Drug resistance of the causative agent of Grigo'rev-Shiga dysentery (Shigella dysenteriae 1)isolated in the USSR

Forty strains of S. dysenteriae 1 isolated in the USSR within 1986-1988 were tested for their resistance to 11 antibacterial drugs. It was shown that 92.5-97.5 per cent of the isolates were resistant to chloramphenicol (Cm) and tetracycline (Tc), 22.5 per cent to streptomycin (Sm), 17.5 per cent to nalidixic acid (Nal) and 10 per cent to ampicillin (Ap) and polymyxin (Pm). Resistance to Cm Tc (51.4 per cent) and Cm Tc Nal (13.5 per cent) represented the predominating phenotype. 35 per cent of the strains carried conjugative R plasmids. In the majority of the cases, the determinants of resistance to Cm and Tc were transferred, which must define the high frequency of the strains resistant to Cm and Tc. All the tested strains were sensitive to gentamicin, neomycin, rifampicin, cefamezin and ciprofloxacin. Since the strains of S. dysenteriae 1 proved to be highly sensitive to the tested drugs it appeared possible to consider them as the drugs of choice in etiotropic therapy of patients with dysentery caused by the pathogens of the Grigoryev-Shiga group.     

Molecular characterization of antibiotic resistance in clinical Salmonella typhi isolated in Ghana

Fifty-eight clinical Salmonella typhi strains isolated from patients suspected of suffering from typhoid fever were obtained at the Korle-Bu Teaching Hospital and the Noguchi Memorial Institute for Medical Research, both located in Ghana, Africa. Each isolate was examined for susceptibility to ampicillin, chloramphenicol, streptomycin, tetracycline, and trimethoprim/sulfamethoxazole by the disk diffusion assay. Five of the isolates were resistant to all five antibiotics while 10 isolates were resistant to ampicillin, chloramphenicol, and trimethoprim/sulfamethoxazole, which are considered 'first line' antibiotics in the treatment of typhoid fever. Thirty-four isolates were resistant to at least one of the antibiotics tested and 62% of these isolates possessed conjugable plasmids belonging to incompatibility group IncHI. Ninety percent of the conjugable plasmids conferred a multiple drug-resistant phenotype on the strains harboring them. Additionally, 14 strains contained plasmids that were transformable and six of them encoded multiple drug resistance. Our findings indicate that multiple drug resistance to the 'first line' antibiotics in S. typhi may be more prevalent in Africa than previously thought.     

Antibiotic resistance and its transmissibility in strains of opportunistic enterobacteria

Sensitivity of 39 opportunistic Enterobacteria strains was studied with respect to tetracycline, kanamycin, ampicillin, levomycetin, streptomycin and nevigramon. The strains were isolated from children with acute intestinal infections of obscure etiology. 38 isolates were resistant to one or more drugs. The highest number of the strains was resistant to kanamycin, ampicillin and levomycetin, i.e. 81.5, 84.2 and 84.2 per cent of the cultures respectively. Nevigramon proved to be the most effective in vitro (76.4 per cent of the sensitive strains). The ability of the strains to transfer the antibiotic resistance markers on conjugation was tested. Transmission of R plasmids was shown in 75 per cent of the isolates.     

Antibiotic resistance study of clinical strains of Pseudomonas aeruginosa]

The study of 40 clinical strains of Ps. aeruginosa isolated from the wound surfaces of the patients showed that all the isolates were resistant to one or several antibiotics. The number of the strains resistant to 5, 4, 3, 2 or 1 drug was 5, 22.5, 25. 30 or 17.5 per cent respectively. Fifteen strains carried resistance plasmids capable of conjugative transfer. Eleven out of 21 plasmids controlled resistance to chloramphenicol, 7 plasmids controlled resistance to streptomycin and sulfanylamides, 1 plasmid controlled resistance to streptomycin and chloramphenicol. The presence of two types of the plasmids controlling resistance to chloramphenicol and streptomycin + sulfanylamides respectively was found. All the plasmids proved to be capable of conjugative transfer between the strains of Ps. aeruginosa ML (PAO). The frequency of the plasmid conjugative transfer in such crosses ranged from 10(-6) to 10(-3). Most of the plasmids belonged to the incompatibility groups P-2 and P-7. One plasmid belonged to the incompatibility group P-5. It should be noted that about a half of the plasmids (11 out of 21) belonged to the incompatibility group P-7 which up to the present time was conditional, since was represented by a single plasmid Rms 148.     

