A selection of 167 Corynebacterium diphtheriae strains isolated in Romania, the Russian Federation and the Republic of Moldova were analysed by biotyping, phage typing, the toxin production test and by molecular techniques such as ribotyping, pulsed field gel electrophoresis and random amplified polymorphic DNA, in order to establish the epidemiological relatedness, genetic divergence and strain circulation within and between the bordering countries. Using a set of five digoxigenin-labeled oligonucleotides and BstEII digestion, 34 ribotypes were identified. The strains isolated in the epidemic areas (Russia and Moldova) were very closely related but different from those isolated in Romania. C1 and C5 were the main ribotypes identified in these areas. Neither ribotype was found in Romania, where the main circulating types were C3 and C7. Field inversion gel electrophoresis was more discriminative than ribotyping and revealed 54 macrorestriction profiles after SfiI restriction. Both methods showed a significant homogeneity of the strains from epidemic areas and a large diversity among the Romanian strains. Random amplification was useful as an identification method for the epidemic strains, but not for the Romanian ones which displayed a large number of amplification profiles. The phenotypic methods associated with molecular typing techniques enabled distinguishing between strains, detecting the epidemic clone, and sustaining the absence of transmission across borders.

A collection of 89 Vibrio cholerae O1 strains, isolated in Romania between 1977 and 1994, and 6 strains from the Republic of Moldavia, was characterized by ribotyping, toxin gene restriction pattern (toxinogenotype) and distribution of cholera toxin gene (ctx), accessory toxin gene (ace) and zonula occludens toxin gene (zot). After Bg/I endonuclease restriction of chromosomal DNA, a total of 18 ribotypes and 21 toxinogenotypes were distinguished. Deletions in the core region of the toxin gene cassette were found in 20% of strains; however, with the exception of one strain, all the isolates contained the ctx gene. Used in association, the three methods of molecular typing provided an accurate characterization of V. cholerae O1 isolates.

Six hundred and twenty-four Vibrio cholerae O1 strains, 623 serotype Ogawa and one serotype Inaba, isolated in Romania between 1977-95 were tested to detect all changing traits concerning serogroup, serotype, biotype, phage type and resistotype patterns and subsequently, the possible epidemiological relationship among these strains. Biotyping revealed one classical, 580 eltor strains and 43 intermediary variants. When tested with Mukerjee phages, 546 (87%) strains were sensitive and 78 (13%) resistant. One phage type (M4) dominated during 1977-90, two phage types (M4 and M5) exhibited the same high frequencies during 1991, a diversity of types occurred during 1993-4 whereas in 1995, two phage types (M4 and M5) showed similar distributions again. Five patterns of drug susceptibility were successively described during 1977-95. The most prominent changes in Vibrio cholerae O1 strains were noticed during 1993-4: the highest number of non-typable strains and intermediary variants, the widest spectrum of phage types and of multidrug resistance. In 1995, the strains reverted to the previous typable forms but a new drug resistance pattern was noticed.

The presence of gene encoding erythrogenic toxin type A (spe A) was determined by the polymerase chain reaction (PCR) to target specific sequences in 72 strains of Streptococcus pyogenes representative T type strains, which were associated with scarlet fever, impetigo, tonsillitis, isolated between the years 1980-1982 and in 1995 by carriers. Isolates showed statistically significant differences in the presence of spe A. With scarlet fever the strains had a 22.22% association, with impetigo had a 8.33% association. With tonsillitis' and with carriers had a low association, 5.55% and 6.9% respectively. The analysis of the data indicated that strains with certain T type surface antigens showed a higher (such as T-1, T-2, T-5) or lower (such as T-4, T-13, T-27) tendency to contain the spe A gene were more likely to be associated with scarlet fever and impetigo than with other types of diseases.

In the preantibiotic era, many people died of bacterial infections caused by such pathogens as Staphylococcus aureus and Streptococcus pyogenes, Streptococcus pneumoniae and Mycobacterium tuberculosis. Antibiotics have reduced the mortality from infectious diseases but not the prevalence of these diseases. It was not long after the clinical introduction of the first antibiotics in the 1950s that the first reports of bacterial resistance began to appear. Use, and often abuse or misuse, of antimicrobial agents has encouraged the evolution of bacteria toward resistance, resulting often in therapeutic failure. In the beginning, new antibiotics have always appeared in plenty of time to provide new cures for diseases caused by resistant bacterial pathogens. Also, some clinically important groups of bacteria showed no signs of major increases in resistance. For example, S. pneumoniae strains remained susceptible to penicillin long after other bacteria had become resistant to it. Recent developments of bacteria resistance to antibiotics are indeed disquieting.

Of 12,930 Salmonella serotype typhimurium strains, phage typed during 1985-1988, 45.68% were "nontypable" by Anderson's set; the percent of typable strains decreased from 54.17 in 1986 to 30.54 in 1988. Of 90 phage patterns of sensitivity, 22 were currently encountered. Phage types 1, 18 and 104 were most frequent to strain of both human and non-human origin. In food generating S. typhimurium outbreaks, phage types 1 and 36 were prevalent. Except lysotypes 198 and 95, isolated from "single cases" in man only, all other phage types were common in man and animals, too. Introducing other typing methods to serotype typhimurium "nontypable" strains (by Anderson's set) was considered necessary for epidemiological purposes.