Virulence and resistance markers in clinical and environmental Aeromonas strains isolated in Romania

The virulence and resistance (R) features of 37 Aeromonas strains from diarrheal cases and 150 from the aquatic environment (isolated during cold and warm season) were tested at different incubation temperatures (4 degrees C, 28 degrees C and 37 degrees C). When incubated at 4 degrees C temperature, the Aeromonasstrains isolated during the cold season expressed the highest number of virulence factors by comparison with the strains isolated during warm season and from diarrhoeal cases, the virulence spectrum increasing simultaneously with the incubation temperature (i.e. 28 degrees C and 37 degrees C) for all strains. Mucinase was the unique virulence factor constantly present in all three categories of strains at all three incubation temperatures. The aquatic as well as clinical strains exhibited similar R levels to ampicillin and colistin, while for the other tested antibiotics, the aquatic strains generally proved higher R levels than clinical strains, excepting cephtazidime. Plasmids of molecular weights ranging between 1904-21226 bp, were isolated in 36.5% of Aeromonas strains, some of them being correlated with specific R patterns. The large virulence spectrum correlated with high R in Aeromonas strains isolated from the aquatic medium is pleading for the significant role of these bacteria in the pathogenic potential of the natural reservoir possibly implicated in human pathology.     

Properties of Serratia marcescens strains isolated in septic diseases of newborn infants

As the result of the study of blood and liquor samples from 120 newborns, Serratia marcescens was isolated in 21 cases (17.5 %). 8 strains were isolated from the environment of these patients. Almost all strains isolated from both the patients and the environment (with the exception of one environmental strain) belonged to serotype 04. The isolated S. marcescens strains were resistant to penicillin, ampicillin, streptomycin, kanamycin, oxacillin, methicillin, ceporin and moderately sensitive to polymixin. 2 strains from the environment and 9 strains from the patients were mildly sensitive to gentamicin. In one hospital all isolated strains were found to have 2 transmissive R plasmids with the molecular weight 40 and 60 megadaltons. The presence of R plasmids with the same molecular weight in all S. marcescens strains isolated in this hospital, as well as their serological identity, suggest that in all patients infection originated from a common source.     

Antagonistic action of Pseudomonas aeruginosa against Staphylococci, coliform bacilli and various types of Proteus

Antagonistic activity of 2 fresh isolates and 3 collection strains of Pseudomonas aeruginosa against 177 microbial strains was determined with the method of late antagonism. Among the microbial strains there were 56 staphylococcal strains isolated from patents and carriers. 38 nontypable colon bacilli isolated from healthy persons, 59 enteropathogenic colon bacilli of various serogroups, 12 strains of Proteus and 12 colon bacilli, carriers of multiple drug resistance factors (R factors). All the cultures were sensitive to the antagonistic action of 5 or at least 3 strains of Pseudomonas used in the study. The most active antagonists were the fresh isolates of Pseudomonas as compared to the collection strains. Among the staphylococci S. aureus proved to be the most resistant to the antagonistic action of Pseudomonas as compared to S. epidermidis, the same as the strains isolated from carriers as compared to the strains isolated from patients. As for the enteric bacilli the most resistant were the strains of Proteus. Acquiring of transmissive R factors by the colon bacilli markedly increased their sensitivity to the antagonistic action of Pseudomonas.     

Continous alert for rickettsiosis in Sicily: molecular characterization of Rickettsia sp. obtained from ticks and human beings (1986-2001)

Several strains of Rickettsia sp. were isolated from patients in western Sicily with MSF (Mediterranean Spotted Fever) as well as ticks. Strains isolated were examined by PCR and identified as belonging to R. conorii sp. Importantly a strain of Israeli Spotted Fever Rickettsiae, obtained from a tick, was also identified. Our data prove that strains other than the classical R. conorii also circulate in Sicily.     

Drug Resistance of Enteric Bacteria

Drug resistance of 3,000 Shigella strains isolated in 1965 were investigated. These strains originated from 10 City Hospitals and 4 Prefectural Health Centers, which are located in different parts of Japan. One hundred and seventy strains which were resistant to 4 drugs, chloramphenicol (CM), tetracycline (TC), dihydrostreptomycin (SM), and sulfanilamide (SA), were selected at random from these stock cultures in this laboratory and the distribution of R factors in these isolates was examined. It was found that the strains all harbored R factors which were capable of transferring drug resistance by usual conjugal process. Among the strains carrying R factors, 85 per cent harbored a single type of R factor and 15 per cent carried two types of R factor in a cell. The latter is called the hetero-R state. Among the strains in the hetero-R state, isolation of strains harboring both R (SM.SA) and R (TC.CM.SM.SA) factors was most frequent. It was found that 25 R (SM.SA) factors isolated from strains in hetero-R had the genetic determinant iR^?, while most of the R (TC.CM.SM.SA) factors isolated from natural sources were iR⁺. When two types of R factor, R (SM.SA) and R (TC.CM.SM.SA) derived from the same host cells, were brought together in a host cell by superinfection with both factors, they were found to exist stably in a host bacterium. These results confirmed the stable existence of both factors in Shigella strains isolated from dysenteric patients.     

