Antimicrobial resistance and R factors in Salmonella isolated from humans and animals in Georgia and South Carolina.

Three hundred and five strains of Salmonella isolated from humans and 152 strains isolated from animals in Georgia and South Carolina during 1973 were examined for resistance to 14 antimicrobial agents. S typhimurium was the most frequently isolated serotype (30% of human isolates and 13% of animal isolates). The overall incidence of antimicrobial resistance was 16% in human starins and 21% in animal strains. The most commonly found resistance were to streptomycin (11% in human strains and 16% in animal strains) and tetracycline (10% in both human and animal isolates). A higher prevalence of resistance to streptomycin, spectinomycin, and nitrofurantoin, which are currently used primarily in veterinary medicine, was found in animal Salmonella. Conversely, resistance to ampicillin, cephalothin, and kanamycin, which are used mainly in human medicine, was found more frequently in human Salmonella. No resistance to nalidixic acid, gentamicin, tobramycin, rifampin, or trimethoprim was detected. Sixty-five percent of resistant strains from humans and 60% of resistant strains from animals transferred their resistance patterns partially or in toto.     

Antimicrobial susceptibility patterns of thermophilic Campylobacter spp. from humans, pigs, cattle, and broilers in Denmark.

The MICs of 16 antimicrobial agents were determined for 202 Campylobacter jejuni isolates, 123 Campylobacter coli isolates, and 6 Campylobacter lari isolates from humans and food animals in Denmark. The C. jejuni isolates originated from humans (75), broilers (95), cattle (29), and pigs (3); the C. coli isolates originated from humans (7), broilers (17), and pigs (99); and the C. lari isolates originated from broilers (5) and cattle (1). All isolates were susceptible to apramycin, neomycin, and gentamicin. Only a few C. jejuni isolates were resistant to one or more antimicrobial agents. Resistance to tetracycline was more common among C. jejuni isolates from humans (11%) than among C. jejuni isolates from animals (0 to 2%). More resistance to streptomycin was found among C. jejuni isolates from cattle (10%) than among those from humans (4%) or broilers (1%). A greater proportion of C. coli than of C. jejuni isolates were resistant to the other antimicrobial agents tested. Isolates were in most cases either coresistant to tylosin, spiramycin, and erythromycin or susceptible to all three antibiotics. More macrolide-resistant isolates were observed among C. coli isolates from swine (79%) than among C. coli isolates from broilers (18%) and humans (14%). Twenty-four percent of C. coli isolates from pigs were resistant to enrofloxacin, whereas 29% of C. coli isolates from humans and none from broilers were resistant. More resistance to streptomycin was observed among C. coli isolates from swine (48%) than among C. coli isolates from broilers (6%) or humans (0%). The six C. lari isolates were susceptible to all antimicrobial agents except ampicillin and nalidixic acid. This study showed that antimicrobial resistance was found only at relatively low frequencies among C. jejuni and C. lari isolates. Among C. coli isolates, especially from swine, there was a high level of resistance to macrolides and streptomycin. Furthermore, this study showed differences in the resistance to antimicrobial agents among Campylobacter isolates of different origins.     

Antibiotic resistance in Campylobacter strains isolated from animals, foods, and humans in Spain in 1997-1998

Colonization by Campylobacter strains was investigated in human, broiler, and pig fecal samples from 1997-1998, as well as in foods of animal origin, and antibiotic susceptibility testing was carried out for these strains. Campylobacter strains were isolated in the foods of animal origin (55 of 101 samples; 54.4%), intestinal samples from broilers (85 of 105; 81%), and pigs (40 of 45; 88.9%). A total of 641 Campylobacter strains were isolated from 8,636 human fecal samples of clinical origin (7.4%). Campylobacter jejuni was the most frequently isolated species from broilers (81%) and humans (84%), and Campylobacter coli was most frequently isolated from pigs (100%). An extremely high frequency of ciprofloxacin resistance was detected among Campylobacter strains, particularly those isolated from broilers and pigs (99%), with a slightly lower result for humans (72%); cross-resistance with nalidixic acid was almost always observed. A higher frequency of resistance to erythromycin (81.1%), ampicillin (65.7%), gentamicin (22.2%), and amikacin (21.6%) was detected in C. coli strains isolated from pigs compared to those isolated from humans (34.5, 29.3, 8.6, and 0%, respectively). A low frequency of erythromycin resistance was found in C. jejuni or C. coli isolated from broilers. A greater resistance to ampicillin and gentamicin (47.4 and 11.9%, respectively) was detected in C. jejuni isolated from broilers than in human strains (38 and 0.4%, respectively). Beta-lactamase production was found in 81% of the Campylobacter strains tested, although 44% of them were characterized as ampicillin susceptible. The increasing rates of Campylobacter resistance make advisable a more conservative policy for the use of antibiotics in farm animals.     

