In vitro activity of oxolinic acid and nalidixic acid against common urinary pathogens: a comparative study.

A study was carried out to compare the sensitivity of 500 bacterial strains, isolated from patients with urinary tract infections, to oxolinic acid and nalidixic acid. The results showed that whilst both antibacterial agents were similar in their bacterial spectrum they were not identical in terms of cross-sensitivity or resistance. Where there was a difference in sensitivity, this was always in flavour of oxolinic acid and was particularly evident in the case of Staphylococcus, Pseudomonas, Serratia, Klebsiella, Proteus (especially P. rettgeri), and to a lesser extent Citrobacter.

Evaluation of closed sterile prefilled humidification.

A closed sterile prefilled humidifier ('Aquapak 310') and a multiple-use humidifier ('Nebal 2') were evaluated in hospital departments to determine their susceptibility to bacterial contamination and cost. No bacterial contamination was found in the 389 samples of 'Aquapak 310' water. However, 54/164 (32.9%) samples of 'Nebal 2' water were found to be contaminated. Pseudomonas aeruginosa was the bacterium most often isolated. The cost analysis was highly influenced by the average use time. In the haemodialysis and respiratory medicine departments the average use times for the 'Aquapak 310' +/- SD were 61.6 +/- 36.2 days and 4.1 +/- 1.7 days, respectively. Using the 'Aquapak 310' system, there was a 51% financial saving in the haemodialysis department but a 2% loss in the respiratory medicine department. In these two departments we found a similar cost saving as far as staff time was concerned (88% vs. 89%). The major difference came from the cost of consumables: 26% saving in the haemodialysis department vs. 70% loss in the respiratory medicine department. Use of the prefilled sterile humidifiers represents a three-fold benefit, a lower infection risk for the patient, an important financial saving in the haemodialysis department and a decreased staff work load.

Identification and susceptibility testing for obligate anaerobic bacteria using a semi-automated API ATB plus system.

We evaluated the reliability of the API systems, Rapid ID 32 A and ATB ANA, for the identification and susceptibility testing of obligate anaerobic bacteria in a clinical laboratory that does not possess either an anaerobic chamber or a chromatograph. Tested were 105 clinical isolates. Identifications were compared with those obtained according to the criteria of the Virginia Polytechnic Institute Manual using the API 20 A system with incubation in an anaerobic chamber and gas chromatography. Identifications were concordant in 86.3% of cases. The Rapid ID 32 A system was inaccurate in distinguishing Bacteroides of the fragilis group. Susceptibility to 10 antibiotics of the ATB ANA system was compared to that obtained by MIC determination on Wilkins Chalgren agar. Overall, concordance was 78.2%. Disagreements were mostly minor (16.4%): resistant strains classified as intermediate or intermediate classified as susceptible. When the ATB ANA strip cannot be inoculated in an anaerobic chamber, it is possible that a denser inoculum would decrease the percentage of minor disagreements.

Kinetics of bactericidal activity of antibiotics measured by luciferin-luciferase assay.

ATP production, measured by the luciferin-luciferase assay, is an indicator of bacterial metabolic activity. This enzymatic assay yields rapid results (less than 5 minutes), permitting multiple measurements and establishment of ATP growth curves in order to study the kinetics of antibiotics in bacterial populations. The measurement of free or extracellular ATP, total ATP (extra and intracellular) and the ratio of free to total ATP are additional means of studying the bacteriostatic or bactericidal activity of antibiotics. An increase in free ATP is an indicator of extracellular movement due to alteration of the cell wall. The ratio free ATP/total ATP x 100 greater than or equal to 50%, indicates bacteriallysis. These assays were used to study the effects of 14 antibiotics on two reference strains of Escherichia coli ATCC 25922 and Staphylococcus aureus 25923.

Evaluation of two media for antibiotic susceptibility testing of anaerobic bacteria using the receiver operating characteristic procedure.

