Serotyping of 80 strains from the WHO multicentre international typing study of Listeria monocytogenes

Serotyping was carried out on 80 coded strains, distribute to all laboratories taking part in the WHO L. monocytogenes multicenter subtyping study. All six laboratories used the method recommended by their coordinator. All 80 strains were typeable. There was complete agreement between the six laboratories on 49 (61.3%) strains (21 serovar 1/2a and 28 serovar 4b strains) which in turn were identical to the expected serovars, known only after decoding. The intralaboratory reproducibility carried out on 11 duplicate strains, ranged from 82 to 100%, with a medium value of 91%. Reproducibility of serotyping L. monocytogenes strains according to serovar varied from 33.3 to 100% for serotypes 3b and 1/2a, respectively, with serovar 4b (x) being incorrectly identified in all six laboratories. Serotyping of L. monocytogenes is easy and simple and is a useful prerequisite for other finer and more discriminatory typing methods. Problems may however, be encountered mainly with the flagellar antigenic factors. There is a need, therefore, for preparing antisera of good quality from which efficient antigenic factors can be obtained.

Resistance to cefotaxime and seven other beta-lactams in members of the family Enterobacteriaceae: a 3-year survey in France

During the second quarter each of 1988, 1989, and 1990, a French collaborative study group, including 12 university hospital laboratories, surveyed the resistance to beta-lactams of clinical isolates from hospitalized patients: consecutively, 10,641, 10,692, and 9,382 isolates were tested. The distribution of bacterial species over time was similar in each laboratory. The susceptibilities of microorganisms to amoxicillin, ticarcillin, cephalothin, cefoxitin, cefotaxime (CTX), ceftazidime (CAZ), aztreonam (ATM), and imipenem (IPM) were measured by the disk diffusion method in accordance with the recommendations of the Antibiogram Committee of the French Society for Microbiology. Five reference strains were included for quality control. Extended-spectrum beta-lactamases were detected by the synergistic effect of the combination of clavulanic acid-amoxicillin with CTX, CAZ, and ATM in the double-diffusion test. A synergistic effect with CTX, CAZ, and ATM was detected for 1.5% of all strains, mainly those of Klebsiella pneumoniae (13.3%). For this species, the synergy test enabled the detection of roughly 50% of the resistant strains misclassified as susceptible on the basis of interpretative standards. Extended-spectrum beta-lactamases disseminated in 1990 in most enterobacterial species but at a low frequency. Important variations in the percentages of resistant strains were observed in terms of bacterial species, hospitals, and wards. However, when the total number of strains was considered, the percentages of resistance to newer beta-lactams remained low.

[In vitro antibacterial activity of a new fluoroquinolone, temafloxacin, against hospital isolates. Results of a multicenter study]

Minimal inhibitory concentrations (MICs) of temafloxacin (TMF) was determined by agar dilution for 2,510 bacterial strains isolated in 1989 in 9 university hospitals. Activity of TMF against nalidixic acid (NAL) susceptible (S) Enterobacteriaceae was close to that of other fluoroquinolones (FQ) (mode MIC: 0.06 micrograms/l); like for other FQ, this activity was reduced against NAL intermediate (mode 1) and resistant (R) (mode 4) Enterobacteriaceae. MICs of TMF against P. aeruginosa were between 0.12 and 128 (mode 0.5-1). TMF had also a good activity against NAL S A. baumannii (mode MIC: 0.06-0.12) but this activity is reduced against NAL R Acinetobacter (mode MIC: 16). TMF was highly active against Haemophilus mode MIC: less than or equal to 0.008), Gonococci (mode MIC: 0.008-0.032), Meningococci (mode MIC: 0.08) and B. catarrhalis (mode MIC: 0.016). TMF showed better activity to other fluoroquinolones against methicillin susceptible Staphylococci (mode MIC: 0.06); the resistant strains (mode MIC: 8) are usually methicillin resistant. Comparatively to the currently available FQ, TMF is so more effective against Enterococci (mode MIC: 1), Streptococci (mode MIC: 0.5-1) and Pneumococci (mode MIC: 0.5). Finally, for the anaerobic bacteria, TMF is more active against C. perfringens (mode MIC: 0.5) than against B. fragilis (mode MIC: 2).

Latest news on listeriosis

Emphasis is given essentially to the presentation of recent data in terms of our total knowledge of Listeria and human and animal listeriosis. This disease of extremely varied origin can be studied in terms of two groups of subjects: females in gestation and all other categories of individuals. There was initially only a single species of Listeria, but at least five are known today, only two of which are pathogenic. Their pathogenic power is related essentially to the presence of listerolysin O, although this is not the only factor involved. Identification of Listeria is easy and can be completed with that of its serovar and lysovar. Epidemiological studies have shown that the great majority of listeriosis are anademic. The contamination of receptive subjects is due to certain forms of food. In the absence of efficient vaccination, disease prevention must be obtained by eliminating Listeria from food.

