Salmonella Alachua: Causative agent of a foodborne disease outbreak

Abstract

The aim of this study is to report the occurrence of the first outbreak of food poisoning caused by Salmonella Alachua in Brazil, as well as the antimicrobial susceptibility and the genetic relatedness of Salmonella Alachua strains isolated from clinical and food samples.
To elucidate the outbreak, an epidemiological investigation was carried out, and two samples of common food were tested - mayonnaise salad and galinhada (a traditional Brazilian dish of chicken and rice) - according to the Compendium of methods for the microbiological examination of foods. Five stool samples were tested employing classic methods for the isolation and identification of enterobacteria. Strains of Salmonella were characterized for antibiotic susceptibility according to the Clinical and Laboratory Standards Institute guidelines (2013), and submitted to pulsed-field gel electrophoresis analysis, performed according to the Centers for Disease Control and Prevention PulseNet protocol.
A total of 94 people were interviewed after ingesting the food, 66 of whom had become ill. A 60-year old female patient who was hospitalized in a serious condition, developed septic shock and died two days after consuming the food. The presence of Salmonella Alachua was confirmed in all the analyzed stool samples, and in the two types of food. The five strains showed higher than minimum inhibitory concentration values of nalidixic acid (≥256μg/mL) and reduced ciprofloxacin susceptibility (minimum inhibitory concentration=0.5μg/mL). The pulsed-field gel electrophoresis analysis revealed indistinguishable patterns in Salmonella Alachua strains isolated from clinical and food samples.
The data presented herein confirm the foodborne disease outbreak. They also allowed for the identification of the source of infection, and suggest that products from poultry are potential reservoirs for this serotype, reinforcing the importance of warning consumers about the danger of possible contamination.
Copyright © 2015. Published by Elsevier Editora Ltda.

Full text

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w
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The
Brazilian
Journal
of
INFECTIOUS
DISEASES
Original
article
Salmonella
Alachua:
causative
agent
of
a
foodborne
disease
outbreak
Ivete
Aparecida
Zago
Castanheira
de
Almeidaa,∗,
Jacqueline
Tanury
Macruz
Peresia,
Elisabete
Cardiga
Alvesa,
Denise
Fusco
Marquesa,
Inara
Siqueira
de
Carvalho
Teixeiraa,
Sonia
Izaura
de
Lima
e
Silvaa,
Sandra
Regina
Ferrari
Pigonb,
Monique
Ribeiro
Tibac,
Sueli
Aparecida
Fernandesc
aInstituto
Adolfo
Lutz,
Centro
de
Laboratório
Regional
de
São
José
do
Rio
Preto,
São
Paulo,
SP,
Brazil
bVigilância
Epidemiológica
Municipal
de
Catanduva,
São
Paulo,
SP,
Brazil
cInstituto
Adolfo
Lutz
Central,
São
Paulo,
SP,
Brazil
a
r
t
i
c
l
e
i
n
f
o
Article
history:
Received
3
October
2014
Accepted
19
December
2014
Available
online
4
February
2015
Keywords:
Foodborne
diseases
Salmonella
Alachua
Drug
resistance
Brazil
a
b
s
t
r
a
c
t
Objectives:
The
aim
of
this
study
is
to
report
the
occurrence
of
the
first
outbreak
of
food
poisoning
caused
by
Salmonella
Alachua
in
Brazil,
as
well
as
the
antimicrobial
susceptibility
and
the
genetic
relatedness
of
Salmonella
Alachua
strains
isolated
from
clinical
and
food
samples.
Material
and
methods:
To
elucidate
the
outbreak,
an
epidemiological
investigation
was
car-
ried
out,
and
two
samples
of
common
food
were
tested
–
mayonnaise
salad
and
galinhada
(a
traditional
Brazilian
dish
of
chicken
and
rice)
–
according
to
the
Compendium
of
meth-
ods
for
the
microbiological
examination
of
foods.
Five
stool
samples
were
tested
employing
classic
methods
for
the
isolation
and
identification
of
enterobacteria.