Drug resistance of opportunistic enterobacteria isolated from various sources]

Resistance of 159 strains of opportunistic enterobacteria to 9 antibacterial drugs was studied. The strains were isolated from man and cattle. It was shown that the overwhelming majority of the isolates (93 per cent) were polyresistant irrespective of the genus. There was a high frequency of the strains resistant to the widely used antibiotics such as chloramphenicol (73 per cent), ampicillin (73.6 per cent) and rifampicin (95.6 per cent) and sulfanilamides (99.3 per cent). Gentamicin and nalidixic acid proved to be the most active against the cultures: 11.9 and 10 per cent of the resistant strains, respectively. The strains of enterobacteria isolated from different sources had a sensitivity to the antibiotics. Multiple antibiotic resistance to at least 5 drugs, variability of the spectra and high resistance were more characteristic of the isolates from the animals. The necessity of a rational use of antibacterial drugs in veterinary is indicated.     

Escherichia coli R-factors unstable in Salmonella typhi are deleted before being segregated in this host

Although resistant Salmonella typhi strains are found in the environment, many epidemiological data indicate that most isolates are multisensitive. Plasmids are not common in S. typhi, contrasting with other enterobacteria. Since S. typhi is able to receive R plasmids from other enterobacteria, such plasmidless condition may be due to destabilization of the plasmids acquired. The segregation process of three plasmids known to behave unstably in S. typhi strains was analyzed, and evidence was obtained that the three of them lost an antibiotic-resistance determinant due to small deletions before plasmid loss occurred. Once deleted, the plasmids entered a segregation phase with particular kinetic features in each case. Selective pressure prevented plasmid deletion and segregation. Like their parental plasmids, the deleted plasmids were unstable in S. typhi but stable in Escherichia coli, suggesting that deletions imply loss of genetic information relevant for a plasmid stability mechanism operative in S. typhi, but not in E. coli.     

Level and nature of the drug resistance of Shigella flexneri]

Characteristics of antibiotic resistance of 300 strains of Shigella flexner 2a isolated from patients within 1976--1977 in the regions where these bacteria were very rare for a long period of time were studied. It was shown that most of the isolates were resistant to chloramphenicol (88.1 per cent), tetracycline (94.8 per cent), streptomycin (89.1 per cent), polymyxin M (82.4 per cent) and others. 46.5--61.6 per cent of the isolates were resistant to neomycin antibiotics. A high level of the resistance was also noted: the bactericidal effect was registered in 52.0-74.0 per cent of the cultures at a dose of 500--1000 microgram/ml. 91.4 per cent of the strains possessed multiple dug resistance, 78.8 per cent of them being simultaneously resistant to 4--7 drugs. Transmissive R-plasmids were found in 68.8 per cent of the isolates. After exposure to acridine dyes the plasmid nature of the resistance was confirmed in 72.3 per cent of the cultures. Variability of the r-determinant sets in r-plasmids was noted. Strains (64.9 per cent) carrying r-determinants Tc, Cm, Sm and Tc, Cm were more frequent. Strains with one transmissive r-determinant were usually solitary.     

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.     

