Frequency of resistance to tetracycline and chloramphenicol amongSalmonella strains isolated in the Netherlands in 1962

Out of 12,472 strains ofSalmonella isolated in the Netherlands in 1962, 1365, or 10.94%, were found to be resistant to tetracycline or chloramphenicol or to both. Compared with the findings of the preceding years (1958/59:2.08%, 1960:1.29%, 1961:3.96%) this is a considerable increase. Of these 1365 strains, 1285, or 94.1%, were resistant to tetracycline and 46, or 3.4%, were resistant to chloramphenicol. The remaining 34 strains, or 2.5%, were resistant to both drugs.Among allSalmonella strains isolated in 1962, 5517 belonged to the speciesS. typhi murium. Of these, 1203 or 21.8%, were resistant to tetracycline. The resistance rates of strains originating from human patients, calves, pigs, other animals and other materials were 24.4%, 37.1%, 15.0%, 8.0% and 5.7% respectively.Factors which may possibly have contributed to the greatly increased frequency of drug resistance inS. typhi murium are: (1) the rapid spread of the use of tetracycline for therapeutic, prophylactic and nutritive purposes, and (2) the possibility of an episome-mediated transfer of drug resistance from relatively harmless intestinal bacteria, such asE. coli, toS. typhi murium.     

Incidence of resistance to ampicillin,chloramphenicol, kanamycin and tetracycline amongSalmonella species isolated in The Netherlands in 1972, 1973 and 1974

The resistance ofSalmonellae to drugs has been studied in the Netherlands since 1958. In 1972, 1973, and 1974 respectively, 14241, 13086, and 22927 strains were tested for resistance to ampicillin, chloramphenicol, kanamyci and tetracycline. From 1973 all strains were also tested for resistance to trimethoprim. In the period covered, the yearly incidence of resistance to at least one of the above drugs ranged from 39.2% to 45.6% of all strains obtained from various sources (humans, animals, animal products, sewage, etc.). A new finding in the period 1972 to 1974 was that many multiply resistant strains emerged inS. typhimurium and inS. dublin isolated from calves and cattle. In 1974, 64.4% of all strains ofS. typhimurium from these animals appeared to be resistant to ampicillin, tetracycline, chloramphenicol and kanamycin, and 25.5% of those ofS. dublin were found to be resistant to chloramphenicol and tetracycline. Of all strains ofSalmonellae examined in 1973 and 1974 respectively, 0.15 and 0.22% were resistant to trimethoprim, the main component of the twin-drug cotrimoxazol. Of the 142 strains ofS. typhi isolated in 1972 to 1974 two were resistant to tetracycline only, and one was resistant to all four antibiotics. The others had a normal susceptibility pattern.     

Incidence of resistance to ampicillin,chloramphenicol, kanamycin,tetracycline and trimethoprim of Salmonella strains isolated in The Netherlands during 1975–1980

From 1975–1980, about 130 000 Salmonella strains isolated from various sources were tested for resistance to ampicillin, chloramphenicol, kanamycin, tetracycline and trimethoprim. Following the ban on incorporation of tetracycline in animal feeds for nutritive purposes, tetracycline resistance in S. typhimurium and S. panama strains of porcine origin dropped from about 90% in 1974 for both species, to about 34% and 1%, respectively, in 1980. The incidence of resistance in human strains concurrently decreased from about 80% in 1974 to 25% and 1%, respectively, in 1980.The build-up of multiple resistance in bovine S. dublin and S. typhimurium strains, already started in 1973–1974, has continued. Recently, phage type 193 S. typhimurium strains have become predominant and they are invariably resistant to ampicillin, chloramphenicol, tetracycline, kanamycin, neomycin, streptomycin, sulphonamide and trimethoprim. Up to now, type 193 strains were hardly encountered in human patients, but the number of human isolates is slowly increasing.A fairly large number of multiply resistant strains belonging to S. oranienburg, S. schwarzengrund, S. typhimurium and, recently, S. krefeld have been isolated from adoptive children from the Far East.     

