Infection control in the clinical laboratory

O Laboratory personnel are analyzed blood and body fluids that may contain infective agents from sick and seemingly well patients.

Infection can be caused by:A. Pathogens being inhaled in aerosols when snap closing specimen containers, dispensing or pipetting infectious fluids.

Infection

B. Pathogens being ingested from contaminated fingers, or in food that has been contaminated, e.g. by being stored in a medical laboratory refrigerator.

C. Mouth- pipetting of specimens and cultures, which is one of the commonest ways of ingesting pathogens

D. Pathogens entering the skin through needle punctures, cuts, scratches insect bites sores or other open skin lesions, Hence, always handle infected needles with great care.

laboratory employee protection

O The greatest danger is to have blood born disease (such as HBV, HCV and AIDS) by virus transmission which arises from:O Accidental “Needle Stick”O Direct Mucous Membrane Contact

(mouth/nose/eye)O Oral Ingestion (pipetting accident)O Open Wound Contact (accidental splash)O Cut Finger (from blood contaminated tube)

O If one has such an accident involving blood, plasma or serum from a specific identifiable patient, he should report immediately to his supervisor.

  O The supervisor is to report the patient’s name. O A blood specimen is to be obtained from the

patient and sent to be tested for blood born viruses

O If the patient (source) results are negative, no further actions will be taken except to inform the employee

O If the source result of Hepatitis b is positiveO The employee should receive two injections of

Hepatitis B Immune Globulin; the first with 7 days of exposure, the second within 28-30 days of exposure.

O If the source result of Hepatitis c is positiveO Perform baseline testing for anti-HCV and ALT

activity; andO Perform follow-up testing (e.g., at 4--6 months) for

anti-HCV and ALT activityO IG and antiviral agents are not recommended after

exposure to HCV-positive blood.

OIf the source result is positive for HIVO The laboratory worker should be counseled

regarding the risk of infection and evaluated clinically and serologically for evidence of HIV infection as soon as possible after the exposure. 

O The laboratory worker should seek medical evaluation for any acute febrile illness that occurs within 12 weeks after the exposure, particularly one characterized by fever, rash, or lymphadenopathy.  

O Seronegative persons should be retested 6 weeks post exposure and on a periodic basis thereafter (e.g., 12 weeks and 6 months after exposure) to determine whether transmission has occurred. 

O health-care workers must consider ALL patients as potentially infected with HIV and/or other blood-borne pathogens and to adhere vigorously to infection-control precautions for minimizing the risk of exposure to blood and body fluids of all patients.  

UNIVERSAL BLOOD AND BODY FLUIDS PRECAUTIONS

 1.    All laboratory workers should routinely use appropriate barrier precautions to prevent skin and mucous membrane exposure when contact with blood or other body fluids of any patients is anticipated.  O Gloves should be worn for touching blood and body fluids,

for handling items or surfaces soiled with blood and body fluids, and for performing venipuncture. 

Gloves should be changed after contact with each patient. O Masks and protective eyewear or face shields should

be worn during procedures that are likely to generate droplets of blood or other body fluid to prevent exposure of mucous membranes of the mouth, nose, and eyes. 

O Gowns or aprons should be worn during procedures that are likely to generate splashes of blood or other body fluids.

2.  All laboratory workers should take precautions to prevent injuries caused by needles, scalpels, and other sharp instruments or devices during procedures; when cleaning used instruments during disposal of used needles, and when handling  sharp instrument after procedures.  O To prevent needle stick injuries, needles should

not be recapped, purposely bent or broken by hand, removed from disposal syringes; and needles, scalpel blades, and other sharp items should be placed in puncture-resistant containers (SAFETY BOX) for disposal.  

O The puncture resistant containers should be located as close as practical to the use area. 

3. Hands and other skin surfaces should be washed immediately and thoroughly if contaminated with blood or other body fluids.  Hands should be washed immediately after gloves are removed.O Hand-washing is considered the most

important single procedure for preventing and controlling the spread of infection.  Proper hand-washing has been shown to eliminate or greatly reduce hand carriage of pathogens.

O There are two types of hand-washing to be used in the Laboratory:  routine and antiseptic.

O Routine hand-washing is used:1. When coming on duty2. Before and after eating3. Before and after using the restroom4. Before going off duty

O Antiseptic hand-washing is used:1. After contact with contaminated objects2. After contact with patient specimens,

particularly “Blood and Body Fluid Precaution” specimens

3. After removal of protective gloves

Hand-washing procedure

O RoutineO Wet hands under running waterO Keep hands lower than elbows, apply SOAPO Work into a lather scrubbing fingers, palms, backs of

hands, wrist and forearms creating friction for at least 15 seconds.  Cleaning under nails should be attempted.

