[Staphylococcus aureus: new detection of intrinsic resistance using the diffusion method]. / Staphylococcus aureus: nouvelle détection de la résistance intrinsèque par la méthode de diffusion.

Because of an heterogeneously-expressed resistance among methicillin-resistant Staphylococcus aureus strains the conditions for antibiogram determination had rapidly to be modified so as to improve their detection. The newly recommended conditions (incubation at +30 degrees C or on hypersalted agar medium) remain widely used at the moment, although they appear to be more and more often badly adapted, particularly because of the recently-observed renewed outbreak of wild strains with a weak in vitro phenotypic expression. It is the reason why we searched for a new and more reliable phenotypic method although still accessible for any laboratory. Sixty-five strains of Staphylococcus aureus entered the study. The absence or presence of mecA gene was previously investigated by gene amplification. These strains were of various origins and had often caused difficulties for the detection of intrinsic resistance to methicillin on the antibiogram. Our results confirm the failures of the classical methods (false negative results at +30 degrees C, false negative or positive results on hypersalted agar medium incubated at +37 degrees C). They also allow to propose a new method which relies on the determination of the susceptibility to cefoxitin using the usual conditions for antibiogram determination. In our series of strains, this new method proved to widely improve both the sensitivity and the susceptibility for the detection of methicillin-resistance by diffusion on the antibiogram.

Lung reperfusion injury after chronic or acute unilateral pulmonary artery occlusion.

Because the lungs receive their blood supply from both the pulmonary and bronchial systems, chronic pulmonary artery obstruction does not necessarily result in severe ischemia. Ischemia-reperfusion (IR) lung injury may therefore be attenuated after long-term pulmonary artery obstruction. To test this hypothesis, isolated left lungs of pigs were reperfused two days (acute IR group) or 5 wk (chronic IR group) after left pulmonary artery ligation and compared to those of sham-operated animals. The severity of IR-lung injury after 60 min ex vivo reperfusion of the left lung was assessed based on lung histology and measurements of filtration coefficient (Kfc), pulmonary arterial resistance (Rpa), and lung myeloperoxidase (MPO) activity. Marked bronchial circulation hypertrophy was seen in the chronic IR group. Hemorrhagic alveolar edema was found in all acute IR lungs but not in sham or chronic IR lungs. Compared with the sham-operated controls, Kfc and Rpa increased two-fold and threefold, and MPO 1.5-fold and twofold in the chronic and acute IR groups, respectively. In conclusion, IR-induced lung injury was markedly reduced when it occurred 5 wk after pulmonary artery ligation, probably because the systemic blood supply to the lung had time to develop, limiting ischemia.

Ex vivo lung model of pig-to-human hyperacute xenograft rejection.

OBJECTIVE: Our objective was to study lung hyperacute rejection in the pig-to-human xenotransplantation combination. METHODS: Pig lungs were harvested and continuously ventilated and perfused ex vivo, using a neonatal oxygenating system, with either xenogeneic unmodified human blood (n = 6) or autogeneic pig blood (n = 6). RESULTS: Autoperfused lungs displayed normal hemodynamics, oxygen extraction (arteriovenous oxygen difference), and histologic characteristics throughout the 3-hour study period. By contrast, xenoperfused lungs displayed, within 30 minutes, severe pulmonary hypertension and abolishment of arteriovenous oxygen difference culminating in massive pulmonary edema, hemorrhage, and lung failure after 115 +/- 44.2 minutes of reperfusion. Within 30 minutes, the human blood showed a significant drop of anti-alpha Gal immunoglobulin M and G xenoreactive antibodies (enzyme-linked immunosorbent assay) and complement activity, consumption of clotting factors, and hemolysis; total circulating human immunoglobulins remained substantially normal. Histologically, lungs perfused with human blood were congestive and showed alveolar edema and hemorrhage and multiple fibrin and platelet thrombi obstructing the small pulmonary vessels (arterioles, capillaries, and venules) but not large (segmental or lobar) pulmonary vessels. On immunohistologic examination, deposits of human immunoglobulin M and complement (C1q and C3) proteins were observed on the alveolar capillaries. CONCLUSIONS: This pig-to-human xenograft model suggests that the pig lung perfused with human blood has an early and violent hyperacute rejection that results in irreversible pulmonary dysfunction and failure within approximately 150 minutes of reperfusion.

