[Treatment of bacterial pneumonias with cefuroxime-axetil. Predictive value of measurement of the in vitro susceptibility]. / Traitement des pneumonies bactériennes par le céfuroxime-axetil. Valeur prédictive de la mesure de la sensibilité in vitro.

Cefuroxime axetil is an oral cephalosporin with proven efficacy in adult lower respiratory tract infections. Indeed, it has a broad spectrum of activity in vitro, covering most pathogens isolated in this setting and showing good stability in the presence of betalactamases. In vitro susceptibility data are a major element in the choice of antimicrobial agent. The aim of this study was to determine the predictive value of the cefuroxime minimal inhibitory concentration (MIC) on the clinical outcome of infections treated with cefuroxime axetil. One hundred-and-seventeen (117) patients with radiologically confirmed community-acquired pneumonia of presumed bacterial origin were enrolled in a prospective multicenter trial of cefuroxime axetil therapy (500 mg twice daily). The pathogen was identified in 44 patients who were treated for a mean of 8.8 days. Most isolates were S. pneumoniae (65.9%) and H. influenzae (15.9%). The MIC was known for 35 isolates and was < or = 4 micrograms/ml in 30 cases (85.7%). The MIC value was a good predictor of clinical efficacy with a sensitivity of 100%, a specificity of 83% and a positive predictive value of 97%; the latter value indicates that therapeutic success is virtually certain when the bacterium causing pneumonia is susceptible to cefuroxime.

[Azithromycin: critical points]. / Azithromycine: points critiques.

The determination of the French breakpoints (< or = c, > C) were selected by the use of different criteria including bacteriological, pharmacokinetic and obviously clinical criteria. Concerning the bacteriological results, azithromycin, being an acid stable orally administered antimicrobial drug, is in vitro marginally less active than erythromycin against Gram-positive organisms including beta-haemolytic streptococci and Staphylococcus aureus. But in contrast, this azalide is more active than erytromycin against many Gram-negative pathogens, notably Neisseria gonorrhoeae, H. influenzae, Branhamella (Moraxella) catarrhalis, Ureaplasma urealyticum, and Borrelia burgdorferi. The activity of azithromycin is unaffected by the inoculum, unlike of pH, serum, and presence of CO2 for anaerobes. However, erythromycin-resistant micro-organisms are also resistant to azithromycin. Considering the pharmacokinetic criteria and the clinical results such as infections of the lower and upper respiratory tracts, skin and soft tissues, uncomplicated urethritis/cervicitis associated with N. gonorrhoeae, Chlamydia trachomatis or U. urealyticum, the preliminary breakpoints of azithromycin are defined by the following concentrations (< or = 0.12 and > 4 mg/l). Additional experimental and clinical results are required to confirm the in vitro activity against some other bacterial species (E. faecalis, L. monocytogenes, Brucella, P. multocida, or even Salmonella and Shigella).

Frequency of inhibitor-resistant TEM beta-lactamases in Escherichia coli isolates from urinary tract infections in France.

Over a six-month period in 1993, 2972 non-duplicated isolates of Escherichia coli causing urinary tract infections were collected in a French teaching hospital (n = 785) and in three private laboratories (n = 2187). The resistance rate to amoxycillin-clavulanate combination (MIC > 16 mg/l) was 25.0% in the hospital isolates and 10.0% in the community isolates. Respectively, 27.5% and 45.0% of hospital and community isolates resistant to amoxycillin-clavulanate exhibited an unusual beta-lactam resistance pattern, suggesting inhibitor-resistant TEM (IRT) beta-lactamase production. These isolates were highly resistant to amoxycillin-clavulanate (MIC90 > 1024 mg/L), but were susceptible to cephalosporins (MIC < 32 mg/L). Enzyme extracts of these IRT-producing strains focused at pI 5.2 (n = 100) or 5.4 (n = 53). DNA-DNA hybridization confirmed that the beta-lactamases involved in this resistance mechanism were TEM-1 derived and contained variations in the altered positions described in IRT enzymes. This study shows a total frequency of 4.9% of IRT-producing isolates among E. coli isolated from urine specimens.

Clinical isolates of Escherichia coli producing multiple TEM mutants resistant to beta-lactamase inhibitors.

