Multiple drug resistance in Pasteurella multocida and Pasteurella haemolytica from cattle and swine.

The results of antimicrobial susceptibility testing on 262 strains of Pasteurella multocida and 141 strains of Pasteurella haemolytica isolated from cattle and swine from 1971 to 1974 were analyzed for patterns of resistance to streptomycin, penicillin, tetracycline, and chloramphenicol, using a modified Kirby-Bauer procedure. Resistance was recorded for 80.5% of the isolants of P multocida and 92.2% of those of P haemolytica. Resistance to streptomycin was most frequent, followed by resistance to penicillin and tetracycline. Most cultures of P multocida and P haemolytica were susceptible to chloramphenicol. There were 9 patterns of resistance with the aforementioned antibiotics. The combinations, streptomycin and penicillin and streptomycin and tetracycline, each accounted for approximately 10% of the resistance patterns of P multocida. Approximately half of the 14 isolants of P haemolytica were resistant to the combination of streptomycin, penicillin, and tetracycline. These observations underscore the need for antimicrobial susceptibility testing of clinical isolants of P multocida and P haemolytica.     

Anti‐microbial Susceptibility of Streptococcus spp. Isolated from Bovine Mastitis in Argentina

The in vitro susceptibility to penicillin G, erythromycin and clindamycin was determined by the disc diffusion test and by E‐test for a total of 47 streptococcal strains (three Streptococcus uberis, 36 Streptococcus agalactiae, eight Streptococcus dysgalactiae spp. dysgalactiae) isolated from bovine intramammary infections in Argentina. Moreover, resistance phenotypes of erythromycin‐resistant streptococcal isolates was characterized. MIC₉₀ of penicillin G, erythromycin and clindamycin for S. agalactiae were 0.75, 8.0 and 12.0 μg/ml respectively. Resistance to erythromycin and clindamycin was detected in 13 (27.6%) and 12 (25.5%) isolates respectively. No isolate was resistant to penicillin G. Resistance against macrolides, lincosamides and streptogramin B (MLS_B) represented by the constitutive MLS_B phenotype was present in 11 (23.4%) erythromycin‐resistant isolates and two isolates (4.3%) expressed the M phenotype. The inducible MLS_B phenotype was not identified. Results suggest that beta‐lactams are the first‐line antibiotics when treating streptococcal udder infections; however, the continuous monitoring of the antibiotic resistance is essential, as the emergence of resistant strains has become a growing concern on the therapy of bovine mastitis.     

The antimicrobial susceptibility of Staphylococcus species isolated from canine dermatitis

In a retrospective study, 1538 strains of -haemolysin-producing Staphylococcus species isolated from dermatitis in dogs at three veterinary clinical microbiology laboratories in Norway during 1986–87 and 1993–94 were investigated for their antimicrobial susceptibility. None of the strains was resistant to cloxacillin, cephalexin or the quinolones enrofloxacin and ciprofloxacin. More than 96% of the strains were susceptible to trimethoprim-sulphonamide, bacitracin and fucidic acid. Between 67% and 89% of the strains were susceptible to erythromycin, lincosamides, tetracycline, neomycin and chloramphenicol. Only 37.9% of the strains were susceptible to penicillin. The frequency of penicillin resistance increased significantly between the first and second periods, from 46.0% to 58.6%. The frequency of resistance to lincomycin, clindamycin and erythromycin also increased significantly between the first and second periods, from 3.0%, 2.1% and 3.3% to 25.5%, 19.5% and 24.8%, respectively. A moderate increase in resistance to tetracycline was also noted, from 20.4% in the first to 27.6% in the second period. On the other hand, the frequency of resistance to trimethoprim-sulphonamide decreased significantly from 4.1% in the first to 0.9% in the second period. Many different resistance patterns were observed in each period. However, the proportion of multiresistant strains increased from 2.1% in the first to 10.2% in the second period. There was a decrease in resistance to the combination of trimethoprim-sulphonamide and penicillin from the first to the second period. Resistance to the combination of lincosamides and pencillin increased. For the combinations penicillin-tetracycline-lincosamides, pencillin-lincosamides-erythromycin, and pencillin-tetracycline-lincosamides-erythromycin, there was a striking increase in resistance between the first and the second periods.Abbreviations CVL Central Veterinary Laboratory - NCVM Norwegian College of Veterinary Medicine - NVL Norwegian Veterinary Laboratory     