Inhaled nitric oxide attenuates reperfusion injury in non-heartbeating-donor lung transplantation. Paris-Sud University Lung Transplantation Group.

BACKGROUND: Non-heartbeating-donor (NHBD) lung transplantation could help reduce the current organ shortage. Polymorphonuclear neutrophil (PMN) activation plays a pivotal role in ischemia-reperfusion injury (I-R), and can be inhibited by nitric oxide (NO). We hypothesized that inhaled NO might be beneficial in NHBD lung transplantation. METHODS: The effect of inhaled NO on PMNs was studied by measuring in vivo PMN lung sequestration (myeloperoxidase activity) and adhesion of recipient circulating PMNs to cultured pulmonary artery endothelial cells (PAECs) in vitro. Pigs were randomly assigned to an NO or a control group (n=9 each). In the NO group, cadavers and recipients were ventilated with oxygen and 30 parts per million of NO. After 3 hr of postmortem in situ warm ischemia and 2 hr of cold ischemia, left allotransplantation was performed. The right pulmonary artery was ligated, and hemodynamic and gas exchange data were recorded hourly for 9 hr. Recipient PMN adherence to tumor necrosis factor-alpha- and calcium ionophore-stimulated PAECs was measured before and after reperfusion, and lung PMN sequestration was determined after death. RESULTS: NO-treated animals exhibited lowered pulmonary vascular resistance (P<0.01), as well as improved oxygenation (P<0.01) and survival (P<0.05). Adhesion of PMNs to PAECs was inhibited in the NO group before (P<0.001) and after reperfusion (P<0.0001). Lung PMN sequestration was reduced by NO (P<0.05). CONCLUSIONS: Inhaled NO attenuates I-R injury after NHBD lung transplantation. This is likely due to the prevention of I-R-induced pulmonary vasoconstriction and to the direct effect on peripheral blood PMN adhesion to endothelium, which results in reduced sequestration and tissue injury.

[Routine detection of beta-lactamases TEM resistant to inhibitors (IRT) and oxacillinases (OXA) in Escherichia coli]. / Détection en routine des bêta-lactamases TEM résistantes aux inhibiteurs (IRT) et des oxacillinases (OXA) chez Escherichia coli.

Comparative study of twenty two strains of Escherichia coli producing a well-characterized penicillinase of the OXA type (oxacillinase) or of the IRT type (TEM resistant to inhibitors) evidenced different criteria leading to the distinction of two groups of strains, according to the type of the harboured enzyme. Applied to eleven clinical strains, these criteria were always concordant with the determination of the isoelectric point, of hybridization and of oligotyping using probes for the classification into OXA or IRT type. We therefore propose the measurement of three inhibition diameters on antibiogram (cefepime, mecillinam and ceftazidime) for the routine distinction of the two enzymes. The interest of the easy characterization of these enzymes is reinforced by our findings that, as for all OXA strains, the inoculum effect which is displayed by some third-generation cephalosporins is very important and should be taken into account in the treatment of severe infections.

Lasting beneficial effect of short-term inhaled nitric oxide on graft function after lung transplantation. Paris-Sud University Lung Transplantation Group.

