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Antimicrobial sensitivity patterns were determined for 53 isolates of Haemophilus pleuropneumoniae from pneumonic porcine lung tissue. All strains were sensitive to chloramphenicol, gentamicin, spectinomycin, and sulfachlorpyridazine. Other antimicrobials tested had less efficacy for in vitro inhibition of H pleuropneumoniae.
A total of 520 Vibrio anguillarum strains, isolated from fish and the environment, were tested for their sensitivity to 20 different antibiotics. Most isolates were of European origin. The results were compared with data on the O-serogroup and plasmid contents. All strains were sensitive to neomycin, spectinomycin, nitrofurantoin, flumequine and oxolinic acid, while most strains were sensitive to streptomycin, oxytetracycline, chloramphenicol, sulphonamides, trimethoprim, sulphonamides with trimethoprim, nalidixan, rifampicin, novobiocin and O/129. A major part of the strains were resistant to the macrolides, spiramycin and lincomycin. For ampicillin, cephalothin, and colistin marked differences were recorded with respect to O-serogroup. Most O1 strains were resistant to colistin and sensitive to ampicillin and cephalothin, while most O2 strains were sensitive to colistin but resistant to ampicillin and cephalothin. Some antibiotic resistant strains carried plasmids but no conjugation experiments were carried out to detect possible R factors.
A comparison of the effect of 11 antibiotic inhibitors of protein synthesis on "enzymatic" and para-chloromercuribenzoateactivated "non-enzymatic" translation was made. It was found that fusidic acid which inhibits protein synthesis by blocking the action of one of the elongation factors (EF-G) did not suppress functioning of the "non-enzymatic" system. On the contrary, all the antibiotics blocking different functional sites of the ribosome itself such as tetracycline, chloramphenicol, erythromycin, edeine, thiostreptone, viridogrisein, spectinomycin, streptomycin, kanamycin and neomycin, were shown to inhibit the "non-enzymatic" translation. The data obtained corroborate the idea that the molecular mechanism which the ribosome utilized during "non-enzymatic" translation are similar or identical to the mechanism of normal "enzymatic" translation. It was found that the "non-enzymatic" working ribosome is more sensitive to all the antibiotics as compared to the ribosome synthesizing peptide with the participation of elongation factors (EF-T and EF-G). This suggests that the elongation factors increase the level of general resistance of the working ribosome against very different hindrances.
Two experiments were done to demonstrate whether the presence of Pseudomonas aeruginosa in bovine semen could affect fertilization and/or early embryonic development. In the first experiment, superovulated heifers were inseminated with semen naturally contaminated with P. aeruginosa (ADRI 102) or clean semen and seven day-old embryos were collected nonsurgically. The endometrium of treated heifers appeared more sensitive to the flush procedures. In experiment 2, heifers were inseminated at synchronized estrus with semen experimentally contaminated with P. aeruginosa (ADRI 102) and processed in the same way as commercial semen with antibiotics (gentamicin, lincomycin, spectinomycin and tylosin) or processed without antibiotics added. Embryos were recovered at slaughter seven days later. In general, there was no significant reduction in fertility or development of embryos in vitro as a result of relatively high numbers of P. aeruginosa in bovine semen.
Exposure of 10 Escherichia coli isolates in vitro to a concentration of lincomycin found in the intestine of swine fed the maximun concentration recommended in feed did not significantly affect sensitivity to 8 antibiotics, 1 nitrofuran, and 1 sulfonamide when compared with sensitivity of E coli isolates not exposed to lincomycin. Changes in sensitivity, on the basis of Kirby-Bauer interpretation, did occasionally occur; however, these alterations were in zonal sizes, which were marginal for designation as sensitive, intermediate, or resistant. These same fluctuations were observed in E coli not exposed to lincomycin. Exposure of E coli to lincomycin in the intestinal tract of swine for 34 days did not alter sensitivity of E coli to tetracycline, dihydrostreptomycin, spectinomycin, lincomycin, or triple sulfa. The results indicated that addition of lincomycin to the feed did not appear to promote resistance transfer in E coli.