Strains
of
Salmonella
were
characterized
for
antibiotic
susceptibility
according
to
the
Clinical
and
Laboratory
Stan-
dards
Institute
guidelines
(2013),
and
submitted
to
pulsed-field
gel
electrophoresis
analysis,
performed
according
to
the
Centers
for
Disease
Control
and
Prevention
PulseNet
protocol.
Results:
A
total
of
94
people
were
interviewed
after
ingesting
the
food,
66
of
whom
had
become
ill.
A
60-year
old
female
patient
who
was
hospitalized
in
a
serious
condition,
devel-
oped
septic
shock
and
died
two
days
after
consuming
the
food.
The
presence
of
Salmonella
Alachua
was
confirmed
in
all
the
analyzed
stool
samples,
and
in
the
two
types
of
food.
The
five
strains
showed
higher
than
minimum
inhibitory
concentration
values
of
nalidixic
acid
(≥256
␮g/mL)
and
reduced
ciprofloxacin
susceptibility
(minimum
inhibitory
concentra-
tion
=
0.5
␮g/mL).
The
pulsed-field
gel
electrophoresis
analysis
revealed
indistinguishable
patterns
in
Salmonella
Alachua
strains
isolated
from
clinical
and
food
samples.
∗Corresponding
author
at:
Rua
Alberto
Sufredine
Bertoni,
n◦2325,
São
José
do
Rio
Preto,
SP
15060-020,
Brazil.
E-mail
addresses:
iazcalmeida@ial.sp.gov.br,
izacal@ig.com.br
(I.A.Z.C.
Almeida).
http://dx.doi.org/10.1016/j.bjid.2014.12.006
1413-8670/©
2015
Elsevier
Editora
Ltda.
All
rights
reserved.

234
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Conclusion:
The
data
presented
herein
confirm
the
foodborne
disease
outbreak.
They
also
allowed
for
the
identification
of
the
source
of
infection,
and
suggest
that
products
from
poultry
are
potential
reservoirs
for
this
serotype,
reinforcing
the
importance
of
warning
consumers
about
the
danger
of
possible
contamination.
©
2015
Elsevier
Editora
Ltda.
All
rights
reserved.
Introduction
Salmonella,
a
genus
of
zoonotic
enterobacteria
responsible
for
outbreaks
of
infections
in
both
humans
and
animals,
has
sig-
nificant
economic
importance
worldwide.1–3 It
is
estimated
that
Salmonella
causes
93.8
million
human
infections
and
155,000
deaths
per
year
around
the
world.3From
2000
to
2013,
Salmonella
was
the
infectious
agent
most
commonly
linked
to
outbreaks
of
food
poisoning
in
Brazil,
with
a
total
of
1560
episodes
representing
38.3%
of
all
agents
identified
during
the
said
period.4
Both
children
and
the
elderly,
as
well
as
immunocompro-
mised
individuals
with
salmonellosis
may
see
the
condition
evolve
to
more
severe
stages
as,
upon
entering
the
blood-
stream,
the
bacteria
can
cause
extraintestinal
infections.5
The
risk
of
invasive
disease
is
two
to
six
times
higher
than
with
other
foodborne
pathogens6;
the
death
rate
is
also
higher.7
Salmonella
Alachua
was
first
described
in
1952,
during
a
study
of
the
effects
of
salmonellosis
in
pigs
in
the
city
of
Alachua,
Florida,
where
it
was
isolated
in
a
soil
sam-
ple
from
a
pig
farm.8However,
the
first
reported
isolation
in
animals
was
in
1955
after
several
outbreaks
of
enteri-
tis
in
chickens
from
different
farms
in
Bombay,
India,
that
resulted
in
a
considerable
loss
of
birds.9Since
then,
iso-
lation
has
proved
uncommon
worldwide,
as
it
is
found
in
human
and
non-human
samples
at
a
rate
of
from
0.03
to
3.8%.10–14
In
this
study,
we
report
the
occurrence
of
the
first
outbreak
of
food
poisoning
caused
by
Salmonella
Alachua
in
Brazil,
in
a
city
in
the
northwestern
region
of
the
State
of
São
Paulo.
