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Abstract
A new perspective on the topic of antibiotic resistance is beginning to emerge based on a broader evolutionary and ecological understanding rather than from the traditional boundaries of clinical research of antibiotic-resistant bacterial pathogens. Phylogenetic insights into the evolution and diversity of several antibiotic resistance genes suggest that at least some of these genes have a long evolutionary history of diversification that began well before the 'antibiotic era'. Besides, there is no indication that lateral gene transfer from antibiotic-producing bacteria has played any significant role in shaping the pool of antibiotic resistance genes in clinically relevant and commensal bacteria. Most likely, the primary antibiotic resistance gene pool originated and diversified within the environmental bacterial communities, from which the genes were mobilized and penetrated into taxonomically and ecologically distant bacterial populations, including pathogens. Dissemination and penetration of antibiotic resistance genes from antibiotic producers were less significant and essentially limited to other high G+C bacteria. Besides direct selection by antibiotics, there is a number of other factors that may contribute to dissemination and maintenance of antibiotic resistance genes in bacterial populations.
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252
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Lin J, Yan M, Sahin O, Pereira S, Chang YJ, Zhang Q. Effect of macrolide usage on emergence of erythromycin-resistant Campylobacter isolates in chickens. Antimicrob Agents Chemother 2007; 51:1678-86. [PMID: 17353243 PMCID: PMC1855539 DOI: 10.1128/aac.01411-06] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In this work we conducted both in vitro and in vivo experiments to examine the development and mechanisms of erythromycin (Ery) resistance in Campylobacter jejuni and Campylobacter coli. In vitro plating revealed that both Campylobacter species had similar but low spontaneous mutation frequencies (3 x 10(-9) to <5.41 x 10(-10)) for Ery resistance. Chickens infected with C. jejuni or C. coli were subjected to single or multiple treatments with medicated water containing tylosin (0.53 g/liter), which transiently reduced the level of Campylobacter colonization but did not select for Ery-resistant (Ery(r)) mutants in the treated birds. However, when tylosin was given to the chickens in feed at a growth-promoting dose (0.05 g/kg feed), Ery(r) mutants emerged in the birds after prolonged exposure to the antibiotic. The vast majority of the in vitro- and in vivo-selected Campylobacter mutants with Ery MICs of 8 to 256 microg/ml lacked the known resistance-associated mutations in the 23S rRNA gene, while the highly resistant mutants (Ery MIC > 512 microg/ml) had the A2074G mutation in the 23S rRNA gene. Inactivation of CmeABC, a multidrug efflux pump, dramatically reduced the Ery MIC in all of the examined mutants regardless of the presence of the A2074G mutation. Together, these results reveal distinct features associated with Ery resistance development in Campylobacter, demonstrate the significant role of CmeABC in Ery resistance, and suggest that long-term use of a macrolide as a growth promoter selects for the emergence of Ery(r) Campylobacter in animal reservoirs.
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Affiliation(s)
- Jun Lin
- Department of Veterinary Microbiology and Preventive Medicine, 1116 Veterinary Medicine Complex, Iowa State University, Ames, IA 50011, USA
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253
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Lévesque S, Frost E, Michaud S. Comparison of antimicrobial resistance of Campylobacter jejuni isolated from humans, chickens, raw milk, and environmental water in Québec. J Food Prot 2007; 70:729-35. [PMID: 17388066 DOI: 10.4315/0362-028x-70.3.729] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This study compares the occurrence of antimicrobial resistance to erythromycin, ciprofloxacin, and tetracycline among 384 Campylobacter jejuni isolates from humans (245), fresh whole retail chickens (56), raw milk (33), and environmental water (41) collected between 2000 and 2003 in Québec, Canada. Resistance to ciprofloxacin was significantly more frequent in human isolates acquired abroad than in those acquired locally (50 versus 5.9%; P < 0.001); ciprofloxacin resistance was almost absent in water, chicken, and raw milk isolates. In contrast, resistance to erythromycin was significantly more common in chicken than in locally acquired human isolates (16 versus 3.0%, respectively; P < 0.001); no erythromycin resistance was found among water, raw milk, and human isolates acquired abroad. Resistance to tetracycline was significantly more common in chicken and human isolates acquired locally (58.9 and 45.8%, respectively) than in raw milk and water isolates (9.1 and 7.3%, respectively, P < 0.001). Tetracycline resistance was also observed in 44.4% of human isolates acquired abroad. No human isolate was resistant to both ciprofloxacin and erythromycin, but one chicken isolate was resistant to all three antimicrobial agents. Our results suggest that from 2000 to 2003 in Québec, antimicrobial resistance remained stable among locally acquired C. jejuni human clinical isolates and might even have decreased. However, the high erythromycin resistance rate observed among chicken isolates is concerning because of the risk of transmission of such isolates to humans. Additional studies are needed to monitor trends in antimicrobial resistance among food, environment, and human C. jejuni isolates as well as antibiotic use in animals.
