Replicon typing of 71 multiresistant Serratia marcescens strains.

Replicon typing is the identification of plasmids by hybridization with specific DNA probes which contain the genes involved in plasmid maintenance. This new method has been used to classify plasmids into replicon (rep) groups which can often be correlated with incompatibility (Inc) groups. We studied 71 multiresistant Serratia marcescens strains with 19 rep probes constructed from reference plasmid replicons belonging to known Inc groups. These probes are known to react with enteric bacterial plasmids. However, they did not represent the totality of the thirty known Inc groups. For 52% of the studied strains, plasmids were identified and classified into groups FIB, FIC, FIIA, HI2, L/M, N, B/O, P, W, Y and Com9. Most (79%) of the plasmid preparations hybridized with a single rep probe, and 21% hybridized with two different probes. Electrophoretic analysis of DNA suggested that double hybridization could result from the presence of either two different Inc plasmids in the same strain (e.g. S37) or one single plasmid with a multireplicon (e.g. S113).

Use of pulsed-field gel electrophoresis as an epidemiologic tool during an outbreak of Pseudomonas aeruginosa lung infections in an intensive care unit.

OBJECTIVE: A retrospective study was performed to evaluate the use of DNA polymorphism analysis by pulsed-field gel electrophoresis (PFGE) in assessing the rate of exogenous contamination during an outbreak of Pseudomonas aeruginosa lung infections in an intensive care unit ICU. Another goal was to determine the risk factors, involved in the outbreak. DESIGN: Rectal swabs and tracheal secretions were cultured from all patients upon admission and thereafter once a week throughout their stay in the ICU. Resistance patterns were determined in all P. aeruginosa isolates. We determined the serotypes, pyocin types, plasmid profiles and total DNA macrorestriction patterns for isolates. The restriction fragment length polymorphism (RFLP) of Dra I total DNA digest was studied by PFGE. A retrospective case-control study was performed to determine the risk factors for P. aeruginosa bronchopulmonary colonization. SETTING: The study was carried out in the medical ICU of Besancon University Hospital (France). RESULTS: The typability, stability and reproducibility of phenotypic markers were not completely satisfactory. Only the RFLP profile satisfied all the criteria for a good typing technique. In four of the 17 patients, P. aeruginosa strains with the same DNA pattern were found. Among the previously reported risk factors for hospital-acquired bronchopulmonary infections, only invasive procedures were determined by multivariate analysis to be significant in our study group. The oropharynx and the bronchial tract are the most likely endogenous sources. CONCLUSION: PFGE-RFLP is a valuable tool for the epidemiologic study of P. aeruginosa. This typing method revealed that exogenous contamination is not always the major source of P. aeruginosa lung infections in mechanically ventilated patients in ICUs.

Discriminatory power and usefulness of pulsed-field gel electrophoresis in epidemiological studies of Pseudomonas aeruginosa.

We assessed the discriminatory power of pulsed-field gel electrophoresis (PFGE) for the analysis of DNA restriction fragment length polymorphism (RFLP) in Pseudomonas aeruginosa. We determined DraI PFGE-RFLP of DNA of unrelated clinical and environmental strains, and clinical strains isolated from two intensive care units of the Besançon University Hospital. The typeability and reproducibility was 100%. The discriminatory index was 0.998, and the DNA patterns were stable in vitro and in vivo. There was a very low correlation between PFGE-RFLP and traditional typing methods. The typeability, reproducibility, the high discriminatory power and the stability of PFGE-RFLP make this a valuable method to be used in conjunction with serotyping. Further standardization and quantitative interpretation are possible and should lead to this technique becoming a library typing system.

Nasal carriage of Staphylococcus aureus and cross-contamination in a surgical intensive care unit: efficacy of mupirocin ointment.