Sensitivity to antibiotics and the disinfectant chloramine of Staphylococci isolated from healthy and sick persons

Five hundred and twenty seven strains of Staphylococcus aureus with massive contamination of at least 10(3) when estimated quantitatively were tested for their sensitivity to antibiotics and chloramine B. The staphylococcal strains were isolated from patients, air and stock of rooms in medical institutions, from medical personnel and healthy persons having no long-term contacts with hospital media i. e. from pregnant women and workers of confectionery plants. Among the isolates there were strains simultaneously sensitive to antibiotics and chloramine B (16.6 per cent), sensitive to antibiotics but resistant to chloramine B (5.5 per cent), resistant to antibiotics but sensitive to chloramine B (63.1 per cent) and resistant to antibiotics and chloramine B (15.3 per cent). Staphylococci resistant simultaneously to antibiotics and chloramine B were isolated from the persons of all the groups and from the air and stock of the rooms in the medical institutions. This showed the necessity of controlling sensitivity or staphylococci circulating in hospital media not only to antibiotics but also to disinfectants for providing more efficient prophylaxis of intrahospital infections.     

R-plasmids of bacteria of the genus Pseudomonas isolated from industrial sewage

A total of 132 Pseudomonas strains isolated from untreated sewage of antibiotic plants were tested. A significant number of the strains were resistant to streptomycin (77 per cent), carbenicillin (75 per cent), kanamycin (37.5 per cent) and tetracycline (23 per cent). Eighteen conjugative and 3 nonconjugative resistance plasmids were detected in 19 strains. The genes determining the resistance to streptomycin, kanamycin and tetracycline were most frequent. The frequency of the plasmid transfer between the strains of Ps. aeruginosa (PAO) varied within 10(-3)--10(-7) per donor cell. Six plasmids belonged to group Inc P-1. Four plasmids belonged to group Inc P-2, 3 plasmids to groups Inc P-3 and Inc P-5 and 1 plasmid to group Inc P-7.     

Antibiotic resistance of Lactobacillus strains]

One hundred and thirty six Lactobacillus strains isolated from poultry and 23 Lactobacillus strains isolated from long-living persons were tested for their antibiotic sensitivity. Occurrence of some type determinants of resistance to aminoglycoside antibiotics and tetracyclines in the Lactobacillus strains resistant to these antibiotics was studied. The majority of the strains from the both collections were resistant to aminoglycosides (73 and 79 per cent, respectively). The isolates from the poultry were characterized by multiple resistance. The isolates from the long-living persons were most frequently resistant to one of two antibiotics. All the tested Lactobacillus strains isolated from the long-living persons were sensitive to tetracyclines. The species composition of the isolates was different. The antibiotic-resistant strains were detected in all the species involved in the study. By hybridization of Lactobacillus colonies with the probes containing various genes of the resistance it was shown that in 14 per cent of the antibiotic-resistant strains belonging to Lactobacillus the antibiotic resistance was controlled by the genes homologous to resistance genes widely distributed in gramnegative organisms. This indicated a possible wide exchange and heterologous expression of the antibiotic resistance determinants between microorganisms of various taxonomic groups.     

Antibiotic sensitivity and pathogenetic factors of hospital strains of Pseudomonas aeruginosa isolated from patients treated in a resuscitation unit]

Strains of Pseudomonas aeruginosa were isolated from patients treated in the Centre of Thermal Affections in 1985-1989. It was shown that 72.9, 59.3, 33.8 and 54.2 per cent of the isolates were sensitive to cefotaxime, tobramycin, gentamicin and polymyxin, respectively. The study of pathogenicity factors of the isolates revealed that 83 per cent of the strains produced thermolabile enterotoxin, 79.6 per cent of the strains had adhesive activity and 71.1 per cent of the strains produced hemolysin. The study detected combinations of various pathogenicity factors. 42.3 per cent of the isolates had both adhesive and enterotoxigenic properties. Adhesiveness and hemolytic activity were shown by 13.5 per cent of the strains. 16.9 per cent of the strains produced both enterotoxin and hemolysin. Adhesive activity, enterotoxigenicity and hemolysin production were observed in 6.7 per cent of the strains. It was noted that the strains of P. aeruginosa resistant to polymyxin mainly produced enterotoxin (18.6 per cent) and those resistant to cefotaxime had adhesive activity (34.0 per cent).     

