Sixteen aromatic amines and azo-derivatives were studied. They were: benzidine; 2-acetylaminofluorene; 3'-methyl-p-dimethylaminobenzene; o-aminoazo-toluene; p-dimethylaminoazobenzene; 2,4-diamino-toluene; 4,4'-oxydianiline; 2,4-diaminoanisole; 4,4'-methylenedianiline; 2-naphthylamine; Auramine O; Rhodamine B; Ponceau MX; 1-naphthylamine; p-aminoazobenzene and aniline. The compounds were examined for their capability to induce alkaline DNA fragmentation in rat liver after treatment in vivo, for their mutagenicity in the Salmonella strains TA 98 and TA 100, for their acute toxicity and for their carcinogenicity in mice and rats. For each parameter a quantitative potency index was established, and the correlation existing amongst the different parameters investigated. Only mutagenicity in the strain TA 98 was slightly correlated with carcinogenic potency (r = 0.408). DNA fragmentation and toxicity were not correlated with carcinogenicity. A significant correlation was found between DNA fragmentation and toxicity (r = 0.539). No correlation was found between DNA fragmentation and mutagenicity. The lack of correlation between DNA fragmentation and carcinogenicity is in contrast with previous results obtained with a family of hydrazine derivatives (12) and a group of nitrosocompounds (22). For these two groups of chemicals correlation between DNA fragmentation and carcinogenicity existed, but not between carcinogenicity and mutagenicity in the Ames' test. It is suggested that short term tests can perform very differently for different classes of chemicals.

Acquired metallo-β-lactamases (MBLs) can confer broad-spectrum β-lactam resistance (including carbapenems) not reversible by conventional β-lactamase inhibitors and are emerging resistance determinants of remarkable clinical importance. In 2001, multidrug-resistant Pseudomonas aeruginosa carrying blaVIM MBL genes were found to be widespread (approximately 20% of all P. aeruginosa isolates and 70% of the carbapenem-resistant isolates) at Trieste University Hospital. Clonal diversity and heterogeneity of resistance determinants (either blaVIM-1-like or blaVIM-2-like) were detected among MBL producers. This evidence is the first that acquired MBLs can rapidly emerge and establish a condition of endemicity in certain epidemiologic settings.

Integron carriage by 36 epidemiologically unrelated Acinetobacter baumannii isolates collected over an 11-year period from patients in six different Italian hospitals was investigated. Sixteen type 1 integron-positive isolates (44%) were found, 13 of which carried the same array of cassettes, i.e., aacC1, orfX, orfX, and aadA1a. As ribotype analysis of the isolates demonstrated a notable genetic diversity, horizontal transfer of the entire integron structure or ancient acquisition was hypothesized.Clinical isolates of Acinetobacter baumannii are frequently resistant to a wide range of antibiotics (1), but, compared to other gram-negative bacteria, little is known about the mechanism(s) by which these bacteria acquire resistance genes. Recently, a major role in the dissemination and evolution of antimicrobial resistance in many gram-negative organisms has been attributed to integrons. These are genetic elements consisting of a gene encoding an integrase (intI) flanked by a recombination site, attI, where mobile gene cassettes, mostly containing antibiotic-resistance determinants, can be inserted or excised by a site-specific recombination mechanism catalyzed by the integrase (16). Different integron types have been recognized on the basis of the sequence of the integrase gene.The presence of type 1 and type 2 integrons has already been described in members of the genus Acinetobacter of both clinical (2,6,8,9,14,(17)(18)(19)23) and environmental (13) origin. In particular, epidemic strains of A. baumannii (9) were found to carry these elements with high frequency.The aim of this study was to evaluate the diffusion of type 1 integrons among clinical isolates of A. baumannii from our country and to carry out a molecular characterization of their gene cassette arrays.To this purpose, 36 epidemiologically unrelated clinical isolates of A. baumannii collected over an 11-year period from six Italian hospital settings were selected (Table 1). The isolate AC-54/97 was already known to carry two type 1 integrons with variable regions of similar size, of which one (In42) had been previously characterized (17). All isolates were identified by amplified ribosomal DNA restriction analysis (4) and were subjected to ribotyping to investigate their genetic relatedness.Genomic DNA was extracted (5), digested by SalI, EcoRI, or ClaI (Roche Diagnostics SpA, Monza, Italy), and processed as described by Gerner-Smidt (7). Banding patterns were analyzed by GelComparII software (Applied Maths, Kortrijk, Belgium) with the Dice coefficient for evaluating similarity. Isolates were included in the same ribotype when their similarity coefficient was equal or superior to 0.85.By combining the results obtained with the three enzymes, all the isolates could be divided into 28 groups, each of them displaying a unique combination of ribotypes (Table 1). Results of this analysis overall indicated a notable genetic diversity of the selected isolates.The presence of intI1-related sequences was initially investigated by dot blot hybridization of genom...

A new rapid microdilution method, employing the dye resazurin as an indicator of mycobacterial growth, was developed to evaluate drug susceptibility of Mycobacterium tuberculosis reference strain H37Rv and of 13 M. tuberculosis susceptible or multidrug-resistant clinical strains. Different growth conditions were evaluated. The MICs of isoniazid, rifampicin, streptomycin and ethambutol were determined by the Microdilution Resazurin Assay (MRA) and the results compared with those obtained by the agar proportion method; complete agreement was always obtained. MRA resulted in a rapid, reliable, simple and inexpensive coloured method suitable for testing the susceptibility of M. tuberculosis clinical strains to first-line drugs; its employment in evaluating new antibacterial molecules is also suggested.

Mediterranean herring gulls (Larus cachinnans) were investigated as a possible reservoir of antibiotic resistant bacteria and of cassette-borne resistance genes located in class 1 integrons. Two hundred and fourteen isolates of the family Enterobacteriaceae were collected from cloacal swabs of 92 chicks captured in a natural reserve in the North East of Italy. They showed high percentages of resistance to ampicillin and streptomycin. High percentages of resistance to trimethoprim/sulfamethoxazole were found in Proteus and Citrobacter and to chloramphenicol in Proteus. Twenty-two (10%) isolates carried the intI1 gene. Molecular characterization of the integron variable regions showed a great diversity, with the presence of 11 different cassette arrays and of one integron without integrated cassettes. The dfrA1-aadA1a and aadB-aadA2 cassette arrays were the most frequently detected. Also the estX cassette, alone or in combination with other cassettes, was detected in many isolates. From this study it is concluded that the enteric flora of Mediterranean herring gulls may act as a reservoir of resistant bacteria and of resistance genes. Due to their feeding habits and their ability to fly over long distances, these free-living birds may facilitate the circulation of resistant strains between waste-handling facilities, crops, waters, and urban areas.