Susceptibility to selected antibiotics of Yersinia enterocolitica 03 strains, carrying and not carrying plasmid pYV

A total of 199 clinical strains of Yersinia enterocolitica serotype O3, biotype 4 were tested for their susceptibility to antibiotics (158 strains carried the virulence plasmid pYV and 41 strains did not). 114 isolates were tested by standard disk diffusion method for 21 antibiotics. Almost all tested strains were resistant to ampicillin and cefazolin and susceptible to amoxycillin/clavulanate, cefaclor, cefamandole, cefuroxime, cefotaxime, ceftriaxone, aztreonam, imipenem, gentamicin, amikacin, netilmicin, tetracycline, doxycycline, chloramphenicol, ciprofloxacin, sulphamethoxazole, co-trimoxazole, trimethoprim and furazolidone. In addition minimal inhibitory concentrations (MICs) of 15 antibiotics were determined by agar dilution method for all 199 strains (158 plasmid positive and 41 strains plasmid negative). Third-generation cephalosporins such as cefotaxime and ceftriaxone and a fluoroquinolone (ciprofloxacin) were the most active antimicrobial agents, tested followed by aztreonam, imipenem, trimethoprim, tetracycline, gentamicin, chloramphenicol, amoxycillin/clavulanate, cefaclor, cefuroxime, amikacin, furazolidone and sulphamethoxazole. The present study demonstrated a high susceptibility of clinical strains of Y. enterocolitica to most of the tested antibiotics. In general, there was no significant difference between susceptibility of virulence plasmid pYV positive and virulence plasmid negative strains to antibacterial agents.     

Post-therapeutic levels of antimicrobial drugs in faeces.

After oral administration for 3 days, furazolidone disappeared from the faeces on the first, polymyxin B and ampicillin on the fourth, and trimethoprim + sulphamethoxazole and nalidixic acid on the fifth day.     

Susceptibility to selected coagulase-negative chemotherapeutic agents of methicillin resistant staphylococci isolated from clinical materials in 1997-1998

The study was aimed at assessment of the sensitivity of methicillin-resistant coagulase-negative staphylococci isolated from clinical material in 1997/1998 to selected chemotherapeutic agents. The investigated material comprised 96 methicillin-resistant coagulase-negative staphylococci from hospital and ambulatory infections isolated during the period from April 1997 to May 1998. Species affiliation was determined by classical identification methods and commercial diagnostic tests for identification of staphylococci. Methicillin resistance was determined by agar disk-diffusion method and screening. Sensitivity to chemotherapeutics was determined by agar disk-diffusion method and agar dilution methods. All the investigated strains were sensitive to nitrofurantoin, furazolidone and vancomycin. To teicoplanin--the second glycopeptide antibiotic--84% strains were sensitive, whereas the percentages of resistant and moderately sensitive strains amounted to 5.2% and 10.4%, respectively. 85% and 82% of coagulase-negative staphylococcal strains were sensitive to fusidic acid and mupirocin. Considerable differences were noted with respect to sensitivity to aminoglycoside group antibiotics. About 35% of strains were sensitive to gentamicin, and 90% sensitive to netilmicin. Ca. 40% of coagulase-negative staphylococci were resistant both to cotrimoxazole and trimethoprim, which, in view of 98% resistance to the second component of cotrimoxazole, may be associated with the activity of only one of the components of the drug--trimethoprim.     

Susceptibility to selected chemotherapeutics of Staphylococcus aureus strains resistant to methycyline isolated from clinical materials in the years 1991-1992 and 1997