A six month prospective study was carried out in a surgical intensive care unit (SICU) of a university hospital to assess the incidence and routes of exogenous colonization by Staphylococcus aureus. A total of 157 patients were included in the study. One thousand one hundred and eleven specimens (nasal, surgical wound swabs, tracheal secretions obtained on admission and once a week thereafter, and all clinical specimens) were collected over a four month period from patients without nasal decontamination (A). They were compared with 729 specimens collected over a two month period from patients treated with nasal mupirocin ointment (B). All S. aureus strains were typed by restriction fragment length polymorphism (RFLP) pulsed-field gel electrophoresis after SmaI macrorestriction. The nasal colonization rates on admission were 25.5 and 32.7% in groups A and B, respectively. Thirty-one untreated patients (31.3%) and three patients (5.1%) treated with nasal ointment, acquired the nasal S. aureus in the SICU (P = 0.00027). Nasal carriers were more frequently colonized in the bronchopulmonary tract (Bp) and surgical wound (Sw) (62%) than patients who were not nasal carriers (14%) (P < 0.00001). The patterns were identical for nasal, Bp and Sw strains from the same patient. RFLP analysis characterized seven epidemic strains of methicillin-resistant S. aureus (MRSA) which colonized 60% of group A and 9% of group B patients (P < 0.00001). The bronchopulmonary tract infection rate was reduced in group B (P = 0.032). In conclusion, in an SICU, nasal carriage of S. aureus appeared to be the source of endogenous and cross-colonization. The use of nasal mupirocin ointment reduced the incidence of Bp and Sw colonization, as well as the MRSA infection rate.

Typing of hospital strains of Xanthomonas maltophilia by pulsed-field gel electrophoresis.

We report the use of pulsed-field gel electrophoresis (PFGE) to characterize Xanthomonas maltophilia isolates from an incident of hospital-acquired infection over a 12-day period in a haematological unit. Ten isolates from five patients (from throat, urine, stool and blood) and two isolates from environmental sites in the unit were compared with 10 epidemiologically unrelated clinical strains, isolated over a 3-month period from several units in two hospitals, by PFGE of DraI digests of chromosomal DNA. The profiles obtained were stable, reproducible and discriminatory. The 10 unrelated strains had different DNA profiles. Each of the five patients in the unit was colonized by a different strain and the isolates from a water faucet and a shower pommel had the same DNA profile as the strains of two patients who had used these fittings. A case-controlled study showed that the only factor that correlated with colonization was the origin of the patient from another unit (P = 0.0122). We conclude that PFGE is a rapid and discriminatory technique for the typing of X. maltophilia where a common origin of infection is suspected.

[Organ culture preservation of the human cornea at +31 degrees C and risk of infection]. / Conservation en culture d'organe à +31 degrees C de la cornée humaine et risque infectieux.

PURPOSE: In order to reduce the risk of infection, we analyzed each stage of conservation of human cornea in organ culture at +31 degrees C. METHODS: This epidomiological study was conducted in 266 human corneas preserved in organ culture between January 1991 and December 1993. There were 3 stages: In the period of preservation (analysis of the contaminated medium), Before clinical use of the graft (analysis of the preservation medium), After the penetrating keratoplasty (analysis of the corneo-scleral rim and the transportation medium). The bacteriological media used were thioglycolate broth, trypticase soja and Sabouraud. RESULTS: In 266 storage media, 42 (15.7%) cultures are positive. The most commonly found organism was Staphylococcus aureus (21.4%). At the end of the conservation procedure, all of the cultures of the media were sterile (n = 165). After penetrating keratoplasty, 8 cultures were positive for the transportation medium and the corneo-scleral rim (5.1%), 3 cultures were positive for the corneo-scleral rim only (1.9%) and 5 cultures were positive (3.2%) for the transportation medium without contamination of the corneo-scleral rim. CONCLUSION: Preservation at +31 degrees C in organ culture of human corneas allows elimination of the contaminated or potentially contaminant corneas before an eventual transplantation. In our experience, the risk of infection is especially situated in the period of preservation which shows the insuffiency of the decontamination procedures or the antibiotical content of the medium and probably the virulence of the organisms in donors hospitalized for long period.

[Listeriosis in patients with malignant hemopathy. 3 cases in the same hospital ward]. / Listériose chez des malades ayant une hémopathie maligne. Trois observations dans un même service.

During the listeriosis epidemic which occurred in France in the summer 1992, three patients with malignant haematopathies hospitalized in our service contracted the disease. Although the retrospective investigations were hindered by the variable incubation period and the impossibility of examining the foods eaten at the time of infection, there was a high probability that two of the patients had been infected by cooked ham and dairy products at home. The third patient was apparently infected in hospital with well-cooked food found to be contaminated. The hypothesis of coinfection has been raised.

[Pseudomonas aeruginosa septicemia. Host-related risk factors in 82 episodes]. / Septicémies à Pseudomonas aeruginosa. Facteurs de risque liés à l'hôte au cours de 82 épisodes.

