Bacteraemia caused by Actinobaculum schaalii: An overlooked pathogen?
Transcript of Bacteraemia caused by Actinobaculum schaalii: An overlooked pathogen?
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Correspondence: J. Sandlund, Division of Clinical Microbiology, Karolinska University Hospital and Karolinska Institute, SE-17176 Stockholm, Sweden. E-mail: [email protected], [email protected]
(Received 12 October 2013 ; accepted 31 March 2014 )
Scandinavian Journal of Infectious Diseases, 2014; 46: 605–608
ISSN 0036-5548 print/ISSN 1651-1980 online © 2014 Informa HealthcareDOI: 10.3109/00365548.2014.913306
SHORT COMMUNICATION
Bacteraemia caused by Actinobaculum schaalii: An overlooked pathogen?
JOHANNA SANDLUND 1,2 , MARTIN GLIM Å KER 1,3 , ANITA SVAHN 2,4 & ANNELIE BRAUNER 2,4
From the 1 Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institute, 2 Department of Clinical Microbiology, Karolinska University Hospital, 3 Department of Infectious Diseases, Karolinska University Hospital, and 4 Department of Microbiology, Tumour and Cell Biology, Karolinska Institute, Stockholm, Sweden
Abstract Actinobaculum schaalii is a uropathogen resistant to ciprofl oxacin and trimethoprim – sulfamethoxazole. It requires a long culture time and specifi c conditions, and is therefore easily overgrown by other bacteria and regarded as part of the normal bacterial fl ora. We review 17 cases of A. schaalii bacteraemia, demonstrating its invasive potential. A. schaalii should always be ruled out as causative agent in patients with urinary tract infection or urosepticaemia with treatment failure.
Keywords: Actinobaculum schaalii , bacteraemia , urosepticaemia , urinary tract infection
Introduction
Actinobaculum schaalii causes urinary tract infec-tions (UTI), primarily in elderly patients and in patients with urological risk factors [1 – 5]. Although sensitive to beta-lactams and the majority of other antibiotics, A. schaalii is resistant to ciprofl oxacin and trimethoprim – sulfamethoxazole [1,6,7].
A. schaalii is a Gram-positive, non-motile, facul-tative anaerobic coccoid rod that grows slowly, preferably in 5% CO 2 or an anaerobic atmosphere [1,2,8]. The tiny grey colonies show weak beta-haemolysis on blood agar and are catalase-negative [2,8]. A. schaalii is easily overgrown by other bacte-ria, and is presumably often overlooked or consid-ered a contaminant [3,9]. A. schaalii has been seen in single cases of other infections, such as spondylitis, and has also been isolated from blood, but little is known about its systemic pathogenic potential.
Methods
Between October 2009 and August 2013, the Department of Clinical Microbiology, Karolinska
University Hospital identifi ed 17 cases of A. schaalii bacteraemia. Cultures were performed using stan-dard laboratory procedures and A. schaalii isolates were verifi ed with 16S rRNA gene sequencing and catalase. Antibiotic sensitivity testing was performed with the Etest (AB Biodisk, Solna, Sweden). The study was approved by the regional ethics committee (Dnr 2014/301-31/2).
Case report
A 62-y-old man was admitted after acute onset of severe urinary problems, malaise, and diarrhoea. Trans-urethral microwave therapy (TUMT) had been performed for benign prostate hyperplasia 2 months earlier, and since then he had required the intermittent use of a urinary catheter. On admission, a palpable resistance corresponding to the urinary bladder was found, containing more than 1 l of urine. The patient ’ s body temperature was 37.8 ° C and his P-creatinine was 1100 μ M/l, indicating severe kidney damage due to post-renal blockage. A suprapubic catheter was applied; the urine contained increased levels of erythrocytes, leukocytes, and protein, but
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606 J. Sandlund et al.
