The WHO Expert Committee on Specifications for Pharmaceutical Preparations adopted in 2009 a revised version of the Good practices for pharmaceutical quality control laboratories (1). During the inspections carried out when prequalifying laboratories, the inspectors had noticed that some of the texts of these guidelines might benefit from additional guidance, with a special focus on microbiology. In light of the above, the Expert Committee recommended that the WHO Secretariat initiate the process of developing a new text on good practices for pharmaceutical microbiology laboratories. The following text is proposed to cover this specific type of laboratory.

Introduction and scope of the document


1. Personnel

2. Environment

2.1 Premises

2.2 Environmental monitoring in the laboratory

2.3 Cleaning, disinfection, and hygiene

2.4 Sterility test facilities

3. Validation of test methods

4. Equipment

4.1 Maintenance of equipment

4.2 Qualification4.3 Calibration, performance verification and monitoring of use

  1. Reagents and culture media

5.1 Reagents

5.2 Media

5.3 Labelling

5.4 Organism resuscitation

  1. Reference materials and reference cultures

6.1 International standards and pharmacopoeial reference substances

6.2 Reference cultures

7  Sampling

  1. Sample handling and identification
  2. Disposal of contaminated waste
  3. Quality assurance of results and quality control of performance

10.1 Internal quality control

  1. Testing procedures
  2. Test reports


Further reading

Appendix 1 Examples of zones in which operations could be carried out

Appendix 2 Examples of maintenance of equipment

Appendix  3 Examples of calibration checks and intervals for different laboratory equipment

Appendix 4 Examples of equipment Qualification and monitoring

Appendix 5 General use of reference cultures

Introduction and scope of the document

Pharmaceutical microbiology laboratories may be involved in — sterility testing; — detection, isolation, enumeration and identification of microorganisms (bacteria, yeast and moulds) and testing for bacterial endotoxins in different materials (e.g. starting materials, water), products, surfaces, garments and the environment; and — assay using microorganisms as part of the test system. These guidelines relate to all microbiology laboratories involved in the above-mentioned testing activities, whether they are independent or a department or unit of a pharmaceutical manufacturing facility. These guidelines are based on and supplement the requirements described in Good practices for pharmaceutical quality control laboratories (1); General guidelines for the establishment, maintenance, and distribution of chemical reference substances. Revision ( 2); The International Pharmacopoeia, Fourth Edition (3); First Supplement to The International Pharmacopoeia, Fourth Edition (4); and ISO/IEC 17025 (5).


calibration The set of operations that establish, under specified conditions, the relationship between values indicated by an instrument or system for measuring (especially weighing), recording and controlling, or the values represented by a material measure, and the corresponding is known values of a reference standard. Limits for acceptance of the results of measuring should be established.

certified reference material

Reference material, characterized by a metrologically valid procedure for one or more specified properties, accompanied by a certificate that provides the value of the specified property, its associated uncertainty and a statement of metrological traceability.

Limit of detection

The lowest number of microorganisms that can be detected, but in numbers that cannot be estimated accurately.


The degree of agreement among individual results.

Quantitation limit (limit of quantitation)

Applied to quantitative microbiological tests. The lowest number of microorganisms within a defined variability that may be counted under the experimental conditions of the method under evaluation.

Reference cultures

Collective term for reference strain and reference stocks.

Reference material

Material sufficiently homogeneous and stable with respect to one or more specified properties, which has been established to be fit for its intended use in a measurement process.

Reference method

A method which has been validated as being fi t for the purpose, with which an alternative method may be compared.

Reference stocks

A set of separate identical cultures obtained by a single subculture from the reference strain (6).

Reference Strains

Microorganisms defined at least to the genus and species level, cataloged and described according to its characteristics and preferably stating its origin (6). Normally obtained from a recognized national or international collection.


The closeness of the agreement between the results of successive measurements of the same measure and under the same conditions of measurement (adapted from ISO).