The combination of ischemia and reperfusion after lung transplantation is characterized by endothelial damage, neutrophil sequestration, and decreased release of endothelial nitric oxide. Because nitric oxide has been shown to selectively dilate the pulmonary vasculature, abrogate neutrophil adherence, and restore endothelial dysfunction, we hypothesized that inhaled nitric oxide given for 4 hours during initial reperfusion might attenuate reperfusion injury in a porcine model of left single-lung transplantation. We tested hemodynamic and gas exchange data, lung neutrophil sequestration, and pulmonary artery endothelial dysfunction after 4 and 24 hours of reperfusion in 12 pigs randomly assigned to nitric oxide and control groups. Harvested lungs were preserved in normal saline solution for 24 hours at 4 degrees C. During transplantation, inflatable cuffs were placed around each pulmonary artery to allow separate evaluation of each lung by occluding flow. Compared with the transplanted lungs in the control group, transplanted lungs in pigs treated with inhaled nitric oxide significantly improved gas exchange, pulmonary vascular resistance, shunt fraction, and oxygen delivery at 4 and 24 hours after reperfusion. Neutrophil sequestration, as measured by the neutrophil-specific enzyme myeloperoxidase and the alveolar leukocyte count per light microscopic field, was significantly lower at 24 hours after reperfusion in the transplanted lungs of the nitric oxide group. The nitric oxide-treated native right lungs exhibited significantly reduced increase in neutrophil accumulation compared with that in control native right lungs. After 24 hours of reperfusion, endothelium-dependent relaxation to acetylcholine was similarly and severely altered in both groups. We conclude that short-term inhaled nitric oxide given during the first 4 hours of reperfusion after lung transplantation significantly attenuates reperfusion injury, improving graft function as long as 24 hours after operation. This effect is probably mediated by a decrease in neutrophil sequestration. A protective effect on the contralateral lung was also observed. Inhaled nitric oxide may be a suitable agent when an acute reperfusion phenomenon is anticipated.

Prevention of ischemia-reperfusion lung injury by inhaled nitric oxide in neonatal piglets.

Lung ischemia-reperfusion results in a decrease in the release of nitric oxide (NO) by the pulmonary endothelium. NO may have lung-protective effects by decreasing neutrophil accumulation in the lung. We tested whether NO inhalation would attenuate reperfusion-induced endothelial dysfunction and increases in microvascular permeability and total pulmonary vascular resistance (RT) by preventing neutrophil lung accumulation. After baseline determinations of RT, coefficient of filtration (Kfc), and circulating neutrophil counts, isolated neonatal piglet lungs were subjected to a 1-h period of ischemia followed by a 1-h period of blood reperfusion and reventilation with or without addition of NO (10 ppm). NO prevented reperfusion-induced increases in RT and Kfc, as well as the decrease in circulating neutrophils. After reperfusion, increases in Kfc were correlated with decreases in circulating neutrophils. NO prevented reperfusion-induced decrease in endothelium-dependent relaxation in precontracted pulmonary arterial rings. This demonstrates that inhaled NO prevents microvascular injury, endothelial dysfunction, and pulmonary neutrophil accumulation in a neonatal piglet model of lung ischemia-reperfusion.

Amelioration of reperfusion injury by pentoxifylline after lung transplantation. The Université Paris-Sud Lung Transplant Group.

BACKGROUND: Pentoxifylline attenuates neutrophil-mediated lung injury in several models of acute lung inflammation. METHODS: Because pulmonary neutrophil sequestration is the main determinant of lung reperfusion injury, we sought to determine whether pentoxifylline prevented reperfusion injury in isolated perfused rat lung (4-hour cold ischemia, 1-hour reperfusion; pentoxifylline intravenously 40 mg) and in pigs after left lung allotransplantation (24-hour cold ischemia, 4-hour reperfusion; pentoxifylline 1.5 mg/kg/hr intravenously). In the pigs, inflatable cuffs placed around each pulmonary artery enabled us to evaluate each lung separately. RESULTS: In rat lungs, the coefficient of lung permeability increased by 75% +/- 10% in controls and by 3% +/- 2% (p < 0.01) in pentoxifylline-treated lungs. In the pigs, with blood flow to the transplanted lung alone and ventilation with an inspired oxygen fraction of 1, the arterial oxygen tension was greater in the pentoxifylline group than in the control group (423 +/- 49 versus 265 +/- 43 mm Hg, p < 0.05), whereas the total pulmonary vascular resistance was lower (15 +/- 1 versus 30 +/- 9 mm Hg/L/min, p < 0.02). After reperfusion, the decrease in circulating leukocyte count fell by 35% +/- 3% in the control group and remained unchanged in the pentoxifylline group, and the leukocytes count per microscopic field in the transplanted lung was lower in the pentoxifylline group than in the control group (15 +/- 2 versus 140 +/- 50, p < 0.02). CONCLUSIONS: These data suggest that pentoxifylline prevented reperfusion injury by decreasing neutrophil lung sequestration.

