The effect of subinhibitory concentrations of some antibiotics on the hydrophobicity of gram-negative bacteria.

Cell surface hydrophobicity is currently regarded as an important factor in promoting bacterial adherence to a wide variety of surfaces. This feature was investigated in some Gram-negative bacteria isolated from urinary tract infections and the extent to which their surface characteristics were affected by subinhibitory concentrations of some antibiotics was assayed. Surface properties were evaluated using the salting-out technique (SAT) and bacterial absorption to n-hexadecane (BATH). SAT showed that all except 3 Escherichia coli strains were autoaggregating. BATH detected more hydrophobic characteristics in the stationary phase of bacterial growth. Pretreatment with antibiotics generally reduced hydrophobicity and thus affected the initial reversible phase of attachment of bacteria to eukaryotic cells.

[Evaluation of in vitro antibiotic sensitivity: critical features of the MIC]. / Valutazione della sensibilità "in vitro" agli antibiotici: aspetti critici della MCI.

Current methods for the "in vitro" study of antibiotic activity, as minimum inhibitory concentration, expose bacteria to constant concentrations of antibiotics. The "in vivo" situation is significantly different, since the antibiotic concentration changes with time. Pharmacokinetic models are "in vitro" experimental systems that seek to simulate conditions of exposure of bacteria to antimicrobial agents that exist in blood and tissues. All of these systems are complicated constructions. A new simple "in vitro" kinetic model, based on solid phase growth, is described.

[Urinary infections: observations on the frequency of microbial isolation at the hospital environment and its surroundings]. / Infezioni urinarie: osservazioni sulla frequenza di isolamenti microbici in ambiente ospedaliero e sul territorio.

Numerous studies have been carried out to specify bacterial frequencies in the urinary tract infections. In such researches the prevalence of Gram negative bacterial species has generally emerged, the most part of these ones would be Enterobatteriaceae (and among them E. coli has a special prominent position); on the other hand several Authors have often found, among other bacterial groups (Gram positive bacteria, Pseudomonas etc.) involved in such pathologies, some differences (also remarkable) in relation to various factors, among them, the hospitalizing condition, the clinical situation, the type of infection etc. In this research we have carried out a statistical analysis of the bacterial frequencies relative to 321 positive urine cultures, trying to point out their differences in relation to hospitalized or ambulatorial patients and to single are mixed infections; above all with regard to three bacterial groups: Enterobatteriaceae, Pseudomonas species and Gram positive bacteria. The most evident result has been the absolute prevalence of Enterobacteriaceae, among them the E. coli has represented, almost always, the most frequent isolated species, followed by Proteus mirabilis, in every kind of patient (hospitalized or ambulatorial) and infection, single or double (we didn't notice, in this research, infections supported by more than two species). Moreover, we noticed, but with less clearness, especially in relation to the numerical dimension of the observations and to the short comparison of the two kind of patients, some indications pointing out that hospitalized patients (in comparison with the ambulatorial) were charged with a major frequency of the two kind of patients, some indications pointing out that hospitalized patients (in comparison with the ambulatorial) were charged with a major frequency of infections supported by Gram + bacteria and Proteus mirabilis, while the Pseudomonas species presented an opposite behaviour (contrary to what several Authors generally report in literature: but a pollution problem of the specimen might have had some influence); and as regard the single infections we observed, among them, a greater frequency of the E. coli and Gram + bacteria than among the double infections, while the Pseudomonas species happened the contrary.

[Combining indirect hemagglutination with the direct agglutination as a parameter for evaluating patients sent for serological verification of toxoplasmosis]. / L'abbinamento dell'emoagglutinazione indiretta (IHA) con l'Agglutinazione diretta (AD) quale parametro valutativo di pazienti inviati per l'accertamento sierologico della toxoplasmosi.

The importance that Toxoplasma gondii congenital infection may assume is still representing a stimulus for trying to improve Toxoplasmosis serological diagnosis; task, this one, which Laboratory is charged with, and that is often hard, particularly when we have to value the possibility of an infection in progress. With the purpose to complete the results obtained in a preceding work of ours, we have valued two among the most commonly used tests for Toxoplasmosis serodiagnosis, the AD (direct agglutination provided by BioMerieux) and the IHA (indirect haemoagglutination provided by Behring), together and separately, in order to make use of their coupling with major security and effectiveness, on the ground of the results obtained on two different groups of individuals, in the number of 125 for each group; for these groups it was possible to expect a different index of receptivity and a different percentage of recent or in progress infections. It was come out, as regards the IHAm a very good degree of assurance in trying to single out the past immunity, while this test wouldn't generally seem to be able to offer sufficient indications to distinguish the recent or in progress infection from past immunity, as it often declares, in fact, middle-high titres also in cases probably referable to the last mentioned situation. The AD has offered a good tribute in estimating the past immunity and it would also appear to give assurance in singling out recent or in progress infection (thanks to the possibility to determine IgM presence); while the presumed capacity of this test in revealing cases of very early infection has resulted not sufficiently assured. In substance the coupling of the two test, which in the direct comparison have shown a good correlation, but also several discordances, seems to be an useful procedure of reciprocal confirmation as regards the singling out of immunity; while the possibility of showing the recent or in progress infection--anyway, always a difficult task, above all, when, as it happened in this research, we deal with it without being able to follow the titre evolution in the time-should be entrusted with major certainty to the AD.

[Aztreonam: monocenter microbiological study with prevention experience in surgery]. / Aztreonam: indagine microbiologica monocentrica con esperienza di profilassi in chirurgia.

