Trop Anim Health ProdDOI 10.1007/s11250-012-0334-7
Antimicrobial susceptibility and multi-drug resistanceof Salmonella enterica subspecies entericaserovars in Sudan
Mayha Mohammed Ali Nor Elmadiena &Adil Ali El Hussein & Catherine Anne Muckle &Linda Cole & Elizabeth Wilkie & Ketna Mistry &Ann Perets
# Springer Science+Business Media Dordrecht 2012
Abstract This study was undertaken to determine the anti-
(98.4 %), ciprofloxacin (93.8 %), and norfloxacin (90.6 %).
microbial resistance patterns of Salmonella enterica subspe-
Two chicken- and the two human-origin S. Kentucky iso-
cies enterica recovered from human, food, water, and
lates were resistant to both ciprofloxacin and norfloxacin.
animal samples collected in Khartoum State, Sudan. A total
All S. Kentucky isolates and the one S. Rissen isolate
of 64 Salmonella isolates belonging to 28 different serovars
demonstrated multi-drug resistance. The results indicate
were tested for their susceptibility to 13 antimicrobial
the significance of multi-drug-resistant Salmonella serovars
agents. The majority of isolates (98.4 %) were resistant to
isolated from chickens and other animals and foods as
at least one antimicrobial agent. Isolates were frequently
sources for multi-drug-resistant Salmonella in humans in
resistant to ampicillin (90.6 %), cephalexin (50.0 %), nali-
dixic acid (25.0 %), streptomycin (21.9 %), kanamycin(18.8 %), gentamicin (17.2 %), and co-trimoxazole and
Keywords Salmonella serovars . Multi-drug resistance .
trimethoprim (12.5 %). The most common pattern of multi-
ple drug resistance included resistance to ampicillin andcephalexin. Most isolates were sensitive to chloramphenicol
Emirates College of Technology, Millennium Tower Sheikh
Hamdan Street, P.O. Box: 41009, Abu Dhabi,
Department of Pathology and Microbiology, Atlantic Veterinary
College, University of Prince Edward Island, Charlottetown,
L. Cole : E. Wilkie : K. Mistry : A. Perets
National Committee for Clinical Laboratory
Laboratory for Salmonellosis, Laboratory for Foodborne
Office International des Epizooties, Reference
Zoonoses, Public Health Agency of Canada,Guelph, Ontario, Canada
National Antimicrobial Resistance Monitoring
participation in various surveillance programs, help monitor
the development and spread of antimicrobial resistance in
To date, few studies have analyzed the levels of resis-
tance to antimicrobial agents in Salmonella serovars in
Sudan (Yagoub et al. ). The present study was therefore
Danish Integrated Antimicrobial Resistance
undertaken to detect and monitor multi-drug resistance pro-
files among Salmonella serovars isolated in Sudan.
Members of Salmonella enterica subspecies enterica are
Isolation and identification of Salmonella
widely distributed in the environment and in the intestinaltracts of animals. Most human infections are acquired
Salmonella were isolated and identified as previously de-
through consumption of contaminated food of animal origin
scribed by El-Hussein et al. (). Salmonella isolates
(Majowicz et al. ; Anjum et al. ). The progressive
were recovered from a variety of sources: raw and cooked
increase in multi-antimicrobial-resistant Salmonella strains
food; chlorinated drinking water; livestock meat and feces;
isolated from humans has been associated with the wide-
and fish, chicken, and human fecal samples. Presumptive
spread use of antimicrobial agents in food animal produc-
Salmonella isolates were shipped to the Public Health
tion. This spread of antimicrobial resistance through the
Agency, Office International des Epizooties (OIE)
food chain is regarded as a major public health issue
Reference Laboratory for Salmonellosis, Guelph, Ontario,
(Threlfall Lynch et al. ; Foley and Lynne
Canada, for serotyping and phage typing as previously
Le Hello et al. ). The appearance of both plasmid-
described by El-Hussein et al. (Sixty-four
mediated antibiotic resistant against conventional anti-
Salmonella isolates identified into 28 different serovars
Salmonella drugs and chromosomal resistance to quinolones
and fluoroquinolones has reduced therapeutic options forSalmonella septicemia in humans (Foley and Lynne ).
Studies on antimicrobial resistance in Salmonella have
primarily been undertaken in developed countries (van
The antimicrobial resistance of the 64 Salmonella isolates
Duijkeren et al. ), having launched large-scale surveil-
was tested against 13 antimicrobial agents by the disk dif-
lance systems to monitor the antimicrobial resistance of
fusion method using Mueller Hinton agar (Oxoid, UK) and
bacterial enteric pathogens (Jones et al. DANMAP
antibiotic disks (Hi Media, India) following the guidelines
; Abdellah et al. ). In developing countries like
of the Clinical and Laboratory Standards Institute (CLSI),
Sudan, Salmonella and other zoonotic bacterial pathogens
formerly the National Committee for Clinical Laboratory
are not routinely cultured, and their resistance to commonly
Standards (CLSI ). An isolate was defined as suscepti-
employed antimicrobials both in public health and veteri-
ble or resistant based on the critical points recommended by
nary practices is rarely determined (Kariuki et al.