Detection of respiratory syncytial virus antigen after seventy-two hours of culture

Between September, 1987, and April, 1989, three techniques for the detection of respiratory syncytial virus (RSV) were compared: indirect immunofluorescence (IF) on the sample, indirect immunofluorescence after 72 h of MRC-5 cell culture (IF 72h), and detection of the cytopathic effect (CPE) by MRC-5 and HEp-2 cell culture. A study of 383 nasal aspirates from young children admitted to the Centre Hospitalier de Nantes (CHR) showing miscellaneous respiratory symptoms produced the following results: 143 samples (37%) were RSV positive by IF, 119 (31%) were positive by IF 72h, and 117 (31%) showed RSV-induced CPE. In comparison with tissue culture isolation (TC), the sensitivities of IF and IF 72h were 89% and 80% and their specificities 85% and 91%, respectively. During the winter of 1988-1989, of the 110 RSV-positive nasal aspirates (104 by IF, 89 by IF 72h, 83 by CPE detection), 109 were identified by IF and/or IF 72h. IF 72h affords rapid detection of RSV.

Transferable plasmid-mediated antibiotic resistance in Listeria monocytogenes

A strain of Listeria monocytogenes, isolated from a patient with meningoencephalitis, was resistant to chloramphenicol, erythromycin, streptomycin, and tetracycline. The genes conferring resistance to these antibiotics were carried by a 37-kb plasmid, pIP811, that was self-transferable to other L monocytogenes cells, to enterococci-streptococci, and to Staphylococcus aureus. The efficacy of transfer and the stability of pIP811 were higher in enterococci-streptococci than in the other gram-positive bacteria. As indicated by nucleic acid hybridisation, the genes in pIP811 conferring resistance to chloramphenicol, erythromycin, and streptomycin were closely related to plasmid-borne determinants that are common in enterococci-streptococci. Plasmid pIP811 shared extensive sequence homology with pAM beta 1, the prototype broad host range resistance plasmid in these two groups of gram-positive cocci. These results suggest that emergence of multiple antibiotic resistance in Listeria spp is due to acquisition of a replicon originating in enterococci-streptococci. The dissemination of resistance to other strains of L monocytogenes is likely.

Isolation of Listeria from French meat products

One hundred and ten Listeria strains were recovered from 378 meat samples: L. monocytogenes (68 strains), L. innocua (45) and L. welshimeri (7). L. monocytogenes isolates mainly belonged to serogroup 1/2 (1/2: 23 strains; 1/2b: 1; 1/2c: 43; 4b: 1). These results contrast those observed for 355 human strains isolated during the same period in France where serovar 4b strains were largely predominant (66.5%). 45% of the strains were phage typable. These results underline the widespread occurrence of Listeria in meat products.

Evolution in antibiotic susceptibility of Bacteroides fragilis group strains in France based on periodic surveys

Anaerobic antibiotic susceptibility testing with standardized methods enabled the authors to speculate on the evolution of antibiotic resistance within the Bacteroides fragilis group strains. Cefoxitin resistance was stable (0-5%) until 1985 and gradually increased later. Clindamycin resistance emerged in 1980 with a stable 10% resistance rate until 1986. An increase in clindamycin resistance developed in three institutions in 1987. No change was detected for imipenem and metronidazole, while piperacillin resistance increased since 1986. A comparison of antibiotic resistance rates is discussed for anaerobes in different countries.

[Prophylactic systemic antibiotherapy with only ceftriaxone in neutropenic patients treated in a protected environment]

Prophylactic systemic antibiotherapy with ceftriaxone (CRO) alone was tested in aplastic patients receiving total gut decontamination and treated in protected environment. To enter the study, the patients had to be afebrile when their polymorphonuclear (PMN) count fell under 500/cumm. Seventy eight therapeutic aplasias (after allogeneic or autologous bone marrow transplant conditioning regimens or high dose chemotherapy) form the basis of this report. The median duration of aplasia was 19 D (11-93 D). Forty-three patients received during 51 aplasias one single injection of CRO per day as soon as PMN count was under 500/cumm. In 23 cases (45%) the patients remained afebrile until the end of aplasia. There were 3 Staphylococcus epidermidis bacteremias (6%), 3 bacteriologically documented fevers (6%) and 1 Cryptococcus septicemia. Twenty-nine of these aplasias were part of a randomized study between group A (prophylactic CRO) and group B (non prophylactic CRO: 27 cases). In group A, there were significantly more aplasias without fever (34.5% vs 4%), and less bacteremias (10% vs 48%). Fever appeared later in group A (mean 12.5 D vs 6 D). No death was recorded during the whole study. Thus, in protected environment, prophylactic systemic antibiotherapy could still lessen the risk of bacterial infections. The side effects and the cost of such a procedure appeared to be diminished by a monoantibiotherapy.

Septicaemia due to Actinobacillus actinomycetemcomitans with endocarditis and spinal epidural abscess

A case of tricuspid valve endocarditis with spinal epidural abscess caused by Actinobacillus actinomycetemcomitans is reported in a 74-year-old male with an endocardial pacemaker. Despite antibiotic treatment, removal of the endocardial wire was necessary for recovery.