Incidence of resistance to tetracycline,chloramphenicol and ampicillin amongSalmonella species isolated in the Netherlands in 1969, 1970 and 1971

In 1969, 1970 and 1971 respectively, 11761, 13844 and 20053Salmonella strains were screened for resistance to ampicillin, chloramphenicol and tetracycline. It was found that in these years respectively 23.4%, 19.3% and 15.1% of the isolated strains were resistant to one or more of these antibiotics. Most strains appeared to be only tetracycline-resistant. Resistance to chloramphenicol remained low (0.56% and less). During 1971 64 kanamycin-resistant strains (0.32%) were isolated. Resistance was largely confined toS. typhimurium andS. panama.     

Incidence of resistance to tetracycline,chloramphenicol and ampicillin amongSalmonella species isolated in The Netherlands in 1965 and 1966

In 1965 and 1966 respectively 9628 and 10467Salmonella strains were screened for resistance to tetracycline and chloramphenicol. In 1965 the major half of the strains were also tested for ampicillin resistance and in 1966 all strains passed this test. In 1965 20.9% and in 1966 21.7% were found resistant, mainly to tetracycline. The incidence of resistance to chloramphenicol remained low (less than 1%). By far the majority of the resistant strains belonged toS. typhi murium andS. panama. The rate of resistance in the former organism remained nearly equal to that observed in 1963 – 1964, whereas inS. panama it has diminished.Ampicillin-resistant strains were found in as many as 23 different types ofSalmonella. In 8 types in which ampicillin resistance was found, only animal strains were concerned. These findings may represent cases of primary ampicillin resistance. In the human strains ofSalmonella the incidence of ampicillin resistance increased from 11.6% in 1965 to 15.3% in 1966.     

Frequency of resistance to chloramphenicol and tetracyclines among 12014Salmonella strains isolated in 1958 and 1959

Summary In the course of 1958 and 1959 12014Salmonella strains were collected and tested for antibiotic susceptibility. 250 or 2.08 per cent of these strains were found resistant to tetracycline, to chloramphenicol or both antibiotics. In the majority of cases it could be established that resistance was due to the application of these drugs in therapeutic or prophylactic doses.     

Resistance of Salmonellae Isolated in 1959 and 1960 to Tetracyclines and Chloramphenicol

The resistance of cultures of Salmonella typhimurium to tetracyclines and chloramphenicol has been examined periodically. Although none of 200 cultures isolated prior to 1948 was resistant to the antibiotics, 5% of 100 cultures from man and 9% of 100 cultures from fowls which were isolated in 1956 and 1957 were resistant to tetracyclines. Among 158 cultures isolated from man and 100 cultures isolated from fowls in 1959 and 1960, 13.9 and 29%, respectively, were resistant to tetracyclines. In the last series, cultures resistant to chloramphenicol were found for the first time. Among 150 cultures of other Salmonella serotypes from man and 137 similar cultures isolated from fowls in 1959 and 1960, 5.3 and 8%, respectively, were found resistant to tetracyclines. There is no obvious explanation for the higher percentage of resistant strains occurring in S. typhimurium than in other serotypes.     

Incidence of resistance to chloram-phenicol and tetracyclines among 11981Salmonella strains isolated in 1960

Summary The incidence of resistance to tetracycline and chloramphenicol amongSalmonella strains, which had been 2.08% in the years 1958 and 1959, dropped to 1.29% in 1960, in spite of the greatly increased use of tetracyclines in cattle-feeds in that year. It is therefore suggested that the resistance to antibiotics found amongSalmonella strains is practically entirely due to the therapeutic use of these drugs.     

