Susceptibilities to antibiotics and antiseptics of new species of the family Enterobacteriaceae

Abstract

One hundred and sixty-nine strains of new species of the family Enterobacteriaceae, isolated mainly from the environment, were tested to determine their susceptibilities to 13 antibiotics and 4 antiseptics or disinfectants. All the species were susceptible to aminoglycosides, doxycycline, and trimethoprim but were resistant to chloramphenicol. Susceptibility to ,-lactams varied more among the strains. However, all the strains were cefotaxime susceptible, apart from some Buttiauxella agrestis strains for which MICs were greater than 256 ,ug/ml. The antiseptic MBCs were similar to those published elsewhere for species of the Enterobacteriaceae of clinical origin. No resistance to chlorhexidine was observed. On the other hand, the environmental strains presented a greater resistance to active chlorine than did the reference strains.Members of the family Enterobacteriaceae are the most common cause of nosocomial infections (8). In 15 years, the number of enterobacterial species has grown from about 20 to more than 130. The exact clinical significance of these new species, which are often detected in a wet environment (e.g., water and soil), remains largely unknown. However, they are isolated with growing frequency during pathogenic processes, especially in immunosuppressed subjects (4).The present study was aimed at evaluating the susceptibilities to 13 antibiotics and 4 antiseptics or disinfectants of 169 strains of new species of Enterobacteriaceae which were isolated mainly from the environment. MATERIALS AND METHODSOrganisms. A total of 169 strains representing 22 newly described species of Enterobacteriaceae were tested. Of these, 17 strains were from sewage, 26 were from surface water, 38 were from soil, 58 were from drinking water, and 30 were of medical origin. The species were identified as previously described (2).Antibiotics. The 13 antibiotics tested were supplied in the form of powders. The antibiotics and their sources were as follows: ampicillin and amikacin (Bristol, Paris, France), amoxicillin-clavulanic acid and ticarcillin (Beecham, Paris, France), cephalothin (Glaxo, Paris, France), cefoxitin (Merck Sharp & Dohme, Paris, France), cefotaxime (Roussel-Uclaf, Romainville, France), gentamicin (Unilabo, Dardilly, France), tobramycin (Lilly, Saint-Cloud, France), doxycycline (Pfizer, Orsay, France), trimethoprim (Roche, Neuilly-sur-Seine, France), chloramphenicol (Clin-Midy, Paris, France), and colistin (Roger Bellon, Neuilly-surSeine, France).The MICs were determined by the microdilution method (1). The various antibiotic dilutions were prepared according to a twofold geometric progression in the culture medium, which was Mueller-Hinton broth (pH 7.4) supplemented with 50 p.g of calcium per ml and 25 mg of magnesium per ml.Portions (100 RI) were placed in the wells of a microdilution plate. The bacterial inoculum obtained by a 10-2 dilution after incubation for 18 h at 35°C in brain heart broth was * Corresponding author. Antiseptics and disinfectants. We tested 5% aqueous chlorhexidine digluconate (I...

Natural antibiotic susceptibility of Klebsiella pneumoniae, K. oxytoca, K. planticola, K. ornithinolytica and K. terrigena strains

“…Because of higher MIC values to all â-lactam agents it is likely that the strains included in the latter study showed an increased â-lactamase expression compared with strains in the present study. Comparison of the results of the present study with those of the study by Freney et al [27], by examining the antibiotic susceptibility of K. terrigena and K. planticola, could lead to erroneous conclusions, because only MIC50 and MIC90 values were cited. Nevertheless, the MICs of ampicillin for 90% of K. planticola strains in this study were 4 mg=L, which would correlate with the natural ampicillin sensitivity of the species.…”

Potential Impact of Increased Use of Biocides in Consumer Products on Prevalence of Antibiotic Resistance

“…Such changes, in the case of the Providencia isolates, were thought to affect binding of the biguanides to the cell surface and therefore reflected envelope modification (74). Freney et al (82) found no evidence of decreased susceptibility within 169 novel Enterobacteriaceae isolated from the general environment relative to clinical isolates. Arguably, such studies support the view that antiseptic use in hospitals does not contribute to the biocide susceptibilities of enterococcal isolates.…”

Impact of an Urban Effluent on Antibiotic Resistance of Riverine Enterobacteriaceae and Aeromonas spp

“…After 24 h of incubation at either 37°C (Enterobacteriaceae) or 30°C (Aeromonas), organisms were classified as sensitive, intermediate, or resistant according to French national guidelines (17). Acquired resistances were deduced from data on wild-type antibiotic susceptibility patterns characteristic of each species (17,19,37,40). Strains with a decreased susceptibility were considered low-level resistant.…”