[New species of the genus Listeria: Listeria seeligeri]. / Une nouvelle espèce du genre Listeria: Listeria seeligeri.

Listeria seeligeri is a recently described species which shares 28% to 1% DNA relatedness with the other species of the genus Listeria. G + C% content of the type strain is 36. Peptidoglycan type (variation A1 gamma) as well as teichoic acids are identical to those found in L. monocytogenes. L. seeligeri can be easily distinguished from the other species using the following markers: hemolysis (CAMP-tests with Staphylococcus aureus and Rhodococcus equi) and acid production from D-xylose, L-rhamnose and alpha-methyl-D-mannoside. No specific antigen allow to characterize L. seeligeri strains which belong to serogroups 1/2 (81%), 4 (12%) and 6 (6%). 85% of these strains proved to be phage typable. So far, more than 100 strains were isolated, mainly in Europe, from environment and animal healthy carriers. Unless one case of meningitis in human, strains of this species are experimentally non virulent.

Characterization of Escherichia coli wild-type strains by means of agglutination with antisera raised against cloned P-, S-, and MS-fimbriae antigens, hemagglutination, serotyping and hemolysin production.

E. coli strains isolated from patients with urinary tract infections (UTI) very often possess mannose-sensitive (MS) and mannose-resistant (MR) adherence factors (fimbriae). According to their receptor specificity the mannose-resistant adhesins can be divided into several types, P, S, M and X. We have cloned the determinants of three groups of UTI E. coli adhesins, MS, P and S, and prepared specific antisera against the fimbriae antigens. 189 hemagglutination (HA+)-positive strains, 96 fecal isolates and 93 strains isolated from UTI have been tested with these specific antisera and further characterized by receptor specific HA, HA patterns and further of the "common O serogroups" 01, 02, 04, 06, 07, 08, 018, 025, 075, most prevalent in UTI, and hemolysin production. 68 (73%) of the UTI strains and 50 (52%) of the fecal isolates showed P-receptor specificity; 16 (17%) of the uropathogenic bacteria and 33 (34%) of the fecal strains exhibited S, M or X-fimbriae antigens. 24% of the P-hemagglutinating (P+) strains reacted with P (F8)-specific antiserum. In contrast, more than three quarter of the S+-strains were agglutinated by S-specific antiserum. HA-pattern VI and 018 antigen were found to be associated with P-fimbriae strains, whereas HA-pattern V and VII and the O antigens 02 (M-type), 06 and 018 (S-type) occurred most frequently in P--strains. A high percentage of P-fimbriated strains showed mannose-sensitive hemagglutination and hemolysin production.

[Acute purulent Listeria seelingeri meningitis in an immunocompetent adult]. / Méningite purulente aiguë à Listeria seeligeri chez un adulte immunocompétent.

Within the genus Listeria, the species L. monocytogenes most frequently causes disease in animals and humans. L. Seeligeri, a species recently described, has been considered experimentally nonpathogenic so far. The authors report the first case of human infection in a previously healthy adult presenting with acute purulent meningitis due to L. seeligeri. The patient recovered promptly after a course of ampicillin and gentamicin, but developed severe neurological sequelae (epilepsy, hydrocephalus) one year after the acute episode. The pathogenic properties of this isolate were investigated in two experimental animal models and the results were as follows. The clinical isolate of L. seeligeri was able to colonize the spleens of adult mice without bacterial multiplication, in contrast to the type strain of L. seeligeri (no colonization) and to a L. monocytogenes strain (colonization and multiplication). Previous infection of adult mice with the clinical L. seeligeri isolate protected moderately against spleen colonization and bacterial multiplication after challenge with L. monocytogenes. No lethal effect was observed after inoculation of suckling mice with the clinical L. seeligeri isolate, in contrast to L. monocytogenes strains. Thus, L. seeligeri, previously described as experimentally nonpathogenic for mice, may in fact be a heterogeneous species regarding its pathogenicity, and include strains that may cause life-threatening diseases in humans.

A multi-centre study on the phage typing of Listeria monocytogenes.

