QUALITY CONTROL IN MEDICAL MICROBIOLOGY Quality control is divided Internal quality control: performed locally inside External quality control: performed between district labs. in same country or worldwide.

Discussing quality control programs

Areas of Quality Specimen collection & Culture Sensitivity Stains & Reporting & recording results.

Culture media

Control of Sample Collection & Define the correct specimen to The best time to Aseptic method for Best methods of storage and How to handle specimens in lab., e.g. blood cultures, CSF, urine, swabs, stool, wet slide preparations.

Sample Collection

Control of Culture Perform correct pH testing, correct storage, and correct Standard control species are used for test performance of No moisture to enter powder Caps are replaced quickly & Store plates at 4 °C in plastic Before use, dry surface of plates.

Correct autoclaving

@ Do not leave unused plates on bench overnight to avoid Slope media & fluid media may be stored at room temp. if New batches of media are dated and stored separate from old Shelf-life of each medium is Small batches of media are prepared to avoid waste.

Media ready for incubation

Trouble-Shooting for Defective media: * Use good quality Incorrect weighing: * Check and correct the Deteriorated media: *Store media in airtight containers at the appropriate Bad water : * Use distilled water for media preparation.

Use good quality media

@ Undissolved media: * Dissolve powder by mixing & Overheating of media after autoclaving: * Open autoclave when pressure comes down & temperature is below 100°C * Cool media immediately after Incorrect pH of medium: * Measure pH when medium cools to room temp. * Pour a sample of medium in a beaker, let agar to solidify around the electrode, and read pH.

pH meter

Antimicrobial Susceptibility Tests Control cultures : S. aureus ATCC (miscellaneous) E. coli ATCC (urine) P. aeruginosa ATCC Subcultured weekly & stored in To detect inhibitors in MH agar, inoculate E.faecalis (ATCC 29212),put co-trimoxazole disc and inhibition zone must be ≥ 20 mm

Antimicrobial Susceptibility Te sts

Sources of Error in Sensitivity Testing (1) Too small control zones: Due Use of discs with low Use of discs after expiry Use of a too dense Use of too thick medium Presence of inhibitors MH agar medium

Too small zones

(2) Too large control zones: Due Use of discs with high Use of a too diluted Use of a too thin medium layer (3) Presence of colonies within inhibition zones: Due Contamination of culture (large Presence of inhibitors in MH agar (small colonies) detected by co-trimoxazole

Too large zones

Control of stains & reagents A control smear is stained to check quality of newly-made Control smears of gram stain is made from a mixed culture of Staph & Control smears are kept in lab. to check Z.N, Leishman, spore stains, Control smears should be alcohol-fixed

Control smears of Gram stain

Control of Regular servicing & Check glassware for good Inspect tube caps and worn Regular check of working Check water of water-bath, Use of indicators to check autoclaves, anaerobic jar, Check distilled water.

Regular check of incubator working temp

Control of Printed forms or computer sheets must be used for reporting Result must be typed clearly and checked by a senior lab. Copies of all results are kept in Dates, demographical data, type of specimen & technologist name must be included.

Typing laboratory res ults