[Bacterial contamination of the inspiratory circuit of artificial ventilation apparatus: influence of the frequency of circuit renewal and the duration of ventilation]

In a study concerning contamination of artificial ventilators (Drager model UV1), the influence of 2 parameters was assessed: the frequency of changing the circuit (2 and 4 days) and the interval between admission of the patient into the intensive care unit and obtaining the sample. As a function of these variables, 4 groups of 15 patients each were constituted. The levels of contamination noted at 4 sites in the inspiratory phase tubing (cascade humidifier, condensate collector, tubing nearest to the patient and tubing nearest to the humidifier) and in the gas flow showed no significant difference between the groups, regardless of whether the circuit was changed after 2 or 4 days, or whether the patient had been recently admitted to the department or had been there for at least 6 days. Quantitative and qualitative study of bacteria showed that the one(s) contaminating the inspiratory phase tubing were the same as the one(s) colonizing the tracheal secretions of the patient, and that the most contaminated areas were those nearest to the patient (proximal tubing, collector), which confirms the retrograde contamination of the circuit.

[Comparative activity of habekacin and 4 other aminoglycosides against gram-negative bacilli. Evolution of resistance]

The activity of 5 aminoglycosides compounds (habekacin, amikacin, gentamicin, netilmicin and tobramycin) was studied by an agar dilution method, against 235 strains of Enterobacteriaceae and 146 other Gram negative bacilli. 79 to 98% of susceptible strains were observed, according to the aminoglycoside compound. Habekacin and amikacin were the most effective, specially against the more frequently resistant bacteria: Enterobacter, Serratia, Hafnia, Acinetobacter, Pseudomonas aeruginosa. In comparison with a previous study, no evolution was observed in the resistance to aminoglycosides.

[Immunologic response in herpes encephalitis: development of the antibody serum/cerebrospinal fluid ratio in 13 cases]

Serological monitoring was performed in 13 cases of herpetic encephalitis (one infant and 12 adults). Samples taken simultaneously from blood and cerebrospinal fluid (CSF) were tested before and after initiation of antiviral treatment. Antiherpesvirus (anti-HSV) antibodies were assayed by an ELISA method. The state of the blood-brain barrier was controlled by assaying other antiviral antibodies. Immune response was studied during the 3-to-4 weeks of the course of the infection. Anti-HSV IgG levels in CSF increased markedly after 12 days. At the same time, antibody serum/CSF ratios dropped below a value of 20, indicating intrathecal secretion of the antibody. Based on results in monitoring these 13 cases, it may be suggested that 3 samples of serum and CSF are required to confirm the herpetic etiology, including 2 samples taken during the second week of the course of encephalitis.

[Preventive systemic antibiotherapy with ceftriaxone alone in neutropenic patients treated in a protected environment]

Prophylactic systemic antibiotic therapy with ceftriaxone alone was tested in aplastic patients receiving total gut decontamination and treated in a protected environment. Only patients who were afebrile when their polymorphonuclear (PMN) count fell below 500/cumm were admitted to the study. Seventy-eight episodes of therapeutic aplasia (consecutive to allogeneic or autologous bone marrow transplant conditioning regimens or to high dose chemotherapy) form the basis of this report. The median duration of aplasia was 19 days (range 11-93 days). Twenty patients received, during 22 episodes of aplasia, one single injection of ceftriaxone per day as soon as their PMN count was below 500/mm3. In 13 cases (59%) the patients remained afebrile until the end of aplasia, and no bacteriemia was detected. The second part of the study was randomized between group A (prophylactic ceftriaxone: 29 cases) and group B (no prophylactic ceftriaxone: 27 cases). Patients in group A had significantly more episodes of afebrile aplasia (34.5% vs 4%) and less bacteriemias (10% vs 48%) than those in group B. Also fever developed later in group A (mean: 12.5 vs 6 days). No death was recorded throughout the study. Thus, in a protected environment prophylactic systemic antibiotic therapy could still lessen the risk of bacterial infection. Using one single antibiotic seemed to reduce the side-effects and cost of the prophylactic treatment.

[Sensitivity of Pseudomonas aeruginosa to beta-lactam antibiotics. Apropos of 338 strains isolated at the Regional Hospital Center at Nantes in 1984]

The MIC of 338 Pseudomonas aeruginosa strains isolated in 1984, in a French hospital, was determined by an agar dilution method, using seven beta-lactam antibiotics: ticarcillin, azlocillin, piperacillin, cefoperazone, ceftriaxone, cefsulodin and ceftazidime. The MIC50-MIC90 were respectively: 32-64, 8-32, 8-16, 8-16, 16-64, 4-16, 2-4 mg/l. Ticarcillin was the most frequently effective compound (95% of the strains were susceptible), 90% of the strains were susceptible to ceftazidime or piperacillin, 87% to azlocillin and 84% to cefsulodin. Cefoperazone and ceftriaxone were much less effective (43% and 19% of the strains, respectively). The study of the resistance patterns showed a higher percentage (80%) of strains susceptible to all the penicillins than the percentage of strains susceptible to cephalosporins, most of them however were susceptible to both cefsulodin and ceftazidime. It also showed the relatively low frequency of resistant strains by inducible cephalosporinase or decreased permeability. Serovar 0.12 was characterized by its multi-resistance to beta-lactam antibiotics.