Wilkins-Chalgren agar and Meat-Yeast agar were evaluated as media for antibiotic susceptibility testing using 112 anaerobic bacterial strains. The results obtained with the two media using the diffusion method were compared with those obtained by the dilution method as reference method. The results were analyzed by the receiver operating characteristic (ROC) procedure allowing a graphic representation of sensitivity and specificity of the technique for each cut-off value. The area under the ROC curves was calculated to compare the accuracy of the two methods. Six antibiotics were tested including amoxicillin, cefoxitin, piperacillin, doxycycline and clindamycin. For amoxicillin and clindamycin, the two methods showed a high and identical discriminative power for distinguishing susceptible bacteria from the others. Diffusion in Wilkins-Chalgren agar appeared better than diffusion in Meat-Yeast agar for separating resistant bacteria from bacteria of intermediate susceptibility (amoxicillin p less than 0.005; clindamycin p less than 0.04). For other drugs, diffusion in Wilkins-Chalgren agar always had a discriminative power higher than that obtained with diffusion in Meat-Yeast agar for separating susceptible bacteria from the others (cefoxitin p less than 0.0005; piperacillin p less than 0.02; doxycycline p less than 0.05). The Wilkins-Chalgren agar medium thus appeared superior to the Meat-Yeast agar medium using the ROC evaluation method, which would deserve wider utilization in the field of microbiology.

Use of the Autobac system for detection of methicillin-resistant Staphylococcus aureus.

Using 490 strains of Staphylococcus aureus divided into methicillin-susceptible, -resistant, and -heteroresistant varieties, we compared the results obtained by the agar disk method with those obtained with the automated Autobac system. Susceptible strains exhibited a perfect correlation, whereas there were numerous discrepancies with resistant and still more with heteroresistant varieties. When incubation was increased to 18 h at 37 degrees C (Autobac incubation temperature), 35 degrees C, or 30 degrees C, these differences disappeared, but other problems may arise when incubation is prolonged, especially with erythromycin. We thus recommend carrying out two readings, a normal one after 3 h of incubation and a special reading after 18 h, solely for the detection of heteroresistance to methicillin.

Fatal Selenomonas sputigena septicemia probably originating from lung abscess.

A case of fatal septicemia with Selenomonas sputigena in an immunocompromised patient is reported. The patient had a lung abscess from which the septicemia is believed to have originated. In contrast to the only other case reported in the literature, the isolate from our patient was characterized by very slow and difficult growth.

[Problem of the in vitro sensitivity to cefamandole of methicillin-resistant Staphylococcus aureus]. / Le problème de la sensibilité in vitro au céfamandole de Staphylococcus aureus résistants à la méthicilline.

In work involving 127 strains of methicillin resistant Staphylococcus aureus, belonging to two resistance categories, homogeneous or RO and heterogeneous or RH and using five cephalosporins, cefalotin, cefazolin, cefamandole, cefotaxime and latamoxef, the authors compared the results of their in vitro sensitivity measurements with two methods: agar disk diffusion and growth inhibition in liquid medium (Autobac). They also compared the MIC values with a significant fraction (19 strains). In order to detect heterogeneous resistance experiments were carried out in duplicate, with one series grown in hypertonic medium and incubated for 48 heures at 37 degrees C, or grown on normal medium with lower incubation at 30 degrees C. In both defined techniques and in vitro, it was observed that the 127 methicillin resistant Staphylococcus aureus strains except one were sensitive to cefamandole and that 26 were also sensitive to cefalotin. Considerable caution is necessary in the in vivo transposition of these findings. May be present media are not able to allow growth of resistant strains to cefamandole.

[Rapid detection of tolerance of streptococci and enterococci to beta-lactam antibiotics by measurement of bacterial TPA]. / Détection rapide de la tolérance des streptocoques et des entérocoques aux bêtalactamines par mesure de l'ATP bactérien.