Anti-microbial susceptibility of Streptococcus spp. isolated from bovine mastitis in Argentina

The in vitro susceptibility to penicillin G, erythromycin and clindamycin was determined by the disc diffusion test and by E-test for a total of 47 streptococcal strains (three Streptococcus uberis, 36 Streptococcus agalactiae, eight Streptococcus dysgalactiae spp. dysgalactiae) isolated from bovine intramammary infections in Argentina. Moreover, resistance phenotypes of erythromycin-resistant streptococcal isolates was characterized. MIC90 of penicillin G, erythromycin and clindamycin for S. agalactiae were 0.75, 8.0 and 12.0 microg/ml respectively. Resistance to erythromycin and clindamycin was detected in 13 (27.6%) and 12 (25.5%) isolates respectively. No isolate was resistant to penicillin G. Resistance against macrolides, lincosamides and streptogramin B (MLS(B)) represented by the constitutive MLS(B) phenotype was present in 11 (23.4%) erythromycin-resistant isolates and two isolates (4.3%) expressed the M phenotype. The inducible MLS(B) phenotype was not identified. Results suggest that beta-lactams are the first-line antibiotics when treating streptococcal udder infections; however, the continuous monitoring of the antibiotic resistance is essential, as the emergence of resistant strains has become a growing concern on the therapy of bovine mastitis.     

Heterogeneity of methicillin-sensitive Staphylococcus pseudintermedius strains isolated from diseased dogs

Thirty nine canine S. pseudintermedius strains were examined for antibiotic susceptibility and genetic polymorphisms. All strains were methicillin-sensitive S. pseudintermedius (MSSP). Resistance to penicillin was most prevalent (66.6%), followed by resistance to neomycin (56.4%), erythromycin (53.8%), clindamycin (48.7%), chloramphenicol (48.7%), and tetracycline (46.2%). Pulsed-field electrophoresis (PFGE) showed a high genetic polymorphism in the investigated strains.     

THE NEW SOUTH WALES MASTITIS CONTROL PROGRAM

Bacteriological examinations were made on quarter samples from cows in 35 herds over a 3 year period to monitor the response in a mastitis control program. Initially, Staphylococcus aureus predominated in 32 of the herds and the mean herd prevalence was 26%. The control measures halved this rate but there was considerable variation in response between herds. The decline occurred rapidly and there was a significant reduction (P less than 0.01) by 3 months. Streptococcus agalactiae predominated in 3 herds and the overall infection rate was 4.9%. Control measures eliminated the infection completely from most herds but reinfection occurred in 2 herds. The greatest decline occurred in the first 6 months and was significant (P less than 0.05). The measures had little effect upon Str. uberis and Str. dysgalactiae which remained fairly consistently at low levels. Initially, strains of Staph. aureus resistant to penicillin were dominant in most herds. In a minority of herds strains resistant to streptomycin predominated and in these herds there was a concurrent resistance to penicillin. These patterns did not change greatly over the control period. Resistance by Str. agalactiae to streptomycin occurred in most herds at the start of the program.     

Antimicrobial resistance in streptococcal species isolated from bovine mammary glands

Streptococcal species isolated from dairy cows with clinical mastitis were obtained from mastitis research workers in Florida, Louisiana, New York, Vermont, Washington, and West Virginia. Seventy-one streptococcal isolates were tested, including 39 strains of Streptococcus agalactiae, 21 strains of S dysgalactiae, and 11 strains of S uberis. The minimal inhibitory concentration of erythromycin, lincomycin, oxytetracycline, penicillin, spectinomycin, streptomycin, and tetracycline was determined for each isolate. Differences were not detected among strains with respect to geographic origin. None of the strains was resistant to penicillin. Lincomycin was the next most effective antimicrobial, with only 2 resistant strains of each streptococcal species. There were no differences among the streptococcal species with respect to resistance to either penicillin or lincomycin. Streptococcus uberis was more likely to be resistant to erythromycin than were S agalactiae and S dysgalactiae (P less than 0.02). Streptococcus agalactiae and S uberis had similar distributions for resistance to oxytetracycline, tetracycline, spectinomycin, and streptomycin. Strains of S dysgalactiae were more likely to have intermediate resistance to oxytetracycline and streptomycin than were strains of S agalactiae and S uberis, which were highly resistant to oxytetracycline and streptomycin (P less than 0.001). Differences were not detected among the streptococcal species with respect to resistance to spectinomycin. Resistance to multiple antimicrobials was observed in all streptococcal species tested. Although S dysgalactiae appeared to have a greater percentage of strains (73%) that were resistant to multiple antimicrobials than did S agalactiae (31%) or S uberis (45%), differences were not statistically significant.     

