Frequency of R Factor-mediated Multiple Drug Resistance in Klebsiella and Aerobacter

Abstract

A comparative study was done on the transfer frequency of R factors from 90 strains of multiple drug-resistant Aerobacter and 81 strains of Klebsiella to Escherichia coli CSH-2 (F-, met-, pro-, Nal-r). The most common resistance patterns for the Aerobacter isolants were ampicillin streptomycin chloramphenicol tetracycline and ampicillin streptomycin chloramphenicol tetracycline kanamycin neomycin; for the Klebsiella isolants, the most common resistance pattern was ampicillin kanamycin streptomycin tetracycline chloramphenicol neomycin. R factors were isolated from 14.1% of the Aerobacter strains; 61.5% of these R factors harbored R determinants for ampicillin streptomycin tetracycline. R factors were isolated from 79.1% of the Klebsiella strains; four R factors were isolated with significant frequency; streptomycin chloramphenicol kanamycin neomycin, 37.5%; ampicillin streptomycin tetracycline kanamycin neomycin, 14.1%; ampicillin streptomycin tetracycline, 12.5%; and streptomycin chloramphenicol tetracycline, 12.5%. Chloramphenicol, kanamycin, and neomycin resistance was rarely transferred from the Aerobacter strains, although over 50% of the clinical isolants possessed resistance to these antibiotics. In contrast, over 75% of the Klebsiella strains transferred resistance to chloramphenicol, kanamycin, neomycin. Highest frequency of transferred resistance to individual drugs in the Aerobacter strains was to streptomycin (14.8%), whereas in the Klebsiella group resistance to four drugs was transferred at a very high frequency: streptomycin (80.8%), chloramphenicol (78.5%), kanamycin (76.4%7c), and neomycin (75.9%). Within the last 5 years in the Medical College of Virginia hospitals, as in others, there has been a significant increase in infections caused by gramnegative bacteria (2, 7, 14, 15, 17). Particularly, Aerobacter and Klebsiella have demonstrated an increase in resistance to multiple drugs which may be due to episomal resistance transfer factors (1, 8). This type of rapidly appearing multiple drug resistance is known to be mediated by an extrachromosomal deoxyribonucleic acid particle (R factor), which is an independent linkage group composed of genes determining drug resistance (R determinants; 4, 20). The existence of gram-negative bacteria possessing R factors responsible for resistance to numerous antibiotics, i.e., ampicillin (Am), tetracycline (Tc), chloramphenicol (Cm), streptomycin (Sm), kanamycin (Km), the sulfonamides, and neomycin (Nm), has been reported in Japan, Great Britain, the European continent, Israel, and recently in the United States (3, 9, 15, 16, 18). In this communication, the incidence of R factors in clinically isolated multiple drug-resistant strains of Klebsiella and Aerobacter is reported. MATERIALS AND METHODS Sources of bacteria. Strains of multiple drugresistant Klebsiella and Aerobacter were isolated from clinical sources, i.e., urine, sputum, wounds, exudates, and blood, during the period from March to June 1968. No effort was made to distinguish between hospitaland com...

Behavior of a hybrid F' ts114 lac+, his+ factor (F42-400) in Klebsiella pneumoniae M5a1

“…None was found. Klebsiella strains are known to harbor a variety of plasmids (12,19,27,44,49,(85)(86)(87). There is no evidence for extrachrosomal deoxyribonucleic acid (DNA) in K. pneumoniae M5al (15), and our strains are not resistant to 10 gg of chloramphenicol per ml.…”

“…The presence of plasmid DNA in strains of Enterobacteriaceae is not uncommon. In fact, several of the Klebsiella strains studied have been shown to harbor plasmid DNA (12,19,27,44,49,85,86,87). A class of R factors has been shown to possess the ability to inhibit their own transfer and that of other transfer-proficient plasmids (fertility inhibition, Fin+) (111).…”

Antibiotic-resistant bacteria in drinking water

“…The occurrence of multiply antibiotic-resistant (MAR) bacteria in the environment is certainly a well-known phenomenon (8,14,28). Many investigators believe that these drug-resistant organisms have become more common recently due to the extensive use of antibiotics in medicine and agriculture throughout the world (15, 17,24,32). Concern about this situation has also become more common, since the antibacterial value of drugs is threatened seriously by the increased prevalence of resistant bacteria (15, 17).…”

“…Many investigators believe that these drug-resistant organisms have become more common recently due to the extensive use of antibiotics in medicine and agriculture throughout the world (15, 17,24,32). Concern about this situation has also become more common, since the antibacterial value of drugs is threatened seriously by the increased prevalence of resistant bacteria (15, 17). This concern is particularly relevant in light of the discovery that resistance characteristics can be transferred to nonresistant recipient cells via R-factor plasmid vectors (23).…”

Characterization of aquatic bacteria and cloning of genes specifying partial degradation of 2,4-dichlorophenoxyacetic acid

“…After expression of the plasmid in its new host, cells were plated on LB agar containing 25 ,ug of chloramphenicol and 200 ,ug of ampicillin per ml. Colonies unable to grow on LB agar plates containing 15 ,ug of tetracycline per ml were prepared for small-scale plasmid extraction and examined for evidence of cloned DNA in vector pBR325.…”