The Incidence of R Factors in Bordetella bronchiseptica Isolated from Pigs

Bordetella bronchiseptica strains isolated from the nasal cavities of young pigs in Japan from 1969 to 1972 were surveyed for drug resistance and distribution of R factors. Of 304 strains examined, 71 (23%) were resistant to either one or more of following three drugs, streptomycin (SM), sulfadimethoxine (SA), and aminobenzyl penicillin (APC). Triple (SM.SA.APC)-resistance was most frequent among these resistant strains. Strains of double (SM. SA)- or single (SM)- and (SA)-resistance were also isolated, but were very few in numbers. Of the 71 drug-resistant strains, 61 (86%) were found to carry R factors which were capable of conjugal transfer. All of these R factors had the triple (SM.SA.APC)-resistant markers and were identified as fi^– (no fertility inhibition) type. The (SM.SA.APC)-resistant strains carrying R factors had been isolated from pigs reared on various farms in different districts, and consequently the prevalence of B. bronchiseptica strains carrying R factors was considered to be relatively wide-spread in young pigs.     

多聚酶链反应技术鉴别肾综合征出血热病毒血清型的初步研究

肾综合征出血热(HFRS)为一组抗原性密切相关的布尼亚科汉坦病毒引起的急性传染病。在我国存在至少两种临床表现、动物宿主及流行特征截然不同的血清型别,即血清Ⅰ型(汉坦型)和血清Ⅱ型(汉城型)。这两型病毒间的血清学定型已有报道。近年来,除啮齿类动物外,从临床病人以及非啮齿类动物体内也分离到了HFRS病毒。同时出现两类型别毒株共存,以及从家鼠体内分离到野鼠型毒株或从野鼠体内分离到家鼠型毒株的复杂情形。为此,准确检定并鉴别不同来源毒株型别,将为深入了解其病原学、流行病学以及制定疫苗生产策略提供重要信息。     

R plasmids among Gram-negative bacteria with multiple drug resistance isolated in a general hospital.

The incidence of conjugative R plasmids in multiple drug-resistant strains of gram-negative bacteria isolated in 1973 from patients in a 700-bed general hospital in Tokyo and some properties of the R plasmids isolated are described. Conjugative R plasmids were found in 52 of the 96 strains (54%), from which 74 R plasmids were demonstrated. It is remarkable that the isolation frequency of R plasmids mediating quadruple- or five-drug resistance was rather low, and the complete pattern of multiple resistance of the original isolates was only rarely transferred by conjugation. These results revealed the existing state of the distribution of R plasmids among hospital strains with multiple drug-resistance.     

Genome sequences of two plant growth-promoting fluorescent Pseudomonas strains, R62 and R81

Plant growth-promoting rhizobacterial (PGPR) strains R62 and R81 have previously been isolated and characterized as part of the Indo-Swiss Collaboration in Biotechnology. Here we present the draft genome sequences of these two PGPR strains, with the aim of unraveling the mechanisms behind their ability to promote wheat growth.     

Genetic transfer of Pseudomonas aeruginosa R factors to plant pathogenic Erwinia species.

The R factors RP1, R68 and R91 were freely transmissible to and from Pseudomonas aeruginosa, Salmonella typhimurium, and various plant pathogenic Erwinia spp. The antibiotic resistance spectrum of R+ Erwinia recipients was similar to those of other bacteria harboring these R factors, but maximum resistance levels differed with each recipient. The sponstaneous elimination of these factors from the Erwinia strains and the ability to transfer multiple antibiotic resistance suggest that these exist as plasmids in these hosts. Several, but not all, RP1-carrying Erwinia strains were sensitive to the RP1 specific phage PRR1. The R factor R18-1 was also transferred from P. aeruginosa to Erwinia spp. R18-1 was unstable in all Erwinia strains. Stable strains were isolated in which R18-1 could not be eliminated by sodium dodecyl sulfate and could not be transferred to other strains.     

Large plasmids of fast-growing rhizobia: homology studies and location of structural nitrogen fixation (nif) genes.