Drug resistance in Salmonellae isolated at Chandigarh (India) during 1972–1978

A total of 1316 strains of Salmonella belonging to 20 serotypes isolated at P.G.I. Chandigarh (India) were tested for drug resistance. Drug resistance was noticed in 494 (38.3%) of the strains; 194 (14.8%) of these strains were resistant to one drug, while 300 (23.5%) had multiple drug resistance. All isolated strains were sensitive to gentamicin, furazolidone and nalidixic acid.Resistance to streptomycin was observed in 233 (17.7%), chloramphenicol 197 (14,9%), tetracycline 293 (22.3%), ampicillin 428 (32.5%), kanamycin 206 (15.7%), neomycin 206 (15.7%) and sulphadiazine 215 (19.9%).Multiple drug resistance was most common in S. bareilly, S. typhimurium and S. anatum serotypes. Increase in incidence of drug resistance in Salmonellae has been noticed during 1972–1978.     

Incidence of resistance to tetracycline,chloramphenicol and ampicillin amongSalmonella species isolated in the Netherlands in 1967 and 1968

In 1967 and 1968 respectively 10450 and 8665Salmonella strains were screened for resistance to ampicillin, chloramphenicol and tetracycline. It was found that in 1967, 17.8% and in 1968, 14.6% of the isolated strains were resistant to one or more antibiotics. Most strains appeared to be only tetracycline-resistant. Strains from human sources that were only ampicillin-resistant increased from 0.8 % in 1965 to 3.2% in 1967, and then decreased in 1968 to 1.3%. Resistance to chloramphenicol remained low (1.4% and lower).     

Antimicrobial resistance among Salmonella serovars isolated from different sources in Brazil during 1978–1983

A total of 748 Salmonella strains (97 serovars) isolated from human (291), animal (119), environmental (141), food (102) and animal feed (95) sources were examined for resistance to 9 antimicrobial agents. Most of the human isolates were from hospitalized patients (282). An overall resistance rate of 98.8% was determined with 100% for human and environmental isolates. Resistance to sulfadiazine (87.7%) was most common, followed by streptomycin (61.2%), ampicillin (39%) and trimethoprim-sulphamethoxazole (37.9%). Fifty one different resistance patterns were identified with Su (164 strains), Su-Sm (122) and Su-Sm-Tc-Cm-Km-Ap-Nx-Gm-Tm (95) predominating, the latter occurring only in human isolates. Multiple resistance was most frequently found among human isolates, particularly in S. derby and S. typhimurium strains. The relationship between antibiotic resistance, serovar and source of isolation of the Salmonella strains is discussed.     

Radiation resistance ofSalmonella

Summary The ionizing radiation resistances of sixSalmonella species were examined. The experimental variables were the suspending medium, the presence or absence of air, and the temperature during the irradiation process.S. typhimurium ATCC 14028,S. enteritidis ATCC 9186,S. newport ATCC 6962,S. dublin ATCC 15480,S. anatum ATCC 9270, andS. arizonae ATCC 29933 were suspended in phosphate buffer (0.1 M, pH 7.0), brain heart infusion broth (BHI) or mechanically deboned chicken and exposed to gamma radiation from cesium-137 at 0.12 kGy per min. The radiation resistance of theSalmonella increased approximately two-fold when assayed in sterile mechanically deboned chicken rather than in buffer or BHI. The average radiation (0.30 to 1.20 kGy) D-value for all sixSalmonella strains was 0.56 kGy in mechanically deboned chicken.S. enteritidis was significantly more resistant to ionizing radiation than the other five strains ofSalmonella tested on mechanically deboned chicken. The temperature of irradiation but not the presence or absence of air significantly influenced the survival ofS. typhimurium andS. enteritidis in mechanically deboned chicken. Treatment of chicken meat with ionizing radiation would be an effective means for control ofSalmonella contamination.     