BREEDING FOR RESISTANCE TO BOOPHILUS MICROPLUS IN AUSTRALIAN ILLAWARRA SHORTHORN AND BRAHMAN X AUSTRALIAN ILLAWARRA SHORTHORN CATTLE

SUMMARY Breeding for resistance to the cattle tick Boophilus microplus was undertaken in a herd of Australian Illawarra Shorthorn (AIS) cattle from 1961 to 1978 and in a herd of Braham x AIS cattle from 1970 to 1979. Breeder cows and their progeny were assessed for tick resistance during October to January. Resistance levels were determined as the average percentage mortality of female ticks from two artificial infestations with cohorts of c 20,000 larvae. Resistance increased from 89.2% to 99% in the AIS breeding herd, as a result of the yearly introductions of more resistant individuals and culling of less resistant ones. Concurrently resistance in the AIS progeny increased from 93.7% to 97.7%, thus demonstrating that the selection and breeding of the cows and bulls resulted in genetic improvement in the resistance of the progeny. Milk production tests on heifers from the selected AIS herd during 1975 to 79 indicated that selection for tick resistance did not select against milk production. Resistance of the Brahman x AIS increased from 98.4% to 99.3% in the breeding herd and from 97.6% to 99.6% in the progeny. Female calves of both breeds were more resistant than males.     

Antimicrobial resistance patterns to beta-lactams of gram-positive cocci isolated from bovine mastitis in Lithuania

The aim of the study was to isolate gram-positive cocci from cows with mastitis and to determine their resistance to beta-lactamic antibiotics. Eight hundred and nine strains were isolated and identified as staphylococci (n=516), streptococci (n=199) and enterococci (n=94) from sub-clinical and clinical cases of bovine mastitis in Lithuania. The most common causative agents of udder disease included: S. epidermidis (n=176), S. aureus (n=176), S. agalactiae (n=134), S. hyicus (136) and E. hirae (n=68). Isolates were analysed for antimicrobial resistance to penicillin, ampicillin, amoxicillin, cephalothin, cephalexin, amoxicillin + clavulanate. The susceptibility patterns were analysed using the agar disk diffusion method. S. aureus showed the highest level of resistance to amoxicillin (81.3%), penicillin (76.7%) and ampicillin (78.4%). The corresponding values for CNS strains were 59.7%, 59.7% and 50.6% against penicillin, ampicillin and amoxicillin respectively. Streptococci were the most frequently resistant to amoxicillin (29.3%), and enterococci to penicillin (27%), amoxicillin (27.5%) and amoxicillin/clavulanic acid (23.8%). The resistance of all tested mastitis pathogens to aminopenicillins and penicillin highly correlated (r=0.83). Compared with other antibiotics, amoxicillin and clavulanic acid combination tended to be more effective (p<0.05) against all tested bacteria in vitro. However, S. aureus, in 38.1% of cases, was resistant to this combination of antimicrobials. This study demonstrates that S. epidermidis, S. aureus, S. hyicus, S. agalactiae and E. hirae remain the most frequent mastitis causative agents on Lithuanian cattle farms. The highest resistance in vitro to penicillins was demonstrated by S. aureus, S. hyicus and S. intermedius. Resistance to cephalosporins remains low, irrespective of bacterial species of gram-positive cocci.     

Investigation of biofilm production and icaA and icaD genes in Staphylococcus aureus isolated from heifers and cows with mastitis

Biofilm formation and antimicrobial resistance of Staphylococcus aureus are important virulence factors in cases of mastitis in dairy cows. However, few studies have investigated mastitis strains isolated from heifers. Within this context, the objective of the present study was to investigate biofilm formation on Congo red agar, the presence of the icaA and icaD genes by polymerase chain reaction (PCR), and the percentage of in vitro antimicrobial resistance of 110 S. aureus isolates from mammary gland secretions of heifers and cows with mastitis. PCR detected the icaA and icaD genes in 98% and 100% of isolates, respectively. However, only 55.5% of all isolates produced a biofilm on Congo red agar. Antimicrobial susceptibility testing revealed that 47.0% of isolates from heifers and 70.4% of isolates from cows were resistant to at least one of the antimicrobial agents tested. Resistance to penicillin and/or ampicillin was the most frequent (44.5%). These results indicate the need to implement prophylactic and control measures of mastitis for heifers. Heifers and cows can carry resistant strains with the capacity of biofilm production, a fact representing a threat to public health and animal well‐being and generating losses to dairy farmers.     

