First Report of IMI-2-Producing Enterobacter bugandensis and CTX-M-55-Producing Escherichia coli isolated from Healthy Volunteers in Tunisia.

The aim of this study was to characterize the prevalence of fecal carriage of extended-spectrum beta-lactamases and carbapenemase-producing Gram-negative bacteria among healthy humans in Tunisia. Fifty-one rectal swabs of healthy volunteers were plated on MacConkey agar plates supplemented with cefotaxime or imipenem. The occurrences of resistance genes, integrons, and phylogroup typing were investigated using PCR and sequencing. The genetic relatedness of isolates was determined by pulsed-field-gel-electrophoresis (PFGE) and multilocus-sequence-typing (MLST). Whole-genome-sequencing (WGS) was performed for the carbapenem-resistant isolate. Sixteen ESBL-producing Escherichia coli isolates and one carbapenem-resistant Enterobacter bugandensis were detected out of the fifty-one fecal samples. The ESBL-producing E. coli strains contained genes encoding CTX-M-15 (n = 9), CTX-M-1 (n = 3), CTX-M-27 (n = 3), and CTX-M-55 (n = 1). Three CTX-M-1-producers were of lineages ST131, ST7366, and ST1158; two CTX-M-15-producers belonged to lineage ST925 and ST5100; one CTX-M-27-producer belonged to ST2887, and one CTX-M-15-producer belonged to ST744. Six isolates contained class 1 integrons with the following four gene cassette arrangements: dfrA5 (two isolates), dfrA12-orf-aadA2 (two isolates), dfrA17-aadA5 (one isolate), and aadA1 (one isolate). E. bugandensis belonged to ST1095, produced IMI-2 carbapenemase, and contained qnrE1 and fosA genes. A genome-sequence analysis of the E. bugandensis strain revealed new mutations in the blaACT and qnr genes. Our results reveal an alarming rate of ESBL-E. coli in healthy humans in Tunisia and the first description of IMI-2 in E. bugandensis.

First Report of KPC-2 and KPC-3-Producing Enterobacteriaceae in Wild Birds in Africa.

The increased incidence of antibiotic-resistant Enterobacteriaceae is a public health problem worldwide. The aim of this study was to analyze the potential role of wild birds, given their capacity of migrating over long distances, in the spreading of carbapenemase, extended-spectrum ß-lactamase (ESBL), and acquired-AmpC beta-lactamase-producing Enterobacteriaceae in the environment. Fecal and pellet samples were recovered from 150 wild birds in seven Tunisian regions and were inoculated in MacConkey-agar plates for Enterobacteriaceae recovery (one isolate/animal). Ninety-nine isolates were obtained and acquired resistance mechanisms were characterized in the five detected imipenem-resistant and/or cefotaxime-resistant isolates, by PCR and sequencing. The following ESBL, carbapenemase, and acquired-AmpC beta-lactamase genes were detected: blaCTX-M-15 (two Escherichia fergusonii and one Klebsiella oxytoca isolates), blaKPC-2 (one K. oxytoca), blaKPC-3 (one E. fergusonii), blaACT-36, and blaACC-2 (two K. oxytoca, four E. fergusonii, and two E. coli). The IncFIIs, IncF, IncFIB, IncK, IncP, and IncX replicons were detected among these beta-lactamase Enterobacteriaceae producers. The blaKPC-2, tetA, sul3, qnrB, and cmlA determinants were co-transferred by conjugation from K. oxytoca strain to E. coli J153, in association with IncK and IncF replicons. Our results support the implication of wild birds as a biological vector for carbapenemase, ESBL, and acquired-AmpC-producing Enterobacteriaceae.

Extended-Spectrum ß-Lactamases among Enterobacteriaceae Isolated from Urinary Tract Infections in Gaza Strip, Palestine.

