Postmortem Bacteriology and Pneumonia in a Mentally
Retarded Population
ANTHONY P. POLEDNAK, PH.D.
Polednak, Anthony P.: Postmortem bacteriology and
pneumonia in a mentally retarded population. Am J Clin
Pathol 67: 190-195, 1977. Postmortem pathologic and
bacteriologic reports were analyzed for 237 deaths occurring at
a large institution for the mentally retarded from 1958 to 1973.
Bronchopneumonia, aspiration pneumonia, and lipid pneumonia were frequently reported at autopsy, and in a total of
146 cases (61.6%) at least one type of pneumonia was reported.
Postmortem bacteriologic cultures in a smaller group revealed
high recovery rates of staphylococci (coagulase-positive),
hemolytic streptococci, and gram-negative bacilli in throat and
lung cultures. Enteric aerobic gram-negative bacilli were
particularly frequent, along with yeast (Candida albicans).
The institutionalized retarded appear similar to other hospitalized populations, in that a large proportion of hospitalacquired respiratory infections is related to aerobic gramnegative bacilli. The high frequency of aspiration and its
sequelae in this population is unusual, however, and postmortem bacteriologic findings appear consistent with those of
antemortem studies of cases of aspiration pneumonia. (Key
words: Postmortem bacteriology; Aspiration pneumonia;
Gram-negative bacteria; Lipoid pneumonia; Nosocomial
respiratory infections.)
PNEUMONIA AND other respiratory diseases continue to be the major cause of death in institutionalized
mentally retarded persons. 13,16 ' 18 ' 19 Autopsy data on
specific types of pneumonia in these populations have
apparently not been reported, and antemortem or postmortem microbiologic data are also lacking. Together,
these data could be of great value in identifying diseases
and probable causal agents, upon which therapeutic
and prevention programs could concentrate.
The present retrospective study describes the
frequencies of specific types of pneumonia and postmortem bacteriologic findings in an autopsy population
of institutionalized mentally retarded persons.
Received November 11, 1975; received revised manuscript
February 16, 1976; accepted for publication February 16, 1976.
Address reprint requests to Dr. Polednak at his present address:
Center for Human Radiobiology, Argonne National Laboratory,
Argonne, Illinois 60439.
Birth Defects Institute,
State Department of Health,
Albany, New York
Materials and Methods
The Ontario Hospital School at Orillia is the oldest
and largest institution for the mentally retarded in
Ontario, Canada. Records of deaths of patients were
available for 1958 to 1973. The total population varied
between about 2,900 and 2,100 per year. The total population at risk for the entire period could not be accurately estimated; the population was rather stable, however, with relatively few new admissions each year, as
reported for other similar institutions. 17 A trend toward
aging of the population, as reported elsewhere, 17 was
also evident; by 1970, an at-risk population less than 5
years of age was virtually nonexistent.
From the centralized record system of the institution,
records were located for 676 of the total of 707
deaths that occurred from 1958 to 1973. These records
included case histories and all medical information
available, including death certificates and autopsy
reports. Autopsy reports were available for 237 of
the 246 performed. Pneumonias and other respiratory
diseases reported at autopsy were coded according to
the International Classification of Diseases, Eighth
Revision (World Health Organization, 1965).22 The
sex composition, average age at death, and intellectual
status (level of retardation) of the autopsy series were
very similar to those of the entire group of 676
decedents. Most autopsies were performed in the
morgue of the institution.
Of the 237 autopsies, at least one bacteriologic
culture report was avilable for 113 (47.7%). These
included 56 nose and throat, 26 bronchus or lung,
and 71 heart blood cultures. Cultures were examined
by standard technics (Gram's method and coagulase
test); cultures for anaerobic bacteria were not done.
190
191
PNEUMONIA IN THE MENTALLY RETARDED
Vol. 67 • No. 2
Chest x-ray reports were examined for all deaths
occurring during a five-year period (1969-73), and reports for 56 autopsied deaths were obtained. Reports
of chest x-rays of individuals with pneumonia reported
at autopsy obtained less than a year prior to death
were analyzed. Reports of the most recent medical
examinations, especially the section pertaining to the
lungs, were also examined.
Results
Pneumonia
Table 1 shows the frequencies of specific types of
pneumonia reported at autopsy. Bronchopneumonia
was most frequently reported (32.9%), followed by
aspiration pneumonia (16.0%). Other types of pneumonia were relatively infrequent. The occurrence of
lipid pneumonia in 15 autopsies (6.3%) is noteworthy,
in view of the high frequency of aspiration pneumonia. In a total of 146 cases (61.6%), at least one
type of pneumonia was reported.
