The Inactivation of the Putative Two-Component System Sensor PA14_27940 Increases the Susceptibility to Several Antibiotics and Reduces the Motility of Pseudomonas aeruginosa

The identification of targets whose inactivation increases the activity of antibiotics helps to fight antibiotic resistance. Previous work showed that a transposon-insertion mutant in the gene PA14_27940 increases Pseudomonas aeruginosa susceptibility to aminoglycosides. Since polar effects may affect the phenotype, in the present work, we generated an in-frame PA14_27940 deletion mutant. A PA14_27940 deletion increased the susceptibility to aminoglycosides, tetracycline, tigecycline, erythromycin and fosfomycin. Excepting fosfomycin, the other antibiotics are inducers of the MexXY efflux pump. MexXY induction is required for P. aeruginosa resistance to these antibiotics, which is post-transcriptionally regulated by the anti-repressor ArmZ. Although mexXY is inducible by tobramycin in ΔPA14_27940, the induction level is lower than in the parental PA14 strain. Additionally, armZ is induced by tobramycin in PA14 and not in ΔPA14_27940, supporting that ΔPA14_27940 presents an ArmZ-mediated defect in mexXY induction. For its part, hypersusceptibility to fosfomycin may be due to a reduced expression of nagZ and agmK, which encode enzymes of the peptidoglycan recycling pathway. ΔPA14_27940 also presents defects in motility, an element with relevance in P. aeruginosa's virulence. Overall, our results support that PA14_27940 is a good target for the search of adjuvants that will increase the activity of antibiotics and reduce the virulence of P. aeruginosa.

Collateral Sensitivity to Fosfomycin of Tobramycin-Resistant Mutants of Pseudomonas aeruginosa Is Contingent on Bacterial Genomic Background

Understanding the consequences in bacterial physiology of the acquisition of drug resistance is needed to identify and exploit the weaknesses derived from it. One of them is collateral sensitivity, a potentially exploitable phenotype that, unfortunately, is not always conserved among different isolates. The identification of robust, conserved collateral sensitivity patterns is then relevant for the translation of this knowledge into clinical practice. We have previously identified a robust fosfomycin collateral sensitivity pattern of Pseudomonas aeruginosa that emerged in different tobramycin-resistant clones. To go one step further, here, we studied if the acquisition of resistance to tobramycin is associated with robust collateral sensitivity to fosfomycin among P. aeruginosa isolates. To that aim, we analyzed, using adaptive laboratory evolution approaches, 23 different clinical isolates of P. aeruginosa presenting diverse mutational resistomes. Nine of them showed collateral sensitivity to fosfomycin, indicating that this phenotype is contingent on the genetic background. Interestingly, collateral sensitivity to fosfomycin was linked to a larger increase in tobramycin minimal inhibitory concentration. Further, we unveiled that fosA low expression, rendering a higher intracellular accumulation of fosfomycin, and a reduction in the expression of the P. aeruginosa alternative peptidoglycan-recycling pathway enzymes, might be on the basis of the collateral sensitivity phenotype.

The Cellular Abundance of Chemoreceptors, Chemosensory Signaling Proteins, Sensor Histidine Kinases, and Solute Binding Proteins of Pseudomonas aeruginosa Provides Insight into Sensory Preferences and Signaling Mechanisms

Chemosensory pathways and two-component systems are important bacterial signal transduction systems. In the human pathogen Pseudomonas aeruginosa, these systems control many virulence traits. Previous studies showed that inorganic phosphate (Pi) deficiency induces virulence. We report here the abundance of chemosensory and two-component signaling proteins of P. aeruginosa grown in Pi deficient and sufficient media. The cellular abundance of chemoreceptors differed greatly, since a 2400-fold difference between the most and least abundant receptors was observed. For many chemoreceptors, their amount varied with the growth condition. The amount of chemoreceptors did not correlate with the magnitude of chemotaxis to their cognate chemoeffectors. Of the four chemosensory pathways, proteins of the Che chemotaxis pathway were most abundant and showed little variation in different growth conditions. The abundance of chemoreceptors and solute binding proteins indicates a sensing preference for amino acids and polyamines. There was an excess of response regulators over sensor histidine kinases in two-component systems. In contrast, ratios of the response regulators CheY and CheB to the histidine kinase CheA of the Che pathway were all below 1, indicative of different signaling mechanisms. This study will serve as a reference for exploring sensing preferences and signaling mechanisms of other bacteria.