With frequent use of aminoglycoside antimicrobials and beta-lactam antibiotics in hospitals in the last few years, the number of bacterial strains resistant to these chemotherapeutics increased. Lately, strains of E. coli, Klebsiella, Enterobacter, Serratia, Proteus and Pseudomonas resistant to many antimicrobials (ampicillin, carbenicillin, cephalothin, chloramphenicol, gentamycin, tobramycin, sisomycin, neomycin, paromomycin, kanamycin, streptomycin, spectinomycin, tetracycline, sulphonamides) were isolated from patients of the university hospital in Zuerich. The resistant phenotype of two representative strains (Klebsiella pneumoniae 1 and Serratia marcescens 2) could be transferred by mixed cultivation to E. coli K-12. Multiple resistance of strain 1, and addition, could be transferred to Salmonella typhimurium, Serratia marcescens, Providencia, Proteus mirabilis and Klebsiella pneumoniae in varying frequencies. Transfer to Pseudomonas aeruginosa, however, could not be achieved. Spontaneous instability of resistance was observed in 0.15% of the cells of an overnight brothe culture and in 90% of the cells of a three months old culture. Conjugation, instability and the response to the sex phages MS-2 and If-1 suggested that resistance was mediated by a monomolecular R-factor, belonging to the fi+-type. This suggestion was confirmed by molecular characterization of the resistance plasmids. After transfer of the R-factors of K. pneumoniae 1 (R-FK 1) and Serratia marcescens 2 (R-FK2) into E. coli K-12, plasmid DNA was labelled with (methyl-3H) thymidine, and isolated by isopycnic centrifugation in cesiumchlorid-ethidium-bromide. Analysis of plasmid DNA then was carried out by sedimentation in a 5-20% neutral sucrose gradient together with reference plasmids of known molecular weights and sedimentation constants. The analysis revealed that R-FK1 had a molecular weight of 54 X 10(6) and R-FK2 of 50 X 10(6) daltons. The values were confirmed by contour length measurements of open circular forms with an electron microscope. A comparison of the sedimentation profile of labelled plasmid DNA from strain 1 and 14C-labelled DNA of E. coli K-12 (R-FK1) showed that the wild-type strain contained, besides the large resistance plasmid, at least two smaller "cryptic" plasmids. These smaller plasmid molecules were also found in antibiotic susceptible variants of strain 1, which did not contain the 54 X 10(6) dalton plasmid molecule, responsible for the resistant phenotype. The number of copies of R-FK1 in E. coli K-12 was determined to be 2, indicating stringent control of replication. It is discussed that the growing number of isolations of strains of Escherichia, Klebsiella, Serratia, Proteus, Providencia and Pseudomonas, exhibiting the same resistance phenotype, results from the spread of the R-factor described above among the hospital bacterial flora.
This study which aimed to determine the susceptibility patterns of seven often prescribed antimicrobial agents for treatment of gonorrhoea in Kumasi, Ghana, over a study period of 3 years (1991 through 1993), examined a total of 1187 specimens (high vaginal, cervical and urethral). Identification of N. gonorrhoeae was by colonial morphology, oxidase test, sugar fermentation test and the Gram-stain. The Intra-lactam strip method was used to determine which Neisseria gonorrhoeae isolates were beta lactamase producers (PPNG). Of the 1115 PPNG strains encountered, 300 were selected for MIC determination against seven (penicillin, cotrimoxazole, tetracycline erythromycin, spectinomycin, norfloxacin and ceftriaxone) antimicrobial agents in current usage in Kumasi, Ghana. Based on our results it was concluded, that PPNG strains are rampant/endemic in Kumasi, Ghana and that most exhibited multiple antimicrobial resistance. This situation requires, therefore, a serious review of the current Ghana Ministry of Health gonorrhoea treatment regimen. Suggestions to this end have been made.
Although the prevalence of gonorrheal and chlamydial infections varies based on patient population, these infections remain a concern, especially for young women. Management should reflect the fact that a large proportion of isolates of N. gonorrhoeae are resistant to penicillin, tetracycline, or spectinomycin. Because up to 45% of women with gonorrheal infection have coexistent chlamydial infection, the treatment should be effective against both organisms. The sexual partners of infected women should be tested, if possible, and treated appropriately.
The extensive use of antibiotics in Nicaragua raises concerns about the resulting levels of susceptibility of pathogenic bacteria. This is the first study that characterizes 18 strains of N. gonorrhoeae isolated in Nicaragua (1989), for their antibiotic susceptibility. Strains were predominantly of the auxotype/serotype Proto/PIB. There was no difference in lipopolysaccharides profiles obtained after SDS-PAGE for all strains. Variable expression of the PII outer membrane protein was not associated to antimicrobial resistance. All strains were susceptible to ceftriaxone, spectinomycin, rifampin and cefoxitin. The strains were classified in five groups based on plasmid profiles. A total of 78% of the isolates were penicillinase-producing (PPNG) and 22% were tetracycline-resistant N. gonorrhoeae (TRNG). One PPNG strain showed a concomitant decreased of penicillin binding to penicillin-binding protein 2. These randomly chosen isolates of N. gonorrhoeae from Nicaragua possess high levels of resistance to multiple families of drugs.