Reproducibility expresses precision between laboratories.

Robustness (or ruggedness)

The ability of the procedure to provide analytical results of acceptable accuracy and precision under a variety of conditions.

Sensitivity: The fraction of the total number of positive cultures or colonies correctly assigned in the presumptive inspection (7).


(selectivity) The ability of the method to detect the required range of microorganisms that might be present in the test sample.

Validation: Action of proving, in accordance with the principles of good practice quality guidelines and regulations (GxP), that any procedure, process, equipment (including the software or hardware used), material, activity or system actually and consistently leads to the expected results.

Verification: The application of methods, procedures, tests and other evaluations, in addition to monitoring, to determine compliance with GxP principles.

Working culture: A primary subculture from a reference stock (6).

  1. Personnel

1.1 Microbiological testing should be performed and supervised by an experienced person, qualified in microbiology or equivalent. Staff should have basic training in microbiology and relevant practical experience before being allowed to perform work covered by the scope of testing.

1.2 Current job descriptions for all personnel involved in tests and/ or calibrations, validations and verifications should be maintained. The laboratory should also maintain records of all technical personnel, describing their qualifications, training, and experience.

1.3 If the laboratory includes opinions and interpretations of test results in reports, this should be done by authorized personnel with suitable experience and relevant knowledge of the specific application including, for example, regulatory and technological requirements and acceptability criteria.

1.4 The laboratory management should ensure that all personnel has received adequate training for the competent performance of tests and operation of equipment. This should include training in basic techniques, e.g. plate pouring, counting of colonies, aseptic technique, media preparation, serial dilutions, and basic techniques in identification, with acceptability, determined using objective criteria where relevant. Personnel may only perform tests on samples if they are either recognized as competent to do so or if they do so under adequate supervision. Competence should be monitored continuously with provision for retraining where necessary. Where a method or technique is not in regular use, the competency of the personnel to perform the test should be verified before testing is undertaken. In some cases, it is acceptable to relate competence to a general technique or instrument being used rather than to particular methods.

1.5 Personnel should be trained in necessary procedures for containment of microorganisms within the laboratory facility.

1.6 Personnel should be trained in safe handling of microorganisms.

  1. Environment

2.1 Premises

2.1.1 Microbiology laboratories and certain support equipment (e.g. autoclaves and glassware) should be dedicated and separated from other areas, especially from production areas.

2.1.2 Microbiology laboratories should be designed to suit the operations to be carried out in them. There should be Sufficient space for all activities to avoid mix-ups, contamination, and cross-contamination. There should be adequate suitable space for samples, reference organisms, media (if necessary, with cooling), testing and records. Due to the nature of some materials (e.g. sterile media versus reference organisms or incubated cultures), separate storage locations may be necessary.

2.1.3 Laboratories should be appropriately designed and should take into account the suitability of construction materials to enable appropriate cleaning, disinfection and minimize the risks of contamination.

2.1.4 There should be separate air supply to laboratories and production areas. Separate air-handling units and other provisions, including temperature and humidity controls where required, should be in place for microbiological laboratories. The air supplied to the laboratory should be of appropriate quality and should not be a source of contamination.

2.1.5 Access to the microbiological laboratory should be restricted to authorized personnel. Personnel should be made aware of: — the appropriate entry and exit procedures including gowning; — the intended use of a particular area; — the restrictions imposed on working within such areas; — the reasons for imposing such restrictions; and — the appropriate containment levels.

2.1.6 Laboratory activities, such as sample preparation, media and equipment preparation, and enumeration of microorganisms, should be segregated by space or at least in time, so as to minimize risks of cross-contamination, false-positive results, and false-negative results. Where nondedicated areas are used, risk management principles should be applied. Sterility testing should always be performed in a dedicated area.