Tetracycline resistance of Australian Campylobacter jejuni and Campylobacter coli isolates

OBJECTIVES: Tetracycline resistance in Campylobacter is encoded by the tet(O) gene and is usually associated with conjugative plasmids. Little was known about tetracycline resistance in Australian Campylobacter species, therefore we investigated this resistance in 41 Campylobacter jejuni and five Campylobacter coli strains from humans and healthy chickens. METHODS: Tetracycline MICs were determined for each isolate using an agar dilution method. The distribution and localization of tet(O) on plasmid and chromosomal DNA was determined by Southern-blot experiments. The ability to transfer resistance to recipient strains was examined through conjugation studies. Identity of transconjugants was confirmed by PCR and flaA-restriction fragment length polymorphism analysis. RESULTS: High-level tetracycline resistance was observed, ranging from 32 to >256 mg/L. Plasmids were detected in 74% of isolates with plasmids between 30 and 40 kb in size most frequently isolated. tet(O) was present in all tetracycline-resistant isolates. In the majority of strains under study the tet(O) gene was chromosomally encoded. Tetracycline resistance of six C. jejuni strains in which tet(O) was plasmid mediated was transferred by conjugation to a C. jejuni recipient strain. Transfer did not occur between tetracycline-resistant C. jejuni strains and a C. coli recipient. No difference in MICs, plasmid carriage and tet(O) localization was detected between human and chicken isolates. CONCLUSIONS: These data indicate that the tet(O) gene, previously reported in Campylobacter strains throughout the world, is present in Australian Campylobacter. This study will lead to a greater understanding of antibiotic resistance distribution in Campylobacter spp. in Australia.     

Antimicrobial resistance in Campylobacter strains isolated from French broilers before and after antimicrobial growth promoter bans

OBJECTIVES: The antimicrobial susceptibility of Campylobacter strains isolated from standard and free-range broilers in 1992-1996 and 2001-2002 was studied. METHODS: Strains were isolated from caeca or skin samples collected from standard or free-range broilers arriving in slaughterhouses. The MICs of ampicillin, nalidixic acid, enrofloxacin, tetracycline, erythromycin and gentamicin were determined by agar dilution and compared according to species (Campylobacter jejuni or Campylobacter coli), production system and sampling period. RESULTS: Results showed that all chickens harboured Campylobacter. An increase over time of the C. coli/C. jejuni ratio for standard chickens occurred. A wide range of MICs was observed among isolates from the same broiler or from the same farm. Strains collected on entry to the slaughterhouse and after storage showed no significant difference in their antibiotic resistance. C. coli was more resistant than C. jejuni to tetracycline and erythromycin during the first period and to all tested molecules (except gentamicin) during the second period. Strains isolated from standard chickens were also more often resistant than those isolated from free-range broilers. The percentage of C. jejuni strains resistant to ampicillin decreased from 1992-1996 to 2001-2002, whereas no change could be observed for the other antimicrobial agents. However, for C. coli the resistance to ampicillin, nalidixic acid, enrofloxacin, tetracycline and erythromycin significantly increased. CONCLUSION: There was an increase in the incidence of antibiotic resistance of C. coli between 1992-1996 and 2001-2002.     