Antibiotic sensitivity and the characteristics of transmissive R plasmids in Shigella belonging to various species]

Sensitivity of 241 Shigella strains isolated from patients at various regions of the USSR in 1975--1978 was tested with respect to 14 antibiotics by the method of serial dilutions. 90.5 per cent of the isolates proved to be resistant to the antibacterial drugs and the greater part of 75.9 per cent of them had multiple resistance. The resistance of the Shigella was most pronounced and frequent with respect to tetracycline, streptomycin, levomycetin, as well as ampicillin and carbenicillin. Gentamicin, cephaloridin, polymyxin M, kanamycin, monomycin, neomycin and rifampicin were highly active against the Shigella. More than 50 per cent of the isolates were sensitive to levomycetin, ampicillin and carbenicillin. Differences in the frequency of the resistant strains and the spectrum of the antibiotic resistance of different Shigella subgroups (species) were observed. The study of 173 multiple resistant Shigella strains showed that about 67 per cent of the strains had a capacity for transduction of the resistance markers into the recipient cells of E. coli. The conjugative R-plasmids were most frequent in Sh. boydii and Sh. sonnei (95 and 95 per cent respectively), less frequent in Sh. flexneri and Sh. newcastle (68 and 53 per cent respectively) and least frequent in the mannitol negative Shigella (25 per cent). The capacity for transduction of R-plasmids in the strains carrying the determinants of resistance to 2 or 3 antibiotics was higher than in the strains carrying the determinant of resistance to one antibiotic. The clinical Shigella strains tested mainly had transmissive R-plasmids of fi--character (79 per cent).     

The structure and antibiotic sensitivity of the causative agents of community-acquired infectious diseases of bacterial origin in children]

Four hundred and forty pediatric patients at the age of 7 days to 15 years with various infections admitted to the Hospital within a month were examined. The biological material was inoculated to blood agar on the first days of the patient admittance to the Hospital and after the growth the organisms were isolated and identified. Antibiotic susceptibility of the isolates was assayed with the disk diffusion method. 479 strains in all were tested. The most frequent cases requiring hospitalization and antibiotic therapy were those of respiratory tract infections (54.09 per cent), urinary tract infections (26.36 per cent), cutaneous and subcutaneous fat diseases, gastrointestinal diseases and others (about 25 per cent of the cases in all). The main pathogens were Streptococcus viridans, S.aureus and S.epidermidis, as well as Enterobacteriaceae (chiefly E.coli) whose frequencies were practically equal (in 25-35 per cent of the cases). The Pneumococcus isolates amounted to 6.3 per cent. Nonfermenting bacteria (Pseudomonas aeruginosa and Acinetobacter) and some representatives of Enterobacteriaceae (Citrobacter, Serratia, Morganella) were isolated from 7 per cent of the patients. The frequency of Klebsiella and Enterobacter was about 11 per cent. The main pathogens were tested for their susceptibility to amoxycillin/clavulanic acid, ampicillin, oxacillin and gentamicin. The least active antibiotic was ampicillin. 88.8 per cent of the E.coli isolates and 100 per cent of the Klebsiella, P.mirabilis, Morganella, Citrobacter, Enterobacter and Serratia isolates were resistant to it. 53.2 per cent of the Streptococcus isolates including 64.5 per cent of the Pneumococcus isolates were as well resistant to ampicillin. 59.5 per cent of the Streptococcus isolates (mainly S.viridans and Enterococcus) was susceptible to oxacillin, 22.2 per cent of them being moderately susceptible. 62.5 per cent of the Pneumococcus isolates and 78.1 per cent of the Staphylococcus isolates were also susceptible to oxacillin. The highest susceptibility of the isolates was that to amoxycillin/clavulanic acid, i.e. 90.1 per cent of the strains, 79.9 per cent of them being highly susceptible. All the isolates of Citrobacter, Serratia and Morganella and some isolates of P.aeruginosa, Acinetobacter, Enterobacter, Klebsiella and E.coli were resistant to amoxycillin/clavulanic acid. As for the latter 5 organisms their susceptibility to amoxycillin/clavulanic acid was comparable with that to gentamicin. The susceptibility of the Streptococcus and Staphylococcus isolates to amoxycillin/clavulanic acid was significantly much higher than that to oxacillin, gentamicin and ampicillin: 93 per cent of the Streptococcus isolates (62.7 per cent of the Pneumococcus isolates) and 90.7 per cent of the Staphylococcus isolates.     