the nitrite test was negative. Moderate anaemia, thrombocytosis, and hypoalbuminaemia, and an ini-tially severe hypercalcaemia, were noted. Due to a blood leukocyte count of 26.5 � 10 9 /l and C-reactive protein (CRP) of 364 mg/l, a UTI was suspected, and treatment with cefotaxime was initiated. The patient improved gradually and was discharged after 5 days, when the P-creatinine level had decreased to 304 μ M/l, leukocyte count to 15.6 � 10 9 /l, and CRP to 108 mg/l. A. schaalii, sensitive to cefotaxime and amoxicillin, was later isolated in blood culture, whereas the urine culture showed growth of the nor-mal urethral fl ora. Amoxicillin 500 mg was given for another 10 days and at follow-up 6 weeks after dis-charge the patient had recovered and the suprapubic catheter was removed.
Results
Among the 17 patients with A. schaalii bacteraemia, 14 were men and the mean age was 75 y (median 79, range 17 – 92 years). Fifteen patients (88%) had symptoms of UTI, 13 (77%) had urinary catheter support, 1 patient had a urethral stricture, and 2 patients presented with malignancies. Blood cul-tures from 6 patients revealed growth of concomitant bacteria (Table I). Out of 22 pairs of blood culture bottles, 14 (64%) aerobic bottles and 19 (86%) anaerobic bottles showed growth, this after a mean time of 52.8 h (range 29.0 – 70.8 h) and 34.6 h (range 14.9 – 53.8 h), respectively.
Urine culture was performed for 15 patients. Interestingly, A. schaalii was not isolated from any of the urine samples. When bacterial growth was detected in the blood cultures, antibiotic treatment had already been initiated in 15 patients. Eleven patients were treated with cefotaxime. For 3 of these patients, therapy was changed to ciprofl oxacin before sensitivity testing results were available (Table I). Among the tested isolates, the majority were resistant to ciprofl oxacin, and all were resistant to trimethoprim – sulfamethoxazole, while all tested strains were sensitive to benzylpenicillin, cefotaxime, and piperacillin – tazobactam.
Discussion
The majority of patients in the current study were men of relatively old mean age with symptoms indicating that the genitourinary tract was the port of entry. Underlying conditions and risk factors, such as long-term urinary catheter usage, anatomical disorders, and genitourinary cancer, were observed in 13 of the 17 patients. Why A. schaalii bacteraemia affects mainly men is unclear, but it has been
suggested that prostatic hyperplasia could be a risk factor [5]. Considering the age of the patients included in this study, the prevalence of prostatic hyperplasia is presumably high. Also, 2 of the 3 women with A. schaalii bacteraemia had risk factors including nephrostomy and urinary catheters.
None of the patients in the current study had growth of A. schaalii in urine culture. Since urine culture in 5% CO 2 and anaerobic atmosphere is only performed when clinicians specifi cally suspect A. schaalii infection and request it, this outcome is not a surprise. Morphologically, A. schaalii resembles Corynebacterium spp. and Lactobacillus spp., increasing the risk that it is considered a contaminant [3,5,9], especially in standard cultures. Additionally, the challenges when culturing A. schaalii often lead to overgrowth by other bacteria and mixed infections [9]. Analyzing 252 routine urine samples for the presence of A. schaalii by a real-time quantitative PCR, Bank et al. found that 16% were positive for A. schaalii [3], clearly indicating that A. schaalii is an often overlooked pathogen in urine samples.
A mixed bacterial fl ora was detected in the blood cultures of 6 patients. Four had simultaneous growth of either Corynebacterium sp. or slow-growing anaerobic Gram-positive round cocci. Considering the similar morphological features of A. schaalii, there is a risk of misinterpretation. The Department of Clinical Microbiology at Karolinska University Hospital receives approximately 80,000 blood cul-tures from 30,000 patients annually. Of these, 12 – 13% are positive, with growth of bacteria or fungi. Considering this high volume, it is noteworthy that only a few isolates, blood and urine included, showed growth of A. schaalii. It cannot be ruled out that some isolates have wrongly been considered con-taminants. Awareness of this pathogen therefore needs to be raised.