Assessment of formulas for calculating critical concentration by the agar diffusion method

The critical concentration of antibiotic was calculated by using the agar diffusion method with disks containing different charges of antibiotic. It is currently possible to use different calculation formulas (based on Fick's law) devised by Cooper and Woodman (the best known) and by Vesterdal. The results obtained with the formulas were compared with the MIC results (obtained by the agar dilution method). A total of 91 strains and two cephalosporins (cefotaxime and ceftriaxone) were studied. The formula of Cooper and Woodman led to critical concentrations that were higher than the MIC, but concentrations obtained with the Vesterdal formula were closer to the MIC. The critical concentration was independent of method parameters (dilution, for example).

[Comparative activity of 9 beta-lactamines, clindamycin and metronidazole on strictly anaerobic bacteria]

The in vitro activities of amoxicillin, amoxicillin-clavulanic acid, piperacillin, cefoxitin, cefotetan, cefotaxime, cefmenoxime, ceftizoxime, latamoxef, clindamycin and metronidazole, were determined by agar dilution method for 196 clinical isolates of anaerobic bacteria. No metronidazole resistant strains could be found, 10% of tested strains were resistant to clindamycin. The majority of these strains was susceptible to amoxicillin-clavulanic acid and piperacillin; less than 10% were resistant to latamoxef, cefoxitin, cefotaxime and ceftizoxime; whereas 15 to 20% were resistant to amoxicillin, cefotetan and cefmenoxime.

[Comparison of fosfomycin-penicillin M and penicillin M-gentamycin. Apropos of 35 severe infections caused by methicillin-sensitive Staphylococcus aureus]

Two combined antibiotic treatments were compared in 35 cases of methicillin-sensitive Staph. aureus infection. Eighteen patients (including 17 with septicaemia) received penicillin M (methicillin or oxacillin) and gentamicin daily for a mean period of 11 days. Clinical and bacteriological cure was obtained in 14 cases; 2 of these 14 patients developed superinfection with gentamicin-resistant enterobacteria, 1 relapsed and 2 had renal impairment. Seventeen patients (including 15 with septicaemia) were given fosfomycin and penicillin M for a mean period of 17 days. Clinical and bacteriological cure was obtained in 16 patients; the patient with clinical and bacteriological failure died. There was no superinfection or relapse; 3 patients had hypokalaemia and 1 had renal damage caused by methicillin. The clinical and bacteriological results, therefore, were in favour of the fosfomycin-methicillin combination, but the only statistically significant difference between the two groups concerned the complications.

Pasteurella multocida bacteremia: report of thirteen cases over twelve years and review of the literature

13 episodes of bacteremia caused by Pasteurella multocida were seen in a general hospital during a 12-year period. All the patients had an underlying disease (77% had cirrhosis) and 2 were receiving chemotherapy for hematologic malignancy. There was a numerical preponderance of male patients (69%). In 5/13 cases a recent animal-derived trauma could be found. In the other cases the source of the infecting organism was thought to be endogenous (from patients' own pharyngeal commensal flora) or secondary to contact with secretions of a pet animal. The clinical presentation of sepsis caused by this organism was nonspecific. Hypotension was seen in 5 cases. Localized sites of infection were certain in 6 and only clinically suspected in 4 other cases. The overall mortality rate was 31%. The administration of ampicillin seems the appropriate therapy for Pasteurella multocida bacteremia.

[In vitro effect of piperacillin, amoxicillin, cefoxitin and metronidazole against obligate anaerobic bacteria]

The minimum inhibitory concentrations (MIC) of piperacillin and three other antibiotics (amoxicillin, cefoxitin, metronidazole) against 165 strains of obligate anaerobes isolated in hospitals in 1985 and 1986 were determined by the Wilkins-Chalgren agar medium dilution method. Among the 67 strains of Bacteroides fragilis, 98.5% were sensitive to piperacillin (MIC less than or equal to 128 mg/l), 100% were sensitive to metronidazole (MIC less than or equal to 4 mg/l), 11.9% were resistant to cefoxitin (MIC greater than 32 mg/l) and 46% were resistant to amoxicillin (MIC greater than 16 mg/l). The MIC50 was about 4 mg/l with piperacillin, 8 mg/l with cefoxitin and 0.5 mg/l with metronidazole. All 32 strains of Clostridium perfringens were sensitive to the 4 antibiotics tested, with an MIC50 of about 0.06 mg/l with piperacillin, 0.125 mg/l with amoxicillin and 0.5 mg/l with cefoxitin and metronidazole. All other strains of Clostridium spp. (33 in all) were sensitive to piperacillin and metronidazole; the MIC's were about 0.06 mg/l with piperacillin, 0.25 mg/l with amoxicillin and metronidazole and 0.5 mg/l with cefoxitin. Seven strains (C. innocuum 5, C. difficile 1, C. ramosum 1) were resistant to cefoxitin. All 33 strains of Peptostreptococcus and Peptococcus were sensitive to the 4 antibiotics tested. Although metronidazole still is the most effective of anti-anaerobes agents, piperacillin has proved to be effective against most anaerobic bacteria, including B. fragilis. It is clearly superior to amoxicillin and relatively superior to cefoxitin, notably against this species.