Occurrence ofSalmonella in cold-blooded animals in Gran Canaria,Canary Islands,Spain

The occurrence ofSalmonella in endemic and subendemic species of lizard and frog of Gran Canaria,Gallotia stehlini andRana perezi, as well as captive reptiles from other regions of the world was investigated. The occurrence ofSalmonella was statistically higher in endemic and subendemic species than in captive animals (p<0.001). Seventy strains ofSalmonella were isolated.S. berta andS. grancanaria were the most frequently isolated serotypes. The study ofSalmonella in gall-bladder contents showed a high parasitation (85%), being higher inGallotia stehlini (100%) than inRana perezi (60%). None of the isolated salmonellae were resistant to tested antibiotics.     

Antimicrobial Susceptibility of Clostridium difficile from Different Sources

A total of 79 Clostridium difficile strains from healthy young and elderly adults, elderly patients without gastrointestinal disease, elderly patients receiving antibiotics without gastrointestinal complications, and elderly patients with antibiotic-associated diarrhea or pseudomembranous colitis were tested for their susceptibilities to 24 antimicrobial agents. All of the 79 strains were inhibited by low concentrations of rifampicin, metronidazole, fusidic acid, vancomycin, ampicillin, and penicillin G. The strains were highly resistant to aminoglycosides, trimethoprim, sulfamethoxazole, nalidixic acid, and cycloserine and often resistant to neomycin, cefoxitin, and cefalexin. Wide variations in the susceptibility of C. difficile strains to erythromycin, clindamycin, lincomycin, chloramphenicol, and tetracycline were found. Strains resistant to erythromycin, clindamycin, and lincomycin were more frequently found among strains isolated from elderly adults than those isolated from young adults, with particularly high frequency among strains isolated from elderly patients receiving antibiotics. None of the 23 strains isolated from healthy young adults was resistant to chloramphenicol. All of the 14 strains resistant to erythromycin, clindamycin, lincomycin, and chloramphenicol were sensitive to tetracycline and all of the 15 strains resistant to erythromycin, clindamycin, lincomycin, and tetracycline were sensitive to chloramphenicol. Only one out of 19 tetracycline-resistant strains was highly toxigenic, whereas 42 (70%) of 60 sensitive strains were highly toxigenic.     

Drug resistance in Salmonella strains isolated from domestic wastewater before and after treatment in stabilization ponds in an arid region (Marrakech,Morocco)

Some 118 Salmonella strains isolated before and after treatment in stabilization ponds were tested for antimicrobial resistance. In the treatment plant, which decreases the abundance of Salmonella by 99%, a significantly lower level of antibiotic resistance (P<0.01) was identified at the system's inflow point (19%) than at its outflow (29%). The serotypes most frequently identified as having multiple antibiotic resistance were Salmonella paratyphi B and S. typhimurium. High tetracycline resistance was observed at all sampling points, followed by resistance to ampicillin and streptomycin. Antibiotic resistance can be transferred from Salmonella to other members of the Enterobacteriaceae family, such as Escherichia coli K12; transfer frequencies in nutrient broth and filtered sewage water were 4.5×10^-4 and 7×10^-7, respectively.The authors are with the Université CADI AYYAD, Faculté des Sciences—Semlalia, Département de Biologie, Laboratoire de Microbiologie, Bd Le Prince My Abdallah, BP. S.15, Marrakech, Morocco.     

A sub-division ofSalmonella typhimurium into phage types based on the method of craigie and yen; Phages adaptable to species of the B and D group ofSalmonella; Phase adsorption as diagnostic aid

Summary and conclusions Phages were isolated which were adsorbed bySalmonella strains of groups B and D. These phages were adaptable to strains of species from these groups. The behaviour of some adaptations of these phages on strains ofS. paratyphi B has been described. A typing scheme forS. typhimurium has been established. So far, this consists of 32 types which have all been demonstrated with adaptations of a single phage.     

Antimicrobial resistance and resistance plasmids in Salmonella from Ontario, Canada.