National surveillance systems, ideally based on integra-
The 13 antibiotics tested were those commonly used in
tion of data for animals, food, and humans, are needed to
humans or poultry flocks in Sudan, these being: ampicillin
develop strategies for containing antimicrobial drug resis-
(25 μg/disk), ceftazidime (30/10 μg), chloramphenicol
tance. In several countries, these programmes are primarily
(30 μg), ciprofloxacin (5 μg), gentamicin (10 μg), kanamy-
based on a network of public or private clinical laboratories
cin (30 μg), nalidixic acid (25 μg/disk), norfloxacin (10 μg),
that refer Salmonella isolates to public health laboratories
streptomycin (25 μg), trimethoprim (5 μg/disk), co-
for identification. However, such laboratory-based surveil-
trimoxazole (25 μg/disk), nitrofurantoin (100 μg/disk), and
lance systems in developing countries are hampered by cost
constraints and poor access to quality health facilities,resulting in a low rate of isolation of bacterial pathogensfrom patients having mild infections (Bouchrif et al. ).
These constraints account for the lack of data and underes-timation of the number of Salmonella infections in many
The results of testing Salmonella isolates against 13 differ-
countries, including Sudan. Clinical microbiology laborato-
ent antimicrobial drugs are summarized in Tables and
ries, through routine antimicrobial susceptibility testing and
Isolates were mainly resistant to ampicillin (90.6 %),
Table 1 Distribution by serovar and source of antimicrobial resistant
Salmonella from samples collected in Khartoum State, Sudan
Numbers in parentheses are the numbers of isolates. S. Typhimu-
rium*1 : Phagetype 2, S. Enteritidis*1 : Phagetype 21a (from food)
A1 ampicillin, C2 chloramphenicol, CAC3 ceftazidime, CIP4 cipro-
floxacin, Cp5 cephalexin, Co6 co-trimoxazole, GM7 gentamicin, Ka8kanamycin, Na9 nalidixic acid, NF10 nitrofurantoin, NOR11 norflox-
acin, S12 streptomycin, Tr13 trimethoprim
cephalexin (50 %), nalidixic acid (25 %), streptomycin
(21.9 %), and kanamycin (18.8 %). A total of 17.2 % iso-
lates were resistant to gentamicin and 12.5 % to co-
trimoxazole and trimethoprim. Isolates belonging to S.
Kentucky, S. Rissen, S. Muenster, S. I:4,12: r;-:enz15 were
resistant to streptomycin. Two S. Livingstone isolates and
one isolate each of S. Adelaide, S. Schwarzengrund, and S.
Typhimurium were also resistant to streptomycin. All iso-
lates were sensitive to chloramphenicol with the exception
of one S. Uganda isolate which showed intermediate sus-
ceptibility. Only a low degree of resistance (3.1 %) to
ceftazidime was detected, but 32.8 % of isolates demonstrat-
ed only intermediate susceptibility to this drug. Most iso-
lates were sensitive to ciprofloxacin (93.8 %) and
norfloxacin (90.6 %). Two human S. Agona isolates were
resistant to norfloxacin. The two human and two of the
chicken S. Kentucky isolates were resistant to both norflox-
Sixty three of 64 isolates (98.4 %) were resistant to at
least one antimicrobial drug, and 71.9 % were resistant to
more than one antimicrobial drug (Table ). Only the one
Johannesburg isolate was sensitive to all antimicrobials
tested (Table Twenty-six different patterns of antimicro-
bial resistance were identified (Table ). The most common
profiles were those which included resistance to ampicillin
and cephalexin (20.3 %). The one S. Rissen isolate recov-
ered was of chicken origin and was resistant to eight drugs.
All S. Kentucky isolates were resistant to at least four drugs,
with the human isolates being resistant to seven.
Variations in resistance of different serovars to a particu-
lar antibiotic can be seen in Tables and , with S. Rissen
and S. Kentucky isolates being the most multi-drug resis-
tant. Human and chicken isolates were most commonly
chloramphenicol, and furazolidone in Sudan might have ledto the emergence of resistance, whereas ciprofloxacin has
The majority (98.4 %) of 64 Salmonella isolates recovered
been newly introduced in the medical field and is not used
from human feces and a variety of animal, food, and water
samples in Sudan were resistant to at least one antimicrobial
Of particular concern, all eight S. Kentucky isolates were
drug, this most commonly being ampicillin (90.6 %). Multi-
multi-drug resistant. This serovar was common to both
drug resistance was more frequent in chicken and animal source
humans and chickens, suggesting that chicken and
isolates than in humans. A similar small-scale survey of
chicken-food products are a potential source of salmonello-
Salmonella from food and humans conducted in Addis
sis in the food chain (El-Hussein et al. ; Le Hello et al.