2.1.7 Consideration should be given to designing appropriate classified areas for the operations to be performed within the microbiology laboratory. The classification should be based on the criticality of the product and the operation being carried out in the area. Sterility testing should be performed under the same class as used for sterile/aseptic manufacturing operations. Appendix 1 shows recommendations for zone classifications.

2.1.8 In general, laboratory equipment should not routinely be moved between areas of different cleanliness class, to avoid accidental cross-contamination. Laboratory equipment used in the microbiology laboratory should not be used outside the microbiology area unless there are specific precautions in place to prevent cross-contamination.

2.2 Environmental monitoring in the laboratory

2.2.1 Where necessary and appropriate (e.g. in areas for sterility testing) an environmental monitoring programme should be in place which covers, for example, use of active air monitoring, air settling or contact plates, temperature and pressure differentials. Alert and action limits should be defi ned. Trending of environmental monitoring results should be carried out.

2.3 Cleaning, disinfection, and hygiene

2.3.1 There should be a documented cleaning and disinfection programme. Results of environmental monitoring should be considered where relevant.

2.3.2 There should be a procedure for dealing with spillages.

2.3.3 Adequate hand-washing and hand-disinfection facilities should be available.

2.4 Sterility test facilities

2.4.1 Sterility test facilities have specific environmental requirements to ensure the integrity of tests carried out. WHO good manufacturing practices (GMP) for sterile pharmaceutical products (8) requires that sterility testing should be carried out and specifies requirements for sterility testing. This section details the clean-room requirements for a sterility test facility.

2.4.2 Sterility testing should be performed under aseptic conditions, which should be equivalent to air quality standards required for the aseptic manufacture of pharmaceutical products. The premises, services, and equipment should be subject to the appropriate qualification process.

2.4.3 The sterility testing should be carried out within a Grade A unidirectional airflow protected zone or a biosafety cabinet (if warranted), which should be located within a clean room with a Grade B background. Alternatively, the testing can be carried out within a barrier isolator. Care should be taken with the design of the facility layout and room airfl ow patterns, to ensure that the unidirectional airfl ow patterns are not disrupted.

2.4.4 The clean-room classification and air-handling equipment of the sterility test facilities should be requalified at least annually by a competent person or contractor. The environment should comply with the non-viable and viable limits, and verification of high-efficiency particulate air (HEPA) filter integrity and room airflows should be performed. However, an alternative frequency of the monitoring may be justified based on quality risk management (QRM). Mapping locations for sample points for routine monitoring should be documented, as well as exposure duration, and frequency of all types of microbiological environmental monitoring should be specified in written procedures.

2.4.5 Air supplied to Grade A and B zones should be via terminal HEPA filters.

2.4.6 Appropriate air flow alarms and pressure differentials and indication instruments should be provided (GMP: Heating, ventilation and air-conditioning systems for non-sterile pharmaceutical dosage forms (8); and GMP for sterile pharmaceutical products (8).

2.4.7 Room pressure readings should be taken and recorded from externally mounted gauges unless a validated continuous monitoring system is installed. As a minimum, readings should be taken prior to entry of the operator to the test suite. Pressure gauges should be labeled to indicate the area served and the acceptable specification.

2.4.8 Entry to the clean room should be via a system of airlocks and a change room where operators are required to don suitable clean-room garments. The final change room should be under “at rest” conditions of the same grade as the room it serves. Change rooms should be of adequate size for ease of changing. There should be a clear demarcation of the different zones.

2.4.9 Garments for the sterility test operator should comply with the principles of section 10 of WHO GMP for sterile pharmaceutical products (8). Operators should be trained and certified in gowning procedures with training records maintained.

2.4.10 The fittings and finishes of the premises should comply with section 11 of WHO GMP for sterile pharmaceutical products (8).

2.4.11 Environmental microbiological monitoring should reflect the facility used (room or isolator) and include a combination of air and surface sampling methods appropriate to the facility, such as:

— active air sampling; — settle (exposure) plates; — surface contact — replicate organism detection and counting (RODAC) plates, swabs or flexible films; — operators’ glove prints.

