K. Ben Slama

Thuricin 7: a novel bacteriocin produced by Bacillus thuringiensis BMG1.7, a new strain isolated from soil

Aims: Detection and identification of new antagonistic activities towards Bacillus cereus and relatives.

Nasal carriage of Staphylococcus aureus in healthy humans with different levels of contact with animals in Tunisia: genetic lineages, methicillin resistance, and virulence factors

Nasal swabs of 423 healthy humans who showed different levels of contact with animals (frequent, 168; sporadic, 94; no contact, 161) were obtained in Tunisia (2008–2009), and 99 of them presented other associated risk factors. Methicillin-resistant Staphylococcus aureus (MRSA) was detected in one of these 423 samples (0.24%), retrieved from a veterinarian. The MRSA isolate was mecA-positive, typed as ST80-t203-SCCmecIVc-agrIII, and contained tet(K), ant(6)-Ia, and aph(3′)-IIIa genes encoding tetracycline, streptomycin, and kanamycin resistance, respectively. This MRSA isolate also contained the lukF/lukS virulence gene encoding Panton–Valentine leukocidin. Fifty-four (12.8%) additional nasal samples contained methicillin-susceptible S. aureus (MSSA) and one isolate/sample was characterized. A high diversity of spa types (n = 43; 4 new) and pulsed-field gel electrophoresis (PFGE) types (n = 37) was detected among the 55 recovered S. aureus strains. The percentages of antimicrobial resistance/detected resistance genes were as follows: tetracycline [22%/tet(K)-tet(L)-tet(M)], erythromycin [5%/msrA], ciprofloxacin [14.5%], trimethoprim–sulfamethoxazole [2%/dfrA], streptomycin [11%/ant(6)-Ia], kanamycin [7%/aph(3′)-IIIa], amikacin [5%], and chloramphenicol [2%]. Four and two isolates carried the lukF/lukS and eta and/or etb genes, respectively, and always in individuals with contact with animals. Eleven isolates carried the tst gene and were recovered from individuals with different levels of contact with animals.

Antibiotic resistance and mechanisms implicated in clinical enterococci in a Tunisian hospital.

Abstract Susceptibility testing for 15 antibiotics was performed in a series of 191 clinical enterococci recovered in a Tunisian Hospital during 2000-2003. Species detected were the following ones (number of isolates): E. faecalis (139) E. faecium (41) E. casseliflavus (5) E. gallinarum (3) E. avium (2) and E. hirae (1). The percentages of antibiotic resistance detected were as follows (E. faecalis/ E. faecium/other species) : penicillin (0/ 73/ 9%), tetracycline (78/ 44/ 54%), chloramphenicol (52/ 29/ 27%), erythromycin (66/ 100/ 82%), spiramycin (84/ 83/ 64%), pristinamycin (100/ 0/ 73%), trimethoprim-sulfamethoxazole (88/ 78/ 91%), rifampicin (72/ 41/ 0%), vancomycin (0/ 0/ 36%), teicoplanin (0/ 0/ 0%), high-level-resistance for gentamicin (24/ 29/ 45%), streptomycin (34/ 56/ 55%) and kanamycin (41/ 68/ 55%). Increased vancomycin minimum inhibitory concentrations (MICs) were only detected in E. casseliflavus and E. gallinarum isolates (MIC range 8-24 μg/ml). The erm(B) catA, tet(M) aac(6′)-aph(2′′) aph(3′)-IIIa, and ant(6)-Ia genes were detected in 91%, 32%, 86%, 98%, 100%, and 72% of the E. faecium and E. faecalis isolates resistant to erythromycin, chloramphenicol, tetracycline and highlevel- resistant to gentamicin, kanamycin and streptomycin, respectively. A total of 20 unrelated pulsed-field-gel-electrophoresis patterns were found in the series of 46 high-level gentamicin-resistant E. faecalis and E. faecium isolates of this study.