[Evaluation of atopy risk factors during the first year of life. Multicentric study]

The AA studied 406 newborn babies during the 1st year of life in order to verify the correlation between atopy risk factors and the appearance of early symptoms, particularly gastroenteric (GE). The results obtained did not demonstrate a significant difference concerning the blood cord IgE level and subsequent appearance of food allergy symptoms, whereas positive familiarity showed a better correlation. No significant difference was observed between breast--or formula--fed infants, or between those weaned before or after the 5th month of life. The comparison of dietary regimen adopted during the 1st quarter in the asymptomatic and atopic children respectively, demonstrated that the presence of predisposing factors influences the appearance of GE symptoms much more than the diet in itself. An allergologic study, randomly performed by Prick-test in 156 cases and by RAST in 200 cases, showed a prevalent, positive response with RAST technique in symptomatic children.

[Alport syndrome: 15-year follow-up in 28 cases]

Twenty-eight patients aged from 18 mo. to 23 y. (at the onset of the diseases) affected by Alport's syndrome (AS), were studied during last 15 years. The mean time of observation was 10 +/- 0.7 years. Two cases progressed to renal failure at 15 and 21 years respectively, while 26 patients have normal renal function within the 2a decade of life. The diagnosis of hereditary nephritis (AS) was based on the following criteria: Existence of affected kindred. Perceptive deafness. Basal membrane ultrastructural abnormalities. A late exact diagnosis was made in some patients without ascertainable familiarity and without early ultrastructural glomerular study. Perceptive deafness occurred chiefly after 6-8 years of life, increasing the diagnostic difficulties. Isolated hematuria was present in 18 cases (64%) and associated proteinuria (or NS) in 10 (36%). Recurrent otitis media worsened the hearing loss in 5 cases (17.83%). An immuno-allergologic study was carried out because of the great frequency of allergic diseases, respiratory mainly. A significative decrease of plasmatic and secretory IgA was observed in those patients who underwent to recurrent otitis media. The features suggestive of AS in our patients, in addition to the familiarity, were gross haematuria in childhood and diffuse GBM splitting and splintering. Heavy proteinuria and nephrotic syndrome associated to early deafness and to male sex indicate a poor prognosis; but several females also can be affected by serious course of the disease.

The quantitative determination of neomycin sulphate by a diffusion technique on agar plates by the method of the European Pharmacopoeia, 2nd edition--evaluation of precision and reproducibility of the method

The medium recommended by the European Pharmacopoeia (EP), 2nd edition, for the microbiological determination of neomycin by the agar diffusion method was tested and compared with the medium recommended by the EP, 1st edition. The tests were carried out in different laboratories. The medium recommended by the EP, 2nd edition, gave greater precision and reproducibility than the previous medium. The possibility of using a reference standard of almost pure neomycin B for both the determination of framycetin and neomycin was evaluated. The results demonstrated that the medium recommended by the EP, 2nd edition, gave better precision and reproducibility. Difficulty in achieving valid assays was practically the same with both media.

[Arterial hypertension in childhood. Study of a school population]