Twenty clinical isolates of Escherichia coli resistant to amoxycillin and ticarcillin, both in combination with clavulanic acid, were studied. The ranges of MICs for these strains as determined by the agar dilution method were as follows: amoxycillin, 2048- > 4096 mg/L; ticarcillin, 512- > 4096 mg/L; piperacillin, 32-256 mg/L; mecillinam, 0.5-8 mg/L; and cephalothin 4-16 mg/L. Combining amoxycillin with beta-lactamase inhibitors, each at a fixed concentration of 4 mg/L, had only modest potentiating effects on the activities of this agent, the ranges of MICs falling to 256- > 2048 mg/L in the presence of clavulanic acid or sulbactam and to 64-1024 mg/L and 128-2048 mg/L in the presence of tazobactam and brobactam respectively. The pI values for the beta-lactamases produced by the 20 isolates were 5.2 for 15 strains, 5.4 for four strains and 7.4 for a single strain. Colony hybridization with oligonucleotides was performed in order to detect substitutions of arginine at position 241 (Arg-241) and methionine at position 67 (Met-67). Based on this technique, the four beta-lactamases with pI values of 5.4 were grouped into two oligotypes (+ = hybridization, - = non-hybridization)-Arg-241+, Met-67- (n = 3) and Arg-241+, Met-67+ (n = 1); in one of the three mutants which did not hybridize with the Met-67 probe, leucine had been substituted for methionine at position 67. The beta-lactamases with pI values of 5.2 which were identified in 15 strains were grouped into the following three oligotypes: Arg-241-, Met-67+ (n = 7); Arg-241-, Met-67- (n = 6); and Arg-241+, Met-67- (n = 2). In three of the 13 mutants which failed to hybridize with the Arg-241 probe, serine residues had replaced arginine residues at position 241. Substitutions of Arg-241 or Met-67 led to reduced affinities of the mutant enzymes for the beta-lactams tested. The results of the hybridization studies demonstrate that, amongst E. coli clinical isolates, there is a diversity of mutant TEM enzymes mediating resistance to beta-lactamase inhibitors.

In-vitro antibacterial activity of cefepime: a multicentre study.

The antimicrobial activity of cefepime, a new broad-spectrum parenteral cephalosporin, was evaluated in vitro against 1757 recent clinical Gram-positive and Gram-negative isolates. Cefepime was active at low concentrations (MIC50 values < or = 0.06 mg/L and MIC90 values < or = 0.12 mg/L) against non-cephalosporinase-producing Enterobacteriaceae (Escherichia coli, Proteus mirabilis, Salmonella spp. and Shigella spp.). For Klebsiella pneumoniae, MICs were between 0.016 and 16 mg/L; the highest MIC values were observed for extended-spectrum beta-lactamase-producing strains. Against Enterobacteriaceae, such as cephalosporinase producing Enterobacter cloacae, MICs were < or = 0.5 mg/L, but MICs against cephalosporinase hyperproducing strains were generally higher. Ticarcillin-sensitive strains of Pseudomonas aeruginosa were inhibited by cefepime concentrations of 0.5-16 mg/L, while cefepime MICs were 8-64 mg/L for strains resistant to ticarcillin. The cefepime MIC50 value for Haemophilus spp. including many resistant to amoxycillin, was 0.03 mg/L. Against methicillin-sensitive strains of Staphylococcus aureus, cefepime MICs were 0.5-16 mg/L; MICs against methicillin-resistant staphylococci were 16- > 128 mg/L). Against methicillin-sensitive coagulase-negative staphylococci, cefepime MIC values were 0.03-16 mg/L; corresponding values for methicillin-resistant strains were 2-128 mg/L. Streptococci (Groups A, C and G) were sensitive to cefepime with MICs ranging from < or = 0.008-2 mg/L (MIC50, 0.03 mg/L; MIC90, 0.25 mg/L). The activity of cefepime against Group B streptococci and pneumococci were comparable, with MIC50 values of 0.12 and 0.25 mg/L, respectively, and MIC90 values of 0.03 and 0.25 mg/L, respectively. Most enterococci and all Listeria monocytogenes strains had MICs > or = 32 mg/L.(ABSTRACT TRUNCATED AT 250 WORDS)

Nucleotide sequences of CAZ-2, CAZ-6, and CAZ-7 beta-lactamase genes.

