to biofilm formation for candida infection?
ADH genes.
Describe the diagnostic process of identifying a candida infection of the oral cavity?
- Collect sample (smear, oral rinse, swab, culture, foam pad, biopsy)
- Microscopy, histology, and culture (in sabouraud’s agar)
- Lab tests for germ tube formation, sugar assimilation, AF sensitivity, and typing.
What topical treatment would you use for a candida infection?
Nystatin or amphotericin B, as they are effective on all candida species.
What topical treatment would you use on pathology that could be bacterial or candida in nature?
Miconazole, as it works on most candida species but also possesses some anti-staphyloccal activity.
CHX also works on both candida and bacteria.
What candida does fluconazole work on?
Works on C albicans, which is the most common, but some resistant strains can develop. C. Krusei and C. Glabrata are naturally resistant.
What should you do if an immunocompromised patient is diagnosed with a candida infection?
Provide systemic anti-fungal (fluconazole) and topical antifungal (nystatin)/CHX.
What clinical sample would you take for investigation of an abscess?
Pus sample.
What is a typical investigative process for microbiological investigations?
Specimen, direct examination, culture, pure culture and species ID, species name established, typing/fingerprinting.
What information can gram staining tell you about a bacteria?
- Can help identify it
- Cell wall composition
- Anti-microbial sensitivity
- Virulence factors
What must be done to identify the cause of a HAI?
The causative agent must be defined and identified.
What are microbes?
Infectious agents which are not visible to the naked eye, widespread in nature and some casue human disease.
Why should a microbiology lab determine the most frequent microbes causing infections and HAI pathogens?
To assess their risk, and to create alerts for serious ones. Furthermore can determine the nature of the HAI.
What basic role should all microbiology labs perform?
Basic typing of micro-organisms, and production of routine reports for IP&C personnel.