OBJECTIVES: The prognosis of septicaemia due to Pseudomonas aeruginosa is severe with mortality ranging from 32 to 73%. We retrospectively studied 82 episodes in order to determine whether risk factors could be identified. METHODS: Eighty-two episodes of Pseudomonas aeruginosa septicaemia, observed between 1986 and 1991, were analyzed. Risk of death within 2 days of the first positive blood culture (mortality = 19.5%) were assessed with univariate and multivariate analyses. RESULTS: Patient age ranged from 1 to 92 years. Most had been hospitalized in medical wards (49%) or intensive care units (28%) (NS). The type of septicaemia (several bacteria in 21%), the source of the infection (nosocomial in 78%), portal, predisposing factors (cancer, haematologic disease: 54%) and MacCabe index were not significantly correlated with risk of death at two days following first positive blood culture. With univariate analysis body temperature below 38,5 degrees C was significant (p = 0.007) for death at day 2 and appropriate antibiotic treatment after diagnosis was significant (p < 0.001) for absence of death on day 2. For multivariate analysis, chemotherapy and shock syndrome were significant (p = 0.005 and 0.09 respectively) for death at day 2 and appropriate antibiotic treatment was significant (p = 0.005) for absence of death on day 2. CONCLUSION: Antibiotic prescription appears to be the most easily controlled significant factor predictive of outcome in Pseudomonas aeruginosa septicaemia.

[Pseudomonas aeruginosa infection in cystic fibrosis: predominance of a single strain and the influence of antibiotic therapy and the environment]. / Infection à bacille pyocyanique au cours de la mucoviscidose: prédominance d'un clone, influence des antibiotiques et de l'environnement.

We analysed the implantation pattern and persistence of Pseudomonas aeruginosa in the tracheobronchial tracts of patients with cystic fibrosis, and investigated the relation of this bacterium with the environment and antibiotic therapy. We used four different techniques to ensure the precise and detailed identification of isolates. In particular, chromosomal differences were assessed by pulsed field electrophoresis (pulsotype determination). Sputum samples were collected from 8 patients, from 6 to 22 years-old, over a period of 19 to 24 months. Only a single strain was isolated from samples from each five patients taken at different times, and there was a predominant strain in the samples from two others. Patient 8, aged 14, was free of infection throughout the study. None of the infections was eradicated by antibiotic therapy (an association of two antibiotics for 15 days at one or two months interval). The strains isolated from two patients became resistant to imipenem: 3 out of the 4 resistant strains were the result of mutation in the resident, susceptible strain. Swabs were taken from the environments of infected patients and were tested for P. aeruginosa: this bacteria was found in three sites, and two of these contained an isolate with the same pulsotype as the strain responsible for the infection, whereas no P. aeruginosa was detected in the environment of an uninfected patient. The detailed and accurate identification of the isolates (by pulsotyping) enabled us--to show that each infected patient was infected by a single or predominant strain,--to investigate the relationship of these strains with those in the environment and the effects of antibiotic therapy.

[Extrachromosomal antibiotic resistance of the intestinal bacterial flora. II. The role of resistance acquired by endogenous intestinal bacterial flora (author's transl)]. / Résistance extrachromosomique aux antibiotiques de la flore bactérienne intestinale. II. Rôle de la résistance acquise par les bactéries intestinales résidentes.

In a previous paper, we have shown that multiple resistant bacteria in the human gut flora may have two origins: firstly, through food which carries resistant bacteria and secondly, our present study, resident intestinal bacteria which become resistant to antibiotics, either because they are chromosomic mutant or because they acquire resistance plasmid from an exogen strain. In all cases these resistant bacteria can implant and multiply in the gut only if there are disorders in the normal bacterial equilibrium. Antibiotherapy can create this inbalance and especially if it is not carefully followed up: it selects resistant bacteria, allows their implantation, and promotes plasmid R transfer. The resistant bacteria are able, in some cases, to spread out from the intestinal tract and give rise to further infections.

[Mechanism of action of antibiotics:some examples]. / Mécanismes d'action des antibiotiques, à propos de quelques exemples.