Actinomyces pyogenes induces suppurative diseases in ruminants and many other animal species. Most of the earlier antimicrobial susceptibility data has been obtained by disk diffusion techniques. Minimal inhibitory concentrations (MIC) of 22 antibiotics for 103 strains of A pyogenes of animal origin were determined by agar dilution test (Mueller-Hinton agar supplemented with 5% sheep blood). All the strains were susceptible to penicillin G, amoxicillin, methicillin, cephalothin, cefoperazone, pristinamycin, kanamycin, gentamicin, spectinomycin, chloramphenicol, vancomycin, novobiocin and rifampin. Fifty-nine percent were resistant to streptomycin, 67% to tetracycline, doxycycline and minocycline, 12% to erythromycin, spiramycin and lincomycin. Most of the strains resistant to macrolides and lincosamides exhibited a constitutive MLS(B)-like phenotype. In the cultural conditions used, it was not possible to determine accurate MIC of fucidic acid and pefloxacin.
Fifteen hemolytic gram-negative bacteria were isolated from the respiratory tracts of sick birds suffering from a long-lasting respiratory syndrome or from the bone marrow of dead birds distributed in the southern part of Taiwan. These were classified as Pseudomonas aeruginosa (10 isolates), Pseudomonas fluorescens (2 isolates), Pseudomonas stutzeri (1 isolate), Pasteurella haemolytica (1 isolate), and Proteus morganii (1 isolate). Each isolate was inoculated intraperitoneally into one group of ten 4-week-old male white leghorn chickens. Mortality and lesions were scored daily for 1 week. Three of the 10 isolates of Pseudomonas aeruginosa caused 100% mortality. Six other isolates of Pseudomonas aeruginosa and the one isolate of Proteus morganii caused 50% mortality. The remaining isolates induced less than 30% mortality. The sole nonpathogenic sample was one isolate of Pseudomonas fluorescens. When therapeutic levels of 22 antibiotics or sulfa drugs were evaluated for their inhibitory activity against the 15 isolates, the most effective were apramycin (15/15), gentamicin (15/15), spectinomycin (13/15), oxytetracycline (8/15), and sulfachloropyrazine (7/15). The least effective were ampicillin, cloxacillin, and tiamulin, which were not effective against any of the isolates. The 14 other drugs were of very low (> 4/15) effectiveness. Most of the isolates studied were virulent for chickens and very resistant to currently used drugs.
Site-directed mutagenesis has been used to introduce specific amino acid changes into the photosystem I reaction center in the green alga Chlamydomonas reinhardtii. Plasmids containing mutated copies of the chloroplast psaB gene, encoding a polypeptide of the photosystem I reaction center heterodimer, were introduced into the chloroplast genome by particle bombardment. Successful transformants were selected by two procedures. The first involved complementation of a nonphotosynthetic mutant of Chlamydomonas, CC-2341 (ac-u-g-2.3), which has a frameshift mutation in the psaB gene, and selection of photosynthetic transformants on minimal medium. The second procedure utilized a co-transformation procedure with a plasmid containing a rRNA gene that confers spectinomycin resistance. Homologous replacement of the psaB gene was confirmed by screening for a unique restriction enzyme site within the transforming psaB sequences. These procedures have been used to specifically mutate a highly conserved proline-cysteine motif suggested to be important in coordinating the [4Fe-4S] iron-sulfur center Fx. Our results show that the cysteine is essential for assembly of the photosystem I reaction center although the adjacent proline fulfills no identifiable function. The approach described in this paper will be of value to future studies of the structure, function, and assembly of photosystem I.
A study was conducted to determine the antibiotic resistance and biochemical characteristics of 2690 Salmonella strains belonging to 52 serovars and isolated from environmental and feed samples from 270 turkey flocks in Canada. Resistance of the Salmonella strains to the aminoglycoside antibiotics varied widely; none of the strains were resistant to amikacin, 14.2% were resistant to neomycin, 25.8% were resistant to gentamicin, and 27.7% of the strains were resistant to kanamycin. Most strains (97.6%) were resistant to the aminocyclitol, spectinomycin. Regarding resistance to the beta-lactam antibiotics, 14.3% and 14.4% of the strains were resistant to ampicillin and carbenicillin, respectively, whereas only 5 (0.2%) of the strains were resistant to cephalothin. None of the strains were resistant to the fluoroquinolone ciprofloxacin or to polymyxin B. Resistance to chloramphenicol and nitrofurantoin was found in 2.4% and 7% of the strains, respectively. Only 1.7% of the strains were resistant to the trimethoprimsulfamethoxazole combination, whereas 58.1% were resistant to sulfisoxazole. Thirty-eight percent of the strains were resistant to tetracycline. Salmonella serovars differed markedly in their drug resistance profiles. Biochemical characterization of the Salmonella showed that the S. anatum, S. saintpaul and S. reading serovars could be divided into distinct biotypes.