Antibiotic resistance in salmonellae isolated from humans and animals in France: comparative data from 1994 and 1997

Among 25526 recorded isolates of salmonellae, 5086 isolated from humans and 20440 from animals in 1994 and 1997 in France, the antibiotic resistance phenotype was determined for all human and 5336 animal isolates. In Salmonella enterica serovar typhimurium, one of the two most frequently isolated serovars from humans as well as animals, resistance to ampicillin was observed in 61% of both human and animal isolates in 1994 and in 73% of human and 53% of animal isolates in 1997. During these periods, resistance to co-amoxiclav was between 45% and 66% for both types of isolate. Resistance to ampicillin was associated with resistance to streptomycin, spectinomycin, sulphonamide, tetracycline and chloramphenicol in over 70% of isolates. Resistance to ampicillin as well as co-amoxiclav never exceeded 7% in Salmonella enteritidis. While Salmonella hadar was practically absent among the human isolates in 1994, this serovar was the third most frequent in 1997, and at that time 92% were resistant to nalidixic acid. Among the animal S. hadar isolates, the prevalence of resistance to nalidixic acid increased from 3% in 1994 to 72% in 1997. None of these isolates manifested high-level resistance to ofloxacin. The levels of resistance to aminoglycosides (< or =3%) and trimethoprim-suphamethoxazole (< or =14%) remained practically unchanged in all three serovars. The resistance markers of 463 ampicillin-resistant S. typhimurium isolated in 1997 were determined. Among the 24 phenotypes observed, six multiresistance phenotypes, representing 82% of these isolates (as compared with 80% in 1994), were associated with the PSE-1 gene typically found in the lysotype DT104 of this serovar.     

Susceptibility studies of multiply resistant Haemophilus influenzae isolated from pediatric patients and contacts

From February 1981 to December 1983, 225 strains were isolated from pediatric patients infected with Haemophilus influenzae. Forty-one strains were found to be resistant to ampicillin, chloramphenicol, and other antibiotics. They were isolated from 20 patients with invasive diseases (meningitis, 16; bacteremia, 4) and 21 with noninvasive diseases (otitis media, 19; conjunctivitis, 2). During this period, 44 patients with invasive diseases were seen (meningitis, 28; bacteremia, 16). Strains resistant to both ampicillin and chloramphenicol occurred in 45.4% of cerebrospinal fluid and blood isolates and in 51% of cerebrospinal fluid isolates only. In this group, individual resistance to ampicillin was 50%; chloramphenicol, 52.2%; tetracycline, 54.5%; and sulfamethoxazole-trimethoprim, 63.6%. No epidemiological relationship could be found among the patients. The presence of asymptomatic carriers was investigated in two nurseries and in eight family groups. From a total of 125 individuals studied, 80 were found to be colonized by H. influenzae, and 36 carried multiply resistant strains. From patients and carriers, 77 strains were found to be resistant to ampicillin, chloramphenicol, and other drugs; 39 belonged to type b (cerebrospinal fluid, 16; blood, 4; ear, 7; and nasopharynx, 12), and 38 were non-type b. The most frequent pattern of resistance was ampicillin-chloramphenicol-tetracycline-sulfamethoxazole-trimethoprim (94.8%), followed by ampicillin-chloramphenicol-tetracycline (3.9%). The disk diffusion method correctly predicted multiple resistance. The mean inhibition zone diameters were: ampicillin, 12.8 mm; chloramphenicol, 15.2 mm; tetracycline, 9.9 mm; and sulfamethoxazole-trimethoprim, 10.8 mm. These resistant strains were susceptible to cefotaxime, moxalactam, cefoperazone, cefuroxime, rifampin, and gentamicin. Our data suggest that in Spain the resistance of H. influenzae to ampicillin and chloramphenicol is endemic and that other effective therapeutic modalities are needed.     

Antibiotic resistance in Campylobacter jejuni and Campylobacter coli isolated from poultry in the South-East Queensland region

OBJECTIVES: The aim of this study was to determine the antimicrobial resistance patterns of 125 Campylobacter jejuni and 27 Campylobacter coli isolates from 39 Queensland broiler farms. METHODS: Two methods, a disc diffusion assay and an agar-based MIC assay, were used. The disc diffusion was performed and interpreted as previously described (Huysmans MB, Turnidge JD. Disc susceptibility testing for thermophilic campylobacters. Pathology 1997; 29: 209-16), whereas the MIC assay was performed according to CLSI (formerly NCCLS) methods and interpreted using DANMAP criteria. RESULTS: In both assays, no C. jejuni or C. coli isolates were resistant to ciprofloxacin or chloramphenicol, no C. coli were resistant to nalidixic acid, and no C. jejuni were resistant to erythromycin. In the MIC assay, no C. jejuni isolate was resistant to nalidixic acid, whereas three isolates (2.4%) were resistant in the disc assay. The highest levels of resistance of the C. jejuni isolates were recorded for tetracycline (19.2% by MIC and 18.4% by disc) and ampicillin (19.2% by MIC and 17.6% by disc). The C. coli isolates gave very similar results (tetracycline resistance 14.8% by both MIC and disc; ampicillin resistance 7.4% by MIC and 14.8% by disc). CONCLUSIONS: This work has shown that the majority of C. jejuni and C. coli isolates were susceptible to the six antibiotics tested by both disc diffusion and MIC methods. Disc diffusion represents a suitable alternative methodology to agar-based MIC methods for poultry Campylobacter isolates.     

