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  Analyses
laboratories can be places at high risk of infection for the personnel. However,
although pathologic materials frequently infected are carried to the
microbiological laboratories (designed for the bacteriological and
virological diagnosis of infectious diseases), the laboratories at
highest risk are, or better were, represented by haematological
laboratories and biochemical-clinical analyses laboratories. This paradox
is due to the fact that microbiologists are aware of the potential
pathological nature of the materials they deal with. Furthermore,
microbiologists work in sterile conditions, which is not the case in the
other laboratories, and all procedures are carried out with extreme
attention and care also in order to avoid contamination of the examined
material to preserve its diagnostic value.
In the last few years, as knowledge of the ways of diffusion of hepatitis
B and AIDS spread, the probability of getting infections in the
laboratories has dropped because now workers pay more attention when
handling samples than in the past. However this probability is still
present, although it is difficult to prove that such infections are
really linked to the occupational activity. The causal relation can be
proved with relative certainty only when the etiological agent is rare. For
example, pneumococcal pneumonia is considered an occupational illness in
France when it occurs in a laboratory worker that, in the two weeks
preceding the infection, had been in contact with such microorganism for
occupational reasons.
Regarding the infections contracted in the laboratories, sometimes the
penetration of the pathogenic agent can take place through ways other
than the natural ones. For example, it is well known that the general
population can contract brucellosis through ingestion of contaminated
food. On the other hand, in laboratory workers (as well as in vets) the
germ penetrates through insignificant solutions of continuity of the skin
or even through the whole skin (transcutaneous route). Microorganisms can
penetrate in the health worker also through the digestive route, as in
the case of accidental ingestion of bacteria. This is the case of
microorganisms responsible for typhus or typhoid enteric fever (the
number of bacteria needed to overcome the defensive barriers of the human
body, are relatively high, in the order of 105-109 microorganisms).
This kind of transmission is linked, especially in the smaller
laboratories, with the habit of storing drinks and food in laboratories'
fridges or of consuming drinks and food or smoking in the laboratories. The
third kind of transmission is by inhalation. In many laboratory
activities aerosols are produced as a result of improper use of the loop.
A loop that is too long or a kink too big can cause, during some phases,
the dispersion in the environment of small drops contaminated by
bacteria. The same effects can be brought about by an incorrect heat
sterilization.
The microorganism most frequently involved in infective events linked to
such practices is Mycobacterium tuberculosis. In fact, this microorganism
gives origin to dry colonies that easily disperse in the air of the
laboratories if precautions, such as the employment of specific
loop-sterilizing rooms, are not taken. The fourth and last kind of
transmission is accidental inoculation. This can follow accidents such as
needle prick or injuries occurred with other sharp objects such as
lancets or broken glasses and it can be responsible for a number of
infectious diseases both bacterial (for example brucellosis, diphtheria,
syphilis) and viral (for example hepatitis B and C, AIDS, mononucleosis
infectious and others).
For additional information
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