A single large plasmid was isolated from multiplasmid-harboring strains Rhizobium leguminosarum 1001 and R. trifolii 5. These single plasmids, as well as the largest plasmid detectable in R. phaseoli 3622, hybridized with part of the nif structural genes of Klebsiella pneumoniae. In contrast, the plasmids of R. meliloti strains V7 and L5-30 did not show hybridization with the nif genes of K. pneumoniae, indicating that these genes might be located either on the chromosome or on a much larger plasmid which as yet has not been isolated. Studies of the homology between plasmids of fast-growing Rhizobium species showed that a specific deoxyribonucleic acid sequence, which carries the structural genes for nitrogenase, is highly conserved on a plasmid in R. leguminosarum, R. trifolii, and R. phaseoli. Furthermore, it was found that this type of plasmid in the different species shares extensive deoxyribonucleic acid homology, suggesting that strains in the R. leguminosarum cluster have preserved a nif plasmid.     

Drug Resistance of Enteric Bacteria XIII. Distribution of R Factors in Escherichia coli Strains Isolated from Livestock

Escherichia coli strains isolated from 151 swine and 108 fowl, which were kept at the Animal Health Center, Maebashi, Japan, were surveyed for drug resistance and distribution of R factors. All of the swine and 38% of the fowl excreted E. coli strains resistant to tetracycline, chloramphenicol, streptomycin, and sulfanilamide, or certain combinations thereof. Among 278 resistant cultures isolated from swine, 13% were found to be resistant to one antibiotic, whereas 87% were resistant to more than one antibiotic. Among these resistant strains, 40% carried R factors which were transferable by the usual conjugal process. The resistance patterns of these R factors included 36% which were singly resistant and 64% which were multiply resistant. Among 54 resistant cultures isolated from fowl, 24% were singly resistant and 76% were multiply resistant. Of the resistant strains from fowl, 22% carried R factors. The resistance patterns of R factors included 50% of the singly resistant type and 50% which were multiply resistant. In spite of feeding with dairy products containing only tetracycline, a high incidence of multiple resistance was observed in the E. coli strains and the R factors isolated from these animals.     

Relatedness Among Rhizobium and Agrobacterium Species Determined by Three Methods of Nucleic Acid Hybridization

Deoxyribonucleic acid (DNA) was isolated from 20 strains of Rhizobium and Agrobacterium and from one strain of Serratia marcescens; the guanine plus cytosine content of each DNA sample was determined by thermal denaturation. Radioactive DNA was isolated from three reference strains following the uptake of [2-(14)C]thymidine in the presence of deoxyadenosine. Ribonucleic acid (RNA) polymerase was used to synthesize radioactive RNA on DNA templates from the three reference strains. Radioactive DNA and RNA from the three reference strains were each hybridized with filter-bound DNA from all of the 21 test strains in 6 x SSC (standard saline citrate) and 50% formamide at 43 C for 40 hr. DNA/DNA relatedness was also determined by spectrophotometric measurement of the rates of association of single-stranded DNA. The order of relatedness between strains was similar by each method. Overall standard deviations for the DNA/DNA and DNA/RNA membrane filter techniques were +/-0.87 and +/-1.03%, respectively; that for the spectrophotometric technique was +/-4.11%. The DNA/DNA membrane technique gave higher absolute values of hybridization than did the DNA/RNA technique. R. leguminosarum and R. trifolii could not be distinguished from each other by these techniques. These results also indicated close relationships between R. lupini and R. japonicum, and (with less certainty) between R. meliloti and R. phaseoli. Of all the rhizobia tested against the A. tumefaciens 371 reference strain, the R. japonicum strains were the most unrelated. The three Agrobacterium strains used were as related to the R. lupini and R. leguminosarum references as were several rhizobium strains.     

Drug Resistance and R Plasmids in Vibrio anguillarum Isolated in Cultured Ayu (Plecoglossus altivelis)

Two hundred twenty-six strains of Vibrio anguillarum collected from cultured ayu (Plecoglossus altivelis) between 1978 and 1980 were studied for their sensitivities to 10 chemotherapeutics. In order to determine whether the drug-resistant strains possessed transferable R plasmids, they were conjugated with Escherichia coli. Almost all the strains isolated during the 3 years showed resistance to nalidixic acid (NA) and/or furazolidone (NF). NA and NF resistance were not transferred to Escherichia coli from any of the strains. Chloramphenicol-resistant strains were isolated in every year and almost all of them carried transferable R plasmids. Only one strain with tetracycline resistance was found among the strains tested. Strains resistant to sulfonamides, streptomycin, ampicillin (ABP), and trimethoprim (TMP) increased rapidly in 1980, and a large number of them carried transferable R plasmids. Transferable R plasmids encoded with resistance to ABP and TMP were detected for the first time in V. anguillarum strains. The R plasmids detected in the strains isolated in 1980 were classified into incompatibility groups E, A, and an untypable group. The R plasmid DNAs were cleaved by EcoRI to yield 11 to 13 fragments. The estimated molecular weights of the R plasmids from the five strains ranged from 97 to 104 M daltons.     