BACKGROUND: Extended-spectrum ß-lactamase-producing organisms causing urinary tract infections are increasing in incidence and pose a major impendence to health-care facility, having limited therapeutic options. This study aimed to assess the prevalence of ESBLs in Enterobacteriaceae isolates causing urinary tract infections in Gaza strip, Palestine, and to characterize ß-lactamase types and associated resistance genes. METHODS: Eighty-five Enterobacteriaceae isolates were recovered from urinary tract infections within three months in Gaza Strip hospitals. The characterization of ß-lactamase genes and the genetic environments of CTX-M, the identification of associated resistance genes, and the presence and characterization of integrons were tested by PCR and sequencing. RESULTS: The occurrence rate of ESBL among tested isolates was 30 (35.3%), and among ESBL-positive isolates, bla CTX-M was the highest followed by bla TEM. ESBL-CTX-M-1 group was confirmed in 93.3%, and the remaining carried CTX-M-9 group. CTX-M-15, CTX-M-3, CTX-M-1, CTX-M-14, CTX-M-27, and CTX-M-37 enzymes were demonstrated among the isolates with the majority (73%) being CTX-M-15. ISEcp-1 was demonstrated in 27 (90%, high incidence) of ESBL isolates. Class 1 integrons have been detected in higher rates (53.3%) in ESBL-positive isolates in comparison with non-ESBL isolates (6, 33.3%). Cassettes of integron-1 contain (aadA1, aadA2, aadA5, dfrA5, dfrA7, dfrA12, and dfrA17) genes. The aac(6')-Ib-cr gene was demonstrated in 36.7% of ESBL-positive isolates. CONCLUSIONS: This study indicates that bla CTX-M-15 was the most prevalent ß-lactamase in this region. Our study demonstrates for the first time in Palestine the identification of bla CTX-M-15 in P. rettgeri and S. liquefaciens, also bla CTX-M-37 in E. cloacae. The coexpression of multiple ß-lactamase genes with aac(6')-Ib-cr and qnr in the presence of ISEcp-1 and integrons in individual strains will increase the dissemination of highly resistant strains. ESBL producers were more resistant than non-ESBLs producers for almost all tested antibiotics.

Antimicrobial resistance and genetic lineages of faecal enterococci of wild birds: Emergence of vanA and vanB2 harbouring Enterococcus faecalis.

Migrating birds have been implicated in pathogen dissemination over long distances. The lack of data on the intestinal microbiota of birds makes these animals a promising path in order to understand their potential role in the transmission of antibiotic-resistant bacteria. This study aimed to investigate the diversity of enterococcal species, and to analyse the antimicrobial-resistant phenotypes/genotypes, as well as the genetic lineages of isolates obtained from faecal and pellet samples of colonial wild birds in Tunisia. Seventy-nine enterococci were recovered from 150 wild birds, after inoculation of samples in Slanetz-Bartley agar, and were identified as E. faecalis (n = 53), E. faecium (n = 19) and E. casseliflavus (n = 7). Antimicrobial susceptibility was tested, and the following rates of resistance were found: tetracycline (46.8%); erythromycin (34.2%); chloramphenicol (8.8%); gentamicin and streptomycin (2.5-3.8%); ciprofloxacin, trimethoprim-sulfamethoxazole and kanamycin (12.7-21%); and ampicillin and linezolid (0%). The tet(M), tet(L), erm(B), erm(C), aac(6')-Ie-aph(2″)-Ia and cat genes were detected in most tetracycline-, erythromycin-, gentamicin- and chloramphenicol-resistant enterococci, respectively. Three vancomycin-resistant E. faecalis isolates were detected, two with the vanA gene (into Tn1546) and one with the vanB2 gene (into Tn5382); these isolates showed different sequence types determined by multi-locus sequence typing (ST9, ST16 and a new ST848). Seven E. casseliflavus isolates harbouring the intrinsic vancomycin resistance mechanism vanC2 were obtained. The gelE, ace, agg, esp and hyl virulence genes were detected among vanA/vanB2 enterococci. This study provides insight into the possible role of wild birds in the spread of certain antimicrobial resistance genes, particularly vanA/vanB2. To the authors' knowledge, this is the first report of vanB2-containing enterococci in Africa.

Detection of CTX-M-15 harboring Escherichia coli isolated from wild birds in Tunisia.