Moreover
we
report
of
the
antimicrobial
susceptibility
and
the
genetic
relatedness
of
Salmonella
Alachua
strains
isolated
from
clinical
and
food
samples.
Materials
and
methods
Epidemiological
investigation
In
order
to
better
explain
the
occurrence
of
a
foodborne
dis-
ease
outbreak
in
a
city
in
the
northwestern
region
of
the
State
of
São
Paulo
in
November
2012,
an
epidemiological
investigation
was
carried
out
by
the
local
health
surveil-
lance
team,
with
the
collection
of
samples
of
the
ingested
food
–
mayonnaise
salad
and
galinhada
(a
traditional
Brazil-
ian
dish
of
chicken
and
rice)
–
and
stool
samples
from
five
patients.
All
the
tests
were
performed
at
the
Regional
Labo-
ratory
Center
of
Instituto
Adolfo
Lutz
in
São
José
do
Rio
Preto
(RLCIAL).
Microbiological
analysis
of
the
food
The
food
was
analyzed
according
to
the
methods
described
in
the
Compendium
of
Methods
for
the
Microbiological
Examina-
tion
of
Foods
–
APHA15 for
contamination
by
coliform
group
bacteria,
Staphylococcus
aureus,
Bacillus
cereus,
Clostridium
per-
fringens
and
Salmonella.
The
procedures
for
isolation
and
identification
of
Salmonella,
were
carried
out
through
pre-enrichment
of
25
g
samples
by
homogenization
with
225
mL
lactose
broth
(10−1dilution),
and
incubation
overnight
at
36
±
1◦C.
Selective
enrichment
was
performed
in
tetrathionate
(TT)
broth
and
modified
Rappaport-Vassiliadis
(RV)
broth,
followed
by
incu-
bation
at
36
±
1◦C
for
24
h
and
42 ◦C
for
24–48
h,
respectively.
Each
enrichment
broth
was
streaked
onto
selective
plates:
Salmonella-Shigella
agar
(SS),
brilliant
green
agar
(BG)
and
xylose
lysine
deoxycholate
agar
(XLD),
and
incubated
for
24
h
at
36
±
1◦C.15
Even
though
no
other
biochemical
tests
were
performed,
characteristic
colonies
of
each
plate
were
biochemically
tested
using
only
IAL
medium16 for
the
presumptive
identification
of
Enterobacteriaceae
and
incubated
for
24
h
at
36
±
1◦C.
Strains
with
presumptive
identification
of
Salmonella
were
submitted
to
serological
tests
using
polyvalent
somatic
(O)
and
flagellar
(H)
antisera
produced
by
the
Laboratory
of
Enteric
Pathogens
of
the
Instituto
Adolfo
Lutz.
The
standard
methodology
for
the
study
of
Salmonella15 rec-
ommends
the
use
of
the
presence/absence
method
in
25
g
of
a
food
sample.
The
highest
dilution
in
which
Salmonella
is
demonstrably
present
in
the
food
sample
was
used
as
a
complement
to
the
testing,
with
the
purpose
of
deter-
mining
which
food
had
the
highest
microbial
load.
Albeit
important,
this
is
not
a
quantitative
method.
For
this,
we
started
with
10
mL
of
a
10−1dilution,
serial
dilutions
of
the
food
samples
were
performed
in
tubes
containing
lactose
broth
up
to
a
dilution
of
10−9.
After
incubating
the
tubes
for
18–24
h
at
36
±
1◦C,
the
presence
of
turbidity
was
verified
in
the
different
dilutions.
The
inoculum
from
all
tubes
that
presented
turbidity
was
submitted
to
selective
enrichment,
isolation
and
identification
procedures,
pursuant
to
the
APHA
methodology.15
Stool
analysis
Stool
samples
were
collected
from
a
total
of
five
patients
by
swab
and
transported
in
Cary-Blair
medium
to
investigate
Escherichia
coli,
Aeromonas
spp.,
Shigella
spp.
and
Salmonella
spp.
