Misdiagnosed Salmonella Septicemia and Endarteritis Due
to a Lactose-fermenting Strain
Bacteriologic and Epidemiologic Considerations
RICHARD K. PORSCHEN, PH.D., DEVON HALE, M.D., AND ZELMA GOODMAN, MT (ASCP)
Porschen, Richard K., Hale, DeVon, and Goodman, Zelma:
Misdiagnosed Salmonella septicemia and endarteritis due to a
lactose-fermenting strain. Bacteriologic and epidemiologic
considerations. Am J Clin Pathol 68: 416-419, 1977. In a
case of septicemia and endarteritis the causative agent was
initially misidentified. The Salmonella had atypical biochemical
properties and was resistant to numerous antibiotics. Therapy
with gentamicin and cephalothin failed to eliminate the
organism. Identification of the organism as a lactosefermenting Salmonella serotype typhimuriutn var. Copenhagen
was confirmed. The possible dissemination of the isolate
from Brazil was analyzed by serologic studies of family members and friends. (Key words: Septicemia; Endarteritis;
Lactose-fermenting Salmonella.)
IN DIAGNOSTIC BACTERIOLOGY the evolution of
atypical strains presents a real challenge. Little is
known about the distribution of such organisms in
nature and their importance as human pathogens.
Atypical, lactose-fermenting Salmonella strains resistant to many antimicrobial agents were reported
endemic in Sao Paulo, Brazil. 3 However, there is little evidence implicating similar strains as the cause of
disease in the United States. Since the recognition of
Salmonella in fecal specimens depends heavily on
screening for lactose-negative colonies, lactose-fermenting variants are easily overlooked. This report
describes pertinent clinical, bacteriologic and epidemiologic features in a case of septicemia and
endarteritis due to a lactose-positive Salmonella
that was initially misdiagnosed.
Received August 30, 1976; accepted for publication September 27,
1976.
Address reprint requests to Dr. Porschen: Director, Microbiology
and Immunology, Veterans Administration Hospital, 5901 East
Seventh St., Long Beach, California 90822.
416
Microbiology Section, Laboratory Service and Division
of Infectious Diseases, Medical Service, Veterans
Administration Hospital, Long Beach, California, and
Department of Medicine, School of Medicine, University
of California, Irvine, California
Report of a Case
A 52-year-old white woman had been in good health
until mid-November 1975, when suprapubic, cramping,
abdominal pain, radiating to her back and legs, developed. She was anorexic, lost 8 pounds in weight
and noticed occasional episodes of feeling warm or
flushed. On December 5 a physical examination and
laboratory evaluation disclosed no abnormality except
an erythrocyte sedimentation rate of 50 mm/hr. The
patient returned a week later with progressive abdominal pain, for which she was given codeine. On
December 25 she came to the emergency room because
of a marked increase in abdominal pain, a three-week
history of constipation, and progressive weight loss.
The patient was very thin. On admission she appeared chronically ill, with moderate abdominal pain.
She was afebrile. Cardiac examination disclosed no
abnormality except a grade II/V I systolic ejection murmur of the left sternal border. A large, nontender pulsatile mass in the mid-epigastric area was palpable.
Bowel sounds were active. Pulses in the lower extremities were 1+ and equal.
On the second hospital day, a large pseudoaneurysm
was removed from the abdominal aorta and a dacron
graft was placed just below the left renal artery to the
bifurcation of the aorta. Cultures from the aneurysm
grew a Gram-negative rod, initially identified asEntero-
417
CASE REPORTS
Vol. 68 • No. 3
Table I. Biochemical Characteristics and Antimicrobial Susceptibility of the Atypical Salmonella
Initial Reactions*
Glucose (acid and gas)
Lactose
Indole
Hydrogen sulfide
Lysine decarboxylase
Ornithine decarboxylase
Citrate
Motility
Phenylalanine deaminase
Rhamnose
Confirmatory Reactions
Voges-Proskauer
Arginine dihydrolase +
Malonate
Dulcitol
+
Urease
-
Antimicrobial
Susceptibility^
Ampicillin
R
Cephalothin
E
Chloramphenicol
S
Tetracycline
R
Kanamycin
R
Gentamicin
S
Colistin
S
Gantrisin
R
Carbenicillin
R
Trimethoprimsulfamethoxazole S
* Reactions characteristic of Eillerobacter aerogenes.
+ This reaction was positive in certain media—e.g., lysine iron agar.
t Disk diffusion tests by modilied Bauer-Kirby tests: S = sensitive. E = equivocal, and R = resistant.
bacter aerogenes. The patient was treated with chloramphenicol for ten days. On the fourteenth hospital
day the antibiotic was changed to gentamicin. That
evening the patient had hematochezia and became
hypotensive. Emergency operation disclosed a leak at
the site of the anastomosis and a small-bowel fistula.
The dacron graft was removed, an axillary-femoral
bypass graft was placed with right femoral-to-left
femoral extension, and the aortic duodenal fistula was
repaired. Cultures from the aorta, peritoneum and incision all grew the same Gram-negative rod initially
isolated.