BACKGROUND: The spreading of antibiotic resistant bacteria is becoming nowadays an alarming threat to human and animal health. There is increasing evidence showing that wild birds could significantly contribute to the transmission and spreading of drug-resistant bacteria. However, data for antimicrobial resistance in wild birds remain scarce, especially throughout Africa. The aims of this investigation were to analyze the prevalence of ESBL-producing E. coli in faecal samples of wild birds in Tunisia and to characterize the recovered isolates. RESULTS: One hundred and eleven samples were inoculated on MacConkey agar plates supplemented with cefotaxime (2 µg/ml). ESBL-producing E. coli isolates were detected in 12 of 111 faecal samples (10.81%) and one isolate per sample was further characterized. ß-lactamase detected genes were as follows: blaCTX-M-15 (8 isolates), blaCTX-M-15 + blaTEM-1b (4 isolates). The ISEcp1 and orf477 sequences were found respectively in the regions upstream and downstream of all blaCTX-M-15 genes. Seven different plasmid profiles were observed among the isolates. IncF (FII, FIA, FIB) and IncW replicons were identified in 11 CTX-M-15 producing isolates, and mostly, other replicons were also identified: IncHI2, IncA/C, IncP, IncI1 and IncX. All ESBL-producing E. coli isolates were integron positive and possessed "empty" integron structures with no inserted region of DNA. The following detected virulence genes were: (number of isolates in parentheses): fimA (ten); papC (seven); aer (five); eae (one); and papGIII, hly, cnf, and bfp (none). Molecular typing using pulsed-field gel electrophoresis and multilocus sequence typing showed a low genetic heterogeneity among the 12 ESBL-producing strains with five unrelated PFGE types and five different sequence types (STs) respectively. CTX-M-15-producing isolates were ascribed to phylogroup A (eleven isolates) and B2 (one isolate). CONCLUSION: To our knowledge, this study provides the first insight into the contribution of wild birds to the dynamics of ESBL-producing E. coli in Tunisia.

First Report of Extended-Spectrum ß-Lactamases Among Clinical Isolates of Klebsiella pneumoniae in Gaza Strip, Palestine.

Sixteen broad-spectrum cephalosporin-resistant Klebsiella pneumoniae isolates were recovered between April and June 2013 from Palestinian hospitals, Gaza Strip. Genes encoding extended-spectrum beta-lactamases (ESBLs) and other resistance genes were characterized by polymerase chain reaction and sequencing. The following ß-lactamase genes were detected: blaCTX-M-15+ blaSHV1+ blaTEM-1 (six isolates), blaCTX-M-15+ blaSHV5+ blaOXA-1 (two isolates), blaCTX-M-14a (two isolates), blaCTX-M-15+ blaSHV33 (one isolate), blaCTX-M-15+ blaTEM-1 (one isolate), blaCTX-M-15+ blaSHV12+ blaOXA-1(one isolate), blaCTX-M-15+ blaSHV5 (one isolate), blaCTX-M-15+ blaSHV1 (one isolate), and blaCTX-M-3 (one isolate). The ISEcp1 (in four cases truncated by IS26), orf477, or IS903 sequences were found upstream or downstream of blaCTX-M genes. The aac(6')-Ib-cr gene was found in seven isolates. The qnrS1 and qnrB1 genes were detected in five isolates and two isolates, respectively. Seven isolates contained class 1 integrons with four gene cassette arrangements: dfrA5 (three isolates), dfrA12-orf-aadA2 (two isolates), dfrA17-aadA5 (one isolate), and aadA1 (one isolate). A high clonal diversity was also observed among studied isolates by pulsed-field gel electrophoresis (12 unrelated profiles). This study demonstrates for the first time the emergence and polyclonal spread of multidrug-resistant ESBL-producing K. pneumoniae isolates among patients in a hospital setting in Gaza Strip, Palestine.

First report of extended-spectrum ß-lactamases among clinical isolates of Escherichia coli in Gaza Strip, Palestine.