[Evaluation of the activity of antibiotics against Listeria. Therapeutic perspectives]

The activity of different antibiotics was considered by studying the results reported in literature and during the IXth International Symposium on the Problems of Listeriosis. Listeria susceptibility to antibiotics did not change. Ampicillin was always one of the most effective and used antibiotics against Listeria. The association with an aminoglycoside produced a synergistic effect, which made the bactericidal activity quicker, in vitro as in vivo on animal. More recent molecules like third generation cephalosporins or fluoro-piperazinyl-quinolones had poor activity against Listeria.

[Multicenter study of the activity of pefloxacin on bacteria isolated in a hospital milieu]

Minimal inhibitory concentrations (MICs) of pefloxacin were evaluated by agar dilution for 3422 bacterial strains isolated in nine hospitals. Enterobacteriaceae proved very sensitive to pefloxacin: 62 p. 100 of 1743 strains tested had MIC less than or equal to 0.12 and 90 p. 100 less than or equal to 1 microgram/ml; but the percent of strains with MIC greater than or equal to 2 varied among the different groups of Enterobacteriaceae: 2.7 p. 100 for E. coli to 39 p. 100 for Serratia. 55 p. 100 for Pseudomonas and 81 p. 100 of Acinetobacter were inhibited by 1 micrograms/ml or less (mode MIC 1 and 0.5 micrograms/ml). Haemophilus sp.: 0.03 and 0.06 micrograms/ml and Gonococci were very sensitive to pefloxacin. The spectrum of pefloxacin extended to Gram positive cocci: MIC of Staphylococci were 0.06 to 8 micrograms/ml (mode MIC: 0.5); Enterococci, other Streptococci and Pneumococci were less sensitive: 2 and 4 micrograms/ml for the majority of strains. Concerning anaerobic bacteria, pefloxacin was more active against Clostridium (0.5 to 1 microgram/ml generally), than against Bacteroides (4 to 16 micrograms/ml).

[Comparative sensitivity of 207 strains of strict anaerobic bacteria to piperacillin and 4 other antibiotics]

The MIC of two hundred and seven anaerobic bacterial strains was determined by an agar dilution method for five antibiotics (piperacillin, ampicillin, carbenicillin, cefalotin, metronidazole). 100% of the strains were susceptible to carbenicillin (MIC less than or equal to 128 mg/l), 97% to piperacillin (MIC less than or equal to 16), 86% to metronidazole (MIC less than or equal to 4), 70% to ampicillin (MIC less than or equal to 4) and 68% to cefalotin (MIC less than or equal to 8). Amongst bêta-lactam compounds, piperacillin and ampicillin determined the lowest MIC for Bacteroides fragilis, Fusobacterium, Clostridium and Gram-positive cocci. Amongst Bacteroides fragilis strains, the lowest MIC were obtained with metronidazole.

Reliability of the bronchoscopic protected catheter brush in intubated and ventilated patients

The reliability of a bronchoscopic protected catheter brush (BPCB) in the diagnosis of lower respiratory tract infection was studied in 17 intubated and ventilated patients, including seven patients free from such infection (group 1) and ten patients with suspected infection (group 2). A first sample was obtained in the lower trachea by aspiration through the fiberoptic bronchoscope and a second in a distal bronchus by the BPCB procedure. In group 1, all BPCB cultures were sterile, although lower tracheal cultures yielded two or more bacterial species, showing that uncontaminated specimens can be obtained by the BPCB procedure. In three patients of group 2, BPCB cultures remained sterile as a nonbacterial pulmonary disease was certified by open lung biopsy. In seven patients from group 2, BPCB cultures yielded all of the organisms isolated simultaneously by reference methods (ie, cultures of blood or pleural fluid, serologic tests, and open lung biopsy). In two of these patients, contamination of the BPCB specimens was ascertained by the reference method bacterial results. In this study the BPCB procedure was able to obtain uncontaminated specimens in intubated and ventilated patients and was mainly accurate in identifying the bacterial etiologic agents of lower respiratory tract infections.

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.

[Bacteriostatic and bactericidal effect of cefotaxime combinations on Staphylococcus aureus assessed by FIC and FBC-index determination]

Activity of cefotaxime associated with one of nine other antibiotics (amikacin, dibekacin, gentamicin, netilmicin, sisomicin, tobramycin, erythromycin, clindamycin, and chloramphenicol) was studied by a checkerboard method with determination of FIC and FBC-indices. Four S. aureus strains were used: one homogeneous methicillin-resistant strain (S1), one heterogeneous methicillin-resistant strain (S2), and two susceptible strains (S3 and S4). Strong synergism between cefotaxime and aminoglycosides was found only for S2, with no significant differences between aminoglycosides (index # 0.3). Cefotaxime and chloramphenicol showed synergistic or additive bacteriostatic activities and consistently antagonist bactericidal activities. Bactericidal activities of cefotaxime and erythromycin were likewise antagonistic, whereas cefotaxime and clindamycin occasionally exhibited in vitro synergism.