O Thoroughly rinse hands under running waterO Use paper towels to blot and dry handsO Use dry paper towel to turn off faucet, then discard

O Antiseptic:O Follow the procedure for routine hand-washing, but

use an ANTISEPTIC product instead of soap.

4.     Laboratory workers who have exudative lesions or weeping dermatitis should refrain from all direct patient care and from handling patient care equipment until the condition resolves.O Open cuts and broken skin must be covered with

a suitable means of protection, such as gloves, to avoid the risk of contamination and possible infections.

5.    All specimens of blood and body fluids should be put in a well constructed container with a secure lid to prevent leaking during transport.  Care should be taken when collecting each specimen to avoid contaminating the outside of the container and of the laboratory form accompanying the specimen.

6.   Mechanical pipetting devices should be used for manipulating all liquids in the laboratory. Mouth pipetting must not be done.

7.    Contaminated materials used in laboratory tests should be decontaminated before reprocessing or be placed in bags and disposed of in accordance with institutional policies for disposal of infective waste.

8.    Scientific equipment that has been contaminated with blood or other body fluids should be decontaminated and cleaned before being repaired in the laboratory or transported to the manufacturer.

9.    All persons should wash their hands after completing laboratory activities and should remove protective clothing before leaving the laboratory.

10. Work surfaces should be decontaminated at least once a day and immediately following any spill involving potentially infectious material. In most cases, surfaces can be decontaminated with alcohol 70% or any other effective disinfectant such as:

1. Alcohol 70% is lethal for all vegetative cells, as it disrupts cellular membranes.

2. Phenolic compounds 10%, such as phenol (carbolic acid), Lysol, Tylenol (Dettol) used for floors and surfaces.

3. Halogens such Iodine and chlorine act as oxidizing agents. Such as hypochlorite (0.5%)

4. Detergents.

Sterilization and disinfection

SterilizationSterilization is the process of destruction or elimination of all forms of microorganisms by physical means including heat, radiation, and filtration) and chemical agents (acids, alkalis, heavy metals, salts, halogens, etc). The equipment or material treated then becomes “Sterile”.

In medical laboratories, materials and equipments are sterilized for the following main purposes.

1. In preparation for taking specimens, such as needles, syringes, test tubes, etc.

2. To sterilize contaminated materials and equipments.

3. To prepare apparatus used for bacteriological cultures, such as petridishes, Pasteur pipettes, and others.

Methods of sterilization

Physical method1. Dry heat (hot air oven, flaming and red - hot)2. Moist heat (autoclave or steam under pressure and boiling 3. Radiation4. Mechanical

Dry heat1. Hot Air ovenO The material to be sterilized is placed in an

oven and the temperature is raised and maintained at 1800c for 30 minutes.

O The sterilized material should not be removed until the oven is cold. This is important particularly with pertidishes, as cold air will be sucked in to them, causing contamination, if they are removed before the oven is cold.

O This method is used only for glass or metal articles such as test tubes, petridishes, all glass syringes, and instruments.

2. FlamingO Metal spatula, glass slides, and cover slips

may be sterilized by passing them through a Bunsen flame, with out letting them become red hot. Alternatively they may be dipped in metylated spirit, and the alcohol burned off. This procedure should be repeated two or three times.

3. Red - hotO Wire loops and tips of forceps may be

sterilized by heating them in a Bunsen flame until they become red hot and allow the materials (instruments) to cool before using them.

Moist heat1.Boiling waterO Moist heat may be applied by boiling water or

steam. O Boiling water is generally used for sterilizing

instruments and syringes. O These are boiled for 10 minuets in a water bath.O This will kill all non-sporing organisms but certain

spore forming organisms can resist the temperature of boiling water for 1-2 hours.

O The addition of 2% sodium carbonate increases the disinfecting power of boiling water for 1-2 hours. Spores, which resist boiling water for 10 hours, have been killed within 30 minutes by the addition of sodium carbonate.

2. Steam under pressure (autoclave)O Autoclave is an instrument that operates by

creating high temperature under steam pressure. Autoclaving is the most common, effective, reliable and practical method of sterilizing laboratory materials.

O The principle of autoclave is that steam is kept at a pressure of 15 pound (lb) per square inch to give a temperature of 1210c, which will kill spores with in 15 minutes.

O At this particular temperature, pressure and time, all forms of lives are destroyed

O It is used to sterilize syringes, needles, glasswares, culture media, etc

Radiation (ultra - violet ray)O UV radiation is lethal to certain

microorganisms by inactivating the DNA of the organisms.