This study aimed to assess the occurrence of extended-spectrum ß-lactamases (ESBLs) in clinical Escherichia coli isolates from Palestine and to characterise their type, genetic environments and associated resistance genes. Twenty-seven broad-spectrum-cephalosporin-resistant E. coli isolates were recovered between April and June 2013 in Gaza Strip hospitals. Characterisation of ESBL genes and their genetic environments, detection of associated resistance genes, and the presence and characterisation of integrons were performed by PCR and sequencing. The clonal relationship among ESBL-positive E. coli strains was determined by pulsed-field gel electrophoresis (PFGE) using the restriction enzyme XbaI. Phylogroup typing and virulence factors were studied by PCR. The following ESBL genes were identified: blaCTX-M-15 (21 isolates); blaCTX-M-14a (2 isolates); blaCTX-M-1 (2 isolates); blaCTX-M-3 (1 isolate); and blaCTX-M-27 (1 isolate). The blaTEM-1 gene was also detected in eight CTX-M-producing strains. The ISEcp1 sequence was found upstream of blaCTX-M in 23 isolates, and orf477 was found downstream of this gene in 24 isolates. IS903 was also detected downstream in three isolates. Six isolates carried class 1 integrons with the gene cassette arrangement dfrA17-aadA5. High clonal diversity was observed among the studied isolates by PFGE (24 unrelated profiles). The virulence gene fimA was detected in 23 isolates, the aer gene in 8 isolates and the papC gene in 7 isolates. The studied isolates belonged to phylogroups B2 (12 isolates), D (12 isolates) and A (3 isolates). This is the first report of the detection of CTX-M class ß-lactamases in E. coli of clinical origin in Gaza Strip hospitals.

IncI1 plasmids carrying bla(CTX-M-1) or bla(CMY-2) genes in Escherichia coli from healthy humans and animals in Tunisia.

The objective was to determine the location of bla(CTX-M-1) and bla(CMY-2) genes in 33 Escherichia coli isolates previously obtained from healthy humans, pets, and food-producing animals in Tunisia, and to characterize the genetic lineages of isolates. Molecular typing was performed by pulsed-field gel electrophoresis (PFGE)-XbaI and multilocus sequence typing (MLST). Plasmids were analyzed by S1-PFGE, polymerase chain reaction-based replicon typing, and plasmid MLST. Conjugation experiments were performed. The bla(CTX-M-1) and bla(CMY-2) genes were studied by I-Ceu1-PFGE and S1-PFGE, and subsequent hybridization with specific probes. Eighteen different sequence types (STs) were identified among the 30 CTX-M-1-producing isolates, 5 of them being detected in 17 isolates (ST/phylogroup): ST57/D, ST155/B1, ST58/B1, ST10/A, and ST398/A. Most of the bla(CTX-M-1)-positive isolates had different PFGE profiles, with the exception of four human and pet isolates of lineage ST57 with related PFGE profiles (>80% identity). Three CMY-2-producing isolates were typed as ST58/B1, ST117/D, and ST3632/B2. The IncI1 replicon was detected in all the 33 E. coli studied isolates, in many cases in combination with other replicons: IncF, IncX, IncK, IncR, IncY, colE, or IncN. The bla(CTX-M-1) gene was transferred by conjugation in 22 of the 30 positive strains and was located into IncI1 plasmids (ST3-CC3); the bla(CMY-2) gene was located into a conjugative IncI1 plasmid (ST12) of 97 kb in one strain. One bla(CTX-M-1)-positive strain carried the qnrB19 gene in a 33 kb IncX plasmid. Diverse genetic lineages are detected in extended-spectrum beta-lactamase- and AmpC beta-lactamase-producing E. coli from different origins. The bla(CTX-M-1) and bla(CMY-2) genes were associated with conjugative IncI1 (ST3 and ST12, respectively) plasmids in E. coli strains from human and animal origin.

Prevalence and characterization of extended-spectrum beta-lactamase (ESBL)- and CMY-2-producing Escherichia coli isolates from healthy food-producing animals in Tunisia.

The prevalence of extended-spectrum beta-lactamase (ESBL)- and plasmidic AmpC-beta-lactamase (pAmpC-BL)-producing Escherichia coli isolates has been studied in food-producing animals at the farm level in Tunisia, and recovered isolates were characterized for the presence of other resistance genes and integrons. Eighty fecal samples of food-producing animals (23 sheep, 22 chickens, 22 cattle, six horses, five rabbits, and two dromedaries) were obtained from 35 different farms in Tunisia in 2011. Samples were inoculated onto MacConkey agar plates supplemented with cefotaxime (2 mg/L) for cefotaxime-resistant (CTX(R)) E. coli recovery. CTX(R) E. coli isolates were detected in 11 out of 80 samples (13.8%), and one isolate per sample was further characterized (10 from chickens and one from a dromedary). The 11 CTX(R) isolates were distributed into phylogroups: B1 (five isolates), A (two isolates), D (three isolates), and B2 (one isolate). The following beta-lactamase genes were detected: bla(CTX-M-1) (seven isolates), bla(CTX-M-1)+bla(TEM-135) (one isolate), bla(CTX-M-1)+bla(TEM-1b) (one isolate), and bla(CMY-2) (two isolates). All ESBL- and pAmpC-BL-producing E. coli strains showed unrelated pulsed-field gel electrophoresis patterns. Seven isolates contained class 1 integrons with four gene cassette arrangements: dfrA17-aadA5 (three isolates), dfrA1-aadA1 (two isolates), dfrA15-aadA1 (one isolate), and aadA1 (one isolate). All isolates showed tetracycline resistance and contained the tet(A) +/- tet(B) genes. Virulence genes detected were as follows (number of isolates in parentheses): fimA (10); aer (eight); papC (two); and papGIII, hly, cnf, and bfp (none). Chicken farms constitute a reservoir of ESBL- and pAmpC-BL-producing E. coli isolates of the CTX-M-1 and CMY-2 types that potentially could be transmitted to humans via the food chain or by direct contact.