At
RLCIAL,
the
swabs
were
seeded
in
plates
with
Mac-
Conkey
Agar
(MC),
Salmonella-Shigella
Agar
(SS)
and
Sorbitol
MacConkey
Agar
(MCS),
and
incubated
for
24
h
at
36
±
1◦C.

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Subsequently,
the
swab
was
placed
in
a
tube
containing
10
mL
of
Tetrathionate
(TT)
broth
and
incubated
for
24
h
at
36
±
1◦C
for
selective
enrichment.
After
this
period,
the
TT
broth
was
inoculated
on
plates
with
MC
and
Brilliant
Green
Agar.
After
incubation
for
18–24
h
at
36
±
1◦C,
all
the
plates
with
the
selec-
tive
medium
were
examined
for
colony
morphology
and
for
utilization
of
lactose/sorbitol,
which
are
used
to
inoculate
the
IAL
medium16 for
the
presumptive
identification
of
the
researched
microorganisms.
Strains
with
presumptive
identification
of
Salmonella
were
submitted
to
serological
tests
using
polyvalent
somatic
(O)
and
flagellar
(H)
antisera
produced
by
the
Laboratory
of
Enteric
Pathogens,
Instituto
Adolfo
Lutz.
Serotyping
All
the
isolates
of
Salmonella
from
the
food
and
stool
samples
were
sent
to
the
Central
Laboratory
of
the
Instituto
Adolfo
Lutz
(CLIAL)
for
complete
serotyping
on
the
basis
of
somatic
O
and
phase
1
and
phase
2
of
the
H
flagellar
antigens
by
agglutina-
tion
tests
with
antisera
prepared
in
the
Laboratory
of
Enteric
Pathogens,
Institute
Adolfo
Lutz,
São
Paulo
as
specified
in
the
Kauffmann–White
protocol
for
Salmonella
serotyping.17
Susceptibility
testing
Antimicrobial
susceptibility
testing
was
performed
for
all
isolates
using
the
disk
diffusion
method
according
to
the
guidelines
of
the
Clinical
and
Laboratory
Standards
Insti-
tute
–
CLSI.18 The
following
antimicrobial
disks
(Oxoid)
were
used:
nalidixic
acid
(30
␮g),
amoxicillin–clavulanic
acid
(20/10
␮g),
amikacin
(30
␮g),
ampicillin
(10
␮g),
aztreonam
(30
␮g),
ceftazidime
(30
␮g),
cefotaxime
(30
␮g),
ceftriaxone
(30
␮g),
cefepime
(30
␮g),
ciprofloxacin
(5
␮g),
chlorampheni-
col
(30
␮g),
streptomycin
(10
␮g),
gentamicin
(10
␮g),
imipenem
(10
␮g),
trimethoprim–sulfamethoxazole
(1.25/23.75
␮g),
sul-
fonamide
(250
␮g),
and
tetracycline
(30
␮g).
Categorization
of
the
diameter
of
halos
in
susceptible,
intermediate
or
resistant
followed
CLSI
recommendations.18
Minimum
inhibitory
concentrations
(MIC)
were
deter-
mined
for
nalidixic
acid
and
ciprofloxacin
by
Etest
(AB
Biodisk,
Solna,
Sweden)
according
to
the
manufacturer’s
recommen-
dations.
The
range
of
MIC
of
ciprofloxacin
for
Salmonella
was
recently
changed
to
susceptible:
≤0.06
␮g/mL;
intermediate
susceptible:
0.12–0.5
␮g/mL;
resistant:
≥1
␮g/mL.18
E.
coli
ATCC
25922
and
E.
coli
ATCC
35218
were
used
as
ref-
erence
strains
for
antimicrobial
susceptibility
testing.
Pulsed
field
gel
electrophoresis
Pulsed
field
gel
electrophoresis
(PFGE)
analysis
was
per-
formed
for
all
the
isolates
at
CLIAL
according
to
the
Centers
for
Disease
Control
and
Prevention
(CDC)
PulseNet
pro-
tocol
(www.cdc.gov/pulsenet/pathogens/index.html).