Plasmid characterization of Shigella spp. isolated from children with shigellosis and asymptomatic excretors

Strains of Shigella dysenteriae type 1 and Sh. flexneri isolated during 1981-82 from children with shigellosis and also from asymptomatic excretors were examined for drug resistance and for the presence of plasmids. Shigella strains isolated from dysenteric children showed multiple plasmid bands. Thirty-eight percent of the strains transferred the drug resistance factor(s), either partially or fully to a recipient Escherichia coli K12 strain. Plasmids in the molecular weight range from between 44-76 Mdal were correlated with drug resistance. It was found that multi-resistant clinical isolates generally harbour a single large transmissible plasmid. Strains isolated from asymptomatic excretors demonstrated plasmid patterns different from those isolated from children with shigellosis although the bands were relatively homogeneous within each group. Both the groups showed the presence of a 140 Mdal plasmid band conferring invasiveness and such strains gave a positive Sereny test. This study thus shows that Shigella strains from asymptomatic excretors also retain invasiveness.     

Nosocomial Multiply Resistant Klebsiella pneumoniae: Epidemiology of an Outbreak of Apparent Index Case Origin

A nosocomial epidemic of multiply resistant (MR) Klebsiella pneumoniae characterized by resistance to gentamicin, tobramycin, kanamycin, cephalothin, chloramphenicol, and ampicillin occurred in a Veterans Administration hospital from 1975 to 1977. A total of 66 infected or colonized patients were observed in a 2-year period; there were 43 urinary tract infections, 13 wound or soft tissue infections, 8 pneumonias, and 6 patients with only asymptomatic stool colonization. Four patients had both pneumonia and a urinary tract infection. There were five secondary bacteremias. The majority of MR K. pneumoniae strains were type 30, but types 17, 21, and 23 and nontypable organisms were also recovered. Other gram-negative bacilli with the same antibiotic resistance pattern were isolated from 14 patients. Seven MR K. pneumoniae and three resistant Escherichia coli isolates were shown to transfer resistance to E. coli K-12. MR K. pneumoniae-infected patients were seriously ill, had long hospitalization times (mean, 67 days), and were in close geographic proximity to other cases. Compared with controls, cases more frequently had prior antibiotic treatment and urinary catheters, but not respiratory instrumentation, nasogastric tubes, or antacid treatment. The apparent source of the outbreak was traced to an index case who entered the hospital with an MR K. pneumoniae urinary tract infection. Asymptomatic gastrointestinal carriage without infection elsewhere was infrequent (1.6% of cultured patients), but 78% of patients with MR K. pneumoniae infections at other sites also had the organism in their stools. Hospital antibiotic usage was unchanged before and during the outbreak. The identification of an index case and relative lack of asymptomatic stool carriers are unique features of this plasmid-mediated MR K. pneumoniae epidemic. Although this MR K. pneumoniae outbreak appeared to be controlled by the use of isolation techniques, a simultaneous increase in gentamicin resistance among other gram-negative organisms was observed.     

Relation of Beta-Lactamase Activity to Antimicrobial Susceptibility in Serratia marcescens

One-hundred clinical isolates of Serratia marcescens were tested for susceptibility to cephalothin, carbenicillin, ticarcillin, ampicillin, and cefoxitin. The majority of the 100 isolates (≥70%) were susceptible to carbenicillin, ticarcillin, and cefoxitin; less than one-half were susceptible to ampicillin; none were susceptible to cephalothin. Ten isolates from the 100 organisms tested were selectively assayed for their β-lactamase activity. Enzyme activity was measured using either iodometric or spectrophotometric methods, and the microbiological assay technique. It was concluded that β-lactamase production was not the sole determinant in β-lactam antibiotic resistance. Resistance without demonstrable β-lactamase was evident in strains for cephalothin, ampicillin, and cefoxitin. In addition, one strain which was susceptible to all antibiotics except cephalothin, elaborated considerable β-lactamase activity.     