Aztreonam is a monobactam antibiotic active against aerobic gram-negative bacteria. The susceptibility of 127 urinary tract isolates to aztreonam, cefotaxime, cefonicid and ceftazidime was determined. Aztreonam showed good antibacterial activity even against Pseudomonas spp. Only 7 bacterial strains were resistant to aztreonam. The clinical efficacy and pharmacokinetics of aztreonam were assessed in two patients treated for urinary tract infections. The concentrations of aztreonam in serum and urine are reported. Aztreonam safety was evaluated on 20 patients given aztreonam immediately prior to an elective abdominal, urinary or gynecological operation. The results provide support for the use of aztreonam for prophylaxis.

[Antibiotic resistance at a hospital environment. Observations from 1980 to 1986]. / Antibioticoresistenza in ambiente ospedaliero. Osservazioni dal 1980 al 1986.

A total of 1659 bacteria Strains were examined for susceptibility to different drugs by the Kirby-Bauer method. The isolates came from the General Medicine ward of Castellamonte's hospital (USSL 40). The results were retrospectively studied and statistically elaborated. The study lasted from 2 to 7 years depending on the antibiotic considered. The isolates included: Escherichia coli, Klebsiella spp., Serratia spp., Citrobacter spp., Proteus mirabilis, Proteus IND+, Pseudomonas aeruginosa, Pseudomonas spp., Staphylococcus aureus, Staphylococcus spp., Streptococcus faecalis. Penicillines, Cefalosporines, Aminoglycosides, Quinolones, Tetraciclines, Nitrofurantoin, Macrolides, Rifampins, Lincosides and peptide antibiotics were tested. The results of this study can be useful for the choice of the antibiotics in non-specific therapy of infectious diseases and show the frequency of isolation of resistant strains from hospitalized patients. Furthermore it would be important to constitute a regional-epidemiological centre of Infectious Diseases.

In vitro antimicrobial activity in comparison with tonsillar tissue penetration of mezlocillin.

The aim of this study was to determine the role of mezlocillin, a new acylureidopenicillin, in otorhinolaryngology. One hundred and forty-four bacterial strains were isolated from 100 patients suffering from infections of the oropharyngeal tract. Among the isolates only 10 (6.9%) resulted in being mezlocillin-resistant by the agar diffusion method. Minimum inhibitory and minimum bactericidal concentrations were also determined. Pharmacokinetic parameters e.g., diffusion in tonsillar tissue and serum concentrations, were studied. Mean mezlocillin tonsillar levels of 3.5 micrograms/g and 1.8 micrograms/g and serum concentrations of 60.2 micrograms/ml and 10.6 micrograms/ml, 1 h and 4 h respectively after administration, were found.

[Teicoplanin in otorhinolaryngology]. / La teicoplanina in otorinolaringoiatria.

In this study the clinical microbiologic efficacy of a new antibiotic, Teicoplanin, has been reported. Teicoplanin was given to both male and female patients (200 or 400 mg/die doses) suffering from ORL infections. The microbial flora of the inflammatory focus was checked before and after antibiotic administration. Complete microbiologic eradication occurred in 13 cases of the 18 examined; in 3 cases was observed reinfection and in 2 cases the isolates were not sensitive to the antibiotic tested.

[Novel characteristic of the genus Campylobacter: Campylobacter-like organisms]. / Nuove caratteristiche del genere Campylobacter: I "Campylobacter like organisms".

The first report of human infections due to Campylobacter dates back to 1947. These microorganisms, classified initially as Vibrio, had been known for many years as agents of several diseases in animals. In 1963 they were grouped in the new Genus Campylobacter belonging to Spirillaceae. Campylobacter are ever more important, particularly C. jejuni, which is an ubiquitous agent of diarrhoea in children. Other microorganisms of this Genus, the "gastric Campylobacter-like organisms" type I, otherwise known as Campylobacter pyloridis, are responsible for gastric diseases.

[Microbiological-clinical study on the efficacy of a new antibiotic: teicoplanin]. / Studio microbiologico-clinico sull'efficacia di un nuovo antibiotico: la teicoplanina.

Teicoplanin is a new antibiotic isolated from the fermentation broth of Actinoplanes teichomyceticus nov. sp. It's a glycopeptide antibiotic belonging to the same family as vancomycin, active against Gram-positive bacteria. The antimicrobial activity of this drug was evaluated in 32 patients suffering from different infections due to Gram-positive bacteria. Among the 36 Gram-positive microorganisms isolated, 15 staphylococci were methicillin resistant, 10 were sensitive, 1 was intermediate and for another one the methicillin susceptibility was not evaluated. After the treatment with teicoplanin, cure and improvement occurred in 26 cases (81%), in 2 cases the therapy failed (6%), in 2 cases there was a relapse and 2 cases were not evaluable. From this clinical study Teicoplanin results safe and effective in the therapy of Gram-positive infections.

[Frequency of methicillin resistance varies with conditions, in a population of staphylococci from a hospital environment]. / Frequenze di meticillino-resistenza e variabili che le modificano, su una popolazione di stafilococchi di provenienza ospedaliera.

The incidence of methicillin-resistant Strains is increasing in these last years. This increase is particularly evident in Strains isolated from hospital environments. In this work we evaluated the methicillin-resistance of 58 Staphylococcus Strains, isolated from a surgical intensive care ward, in various experimental conditions, which changing in: culture medium, inoculum, incubation period and antibiotic concentration. Besides this we took in consideration various factors which can influence the frequency of methicillin-resistance and can also lead to errors in the evaluation itself. From our study we can conclude that the factors are: survey "in vitro" of the resistance or of the sensitivity, exclusion or inclusion of staphylococci different from Staphylococcus aureus, double count of the same Strains isolated in different times.