Microbial environmental monitoring of the sterility test zone should be performed during every work session under operational (dynamic) conditions. There should be written specifications, including appropriate alert and action limits for microbial contamination. Limits for microbiological environmental monitoring are given in the WHO GMP for sterile pharmaceutical products (8).

  1. Validation of test methods

3.1 Standard (pharmacopoeial) test methods are considered to be validated. However, the specific test method to be used by a specific laboratory for testing of a specific product needs to be shown to be suitable for use in recovering bacteria, yeast and mold in the presence of the specific product. The laboratory should demonstrate that the performance criteria of the standard test method can be met by the laboratory before introducing the test for routine purposes (method verifi cation) and that the specific test method for the specific product is suitable (test method suitability including positive and negative controls).

3.2 Test methods not based on compendial or other recognized references should be validated before use. The validation should comprise, where appropriate, determining accuracy, precision, specifi city, limit of detection, limit of quantitation, linearity, and robustness. Potentially inhibitory effects from the sample should be taken into account when testing different types of sample. The results should be evaluated with appropriate statistical methods, e.g. as described in the national, regional or international pharmacopeias.

  1. Equipment: Each item of equipment, instrument or other device used for testing, verification and calibration should be uniquely identified. As part of its quality system, a laboratory should have a documented programme for the qualifi cation, calibration, performance verifi cation, maintenance and a system for monitoring the use of its equipment.

4.1 Maintenance of equipment

4.1.1 Maintenance of essential equipment should be carried out at predetermined intervals in accordance with a documented procedure. Detailed records should be kept. (For examples of maintenance of equipment and intervals see Appendix 2.)

4.2 Qualification

4.2.1 For Qualification of equipment see sections 8 and 12 in Good practices for pharmaceutical quality control laboratories (1).

4.3 Calibration, performance verification and monitoring of use

4.3.1 The date of calibration and servicing and the date when recalibration is due should be clearly indicated on a label attached to the instrument.

4.3.2 The frequency of calibration and performance verification will be determined by documented experience and will be based on need, type and previous performance of the equipment. Intervals between calibration and verification should be shorter than the time the equipment has been found to take to drift outside acceptable limits. (For examples of calibration checks and intervals for different laboratory equipment, see Appendix 3; and for equipment Qualification and monitoring, see Appendix 4.) The performance of the equipment should conform to predefined acceptance criteria.

4.3.3 Temperature measurement devices Where temperature has a direct effect on the result of an analysis or is critical for the correct performance of equipment, temperature measuring devices should be of appropriate quality to achieve the accuracy required (e.g. liquid-in-glass thermometers, thermocouples and platinum resistance thermometers (PRTs) used in incubators and autoclaves). Calibration of devices should be traceable to national or international standards for temperature.

4.3.4 Incubators, water-baths and ovens The stability of temperature, uniformity of temperature distribution and time required to achieve equilibrium conditions in incubators, water-baths, ovens, and temperature-controlled rooms should be established initially and documented, in particular with respect to typical uses (for example, position, space between, and height of, stacks of Petri dishes). The constancy of the characteristics recorded during the initial validation of the equipment should be checked and recorded after each signifi cant repair or modification. The operating temperature of this type of equipment should be monitored and records retained. The use of the equipment should be considered when determining what temperature controls are required.