Antibiotic resistance and small R plasmids among Escherichia coli isolates from outpatient urinary tract infections in northern Norway.

Escherichia coli strains from outpatient urinary tract infections in northern Norway over a period of 1 year were examined for resistance to nine commonly used antibiotics. Strains collected during 4.5 months were examined for R plasmid content by using conjugation and in vitro transformation. Of the E. coli strains, 42% were resistant to one or more antibiotics. Resistance was highest to sulfonamide (20.8% of all strains), nitrofurantoin (14.5%), and tetracycline (10.1%), whereas less than 6% of the strains were resistant to ampicillin, carbenicillin, cephalothin, nalidixic acid, or trimethoprim-sulfamethoxazole. No strain was resistant to gentamicin. Tetracycline resistance was more common in men than in women. Resistance to cephalothin, nalidixic acid, and sulfonamide was higher in strains from older people. Resistance to sulfonamide was more frequent in the urban community. These was no seasonal variation in antibiotic resistance, although the incidence of urinary tract infection varied with seasons. Plasmid-determined resistance to ampicillin, streptomycin, sulfonamide, and tetracycline was found. About 18% of the resistant strains from the urban municipality carried R plasmids, most of which were small plasmids mediating resistance to sulfonamide and streptomycin. The overall frequency of resistance in strains collected from rural areas was similar to the urban frequency, but in the rural strains, R plasmids were found in only 5% of the resistant strains.     

Multidrug-resistant urinary tract isolates of Escherichia coli: prevalence and patient demographics in the United States in 2000

Concurrent resistance to antimicrobials of different structural classes has arisen in a multitude of bacterial species and may complicate the therapeutic management of infections, including those of the urinary tract. To assess the current breadth of multidrug resistance among urinary isolates of Escherichia coli, the most prevalent pathogen contributing to these infections, all pertinent results in The Surveillance Network Database-USA from 1 January to 30 September 2000 were analyzed. Results were available for 38,835 urinary isolates of E. coli that had been tested against ampicillin, cephalothin, ciprofloxacin, nitrofurantoin, and trimethoprim-sulfamethoxazole. Of these isolates, 7.1% (2,763 of 38,835) were resistant to three or more agents and considered multidrug resistant. Among the multidrug-resistant isolates, 97.8% were resistant to ampicillin, 92.8% were resistant to trimethoprim-sulfamethoxazole, 86.6% were resistant to cephalothin, 38.8% were resistant to ciprofloxacin, and 7.7% were resistant to nitrofurantoin. The predominant phenotype among multidrug-resistant isolates (57.9%; 1,600 of 2,793) included resistance to ampicillin, cephalothin, and trimethoprim-sulfamethoxazole. This was the most common phenotype regardless of patient age, gender, or inpatient-outpatient status and in eight of the nine U.S. Bureau of the Census regions. Rates of multidrug resistance were demonstrated to be higher among males (10.4%) than females (6.6%), among patients > 65 years of age (8.7%) than patients < or = 17 (6.8%) and 18 to 65 (6.1%) years of age, and among inpatients (7.6%) than outpatients (6.9%). Regionally, the rates ranged from 4.3% in the West North Central region to 9.2% in the West South Central region. Given the current prevalence of multidrug resistance among urinary tract isolates of E. coli in the United States (7.1%), continued local, regional, and national surveillance is warranted.     

Multidrug resistance in Campylobacter jejuni strains collected from Finnish patients during 1995-2000