Briefly,
cell
lysis
was
followed
by
proteinase
K
treatment
and
DNA
restriction
with
XbaI
(New
England
Biolabs,
Ipswich,
MA).
Electrophoresis
was
performed
with
a
CHEF
DRIII
system
(BioRad
Laboratories
Inc.,
Hercules,
CA)
using
the
follow-
ing
run
parameters:
a
switch
time
of
2.2–63.8
s
and
a
run
time
of
20
h.
Salmonella
Braenderup
H9812
was
used
as
a
molecular
size
marker.19 TIFF
images
were
analyzed
using
the
BioNumerics
5.0
software
(Applied
Maths).
Dice’s
coefficient
with
tolerance
of
1.5
was
used
to
calculate
similarity
using
the
Unweighted
Pair
Group
Method
with
arithmetic
averages
(UPGMA).
Results
Epidemiological
investigation
Of
the
94
people
interviewed
after
the
foodborne
out-
break,
the
epidemiological
investigation
found
that
the
consumption
of
mayonnaise
salad
and
galinhada
was
com-
mon
to
the
entire
group;
66,
both
children
and
adults,
had
become
ill.
The
median
incubation
period
was
72
h,
and
the
main
symptoms
observed
were:
diarrhea
63/66
(95.4%),
abdominal
pain
50/66
(75.7%),
nausea
40/66
(60.6%),
fever
27/66
(40.9%),
vomiting
23/66
(34.8),
and
headache
22/66
(33.3%).
Attack
rates
by
age
group
are
shown
in
Table
1.
According
to
the
investigation,
a
60-year
old
female
patient
who
was
hospitalized
in
a
serious
condition,
developed
septic
shock
and
died
two
days
after
consuming
the
food.
Microbiological
analysis
The
presence
of
Salmonella
was
confirmed
in
all
the
analyzed
stool
samples
and
in
both
types
of
food,
consequently
it
was
isolated
in
dilutions
of
10−7and
10−2of
the
salad
mayonnaise
and
galinhada,
respectively.
No
other
pathogens
were
isolated
from
the
food
or
stool
samples.
The
Most
Probable
Numbers
(MPN)
of
thermotolerant
col-
iforms
found
in
the
mayonnaise
salad
and
galinhada
samples
were
>2400/g
and
240/g,
respectively.
Serotyping
All
the
strains
isolated
from
human
and
food
sources
were
identified
as
Salmonella
enterica
serovar
Alachua
by
agglutina-
tion
tests.
Antimicrobial
susceptibility
All
the
Salmonella
Alachua
strains
demonstrated
resistance
to
nalidixic
acid
and
reduced
susceptibility
to
ciprofloxacin
(intermediate
resistant).
However,
all
of
them
were
susceptible
to
the
other
antimicrobials
tested.
The
seven
strains
showed
higher
MIC
values
for
nalidixic
acid
(≥256
␮g/mL)
and
reduced
ciprofloxacin
susceptibility
(MIC
=
0.5
␮g/mL).
Pulsed
field
gel
electrophoresis
A
dendrogram,
generated
by
PFGE
patterns
of
Salmonella
Alachua
strains
using
XbaI
as
the
restriction
enzyme,
is
shown
in
Fig.
1.
One
PFGE
pattern
was
identified
among
the
Salmonella
Alachua
clinical
and
food
isolates
analyzed.
The
genetic
relatedness
among
the
strains
was
100%.

236
b
r
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9(3):233–238
Table
1
–
Attack
rate
by
age
group
of
the
subjects
exposed
to
risk
by
the
ingestion
of
food
contaminated
by
Salmonella.