Antibiotics are very commonly used substances to eradicate bacterial infections by bacteriostatic or even bactericid effect. They act at a very specific stage (target), although other less important or secondary interactions can occur. We studied the interaction of three antibiotic families (beta-lactamins, aminosides, rifampicin) with bacterial cell. Penicillin disturbs the cell wall synthesis and more accurately the glycopeptide (or murein) formation, a substance giving rigidity or shape to bacteria. It acts in the late phase of murein-biosynthesis, when N-acetyl glucosamin -- N-acetyl muramic acid L ala -D glu M-DAP (L lys) -D ala -D ala are linked together by the peptide part, under the effect of several enzymes, particularly transpeptidase and DD-carboxy-peptidase. It would appear that beta-lactame-thiazolidine rings have a steric analogy with dipeptide D-alanyl D-alanine. The result would be that the enzyme would act on the antibiotic instead of peptide: the consequence would be inhibition of the peptidic link, giving an abnormal murein, and an incomplete cell wall i.e. fragile bacteria. Aminosides, particularly Streptomycin, link themselves to 30 S subunit of bacterial ribosome. In this case, it seems that it is a 3''OH function which reacts with lysine (from S 12 protein part of 30 S subunit). The consequence is an alteration in the RNA messager lecture, and a false traduction and consequently protein biosynthesis stops with a decrease of polyribosomes and of the formation of inert 70 S ribosome. Rifamycins, and particularly Rifampicin act by inhibition of RNA messager synthesis. One molecule of antibiotic links itself to one molecule of RNA messager : hydroxyl and cetone function in C1 Cs C21 C23 and "ansa" bridge link to beta subunit of RNA polymerase. This linkage gives a conformational change to the RNA polymerase-DNA complex, inhibiting the catalytic action of this enzyme, and consequently stopping RNA messager and protein synthesis. The study of the action mechanism of these antibiotics enables us to show the action specificity of these products in the bacteria. This specificity is more accurate when the target is not to be found in the eucaryotic cells : in this case the antibiotic may be considered as entirely atoxic. If the study of the action mechanism of antibiotics gives a better understanding of the use of these drugs, their action at a definite stage in bacterial metabolism is a valuable tool for scientists in their approach to cell functioning.

[Extrachromosomal antibiotic resistance of the intestinal bacterial flora. I. Prevalence. Role of the ingestion of exogenous bacteria (author's transl)]. / Résistance extrachromosomique de la flore bactérienne intestinal aux antibiotiques. I. Fréquence. Rôle de l'ingestion de bactéries exogènes.

Studies on the antibiotic resistance of bacterial flora isolated from stool, over these last ten years, have shown an increase of resistant strains to antibiotics. This resistance may depend on genes localized on the chromosome, or more frequently on extra-chromosomic DNA (R plasmid) which carries resistance to several antibiotic groups and which is spreading. The origin of multiple resistant bacteria could be twofold. The only one, which is considered in this paper, is the intake of exogenous bacteria already resistant and carried in food: beef, pork, chicken, having had some form of antibiotics--either supplementation to feeding to improve growth-or for prophylactic or therapeutic purposes.

[Transmissible resistance factor in Pseudomonas aeruginosa: arguments in favor of it being a plasmid]. / Facteur de résistance transmissible mis en évidence chez Pseudomonas aeruginosa: arguments en faveur de sa nature plasmidique

The transmissible Carbenicillin resistance factor R (56 BE) was isolated in Pseudomonas aeruginosa. It was not cured by usual agents and not isolated by ultra-centrifugation. So the plasmidic nature may be doubtful. We demonstrate in this paper that it is possible: 1) to transduce this factor into bacteria which is then able to conjugate and to transfer resistance to another bacteria, 2) to transfer carbenicillin resistance to arginine deficient strains without bringing chromosomic genes, 3) to obtain the carbenicillin resistance maintenance in Rec deficient strains. All these results are in favour of a plasmid.

[Professional brucellosis and endemic brucellosis in a given area]. / Brucelloses professionnelles et etat endémique brucellien dans une même région

An epidemiological survey was carried out in an area where there is an abattoir/canning factory in which a recrudescence of cases of professional brucellosis was observed: whilst there had been 29 cases of brucellosis in 8 years, 10 cases were confirmed in 1970. Our survey had underlined a brucellosis endemy in the population of that area: 32.50% of the patients had agglutinating or complement-fixing antibodies (698 people were examined). Results obtained have brought us to discuss the professional origin of brucellosis.