The patient remained febrile despite continuous administration of gentamicin. On the thirty-first hospital
day she had a hot, swollen, painful ankle, and a blood
culture was positive for the Gram-negative rod. On
the basis of favorable in-vitro synergy studies, cephalothin was added to the gentamicin. The patient became
afebrile, and the ankle returned to normal. On hospital
day 41 she again noticed bloody stools, and on day
44 a small pulsatile left upper quadrant mass was
detected. At operation the proximal stump of the aorta
and the left renal artery were found to be necrotic.
A small aortic duodenal fistula was repaired, with
further resection of the aortic stump, and a left nephrectomy was performed. Cultures of material from the
aorta and para-aortic areas were again positive.
On the day 47 the Gram-negative rod was reidentified
as a lactose-positive Salmonella Group B. Cultures of
stool, urine, sputum and duodenal material all grew
Salmonella, Group B. Gentamicin and cephalothin
were discontinued and chloramphenicol administration
was reinstituted. Within ten days all cultures were
negative, and the patient became afebrile. On the
hospital day 65 she had an uncomplicated cholecystectomy.
On the hospital day 76 the patient awoke unable to
move her legs, which were cold, numb, and pulseless.
A shunt revision was performed, with removal of a clot
from the bypass graft. On the day 85 she experienced
a similar episode of painful, cold, lower extremities,
and a second axillo-femoral graft was placed on the
left. After 38 days of therapy, chloramphenicol was
replaced by trimethoprim-sulfamethoxazole. The patient was discharged on the hundredth hospital day,
to be followed as an outpatient.
Bacteriology
The organism was initially cultured from aneurysms,
peritoneum, blood, sputum, and urine. The biochemical reactions observed on r/b enteric identification
media (Diagnostic Research, Inc., Roslyn, New York)
were typical for Enterohacter aerogenes. Table 1 lists
the initial reactions, which included acid production
from lactose and no hydrogen sulfide (H2S) production.
It was only by a bacteriologist's study, analyzing
carbenicillin-resistant Enterohacter species with additional tests, that the correct identification was discovered. Confirmatory biochemical studies that led
to the identification of Salmonella enteriditis were
negative reactions for Voges-Proskauer, malonate, and
urease, while arginine dihydrolase and dulcitol tests
were positive. Subsequent serologic studies led to the
identification of Salmonella, Group B. At this time,
additional cultures of stool and duodenal aspirate were
obtained and grew the organism. Cultures of material
from the gallbladder were negative. Later, the Center
for Disease Control (CDC) confirmed the isolate as
Salmonella enteriditis, serotype typhimurium,
var.
Copenhagen.
On standard selective and differential enteric media
the unusual strain of Salmonella appeared as a nonmucoid, lactose-positive colony resembling Escherichia coli, Citrobacter, or Enterohacter species.
It showed unusual reactions in certain media that determine H 2 S production, e.g., triple-sugar iron agar and
418
PORSCHEN, HALE AND GOODMAN
Table 2. Serologic Evaluation of Patient
Contacts for Determination of Source
of Lactose-fermenting Salmonella
A.J.C.P. • September 1977
were nontypable by bacteriophage tests, and 18 of 120
strains had a similar antibiogram. 3
Stool cultures from the patient's husband, son and
two friends were negative. However, the possibility
Titers by Tube
of intermittently positive carriers cannot be ruled out
Agglutiination*
until 12 stool cultures are negative over a one-year
Senimt
0 Antigen
H Antigen
period and a final duodenal aspirate culture is negative. 7
Serologic tests were performed on the patient, her
HM
1:640
1:40
husband,
her stepson, and his two friends. Employing
PM, Sr.
<1: 10
<1:10
PM, Jr.
<1 :I0
1:80
the patient's isolate somatic or O and flagella or H
BT
<1 :10
1:40
antigens were prepared. 2 Table 2 presents tube aggluEJ
<1 :10
<1:10
tination reactions using these antigens. The patient
* Employing patient's isolate for antigen preparation.
showed a high titer to the somatic antigen (1:640) and a
t HM = patient: PM.Sr. = husband: PM. Jr. = stepson; BTand EJ = stepson's friends.
1:40 titer with the flagella antigen. The other subjects
all had negative titers to somatic antigen (<1:10). With
Kligler's iron agar. No H 2 S production was demonstrated, probably because the large amount of acid
the flagella antigen, the son had a 1:80 titer and BT
production inhibits the reaction. 8 However, in other
had 1:40 titer. The husband and EJ were negative
H 2 S-indicating media, such as lysine iron agar,
(<1:10).
Hektoen enteric agar and bismuth sulfite agar, the
Discussion
reaction was positive.