4.3.5 Autoclaves, including media preparators Autoclaves should be capable of meeting specified time and temperature tolerances; monitoring pressure alone is not acceptable. Sensors

used for controlling or monitoring operating cycles require calibration and the performance of timers should be verifi ed. Initial validation should include performance studies (spatial temperature distribution surveys) for each operating cycle and each load configuration used in practice. This process must be repeated after any signifi cant repair or modification (e.g. replacement of thermoregulator probe or programmer, change to loading arrangements or operating cycle) or where indicated by the results of quality control checks on media or risk assessment. Sufficient temperature sensors should be positioned within the load (e.g. in containers filled with liquid/medium) to enable location differences to be demonstrated. In the case of media preparators, where uniform heating cannot be demonstrated by other means, the use of two sensors, one adjacent to the control probe and one remote from it, would generally be considered appropriate. Validation and revalidation should consider the suitability of come-up and come-down times as well as time at sterilization temperature. Clear operating instructions should be provided based on the heating profiles determined for typical uses during validation/revalidation. Acceptance/rejection criteria should be established and records of autoclave operations, including temperature and time, maintained for every cycle. Monitoring may be achieved by one of the following: — using a thermocouple and recorder to produce a chart or printout; —direct observation and recording of maximum temperature achieved and time at that temperature. In addition to directly monitoring the temperature of an autoclave, the effectiveness of its operation during each cycle may be checked by the use of chemical or biological indicators for sterilization or decontamination purposes. Autoclave tape or indicator strips should be used only to show that a load has been processed, not to demonstrate completion of an acceptable cycle. Laboratories should have a separate autoclave for decontamination. However, in exceptional cases, one autoclave may be acceptable provided that extensive precautions are taken to separate decontamination and sterilization loads, and a documented cleaning programme is in place to address both the internal and external environment of the autoclave.

4.3.6 Weights and balances Weights and balances shall be calibrated traceably at regular intervals (according to their intended use) using appropriate standard weights traceable to certified standard weights.

4.3.7 Volumetric equipment Microbiology laboratories should carry out initial verification of volumetric equipment (automatic dispensers, dispenser/diluters, mechanical hand pipettes, and disposable pipettes) and then make regular checks, as appropriate, to ensure that the equipment is performing within the required specifi cation. Initial verification should not be necessary for glassware which has been certified to a specific tolerance. Equipment should be checked for the accuracy of the delivered volume against the set volume (for several different settings in the case of variable volume instruments) and the precision of the repeat deliveries should be measured. For “single-use” disposable volumetric equipment, laboratories should obtain supplies from companies with a recognized and relevant quality system. After the initial validation of the suitability of the equipment, it is recommended that random checks on accuracy are carried out. If the supplier does not have a recognized quality system, laboratories should check each batch of equipment for suitability.

4.3.8 Other equipment Conductivity meters, oxygen meters, pH meters, and other similar instruments should be verified regularly or before each use. The buffers used for verification purposes should be stored in appropriate conditions and should be marked with an expiry date. Where humidity is important to the outcome of the test, hygrometers should be calibrated, the calibration being traceable to national or international standards. Timers, including the autoclave timer, should be verified using a calibrated timer or national time signal. When centrifuges are used in test procedures, an assessment of the rotations per minute (RPM) should be made. Where it is critical, the centrifuge should be calibrated.

  1. Reagents and culture media Laboratories should ensure that the quality of reagents and media used is appropriate for the test concerned.

5.1 Reagents 5.1.1 Laboratories should verify the suitability of each batch of reagents critical for the test, initially and during its shelf-life.

5.2 Media

5.2.1 Media may be prepared in-house or purchased either partially or fully prepared. Vendors of purchased media should be approved and qualifi ed. The qualified vendor may certify some of the quality parameters listed subsequently. Growth promotion and, if appropriate, other suitable performance tests (see section 5.2.2) should be done on all media on every batch and on every shipment. Where the supplier of fully prepared media is qualified and provides growth promotion certification per batch of media and transportation conditions have been qualified, the user may rely on the manufacturer’s certificate with periodic verification of his or her results.

5.2.2 The suitable performance of culture media, diluents, and other suspension fluids should be checked, where relevant, with regard to:

— recovery or survival maintenance of target organisms. Recovery of 50–200% (after inoculation of not more than 100 colony-forming units (CFU or CFU) should be demonstrated; — inhibition or suppression of non-target organisms; —biochemical (differential and diagnostic) properties; and — other appropriate properties (e.g. pH, volume and sterility).