A survey of antimicrobial resistance in Salmonellae isolated from animals in England and Wales during 1984-1987

Resistance to 14 antimicrobial substances was tested in 18,647 salmonella strains isolated from animals, their environment and from animal feeds during the period 1984-1987. Of the 2284 Salmonella dublin strains the percentage sensitive to all the antimicrobial substances ranged from 18.1 to 26.8. Resistance to the higher concentration of streptomycin (S25) ranged from 1.9 to 6.4%, whereas the corresponding figures when the lower concentration (S10) was used were 32.3 and 63.8%. Resistance to the higher sulphonamide concentration (Su500) never exceeded 3.3%, although in 1987 70.3% of strains showed resistance to the lower concentration. In general, less than 1% of strains showed resistance to the other antibacterial substances. No strains resistant to amikacin (AK), apramycin (Apr), gentamicin (CN) and colistin (CT) were detected. Of the 8677 S. typhimurium strains the percentage sensitive to all the antimicrobial agents ranged from 6.6 in 1985 to 13.6 in 1987. Resistance to tetracycline (T), ampicillin (PN), trimethoprim (TM) and chloramphenicol (C) ranged from 36.5 to 58.8%, the highest percentages being detected with tetracyclines. Less than 1% of strains showed resistance to furazolidone and none was resistant to amikacin and colistin. Resistance to apramycin ranged from 3.1% in 1984 to 11.6% in 1985; the figures for gentamicin were approximately half that of apramycin. In 1984, 41.6% of strains showed resistance to neomycin but only 8.5% in 1987. The fall in neomycin resistance was associated with the epidemic spread of the commonest phage-type DT204C becoming sensitive to neomycin. Of the 7687 strains of serotypes other than S. typhimurium and S. dublin the percentage sensitive to all antimicrobial agents ranged from 23.7 in 1985 to 14.7 in 1987. Resistance to tetracyclines and sulphonamides (Su500) ranged from 5.2 to 12.1% and 5.8 to 13.3% respectively. Resistance to the other antimicrobial agents was usually less than 5%.     

Antibiotic resistance of staphylococci from humans, food and different animal species according to data of the Hungarian resistance monitoring system in 2001

Based on data of the Hungarian resistance monitoring system the antibiotic resistance of Staphylococcus strains of human and animal origin was studied. No methicillin-resistant staphylococci harbouring mecA gene were isolated from animals in 2001. Penicillin resistance, mediated by penicillinase production, was the most frequent among Staphylococcus aureus strains isolated from humans (96%), from bovine mastitis (55%), from foods (45%) and from dogs. In staphylococci isolated from animals low resistance percentages to aminoglycosides (0-2%), fluoroquinolones (0.5-3%) and sulphonamides (0.5-4%) were found but in strains isolated humans these figures were higher (1-14%, 5-18% and 3-31%, respectively). The most frequent antibiotic resistance profiles of strains isolated from animals and food were penicillin/tetracycline, penicillin/lincomycin and penicillin/lincomycin/tetracycline. Penicillin/tetracycline resistance was exhibited by strains from mastitis (3), samples from the meat industry (31), poultry flocks (1), poultry industry (1), noodle (1) and horses (2). Penicillin/lincomycin resistance was found in 10 Staphylococcus strains from mastitis, 1 from the dairy industry, 1 from the meat industry and 6 from dogs. Isolates from mastitis (2), from the dairy industry (2), from pigs (1), from the meat industry (1) and from poultry (1) harboured penicillin/lincomycin/tetracycline resistance pattern. Multiresistant strains were usually isolated only from one and sometimes from two animal species; therefore, the spread of defined resistant strains (clones) among different animal species could not be demonstrated. These results also suggest that the transfer of antibiotic resistance of S. aureus from animals to humans probably occurs less frequently than is generally assumed.     