OBJECTIVES: The resistance of Campylobacter jejuni to fluoroquinolones is increasing globally. This study was performed to delineate those antimicrobial agents that are effective in vitro against ciprofloxacin-resistant C. jejuni isolates and potentially suitable for the treatment of severe disease when fluoroquinolone resistance or multidrug resistance is known or suspected. METHODS: During 1995-2000 we collected 376 C. jejuni strains, of which 354 were of foreign origin from multiple countries and 22 were of domestic origin. The MICs of 12 antimicrobial agents against the isolates were determined. RESULTS: Of the 376 strains, 174 (46%) were resistant to ciprofloxacin. Among other antimicrobials, resistance was most common to tetracycline (46%) and ampicillin (17%). Of the ciprofloxacin-resistant strains, 68% and 25%, respectively, were resistant to tetracycline and ampicillin, and 3% were resistant to erythromycin, gentamicin or clindamycin. One (0.6%) ciprofloxacin-resistant isolate was resistant to co-amoxiclav and none was resistant to imipenem. Resistance to three or more antimicrobial groups was detected in 22% of the isolates. Multidrug resistance was significantly associated with ciprofloxacin resistance (33% versus 12%; P<0.01). Eight (2%) strains were resistant to macrolides, of which 75% were also resistant to ciprofloxacin, but none was resistant to co-amoxiclav or imipenem. CONCLUSIONS: Macrolides still appear to be the first-choice alternative for suspected C. jejuni enteritis, if antimicrobial treatment is needed. The in vitro susceptibilities suggest that clinical trials to treat enteritis caused by multidrug-resistant C. jejuni with co-amoxiclav, and life-threatening infections with a carbapenem, may be valuable.     

Antimicrobial susceptibility of Salmonella isolated from cattle, swine and poultry (2001-2002): report from the Japanese Veterinary Antimicrobial Resistance Monitoring Program

OBJECTIVES: The Japanese Veterinary Antimicrobial Resistance Monitoring (JVARM) Program was established in 1999 to examine the susceptibility of bacteria from food-producing animals to antimicrobial agents. This study tested the susceptibility of Salmonella isolates collected during 2001-2002 to 20 antimicrobials.Materials and methods: MICs of antimicrobial agents were determined using the NCCLS agar dilution method, and interpreted according to breakpoints obtained from the bimodal MIC distributions. RESULTS: A total of 82 Salmonella were isolated from food-producing animals and tested for antimicrobial susceptibility. Isolates resistant to ampicillin, dihydrostreptomycin, kanamycin, oxytetracycline, chloramphenicol, bicozamycin, nalidixic acid, oxolinic acid and trimethoprim were obtained from healthy animals and diagnostic sample submissions. Salmonella Dublin was isolated only from cattle and showed resistance to older quinolones. Resistance to ampicillin, dihydrostreptomycin, kanamycin and oxytetracycline was common across all serotypes. Fluoroquinolone-resistant Salmonella Choleraesuis was isolated from swine and was the first Japanese report on this type of resistance in Salmonella from an animal origin. Most Salmonella Typhimurium isolates showed resistance to ampicillin, chloramphenicol, dihydrostreptomycin and oxytetracycline. S. Typhimurium DT104 accounted for 40.7% of S. Typhimurium isolates and was more often multi-drug resistant. Most Salmonella Infantis isolates from poultry showed resistance to dihydrostreptomycin, oxytetracycline, trimethoprim or kanamycin. In Salmonella Enteritidis, the major serotype isolated from food-poisoning in Japan, only resistance to dihydrostreptomycin was observed. CONCLUSIONS: This is the first JVARM report of Salmonella isolates, and continuous investigations at the national level on antimicrobial resistance in Salmonella isolated from food-producing animals will be important in the JVARM Program.     

A national surveillance of antimicrobial resistance in Escherichia coli isolated from food-producing animals in Japan

A nationwide investigation of antimicrobial susceptibility in Escherichia coli isolated from food-producing animals was performed in Japan. MICs of 18 antimicrobial agents were determined for a total of 1018 isolates. Higher resistance rates were observed against sulfadimethoxine, oxytetracycline and dihydrostreptomycin, followed by ampicillin and kanamycin. Resistance was more frequently observed among broiler isolates, followed by isolates from pigs. Almost 10% of broiler isolates were resistant to fluoroquinolones and extremely high MICs (100 mg/L) were observed. In general, antimicrobial resistance rates in E. coli have declined in recent years, with the exception of resistance to fluoroquinolones among broiler isolates, which has increased.     

