Role of Microbiology Lab Flashcards
What are the two important functions of microbiology labs?
Clinical- diagnosis of infection in an individual patient for everyday management of infections
Epidemiological- support for infection prevention and control in searching for source and route of transmission of HAI.
What are the 6 minimal requirements for microbiology services?
1- set up inside the facility (if not possible, negotiate a contract for diagnostic microbiology with the nearest lab)
2- available every day including Sundays and holidays (ideally on a 24 hour basis)
3- able to examine blood, CSF, urine, stool, wound exudate or swab, respiratory secretions, and perform basic seriological tests (HIV, HBV and HCV)
4- identify common bacteria and fungi to species level
5- perform susceptibility testing using disc-diffusion methodology
6- perform basic phenotyping (serotyping and biotyping).
What species can you serotype for?
Salmonellae, Shigellae, P. aeruginosa, N. meningitidis.
What species can you biotype for?
S. typhi.
What is the zone of inhibition?
The Zone of inhibition is a circular area around the spot of the antibiotic in which the bacteria colonies do not grow. … The zone of inhibition can be used to measure the susceptibility of the bacteria to wards the antibiotic.
What are the 3 classical bacteriological methods?
Direct smear
Culture
Antigen detection.
What are the 4 roles of diagnosing infection?
Classical bacteriological methods
Sensitivity testing
Antibody detection
Molecular methods.
What is a positive and negative of antibody testing?
Not very useful in the early stages of infection
It is good at deciding what type of organism is present.
What is the simplified scheme for bacterial identification?
Specimen…Direct examination…Culture…Pure culture and identification to species…Species name established…Typing or fingerprinting for taxonomic or epidemiological purposes.
What are the 4 different types of cocci?
Single coccus
Pair of cocci
Cluster of cocci
Chains of cocci.
What are the different types of rods?
Single rod
Chain of rods
Curved rod
Spiral.
What is the shape of strep mutans?
Chains of cocci.
Do gram negative or gram positive bacteria have a thick peptidoglycan cell wall?
Gram positive.
What are the six stages of the gram stain?
1- prepare a heat fixed film of bacteria on a glass slide
2- stain with crystal violet for one minute and rinse with water
3- treat with Gram’s iodine for one minute and rinse with water
4- briefly decolourise with acetone or ethanol (a few seconds depending on thickness of film)
5- counter stain with basic fuchsin or safranin (pink dye) for one minute and rinse with water
6- blot dry and view under oil immersion.
What does gram staining tell us?
Cell wall composition.
What are the four roles in prevention and control of HAI’s?
1- outbreak investigation
2- surveillance of HAIs
3- alert microorganisms reports
4- designing antibiotic policy.
What are the two main aims of an outbreak investigation?
To determine the cause of a single-source outbreak the causative agent must be defined
Then microbiology laboratory determines if two or more isolated strains are same of different.
What microbiological tests may be added during an outbreak?
Blood products Environmental surfaces Disinfectants and antiseptics Air Water Hands of personnel Anterior nares of personnel.
What happens during HAI surveillance?
The microbiology lab should produce routine reports of bacterial isolates
A baseline incidence can be established
If the lab is computerised, these data can be made readily available.
REMEMBER TO RESERVE ANTIBIOTICS ONLY IF PATHOGEN IS RESISTANT TO FIRST LINE ANTIBIOTICS!
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What is the role of clinical microbiologist/ID specialist?
Provide leadership to antimicrobial team
Antibiotic ward rounds
Interpretation of patient specific data to optimise treatment
Active surveillance/awareness (screening for carriage of resistant bacteria and molecular detection and typing).
What are the chain of infection steps?
Infectious agent Reservoir Portal of exit Mode of transmission Portal of entry Susceptible host.
Remember: the lab should perform basic typing of microorganisms, should produce routine reports for IP&C personnel, they should interpret microbiological findings for IP&C personnel and act together with clinical and nursing colleagues in prevention of HAI.
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What are the four types of media?
Enrichment
Selective
Solid
Liquid.
What are examples of molecular techniques?
DNA hybridisation
Nucleic acid amplification testing (PCR, LCR, real time PCr and automated DNA amplification).
What are some examples of typing methods?
Phage Serology Bacteriocin Endonuclease digestion Multiocus sequence typing Whole genome sequence.
What are some examples of serological techniques?
Agglutination Precipitation Complement fixation Virus neutralisation ELISA Radioimmunoassay Immunofluorescence.
Where do scientists get infectious disease morbidity and mortality data come from?
Statutory notification Microbiology lab reports Death certificate GP surveillance schemes Hospital infection reports Specific reporting schemes.
How can you break the chain of infection?
Contact tracing Isolation Early treatment Vaccination Antibiotic prophylaxis (e.g. meningitis First aid Handwashing Treatment of underlying disease Education Sanitisation/disinfection.
What are some solutions to break the chain of infection to apply in a hospital?
Ward design Isolation facilities Maintenance of air-conditioning and ventilation Hospital design Adequate space Isolation facilities Infection control policies Staff education Good clinical practice Sterile supplies Disinfection policy Equipment sterilisation Single-use items.