Reduction of ischemia-reperfusion injury by pentoxifylline in the isolated rat lung. Paris-Sud University Lung Transplantation Group.

Inhibition of pulmonary neutrophil sequestration attenuates ischemia-reperfusion (IR) lung injury. Pentoxifylline (PTX) reduced pulmonary sequestration of neutrophils and neutrophil-dependent lung injury in several experimental settings but has never been tested in IR models. We hypothesized that PTX may have a beneficial effect on IR lung injury as measured by the coefficient of filtration (Kfc) and may reduce IR-associated sequestration of neutrophils as assessed by lung myeloperoxidase (MPO) activity and by blood neutrophil count decrease during reperfusion. Three groups of isolated blood perfused rat lungs were studied: a time control group (n = 6) was perfused for 3 h, and two groups (n = 10) subjected to 1 h ischemia were treated with PTX or saline before a 2 h reperfusion. The increase in Kfc induced by IR was reduced fivefold by PTX compared with saline (+27 +/- 8% versus +112 +/- 12%, respectively; p < 0.001), and was similar to time controls (+9 +/- 9%). After IR, MPO and blood neutrophil count decrease were lower with PTX than with saline. Changes in Kfc were correlated to the percentage decrease in blood neutrophils during reperfusion. We conclude that PTX reduced rat lung IR microvascular injury. This effect may be mainly caused by decrease in lung sequestration of neutrophils during reperfusion.

[Methicillin resistant Staphylococcus aureus and glycopeptides (vancomycin, teicoplanin): in vitro selection of resistance]. / Staphylococcus aureus résistant à la méticilline et glycopeptides (vancomycine, teicoplanine): sélection de résistance in vitro.

By repeated and successive treatments of five strains of methicillin-resistant Staphylococcus aureus with sub-inhibitory concentrations of vancomycin and of teicoplanin, the authors have confirmed that selection of resistant strains could be obtained more easily with teicoplanin than with vancomycin. Moreover, we have shown that treatments with subinhibitory concentrations of teicoplanin could also influence the activity of vancomycin, although the strains have never been in contact with the latter antibiotic. This could account, at least in part, for the downhill evolution of the activity of glycopeptides against staphylococci, observed this last years. Indeed, the efficacy of these antibiotics upon which treatment of severe infections due to multiresistant staphylococci relies, is lowering. Considering the challenge, this risk is worth being not only evaluated by a reinforced epidemiologic surveillance, but also limited by more severe criteria for the prescription and the follow-up of treatments with glycopeptides.

Utility of C-reactive protein measurements for empyema diagnosis after pneumonectomy.

Serum C-reactive protein (CRP) levels were studied serially during the postoperative period in 151 consecutive patients who underwent pneumonectomy. Virtually all patients who had a simple postoperative course (115 of 120), as well as 9 patients who had a bronchial infection of the remaining lung, 3 with a pulmonary embolus, and 2 who suffered postoperative bleeding requiring reoperation, demonstrated a similar postoperative evolution in their CRP values: a rapid postoperative rise until a peak or a plateau (mean peak value, 132 +/- 25 mg/L) was reached within 3 to 6 days, followed by a progressive decline to a value of less than 75 mg/L on day 9, and less than 50 mg/L on day 12. Conversely, all 12 patients who suffered empyema postoperatively, as well as 3 patients with bacterial pneumonia, 1 patient with chylothorax, and 1 patient with inflammatory pericarditis, demonstrated either a markedly persistent elevation in their CRP values or a secondary rise in the levels which exceeded 100 mg/L. Because of the high sensitivity (100%) and specificity (91.4%) of the CRP levels in detecting postpneumonectomy empyema, we recommend the routine use of this measure. Furthermore, a low CRP value after pneumonectomy (less than 50 mg/L) may help in deciding whether to confidently discharge a patient from the hospital in the absence of empyema. The negative predictive value of this method was found to be 100%.

