Laboratory Acquired Infections

Introduction: 

Laboratory-acquired infections (LAIs) are defined as all infections acquired through laboratory or laboratory-related activities, also called occupational illness or laboratory-associated infections. 

v  Working with pathogenic microorganisms requires good laboratory practices, risk assessments, and biosafety/biosecurity measures to ensure the safety of personnel, community, and the environment from accidental or deliberate infection.

v  Clinical diagnostic laboratories accounted for 45% of all laboratory-acquired infections. 

Laboratory workers, especially those in microbiology, are at greater risk of becoming infected than the general population.

v  An occupationally-acquired infection of laboratory personnel is referred to as a laboratory-acquired infection (LAI) and these have been reported in scientific literature since 1897.

v  Accidents or exposure events leading to LAIs may include inhalation of infectious aerosols, contact with mucous membranes by splash, touch, or spill, or infection via the percutaneous route (bites, cuts, accidental self-inoculation).

v  Laboratory infections due to a wide variety of bacteria, viruses, rickettsiae, fungi, and parasites.

v  In 1976 - R.M. Pike, surveyed huge laboratory acquired infections and reported 4079 cases by 159 biological agents.  

v  The major ten pathogens caused infections accounting for 50 % of cases are brucellosis, Q fever, hepatitis, typhoid fever, tularemia, tuberculosis, dermatomycoses, Venezuelan equine encephalitis, psittacosis, and coccidioidomycosis.

v  During the 20 years following the Pike and Sulkin publications, a worldwide literature review by Harding and Byers revealed 1267 cases of infections, with 22 deaths.

v  Five deaths were foetus abortions as consequences of a maternal LAI.

v  Mycobacterium tuberculosis, Coxiella burnetii, hantaviruses, arboviruses, Hepatitis B virus, Brucella spp., Salmonella spp., Shigella spp., hepatitis C virus, and Cryptosporidium spp. accounted for 1074 of the 1267 infections.

Bacterial LAI:

§  M. tuberculosis can be isolated from a variety of clinical specimens, aerosols generated is the most important risk factor for acquiring tuberculosis in the laboratory. The infective dose is <10bacilli.

§  Brucellosis continues to be the most frequently reported laboratory-associated bacterial infection. Accounting for 24% of laboratory-acquired bacterial infections and 11% of deaths, aerosol transmission.

§  Salmonella typhi - typhoid fever has accounted for more reported fatalities than any other laboratory-acquired infection.

§  Typhoid fever were associated with mouth pipetting and handling of proficiency test strains.

§  Laboratory-acquired shigellosis is that Shigella species are more virulent and require a much lower inoculum to cause illness.

§  Francisella tularensis is a fastidious, gram-negative coccobacillus that is infrequently encountered in the clinical microbiology laboratory, possible use as a bioterrorism agent - infectious aerosols from manipulation of cultures.

o   Blood cultures, sputum cultures, and autopsy pleural fluid were all positive for gram-negative coccobacilli – pneumonic tularemia.

Viral HAI:

¨     Viral agents transmitted through blood and bodily fluids, common blood-associated viruses, hepatitis B virus (HBV) is the most common cause of laboratory-acquired infection.

¨     HBV incidence estimated to be 3.5–4.6 infections per 1000 workers, which is 2–4 times than the level for the general population.

¨     HCV - 5 occupational exposures (1.5%) to blood.

¨     The risk of HIV transmission after a percutaneous exposure to HIV-infected blood has been estimated to be ∼0.3%, and the risk has been estimated to be ∼0.09% after exposure to a mucous membrane. Exposure to contaminated blood or body fluids.

Fungal Pathogens:

The dimorphic fungi Blastomyces dermatitidis, Coccidioides immitis and Histoplasma caspsulatum are responsible for the majority of laboratory-acquired fungal infections.

Parasites:

              Laboratory-acquired parasitic infections are uncommon in the diagnostic microbiology laboratory.

Blood and tissue protozoa – Trypanosoma cruzi, Toxoplasma gondii, Plasmodium sp, etc.,

Intestinal protozoa – Cryptosporidium parvum, Entamoeba histolytica.

Helminthes – Schistosoma sp, Ascaris lumbricoides.

 

Inhalation of Aerosols and Droplets

 

¨     Pipetting, blenders, pouring, non-self-contained centrifuges, sonicators, vortex mixers, flaming a reusable loop, and catalase testing may generate airborne respirable size particles (<0.05 mm in diameter).

¨     Lyophilized cultures, dried materials on laboratory benches, and bacterial and fungal spores can act as droplet nuclei.

¨     Contaminating gloved hands, work surfaces, and possibly mucous membranes of the person performing the procedure.

¨     Contaminated sharps such as blades and broken glassware, Spills, sprays, and splashes into eyes, mouth, or nose and hand-to-face actions, skin cuts, abrasions, and dry, inflamed skin, Contaminated surfaces and equipment.

 

Safety precautions

1.      Use of PPE (Personnel protective equipment) -  gloves, masks, face shields, coats, gowns, respirators,

2.      Use of safety centrifuge containers, sharps protection, and biological safety cabinets.

3.      Decontamination facility, handwashing facilities, specialized ventilation, and/or airflow.

4.      Clean hygienic practices – procedure to address accidental spills, release of pathogens in laboratory, reporting of injuries, illnesses, and incidents of potential exposure and its documentation.

5.      Disposal of biohazards – blood and blood products, culture exposure, sputum samples, urine, faecal samples, etc.,.

6.      Medical surveillance,  safety manual, training programs to adhere safety procedures.