Carotenoids of purple nonsulfur bacteria

Summary The carotenoid composition of some recently isolated new species of purple nonsulfur bacteria was investigated. All of the investigated R. tenue and R. purpureus strains and three of the R. acidophila strains synthesize the components of the rhodopinal series. It was shown that spirilloxanthin was present in all strains of R. acidophila; in three R. acidophila strains a very small amount of -carotene was found. Large amounts of the glucosides of rhodopin and rhodopinal were isolated from the cells of seven R. acidophila strains. Some taxonomic aspects are discussed.     

Strain Identification in Rhizobium Using Intrinsic Antibiotic Resistance

The variation in intrinsic resistance to low levels of eight antibiotics was used as an identifying characteristic for 26 Rhizobium leguminosarum strains. The pattern of antibiotic resistance of each strain was a stable property by which rhizobia isolated from root nodules of inoculated Pisum sativum could be recognized. The antibiotic tests for strain identification with R. leguminosarum were applied to R. phaseoli . It was necessary to include reference cultures in tests with this species, as the tests most suitable for the R. leguminosarum strains showed some variability with R. phaseoli .     

Specific Distribution of R Factors in Serratia marcescens Strains Isolated from Hospital Infections

Serratia marcescens strains from three hospitals in the city of New York were tested for antibiotic susceptibility patterns and the presence of transmissible antibiotic resistance factors. There appears to be a pattern characteristic for each hospital with regard to the sensitivity to nalidixic acid, tetracycline, chloramphenicol, and sulfonamides, whereas the resistance to ampicillin, cephalothin, and streptomycin is similar in the strains isolated from all three hospitals. In one hospital, a single type of R factor was found which transfers resistance to streptomycin, kanamycin, ampicillin, and sulfonamides, whereas strains isolated from a second hospital transfer only ampicillin resistance. No R factors could be detected in multiply resistant Serratia strains isolated in a third hospital. The presence of a single type of R factor probably reflects the relative ecological isolation of S. marcescens and could be useful for epidemiological studies of hospital infections with Serratia.     

Drug resistance of Escherichia coli isolated in Nepal.

We collected Escherichia coli strains from 59 Nepalese porters in 1971 and surveyed for their drug resistance. Drug-resistant E. coli strains were isolated from four porters. (TC. CM. SM. SA. APC.)-resistant strains were isolated from two porters and SA- or APC-resistant strains were isolated from each of the others. The R factors were demonstrated from the multiple-resistant E. coli strains.     

Smouldering epidemic of Yersinia pseudotuberculosis in barn rats.

Yersinia pseudotuberculosis was isolated from 8 (8 Rattus norvegicus) of 270 (259 R. norvegicus and 11 R. rattus) rats examined. Seasonal variation was not found in the incidence of isolations. The isolation occurred almost equally in both young and old rats. The isolated strains were determined as serovar IB in one rat, and serovar IVA in seven rats. The strains were isolated from the contents of the intestinal tract (the duodenum, jejunum, ileum, cecum, colon, and rectum), the spleen, liver and mesenteric lymph nodes; they were not detected in the kidneys. Agglutinin titer in the eight rats was no more than 32.     

Genotypic and phenotypic characterization of rhizobia that nodulate snap bean (Phaseolus vulgaris L.) in Egyptian soils

Snap bean fields in 12 of the 25 governorates of Egypt were surveyed to determine the distribution and taxonomy of snap bean-nodulating rhizobia. Nodulation rates in the field were very low, indicating that Egyptian soils do not have sufficient numbers of snap bean-compatible Rhizobium spp. A total of 87 rhizobial isolates were assayed on the most commonly grown cultivars in order to identify the most effective strains. The five most effective isolates (R11, R13, R28, R49 and R52) were fast-growing and utilized a wide range of carbon and nitrogen sources. A phylogenetic assignment of these strains by analysis of the 16S ribosomal RNA gene suggested that all fell within the Rhizobium etli–Rhizobium leguminosarum group. Strains R11, R49 and R52 all clustered with other identified R. etli strains, while strains R13 and R28 were more distinct. The distinctness of R13 and R28 was supported by physiological characteristics, such as their ability to utilize citrate, erythritol, dulcitol and lactate. Strains R13 and R28 also yielded the highest plant nitrogen content of all isolates.The highly effective strains isolated in this study, in particular strains R13 and R28, are promising candidates for improving crop yields. The data also suggested that these two strains represented a novel sub-group within the R. etli–R. leguminosarum group. As snap bean is a crop of great economic value to Egypt, the identification of highly effective rhizobial strains adapted to Egyptian soils, such as strains R13 and R28, is of great interest.