Only 229 cases of gonococcal infection were recorded in Norway in 1994 (population 4.3 million), as against more than 14,000 cases two decades before. Up to now aminopenicillins with probenecid have been the standard treatment. In 1994, 29% of the reported cases of gonococcal infection were caused by a betalactamase-producing strain. We now recommend treating uncomplicated gonococcal infections with a single oral dose of ciprofloxacin 500 mg, or ofloxacin 400 mg. Pregnant or lactating women should receive intramuscular injections of cefotaxim 500 mg, or spectinomycin 2 g. Test-of-cure is essential. Its main purpose is to discover resistant strains and reinfections. Thorough contact tracing is more important than ever. Culture verification, susceptibility testing and test-of-cure in all cases will influence the continuous reevaluation of these guidelines.
Residual antibiotics in milk were identified by high-voltage electrophoresis in 1% agarose gel and bioautographic detection. The test strain Bacillus subtilis BGA was used for the detection, pH of the culture medium was 8.0. An electrophoretic identification map of 13 selected antibiotics has been set up and the following minimal inhibition concentrations (MIC), expressed in microgram per 1 g, have been established: benzylpenicillin 0.06; ampicillin 0.25; streptomycin 0.5; dihydrostreptomycin 0.2; spectinomycin 40; gentamycin 0.06; neomycin 0.15; oxytetracycline 5; tetracycline 2.5; chlortetracycline 1; erythromycin 0.01; tylosin 1; chloramphenicol 20. The established values of MIC were compared with the Maximum Residue Limits (MRL) as defined currently in the legislation of the European Union. The condensation of samples by freeze-drying increased the sensitivity of the method which was used for the identification of residual antibiotics detected by microbiological screening techniques in milk.
The antimicrobial susceptibility of 775 isolates of Neisseria gonorrhoeae, recovered in Barbados over a five-year period, was studied by disc diffusion. Sensitivity to penicillin declined from 56% in 1990 to 38% in 1994. The prevalence of beta-lactamase production rose from 30% to 50% during this period and sensitivity to tetracycline declined from 96% to 46%, while co-trimoxazole and spectinomycin sensitivities varied. Ceftriaxone, norfloxacin and erythromycin were the only compounds tested to which sensitivity remained uniform. The results confirm the current recommendations by several agencies that ceftriaxone or an oral fluoroquinolone should be considered the drug of choice for the empirical treatment of gonorrhoea.
Since the introduction of methicillin, methicillin resistant S. aureus (MRSA) was appeared in 1961 in England. MRSA produces specific penicillin-binding protein PBP2' which shows very low affinity to most of beta-lactam antibiotics. The region around mecA is called additional DNA or mec DNA and is thought to be extraspecies origin. From the study of mec DNA, it was revealed that there were three types of mec DNA. In the case of mec DNA of N315, a transposon Tn554 which encoded erythromysin and spectinomycin resistance, and a plasmid pUB110 which encoded resistance to kanamycin, tobramycin, and bleomycin were integrated. MRSA became resistant to many antibiotics during a few years which were effective at the time of introduction, such as, carbapenems, new quinolones, and minocycline. MRSA has changed their properties by obtaining resistance-genes or generating mutations on its chromosomal DNA.
Antimicrobial resistance has become a major medical and public health problem. The main factor responsible for development and spread of bacterial resistance is injudicious use of antimicrobial agents which has resulted in most gram positive and gram negative bacteria continuously developing resistance to the antimicrobials in regular use at different time periods. In East Africa, among E. coli in urinary tract infections, more than 80% are currently resistant to ampicillin, cotrimoxazole and tetracycline while more than 80% of the isolates are still susceptible to nitrofurantoin, gentamicin and third generation cephalosporins. Penicillin G resistant strains of pneumococci were first reported in 1967 but had gradually increased to about 20% in 1991. Among group A streptococci, all natural strains are still sensitive to penicillin G while resistance to tetracycline has reached alarming proportions. In Tanzania, more than 65% of N. gonorrhoeae isolates are beta-lactamase producers, however, spectinomycin, second and third generation cephalosporins and ciprofloxacin are effective against most strains. Vibrio cholerae 01 strains resistant to multiple antibiotics are widely spread globally, however, there are recent reports indicating that withdrawal of the drugs can lead to loss of the antibiotic resistance factors. Despite varied susceptibility of N. meningitidis strains world wide, isolates in Tanzania are still susceptible to commonly available drugs including penicillin G and chloramphenicol. Available methods for control of spread of bacterial resistance include rational use of antimicrobial agents including control in animal husbandry, change to newer antimicrobials, rotational use of drugs and constant surveillance for emerging bacterial resistance.