Quantitative procedures for evaluation of recovery or survival are preferred.

5.2.3 Raw materials (both commercial dehydrated formulations and individual constituents) and media should be stored under appropriate conditions recommended by the manufacturer, e.g. cool, dry and dark. All containers, especially those for dehydrated media, should be sealed tightly. Dehydrated media that are caked or cracked or show a color change should not be used.

5.2.4 Water of a suitable microbiological quality and which is free from bactericidal, inhibitory or interfering substances, should be used for preparation unless the test method specifies otherwise.

5.2.5 Media containing antimetabolites or inhibitors should be prepared using dedicated glassware, as carry-over of these agents into other media could inhibit the growth and detection of microorganisms present in the sample under test. If dedicated glassware is not used, washing procedures for glassware should be validated.

5.2.6 Repartition of media after sterilization should be performed under unidirectional airflow (UDAF) to minimize the potential for environmental contamination. This should be considered a minimum requirement for media to be used in relation to sterile product testing. This includes the cooling of media, as container lids will need to be removed during cooling to prevent the build-up of condensation.

5.2.7 Plated media which is to be irradiated may require the addition of an antioxidant and free radical scavenger to provide protection from the effects of the irradiation process. The irradiated media should be validated by performing quantitative growth promotion testing on both irradiated and non-irradiated media.

5.2.8 Shelf-life of prepared media under defined storage conditions shall be determined and verifi ed.

5.2.9 Batches of media should be identifi able and their conformance with quality specifications documented. For purchased media, the user laboratory should ensure that it will be notifi d by the manufacturer of any changes to the quality specification.

5.2.10 Media should be prepared in accordance with any manufacturer’s instructions, taking into careful account specifications such as time and temperature for sterilization.

5.2.11 Microwave devices should not be used for the melting of media due to the inconsistent distribution of the heating process.

5.3 Labelling 5.3.1 Laboratories should ensure that all reagents (including stock solutions), media, diluents and other suspending fluids are adequately labeled to indicate, as appropriate, identity, concentration, storage conditions, preparation date, validated expiry date and/or recommended storage periods. The person responsible for preparation should be identifi able from records.

5.4 Organism resuscitation

5.4.1 Organism resuscitation is required where test methodologies may produce sublethally injured cells. For example,

exposure to:— injurious effects of processing, e.g. heat; — antimicrobial agents; — preservatives; — extremes of osmotic pressure; and — extremes of pH.

5.4.2 Organism resuscitation may be achieved by:

— exposure to a liquid media like a simple salt solution at room temperature for 2 hours; — exposure to a solid repair medium for 4–6 hours.

  1. Reference materials and reference cultures 6.1 International standards and pharmacopoeial reference substances 6.1.1 Reference materials and certified reference materials are generally used in a microbiological laboratory to qualify, verify and calibrate equipment.

Whenever possible these reference materials should be used in appropriate matrices.

International standards and pharmacopoeial reference substances are employed, for example, to:

— determine potency or content; —methods; — enable comparison of methods; — perform positive controls; and — perform growth promotion tests. If possible reference materials should be used in appropriate matrices.

6.2 Reference cultures

6.2.1 Reference cultures are required for establishing the acceptable performance of media (including test kits), for validating methods, for verifying the suitability of test methods and for assessing or evaluating ongoing performance. Traceability is necessary, for example, when establishing media performance for the test kit and method validations. To demonstrate traceability, laboratories must use reference strains of microorganisms obtained directly from a recognized national or international collection, where these exist. Alternatively, commercial derivatives for which all relevant properties have been shown by the laboratory to be equivalent at the point of use may be used.

6.2.2 Reference strains may be subcultured once to provide reference stocks. Purity and biochemical checks should be made in parallel as appropriate. It is recommended to store reference stocks in aliquots either deep-frozen or lyophilized. Working cultures for routine use should be primary subcultures from the reference stock (see Appendix 5 on general use of reference cultures). If reference stocks have been thawed, they must not be refrozen and reused.