In addition to the 38 cases of aspiration pneumonia,
evidence of aspiration was obtained in another 22
autopsies. Of these 22 cases, seven involved pneumonia (five bronchopneumonia, one bacterial, and one
lipid), five involved bronchitis or emphysema, and four
involved pulmonary collapse (atelectasis, a feature of
aspiration pneumonia). It is probable that aspiration
often preceded (and was causally related to) these
pulmonary conditions; this was indicated by the reporting of "old" or "chronic" aspiration pneumonia along
with other pulmonary conditions of apparently more
recent development.
The pathologic features of aspiration pneumonia included edema, hemorrhage (with hemosiderin-filled
macrophages), patchy atelectasis, and some necrosis,
as described in previous studies.4'6 Aspiration or
aspiration pneumonia was mentioned in autopsy reports of only five of 15 cases with lipid pneumonia.
The pathologic features were similar to those for
aspiration pneumonia (patchy atelectasis, edema and
hemorrhage); fat-filled macrophages (with positive
histologic staining for fat) were often reported, along
with an inflammatory process and vacuolated cells.
Pleurisy was also frequently found at autopsy—
i.e., in 45 of 237 cases, or 19.0%. Fibrinous pleurisy is
most commonly due to bacterial pneumonia, but
pneumonia may also cause effusion.21 Only ten of the
45 autopsy reports describing pleurisy mentioned
effusion. Effusion was apparently related to esophageal
ulcer, secondary carcinomatous deposits in the lung
(from an ovarian tumor in one case, and a fascial
fibrosarcoma in another case), myocardial infarction,
hemothorax with aspiration (asphyxia and pulmonary
Table 1. Types of Pneumonia Reported at Autopsy
Male
Type of Pneumonia
(ICD Code)
Female
Total
No.
%
No.
%
No.
%
22
0
5
0
34
8
18.3
0.0
4.2
0.0
28.3
6.7
16
1
11
1
44
3
13.7
0.9
9.4
0.9
37.6
2.6
38
1
16
1
78
11
16.0
0.4
6.8
0.4
32.9
4.6
17 Other chronic interstitial pneumonia
6
5.0
9
7.7
15
6.3
19.2 Lipid pneumonia
7
5.8
8
6.8
15
6.3
otal with one or more
69
57.5
77
65.8
146
61.6
480-486 Pneumonia
* Aspiration
480 Viral
481, 482 Bacterial
484 Acute interstitial
485 Bronchopneumonia
486 Unspecified
Total number of autopsies
120
117
237
Mean age at death (years)
15.6
24.5
20.0
* There is no specific ICD code for aspiration pneumonia.
hemorrhage), and pneumonia (three cases). These are
recognized causes of pleural effusion; tuberculous
pleural effusion could also be involved, but direct
evidence may be difficult to obtain.21 Only one of the
45 autopsy reports describing pleurisy mentioned
tuberculosis; this was "arrested" tuberculosis
(bilateral, upper lobe) with pleural adhesions in a 65year-old man.
Postmortem bacteriology
Microorganisms were recovered from cultures from
at least one site (nose and throat, bronchus or lung,
and heart blood) in 94 (83.2%) of 113 cases, excluding "contaminants" in heart blood cultures. Table
2 shows the frequencies of postmortem recoveries of
microorganisms from the three sources. Staphylococci
were found frequently in the nose and throat, and
somewhat less frequently in bronchus or lung. Noteworthy are the high recovery rates of E. coli and
Klebsiella-Aerobacter species, especially in the
bronchus or lung. Candida albicans was also relatively frequent in nose and throat, and bronchus or
lung, cultures. Positive cultures were relatively less
frequent from heart-blood samples; only 40 of 71
cultures (56.3%) were positive, and the pattern of
microorganisms recovered was somewhat different
from those at the other sites (i.e., coagulase-positive
staphylococci were less frequent and coagulase-negative staphylococci more frequent).
Of the 26 cases in which cultures from the lung or
bronchus were obtained, 17 reportedly had evidence
of pneumonia at autopsy. A total of 27 microorganisms
was recovered from these 17 cases, or 1.6 organisms
POLEDNAK
192
Table 2. Recovery of Microorganisms from
Postmortem Cultures
Nose
and
Throat
(N = 56)
Bronchus
or
Lung
(N = 26)
Heart
Blood
(N = 71)
No.
%
No.
%
No.