The authors developed a rapid method for determination of tolerance of streptococci and enterococci to ampicillin by measuring the bacterial TPA. Of thirty three strains from blood cultures, 11 were tolerant with a MBC/MIC ratio > 32. For these strains, the free TPA/total TPA ratio measuring the bacterial lysis after a 2hrs incubation with 2 MIC of ampicillin, had an average of 38% (SD = 21) versus 88.6% (SD = 17.9) for the non-tolerant strains. There is a good correlation between the values of MBC/MIC ratios and the free TPA/total TPA ratios. The authors concluded that TPA assessment after 2hrs incubation with antibiotic can predict the antibiotic tolerance of streptococci or enterococci.

[Comparison of minimum inhibitory concentrations of group M penicillins against Staphylococcus aureus. Practical impact on diagnosis and treatment]. / Comparaison des concentrations minimales inhibitrices des pénicillines du groupe M vis-à-vis des Staphylococcus aureus. Incidences pratiques sur le diagnostic et la thérapeutique.

The MICs were determined in usual conditions and in special conditions for the detection of heterogeneous methicillin resistance. The study involved 40 strains of Staphylococcus aureus of the 3 categories of homogeneous resistant, heterogeneous resistant and sensitive strains. The MICs of the 4 main compounds of the group M penicillins, methicillin, oxacillin, cloxacillin and dicloxacillin, were lower in the presence of a higher number of chlorine atoms on the molecule. The heterogeneous strains were even sensitive to dicloxacillin. The MIC for a notable fraction of resistant strains were lower than the critical value, i.e. these strains entered the category of dicloxacillin sensitive even in reading conditions theoretically leading to the detection of heterogeneous resistance. These in vitro observations are of value in the presence of methicillin sensitive strains, since antibiotics containing one or two chlorine atoms will probably be more therapeutically effective. But the bacteriologist should pay more careful attention to the detection of methicillin resistant and heteroresistant strains, since the resistance in vivo is extended to other penicillinase-resistant penicillins or penicillins M.

[In vitro bactericidal rate of amikacin at concentrations realizable in vivo]. / Vitesse de bactéricidie, in vitro, de l'amikacine aux concentrations realisables in vivo.

The bactericidal rate of amikacin in vitro was established by varying bacterial cell density (10(5) and 10(6) CFU/ml) and physiological state (lag phase and onset of exponential growth) at the moment the antibiotic was introduced. This was done with nine strains belonging to five different species. Antibiotic concentrations were those obtained in vivo at the valley (4 micrograms/ml) and the peak (20 micrograms/ml) with a dosage of 5 mg/kg. The concentration of 40 micrograms/ml is the peak value in the context of hypothesis of a short-term treatment with reinforced dosage (10 mg/kg). The bactericidal effect of amikacin, generally rapid, increased with increasing drug concentration. A bactericidal effect of 99.9% or even 99.99% was obtained in one hour or less at the concentration of 40 micrograms/ml. Above all, this concentration prevented regrowth or rebound, observed at lower concentrations. This results from a rapid but above all powerful bactericidal effect, practically total and constitutes a bacteriological argument in favor of an increase in dosage combined with a reduction in the length of treatment.

[Hypocomplementaemic leucocytoclasic vasculitis. (Mac Duffie's syndrome). One case with bacterial lymphadenitis (author's transl)]. / Vascularite leucocytoclasique hypocomplémentémique (syndrome de Mac Duffie): Un cas avec lymphaénite bactérienne.

Mac Duffie's syndrome includes a hypocomplementaemic allergic vasculitis with essentially cutaneous and articular manifestations. Its pathogenesis, still incompletely elucidated, involves the precipitation of immune complexes in the walls of the all vessels. The problem remains as to whether the alteration in the complement system is merely a reflection of this formation of immune complexes, or if it is primary, favourising the chronic infections which produce such complexes. The significance of the presence of low molecular weight precipitins reacting with C1g in the serum of a number of patients remains uncertain. The case reported, with its new clinical features, does not provide an answer to these questions but emphasises the possible role of chronic infections in the origin of this syndrome.