CAZ-2, CAZ-6, and CAZ-7 are plasmid-mediated beta-lactamases that are markedly active against ceftazidime. The corresponding structural genes were amplified by the polymerase chain reaction. Nucleotide sequences were determined by direct sequencing of the amplified products. Analysis of the nucleotide and the deduced amino acid sequences showed that CAZ-2, CAZ-6, and CAZ-7 are derived from TEM-2 by three, four, and two amino acid substitutions, respectively. All these substitutions are located at positions 102, 162, 235, 236, and 237 (Sutcliffe numbering), which are known to extend the substrate range of beta-lactamases. These substitutions are Lys-102, Ser-162, and Ser-236 in CAZ-2; Lys-102, Ser-162, Thr-235, and Lys-237 in CAZ-6; and Lys-102 and His-162 in CAZ-7. These results indicate that the nucleotide sequence of CAZ-2 is identical to that of TEM-8. The nucleotide sequence of CAZ-7 possesses the two mutations described in TEM-16 by the oligotyping method. In contrast, the combination of mutations encountered in CAZ-6 has not yet been described, and this enzyme was designated TEM-24.

A collaborative study of the in-vitro sensitivity to RP 59500 of bacteria isolated in seven hospitals in France.

The in-vitro activity of RP 59500 was determined against 1051 recent clinical bacterial isolates. The susceptibility to RP 59500 was determined with an agar dilution technique for all the isolates, while MICs and MBCs were determined for 82 selected strains in broth. Isolates of both Staphylococcus aureus and coagulase-negative staphylococci appeared to be potentially susceptible to RP 59500, independent of susceptibility to methicillin or MLS resistance. (S. aureus: methicillin-sensitive, MIC90, 1.0 mg/L; methicillin-resistant, MIC90 1.0 mg/L; coagulase-negative staphylococci: methicillin-sensitive, MIC90 0.5 mg/L). Lancefield group A, B, C and G streptococci (MIC50 0.5 and MIC90 1.0 mg/L) and Streptococcus pneumoniae (MIC50 0.5 and MIC90 1.0 mg/L) appeared to be susceptible to RP 59500. Some Streptococcus spp. and enterococci as well as Listeria monocytogenes were inhibited by a higher concentration of RP 59500 (enterococci: MIC90 4 mg/L, range 0.125-16 mg/L). Comparatively low MICs were seen when Legionella spp., Neisseria gonorrhoeae and Gardnerella vaginalis were tested. Broth dilution MIC/MBC determinations showed no evidence of tolerance, as MIC values were within two dilutions of MBC values. RP 59500 might be a useful compound in the treatment of infections caused by a range of Gram-negative and Gram-positive bacteria, including those resistant to methicillin and/or macrolides.

Inhibition of Haemophilus influenzae adherence to buccal epithelial cells by cefuroxime.

We studied the effect of subinhibitory concentrations of cefuroxime on the capacity of Haemophilus influenzae to adhere to buccal epithelial cells (BEC). Two encapsulated strains (serotype b) and two nonencapsulated, nontypable strains were studied. All four strains adhered strongly to BEC, with indices (mean number of bacteria adhering to a single BEC) ranging from 19 to 48. Subinhibitory concentrations of cefuroxime (serial dilutions from MIC/2 to MIC/32) were added to cultures in tryptic soy broth and their effect on adherence was tested after 18 h incubation at 37 degrees C. Adherence was diminished by more than 50% by concentrations of cefuroxime ranging from MIC/2 to MIC/8 and varied according to the strain studied. These results show that the adherence of H. influenzae to BEC is inhibited by subinhibitory concentrations of cefuroxime.

Nosocomial rotavirus infections in adult renal transplant recipients.

We conducted a 24-month survey of hospital-acquired rotavirus infections in 20 renal transplant recipients who received their graft during 1988. Four cases of nosocomial rotavirus infection were diagnosed (20% of patients), 3-34 days after graft. Two patients presented with severe diarrhoea and two with fever alone. The cases occurred mainly during the winter months and remained sporadic. None of our patients was found to have chronic excretion of rotaviruses. Contacts from paediatric cases can be ruled out. We concluded that rotavirus nosocomial infections were frequent in adult renal transplant recipients and suggest that screening for rotavirus is regularly performed in these immunodeficient patients who are very susceptible to hypovolaemia.