Treatment of staphylococcal pneumonias

Sensitivity of 129 strains of pathogenic staphylococci isolated from patients with pneumonia was studied with respect to a large number of drugs in the Bacteriological Laboratory of Konstantiny in the Algerian People's Democratic Republic. The method of paper discs and the Müller-Hinton solid nutrient medium were used. The staphylococcal strains were highly sensitive to cephalosporins, some of aminoglycosides (neomycin, gentamicin, tobramycin), nitrofurans, rifampicin, some antibiotics of other groups. Minocycline proved to be the most active among the tetracycline antibiotics. The number of the strains sensitive to it amounted to 82 per cent. 74--76 per cent of the isolates were resistant to tetracycline and oxytetracycline. 40--77 per cent of the isolates were resistant to sulfanilamides.     

A comprehensive evaluation of the biological properties of the causative agents of typhoid fever isolated from patients and carriers

The biological properties of 106 S. typhi cultures were studied; of these, 59 cultures were isolated from 45 chronic carriers and 47 cultures, from 23 typhoid fever patients. According to the degree of their virulence (CPD50 in the continuous cell-line culture Hep-2), the strains isolated from the patients were more virulent than those isolated from the chronic carriers. The mean value of lg CPD50 was 5.76 +/- 0.04 for the patients and 6.86 +/- 0.03 for the chronic carriers. The strains isolated from the patients showed greater variability in the degree of their virulence. The study of the plasmid spectrum showed that 9.4 +/- 5.6% of the strains contained plasmids. From the patients plasmid-containing strains were isolated more frequently than from the carriers (14.9 +/- 2.5% and 5.1 +/- 2.9%). Multiresistance to antibiotics in combination with the presence of plasmids was detected in 6 strains isolated from the typhoid patients with morbidity having the character of outbreaks.     

Comparative characteristics of the antibioticograms and biological properties of the staphylococci isolated from patients with various eye diseases]

A total of 1488 examinations of the conjunctival content of patients with various ophthalmic diseases were performed within 5 years (1973--1977). 989 (66.4 per cent) cultures were isolated. Staphylococci were isolated in 79.2 per cent of the patients irrespective of the diagnosis. The plasma-coagulating strains were isolated in 43.6 per cent of the patients with acute conjunctivitis. The plasma-negative staphylococci were more frequent in chronic conjunctivitis (83.5 per cent). A total of 188 strains were studied according to 18 tests. Determination of the antibiotic sensitivity showed that the number of the benzylpenicillin and tetracycline resistant strains among the plasma-coagulating staphylococci was higher in the patients with acute ophthalmic diseases. In chronic conjunctivitis no differences in the antibiotic sensitivity of the plasma-coagulating and plasma-negative strains were noted. Similar antibiotic sensitivity of all plasma-negative staphylococci irrespective of the diagnosis was found. High biological activity of the plasma-negative staphylococci was shown: 74.1 per cent of the isolates possessed phosphatase, 59.8 per cent possessed protease and 88.4 per cent a lysozyme-like enzyme. The strains isolated in chronic conjunctivitis produced protease more frequently that those isolated in acute ophthalmic diseases.     