Antimicrobial susceptibility of Staphylococcus aureus and Staphylococcus pseudintermedius isolated from various animals

This study characterized the antimicrobial susceptibility of 221 Staphylococcus aureus isolated from various species, and 60 canine Staphylococcus pseudintermedius isolated from 1986 through 2000 at the Western College of Veterinary Medicine (WCVM). Resistance of S. aureus was most common to penicillin (31%) and tetracycline (14%); resistance of S. pseudintermedius to penicillin was present in 8% and to tetracycline in 34% of isolates. Resistance to trimethoprim/sulfamethoxazole was only seen among S. pseudintermedius, and there was no resistance to amoxicillin/clavulanate, ampicillin/sulbactam, cephalothin, amikacin, gentamicin, enrofloxacin, chloramphenicol, or rifampin among any isolate. Inducible clindamycin resistance was found in both S. aureus and S. pseudintermedius, highlighting the need for careful interpretation of culture and susceptibility test results. There were significant differences in the minimum inhibitory concentrations of penicillin, ciprofloxacin, enrofloxacin, clindamycin, erythromycin, chloramphenicol, and tetracycline between avian, bovine, equine, and porcine isolates.     

Resistance of Staphylococcus-aureus strains, isolated from food, to antibiotics]

Resistance to selected antibiotics was studied in 325 strains of Staphylococcus aureus, isolated from foodstuffs. Out of these strains, 50.46% were resistant to penicillin, 15.7% to ampicillin, 4% to streptomycin, 5.2% to erythromycin, 5.8% to chloramphenicol, 18.5% to tetracycline, 18.2% to oxytetracycline, 2.5% to gentamycin, 1.6% to canamycin, 53.5% to colistine and 9.2% to bacitracin. Eighty-five strains (26.15%) were sensitive to all the antibiotics used; 107 strains (32.92%) were resistant to one antibiotic, and 133 strains (40.93%) to two or more antibiotics.     

Phage typing of Staphylococcus aureus strains isolated in Sweden from bovine milk.

Both the human and the bovine international sets of phages were used for typing of 372 bovine Staphylococcus aureus (Sa) strains, whereas the bovine set alone was used for typing of a further 1183 strains. In addition, 338 of the strains were tested for antibiotic sensitivity. Out of 372 Sa strains 85.5% could be typed with the human and 89.8% with the bovine phage set. Of all the 1555 Sa strains used 92.4% were lysed by the bovine phage set. Several phage types can be present in one and the same herd and some of them can predominate. Resistance to most of the tested antibiotics was very low. The incidence of resistance to penicillin and ampicillin was 10.0% and 4.4% respectively.     

Aanalysis of resistance and its transferability in microflora from primary meat production]

Resistance spectra and their transferability were studied in G- strains isolated from the primary production of meat by the method after Bohus (1974). Out of the set of strains, 93% were resistant, and out of these, 65% were multiresistant. Thirty-five per cent of the resistant strains were R plasmid donors. Of the two recipients, the laboratory strain of E. coli IHE Nx was significantly better. Among the 21 determined resistance spectra, the following were the most frequent: Tc, SmTcSu, and TcAm. Transfer of two to four, or even six, different plasmid types, mostly simple, was recorded from the two most frequent complex types of donor strain resistance: SmCmTcAmSu and SmTcAmSu. The determinants Tc and Am prevailed in the spectra of the transferring R plasmids, mostly as separate markers and only in 21 to 36% of cases in more complex types.     

Antimicrobial Susceptibility of Microorganisms Isolated from Equine Orthopedic Patients

Positive cultures were obtained from 60 equine orthopedic cases during a 12 year period (1974-1985). These cases consisted of 34 long or cuboidal bone fractures, 13 arthrotomy/arthroscopy procedures for removal or internal fixation of a fracture, 7 proximal splint bone fractures, and 6 facial or mandibular fractures. Excluding the 13 arthrotomies, only 10 (21%) of the 47 were open fractures. Multiple organisms were isolated from 36 cases (20 long or cuboidal bone fractures, 7 splint bone fractures, 5 mandibular fractures, and 4 intra-articular fractures). Of the 142 isolates, 35 (24%) were members of the family Enterobacteriaceae, 33 (23%) Streptococcus spp., and 25 (18%) Staphylococcus spp. with the majority being coagulase positive (65%). Other organisms isolated were Pseudomonas spp. (16, 11%), obligate anaerobes (11, 7%), and Actinobacillus spp. (7, 5%). the remaining 10% consisted of Pasteurella spp., Bacillus spp., Corynebacterium spp., Micrococcus spp., and Actinomyces spp. When comparing results between two time periods (1974-1979 and 1980-1985) there was an increase in the percentage of coagulase positive staphylococci isolates resistant to all antimicrobics tested except oxacillin and amikacin, and Escherichia coli isolates were resistant to all but amikacin. For Pseudomonas spp., resistance to gentamicin increased in the second time period (1980-1986). During the initial time period (1974-1979) culture tests for obligate anerobes were not conducted until 1975. No anerobes were cultured during those initial 5 years; however, one third of those isolated after 1980 were resistant to penicillin and ampicillin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterization of Methicillin‐Resistant Staphylococcus aureus Isolates from Pig Carcasses in Hong Kong

