Transfer of kanamycin resistance among familial strains of Enterobacteriaceae isolated from a chronic bacterial carrier of Salmonella schottmuelleri

Escherichia coli, Enterobacter aerogenes and S. schottmuelleri were isolated from the large intestine of a bacteriocarrier. E. coli and E. aerogenes strains proved to be resistant to a number of antibiotics. Plasmids were detected in DNA preparations obtained from E. coli strains. After the hybridization of these E. coli strains with E. coli C600 5K and S. schottmuelleri at 28 degrees C the transfer of resistance to kanamycin was found to occur. From some of the transconjugates thus obtained resistance to kanamycin was transferred to E. aerogenes. This resistance was found to be controlled by the plasmid with a molecular weight exceeding 2 Md. The fact that S. schottmuelleri in the carrier's body retained their sensitivity to antibiotics can be explained by the absence of the transfer of plasmid Kmr at a temperature exceeding 28 degrees C and by the existence of the infective agent in an ecological niche other than that of E. coli.     

A comparative analysis of the Salmonella typhi strains isolated from patients and bacterial carriers

The comparative analysis of 133 S. typhi clinical strains isolated from patients and carriers in Dnepropetrovsk Province in 1978-1987 was carried out. As shown by this analysis, 10 Vi phage types were represented in the set of strains under study, phage types A and F1 being the most numerous ones. Phage type F1 occurred less frequently among the strains isolated from carriers. 31.1% of the strains were found to contain plasmids with different molecular weight ranging from 96 to 0.5 MD. The occurrence of plasmid-containing strains remained at the same level during the whole period under study. Low-molecular plasmids occurred more frequently in the strains isolated from carriers. The minimal suppressive concentrations of a number of antibiotics, such as penicillin, ampicillin, monomycin, chloramphenicol, tetracycline, rifampicin and streptomycin, were determined. 7% of the strains were resistant to penicillin, 9% to monomycin, 15%--to tetracycline and 2.6% to chloramphenicol. The correlation between penicillin and monomycin resistance of the strains and the presence of the plasmid with a molecular weight of 60 MD in these strains was established. All strains were shown to be highly variable in the degree of their virulence: from 10(2) to 10(8). The strains isolated from patients possessed greater virulence.     

Resistance to antibacterial drugs of Enterobacteriaceae isolated from healthy children and from those with Salmonella infections

A total of 2329 Enterobacteriaceae strains in bacterial associations isolated from healthy children and children with salmonellosis were tested for their resistance to antimicrobial drugs. It was shown that the aerobic microbial associations isolated from the healthy children contained higher numbers of strains sensitive or resistant to 1-3 antibiotics while the microbial associations from the children patients with salmonellosis treated with antibiotics contained higher numbers of strains resistant to 6-8 antibiotics. Resistance of the aerobic bacterial associations was mainly defined by resistance of E. coli and K. pneumoniae. The feces of the healthy children never treated with antimicrobial drugs contained strains resistant to them. The use of the antibiotics in the treatment led to increasing numbers of the resistant bacteria and changing species composition of the bacterial associations.     

Characteristics of lipopolysaccharides ofSalmonella typhi isolated from carriers and patients suffering from typhoid fever

Lipopolysaccharides (LPS) ofSalmonella typhi strains, isolated from carriers and patients suffering from typhoid fever, were characterised according to their biochemical properties, morphological structure and degree of aggregation of complexes. All preparations of LPS, regardless of their origin, were morphologically heterogeneous. Free electrophoresis and immunoelectrophoresis demonstrated that LPS preparations were composed of components possessing different mobilities in electric fields. LPS of bacterial strains isolated from both carriers and patients, split upon reaction in immunoelectrophoresis with specific antiserum 73, rabbit antiserum toSalmonella typhi Vi Bhatnagar and 0–901 split into anodic and cathodio fractions. The anodic fraction reacted similarly as Vi antigen. LPS fromSalmonella typhi Ty-2 yielded only the cathodic fraction, typical for O antigen. LPS from strains whioh were passaged twice in nutritional medium possessed identical properties as LPS from fresh cultures ofSalmonella typhi. Electron microscopy revealed that LPS appears as long bands, rods, ellipsoid forms and amorphous material. Contrary to amorphous material, the bands, rods and ellipsoid forms possessed three-layer structure.     