Age
range
(years)
Subjects
exposed
to
risk
Total,
n
Attack
rate
(%)
Individuals
sick,
n
Individuals
not
sick,
n
<1
–
–
–
–
1–9
7
1
8
87.5
10–20
6
2
8
75.0
20–39
28
11
39
71.8
40–49
10
4
14
71.4
50–59
5
7
12
41.7
≥60
10
3
13
76.9
Total
66
28
94
70.2
Discussion
Currently,
Salmonella
is
one
of
the
most
common
microorgan-
isms
involved
in
foodborne
disease
outbreaks
worldwide.4,20,21
In
the
United
States,
Salmonella
Alachua
corresponds
to
0.05%
of
the
isolates
identified
in
the
period
from
1999
to
2009,
while
Salmonella
Typhimurium
and
Salmonella
Enteritidis
were
the
prevalent
serotypes,
accounting
for
18.5%
and
16.3%
of
cases,
respectively.13
A
similar
situation
occurred
in
Mexico,
where,
between
1972
and
1999,
only
26
(0.1%)
strains
of
24,394
Salmonella
iso-
lates
from
various
public
health
and
private
laboratories
were
found
to
be
Salmonella
Alachua.12
Three
(0.03%)
and
one
(0.04%)
isolates
of
Salmonella
Alachua
identified
in
non-human
and
human
material,
respectively,
were
registered
in
the
State
of
São
Paulo,
Brazil,
in
different
periods.11,22 Moreover,
in
the
State
of
Goiás,
Brazil,
Salmonella
Alachua
was
isolated
in
two
(3.8%)
samples
from
bird
transport
box
liners.14
According
to
Almeida
et
al.23 no
presence
of
Salmonella
Alachua
was
observed
in
human
and
non-human
(food)
mat-
ter
during
the
1990s
in
the
same
region
as
the
current
reported
outbreak.
The
only
time
in
which
this
serotype
was
isolated
was
in
2007,
from
a
sample
of
raw
eggs,
during
an
investigation
of
a
foodborne
disease
outbreak.
However,
it
was
not
consid-
ered
the
causative
agent,
as
the
Salmonella
enterica
serotype
Infantis
was
isolated
in
all
the
stool
samples
of
the
affected
individuals
(12
patients).24
A
significant
increase
in
the
number
of
Salmonella
Alachua
isolates
(27
to
88)
observed
in
the
USA
in
1982,
corresponding
to
an
upsurge
of
226%
over
the
previous
year,
was
attributed
to
the
adoption
of
children
from
a
nursery
in
Calcutta,
India,
by
American
families.25 Given
the
above,
one
should
consider
the
possibility
that
this
serotype
may
have
had
a
relevant
epi-
demiological
expression
for
some
time
in
India.
Changes
in
the
prevalence
of
serotypes
have
been
observed
in
several
studies,22,26–28 hence
any
serotype,
however
unusual
or
uncommon,
may
become
emergent
and
cause
serious
infec-
tions
or
outbreaks.
Some
serotypes
are
frequently
associated
with
certain
classes
of
food.
Thus,
studies
on
the
serotypes
characteriza-
tion
provide
information
on
reservoirs,
routes
of
transmission
and
prevalence
in
a
specific
region,
particularly
when
out-
breaks
of
foodborne
diseases
occur.4,29,30
Notwithstanding
the
fact
that
there
are
few
reports
on
Salmonella
Alachua,
products
originating
from
poultry
farms
can
be
considered
possible
reservoirs
for
this
serotype.14,24
49.3
100
Human
Human
Human
Human
Human
Food
Food
Marker
10-30571
10-30555
10-30572
10-30560
10-30557
10-30553
10-30552
Source Type
LabID
60
80
100
2000
1500
1200
1000
700.00
600.00
500.00
100.00
350.00
300.00
250.00
200.00
150.00
80.00
60.00
10.00
30.00
20.00
PFGE-Xbal PFGE-Xbal
Dice (Opt 1.50%) (Tol 1.5%-1.5%) (H>0.0% S>0.0%) [0.0%-100.0%]
Fig.
1
–
Dendrogram
pulsed
field
gel
electrophoresis
patterns
of
Salmonella
Alachua
strains.
LabID
(identification
number)
and
source
type
(human
or
food)
of
the
Salmonella
Alachua
strains
analyzed.
Marker:
Salmonella
Braenderup
H9812
digested
with
XbaI
enzyme
was
used
as
a
molecular
size.

b
r
a
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j
i
n
f
e
c
t
d
i
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.