[Multicenter study of the in vitro effect of imipenem (N-formimidoyl-thienamycin) on hospital bacteria]

Minimal inhibitory concentrations (MICs) of imipenem were evaluated by agar dilution for 2 895 bacterial strains isolated in 9 hospitals. Imipenem proved highly active against Enterobacteriaceae, with an MIC less than or equal to 0.25 for 63% of the 1 556 tested strains, less than or equal to 1 for 89.6% and less than or equal to 4 for 99%. The different groups of Enterobacteriaceae exhibited similar mode MICs (0.12 to 0.25), with the exception of Serratia (0.25-0.5), P. mirabilis (0.5), indole-positive Proteus (2), and Providencia (1). MICs of most cefotaxime-resistant strains were within the susceptibility range. Imipenem also exhibited satisfactory activity against P. aeruginosa (mode MIC 1-2) and Acinetobacter sp. (mode MIC: 0.25-0.5). MICs ranged from 0.03 to 4 (mode MIC: 0.5) for Haemophilus sp. and 0.25 to 1 for Gonococci, regardless of beta-lactamase-production status. MICs for Meningococci were less than or equal to 0,06. Methicillin-susceptible Staphylococci had low MICs, ranging from 0.008 to 0.5 (mode MIC : 0.016); MICs for methicillin-resistant strains varied widely, from 0.016 to 64, and were higher after incubation at 30 degrees C. Streptococci, except for Enterococci, and Pneumococci were highly susceptible (usually 0.008-0.03); MICs for Enterococci varied from 0,12 to 32 (mode MIC: 1-2). Except for four C. difficile strains, all tested anaerobic strains were inhibited by concentrations less than or equal to 1 (mode MICs: 0.06 for C. perfringens and 0.03 for B. fragilis).

[Sensitivity to cefotiam of 494 hospital bacterial strains. Determination of minimal inhibitory concentration and comparison with other beta-lactams]

Susceptibility to cefotiam of 494 bacterial strains was studied by MIC determination using an agar dilution assay. Activity of cefotiam was also compared with that of six other beta-lactams (ampicillin, mezlocillin, ticarcillin, cefalotin, cefotaxime, and moxalactam) using an agar diffusion method. Cefotiam showed a wide antibacterial spectrum including more than 70% of Enterobacteriaceae (except Serratia), beta-lactamase-producing and non-beta-lactamase-producing Haemophilus influenzae, non-enterococcus streptococci, and penicillinase-producing and non-penicillinase-producing staphylococci susceptible to methicillin. Conversely, cefotiam was inactive against Pseudomonas aeruginosa, Acinetobacter anitratum, Streptococcus faecalis, and methicillin-resistant Staphylococcus aureus.

[Comparative effects of netilmicin and 4 other aminoglycosides on 1028 bacterial strains isolated in a hospital milieu]

The activity of netilmicin and four other aminoglycosides was studied by a diffusion method against 1 028 bacterial strains isolated in hospital. Nearly all the strains of Gram-negative bacilli were susceptible to amikacin; with netilmicin, tobramycin, gentamicin and dibekacin the percentages of susceptible strains were smaller, without any statistically significant differences between them. Amikacin and netilmicin were the most effective compounds against staphylococci. Netilmicin seemed to be the most effective compound, in vitro, against streptococci. The MIC of gentamicin and netilmicin of 224 strains showed the superior activity of netilmicin against K. pneumoniae, Proteus, P. aeruginosa and S. aureus.

[Antibiotic sensitivity of 139 strains of Listeria serotyped by the National Reference Center in 1983]

The susceptibility of 139 strains of Listeria towards eight antibiotics--penicillin, ampicillin, cephalotin, gentamicin, chloramphenicol, tetracycline, erythromycin and pefloxacin--was studied. All strains were susceptible to all antibiotics except pefloxacin. The lowest MIC (less than or equal to 0.5 mg/l) were obtained with penicillin, ampicillin, gentamicin and erythromycin. For tetracycline, cephalotin and chloramphenicol, MIC ranged from 0.5 to 16 mg/l. The MIC of pefloxacin varied from 4 to 16 mg/l.

[Antibacterial effects of the combinations of azlocillin with other antibiotics]

Evaluating the synergistic effects of antibiotic associations is by no means an easy task owing to the diversity of the test methods utilized for this purpose. Data extracted from 11 reports published between 1975 and 1982 and concerning associations of azlocillin with various aminoglycosides (gentamicin, sisomycin, netilmicin, amikacin, tobramycin and dibekacin) and with two beta-lactam antibiotics (cloxacillin and cefotaxime) are reviewed in this article. On the whole, a synergistic effect against Staphylococcus aureus, Pseudomonas aeruginosa and Enterobacteriaceae was most frequently observed with the azlocillin-aminoglycoside association. This effect was usually more pronounced with organisms showing low sensitivity to azlocillin and less pronounced with organisms resistant to aminoglycosides. As often pointed out, there is no general rule that would help predict with certainty from the sensitivity of a strain whether or not any given antibiotic association will act synergistically on that strain.

