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A Ben Hassen

Publications and source records attributed to A Ben Hassen.

18 recordsLinked to original sources
PubMed1992

[Staphylococcus aureus nosocomial infections in an intensive care milieu (1985-1989) in Tunis].

221 strains of Staphylococcus aureus oxacillin resistant (MetiR) caused nosocomial infections were isolated from 1985 to 1989 in a medical intensive care unit. The survey of susceptibility to antibiotics was established according to the computerized data of disk susceptibility test. The resistance phenotypes to beta-lactams, aminoglycosides and macrolides were established for epidemiological study. S. aureus infections were mainly bacteraemia (31%) and peritonitis (12%). These isolates were resistant to oxacillin with a high level (mean MIC 386 micrograms/ml). Their resistance phenotypes were MLSBc (constitutive resistance to macrolides, lincosamine and streptogramines B) in 53% and S + KGT (resistance to streptomycin, kanamycin, gentamicin and tobramycin) in 61%. All the isolates were susceptible to pristinamycin and vancomycin (MIC 0.1 and 2 micrograms/ml). These phenotypes related to the spread of multiply drug resistant strains were responsible of nosocomial outbreaks. Strains with the same pattern of resistance were isolated among the medical staff and in the environment. Infection control measures allowed to stop these outbreaks.

Cross Infection↗
PubMed1991

Nosocomial outbreak of acute gastroenteritis in a neonatal intensive care unit in Tunisia caused by multiply drug resistant Salmonella wien producing SHV-2 beta-lactamase.

In a Tunisian hospital 27 babies, including 12 who were premature, in a single intensive care unit suffered acute gastroenteritis in the period from January to May 1988. The mean age at the onset of gastroenteritis was 8.4 days; nine babies died. Salmonella wien was isolated from stools (all babies) and blood (4 babies). It was also isolated from the stools of one nurse and from a mattress. Twelve of the babies had received cefotaxime, which was successfully replaced by oral colimycin. The outbreak was stopped by the implementation of infection control measures. All isolates of Salmonella wien were of the same biotype, and had the same antibiotic resistance pattern (third generation cephalosporins, monobactams, aminoglycosides, chloramphenicol, trimethoprim and sulphonamides) and plasmid DNA restriction pattern. The isolates were all susceptible to a combination of cefotaxime and clavulanic acid (a beta-lactamase inhibitor), which displayed synergy, suggesting the presence of a beta-lactamase (geometric mean MICs 11.24 micrograms/ml for cefotaxime alone and 0.24 micrograms/ml in combination with 0.1 micrograms/ml potassium clavulanate). All isolates produced TEM-1 and SHV-2 beta-lactamase which was not transferable to Escherichia coli by conjugation. The presence of the SHV-2 enzyme in Salmonella wien may allow it to adapt to newer beta-lactams which is a cause for concern in this hospital.

Acute Disease↗
PubMed1991

Species incidence and antimicrobial-agent resistance patterns of Enterobacteriaceae in Charles Nicolle Hospital, Tunis, from 1983 to 1987.

Between July 1983 and December 1987, 13,108 strains of enterobacteriaceae were isolated at Charles Nicolle Hospital in Tunis. This study reports the prevalence of different species isolated, their resistance and the evolution of bacterial resistance during that period. There appeared to be a great stability in the distribution of bacterial groups. Among the commonly sensitive species, Proteus mirabilis showed a high proportion of strains resistant to ampicillin (79.3%), carbenicillin (75.9%), cefalotin (73.8%) and gentamicin (46%). The proportions of resistant strains in P. mirabilis were much the same for each successive year from 1983 to 1987, and the percentages of resistant strains in the majority of the bacterial species were similarly stable. Amikacin and cefotaxime remained the most active antibiotics against enterobacteriaceae.

Drug Resistance, Microbial↗
PubMed1991

[Beta-lactam and aminoglycoside resistant phenotypes in enterobacteria isolated in pediatrics].

Beta-lactams and aminoglycosides are widely used in the therapy of serious Gram negative infections in pediatrics. In order to survey acquired resistance, the phenotype of resistance to beta-lactams and aminoglycosides were characterized for 260 strains of enterobacteriaceae among the mainly isolated species in pediatrics. These phenotypes were established according to the results of the disk susceptibility tests for beta-lactams respectively ampicillin, ticarcillin, cefaloridin and cefotaxim, and aminoglycosides, streptomycin (S), gentamicin (G), tobryamycin (T), amikacin (A), and netilmicin (N). 49% of E. coli and 73% of P. mirabilis strains were resistant to 3 beta-lactams (RRRS). 72% of Salmonella spp. strains were resistant to 4 beta-lactams (RRRR). For the majority of strains, the mainly observed resistance phenotype to aminoglycosides was streptomycin resistance excepted for Salmonella spp., which was S + KGTNA. The high level of acquired resistance to beta-lactams and aminoglycosides among Enterobacteriaceae with the selection of multiresistant strains would be explained by the wild use of cefotaxim and amikacin in pediatrics.

Aminoglycosides↗
PubMed1990

Two novel transferable extended-spectrum beta-lactamases from Klebsiella pneumoniae in Tunisia.