Antibiotic resistance in Escherichia coli in husbandry animals: the African perspective

In the last few years, different surveillances have been published in Africa, especially in northern countries, regarding antimicrobial resistance among husbandry animals. Information is still scarce, but the available data show a worrying picture. Although the highest resistance rates have been described against tetracycline, penicillins and sulphonamides, prevalence of plasmid‐mediated quinolone resistance genes and extended spectrum β‐lactamase (ESBL) are being increasingly reported. Among ESBLs, the CTX‐M‐1 group was dominant in most African surveys. Within this group, CTX‐M‐15 was the main variant both in animals and humans, except in Tunisia where CTX‐M‐1 was more frequently detected among Escherichia coli from poultry. Certain blaCTX‐M‐15‐harbouring clones (ST131/B2 or ST405/D) are mainly identified in humans, but they have also been reported in livestock species from Tanzania, Nigeria or Tunisia. Moreover, several reports suggest an inter‐host circulation of specific plasmids (e.g. blaCTX‐M‐1‐carrying IncI1/ST3 in Tunisia, IncY‐ and Inc‐untypeable replicons co‐harbouring qnrS1 and blaCTX‐M‐15 in Tanzania and the worldwide distributed blaCTX‐M‐15‐carrying IncF‐type plasmids). International trade of poultry meat seems to have contributed to the spread of other ESBL variants, such as CTX‐M‐14, and clones. Furthermore, first descriptions of OXA‐48‐ and OXA‐181‐producing E. coli have been recently documented in cattle from Egypt, and the emergent plasmid‐mediated colistin resistance mcr‐1 gene has been also identified in chickens from Algeria, Tunisia and South Africa. These data reflect the urgent need of a larger regulation in the use of veterinary drugs and the implementation of surveillance programmes in order to decelerate the advance of antimicrobial resistance in this continent.

Characterisation of nasal Staphylococcus delphini and Staphylococcus pseudintermedius isolates from healthy donkeys in Tunisia

REASONS FOR PERFORMING STUDY Staphylococcus intermedius group (SIG) bacteria can colonise the nares of some animals but are also emerging pathogens in humans and animals. OBJECTIVES To analyse SIG nasal carriage in healthy donkeys destined for food consumption in Tunisia and to characterise recovered isolates. METHODS Nasal swabs from 100 healthy donkeys were tested for SIG recovery, and isolates were identified by biochemical and molecular methods. Antimicrobial susceptibility of isolates was tested and detection of antimicrobial resistance and virulence genes was performed. Isolates were typed at the clonal level by multilocus sequence typing and SmaI pulsed-field gel electrophoresis. RESULTS Staphylococcus delphini and Staphylococcus pseudintermedius (included in SIG) were obtained in 19% and 2% of the tested samples, respectively, and one isolate per sample was characterised. All isolates were meticillin susceptible and mecA negative. Most S. delphini and S. pseudintermedius isolates showed susceptibility to all antimicrobials tested, with the exception of 2 isolates resistant to tetracycline (tet(M) gene) or fusidic acid. The following toxin genes were identified (percentage of isolates): lukS-I (100%), lukF-I (9.5%), siet (100%), se-int (90%), seccanine (19%) and expA (9.5%). Thirteen different pulsed-field gel electrophoresis profiles were identified among the 21 SIG isolates. Additionally, the following 9 different sequence types (STs) were detected by multilocus sequence typing, 6 of them new: ST219 (6 isolates), ST12 (5 isolates), ST220 (3 isolates), ST13, ST50, ST193, ST196, ST218 and ST221 (one isolate each). CONCLUSIONS Staphylococcus delphini and S. pseudintermedius are common nasal colonisers of donkeys, generally susceptible to the antimicrobials tested; nevertheless, these SIG isolates contain virulence genes, including the recently described exfoliative gene (expA) and several enterotoxin genes, with potential implications for public health. This is the first description of S. delphini in Tunisia. The Summary is available in Chinese - see Supporting information.

