[Epidemiology of hepatitis E in Tunisia].
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Biomedical subjects
Publications and source records attributed to S Ben Redjeb.
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The plasmid profile of 28 multiresistant Salmonella serovar Wien strains isolated between 1985 and 1990 is described. Four types of plasmids were individualised. Among these plasmids, two were responsable for beta-lactam resistance, type I plasmid of 110 kb and type II of 30 kb.
Methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen in hospitals. Between 1985 to 1988, there has been an increase in the number of MRSA (92 %) caused by an epidemic emergency in medical care unit of our hospital. Infections control measures allowed to stop these outbreaks (20 % MRSA in 1990). But incidence of MRSA persist to decrease without supplement control measures and in 1994, only 7 % of Staphylococcus aureus strains are MRSA.
A serious epidemic of Acinetobacter baumannii resistant to imipenem occurred in the surgical intensive care unit of the hospital Charles-Nicolle in Tunis during February 1994, causing two deaths among three patients. The Acinetobacter strains were isolated from various samples of the intensive care unit. The techniques used for typing were biotyping, antibiogram, plasmid profiles and chromosomal DNA by random amplified polymorphic DNA (RAPD). The A baumannii strains isolated from patients exhibited an identical pattern with all the epidemiological markers utilized; the strains from the surrounding areas showed four and six different patterns respectively for phenotypic and genotypic characters. The strain isolated from a care table had the same phenotypic and genotypic pattern as that of the patients' strains.
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A multiresistant Salmonella typhi (S typhi, strain 302) was isolated from a blood culture of a patient in the Infectious Diseases department of Rabta Hospital in Tunis. The following tests were carried out: antibiotic susceptibility testing by the agar diffusion method; determination of the minimum inhibitory concentration against four beta-lactam antibiotics (amoxicillin, ceftriaxone, ceftazidime, imipenem), chloramphenicol, gentamicin, and amikacin by the agar dilution method; conjugation with E coli K12 for study of transferability of resistance markers; and electrophoresis of plasmid DNA extracts on agarose gel. S typhi 302 was resistant to amoxicillin, streptomycin, tetracycline, chloramphenicol, and sulfamide-trimethoprim, and this resistance was transferable in toto with a frequency of 10(-4). The MICs of amoxicillin and chloramphenicol were, respectively, 1024 (due to the production of TEM-1 beta-lactamase) and 256 mg/l. These resistance markers were carried by a plasmid of about 40 kb, similar to the Salmonella wien plasmid. The easy acquisition of a multiresistance plasmid by S typhi suggests that epidemiological monitoring of this serovar should be carried out.
During a five and a half years' period, 805 strains of beta-haemolytic groups A, B, C and G streptococci were isolated. Among these, 28 were responsible for bacteremia; 57 percent group B and 32 percent group A. All strains were susceptible to beta-lactam antibiotics; 4 strains were resistant to macrolides. The majority of patients had underlying diseases. Mortality was high in this group.
252 nontyphoidic salmonellae strains isolated from pediatrics were identified by using standard laboratory procedures and were serotyped with commercial antisera. Antibiotic susceptibility tests were performed by the agar diffusion method. Mostly isolates obtained from feces (182) and blood (67) and 89% of them from newborns and nursings. S. sér. Wien represented 75% of the isolates. The other serovars were essentially S. sér Typhimurium, S. sér Infantis and S. sér Enteritidis. All the isolates of S. sér Wien and S. sér Typhimurium were resistant to amoxicillin, carbenicillin, cephalothin, streptomycin, chloramphenicol and tetracycline from 1980. From 1987 S. sér Wien isolates developed resistance to cefotaxime and amikacin. Distribution nontyphoidic salmonellae strains according to the year was variable. Maximal isolates were in September and October. Two major epidemics were observed in this study, in 1982 and 1989. 94% of the strains determined nosocomial infections. The source of infection was established during the epidemic of 1989. The application of hygiene measures led to decline the number of isolates in 1990 and their disappearance in 1991, any strains of S. sér Wien was isolated.
Since 1985 to 1990, 153 isolates of non typhoidic Salmonella were recovered from pediatric unit of the Charles Nicolle Hospital in Tunis. The epidemiological profile of these isolates was established according to the biochemical and serological characterizations, the antibiotic susceptibility patterns (disk diffusion method) to betalactams and aminoglycosides. 127 isolates of Salmonella spp were from stools and 22 from blood cultures. The main serotypes were S. ser. Wien (108 isolates) and S. ser. Typhimurium (21). A sample of 50 isolates was selected among the different resistance phenotypes for determination of MICs and betalactamase identification by isolelectro-focusing (36 isolates). All of them were resistant to ampicillin and carbenicillin but variable for cephaloridine. Since 1986 appeared the resistance to cefotaxime and in 1990 all the S. ser. Wien isolates were resistant to the 4 betalactams tested including cefotaxime associated to streptomycin, kanamycin, gentamicin, tobramycin and amikacin. All of them had a high level of resistance to amoxicillin and gentamicin (mean MICs > 2048 and > 512 mg/l). The mean MIC of cefotaxime was 43.2 mg/l for S. ser. Wien, 64mg/l for S. ser. Typhimurium and decreased to 1.9 and 0.12 mg/l in combination with 1 mg/l of clavulanic acid. The beta-lactam resistance was mediated to enzymatic mechanism, at first the betalactamase of TEM-1 type alone, then associated to extended-spectrum betalactamase, mainly type SHV-2 since 1986, and other new types in 1990. They were under the control of plasmids with different sizes.
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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.
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.