Most Authors fix the upper limits of normal blood pressure at 90 degrees percentile according to age. Nevertheless in their investigations different instruments were used and they often didn't relate in detail the position of the subject during the measurement. Other factors, influencing blood pressure values, have been often left out: relation with meals, room temperature, pain, drugs, stress, etc. The prevalence of hypertension in pediatric age in literature is 0,6 - 12,4% with several intermediate values. The first very important research concerning the hypertension in pediatric age was carried out by Londe et Coll., conducted among 1593 children (785 males and 798 females); they estimated mean values and percentiles according to age and sex. In the present study the A.A. saw 346 children (161 females and 185 males), 11-15 years old, observed at school, in a comfortable room. Pressure measurement was done twice in the same morning with half an our interval. Systolic pressure, 4 degrees and 5 degrees Korotkoff tones, was noticed. 11% of the children had systolic pressure values under 50 degrees percentile, 35,3% between 50 degrees and 90 degrees percentile and 43,1% had values equal or greater than 90 degrees percentile at the first measurement. The third group went down to 30,6% (106 cases) at the control (after an half an hour). This reduction shows the importance of the emotional factors in the P.A. variations. The 106 children who had systolic and/or diastolic values equal or greater than 90 degrees percentile were controlled again after a week. 92 maintained the same values. They were called for the third sitting 1-6 months later. 45 subjects agreed to our invitation and it was possible to point out that high blood pressure values persisted in 31 children (that is 8,9% of all examined cases). Following correlations were observed: body weight-blood pressure values (either systolic or diastolic ones) and so cutaneous plica-pressure values (p less than 0,01); moreover 50% of the 31 hypertensive children had hypertensive parents; the most frequent subjective symptom (13 cases) was cephalalgia. None of the studied school children showed either clinic or biochemical abnormal data, so that it was possible to define their hypertension as "essential".

[A thymus extract (thymomodulin) in the prevention of childhood asthma]

41 children aged 2-12 years affected with bronchial asthma, have been treated orally with a thymus extract for three months (sep.-oct.-nov. 1980); a further period of treatment has been repeated during the month of March 1981. The following immunologic tests have been performed before therapy, 2 months after therapy withdrawal and 12 months after the second therapeutical discontinuance: plasmatic immunoglobulins (P. Ig), C3-C4 complement's factors, E-rosette forming cells (both active and total), surface immunoglobulins (IgS), PHA lymphocyte stimulation. Periodic anamnestic and clinical controls of patients revealed a significant reduction of asthmatic attacks during the months of observation, in comparison with the crises remarked in the same period of the previous year (the mean number of crises per child being 6 and 0.7 respectively before and after treatment, P less than 0.001). The immunologic tests, despite the clinical results, did not show significant modifications at the 1st control. Nevertheless the control carried out 12 months after the second therapeutical withdrawal demonstrated: IgG and IgM plasmatic levels significantly increased (1097 +/- 63 vs 906 +/- 45 and 122 +/- 10 vs 104 +/- 10 respectively, P less than 0.02) while IgE, C3-C4 plasmatic levels significantly decreased (232 +/- 57 vs 396 +/- 71, 132 +/- 6 vs 162 +/- 7, 22 +/- 2 vs 30 +/- 2 respectively, P less than 0.005). No side effects have been seen in all the patients treated.

[Correlation between plasma IgE and IgA in infant nephrosis and nephrotic syndrome]

A study on IgE - IgA plasmatic level has been carried out in the acute phase and in remission of minimal changes nephrosis (MCN) and in glomerulonephritis with nephrotic syndrome (NS). The results obtained are the following: 1) Mean values of Ig classes were impaired in comparison with the normal values of children of the same age, both in MCN and in NS. 2) IgE were increased, particularly in children over 6 years in the MCN acute phase; the values decreased within normal after the remission was achieved. 3) IgA, on the contrary, were decreased in the subjects over 6 years, in the MCN acute phase. 4) No significant correlation was found between the two Ig classes. 5) The modifications of the Ig plasmatic level during the remission, after corticosteroid therapy was characterized by IgE reduction; IgA were only slightly, but not significantly, decreased in the same phase.

[Diagnostic and therapeutic problems in lupus nephritis]

A review of the SLE in the paediatric age in performed to underline the peculiarity of the disease in children: age, frequency, symptomatology, renal histology, clinical course, therapy and correlated side effects are reported according to literature data. The A.A. describe six cases of lupus nephritis, observed in the last few years, which confirm the diagnostic difficulties and the wide variety in the evolution of the disease. A favourable course of the disease was obtained in three cases, with corticosteroid and immuno-depressive treatment (used in association and/or alternatively); a fourth case developed some therapeutic complications among which an avascular bilateral bone necrosis, leucopenia, alopecia and herpes zoster. In two cases the SLE led to chronic renal failure owing to many relapses of the disease, enhanced by therapeutic break or dosage reduction. A careful surveillance of these patients is of fundamental importance in the management of the disease in order to obtain the longer survival and the lesser side effects.