High diversity of genetic lineages and virulence genes in nasal Staphylococcus aureus isolates from donkeys destined to food consumption in Tunisia with predominance of the ruminant associated CC133 lineage.

BACKGROUND: The objective of this study was to determine the genetic lineages and the incidence of antibiotic resistance and virulence determinants of nasal Staphylococcus aureus isolates of healthy donkeys destined to food consumption in Tunisia. RESULTS: Nasal swabs of 100 donkeys obtained in a large slaughterhouse in 2010 were inoculated in specific media for S. aureus and methicillin-resistant S. aureus (MRSA) recovery. S. aureus was obtained in 50% of the samples, being all of isolates methicillin-susceptible (MSSA). Genetic lineages, toxin gene profile, and antibiotic resistance mechanisms were determined in recovered isolates. Twenty-five different spa-types were detected among the 50 MSSA with 9 novel spa-types. S. aureus isolates were ascribed to agr type I (37 isolates), III (7), II (4), and IV (2). Sixteen different sequence-types (STs) were revealed by MLST, with seven new ones. STs belonging to clonal clomplex CC133 were majority. The gene tst was detected in 6 isolates and the gene etb in one isolate. Different combinations of enterotoxin, leukocidin and haemolysin genes were identified among S. aureus isolates. The egc-cluster-like and an incomplete egc-cluster-like were detected. Isolates resistant to penicillin, erythromycin, fusidic acid, streptomycin, ciprofloxacin, clindamycin, tetracycline, or chloramphenicol were found and the genes blaZ, erm(A), erm(C), tet(M), fusC were identified. CONCLUSIONS: The nares of donkeys frequently harbor MSSA. They could be reservoirs of the ruminant-associated CC133 lineage and of toxin genes encoding TSST-1 and other virulence traits with potential implications in public health. CC133 seems to have a broader host distribution than expected.

Prevalence, antibiotic resistance, virulence traits and genetic lineages of Staphylococcus aureus in healthy sheep in Tunisia.

Nasal swabs of 163 healthy sheep were obtained from two farms and one abattoir in Tunisia during 2010. Samples were inoculated in Baird Parker agar and ORSAB medium for Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) recovery, respectively. MRSA was detected in 5 of these 163 samples (3%) in ORSAB medium, and one isolate per sample was further studied. MRSA isolates were mecA-positive, typed as ST153-CC80-t044-agrIII, and contained blaZ, ant(6)-Ia, aph(3')-IIIa, erm(C), tet(K), and fusB genes encoding penicillin, streptomycin, kanamycin, erythromycin, tetracycline and fusidic acid resistance, respectively. These MRSA isolates showed indistinguishable or closely related PFGE-patterns and harboured the lukF/lukS gene encoding the Panton-Valentine leukocidin and the luk-ED, hla, hld, and hlg(v) genes. Methicillin-susceptible S. aureus (MSSA) were recovered in 68 of the 163 samples (41.7%) and one isolate per sample was characterized. Most of MSSA (82.4%) showed susceptibility to the tested antibiotics with exceptions: penicillin (6%, carrying blaZ gene), tetracycline (19%, carrying tet(K) gene) and fusidic acid (9%). The following toxin-genes were identified among MSSA: tst (53 isolates), luk-M (52), luk-ED, hla, hlb, hld and hlg(v) (67), hlg (1), sec (49), sel (52), and the egc-cluster-like sen-sem-sei-seo-seg (1). Ten spa-types (two of them new ones) and nine sequence types (six new ones) were detected among the 73 S. aureus isolates, and they were ascribed to agr types I and III. All MRSA and MSSA isolates were able to coagulate bovine plasma and MRSA harboured the immune-evasion-gene-cluster type E. Conclusions. Nares of healthy sheep could be a reservoir of PVL-positive community-associated-MRSA and also of TSST-positive S. aureus isolates, with potential implications in public health.