Results of antimicrobial disk susceptibility studies
In this case Salmonella endarteritis probably deare presented in Table 1. The organism was resistant
veloped following transient bacteremia associated with
to numerous antibiotics. Susceptible tests were obintestinal carriage of the organism. The aortic aneuserved for only chloramphenicol, gentamicin, colistin,
rysm necessitated a complex series of surgical proand trimethoprim- sulfamethoxazole.
cedures with a dacron prosthesis and prolonged antiGenetic studies were performed to determine
biotic therapy to achieve a cure. Kanwar and colwhether the lactose fermentation property wsa due to
leagues 4 recently reported a case of abdominal aortic
a plasmid or episome. (Work was done by R. T. Libby
aneurysm secondary to Salmonella infection and reand D. T. Chester, Department of Microbiology,
viewed 22 other cases, among which there were only
California State University, Long Beach.) No transfer
three long-term survivors.
of extrachromosomal markers was demonstrated by
The unusual biochemical properties of the Salconjugation studies employing related organisms as
monella isolate led to initial misidentification and subrecipients.
sequent antibiotic mismanagement. In our case gentamicin alone and in combination with cephalothin did
Epidemiology
not eradicate the organism, although it was susceptible
by
in-vitro tests.
A thorough family history of the patient revealed
The recognition of lactose-fermenting Salmonella in
that her stepson (PM, Jr.) and two of his friends (BT
stool specimens is nearly impossible with isolation
and EJ) had spent a year in Brazil during 1972-1973.
media that utilize lactose fermentation as the only difThe patient and her husband (PM, Sr.) had subsequent
ferential marker. Recommendations for detecting laccontact with their son and BT only once; approximately
tose-fermenting Salmonella 1,3 suggests a medium that
20 months after their return from Brazil and eight
is highly selective for Salmonella and contains an H 2 S
months prior to the patient's illness. During the visit
indicator—i.e., bismuth sulfite agar. Another method
they had remained overnight and had eaten dinner preis to inoculate multiple lactose-positive colonies into
pared by the friends.
lysine iron agar or peptone iron agar for detection of
Although the son and his friends had not been ill
H 2 S production.
recently, two of them (PM, Jr., and BT) did recall
The difficulty in recognizing lactose-fermenting Salexperiencing nausea, fever and vomiting while in Brazil.
monella supports concerted efforts to study and control
Additionally, they had travelled to Sao Paulo and had
its spread. Evidence that our isolate disseminated from
lodged with one of the friend's uncles who travelled
Brazil is based on biochemical and serologic studies,
regularly to Sao Paulo.
as well as antimicrobial susceptibility patterns. A
Our isolate was identified as the serotype common
genetic study on the nature of the lactose-fermenting
to the Sao Paulo area. Although antibiogram and
property revealed that it was not transferred in unbacteriophage studies (performed by Dr. J. J. Farmer
complicated conjugation experiments. This was similar
at CDC) were inconclusive, some strains from Brazil
CASE REPORTS
Vol. 6X • No. 3
5
to the findings of Le Minor and colleagues, in which
the lactose-fermenting property of the Sao Paulo
strains could be mobilized only by introducing a wellcharacterized E. coli plasmid.
Epidemiologic studies also revealed interesting findings. The son and BT (H titers of 1:80 and 1:40,
respectively) recalled illnesses while in Sao Paulo and
had entertained the patient and husband eight months
prior to her illness. It has been observed that flagella
antigen titers remain consistently higher than somatic
antigen titers. 6 There is no common flagella antigen
between S. typhi and S. typhimurium, var. Copenhagen, excluding elevated titers due to vaccination.
However, many commonly occurring Salmonella
strains do have cross-reacting antigens and may be
encountered by man without manifestation of disease.
Since no data regarding the significance of titers in
Salmonella carriers are available, we can only speculate that the lactose-fermenting S. typhimurium, var.
Copenhagen, was brought from Brazil, perhaps in a
carrier state, by the stepson or his friend.
419
References
1. Blackburn BO, Ellis EM: Lactose-fermenting Salmonella from
dried milk and milk-drying plants. Appl Microbiol 26:672674, 1973
2. Edwards PR, Ewing WH: Identification of Enterobacteriaceae.
Third edition. Minneapolis, Burgess Publishing Company,
1972
3. Falcao DP, Trabulsi LR, Hickman FW, et al: Unusual
Enterobacteriaceae: Lactose-positive Salmonella typhimurium which is endemic in Sao Paulo, Brazil. J Clin
Microbiol 2:349-353, 1975
4. Kanwar YS, Malhotra V, Anderson BR, et al: Salmonellosis
associated with abdominal aortic aneurysm. Arch Intern Med
134:1095-1098, 1974
5. Le Minor L, Coynault C, Pessoa G: Genetics of unusual lactose-fermenting Salmonella endemic in Sao Paulo, Brazil.
Ann Inst Pasteur 125A:261-285, 1974
6. Morgan HR: The enteric bacteria, Bacterial and Mycotic Infections of Man. Fourth edition. Edited by Dubos RJ,
Hirsch JG. Philadelphia, J. B. Lippincott, 1965, pp 610648
7. Musher DM, Rubenstein AD: Permanent carriers of nontyphosa
Salmonellae. Arch Intern Med 132:689-872, 1973
8. Veron M, Gasser F: Sur la detection de I'hydrogene sulfure
produit par certaines Enterobacteriacees dans les milieux dits
de diagnostic paride. Ann Inst Pasteur 105:524-534, 1963