Strains of genus Salmonella isolated from extraintestinal infections

Every year in Poland from tens to more than hundred bacteriologically verified extraintestinal infections caused by Salmonella species have been registered. These unusually located infections have substantially heavy course and in many cases hospitalisation and antibiotic therapy have to be involved. Cases of extraintestinal infections with these Gram-negative rods, which were described in the literature, concerned: pneumonias, lung abscesses and thoracic empyemas, and infections of: blood, bones and joints, wounds, fistulas and urinary tract. The aim of this study was to set extraintestinal Salmonella infections and to analyze a susceptibility of isolated strains to antimicrobial agents. Between 01.07.2002 and 31.12.2004 (30 months) 13 strains of Salmonella genus have been isolated, including 11 S. enteritidis and 2 S. Hadar. In general, with one exception, isolated strains were susceptible to tested antibiotics/chemotherapeutics. ESBL - positive strains were not detected. The tendency of Salmonella strains to cause extraintestinal infections has been noticed. The problem is still escalating, especially in group of patients chronically treated, with immunodeficiency and immunosuppression, after complicated medical procedures, also in the group of small children and aged persons. Therefore, it is necessary to evaluate a susceptibility to antibiotics/chemotherapeutics of every strain from confirmed case of Salmonella extraintestinal infection and it is important to apply a guided therapy.     

Genotyping of Staphylococcus aureus strains isolated from healthy persistent carriers

The paper presents results on the relatedness of Staphylococcus aureus strains colonizing the upper respiratory tract isolated from healthy persistent carriers. Genotyping was carried out using two methods—multiple-locus variable-number tandem-repeat fingerprinting (MLVF) and pulsed-field gel electrophoresis (PFGE). By comparison of the results obtained by both methods, good correlations between MLVF and PFGE genotyping of strains isolated from the asymptomatic carriers were observed. Further studies are needed to evaluate methods useful for genotyping of S. aureus strains circulating in the community.     

Comparison of frequency and susceptibility to antimicrobials of bacterial strains of the family Enterobacteriaceae isolated from patients hospitalised in intensive care units

The aim of the study was estimation of frequency and susceptibility to antimicrobial agents of gram-negative rods isolated from clinical specimens obtained from patients requiring intensive care, with emphasis on profile of the unit. The analysis comprised strains of gram-negative rods isolated from patients of two intensive care units (ICUs) of a tertiary care hospital (1200 beds). Identification of cultured isolates was done using automated VITEK and API systems (bioMerieux, France). Susceptibility to antimicrobial agents was tested by a disk-diffusion method according to the NCCLS recommendations. In total the analysis comprised 722 strains of gram-negative rods. In blood cultures predominated strains of Enterobacter spp. (42.5%) and Klebsiella pneumoniae (37.5%). In cultures of clinical specimens other than blood 41.6% comprised strains of Klebsiella pneumoniae, 14.8% Escherichia coli and 14.4% Proteus mirabilis. Frequency of multi-drug resistant strains of bacteria of the family Enterobacteriaceae was much higher among blood isolates in comparison to strains cultured from other clinical specimens. There was a relatively high percentage of strains of Enterobacteriaceae susceptible to piperacillin and tazobactam (69.0%) and ceftazidime (54.6%). Conclusions: 1. All strains were susceptible to carbapenems. 2. There was a relatively high percentage of strains of gram-negative rods susceptible to piperacillin/tazobactam and ceftazidime. 3. Bacteria isolated from blood cultures were characterised by a much higher percentage of resistant strains in comparison to other specimens. 4. Longer stay in ICU promoted selection of strains resistant to antimicrobials.     

Typing of Streptococcus group A isolated from patients and healthy persons

The typing of 80% of 381 streptococcal strains, group A, under study was accomplished with a set of diagnostic anti-T sera obtained from the Sevak Institute (Czechoslovakia). None of the T-types could be related with certainty to the localization of the infective agent in the human body (the pharynx, the skin). Different T-types were shown to circulate in definite regions of the USSR. To enhance the differentiating capacity of T-typing, the enzymatic (lipoproteinase and NADase) activity of the strains was determined, thus permitting the subdivision of the T-types into still smaller groups. The typing of OF+ strains of unknown M-specificity could be carried out by means of the blood sera of healthy persons, containing antibodies to streptococcal lipoproteinase. The conclusion on the expediency of using the determination of lipoproteinase and NADase as an additional marker in the typing of group A streptococci was made.     

