First molecular characterization of HIV-1 Tunisian strains

In order to identify HIV-1 subtypes circulating in Tunisia, blood specimens from 25 HIV-1 infected Tunisian patients were collected. Proviral HIV-1 DNA was genotyped by sequence analysis of the C2-V3 env region. HIV-1 subtypes were determined in 21 DNA sequences: 20 were of subtype B and one was a circulating recombinant form (CRF02 AG). Subtype B largely dominates the epidemiology of HIV-1 infection in Tunisia, suggesting the probable imported origin of HIV-1 infection, but further studies are needed to investigate the potential diversification of HIV-1 isolates in Tunisia.

[Infectious endocarditis caused by a glycopeptide-resistant enterococus]

Enterococci are an important cause of infective endocarditis. Their resistance to most of the antibiotics involve real therapeutic problems. We report the first clinical isolate of glycopeptide resistant enterococcus from blood culture of patient with a prosthetic valve endocarditis. The strain is an E. faecium with a high level of resistance to vancomycin and teicoplanin (MIC > 256 mg/l), a low level of resistance to gentamycin (MIC = 6 mg/l) and susceptible to ampicillin (MIC = 1.5 mg/l). Therapeutic failure was observed leading to a surgical treatment. Therapy of such infection caused by multiresistant Enterococcus must be based on the study of bactericidal activity of antibiotic associations. In order to control the spread of this emerging resistance, the implementation of control measures is necessary.

[Study of the incidence and cost of nosocomial infections in general surgery]

Nosocomial infection incidence and its cost were study. We have identified 61 infected patients and 75 infectious episodes, is an incidence of 9.4% infected for 100 hospitalized by trimester. Operative site infections are the most frequent (60%), operative site infection (9.1%), inferior respiratory ways infections (2.2%). Incriminated germs are represented essentially by negative gram Bacillus (77.3%) with predominance of enterobacterias (59%). Invasive technique usage, surgery types and contamination classes have been identified as risk factors of nosocomial infection occurrence. The supplementary stay duration estimated by simple comparison between infected group and no-infected one is 9.3% days, responsible of an over cost of 336 TD by infected patient and 273 TD by infectious episode. The curative antibiotic costs have been estimated at 70 TD by infected patient being equivalent to two hospitalization days and to 57 TD by infectious episode.

Characterisation of CMY-4, an AmpC-type plasmid-mediated beta-lactamase in a Tunisian clinical isolate of Proteus mirabilis

A strain of Proteus mirabilis resistant to beta-lactams, including cefoxitin, was isolated from the urine of a woman from Tunisia. Its antibiotic susceptibility pattern and that of the Escherichia coli transconjugant suggested the presence of an AmpC-type beta-lactamase. Two bands of beta-lactamase activity (pI 5.4 and 9.2) were detected by isoelectric focusing. The nucleotide sequence of the gene encoding the AmpC-type enzyme was determined. The deduced amino acid sequence was 98-99% identical to CMY-3 and to those of the plasmid-mediated AmpC-type beta-lactamases originated from Citrobacter freundii and 97% identical to the chromosome-encoded beta-lactamase of a Tunisian clinical isolate of C. freundii. This enzyme differs from CMY-2 by one substitution (Arg for Trp at position 221) and from CMY-3 by two substitutions (Glu for Gly at position 42 and Ser for Asn at position 363) and we propose the denomination CMY-4.

[Conjugative and non-conjugative plasmids in Salmonella serovar Wien coded for broad-spectrum beta-lactamase]

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. Decrease of incidence in a medical resuscitation unit at CHU Charles-Nicolle in Tunis]

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.

[Epidemiological pattern of the resistance of 153 Salmonella strains (S. typhi excluded) isolated in a Tunisian pediatric unit from 1985 to 1990]

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.

[Septicemia caused by A, B, C and G groups of beta-hemolytic streptococci]

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.

[Non-typhoid Salmonella in pediatric patients in Tunis (Hospital Charles-Nicolle) from 1980 to 1991]

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.

[Study of antibiotic sensitivity of Streptococcus pyogenes isolated in the hospital milieu (Charles Nicolle hospital of Tunis)]

The purpose of the present work was to investigate the susceptibility of S. pyogenes to antimicrobial agents. The strains have been taken from the bacteriological Service of Charles Nicolle's hospital at Tunis, and that during the period from January 1988- to December 1990. The antibiogram results as well as the minimal inhibitrice concentration determined by the agar diffusion technique, reveal that S. pyogenes continues to be very susceptible to the beta-lactamins (M.I.C. of penicillin G is "0.15 for 50% of strains tested. Resistance are noted for chloramphenicol; tetracycline and novobiocine (13%, 93%, 80%) not considered as good antibiotics anti-streptococcies. The macrolids are effective against S. pyogenes (100% of susceptibility) that's they are considered as the best alternating antimicrobiologents to the beta-lactamins (M.I.C. of erythromycin is 0.015.

[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.