Ababa, Ethiopia, during 2003–2004 (Zewdu and Poppe
Similar to our study, all three S. Kentucky isolates
found 32.7 % of 98 isolates were resistant to one or more of 24
from chicken or beef origin isolated in Addis Ababa,
antimicrobials tested, with resistance being most common to
Ethiopia, were resistant to at least eight antimicrobials,
streptomycin (75 %), followed by ampicillin (59.4 %). Another
including ciprofloxacin (Zewdu and Poppe
2003 study of chicken carcass samples in Addis Ababa (Molla
Emergence of this multi-resistant serovar undermines the
et al. found that 63.7 % of 80 Salmonella isolates were
value of relatively cheaper and commonly available antimi-
resistant to one or more antimicrobials, with resistance to
crobials as first-line drugs for human systemic salmonellosis
sulfisoxazole being highest (51.2 %) and 45 % of isolates being
for poor citizens of developing countries, as well as the less
resistant to ampicillin. A 2003 study of Salmonella from beef
available and more expensive cephalosporins and quinolone
samples in Dakar, Senegal, found that 60 % of 247 isolates
were resistant to at least one antimicrobial (Stevens et al. ).
The high proportion of Salmonella isolates in our study
resistant to at least one antimicrobial is consistent with a
2001 study in the USA which found that 84 % of Salmonellaisolates from retail ground chicken, beef, turkey, and pork
Our results are based on a relatively small number of
were resistant to at least one antimicrobial. Recent national
Salmonella isolates; however, these findings are consistent with
antimicrobial resistance surveillance data for Salmonella
the trends of Salmonella multi-drug resistance found in similar
from animals collected in Canada (CIPARS ) showed
small-scale surveillance research investigations conducted in
that 52 % of Salmonella isolates from chicken samples and
the same time period in other African countries (Fadlalla et al.
65 % of pigs abattoir samples were resistant to one or more
; Molla et al. Stevens et al. Zewdu and Poppe
antimicrobials, and that 47 % of chicken and 69 % of
), as well as large-scale national surveillance programs in
pig retail meat samples were resistant to one or more
developed countries, such as DANMAP (DANMAP ),
NARMS (Foley and Lynne ), CIPARS (CIPARS ),
As previously noted (El-Hussein et al. ), it is difficult to
make comparisons between Salmonella surveillance surveys
This present study clearly demonstrates the need for con-
conducted in different countries as the prevalence of
tinued active surveillance to highlight the public health signif-
Salmonella serovars varies regionally and isolation rates de-
icance of multi-drug resistance among Salmonella in animals
pend upon the country, sample plan, and methodology used.
and humans in Sudan. Salmonella surveillance can provide
We speculate that the high level of multi-drug resistance of
data to target interventions to most effectively treat and prevent
Salmonella isolates in Sudan can be attributed to selective
foodborne and zoonotic pathogens (Mangen et al. ).
pressure from the irrational use of antimicrobials in food ani-mals and humans which selects for certain Salmonella serovarsmore prone to develop resistance than others (WHO
The authors gratefully acknowledge the support
of the Office International des Epizooties (OIE) Reference Laboratory
Our findings are comparable to a recently reported study on
for Salmonellosis, Laboratory for Foodborne Zoonoses, Public Health
antimicrobial susceptibility of Salmonella serotypes isolated
Agency of Canada, Guelph, Ontario, Canada.
from the feces of humans, cattle, camels, and poultry in Sudan(Fadlalla et al. ). This survey demonstrated that 93.1 % of87 human isolates and 46.8 % of 32 animal isolates were
resistant to at least one of the ten antimicrobial agents tested. The most common resistance was to streptomycin (75 %),followed by ampicillin (59.4 %). Resistance to ciprofloxacin,
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Neuromuscular Disorders 15 (2005) 498–512126th International Workshop: Congenital Myasthenic Syndromes,24–26 September 2004, Naarden, The NetherlandsDavid Beesona, Daniel Hantaı¨b, Hanns Lochmu¨llerc,*, Andrew G. EngeldaNeurosciences Group, Weatherall Institute of Molecular Medicine, The John Radcliff, Oxford, UKbINSERM U582, Institut de Myologie, Hoˆpital de la Salpeˆtrie`re, Pa