%
Staphylococci
Coagulase-positive
Coagulase-negative
32
3
57.1
5.4
9
1
34.6
3.8
4
10
5.6
14.1
Streptococci
Beta-hemolytic
Alpha-hemolytic
17
10
30.4
17.9
6
5
23.1
19.2
7
7
9.9
9.9
Escherichia coli
8
14.3
8
30.8
6
8.5
Enterobacterial species
3
5.4
1
3.8
1
1.4
Klebsiella-Aerobacter
species
6
10.7
6
23.1
5
7.0
Pseudomonas species
2
3.6
0
0.0
3
4.2
Proteus species
3
5.4
2
7.7
3
4.2
11
19.6
3
11.5
2
2.8
Miscellaneous
2
3.6
3
11.5
5
7.0
Contaminants
0
0.0
0
0.0
9
12.7
No growth
2
3.6
0
0.0
22
31.0
Candida albicans
Ratio of number of
organisms to number of
cultures
1.7:1
1.7:1
0.7:1
per culture. The microorganisms involved were:
coagulase-positive staphylococci in five (29.4%); E.
coli in five (29.4%); Klebsiella in four (23.5%); alphahemolytic streptococci in three (17.6%); staphylococci
coagulase-negative, Proteus, Achromobacter, other
enterobacteria, Haemophilus, and unspecified gramnegative organisms in one case (5.9%) each.
Table 3 shows the bacteriologic findings in 21
cases with aspiration (N = 12) or aspiration pneumonia
(N = 9) reported at autopsy. Enterobacteria (£. coli,
Proteus mirabilis, and Klebsiella) and yeast
(Candida albicans) are evident. Hemolytic streptococci {viridans and pyogenes) were also frequently reported.
Chest X-ray Reports
As mentioned above, chest x-ray reports were
available for 56 autopsied deaths (1969-73). Chest
x-ray reports were obtained for 21 cases with aspiration pneumonia reported at autopsy, but only 12 of
these were recent {i.e., within a year of death).
Findings reported were negative for most of these,
even those obtained within a few days (N = 3), two
weeks (N = 1), and a month (N = 2) of death. In
A.J.C.I'. • i-ebruury 1977
one case "resolved pneumonitis or cardiac failure"
(with Down's syndrome) was found one month before death, and another individual had "interstitial
disease of both lungs" found five months before
death, but no recommendation for treatment was
given. Chest x-ray or medical examination reports
made mention of rales in three of the 12 cases.
One person who had lipid pneumonia reported at
autopsy had had a chest x-ray two weeks before
death; crepitant rales in the lower lung regions had
been detected, but were not attributed to an infectious
process.
Of 11 persons with bronchopneumonia reported at
autopsy, seven had had chest x-rays taken within a
year of death. One report, about a month before death
(from bronchopneumonia), indicated a stable infiltration of the left lung, with no recommendation for
treatment; in this case bronchopneumonia and aspiration of bile were reported at autopsy. The other six
individuals, including one who had bronchopneumonia
and aspiration found at autopsy, had been reported as
without evidence of disease. This included a person
who had had an x-ray taken three days before death
with "no sign of pneumonia in either lung" who died
from bronchopneumonia (certified as the underlying
cause of death and reported at autopsy).
It should be noted that tuberculosis did not appear
to be frequent in this population. Tuberculin test
results were noted on almost all chest x-ray reports,
along with diagnostic impressions regarding tuberculosis. Of the 56 autopsied deaths (1969-73) with
chest x-ray reports, three early reports (from the
1950's) mentioned positive tuberculin skin tests, and
two of these reported tuberculosis (old and arrested,
with pleurisy). One other report mentioned a positive
tuberculin test in 1970, two years before death, but no
diagnosis of tuberculosis was mentioned, and the
death was attributed to aspiration pneumonia and
intestinal obstruction. Chest x-ray reports for nonautopsied deaths (1969-73) were also examined for
evidence of tuberculosis. Of 37 cases in which roentgenograms had been obtained within a year of death,
tuberculosis was reported in none, one person had a
positive tuberculin test but "no evidence of pulmonary
tuberculosis" was reported. Of 47 other non-autopsied
deaths with chest x-ray reports on file, two had had
minimal, arrested pulmonary tuberculosis reported
some years before death. Parenthetically, it was
found that only two of the 676 death certificates
mentioned tuberculosis (LCD. codes 010-019), and
these were for relatively old persons (62 and 65 years
old at death). One of these two individuals had an
autopsy, and is mentioned above with reference to
pleurisy.