[Frequency and distribution of beta-lactamases in 1792 strains of Klebsiella pneumoniae in France between 1985 and 1988]. / Fréquence et distribution des bêta-lactamases chez 1,792 souches de Klebsiella pneumoniae isolées en France entre 1985 et 1988.

In october 1985, 1987 and 1988, all the clinical isolates of K. pneumoniae (respectively 530, 654, 590 strains) were collected in 20 hospitals. The beta-lactamases were identified by analytical isoelectrofocusing and by substrate and inhibition profiles. 76 to 81% of the strains produced only one beta-lactamase: SHV-1 type, pI 7.7 (61 to 65%) or PI 7.1 (14%). The TEM-1 betalactamase (pI 5.4) was produced in 1985 by 21% of the strains, 9% in 1987, and 11% in 1988: TEM-2, pI 5.6 by 2% in 1985-87-88. The extended broad spectrum beta-lactamases, able to hydrolyse amino-thiazol-oximino-beta-lactam antibiotics, TEM or SHV type enzymes (SHV-2, pI 7.7, SHV-3, pI 7.1; SHV-4/CAZ-5, pI 7.8; SHV-5/CAZ-4 pI 8.2; CTX-1/TEM-3, pI 6.3) were also detected: 0.75% of the strain (3 strains) in 1985, 8.4% (55 strains) in 1987, 11% (65 strains) in 1988. These extended broad spectrum beta-lactamases were found in 2 hospitals in 1985, 10 in 1987 and 9 in 1988.

[Inhibition by nifurzide of the adhesion capacity of enteropathogenic colibacillus to HEP-2 cells]. / Inhibition par le nifurzide du pouvoir d'adhésion des colibacilles entéropathogènes aux cellules HEP-2.

Enteropathogenic Escherichia coli (EPEC) adhere in vivo to enterocytes. This adhesion capacity can be obtained in vitro with Hep-2 cells on which a characteristic localized adherence (LA) is observed. We studied the effect of subinhibitory concentrations (SIC) of nifurzide, a nitrofurane derivative, on this bacterial adherence phenomenon. Three EPEC strains are used: 11201 (026 serogroup), 7958 (0128) and 7836 (0142). Various SIC (MIC/2; MIC/4;...; MIC/32) were added either to the culture medium of bacteria or to the Eagle medium in which bacteria and Hep-2 cells were mixed during the adhesion experiments. In each case an adhesion index is determined. Nifurzide strongly inhibits the adherence capacity of the three strains when concentrations ranging from MIC/2 to MIC/16 where added in both culture media. On the other hand three other nitrofurane derivatives which have no antibacterial effect did not inhibit adherence. The mechanism of the adherence inhibition by nifurzide is discussed.

Multiplicity of TEM-derived beta-lactamases from Klebsiella pneumoniae strains isolated at the same hospital and relationships between the responsible plasmids.

Five plasmid-mediated beta-lactamases conferring high-level resistance to ceftazidime were isolated from Klebsiella pneumoniae strains in the same hospital. These enzymes had isoelectric points ranging from 5.3 to 6.5 (CAZ-1, 5.55; CAZ-2, 6.0; CAZ-3, 5.3; CAZ-6, 6.5; and CAZ-7, 6.3). All isolates and their Escherichia coli transconjugants were highly resistant to amoxicillin (MICs, greater than 4,096 micrograms/ml), piperacillin (64 to 256 micrograms/ml), cephalothin (32 to 256 micrograms/ml), and ceftazidime (32 to 512 micrograms/ml) but remained moderately susceptible to cefotaxime (0.5 to 8 micrograms/ml). Only CAZ-6- and CAZ-7-producing strains were highly resistant to aztreonam (64 to 128 micrograms/ml). All the isolates remained susceptible to moxalactam and imipenem. The reduced activity of piperacillin, cefotaxime, ceftazidime, or aztreonam was restored by 2 micrograms of clavulanate, sulbactam, tazobactam, or brobactam per ml for E. coli producing CAZ-2, CAZ-3, and CAZ-7. Sulbactam had a lower protective effect than other inhibitors for E. coli harboring CAZ-1 and especially CAZ-6. Except for CAZ-1, which was mediated by a 150-kilobase (kb) plasmid (pCFF14), the other ceftazidimases were mediated by plasmids of 85 kb with EcoRI digestion patterns similar to that of pCFF04 encoding CTX-1 beta-lactamase. A TEM probe hybridized with a 19-kb EcoRI fragment of all these closely related plasmids.