[Pharmacokinetics of azlocillin in the burn patient]

Pharmacokinetic values of azlocillin were determined in burned patients during the exudation and repair periods. A single dose of 80 mg/kg was administered intravenously over 30 min. Pharmacokinetic constants were calculated using an open two-compartment model. During the exudation period the ultimate serum half-lives (t 1/2 beta) were 1.17 to 1.4 h, 1.73 to 1.78 h and 3.3 h respectively with creatinine clearances of 111-131, 60-94 and 14 ml/min/1.73 m2. Renal clearances varied from 30.9 to 128 ml/min/1.73 m2. During the repair period little change was observed in t 1/2 beta, but renal clearance increased from 36.6 to 116 ml/min/1.73 m2 in one patient. It is concluded that azlocillin behaves in burned patients as in patients with impaired renal function.

[Critical study of the serological diagnosis of herpetic encephalitis. Apropos of 4 cases]

Virologic study was performed in four cases of Herpes simplex virus encephalitis. Herpes simplex virus type 1 was recovered from surgical brain biopsy specimens taken in three cases. Anti-HSV antibodies were assayed in simultaneous blood and cerebrospinal fluid samples by ELISA. CSF and serum specific antibody ratios were compared to those of antibodies directed against other viral antigens whenever possible. A significant and early increase in this CSF/serum ratio was demonstrated in two patients. The diagnostic value of this serological method is discussed, as an alternative to viral isolation from brain biopsy specimens.

[In vitro action of moxalactam on hospital bacteria. Results of a multicenter survey]

The high potency of Moxalactam on three major groups of bacteria, i.e. Enterobacteriae, Haemophilus and Bacteroïdes, predicted by previous studies, has been confirmed by the study of hospital strains in this multicenter investigation. Among these groups, the proportion of resistant strains is very low. However, Moxalactam is not superior to older agents on staphylococci, Streptococci and Listeria, and is less active than certain new agents on Pseudomonas. Moxalactam is one of the best "third generation" cephalosporins. It is remarkable by its potency against Bacteroides fragilis and its weak activity on Streptococci and Pneumococci. The unanswered question concerns the future of resistant strains: will they remain exceptional or will they multiply?

[In vitro activity of cefatiolene (RP 42,980) against hospital bacteria. Comparison with cefotaxime and lamoxactam. Results of a multicenter study]

This work reports a multicenter study of antibacterial activity of cefatiolene (RP 42 980), a new third generation cephalosporin, in comparison with cefotaxime and lamoxactam. On the basis of MIC, activity of the three products is similar or Gram negative rods, but cefotaxime is a little more active on Enterobacteriaceae. The activity against Staphylococci requires further studies, indeed the determination of IC 50 of some strains showed a better activity of cefatiolene, but this was not observed by determination of MIC. As cefotaxime and contrary to lamoxactam, cefatiolene is active at low concentrations on other Streptococci than Enterococci, but a little on Bacteroides.

[Contribution of rapid methods to the diagnosis of Haemophilus influenzae infections and the conduct of antibacterial treatment]

In the last decade medical microbiologists could make use of a great number of techniques that allow to shorten length of time of report from the arrival of specimens in laboratory. The direct microscopical examination has been considerably revalued: it is very important. Now it can be completed by use of reagents that allow the presumptive identification of various bacteria. For Hemophilus influenzae the efforts are devoted only to serovar b. In the absence of visible bacteria, the research of the presence of bacterial antigen is now possible. The semiautomatic apparatus allows also to watch over the cultures and to detect the beginning of development more accurately than macroscopically. Finally, for antibiotic sensitivity test, we can also use the automatic apparatus that shortens length of time of report to clinician.

[Bactericidal activity of antibiotics as a function of pharmacokinetic constants. II. Effect of pharmacokinetic parameters (C max and Ke) on the bactericidal activity of gentamicin]

The authors studied the influence of certain pharmacokinetic parameters on the bactericidal activity of gentamicin using an experimental model simulating the variations of antibiotic concentration. These parameters are the maximal concentration (C max) and the elimination constant (Ke). The bactericidal activity of gentamicin was studied on the strain of E. coli ATCC 25922. The result is that an influence of C max on the bactericidal activity is more important than that of Ke from these experiments. Considering only bacteriological parameters, the rapid intravenous injection will be superior to slow perfusion. However, the pharmacological parameters must be considered and modify also these conclusions.