Since A. schaalii is resistant to ciprofl oxacin and trimethoprim – sulfamethoxazole [1,6,7], there is a substantial risk of treatment failure in UTI. Antibi-otic treatment for several weeks has been recom-mended, which also has to be taken into consideration [2,5,6,7]. A. schaalii is susceptible to beta-lactams. In our study, 15 patients (88%) were treated with beta-lactams, and the isolates showed high suscepti-bility to these compounds. As expected, a majority were resistant to ciprofl oxacin and trimethoprim – sulfamethoxazole, highlighting the need for attention when treating patients with UTIs.
In conclusion, we have demonstrated that A. schaalii has signifi cant invasive potential. We empha-size the need for special attention from both clini-cians and microbiologists in order not to overlook this pathogen. In patients with UTI or urosepticae-mia of unknown aetiology or with treatment failure,
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Bacteraemia caused by Actinobaculum schaalii 607
Tab
le I
. C
linic
al a
nd m
icro
biol
ogic
al c
hara
cter
isti
cs o
f 17
pat
ient
s w
ith
Act
inob
acul
um s
chaa
lii b
acte
raem
ia.
Age
Sex
Clin
ical
pr
esen
tati
onC
o-m
orbi
dity
/ ri
sk f
acto
rs
Con
com
itan
t fl o
ra,
bloo
d (N
o. o
f bo
ttle
s)U
rine
cul
ture
ta
ken
(fi n
ding
)O
ther
cul
ture
s ta
ken
(fi n
ding
)T
reat
men
t a R
efer
ring
de
part
men
tU
rina
ry
com
plic
atio
ns b
82M
Uro
seps
isU
rina
ry c
athe
ter
0Y
es (
uret
hral
fl o
ra)
No
CIP
® C
TX
®
CIP
Uro
logy
Yes
73M
Res
pira
tory
in
fect
ion
Uri
nary
cat
hete
rC
oryn
ebac
teri
um s
p (1
/1)
Yes
(K
lebs
iella
pn
eum
onia
e)N
PH
(M
orax
ella
cat
arrh
alis
�
Hae
mop
hilu
s in
fl uen
zae)
; an
d tr
ache
al
secr
etio
n (r
espi
rato
ry fl
ora
)
PT
Z �
ER
YE
mer
genc
y de
part
men
tY
es
81M
UT
IP
erm
anen
t ur
inar
y ca
thet
er0
Yes
(ur
ethr
al fl
ora
)N
PH
(re
spir
ator
y fl o
ra)
CT
XE
mer
genc
y de
part
men
tY
es 71
MU
rose
psis
Uri
nary
cat
hete
r,
PD
Sta
phyl
ococ
cus
epid
erm
idis
(1/
4)Y
es (
Gra
m-p
osit
ive
mix
ed fl
ora
)N
PH
(re
spir
ator
y fl o
ra)
CT
XN
euro
logy
Yes
17M
Res
pira
tory
in
fect
ion
Ure
thra
l st
rict
ure
Cor
yneb
acte
rium
sp.
(4
/4)
Yes
(ne
gati
ve)
NP
H (
resp
irat
ory
fl ora
)C
IPE
mer
genc
y de
part
men
tY
es 83
FU
rose
psis
Nep
hros
tom
yP
revo
tella
sp.
(2/
4) �
al
pha-
haem
olyt
ic
stre
ptoc
occi
(4/
4)
No
No
CT
XG
ener
al s
urge
ryY
es
77F
Unk
now
nU
rina
ry c
athe
ter
0Y
es (
Gra
m-p
osit
ive
mix
ed fl
ora
)N
PH
(M
orax
ella
cat
arrh
alis
)C
TX
Em
erge
ncy
depa
rtm
ent
Yes
57M
Fev
er,
naus
eaO
esop
hage
al
canc
erS
trep
toco
ccus
sp.