6.2.3 Working stocks should not normally be subcultured. Usually, not more than five generations (or passages) from the original reference strain can be subcultured if defined by a standard method or laboratories can provide documentary evidence that there has been no change in any relevant property. Commercial derivatives of reference strains may only be used as working cultures.

  1. Sampling For general principles reference is made to Good practices for pharmaceutical quality control laboratories (1).

7.1 Where testing laboratories are responsible for primary sampling to obtain test items, it is strongly recommended that this sampling is covered by a quality assurance system and it should be subject to regular audits.

7.2 Any disinfection processes used in obtaining the sample (e.g. disinfection of sample points) should not compromise the microbial level within the sample.

7.3 Transport and storage of samples should be under conditions that maintain the integrity of the sample (e.g. chilled or frozen where appropriate). Testing of the samples should be performed as soon as possible after sampling. For samples where a growth in the microbial population during transport and storage is possible it should be demonstrated that the storage conditions, time and temperature, will not affect the accuracy of the testing result. The storage conditions should be monitored and records kept. The responsibility for transport, storage between sampling and arrival at the testing laboratory should be clearly documented.

7.4 Sampling should only be performed by trained personnel. It should be carried out aseptically using sterile equipment. Appropriate precautions should be taken to ensure that sample integrity is maintained through the use of sterile sealed containers for the collection of samples where appropriate. It may be necessary to monitor environmental conditions, for example, air contamination and temperature, at the sampling site. Time of sampling should be recorded, if appropriate.

  1. Sample handling and identification

8.1 The laboratory should have procedures that cover the delivery and receipt of samples and sample identification. If there is the insufficient sample or the sample is in poor condition due to physical deterioration, incorrect temperature, torn packaging or deficient labeling, the laboratory should consult with the client before deciding whether to test or refuse the sample. 8.2 The laboratory should record all relevant information, e.g. — date and, where relevant, the time of receipt; — condition of the sample on receipt and, when necessary, temperature; and— characteristics of the sampling operation (including sampling date and sampling conditions).

8.3 Samples awaiting testing should be stored under suitable conditions to minimize changes to any microbial population present. Storage conditions should be validated, defined and recorded.

8.4 The packaging and labels of samples may be highly contaminated and should be handled and stored with care so as to avoid any spread of contamination. Disinfection processes applied to the outer container should not affect the integrity of the sample. It should be noted that alcohol is not sporicidal.

8.5 Subsampling by the laboratory immediately prior to testing may be required as part of the test method. It may be appropriate that it is performed according to national or international standards, where they exist, or by validated in-house methods. Subsampling procedures should be designed to collect a representative sample.

8.6 There should be a written procedure for the retention and disposal of samples. If sample integrity can be maintained it may be appropriate that samples are stored until the test results are obtained, or longer if required. Laboratory sample portions that are known to be contaminated should be decontaminated prior to being discarded (see section 11.1).

  1. Disposal of contaminated waste

9.1 The procedures for the disposal of contaminated materials should be designed to minimize the possibility of contaminating the test environment or materials. It is a matter of good laboratory management and should conform to national/international environmental or health and safety regulations.

  1. Quality assurance of results and quality control of performance

10.1 Internal quality control

10.1.1 The laboratory should have a system of internal quality assurance or quality control (e.g. handling deviations, use of spiked samples, replicate testing and participation in proficiency testing, where appropriate) to ensure the consistency of results from day to day and their conformity with defined criteria.

  1. Testing procedures

11.1 Testing should normally be performed according to procedures described in the national, regional and international pharmacopeias.

11.2 Alternative testing procedures may be used if they are appropriately validated and equivalence to official methods has been demonstrated.