[Asymptomatic microhematuria]

Microscopic haematuria is an urinary finding more and more frequently observed in routine analysis in childhood; the diagnostic problems, most of which unresolved, are yet the principal questions of concern. We have studied 123 patients during five years from 1975 to 1980, and followed them for 1-8 years (mean 4 years). Our experience allowed us to consider "normal" or without remarkable pathologic significance a urinary finding less than or equal to 5.000 RBC/m' at the Addis count. Such findings were pointed out in 55 cases (44%); 27 patients (22%) had 5-10.000 RBC/m', 34 cases (27,6%) presented 10-50.000 RBC/m' and 7 cases (5,7%) had more then 50.000 RBC/m'. The familiar background, the clinical, biological and immunological data, the roentgenographic investigations and the renal biopsy carried out in the 4 groups of patients, led us to the following conclusions: 1) 26% of the 123 cases had a "unexplained;; microscopic haematuria with complete lack of anamnestic data, symptomatology and with normal biological findings. 2) in 65,8% of the cases it was possible to discover frequent upper respiratory tract infections (and allergy in 5,6% of them). 3) in 26% of the patients we discovered a previous or actual genito-urinary (10,5% and 15,5% respectively) infection: 9,4% of 96 urography demonstrated a variable degree of nephro-urological abnormalities. 4) 23 children (18,7%) was selected for renal biopsy, primarily by the hypocomplementemia and positive anti-DNA ab. test, and secondly by elevated degree of microhematuria. The histological and immunohistochemical studies demonstrated the presence of mesangial proliferation glomerulonephritis with IgG-IgA-C3 deposits in 7 cases (30% of the cases biopsied and 5,6% of the total), 69,6% of the cases had only minimal charges with negative immunofluorescence. 5) A mean follow-up of 4 years in two groups of patients (less than or greater than 6 years of age) has demonstrated that microscopic haematuria remains unchanged in 18-19% of both groups. A more marked improvement or normalization has been documented in the children more than 6 years aged (p less than 0,001) while a worsening has been observed in the children less than 6 years aged (p less than 0,005), with a statistically significant difference between the two groups considered.

[Study of factors affecting the renin-angiotensin-aldosterone system in the premature infant]

Renin-angiotensin-aldosterone system (RAA), Na-K dietary intake and Na-K urinary excretion in 36 premature babies have been investigated. The plasmatic renin activity (PRA) and plasmatic aldosterone level (P-aldo) resulted significantly increased in comparison with children previously studied, 20 days - 23 months old (p less than 0,01). P-aldo demonstrated, in premature babies, a negative correlation with Na-K intake and urinary excretion (p less than 0,001 and less than 0,01 respectively); in the groups nourished with maternal milk or "adapted" formulae P-aldo mean value was significantly more elevated than in the group nourished with formulae "unadapted" (p less than 0,01). A different Na dietary intake seems to be the most important factor influencing P-aldo level also in premature babies. No correlation between PRA - electrolyte excretion was found in any group. The main factor influencing PRA seems to be the age of infants as well as, probably, other hemodynamic mechanisms.

[Is it possible to improve the prognosis of congenital nephrosis?]

Two cases of congenital nephrotic syndrome (C.N.S.) with a prolonged survival are related. The AA. outline some clinical and immunological features which are already known but not currently employed to therapeutic ends. Probably due to metabolic disorders, the biological and clinical hypothyroidism is a prominent problem which worsens either poor skeleton maturation or neurological development of these patients; adequate doses of thyroid hormone produced a marked increase of the muscular tone, skeleton maturation and neuropsychological development in both patients. Periodic plasma administration (2-3 times monthly) during the first year of life, and a great care to avoid all extra-family contacts and infections in the same period, resulted to be the prevalent reason of the prolonged survival of these children (the plasma acting as a source of proteins and immunoglobulins). The immunologic assessment demonstrated in both children as marked depression of T-cells number and function, besides a hypogammaglobulinemia. This aspect of the immunocompetent system is similar in C.N.S. and nephrotic syndrome of the aged children and perhaps could approach the pathogenesis of the two diseases. The cases related demonstrate that a better assistance is possible and necessary in order to obtain the longest survival of these patients and therefore the best results in dialitic treatment and in transplantation programs.