[Bactericidal activity of antibiotics as a function of pharmacokinetic constants. I. Experimental dynamic model simulating variations in the concentrations of antibiotics]

In order to study the bactericidal effect of antibiotics in a system approaching actual therapy, a dynamic model which simulates concentration variations was developed. This was done using a dialysis intermediary. Three aminoglycosides (amikacin, gentamicin, tobramycin) were taken in a system resembling the serum rates of the normal individual. The apparatus is fairly accurate, the variation coefficients being of the order of 10 to 14%. This model enables the simulation of numerous therapeutic situations. It is however limited to only dialysable antibiotics.

[Influence of antibiotic disk charge on concordance curve of cefotaxime ]

The activity of new cephalosporins is considerably higher than that of the first molecules. However antibiotic desk charge used for the agar diffusion method is still 30 micrograms. The disk diffusion - MIC distribution is not linear. The authors observed the influence of disk charge on the aspect of this distribution in order to determine the change permitting the best linearity. One hundred sixty five strains were studied using the agar diffusion and dilution methods. Their MICs were distributed from 0.015 to 128 mg/l. The disk charges studied were 5, 10, 15, 20, 25 and 30 micrograms. The results confirmed the parabolic aspect of concordance curve. This phenomenon was observed at higher disk charges (20, 25 and 30 micrograms). The linearity is better with the curves calculated from 5 and 10 micrograms. The correlation coefficients between these two charges were 0.92. However the inhibition diameters in 5 micrograms were too small to permit a clear differentiation between resistant and intermediate strains. The best discrimination is obtained with 10 micrograms. The zone diameter breakpoints were greater than or equal to 18 mm for susceptible 12 to 17 mm for intermediate, and less than or equal to 11 mm for resistant.

[Expression of staphylococci resistance to oxacillin and cefalotin ]

The comportment to oxacillin (OXA) and cefalotin (CFT) of 32 strains of staphylococci - 18 Staphylococcus aureus and 14 coagulase-negative staphylococci (SCN) - was studied by three different methods, on three types of media, with or without 5 p. cent of NaCl and incubated at two temperatures (30 degree C-37 degree C). S. aureus showed always a cross-resistance to OXA and CFT. Three types were recognized : "susceptible" (S) and "high level resistant" (RO) types, whose comportment did not vary with culture conditions; "heterogenous resistant" type (RH) for which the OXA - resistance expression was better at 30 degree C and on salt medium. SCN did not always present a cross-resistance. In addition to S, RO and RH types, one strain showed a dissociated resistance to OXA and CFT, with a better expression at 30 degree C and on salt medium; one strain, which appeared to be susceptible by discs method, presented a resistant population level higher than that of the susceptible reference strain, whatever the culture conditions were.

[Comparative activity of cefsulodin on Pseudomonas aeruginosa, Acinetobacter and Enterobacteriaceae (author's transl)]

Cefsulodin, a new semi-synthetic cephalosporin, is characterized by its activity against P. aeruginosa. In this study the authors compared this new molecule with other four betalactamines, carbenicillin, ticarcillin, azlocillin and mezlocillin, and two aminoglycosides, amikacin and netilmicin. Two hundred and forty five strains studied were 100 Pseudomonas aeruginosa, 20 Acinetobacter, 42 Proteus, 21 Serratia, 22 Enterobacter, 20 Klebsiella and 20 E. coli. One hundred twenty strains of these showed carbenicillin resistant phenotype. MIC were determined by the agar dilution method. Cefsulodin was only active on Pseudomonas aeruginosa. MICs were at least 16 mg/l in the other species. On carbenicillin susceptible P. aeruginosa strains, the average MIC of cefsulodin, amikacin and netilmicin was 1 mg/l, and MICs of azlocillin, mezlocillin, ticarcillin and carbenicillin were 4-8 mg/l, 8 mg/l, 16 mg/l and 32 mg/l, respectively. On carbenicillin resistant P. aeruginosa, ticarcillin and mezlocillin were not effective and MICs of azlocillin and cefsulodin were 16 mg/l and 4-8 mg/l, respectively. However, MICs were between 64 and 128 mg/l in 20 p. cent of carbenicillin resistant strains.

[Comparison of light-scattering index 50% (LSI50) and inhibitory concentration 50% (CI50) (author's transl)]

The "Autobac" apparatus permitted the rapid determination of the light-scattering index 50% (LSI50) and inhibitory concentration 50% (CI50) of eight antibiotics -- kanamycin, amikacin, lividomycin, gentamicin, tobramycin, sisomicin, netilmicin and colistin -- for the strain of Escherichia coli ATCC-25922. The results were compared with those of the reference method using an agar dilution method. The percentage of inhibition (% I) was obtained from LSI by applying the formula % I = 10(-(GIXLSI)). The growth index (GI) has an influence on the values of the rapid method. The best results were observed in the GI ranges of 1.2 to 1.7. For all the antibiotics except tobramycin and colistin, the CI50 values of the two methods were very similar. The values of LSI50 were not assimiliated to those of CI50. These three parameters had a small variability. The averages of standard deviation were 0.23 log2 for the CI50 of the reference method, 0.24 log2 for the CI50 of the rapid method and 0.32 log2 for the LSI50. The "Autobac" enables the determination of CI50 by a simpler and faster technique.