  1. Test reports

12.1 If the result of the enumeration is negative, it should be reported as “not detected for a defined unit” or “less than the detection limit for a defined unit”. The result should not be given as “zero for a defined unit” unless it is a regulatory requirement. Qualitative test results should be reported as “detected/not detected in a defined quantity or volume”. They may also be expressed as “less than a specified number of organisms for a defined unit” where the specified number of organisms exceeds the detection limit of the method and this has been agreed with the client. In the raw data, the result should not be given as zero for a defined unit unless it is a regulatory requirement. A reported value of “0” may be used for data entry and calculations or trend analysis in electronic databases

12.2 Where an estimate of the uncertainty of the test result is expressed on the test report, any limitations (particularly if the estimate does not include the component contributed by the distribution of microorganisms within the sample) have to be made clear to the client.


  1. Good Practices for pharmaceutical quality control laboratories. In: WHO Expert Committee on Specifications for Pharmaceutical Preparations. Forty-fourth report. Geneva, World Health Organization. WHO Technical Report Series, No. 957, 2010, Annex 1.
  2. General guidelines for the establishment, maintenance, and distribution of chemical reference substances. Revision. In: WHO Expert Committee on Specifications for Pharmaceutical Preparations. Forty-first report. Geneva, World Health Organization. WHO Technical Report Series, No. 943, 2007, Annex 3.
  3. The International Pharmacopoeia, Fourth Edition. Geneva, World Health Organization, 2006. Also available on CD-ROM.
  4. The International Pharmacopoeia, Fourth Edition, First Supplement. Geneva, World Health Organization, 2008. Also available on CD-ROM.
  5. ISO/IEC 17025 (2005) General requirements for the competence of testing and calibration laboratories.
  6. ISO 11133-1 (2000) Microbiology of food and animal feeding stuffs — Guidelines on preparation and production of culture media — Part 1: General guidelines on quality assurance for the preparation of culture media in the laboratory.
  7. ISO 13843 (2000) Water quality — Guidance on validation of microbiological methods.
  8. WHO good manufacturing practices: main principles for pharmaceutical products. In: Quality assurance of pharmaceuticals. A compendium of guidelines and related materials. Volume 2, 2nd updated edition. Good manufacturing practices (GMP) and inspection. Geneva, World Health Organization, 2007, and subsequent updates, including WHO GMP for sterile pharmaceutical products. In: WHO Expert Committee on Specifications for Pharmaceutical Preparations. Forty-fifth report. Geneva, World Health Organization. WHO Technical Report Series, No. 961, Annex 6, 2011; and GMP: Heating, ventilation and air-conditioning systems for non-sterile pharmaceutical dosage forms. In: WHO Expert Committee on Specifications for Pharmaceutical Preparations. Forty-fifth report. Geneva, World Health Organization. WHO Technical Report Series, No. 961, 2011, Annex 5.

Further reading

ISO 7218 (2007) Microbiology of food and animal feeding stuffs — General requirements and guidance for microbiological examinations.

ISO 6887-1 (1999) Microbiology of food and animal feeding stuffs — Preparation of test samples, initial suspension and decimal dilutions for microbiological examination — Part 1: General rules for the preparation of the initial suspension and decimal dilutions.

ISO Guide 30 (1992) Terms and defi nations used in connection with reference materials.

ISO 9000 (2008) Quality management systems — fundamentals and vocabulary.

ISO Guide 99 (1993) International vocabulary of basic and general terms in metrology (VIM).

ISO (CIPM):1995. Guide to the expression of uncertainty in measurements.

Draft ISO/DIS 16140. (1999) Food microbiology. Protocol for the validation of alternative methods.

Draft ISO/FDIS (2003) 11133-2. Microbiology of food and animal feeding stuff. Guidelines on preparation and production of culture media. Part 2 — Practical guidelines on performance testing on culture media.

EN 12741 (1999). Biotechnology — Laboratories for research, development, and analysis — Guidance for biotechnology laboratory operations.





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