The susceptibility to selected chemotherapeutic agents was determined in 100 strains of Staphylococcus aureus methicillin-resistant (MRSA) isolated from clinical materials in 1991-1992 (50 strains) and in 1997 (50 strains). Two methods were used for the determination: disc method and antibiotic dilution in agar. The minimal inhibitory concentration (MIC) was determined for vancomycin, teicoplanin, furazolidone, nitrofurantoin, ofloxacin, gentamicin, netilmicin and trimethoprim. The concentrations of the chemotherapeutics in the substrate ranged from 0.125 to 512 mg/l. The obtained results served for drawing of the following conclusions: all studied MRSA strains isolated in 1991-1992 and in 1997 were sensitive to glycopeptide antibiotics: vancomycin and teicoplanin, to nitrofurans: nitrofurantoin and furazolidone, and to fusidic acid. MRSA strains isolated in 1991-1992 were sensitive to ofloxacin, but in 1997 about 80% of the strains were resistant to that antibiotic, and this resistance was noted in S. aureus strains with homogeneous resistance to methicillin. Increasing frequency of resistance to mupirocin was found, in 1991-1992 4% of the strains were resistant, and in 1997 the resistance of MRSA to that antibiotic was found in 12%. No changes occurred in the sensitivity of staphylococci to trimethoprim/sulfamethoxazole (cotrimoxazole). About 94% of strains in 1991-1992 and 1997 were sensitive to that drug. The sensitivity to cotrimoxazole is connected with one of its components (trimethoprim), with 94% of MRSA strains sensitive to it.     

Comparative Trial of Tetracycline,Chloramphenicol, and Trimethoprim Sulphamethoxazole in Eradication of Vibrio cholera El Tor

A comparison of tetracycline, chloramphenicol, and trimethoprim/sulphamethoxazole showed that all hasten the eradication of Vibrio cholerae from the stools of patients with cholera.A four-day period of tetracycline or trimethoprim/ sulphamethoxazole was adequate for eradicating V. cholerae from the stools of all patients, but three days, as suggested by the W.H.O. Expert Committee, was not. Four days of chloramphenicol therapy was sufficient for most patients, but a minority required up to seven days'' therapy.Purging produced reappearance of V. cholerae in the stools of one-eighth of the patients who had had three successive daily negative stool cultures; such patients are a potential danger to the population.     

Trimethoprim resistance in hospitals.

During November 1980 to April 1981, 1561 urinary tract pathogens were collected from Turku City Hospital, Turku University Central Hospital, and Kuopio University Central Hospital. Resistance of the strains was tested by agar-plate dilution against trimethoprim, sulphamethoxazole-trimethoprim, sulphamethoxazole, ampicillin, and nitrofurantoin. Resistance to trimethoprim (greater than 8 mg/l) occurred in 8.6-12.2% of strains from the university hospitals (Pseudomonas excluded) and 38.3% of strains from Turku City Hospital. Resistance of Escherichia coli occurred in 4.1-6.2% of strains from the university hospitals and 21% of strains from Turku City Hospital. Proteus mirabilis was the most resistant of the clinically important bacterial species with resistance to trimethoprim in 29-78%. Attention is called for in defining the type of hospital used for a particular study: bacterial resistance in different hospitals cannot be compared direct and one hospital is not necessarily representative for a whole country. After seven years'' use of plain trimethoprim the prevalence of resistance in the two university hospitals in Finland was similar to that in a London hospital just before plain trimethoprim was registered for use in Britain.     

Sensitivity of Haemophilus influenzae to Antibiotics

The use of many different antibiotics to treat chest infection has led us to test the sensitivity of 68 strains of Haemophilus influenzae to 15 different compounds. These included established compounds such as ampicillin and tetracycline and newer agents such as cephalosporins and clindamycin. The minimum inhibitory concentrations of the compounds for H. influenzae were then compared with blood levels attained after the usual dose regimens. There has been a significant increase in tetracycline resistance in the last few years, but all strains were sensitive to ampicillin, chloramphenicol, sulphamethoxazole, and trimethoprim, Several antibiotics were found to be microbiologically unsuitable for treating H. influenzae infections.     

Controlled Comparison of Tetracycline and Furazolidone in Cholera

A controlled comparison of furazolidone and tetracycline in the treatment of cholera indicates that, in either dosage used, furazolidone reduced total stool volume by 50% and duration of diarrhoea by 40%. These results are comparable to those achieved with tetracycline, which was given in presently recommended dosage. Both furazolidone and tetracycline significantly reduced the rate of stool output within 18 to 24 hours of starting antibiotic treatment. Furazolidone was significantly less effective than tetracycline in rapidly and consistently terminating vibrio excretion. One convalescent carrier of cholera vibrios was identified among control patients; none was identified among patients treated with either tetracycline or furazolidone. All Vibrio cholerae strains tested were sensitive to tetracycline and furazolidone, but larger concentrations of the latter were required to achieve inhibition of growth. It is concluded that tetracycline remains the antibiotic of choice in cholera but that furazolidone would be a useful adjunct to cholera therapy when tetracycline is unobtainable or if strains of V. cholerae with clinically significant resistance to tetracycline should be encountered.     