(1
/4)
Yes
(ur
ethr
al fl
ora
)N
PH
(re
spir
ator
y fl o
ra)
PT
ZO
ncol
ogy
No
79M
Unk
now
nU
nkno
wn
0Y
es (
nega
tive
)N
PH
(ne
gati
ve)
CE
F �
GE
NE
mer
genc
y de
part
men
tN
o 77
MU
rina
ry
rete
ntio
nU
rina
ry c
athe
ter
0Y
es (
uret
hral
fl o
ra)
No
CT
XU
rolo
gyY
es 74
MU
rose
psis
Pro
stat
e ca
ncer
, ur
inar
y ca
thet
er0
No
No
Unk
now
nP
allia
tive
hom
e ca
reY
es
89M
UT
IU
nkno
wn
0Y
es (
Aer
ococ
cus
sang
uini
cola
)N
oU
nkno
wn
Uro
logy
Yes
92M
Unk
now
nS
upra
pubi
c ur
inar
y ca
thet
er0
Yes
(m
ixed
fl o
ra)
No
CT
X ®
CD
XU
rolo
gyY
es
88M
Unk
now
nU
rina
ry c
athe
ter
Gra
m-p
osit
ive
cocc
i, an
aero
bic
(1/2
)Y
es (
nega
tive
)N
oC
TX
Neu
rolo
gyY
es
82M
Uro
seps
isU
rina
ry c
athe
ter
0Y
es (
nega
tive
)N
PH
(ne
gati
ve)
CT
X ®
CIP
Uro
logy
Yes
84F
Uro
seps
isU
nkno
wn
0Y
es (
uret
hral
fl o
ra)
No
CT
X ®
CIP
Infe
ctio
us d
isea
seY
es62
MU
rina
ry
rete
ntio
nU
rina
ry c
athe
ter
0Y
es (
nega
tive
)N
oC
TX
Uro
logy
Yes
M,
mal
e; F
, fe
mal
e; N
PH
, na
soph
aryn
x; U
TI,
uri
nary
tra
ct i
nfec
tion
; P
D,
Par
kins
on ’ s
dis
ease
; C
IP,
cipr
ofl o
xaci
n; C
TX
, ce
fota
xim
e; P
TZ
, pi
pera
cilli
n – ta
zoba
ctam
; E
RY
, er
ythr
omyc
in;
GE
N,
gent
amic
in;
CD
X,
cefa
drox
il; C
EF
, ce
ftaz
idim
e.
a At
the
tim
e po
int
whe
n a
bloo
d cu
ltur
e bo
ttle
is
posi
tive
and
ini
tial
Gra
m s
tain
ide
ntifi
cati
on i
s m
ade,
thi
s fi n
ding
is
com
mun
icat
ed b
y th
e m
icro
biol
ogis
t to
the
clin
icia
n, a
nd t
he p
rese
nted
in
form
atio
n on
ant
ibio
tic
trea
tmen
t w
as g
iven
. b I
nclu
ding
sym
ptom
s fr
om t
he u
rina
ry t
ract
, re
ferr
als
from
the
uro
logy
dep
artm
ent,
and
co-
mor
bidi
ties
and
ris
k fa
ctor
s su
ch a
s ur
inar
y ca
thet
er,
neph
rost
omy,
and
pro
stat
e ca
ncer
.
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608 J. Sandlund et al.
as well as in patients with co-morbidities and known risk factors, A. schaalii should always be ruled out as a causative agent. Considering the potential risk for diagnostic misinterpretation, careful culture proce-dures allowing growth of A. schaalii should be per-formed. Further studies are needed to identify risk factors and clinical manifestations, and to determine the optimal treatment duration.
Acknowledgements
The authors wish to thank Peggy Bergquist at the Department of Clinical Microbiology, Karolinska University Hospital, for skilful technical assistance.
Declaration of interest: The authors report no confl icts of interest. The authors alone are respon-sible for the content and writing of the paper.
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