The aim of this multicenter study was to determine and to standardize methods in order to have common basis for comparing results of phage typing of Listeria monocytogenes. Using a common set of Listeria strains, a standardized method, including media, bacterial growth conditions, application of viruses and reading of lytic reactions, was established. 29 bacteriophages were selected according to their host range. This phage typing system allowed phagovar determination of 54% of the serogroup 1/2 strains and 77% of the serogroup 4 strains of L. monocytogenes.

[Isolation of Listeria seeligeri and L. welshimeri bacteriophages. Lysotyping of L. monocytogenes, L. ivanovii, L. innocua, L. seeligeri and L. welshimeri]. / Isolement de bactériophages de Listeria seeligeri et L. welshimeri. Lysotypie de L. monocytogenes, L. ivanovii, L. innocua, L. seeligeri et L. welshimeri.

Recent taxonomic reexamination of Listeria monocytogenes strains as defined in the 8th edition of Bergey's Manual of Determinative Bacteriology allowed to distinguish 5 species among these strains: L. monocytogenes, L. innocua, L. ivanovii, L. welshimeri, and L. seeligeri. As till now only the behaviour of the species L. monocytogenes, L. innocua, and L. ivanovii towards bacteriophages was characterized, the present study aimed at the search for phages occurring on these two new species and to determine their lytic activities towards representative strains of the whole genus. Seven different bacteriophages were isolated from the culture filtrates of 45 strains of L. seeligeri, whereas only one phage was obtained from the filtrates of 17 strains of L. welshimeri. No phage was isolated from the filtrates of L. grayi and L. murrayi strains with our methods. The phage preparations proved stable over a period of 6 to 12 months with titers ranging from 7 X 10(8) to 5 X 10(10). By use of a set of lytic phages which contained in addition to the eight new phages from L. welshimeri and L. seeligeri 23 known phages from L. monocytogenes, L. innocua, and L. ivanovii, 511 selected strains, originating from various sources, especially environment (125 strains), and belonging to all species of Listeria, were studied. 345 (68%) of the 511 strains could be assigned to a lysovar by means of the extended set. The eight new phages showed genus- and serogroup specificity but did not present species-specific reactions. The strains of L. grayi and L. murrayi were untypable using these 31 phages. No relationship between lysovar and serovar on the one side and host and geographic source on the other side was apparent.

Hemolytic Escherichia coli strains in the human fecal flora as potential urinary pathogens.

Hemolysin production is presumed to be a virulence factor in extraintestinal, e.g. urinary tract, infections caused by Escherichia coli. In order to investigate its incidence among the fecal flora, particularly in combination with other presumptive virulence factors, 369 and 373 fecal isolates from Würzburg, FRG and Lima, Peru respectively were examined. 12% of the former and 4% of the latter were hemolytic (Hly+) compared to 33% of 249 E. coli strains isolated from urinary tract infections in Würzburg. In comparison to those which were non hemolytic (Hly-), Hly+ fecal E. coli isolates were associated to a far greater extent with other factors implicated in urinary tract virulence. 41% of these Hly+ strains (cf. 8% Hly-) possessed mannose resistant hemagglutination (MRHA types V, VI, VII). In addition they belonged to the "common O serogroups" O1, O2, O4, O6, O7, O8, O18, O25, O75 in 61% of cases (cf. 25% Hly-) and they possessed K5 antigen in 13% of instances (cf. 2.5% Hly-). The occurrence of these three virulence factors among Hly+ fecal E. coli strains is very similar to that observed among E. coli urinary isolates. One may conclude that these Hly+ fecal strains constitute a "pool" of potential urinary tract pathogens.

[Effect of multiresistance on the minimal inhibitory concentration of N-formimidoyl thienamycin and 6 comparing substances against P. aeruginosa and 4 Enterobacteriaceae species]. / Der Einfluss der Mehrfachresistenz auf die minimalen Hemmkonzentrationen von N-Formimidoylthienamycin und sechs Vergleichssubstanzen bei P. aeruginosa und vier Enterobakteriazeen-Arten.