Potentiation of Inhibitory Activity of Colistin on Pseudomonas aeruginosa by Sulphamethoxazole and Sulphamethizole

Potentiation of colistin by sulphamethoxazole and sulphamethizole was demonstrated with 19 out of 20 strains of Pseudomonas aeruginosa. This enhancement was bactericidal as well as bacteriostatic. Synergy between trimethoprim and sulphamethoxazole was also demonstrated with four strains of Ps. aeruginosa, but even when the two drugs were combined high concentrations of trimethoprim were still required to produce a bactericidal effect. Combinations of sulphamethoxazole and gentamicin appeared to be synergistic when the bacteriostatic effect was measured, but the combined bactericidal effect was indifference. The bactericidal and bacteriostatic effect of combinations of carbenicillin with sulphamethoxazole was also indifference.     

Trimethoprim in the Treatment of Urinary Infections in Hospital

Success in the cure of urinary infections of hospital patients was compared for five-day courses of sulphamethoxazole alone, sulphamethoxazole plus one-tenth its weight of trimethoprim, and sulphamethoxazole plus one-fifth its weight of trimethoprim (Septrin). The cure rates were 65%, 84%, and 92% respectively. Fifty-four per cent. of 111 patients had urinary tract abnormalities. Forty-three per cent. of the causative organisms were sulphonamide-resistant in vitro. There were no major side-effects, though two patients had pruritus or a rash.The degree of potentiation of sulphamethoxazole activity by one-fifth the weight of trimethoprim was so great that its cure rate of infections due to sulphonamide-resistant organisms exceeded that of sulphamethoxazole alone used in infections due to sulphonamide-sensitive organisms. The degree of synergism between trimethoprim and sulphamethoxazole demonstrated in vitro against urinary organisms was directly related to the cure rate of the combination.     

Drug resistance in Shigella dysenteriae,S flexneri and S boydii in England and Wales: increasing incidence of resistance to trimethoprim.

A total of 2753 strains of shigella belonging to subgroups A, B, and C that were isolated from patients in England and Wales during the period from 1979 to mid-1983 were studied. Of these, 1690 (61%) were from patients recently returned from abroad or in contact with recent travellers, and 760 (45%) of these affected travellers from the Indian subcontinent. The number of strains resistant to sulphonamides and streptomycin remained at a high level throughout (average 76% and 72% respectively). Resistance to tetracyclines, ampicillin, and chloramphenicol rose, reaching 63%, 51%, and 48%, respectively, in 1982. Strains resistant to trimethoprim were seen in substantial numbers for the first time and increased from 1.3% of all strains in 1979 to 9.9% in 1982 and 16.8% in the first half of 1983. The proportion of patients with recent foreign contact was notably smaller among those with strains resistant to trimethoprim than among those with strains sensitive to trimethoprim. The increase in resistance to trimethoprim might partly result from the use in Britain of compounds containing trimethoprim for the treatment of shigellosis.     

Effects of antibiotics on the growth and morphology of Pasteurella multocida.

The effects of subminimal inhibitory concentrations (subMICs) of certain antibiotics, namely penicillin G, tetracycline and trimethoprim/sulphamethoxazole, on the growth and morphology of Pasteurella multocida were evaluated. SubMICs of penicillin markedly reduced the growth of P. multocida. Tetracycline and trimethoprim/sulphamethoxazole had no effect on its growth. SubMICs of penicillin greatly affected the morphology of P. multocida. At the highest concentrations tested (1/2 and 1/4 MIC) cells were acapsulate, and long filamentous cells (4-6 microns) were observed with some isolates. There was no correlation between the observed differences in the penicillin-binding proteins of the P. multocida isolates, and the extent of cell filamentation induced by penicillin G. SubMICs of tetracycline and trimethoprim/sulphamethoxazole did not seem to affect capsule production although filamentation was observed. Our results indicate that subMICs of penicillin can reduce growth of P. multocida. Furthermore, results also indicate that subMICs of antibiotics can affect the production of capsular material and the morphology of P. multocida.     