O It is effective and valuable in sterilization of air in a given room or place. E.g: Pulmonary tuberculosis Laboratory

Mechanical methodO Filtration is a mechanical method for

eliminating bacteria from biological fluids and from the laminar flow systems, which are used to ventilate operating rooms, laboratories and areas having immune suppressed and burn patients.

O Filtered air is pumped into the space at a pressure required to displace regular circulating air.

Chemical methodsO Generally, many chemicals are lethal to

microorganismsO Some of the commonly used chemicals are

hypochlorite solution (‘berekina’), phenolic derivatives and ethylene oxide.

DisinfectionO Disinfection is the process of destruction of

pathogenic or potentially pathogenic microorganisms by chemical means.

O Decontamination is the process of decreasing the virulence (ability to cause disease) of microorganisms by using different chemical agents.

AlcoholO Ethanol and isopropanol, at 70 -80% volume /

volume (v/v) concentration in water, are useful for skin, work surfaces of laboratory benches and biosafety cabinets, and to soak small surgical instruments. They are active against vegetative bacteria, fungi and lipid containing viruses, but not against spores.

O Their activity is improved by mixing them with formalin or hypochlorite. A major advantage of aqueous solutions of alcohols is that they do not leave any residue on treated items.

Phenolic compoundsO Phenolic compounds are a broad group of agents,

were among the earliest germicides. However, more recent safety concerns restrict them their use.

O They are active against vegetative bacteria and lipid containing viruses

O They are not active against spores and their activity against non-lipid viruses is variable.

O Many phenolic products are used for the decontamination of environmental surfaces, and some (example, triclosan and chloroxylene) are among the more commonly used antiseptics.

O They are used at 2 - 5% volume/volume (v/v) concentration according to the manufacturers instruction.

Chlorine (sodium hypo chloride)O Chlorine, a fast - acting oxidant, is a widely

available and broad-spectrum chemical germicide.

O It is normally sold as bleach, an aqueous solution of sodium hypo chloride, which can be diluted with water to provide various concentrations of available chlorine.

O Products containing 100,000 parts per million (ppm) of chlorine are suitable for laboratory use.

O They are effective against viruses as well as bacteria.

O Dilutions should not be kept for more than 24 hours so as to maintain its activity.

FormaldehydeO Formaldehyde is a gas that kills all

microorganisms and spores.O It is relatively slow acting chemical and needs a

relative humidity level of about 70% Five percent (5%) formaldehyde is widely used for decontamination and disinfection of enclosed volumes such as safety cabinets and laboratory rooms.

Iodine and iodophorsO Iodine and iodophors have similar action to

that of chlorine.O Iodophors and tincture of iodine are good

antiseptics. O Iodine can be toxic. O Organic iodine based products must be stored

at 4 -100C to avoid the growth of potentially harmful bacteria in them

Biological Safety Cabinets

O also called microbiological safety cabinet — is an enclosed, ventilated laboratory workspace for safely working with materials contaminated with (or potentially contaminated with) pathogens requiring a defined biosafety level. Several different types of BSC exist, differentiated by the degree of biocontainment required.

Opurpose The primary purpose of a BSC is to serve as a means to protect the laboratory worker and the surrounding environment from pathogens

BioSafety Levels

O Biosafety Level 1 O BSL-1 laboratories are used to study

agents not known to consistently cause disease in healthy adults.

O They follow basic safety procedures and require no special equipment or design features.

BioSafety LevelsO Biosafety Level 2

O BSL-2 laboratories are used to study moderate-risk agents that pose a danger if accidentally inhaled, swallowed or exposed to the skin.

O Safety measures include limited access, biohazard warning signs, sharps precautions, class I or II BSCs, the use of PPE such as gloves and eyewear as well as handwashing sinks and waste decontamination facilities such as an autoclave.

BioSafety Levels

O Biosafety Level 3 O BSL-3 laboratories are used to study agents

that can be transmitted through the air and may cause potentially lethal infection.

O Researchers perform lab manipulations in class I or II BSCs or other enclosure. Other safety features include clothing decontamination, sealed windows, double-door access, and specialized ventilation systems.

BioSafety LevelsO Biosafety Level 4

O BSL-4 laboratories are used to study agents that pose a high risk of life-threatening disease, aerosol-transmitted lab infections, or related agents whose risk is not known. Lab personnel are required to to shower when exiting the facility. The labs incorporate all BSL 3 features and occupy safe, isolated zones within a larger building or a separate building. Procedures are performed in Class III BSCs or Class II while wearing a positive pressure full-body suit.

O The laboratory director is specifically and primarily responsible for assessing the risks and appropriately applying the recommended biosafety levels.