Resistance to antibiotics of Lactobacillus isolated from the intestines of healthy persons

Lactobacilli constitute a significant part of the microbial population in the gastrointestinal tract of humans and animals. Sensitivity of intestinal lactobacilli to 11 chemotherapeutic drugs was tested with the method of serial dilutions in the solid medium MRS under aerobic and anaerobic conditions. Criteria for dividing the organisms into sensitive and resistant ones with respect to the drugs are proposed. Prevalence of lactobacilli polyresistant strains in the intestine contents of healthy persons at the age of 25 to 50 years being in prolonged constant contact with antibiotics was shown. On the whole 77 various combinations of the antibiotic resistance markers were detected in 141 tested strains. The most frequent were isolated simultaneously resistant to 6 or 7 antibiotics. Different levels of the antibiotic resistance in the strains tested under the aerobic and anaerobic conditions were observed.     

Detection of microbial variants of Salmonella typhi in the bone marrow of typhoid patients and carriers

The immunofluorescence test with the use of antisera to S. typhi and its L-forms permits the detection of the infective agent in bone marrow smears. This diagnostic method is particularly important in cases of carrier state in the latent phase and in differential diagnosis. As revealed in this study, the microbial variants of S. typhi, reacting with antiserum to its L-forms, are present in the bone marrow of carriers. They are localized, as a rule, on the membranes of lymphoid and erythroid cells, which probably leads to the formation of rosettes.     

Microbial biocenosis of the nasal mucosa in healthy persons and in Staphylococcus carriers

The normal microflora of the nasal mucosa in man is differentiated into main, complementary and casual microflora, taking into account its isolation rate and characteristics of microbial contamination. The main microflora of adults, in contrast to children, is represented, in addition to coagulaso-negative (CN) staphylococci, by bacteria of the genus Corynebacterium. In staphylococcal carrier state a decrease in the isolation rate and the amount of bacteria belonging to the main and complementary microflora (CN staphylococci, Micrococcus, Streptococcus, Bacillus) was observed. Moreover, in carriers the weakening of the degree of association between CN staphylococci, Micrococcus, Corynebacterium, Streptococcus in symbiotic pairs was noted. In the absence of S. aureus carrier state the main and complementary microflora was characterized by the combination of the factors of antagonism and persistence, while in carrier state the complex of colonization factors was defective in the main microflora and well pronounced in coagulase-positive staphylococcal strains and enterobacteria.     

Comparative Virulotyping of Salmonella typhi and Salmonella enteritidis

Members of Salmonella enterica are important foodborne pathogens of significant public health concern worldwide. This study aimed to determine a range of virulence genes among typhoidal (S. typhi) and non-typhoidal (S. enteritidis) strains isolated from different geographical regions and different years. A total of 87 S. typhi and 94 S. enteritidis strains were tested for presence of 22 virulence genes by employing multiplex PCR and the genetic relatedness of these strains was further characterized by REP-PCR. In S. typhi, invA, prgH, sifA, spiC, sopB, iroN, sitC, misL, pipD, cdtB, and orfL were present in all the strains, while sopE, agfC, agfA, sefC, mgtC, and sefD were present in 98.8, 97.7, 90.8, 87.4, 87.4 and 17.2 %, of the strains, respectively. No lpfA, lpfC, pefA, spvB, or spvC was detected. Meanwhile, in S. enteritidis, 15 genes, agfA, agfC, invA, lpfA, lpfC, sefD, prgH, spiC, sopB, sopE, iroN, sitC, misL, pipD, and orfL were found in all S. enteritidis strains 100 %, followed by sifA and spvC 98.9 %, pefA, spvB and mgtC 97.8 %, and sefC 90.4 %. cdtB was absent from all S. enteritidis strains tested. REP-PCR subtyped S. typhi strains into 18 REP-types and concurred with the virulotyping results in grouping the strains, while in S. enteritidis, REP-PCR subtyped the strains into eight profiles and they were poorly distinguishable between human and animal origins. The study showed that S. typhi and S. enteritidis contain a range of virulence factors associated with pathogenesis. Virulotyping is a rapid screening method to identify and profile virulence genes in Salmonella strains, and improve an understanding of potential risk for human and animal infections.