Trimethoprim-resistant bacteria: cross-resistance patterns

One hundred and eighty one strains (clinically isolated) of trimethoprim-resistant bacteria were tested for sensitivity to proguanil, pyrimethamine, methotrexate and methasquin. All these agents had less intrinsic antibacterial activity than trimethoprim, and there was marked cross-resistance between trimethoprim on the one hand and pyrimethamine and methasquin on the other. Methotrexate was of very low activity against Gram-negative bacilli, but was highly inhibitory for streptococci. Proguanil had approximately the same activity for all the organisms tested, and appears not to act as an anti-folate agent.     

Trimethoprim resistance in Finland after five years' use of plain trimethoprim.

A total of 1388 urinary bacterial pathogens were tested for resistance to plain trimethoprim after five years'' use of this drug for prophylaxis against urinary tract infections. Samples were obtained in Turku, Finland, where use of the drug is much greater than in other parts of Finland. Resistance to trimethoprim (greater than 8 mg/l; agar-dilution method) occurred in 20.3% of strains isolated from outpatients and 39.8% of strains isolated from inpatients. Escherichia coli and Micrococcus showed low incidences of resistance (11% and 13% respectively in ouptatients and 23% and 19% respectively in inpatients); Enterobacter, Streptococcus faecalis, and Staphylococcus epidermidis occupied an intermediate position; and Proteus mirabilis and Klebsiella were resistant in 41-76% of cases. Similar incidences of resistance were observed to sulphamethoxazole-trimethoprim, sulphamethoxazole, ampicillin, and nitrofurantoin. These findings together with the rare occurrence of side effects and convenient dosage confirm the usefulness of plain trimethoprim for urinary tract infection.     

Antibiotic resistance of Salmonella strains isolated from children living in the wastewater-spreading field of Marrakesh city (Morocco)

A total of 813 Salmonella strains isolated from raw wastewater and stool specimens of inpatient children, living in the wastewater-spreading field of Marrakesh city, were examined for their susceptibility to 15 antimicrobial agents. All the isolates were susceptible to cefotaxime, and almost of them showed susceptibility to gentamicin (99.88%), trimethoprim-sulphamethoxazole (98.04%), nalidixic acid (98.04%), kanamycin (97.30%), trimethoprim (97.18%), and chloramphenicol (96.07%). The highest levels of antibiotic resistance were obtained for cephalothin (29.27%), amoxicillin (26.44%), sulphamethoxazole (26.07%), and ampicillin (25.21%). The strains from the serogroup B showed the highest antibiotic resistance frequencies. The percentage of polyresistant strains (36.09%) was significantly higher than that of monoresistant isolates (15.49%). The incidence of drug resistance in Salmonella isolates from stools was significantly higher than in those isolated from wastewater.     

Trimethoprim and Sulphamethoxazole in Typhoid

Six patients with proved typhoid fever were treated with a combination of trimethoprim and sulphamethoxazole; four others were treated with chloramphenicol. All ten patients made an uneventful recovery.Though the numbers are small it appears that the patients treated with the combined drugs did just as well as those treated with chloramphenicol, and fever seemed to subside quicker with the combined drugs.Trimethoprim and sulphamethoxazole have low toxicities, so further studies of their use in the treatment of typhoid are justified.     

Multidrug resistance to antibacterial drugs of Salmonella enterica subsp. enterica strains isolated in Poland in the 1998-1999 period]

A total of 510 Salmonella enterica subsp. enterica strains representing 56 serotypes, isolated from human stool specimens during 1998-2000 in sanitary-epidemiological units in Poland were tested for their susceptibility by a standard disk diffusion method for: ampicillin, cefotaxime, chloramphenicol, tetracycline, streptomycin, gentamicin, kanamycin, nalidixic acid, ciprofloxacin, furazolidone, cotrimoxazole, sulfonamides and trimethoprim. For 201 of the investigated strains, belonging to 5 most common isolated serotypes (S. Enteritidis, S. Typhimurium, S. Hadar, S. Infantis and S. Virchow) the minimal inhibitory concentrations (MICs) for the aforementioned antibiotics, as well as for amoxicillin with clavulanian were determined. Selected strains were screened for production extended spectrum b-lactamases (ESBLs). It was observed that 42.9% of Salmonella enterica subsp. enterica strains were resistant to 2 or more antibiotics, with the highest prevalence of MDR strains among serotypes Typhimurium, Hadar and Virchow. Resistance to ampicillin, streptomycin, tetracycline, nalidixic acid, furazolidone and sulphonamides was observed most frequently. Over 93% of S. Virchow strains were resistant to furazolidone. No strains resistant to ciprofloxacin were detected according to the NCCLS guidelines, but 31.3% of isolates exhibiting reduced ciprofloxacin susceptibility (MICs ranging between 0.125 and 0.5 mg/l). Two strains S. Mbandaka and Salmonella group D (variant motility--) were resistant to cefotaxime and probably produced ESBL.     