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PNEUMONIA IN THE MENTALLY RETARDED
Vol. 67 • No. 2
Discussion
Autopsy reports were examined to evaluate the
prevalences of specific types of pneumonia at death.
Since autopsies are not representative of all deaths,
these data must be interpreted with caution. Bronchopneumonia was found in about a third of all autopsies
(Table 1), which is similar to the figure reported
from a large Veterans Administration hospital.14
The finding that 60 of 237 autopsies (25.3%) made
mention of aspiration suggests that this is a significant
potential health problem in this population. These 60
cases included 38 with aspiration pneumonia; in the
others, pneumonia was sometimes reported along with
aspiration, but the relationship was apparently unclear.
Cases of lipid pneumonia also undoubtedly involved
aspiration, although it was mentioned in only five of
15 cases. In "exogenous" lipid (lipoid) pneumonia,
animal fats are introduced into the lung by aspiration (often of regurgitated food).7 Phagocytosis of the
fat by alveolar macrophages occurs, as in the present
case where fat-filled macrophages were found histologically.
The true incidence of aspiration and its sequelae
is difficult to determine, since postmortem examination
may reveal only nonspecific results of aspiration.8
In 11 of the 38 cases of aspiration pneumonia,
bronchopneumonia was also reported; other cases
of bronchopneumonia may have been related to aspiration, which was unrecognized. The rather large number
of cases of "other chronic interstitial pneumonia"
(Table 1) suggests the possibility of aspiration as a
precursor; the cellular infiltration and increase in
fibrous tissue in interstitial pulmonary disease suggest
the possibility of unrecognized lipoid pneumonia, but
this is speculative.
Chest x-ray reports on a smaller group with pneumonia found at autopsy suggested that bronchopneumonia and aspiration pneumonia often develop
rapidly, with few recognized symptoms. This is in
agreement with findings in a large veterans' hospital,
in which bronchopneumonia was often associated with
aspiration, and was usually insidious, with few
symptoms and a rapid course.14 Arms and associates1
did find classic bilateral diffuse infiltration in about
25% of cases of aspiration pneumonia, which suggests
that roentgenograms of the chest may be of some
value in detection of aspiration pneumonia. Rales
were reported to occur in three of 12 cases of
aspiration pneumonia, and in the one case of lipid
pneumonia. Diffuse rales are reportedly common in
patients who have aspiration pneumonitis.6
Tuberculosis did not appear to be frequent in this
population, according to death certificates, autopsy
Table 3. Postmortem Cultures in Cases with Aspiration
or Aspiration Pneumonia (N = 21)
Streptococci
Staphylococci
E. coli
Proteus mirabilis
Achromobacter
Klebsiella aerobacter
Hemophilus
Bacterium anitratum
Candida albicans
Sterile
Number of cultures
Ratio of number of
organisms to number of cultures
Nose,
Throat
No.
Bronchus,
Lung
No.
Heart
Blood
No.
4
3
1
1
0
1
0
0
2
0
6
12/6 = 2:1
2
1
2
1
1
0
1
0
1
0
8
9/8 = 1.1:1
4
1
3
1
0
1
0
2
1
2*
12
13/12 = 1.1:1
* Two of these were in cases with aspiration alone.
reports, and chest x-ray reports. Similarly, Richards
and Sylvester19 reported that tuberculosis has been
an insignificant cause of death in mental deficiency
institutions in England since 1950. Changes in the age
structure of institutions for the retarded,17 however,
could be involved; the highest mortality rate for
tuberculosis is in the first few years of life, and the
proportion of institutionalized retarded young children
has declined considerably.
Since postmortem bacteriologic cultures were not
available for all cases, these findings must also be
interpreted with caution. The 56.3% positive rate
for heart blood cultures agrees closely with the 53%
rate in a recent study.11 As in previous studies,10
postmortem swabs from the throat almost always
showed bacterial growth (Table 2). Gram-positive
organisms (staphylococci and streptococci) predominated. These are common commensals of the
upper respiratory tract, but coagulase-positive staphylococci are regarded as potential pathogens, and were
frequently recovered from nose and throat cultures.
Enteric gram-negative bacilli, however, are rarely
found in the oropharyngeal flora of non-hospitalized
persons.915
The bronchi and lungs are sterile when healthy,
and postmortem invasion of bacteria is unlikely1011;
hence, lung cultures may be of particular importance.