Comparative study of five plasmid-mediated ceftazidimases isolated in Klebsiella pneumoniae.

Five plasmid-mediated beta-lactamases conferring a high level of resistance to ceftazidime were isolated from Klebsiella pneumoniae strains. These ceftazidimases (CAZ) differed in their isoelectric point (from 5.3 to 8.2) and were encoded by large self-transferable plasmids of 85 kb (CAZ-2, CAZ-3) or greater than or equal to 150 kb (CAZ-1, CAZ-4, CAZ-5). The 85 kb plasmids seemed closely related to pCFF04 encoding CTX-1 enzyme and belonged to the same incompatibility group 7 or M. These beta-lactamases hydrolysed all beta-lactams with the exception of cephamycins and carbapenems. For CAZ-1, CAZ-2 and CAZ-3 producers, MICs of ceftazidime (32-256 mg/l) were higher than MICs of cefotaxime (0.12-2 mg/l) and aztreonam (1-16 mg/l). For the strains producing the beta-lactamases CAZ-4 and CAZ-5, MICs of aztreonam were the highest (greater than or equal to 256 mg/l). The impaired activities of cephalosporins and monobactams were restored equally well by 2 mg/l of clavulanate, sulbactam and CL-298741 for CAZ-2 producing strains (wild type and transconjugant). Sulbactam (2 mg/l) had a lower protective effect than other inhibitors on ceftazidime for CAZ-1 and CAZ-3 producing K. pneumoniae. The protective effect of sulbactam (2 mg/l) was lower than that of the other inhibitors on all beta-lactams for CAZ-4 and CAZ-5 producers. The enzymes CAZ-1, CAZ-2 and CAZ-3 derived from TEM beta-lactamase whereas CAZ-4 and CAZ-5 derived from SHV-1 enzyme.

Comparative in-vitro activity of meropenem against clinical isolates including Enterobacteriaceae with expanded-spectrum beta-lactamases.

Meropenem, a new parenteral carbapenem, was tested in vitro by an agar-dilution method against 373 standard strains (aerobes and anaerobes) and against nine expanded-spectrum beta-lactamase-producing strains and their transconjugants (5 CTX-1, 2 CAZ-1, 2 CAZ-2). Meropenem was compared with methicillin, imipenem, piperacillin, cefoxitin, cefotaxime, ceftazidime, gentamicin, chloramphenicol, clindamycin, ciprofloxacin, vancomycin and metronidazole. Meropenem and imipenem exhibited an extended spectrum of activity, with low MICs. Only methicillin-resistant staphylococci, and Pseudomonas (Xanthomonas) maltophilia were resistant. Of the carbapenems, imipenem was more active against methicillin-susceptible staphylococci, streptococci and Enterococcus faecalis, but meropenem was markedly more active against all the Enterobacteriaceae and some pseudomonads. Both had similar activity against Ps. aeruginosa, Acinetobacter spp. and anaerobes. The carbapenem MICs were very low for Enterol acteriaceae producing the expanded-spectrum beta-lactamases. Against CTX-1-producing strains resistant to cefotaxime and ceftazidime and against CAZ-1 or CAZ-2-producers highly resistant to ceftazidime meropenem was the most active, with MICs lower (0.03-0.12 mg/l) than those of imipenem (0.06-0.5 mg/l), for wild type producers and their transconjugants.

Comparative study of a novel plasmid-mediated beta-lactamase, CAZ-2, and the CTX-1 and CAZ-1 enzymes conferring resistance to broad-spectrum cephalosporins.