This study describes the isolation and characterization of methicillin‐resistant Staphylococcus aureus (MRSA) from slaughtered pigs sampled from local markets in Hong Kong. The nares of 400 slaughtered pigs were cultured and MRSA isolates characterized for the presence of antibiotic‐resistance determinants, toxins and SCCmec and spa types using PCR. Clonality was investigated using PFGE and MLST. The prevalence of MRSA colonization of slaughter pigs was 39.3%, the majority (92%) harbouring SCCmec type IVb. Of the 157 samples yielding MRSA, 13 had two distinct MRSA strains present. Spa type t899 was predominant, with only 5/170 isolates displaying closely related types (t4474, t1939, t2922 and t5390). PFGE with sma1 and MLST confirmed the strains as ST9. Most isolates were multidrug resistant. Tetracycline resistance (97%) was mainly attributable to tet(K) with only 3% of isolates additionally harbouring tet(M). Resistance to erythromycin (89%) and chloramphenicol (71%) was associated with the presence of erm(C), and fex( A), respectively. No strains carried cfr and there was no resistance to linezolid, although minimum inhibitory concentration (MICs) were close to the resistance break point. Resistance to clindamycin (99%), ciprofloxacin(78%), quinopristin–dalfopristin (44%) and cotrimoxazole (32%) was common, but remained low for fusidic acid (4%) and rifampicin (2%). All strains were negative for PVL, exfoliative, and enterotoxins. This survey confirmed the uniformity of MRSA isolates in pigs from several regions of China, in contrast to more diversified characteristics reported in European studies. Colonization rates were higher than previously reported. Isolates were resistant to a wide range of antibiotics, but resistance was not detected to linezolid, nitrofurantoin, vancomycin or tigecycline. Although the clinical importance of ST9 in humans is uncertain, continued surveillance, in particular of those occupationally‐exposed, is recommended.     

Susceptibility of Clostridium perfringens of animal origin to fifteen antimicrobial agents

The minimal inhibitory concentrations of fifteen antibacterial agents were determined by agar-dilution method against 121 strains of Clostridium perfringens isolated from pigs, cattle and poultry. All strains, regardless of host of origin, were susceptible to avoparcin, furazolidone, monensin, nitrovin, penicillin G, ronidazole and tiamulin and resistant to flavomycin. Poultry strains were also susceptible to carbadox, chloramphenicol, erythromycin and virginiamycin. Bacitracin-resistant poultry strains were susceptible to all tested antibacterial agents except tetracycline, but the bacitracin-resistant cattle strains were polyresistant. Porcine strains were susceptible to bacitracin and bovine strains to carbadox. Carbadox-resistant porcine strains were resistant to erythromycin, lincomycin and tetracycline and susceptible to chloramphenicol. Resistance to erythromycin was associated with resistance to lincomycin. High level erythromycin-lincomycin-resistant strains were susceptible to virginiamycin, but the intermediate level erythromycin-lincomycin-resistant cattle strains were resistant to virginiamycin. Resistance to chloramphenicol or erythromycin-lincomycin was always associated with resistance to tetracycline but the reverse was not always true.     

Antibiotic resistance and transferable antibiotica resistance Escherichia coli isolated from calves on a modern farm with therapeutic problems and unsatisfactory management conditions.

On a farm with therapeutic problems and unsatisfactory management conditions, the occurrence of antibiotic resistance and transferable antibiotic resistance has been studied in E. coli isolated from calves which were 5 and 30 days old. Strains with resistance to up to seven antibiotics as well as transferable resistance against up to five antibiotics were recorded. On an average, 4.2 strains with different patterns and 4.0 different strains with transferable resistance were isolated from each calf. The corresponding figures previously found for healthy control calves were 1.6 and 1.1 strains, respectively. Resistance and transferable resistance were most common against sulphonamide and penicillin.