The recovery of staphylococci in bronchus or lung
cultures is not unexpected, in view of their high
invasion rate10 and occurrence in debilitated hospitalized patients. Several studies, reviewed by Pierce
and Sanford,15 have shown that autopsy cultures of
human lungs provide bacterial species similar to those
cultured in the pharynx. Tables 2 and 3 show this
similarity. Coagulase-positive staphylococci, for
194
A.J.C.P. . l-ebruary 1977
POLEDNAK
example, were frequent in both nose (and throat)
and bronchus or lung cultures (Table 2). Aerobic
gram-negative bacilli are also frequent in cultures from
both regions (Table 2). In hospitalized patients the
oropharynx is commonly colonized with gram-negative
aerobes, which cause many nosocomial respiratory
infections.9,15 Pierce and Sanford15 have estimated that
about half of all pneumonias acquired within a hospital
setting are due to aerobic gram-negative bacilli. The
present findings, albeit based on postmortem cultures
alone, are not inconsistent with this estimate.
The high postmortem recovery rate of certain gramnegative bacilli and other microorganisms in this
study could be correlated with the high frequency of
aspiration pneumonia in the population (Table 1).
E. coli and related organisms (other enterobacteria,
such as Aerobacter) are frequent isolates in the
upper respiratory tracts of young children, presumably regurgitated from the alimentary tract. E.
coli reportedly has a high invasion rate,10 and in the
present study was frequently recovered in the
bronchus or lung, as well as the nose and throat
(Tables 2 and 3). Antemortem cultures from patients
with aspiration and aspiration pneumonia1'2,6'12 have
shown E. coli and Klebsiella, along with staphylococci.
Anaerobic bacteria are also common pathogens in
aspiration pneumonia, however, and anaerobic cultures were not available in the present study. On
the other hand, aerobic enteric gram-negative bacilli
are particularly common in patients with hospitalacquired aspiration pneumonia.12 Thus, the present
findings may be indicative (at least in part) of hospitalacquired aspiration pneumonia in this population
(Table 3), within the limitations of the validity of
postmortem cultures.
Recent reports20 suggest possible involvement of
Candida albicans in pneumonia related to aspiration
of pharyngeal contents. The postmortem recovery of
Candida in patients with evidence of aspiration (Table
3), as well as in other cases (Table 2), is noteworthy in this regard.
The presence of hemolytic streptococci in bronchus
or lung cultures is noteworthy. Although streptococcal pneumonia has been rare since the introduction
of penicillin, recent outbreaks have been reported to
occur in institutionalized populations {i.e., military
recruits).3 Systematic records of antibiotic treatment
were not available, but chemotherapy or antibiotic
treatment prescribed within 48 hours of death does not
appear to influence the total postmortem recovery of
microorganisms significantly.11
Perhaps the most significant finding in this population is the high frequency of aspiration and aspiration pneumonia, and the postmortem bacteriologic
culture data apparently consistent with this. The high
frequency of aspiration and its sequelae is not unexpected in institutionalized populations. In institutionalized elderly patients,14 aspiration pneumonia is a
frequent finding at autopsy. States of impaired consciousness, related to epilepsy or cerebral dysfunction,
are known risk factors for aspiration.1,2,4,5 The occurrences of epilepsy, cerebral palsy, encephalitis, and
various congenital malformations of the digestive tract
in retarded populations suggest that they may be at
high risk for aspiration. Prolonged bed rest, reducing
drainage of tracheobronchial secretions, may be an
additional factor. As Richards and Sylvester19 have
observed, severely retarded patients with infrequency
and inefficiency of throat-clearing, coughing and noseblowing could be at high risk for respiratory disease,
including aspiration. Poor personal hygienic habits
could also facilitate the spread of infection, but this
requires further study.
Proper positioning in bed to facilitate drainage of
tracheobronchial sections,5 and special feeding procedures1'5 may be useful measures in prevention of
aspiration pneumonia in institutionalized retarded
populations. Observation, recording and modification
of personal hygienic behavior (coughing, nose-blowing, throat-clearing, and washing) could also be considered. Periodic chest x-rays, collection of sputum
to be examined for evidence of lipoid pneumonia,
and transtracheal aspiration of material for culture
for gram-negative microorganisms (including
anaerobes) would be useful in early detection of
aspiration and its sequelae. Pulmonary function tests
would also be useful in studying such sequelae as
atelectasis and fibrosis.
Acknowledgments. Cooperation and assistance were provided by
Mrs. Lillian Mayor, Supervisor of Resident Record Services
at the Huronia Regional Centre (formerly the Ontario Hospital
School), Orillia, Ontario, Canada. Part of this work was supported
by a grant from the University of Waterloo, Waterloo, Ontario.
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