A Lie group approach to a neural system for three-dimensional interpretation of visual motion.

A novel approach is presented to neural network computation of three-dimensional rigid motion from noisy two-dimensional image flow. It is shown that the process of 3-D interpretation of image flow can be viewed as a linear signal transform. The elementary signals of this linear transform are the 2-D vector fields of the six infinitesimal generators of the 3-D Euclidean group. This transform can be performed by a neural network. Results are also reported of neural network simulations for the 3-D interpretation of image flow and a comparison of the performance of this approach with that using conventional methods. Computer simulation results verify the Lie-group-based neural network approach to three-dimensional motion perception.

[Antibiotic and antiseptic prophylaxis in thoracic surgery. Controlled study]. / Prophylaxie antibiotique et antiseptique en chirurgie thoracique. Etude contrôlée.

The aim of this report was to evaluate perioperative antibiotherapy and antiseptic irrigation of the operative site in the prevention of post-pneumonectomy empyema. From 1984 to 1986, 171 patients undergoing pneumonectomy at our institution for bronchogenic carcinoma were randomly selected in 2 groups: group I (85 patients) received a "classical" prophylaxis: irrigation of the operative site with saline, plus a 7-day antibiotherapy (minocycline 200 mg/24 h) started the evening following surgery; group II (86 patients): irrigation of the operative site was performed with Povidone iodine (dilution 5%); antibiotherapy (cefotiam was given for a short period (2 g intraoperatively, 2 g 12 hours and 24 hours following surgery). We used a "pragmatic" approach in order to choose, whatever the results would be, a type of perioperative antibiotherapy. We thus accepted the choice, without the help of statistical tests, of the therapy that would best prevent infection, and, if both regimens would demonstrate the same efficacy, to leave the choice at random. The only statistical test was to calculate the "gamma-risk" that we choose the worst among the 2 regimens. Although no significant difference in the overall infection rate was observed between the 2 groups, there were 9 empyemas (5 of those with bronchial fistula) in group I and 3 empyemas (2 of those with bronchial fistula) in group II. The cefotiam-povidone iodine regimen is thus better than the minocycline-saline regimen in the prevention of post-pneumonectomy empyema (3.5% v.s. 10.5%). The "gamma-risk", ie the probability that the minocycline-saline regimen is the best, calculated from these percentages, is 0.03.

[Adaptation of the Autobac system to the determination of serum concentrations of antibiotics]. / Adaptation du système Autobac à la détermination des concentrations sériques d'antibiotiques.

Adaptation of the Autobac system to the determination of antibiotic concentrations in the serum. In face of increasing interest in antibiotic assays, particularly for those effective within a narrow range, we have combined the Autobac system with a rapid microbiological assay in liquid medium which involves the use of a laser nephelometer. This method is rapid, simple, accurate and inexpensive. It allows laboratories with the Autobac system to monitor closely antibiotic treatments.

[Sensitivity to cephalosporins of coagulase-negative methicillin-resistant staphylococci. In vitro studies by different methods]. / Sensibilité aux céphalosporines de staphylocoques coagulase négatifs méticilline résistants. Etude in vitro selon différentes méthodologies.

The activity of five cephalosporins has been studied with 80 coagulase-negative methicillin-resistant Staphylococcus strains (SCN meti-R) isolated from hospitalized patients. It has been evaluated in vitro under different conditions, in liquid as well as solid media. Results show that in all cases cefamandole has the highest activity on SCN meti-R. Thus cefamandole is quite effective for the prophylaxis of Staphylococcal infections. Furthermore the association of cefamandole with other antibiotics should be tested as an alternative to vancomycin for the treatment of SCN meti-R severe infections.