Infections caused by strains of Klebsiella pneumoniae resistant to broad-spectrum cephalosporins have been observed recently in hospitals in Clermont-Ferrand, France. beta-Lactam resistance resulted primarily from the plasmid-mediated, expanded-spectrum CTX-1 beta-lactamase. Furthermore, since 1987 some K. pneumoniae isolates more resistant to ceftazidime than to other cephalosporins have been observed. This new resistance phenotype was the result of the production of ceftazidimase CAZ-1 and, more recently, CAZ-2. As in CTX-1-producing strains, resistance to beta-lactams resulting from CAZ-2 was associated with resistance to aminoglycosides except gentamicin, sulfonamide, and tetracycline and was transferable to Escherichia coli by conjugation. Agarose gel electrophoresis of plasmid DNA from wild-type strains and transconjugants indicated that CAZ-2 production was mediated by a plasmid of 85 kilobases highly related to plasmid pCFF04 coding for CTX-1 beta-lactamase. The isoelectric point, close to 6.0, of this novel enzyme differed from those of CTX-1 and CAZ-1. Like CAZ-1, the CAZ-2 enzyme efficiently hydrolyzed ceftazidime and aztreonam, but as with CTX-1, cefotaxime gave the maximal reaction rate. For each expanded-spectrum beta-lactamase, the activity of broad-spectrum cephalosporins was restored by clavulanic acid or sulbactam.

[Sensitivity of Pseudomonas aeruginosa and Klebsiella spp. to ceftazidime. Current status in France]. / Sensibilité des Pseudomonas aeruginosa et des Klebsiella à la ceftazidime. Etat actuel en France.

Ceftazidime was tested against 2,224 strains of Pseudomonas aeruginosa obtained from 17 hospitals in April, May and June, 1986 and against 607 strains of Klebsiella pneumoniae and 234 strains of K. oxytoca obtained from 16 hospitals in October, 1987. The MIC's of ceftazidime against P. aeruginosa were distributed normally, with an MIC50 of 2 mg/l and an MIC90 of 4 mg/l. Depending on critical concentrations, 80 per cent of strains were sensitive, 11.4 per cent were of intermediate sensitivity and 0.54 per cent were resistant. There were few differences in results between hospitals. Ninety-two per cent of resistant strains and 45 per cent of intermediate strains (as opposed to 6 per cent of all strains) produced a high-level constitutive cephalosporinase with little variations between centres. The MIC's of ceftazidime against K. pneumoniae and K. oxytoca had a bimodal distribution: 91 per cent of strains were sensitive to 0.25 mg/l, 6 per cent of strains showed intermediate sensitivity and 3 per cent were resistant. All intermediate and resistant strains produced a very broad spectrum beta-lactamase which hydrolyzed some of the third generation cephalosporins: K. pneumoniae 36 CTX-1, 5 SHV-2, and 14 strains producing a recently identified beta-lactamase "CAZ-5/SHV-4"; K. oxytoca 3 CTX-1. These strains were isolated in 10 of the 16 hospitals which took part in the 1987 study. Comparison of these results with those of studies performed in 1984 and 1985 showed a moderate increase in the number of intermediate sensitivity strains of P. aeruginosa and the occasional occurrence, of the epidemic type, in some hospitals of Klebsiella spp. producing very broad spectrum beta-lactamases which were rare in 1985.

Novel plasmid-mediated beta-lactamase in clinical isolates of Klebsiella pneumoniae more resistant to ceftazidime than to other broad-spectrum cephalosporins.

Multiresistant Klebsiella pneumoniae strains isolated from three patients in the same intensive care unit were more resistant to ceftazidime than to cefotaxime and aztreonam but remained susceptible to moxalactam and imipenem. Resistance to beta-lactams, kanamycin, streptomycin, sulfonamides, and tetracyclines was transferable to Escherichia coli by conjugation and was lost en bloc after treatment with ethidium bromide. Agarose gel electrophoresis of wild types and transconjugants indicated that these resistances were mediated by a 150-kilobase plasmid, pCFF14. The strains constitutively produced a beta-lactamase with isoelectric point close to 5.6 and which had a higher Vmax for ceftazidime and cephalothin than for cefotaxime. The substrate profile and isoelectric point of this enzyme thus differ from those of other known plasmid-mediated beta-lactamases, including the broad-spectrum enzyme CTX-1. Hybridization studies support the derivation of the novel enzyme from a TEM-type beta-lactamase.