Diversity of genetic lineages among CTX-M-15 and CTX-M-14 producing Escherichia coli strains in a Tunisian hospital.

Fourteen broad-spectrum-cephalosporin-resistant Escherichia coli isolates were recovered between June and December 2007 in a Tunisian hospital. Genes encoding extended-spectrum-beta-lactamases (ESBL) and other resistance genes were characterized by PCR and sequencing. The following ESBL genes were identified: bla (CTX-M-15) (12 isolates), bla (CTX-M-14a) (one isolate), and bla (CTX-M-14b) (one isolate). The bla (OXA-1) gene was detected in 13 bla (CTX-M)-producing strains and a bla (TEM-1) gene in 6 of them. The ISEcp1 sequence was found upstream of bla (CTX-M) genes in 8 of 14 strains, and orf477 or IS903 downstream of this gene in 13 strains. Nine of the strains carried class 1 integrons and five different gene cassette arrangements were detected, dfrA17-aadA5 being the most common. One of the strains (bla (CTX-M-14a)-positive) harbored three class 1 integrons, and one of them was non-previously described containing as gene cassettes new variants of aac(6')-Ib and cmlA1 genes and it was linked to the bla (CTX-M-14a) gene flanked by a truncated ISEcp1 sequence (included in GenBank with accession number JF701188). CTX-M-15-producing strains were ascribed to phylogroup B2 (six isolates) and D (six isolates). Multilocus-sequence-typing revealed ten different sequence-types (STs) among ESBL-positive E. coli strains with prevalence of ST405 (four strains of phylogroup D) and ST131 types (two strains of phylogroup B2 and serogroup O25b). A high clonal diversity was also observed among studied strains by pulsed-field-gel-electrophoresis (11 unrelated profiles). CTX-M-15 is an emergent mechanism of resistance in the studied hospital and the world-disseminated 0:25b-ST131-B2 and ST405-D clones have been identified among CTX-M-15-producing isolates.

Prevalence of broad-spectrum cephalosporin-resistant Escherichia coli isolates in food samples in Tunisia, and characterization of integrons and antimicrobial resistance mechanisms implicated.

The presence of broad-spectrum-cephalosporin-resistant Escherichia coli isolates and the implicated mechanisms of resistance were investigated in 79 food samples of animal origin obtained in different supermarkets and local butcheries in Tunisia. Ten of these samples (12.6%) harbored extended-spectrum beta-lactamase (ESBL) producing E. coli isolates and 13 ESBL-positive isolates were recovered (one or two/sample), which exhibited nine different Pulsed-Field-Gel-Electrophoresis (PFGE) patterns. ESBLs detected were the following: CTX-M-1 (10 strains), CTX-M-1+TEM-1b (2 strains) and CTX-M-1+TEM-20 (1 strain). The orf477 sequence was identified downstream of bla(CTX-M-1) gene in all 13 strains and ISEcp1 upstream in 9 strains. All ESBL-positive strains were included into phylogenetic group A or B1 (4 and 9 strains, respectively). Three of the 79 food samples (3.8%) contained broad-spectrum-cephalosporin-resistant and ESBL-negative E. coli isolates with AmpC phenotype. One isolate per sample was studied, and they showed unrelated PFGE patterns. The CMY-2 type beta-lactamase was identified in one of these 3 strains and specific point mutations in the promoter/attenuator region of ampC gene (at positions -42, -18, -1 and +58) were detected in the remaining two strains. Twelve ESBL-positive and one ESBL-negative E. coli strains contained class 1 integrons with the following gene cassette arrangements: dfrA1+aadA (6 strains) and dfrA17+aadA5 (7 strains). E. coli strains from food samples could represent a reservoir of ESBL-encoding genes and integrons that could be transmitted to humans through the food chain.