Two novel beta-lactamases conferring multiresistance to antibiotics including oxyimino beta-lactams have been identified in two nosocomial K. pneumoniae strains isolated in Tunis in 1986 and 1988. Both enzymes were encoded by ca. 150-kilobase plasmids. Donor and transconjugant strains producing these enzymes exhibited highly similar pattern of resistance (CTX phenotype) to beta-lactams including penicillins and oxyimino beta-lactams e.g. cefotaxime, ceftriaxone, ceftazidime, and aztreonam. High and variable synergy (16 to 1066-fold) was obtained when combined to 0.1 microgram/ml of clavulanate (beta-lactamase inhibitor). The isoelectric points of these two enzymes were 5.4 and 6.4. These beta-lactamases differed from TEM types by hydrolysis for cefotaxime or ceftriaxone but were inhibited by clavulanate and cloxacillin. DNA hybridization studies suggested that that the genes of these enzymes may be derived from genes encoding TEM-type enzymes.

DNA, Bacterial↗
PubMed1990

[Enzymatic resistance to cefotaxime in 56 strains of Klebsiella spp., Escherichia coli and Salmonella spp. at a Tunisian hospital (1984-1988)].

The enzymatic and plasmid-encoded resistance towards oxyimino-beta-lactams has been recently reported as related to the production of an extended-spectrum beta-lactamase (e.g. SHV-2, CTX-1 or TEM-3), in particular in our hospital since 1984. The prevalence of that resistance has been examined from January 1984 to December 1988 in function of specimen, unit and type of enzyme among 8,421 isolates of Klebsiella spp., E. coli, Salmonella spp. Each isolate showing a diameter of inhibition zone size inferior or equal to 25 mm for cefotaxime, the double disk synergy test was performed between a disk of amoxicillin and a clavulanic acid disk of cefotaxime, ceftriaxone, ceftazidime and aztreonam. In case of synergy, sonicated extracts have been prepared and examined by isoelectrofocusing with the detection of beta-lactamase activity by ceftriaxone and nitrocefin. 56 isolates (K. pneumoniae, K. oxytoca, E. coli, S. wien, S. typhimurium scored positive including 27 in pediatrics, 18 in surgery, and 8 in medicine. 41% of isolates have been obtained from blood cultures and 26.8% from urines. A majority of isolates (49/56) produced the SHV-2 type, but other types mediating the resistance phenotype CTX have been individualized initially by their isoelectric points e.g. 5.4 (TEM-20 in K. pneumoniae in July 1986), 6.4 (TEM-21 in E. coli, 1 K. pneumoniae in July 1988). The prevalence of resistance to cefotaxime from 1984 to 1988 has increased (from 0.3 to 1.4%), the highest rate being observed in pediatrics (5.6% in 1984 and 22.1% in 1988).

Cefotaxime↗
PubMedDate not supplied

Epidemiology of extended spectrum beta-lactamases.

Beta-lactamases play a major part in resistance, as recently redemonstrated by the emergence of extended spectrum beta-lactamases. Since its discovery in FR Germany, SHV-2 has been reported from four continents and CTX-1 (TEM-3) was established in at least 26 French hospitals. More than 12 other enzymes have been individualized. The newest aspect of resistance was probably underestimated because most strains of enterobacteria (mainly Klebsiella pneumoniae) appeared susceptible to oxyimino-beta-lactams as suggested by MICs or diameters of inhibition zone sizes. The double-disk synergy test between amoxicillin/clavulanic acid and oxyimino-beta-lactams was useful to easily detect two susceptibility patterns (CTX, CAZ). Extended spectrum beta-lactamases isolated among nosocomial isolates of enterobacteria (urines, blood, wound, sputum cultures) mostly from intensive care units have spread through hospitals. If outbreaks were described, numerous serotypes were identified in Klebsiella pneumoniae. In France the distribution of extended spectrum beta-lactamases showed that CTX-1 (TEM-3) was well distributed among ten species unlike SHV-type enzymes (SHV-2, SHV-3, SHV-4) preferentially detected in Klebsiella pneumoniae. A majority of strains produced CAZ-type enzymes in Escherichia coli. Some isolates produced two extended spectrum beta-lactamases. In Tunisia extended spectrum beta-lactamase producing strains were mainly identified among pediatric isolates of Klebsiella pneumoniae, Salmonella and Escherichia coli; SHV-2 was predominant but recently CTX-1 and two other types with an isoelectric point of 6.35 and 5.4 (phenotype CTX) were individualized. Because plasmid-encoded, this mechanism was spreading in France among enterobacteria with other resistance markers (e.g. netilmicin, amikacin) for CTX-1 unlike SHV-2.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Infections↗
PubMedDate not supplied

[Pseudomonas aeruginosa and beta-lactam resistance phenotypes (Tunisia 1989-1990)].

366 strains of P. aeruginosa were studied. More than half of samples were issued from urology (40%) and general surgery (21%) and samples are mostly urine specimens (46%). The phenotypes of resistance to 3 beta-lactams (respectively ticarcillin, cefotaxime and ceftazidime) showed that 73% of the strains were wild phenotype (SSS-SIS-SRS). The MIC of ticarcillin +/- clavulanic acid, azlocillin, cefoperazone, cefsulodin, cefotaxime and ceftazidime against 93 strains chosen among different phenotypes of resistance showed that ceftazidime is the most active beta-lactam, 93% of strains being inhibited by 16 micrograms/ml. These MIC and iodometric test performed on 33 strains with ticarcillin MIC > 128 mg/l showed that acquired resistance was non enzymatic in 21% of cases and was related to beta-lactamase production in 79% of cases.

Cefotaxime↗