The minimal inhibitory concentrations (MICs) of multiresistant strains of P. aeruginosa and four species of Enterobacteriaceae were compared with those of more sensitive ones in N-f-thienamycin and six other antibiotics. The greatest difference between these two differently resistant bacterial populations was found in cefoperazone and the beta-lactamase-instable piperacillin. The latter was used for comparison purposes. The activity of cefsulodin was distinctly reduced in multiresistant strains of P. aeruginosa. Cefotaxime and lamoxactam displayed slightly elevated MICs in multiresistant strains. In N-f-thienamycin a significant difference between the multiresistant and the more sensitive population could not be verified (p greater than 0.05). In this regard it resembles fosfomycin. beta-lactam antibiotics could be ranked by means of correlation analysis of their MICs. Using piperacillin as a reference antibiotic the following order of succession could be arranged according to correlation coefficients in P. aeruginosa: cefoperazone, cefsulodin, lamoxactam, cefotaxime and N-f-thienamycin. For the Enterobacteriaceae species some antibiotics could not be evaluated in this test. Moreover, it was recognized that there was an obvious correlation between the activities of lamoxactam and cefotaxime in P. aeruginosa (r = 0.81) and E. coli (r = 0.80). A correlation was also observed between those of cefsulodin and cefoperazone in P. aeruginosa (r = 0.75). Lower correlation coefficients were seen in N-f-thienamycin with cefoperazone, piperacillin and cefsulodin in P. aeruginosa and with cefoperazone in Klebsiella spec.. Notwithstanding, strains resistant to cefsulodin and cefoperazone were inhibited by concentrations less than or equal to 8 micrograms/ml of N-f-thienamycin. These results showed that in N-f-thienamycin, cefotaxime and lamoxactam multiresistance has only a minimal influence on the MICs of the species of Enterobacteriaceae examined. For therapeutic considerations concerning multiresistance the small differences recognized among these three antibiotics might be without significance. However, N-f-thienamycin was distinctly more active in multiresistant strains of P. aeruginosa than the other beta-lactam antibiotics tested.

[Biochemical differentiation of the "Listeria monocytogenes" (sensu lato) genomic groups]. / Différenciation biochimique des groupes génomiques de Listeria monocytogenes (sensu lato).

CAMP-tests with Staphylococcus aureus and Rhodococcus equi and acid production from D-xylose allowed to separate the five DNA relatedness groups described for Listeria monocytogenes sensu lato; acid production from L-rhamnose and alpha-methyl-D-mannoside are secondary markers.

[Special position of strongly haemolytic strains of the genus Listeria]. / Zur Sonderstellung stark hämolysierender Stämme der Gattung Listeria.

The special status of the strongly haemolytic strains of serovar (sv) 5 of Listeria monocytogenes is reviewed. Besides some biochemical reactions sv 5 strains are characterized by their excessive haemolysis on sheep blood agar and by a positive result of the CAMP test with R. equi. The haemolysis is caused by a soluble thermolabile protein which stimulates the formation of antibodies and which is inhibited by cholesterol. Sv 5-strains are less virulent than strains of sv 1/2a and sv 4b. The antibiotic sensitivity patterns characteristic for listeriae and for the principles of treating Listeria infections, are valid for sv 5-strains, too. The special position of sv 5 versus the other serovars of L. monocytogenes - with particular reference to its biochemical activity, its haemolytic properties, its lysosensitivity and its pathogenicity - calls for a reconsideration of its taxonomic position within the genus Listeria.

Isolation of bacteriophages from Listeria monocytogenes Serovar 5 and Listeria innocua.

11 new bacteriophages, 3 from Listeria monocytogenes serovar 5 and 8 from Listeria innocua were isolated from lysogenic strains without induction. Phagovar determinations were carried out with these phages and 12 other isolated from L. monocytogenes serovars 1/2 and 4b. 76% of the 142 strains from different serovars tested gave a lytic pattern. The new phage set increased the percentage of determinable L. innocua strains to 61.7%. Different phage patterns underline the distinction between L. monocytogenes and L. innocua. L. monocytogenes serovar 5 is characterized by its great sensibility to many phages from lysogenic strains of various serovars.