Environmental Engineering Reference
In-Depth Information
Because of the presence of antigens on
their cell walls and membranes, bacteria have the potential to cause allergic
reactions similar to those observed with mold, insect excreta, and animal
danders. Though a few studies have shown that exposure to various Gram-
negative and Gram-positive bacteria can cause allergic responses (such as
the release of histamine), bacteria have not been clinically identified as a
cause of chronic allergic rhinitis or asthma.
The higher bacteria, especially thermophilic actinomycetes, have been
definitively identified as a major causal organism in the development of
hypersensitivity pneumonitis. Exposures to thermophilic actinomycete spe-
cies
e.
Hypersensitivity diseases.
Faenia rectivirgula, Saccharomonosporo viridis,
and
Thermoactinomyces vul-
garis
are known to cause farmer's lung, with
T. vulgaris, T. sacchari,
and
T.
thalophilus
responsible for bagassosis, a hypersensitivity disease of sugar
cane workers. Hypersensitivity pneumonitis has also been associated with
composting operations and air conditioning systems. In residences, cases of
hypersensitivity pneumonitis have been associated with contamination of a
sonic humidifier by the bacterium,
Klebsiella oxytoca
and a
Bacillus subtillus
infestation of bathroom wood materials disturbed during remodeling.
The relationship between thermophilic actinomycete exposure and
hypersensitivity pneumonitis appears to be due to very high exposures to
small-diameter spores. Actinomycete spores have aerodynamic diameters in
the range of 1 to 1.5
m, well in the respirable range wherein spores have a
high probability of deposition in the lower respiratory airways and lung
tissue (where hypersensitivity pneumonitis pathology and immediate symp-
toms occur). This is consistent with mold species as well. Molds which
produce small spores, such as
µ
spp. have
also been identified as causes of hypersensitivity pneumonitis. The lower
bacteria (which consist of small aerodynamic diameter cells) have also been
identified as causing hypersensitivity pneumonitis.
The aerodynamic size phenomenon may be a significant one in terms of
the potential role of bacteria in causing hypersensitivity diseases such as
chronic allergic rhinitis and asthma. In both cases, disease/symptom induc-
tion is typically associated with allergens with larger aerodynamic diameters
(>2.5
Aspergillus fumigatus
and
Penicillium
m). Such allergens tend to be deposited in the nasopharyngeal and
upper respiratory airways where allergy and asthma symptoms manifest
themselves. Because of their small size, bacteria may not pose a significant
immunological sensitization and exposure risk for allergy and asthma.
µ
As indicated previously, endotox-
ins are released into the environment when Gram-negative bacteria undergo
lysis or disruption of their outer membranes. Endotoxins are potent cytotoxic
compounds that can kill pulmonary macrophages and affect the immune
responses of neutrophils and basophils. In addition, they stimulate cell divi-
sion and cause membrane dysfunction. Clinical manifestations of inhalation
exposure include fever, increased respiratory rate, chest tightness, airway
hyperreactivity, and bronchitis.
f.
Endotoxins and humidifier fever.