Collections of 589 human and 204 animal strains of Salmonella isolated in Ontario during the summer of1974 were examined for susceptibility to 12 antimicrobial agents. Many isolates were found to be resistant to both chloramphenicol (12.4% of the human and 38.2% of the animal sample) and ampicillin. The chloramphenicol resistance almost always occurred in strains which were also resistant to ampicillin and was usually due to a self-transmissible plasmid with a resistance pattern of CmKmSmTc (chloramphenicol, kanamycin, streptomycin, and tetracycline) or CmTc. Ampicillin resistance in these strains was mediated by a variety of plasmids with patterns ApSu (ampicillin and sulfa drugs) and ApSmSu, many of which were nonself-transmissible. Ampicillin resistance in chloramphenicol-sensitive strains was transferable from 21% of the strains, and it was associated with resistance patterns which were different from the self-transferable ampicillin patterns from the chloramphenicol-resistance strains.     

Phenotypic and genetic characterization of multidrug-resistant <Emphasis Type="Italic">Salmonella</Emphasis> Infantis strains isolated from broiler chicken meats in Turkey

Twenty Salmonella Infantis strains resistant against kanamycin, tetracycline, neomycin, spectinomycin, sulphonamide, nalidixic acid and trimethoprim were selected for this study out of 103 Salmonella strains isolated from broiler samples collected from several markets in the Bolu and Ankara regions of Turkey. The resistance genes aadA1, aphA1, sul1, tet(A), dfrA5/dfrA14 and gyrA were determined for these multidrug-resistant S. Infantis strains. S. Infantis strains contained a mega plasmid with the molecular size of 206 kb. The strains were divided into three groups according to the pulsed field gel electrophoresis patterns of XbaI digested chromosomal DNA. A Ser83→Tyr83 point mutation was found in the gyrA gene of all quinolone-resistant isolates. Filter mating experiments showed that 206 kb plasmid transferred nalidixic acid resistance associated with class I integrons.     

Incidence of antimicrobial resistance among Enterobacteriaceae isolated in Riyadh

The antimicrobial resistance of 1,018 isolates of Enterobacteriaceae isolated from fecal specimens of the urban population of Riyadh, Saudi Arabia, was studied. Resistance to 1 or more of 10 antimicrobial agents was encountered in 50.2% of the isolates. Of the isolates tested,Escherichia coli (0.8%) andKlebsiella species (1.6%) were found resistant to seven antimicrobial agents simultaneously: ampicillin, chloramphenicol, kanamycin, colistin, streptomycin, tetracycline, and carbenicillin. Resistance to nalidixic acid was encountered in only 0.68% of theE. coli isolates. No isolate was found to be resistant to gentamicin. Eighty-six of the resistant strains were tested for their ability to transfer their resistance. Forty percent were able to do so withE. coli K-12.     

Occurrence of heterogeneous R-plasmids during two concurrent epidemics due to multidrug-resistantSalmonella oranienburg

During two different epidemics that started in August–September, 1980, 140 and 6 multidrug-resistant strains ofSalmonella oranienburg were isolated from a Children's Hospital in New Delhi (epidemic 1) and H.N. Das Hospital in Bombay (epidemic 2) respectively. Out of 140, 123 strains showed high levels of resistance to ampicillin, kanamycin, streptomycin, sulfamethoxazole, tetracycline, and trimethoprim. All six strains of epidemic 2 and two strains of epidemic 1 were also found resistant to chloramphenicol in addition to the above antibiotics. The genetic characterization of conjugative R-plasmids harbored by these strains revealed that, while strains of epidemic 1 carry a fi^–, 96 megadalton, an unclassified plasmid, the strains isolated during epidemic 2 contain a fi^–, 62 megadalton plasmid of incompatibility group I₁. All the six strains of epidemic 2 were found to produce bacteriocin of Col Ib group. Plasmid transfer studies revealed that the genes for antibiotic resistance and bacteriocin production were coded on a single plasmid of 62 megadalton. The data show the significance of detailed genetic analysis while dealing with the clonal outbreaks due to same resistant serotypes.