Trimethoprim-Sulphamethoxazole: Comparative Study in Urinary Infection in Hospital

Trimethoprim is inhibitory for a wide range of bacteria, and when used in combination with a sulphonamide marked synergy has been reported.In order to test its value in the treatment of urinary infections 154 hospital patients with infections of varying severity and due to a wide range of organisms were treated with combinations of sulphamethoxazole and trimethoprim. Combinations of these substances in two different ratios (2:1 and 10:1) were used in 113 patients, and one week after the end of treatment about three-quarters were cured by both combinations. In a second study 106 patients were treated with a sulphamethoxazole-trimethoprim combination (5:1), ampicillin, or sulphadimidine. The cure rate with the 5:1 combination was higher than that found with ampicillin or sulphadimidine both one week after finishing treatment (sulphamethoxazole-trimethoprim 85%, ampicillin 70%, sulphadimidine 40%) and at the fourth- to fifth-week follow-up (sulphamethoxazole-trimethoprim 67%, ampicillin 52%, sulphadimidine 15%).The results obtained with the various sulphamethoxazole–trimethoprim combinations did not indicate that a particular ratio was superior for treating urinary infections in general or for those caused by any particular species of organism.Laboratory studies showed that many bacteria causing urinary infections in hospital were sensitive to trimethoprim, and the therapeutic results could have been largely predicted from a knowledge of the in-vitro sensitivity tests to trimethoprim alone. For example, sulphamethoxazole–trimethoprim in the treatment of Proteus mirabilis infections was less successful than in those due to Escherichia coli, and this finding was clearly reflected in the higher minimal inhibitory concentrations for trimethoprim of Pr. mirabilis.The sulphamethoxazole–trimethoprim combination was simple to administer, free from side-effects, and gave satisfactory results in the treatment of urinary infections that occurred in hospital patients.     

Studies on shigella isolated in southern Taiwan.

During 1969, a total of 1,476 fecal and rectal swab specimens was collected from children with diarrhea and 249 strains of shigella were isolated. The incidence was 16.9%. The serotypes of 249 strains were: Shigella dysenteriae, 1.6% (4 strains); S. flexneri, 73.1% (182 strains); S. boydii, 3.2 (8 strains) and S. sonnei, 22.1% (55 strains). There was no marked difference of the isolation rate throughout the whole year. The susceptibility of shigella isolates to chemotherapeutic agents were also investigated. The percentage of the strains susceptible to gentamicin was 97.2%; to cephaloridine, 93.2%; to kanamycin, 91.9%; to colistin, 91.6%; to hetacillin, 88.4%; to ampicillin, 82.4% and to nalidixic acid, 79.9%. The other tested chemotherapeutic agents were less effective.     

Increase in antibiotic resistance in Haemophilus influenzae in the United Kingdom since 1977: report of study group.

A survey of antibiotic resistance in Haemophilus influenzae was carried out in the United Kingdom with 25 laboratories participating. The incidence of resistance in the 1841 strains examined was: tetracycline 3.1%, ampicillin 6.2%, chloramphenicol 1.03%, trimethoprim 1.4%, and sulphamethoxazole 1.5%. Of the 115 strains resistant to ampicillin, 106 produced beta-lactamase. Seventy-nine strains were capsulate, none of which was chloramphenicol resistant, but nine produced beta-lactamase (11.4%). Comparison of these figures of antibiotic resistance with those from a similar survey performed in 1977 showed a significant increase in resistance of H influenzae to ampicillin, chloramphenicol, and trimethoprim.