Polymorphism in pbp5 Gene Detected in Clinical Enterococcus faecium Strains with Different Ampicillin MICs from a Tunisian Hospital

Abstract The polymorphism in pbp5 gene was investigated in nine unrelated clinical gentamicin-resistant Enterococcus faecium strains with different minimal-inhibitory-concentration values for ampicillin (six ampicillin-resistant and three ampicillin-susceptible). Five alleles were detected when the pbp5 C-terminal region was analysed, two of them in the ampicillin-susceptible strains. Two of our high-ampicillin-resistant strains showed a new allele characterised by the Thr416Ala and Val462Ala substitutions. Two different alleles were identified when the pbp5 N-terminal region was studied; one of them in the unique strain (E. faecium 83) that presented very low ampicillin MIC (<0.125 μg/ml) and a nucleotidic mutation implicating a stop codon at 451 position. RT-PCR experiments carried out on five E. faecium strains belonging to each of the different pbp5 alleles (including E. faecium 83) gave positive results indicating the expression of this gene. Specific mutations in pbp5 gene could be responsible of the high MIC values of some of the E. faecium strains.

Faecal enterococci from camels in Tunisia: species, antibiotic resistance and virulent genes.

Enterococci species are commensal microorganisms found in the gastrointestinal tract of animals and humans, being commonly isolated from faeces, water, plants, soil and food products, among others (Aarestrup and others 2000, Mannu and others 2003, Abriouel and others 2008). Enterococci are also important human pathogens being frequently implicated in human infections. These microorganisms present a high capacity of acquisition of antibiotic resistance mechanisms through horizontal gene transfer (Hammerum and others 2010). Of special relevance is the acquisition by enterococci of vancomycin-resistant genes, and the emergence of these resistant isolates in animals is being associated to the use of avoparcin in the past as an animal growth-promoter in some countries (Hammerum and others 2010). It is important to characterise the resistance and virulence trait characteristics of enterococci borne in different animals that could come in contact with human beings, and also to identify the species and clones circulating within animal ecosystems. Toward these aims, this study has been focused in order to study antibiotic resistance and presence of virulent genes in enterococci recovered from faecal samples of camels in Tunisia, and to determine the genetic diversity among the predominant species detected by pulsed-field gel electrophoresis (PFGE). To our knowledge, this is the first study that analyses the diversity and the characteristics of faecal enterococci in camels. Faecal samples of 100 camels (one sample per animal) from different regions of Tunisia (north, centre and south) were collected in this study. Samples were diluted and seeded in Slanetz-Bartley agar plates and they were incubated for 48 hours at 37°C. Phenotypic identification at the genus level of recovered isolates was based on Gram stain, bile-aesculin and hypersalin tests. Identification of Enterococcus species …

Diversity of Structures Carrying the aac(6′)-aph(2“) Gene in Clinical Enterococcus faecalis and Enterococcus faecium Strains Isolated in Tunisia

Abstract The diversity of structures carrying the aac(6′)-aph(2”) gene was studied in 46 high-level gentamicin-resistant Enterococcus faecalis and Enterococcus faecium clinical strains recovered in a Tunisian hospital during the period 2000-2003. The inclusion of the aac(6′)-aph(2”) gene within the Tn4001 composite element or in its truncated forms (lacking the IS256 at the right, the left or at both sides of the aac(6′)-aph(2”) gene) was investigated by PCR and sequencing. The aac(6′)-aph(2”) gene was included in the composite Tn4001 element in 19 of 34 high-level gentamicin-resistant E. faecalis strains (56%) and in 1 of 12 E. faecium strains (12%). A truncated form of Tn4001 lacking IS256 at the left-hand (in 10 E. faecalis and 8 E. faecium), at the right-hand (3 E. faecalis and 2 E. faecium) or at both sides of the aac(6′)-aph(2”) gene (in 2 E. faecalis and 1 E. faecium) was also detected in 26 of our enterococci. The transference by conjugation of the aac(6′)- aph(2”) gene, associated with other resistance genes, was demonstrated in seven of the high-level gentamicin-resistant E. faecalis strains.