Maximum numbers of air microorganisms allowable in health care facilities
Date__________________
CLASS 14
Topic: Ecology of the microorganisms. Sanitary microbiology.
Questions to be discussed:
1. Sanitary bacteriological analysis. Indicator microorganisms (IMO). Criteria suggested for indicator microorganisms.
2. Microflora of water. Water as a factor of infectious agents spread.
3. Microbiological control of water: total microbial number; coliforms number, and thermotolerant coliforms number. Sanitary criteria for drinking water quality control.
4. Microflora of air. Pathogenic microorganisms that are spread via air.
Practical tasks:
Calculate total microbial number in given tap water samples by plate counting of colony formation units (CFU/ml) and evaluate the quality of water.
Number of colonies on the surface and in the depth of agar medium inoculated with 1ml of tap water –
Plate № 1 _______________________________________________
Plate № 2 _______________________________________________
Total microbial number ________________________________ CFU/ml
Conclusion: ___________________________________________________
__________________________________________________________________
2. Determine coliforms number, and thermotolerant coliforms number in given tap water samples examined by the multi-tube fermentation test.
- Read the results of lactose broths (Kessler’s medium) inoculation with falling quantities of tap water and incubated 2 days at 370C.
- Compare experimental results with those from the table 2. Make a conclusion concerning quality of the examined tap water.
Table 1
Criteria for drinking water quality evaluation
| Indexes | Units | Allowable standard |
| Total microbial number | CFU in 1 ml | <50 |
| Coliforms number | Number in 100 ml | Absence |
| Thermotolerant coliforms number | Number in 100 ml | Absence |
| Coliphages | PFU in 100 ml | Absence |
| Spores of Clostridia | Number in 20 ml | Absence |
Conclusion: __________________________________________________
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3. Determine coliforms number, and thermotolerant coliforms in given water samples examined by the membrane filtration test.
- Read the results of Endo medium inoculation with the bacteria from100 ml of water samples trapped in membrane filters and incubation for 24 hours at 370C. Coliforms as lactose fermenters will form red colonies, which can be easily count. Fill in Table 2 with the results and make conclusion about the quality of tested water samples.
Table 2
Results of tap water samples examination by the membrane filtration test.
| № | Volume of water | Number of lactose- positive colonies | Coliforms number | Conclusion |
| 1. | ||||
| 2. | ||||
| 3. |
4. Calculate the total microbial number in 1m3 of classroom air, examined by sedimentation method.
- Determine the total amount of colonies in 1m3 of classroom , that can be calculated using formula:
A x 100 1000
X= 80 x 10 ; where
X – number of microbes in 1 m3 of air (CFU/m3 );
A – number of growing colonies on petri dish;
80 cm2 – surface of petri dish;
(It was shown that the number of bacteria equivalent to that in 10 L (10 dm3) of air sediments on the 100 cm2 agar surface during 5 minutes of incubation).
Note that 1m3 of air is equal to 1000L.
Conclusion: ______________________________________________
Table 1.
Maximum numbers of air microorganisms allowable in health care facilities
| Reception room | Total microbial number | <1500 CFU/1m3 | Absence of coliforms, Candida, pathogenic organisms | |
| Operating room before operation | Staphylococcus aureus | Absence in 1m3 | ||
| Total microbial number | <100 CFU/1m3 | |||
| Operating room after operation
| Staphylococcus aureus | Absence in 1m3 | ||
| Total microbial number | <1000 CFU/1m3 | |||
| Intensive care room
| Staphylococcus aureus | <4 in 1m3 | ||
| Total microbial number | <1000 CFU/1m3 |
Practical task 1.
Practical task 3.
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