2
0
1
5;1
9(3):233–238
237
Considering
the
fact
that
Salmonella
Alachua
has
been
iden-
tified
with
the
same
genetic
connection
in
both
the
isolated
foods,
it
can
be
suggested
that
cross-contamination
occurred
between
the
two
types
of
food
analyzed.
Cross-contamination
can
occur
as
a
result
of
inadequate
manipulation,
and
use
of
contaminated
kitchen
utensils,
and
may
become
critical,
depending
on
the
amount
of
time
that
the
product
is
exposed
to
improper
storage
temperatures.31 It
should
be
emphasized
that
the
use
of
raw
eggs
in
the
preparation
of
the
mayonnaise
salad
during
the
epidemiological
investigation
of
the
outbreak
was
not
confirmed.
Therefore,
the
chicken
meat
used
for
the
preparation
of
galinhada
can
be
considered
the
likely
source
of
Salmonella
Alachua.
The
infectious
dose
of
Salmonella
varies
between
105and
108cells,
with
infective
doses
as
low
as
≤103being
reported
in
immunocompromised
patients,
while
certain
serotypes
are
related
to
foodborne
disease
outbreaks.5,32 Consequently,
despite
the
non-quantification
of
Salmonella,
the
large
number
of
affected
individuals
in
this
study
can
be
explained
by
the
presence
of
this
pathogen
at
dilutions
of
10−7in
the
sample
of
mayonnaise
salad.
Certain
reports
have
demonstrated
antimicrobial
resis-
tance
to
Salmonella
Alachua
strains
from
both
human
and
non-human
sources.14,33,34 In
this
study,
even
though
there
was
susceptibility
of
Salmonella
Alachua
strains
to
most
of
the
antimicrobials
tests,
all
presented
resistance
to
nalidixic
acid
(MIC
≥256
␮g/mL)
with
reduced
susceptibility
to
ciprofloxacin
(MIC
=
0.5
␮g/mL).
The
resistance
to
nalidixic
acid
can
predict
a
resistance
to
fluoroquinolones,
as
observed
in
the
study.
Fluoroquinolones
are
currently
used
to
treat
invasive
and
systematic
salmonellosis,
occurring
in
humans.
These
are
also
effective
in
treating
a
range
of
different
infections
encoun-
tered
in
animals.
Resistance
to
fluoroquinolones
is
relatively
uncommon
with
Salmonella.
However,
in
recent
years,
studies
have
reported
an
increase
in
the
number
of
clinical
isolates
with
reduced
susceptibility
to
ciprofloxacin
associated
with
treatment
failure.35–37 The
emergence
of
reduced
susceptibil-
ity
to
fluoroquinolones
among
food
animals
and
humans
is
considered
a
significant
public
health
concern,
and
should
be
carefully
monitored.
PFGE
revealed
indistinguishable
patterns
in
Salmonella
Alachua
strains
isolated
from
clinical
and
food
samples,
thus
confirming
the
foodborne
disease
outbreak;
this
also
allowed
for
the
identification
of
the
source
of
infection.
PFGE
is
a
standard
typing
method
used
in
Salmonella
outbreak
investiga-
tions
to
determine
the
relationship
and
distribution
of
genetic
subtypes
of
Salmonella
circulating
in
countries,
as
well
as
the
application
for
the
investigation
of
foodborne
outbreaks,
and
to
detect
emerging
pathogens.38
Conclusion
This
study
reports
on
the
first
foodborne
disease
outbreak
caused
by
the
Salmonella
Alachua
serotype
in
Brazil.
The
source
of
infection
was
confirmed
by
PFGE,
and
all
Salmonella
Alachua
strains
presented
resistance
to
nalidixic
acid,
and
reduced
sus-
ceptibility
to
ciprofloxacin.
The
findings
of
this
study
highlight
the
importance
of
the
numerous
and
complex
activities
of
Public
Health
Laboratories
in
the
development
of
necessary
knowledge
to
optimize
prevention
and
food
contamination
control.
Conflicts
of
interest
The
authors
declare
no
conflicts
of
interest.
r
e
f
e
r
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