A European survey of antimicrobial susceptibility among zoonotic and commensal bacteria isolated from food-producing animals

OBJECTIVE: To study antimicrobial resistance in zoonotic bacteria isolated from food animals in different countries using uniform methodology. METHODS: Samples were taken at slaughter from chickens, pigs and cattle in four EU countries per host. Escherichia coli (indicator organism; n = 2118), Salmonella spp. (n = 271) and Campylobacter spp. (n = 1325) were isolated in national laboratories and MICs tested in a central laboratory against, where appropriate, ampicillin, cefepime, cefotaxime, ciprofloxacin, chloramphenicol, erythromycin, gentamicin, nalidixic acid, streptomycin, tetracycline and trimethoprim/sulfamethoxazole. RESULTS: Isolation rates were high for E. coli, low for Salmonella and intermediate for Campylobacter. MIC results showed resistance prevalence varied among compounds, hosts and countries. For E. coli and Salmonella, resistance to newer compounds (cefepime, cefotaxime, ciprofloxacin) was absent or low, but to older compounds (except gentamicin), resistance was variable and higher. E. coli isolates from Sweden showed low resistance, whereas among isolates from Spain (pigs), resistance to ampicillin, chloramphenicol, streptomycin, tetracycline and trimethoprim/sulfamethoxazole was higher; the UK, France, the Netherlands, Germany, Italy and Denmark were intermediate. For Campylobacter spp. isolates from chickens, nalidixic acid and ciprofloxacin resistance was >30% in France and the Netherlands, >6% in the UK and zero in Sweden. Nalidixic acid resistance was high in cattle (20%-64%), whereas ciprofloxacin resistance was markedly lower in cattle, variable in pigs (3%-21%) and highest in Sweden. Generally, Campylobacter coli was more resistant than Campylobacter jejuni. CONCLUSION: Antimicrobial resistance among enteric organisms in food animals varied among countries, particularly for older antimicrobials, but resistance to newer compounds used to treat disease in humans was generally low.     

Physical Characterization of Ten R Plasmids Obtained from an Outbreak of Nosocomial Klebsiella pneumoniae Infections

Gentamicin resistance in Klebsiella pneumoniae involved in an outbreak at the Minneapolis Veterans Administration Hospital was due to a transmissible R plasmid. In addition to gentamicin, this plasmid conferred resistance to tobramycin, kanamycin, ampicillin, carbenicillin, cephalothin, chloramphenicol, and sulfathiazole. R plasmids which transferred this complex antibiogram were identified in several clinical isolates, including four different serotypes of K. pneumoniae, Escherichia coli, Enterobacter cloacae, and Proteus morganii. The covalently closed circular form of all R plasmids isolated had a sedimentation coefficient of 76S to 77S, corresponding to a molecular weight of 58 x 10(6). The possibility that a single R plasmid was responsible for the dissemination of multiple drug resistance among all of these different clinical strains was examined by characterizing the plasmids by using EcoRI restriction endonuclease. The same 15 fragments were obtained from each of the 10 plasmids analyzed. Their molecular weights ranged from 4 x 10(5) to 11 x 10(6). Thus, we conclude that each of the 10 plasmids present in the various clinical strains isolated from the hospital over a 7-month period originated from a common source and that R plasmid transfer was important in their spread.     

Survey of plasmids and resistance factors in Campylobacter jejuni and Campylobacter coli.

A total of 688 isolates of Campylobacter jejuni and Campylobacter coli were screened for the presence of plasmid DNA by agarose gel electrophoresis and were tested for susceptibility to ampicillin, chloramphenicol, erythromycin, streptomycin, and tetracycline. Of the isolates examined, 32% were noted to harbor plasmid DNA, ranging in size from 2.0 to 162 kilobases. Only tetracycline resistance was noted to correlate with the presence of plasmids. Plasmids capable of transferring tetracycline resistance via conjugation ranged in size from 42 to 100 kilobases. The Bg/II and Bc/I restriction endonuclease profiles of 31 plasmids examined showed marked diversity in their banding patterns. Although a high degree of DNA-DNA homology was noted among the Campylobacter spp. plasmids, no homology was noted between these plasmids and tetracycline R factors commonly found in the family Enterobacteriaceae.     

Identification and Expression of Cephamycinase blaCMY Genes in Escherichia coli and Salmonella Isolates from Food Animals and Ground Meat

Twenty-one Salmonella and 54 Escherichia coli isolates, recovered from food animals and retail ground meats, that exhibited decreased susceptibilities to ceftiofur and ceftriaxone were shown to possess a bla(CMY) gene. The bla(CMY-4) gene was identified in an E. coli isolate recovered from retail chicken and was further shown to be responsible for resistance to cephalothin, ampicillin, and amoxicillin-clavulanic acid and elevated MICs of ceftriaxone, cefoxitin, and ceftiofur.