Characterization of incompatibility group HI1 plasmids from Salmonella typhi by restriction endonuclease digestion and hybridization of DNA probes for Tn3, Tn9, and Tn10

Chloramphenicol resistance in Salmonella typhi is medicated by plasmids of the incompatibility group H, subgroup 1 (IncHI1). Eight IncHI1 plasmids from S. typhi strains originating in Mexico, Vietnam, Thailand, and India were examined by restriction enzyme digestion. The restriction enzymes, Apal, Xbal, and PstI were found to be most useful for comparison of plasmid DNAs. Four plasmids from S. typhi isolated in Mexico, Vietnam, and Thailand between 1972 and 1974 had identical restriction patterns with all three enzymes. The other IncHI1 plasmids showed only minor differences. However, some significant differences were noted between these IncHI1 plasmids and the prototype IncHI1 plasmid R27, which was isolated from S. typhimurium in 1961 and for which a restriction map has been constructed. Southern transfer hybridization with a nick-translated HI1 plasmid as a probe confirmed that there is a great deal of sequence homology among the IncHI1 plasmids. DNA probes were used to locate DNA sequences for ampicillin resistance (Tn3), chloramphenicol resistance (Tn9), tetracycline resistance (Tn10), and the one-way incompatibility between IncHI1 plasmids and the F factor, a characteristic property of IncHI1 plasmids. The results demonstrate that IncHI1 plasmids isolated from S. typhi from widely different geographic sources are very similar. Comparisons between the S. typhi plasmids and R27 indicated that conserved regions of DNA were those involved in conjugative transfer.     

Antibiotic sensitivity of pneumonia pathogens in newborns and problems of antibacterial therapy of the pathologic process]

The results of the bacteriological investigation of the secretion from the trachea, large bronchi and fauces of 36 newborns (including 27 preterms) with severe pneumonia were analyzed. 20 of them were born of women with complicating somatic, obstetric and gynecologic histories: candidiasis, herpes genitalis, chronic endometritis, adnexitis or chronic pyelonephritis that could be the risk of the fetus intranatal infection. During the acute period of pneumonia in the newborns within the first 4-8 days of life mainly Pseudomonas aeruginosa was isolated (51.3 per cent), Staphylococcus epidermidis, S. haemolyticus and Enterococcus faecalis were less frequent (18.9, 8.1 and 5.4 per cent, respectively). Klebsiella pneumoniae, Streptococcus anhaemolyticus and other organisms were extremely rare. On the whole the gramnegative microflora predominated. The study of the antibiotic susceptibility showed that the majority of the P. aeruginosa isolates were susceptible to amikacin and polymyxin B, the isolates susceptible to ceftazidime were less frequent, 20-25 per cent of the isolates were susceptible to ciprofloxacin, cefoperazone and imipenem and practically no isolates were susceptible to gentamicin. The S.epidermidis isolates were susceptible to rifampicin and vancomycin and in rare cases to fusidin and amikacin and resistant to oxacillin. When the treatment course was more than 15 days, the isolates proved to be susceptible to 1/3 of the presently available antibiotics. Because of the host low protective forces, peculiarities of the infection pathways and high frequency of the resistant strains it is valid to include netilmicin, imipenem, cefoperazone and ceftriaxone to the complex therapy of the newborns along with the substitution immunotherapy.     

Sensitivity of Corynebacterium diphtheriae isolated in Saint-Petersburg to antibacterial drugs]

One hundred and thirty strains of Corynebacterium diphtheriae isolated in St. Petersburg (42 toxigenic and 88 nontoxigenic) were tested with the method of serial dilutions in solid media for their susceptibility to 20 antibacterial drugs. The MICs of the drugs for the isolates ranged from < or = 0.015 to > or = 32.0 micrograms/ml. 13 per cent of the isolates was resistant at least to one antibacterial drug. The isolates resistant to erythromycin (11.5 per cent), lincomycin (11.5 per cent) and trimethoprim (8.5 per cent) were most frequent. 3 isolates (2.3 per cent) had multiple resistance to 8 drugs: benzylpenicillin, ampicillin, oxacillin, chloramphenicol, erythromycin, lincomycin, trimethoprim, and nitroxolin. No significant differences in the susceptibility of the toxigenic and nontoxigenic strains of C. diphtheriae were detected. Gentamicin, rifampicin, tetracycline, doxycycline and pefloxacin were the most active antibiotics.