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Affiliation(s)
- Simon Lévesque
- Department of Microbiology and Infectious Diseases, Faculté de Mèdecine de l'Université de Sherbrooke, Québec, Canada J1H 5N4
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254
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Han K, Jang SS, Choo E, Heu S, Ryu S. Prevalence, genetic diversity, and antibiotic resistance patterns of Campylobacter jejuni from retail raw chickens in Korea. Int J Food Microbiol 2007; 114:50-9. [PMID: 17207550 DOI: 10.1016/j.ijfoodmicro.2006.10.042] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2006] [Revised: 08/17/2006] [Accepted: 10/09/2006] [Indexed: 10/23/2022]
Abstract
Campylobacter jejuni is a frequently detected food-borne pathogenic bacterium. Clinical cases are mostly sporadic but campylobacteriosis can have serious consequences, such as the development of Guillain-Barré syndrome as well as diarrheal diseases. We examined 265 retail raw chickens from Korean markets for the presence of C. jejuni using the US Food and Drug Administration standard cultural method and multiplex polymerase chain reaction (mPCR). The mPCR-confirmed C. jejuni isolates were subtyped by pulsed field gel electrophoresis (PFGE) and flaA-typing for investigating the genetic diversity of the microorganism in retail raw chickens. Restriction enzymes SmaI and DdeI were used for PFGE and flaA-typing, respectively. Campylobacter spp. were found in 181 samples (68.3%) and C. jejuni in 100 samples (37.74%). For C. jejuni, 73 pulsotypes and 30 flaA types were detected. Antibiotic resistance tests performed by disk diffusion assay indicated that most C. jejuni isolates were resistant to tetracycline, nalidixic acid, and ciprofloxacin, and 87 composite types were revealed by PFGE, flaA-typing, and the antibiotic resistance tests. Our results show that the genetic diversity of C. jejuni isolates is very high and the correlation between genotype and antibiotic resistance was low even though many bacteria showed multi-drug resistance.
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Affiliation(s)
- Kiseon Han
- Department of Food and Animal Biotechnology, School of Agricultural Biotechnology and Center for Agricultural Biomaterials, Seoul National University, San 56-1, Shillim-dong, Kwanak-gu, Seoul 151-742, Republic of Korea
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255
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Sonnevend Á, Rotimi VO, Kolodziejek J, Usmani A, Nowotny N, Pál T. High level of ciprofloxacin resistance and its molecular background among Campylobacter jejuni strains isolated in the United Arab Emirates. J Med Microbiol 2006; 55:1533-1538. [PMID: 17030913 DOI: 10.1099/jmm.0.46744-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The antibiotic sensitivity and the serotype and molecular type (MT) distribution of 41 Campylobacter jejuni strains isolated from individual patients in Tawam Hospital, Al Ain, United Arab Emirates, were investigated. While all strains were sensitive to erythromycin (MIC 0.5-4 mg l(-1)), 35 isolates (85.4 %) exhibited resistance to ciprofloxacin (MIC 8-64 mg l(-1)). All resistant strains carried the Thr-86 to Ile mutation in the gyrase A (gyrA) gene, as shown by mismatch amplification mutation assay (MAMA) and confirmed by sequencing. Based on the partial sequences of gyrA, resistant isolates carried 10 distinct alleles, eight of them representing new variants. Strains were assigned to 30 MTs based on the combined results of PFGE and flaA PCR-RFLP typing. Eight of the 35 ciprofloxacin-resistant strains, isolated over a period of more than 1 year, represented the largest MT, also carrying the same allelic variant of the gyrA gene. These results show that the local incidence of fluoroquinolone resistance among C. jejuni is one of the highest reported worldwide. It was also demonstrated that stable MTs could persist for a relatively long time among the clonally unrelated antibiotic-resistant isolates of C. jejuni. The data also emphasize the need to replace fluoroquinolones as empirical therapy for diarrhoea of undiagnosed aetiology.
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Affiliation(s)
- Ágnes Sonnevend
- Department of Medical Microbiology and Immunology, University of Pécs, Pécs, Hungary
- Department of Medical Microbiology, Faculty of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Vincent O Rotimi
- Department of Medical Microbiology, Faculty of Medicine, University of Kuwait, Kuwait
| | - Jolanta Kolodziejek
- Zoonoses and Emerging Infections Group, Clinical Virology, Clinical Department of Diagnostic Imaging, Infectious Diseases and Clinical Pathology, University of Veterinary Medicine, Vienna, Austria
| | - Asad Usmani
- Department of Medical Microbiology, Faculty of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Norbert Nowotny
- Zoonoses and Emerging Infections Group, Clinical Virology, Clinical Department of Diagnostic Imaging, Infectious Diseases and Clinical Pathology, University of Veterinary Medicine, Vienna, Austria
- Department of Medical Microbiology, Faculty of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Tibor Pál
- Department of Medical Microbiology and Immunology, University of Pécs, Pécs, Hungary
- Department of Medical Microbiology, Faculty of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
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256
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Quinn T, Bolla JM, Pagès JM, Fanning S. Antibiotic-resistant Campylobacter: could efflux pump inhibitors control infection? J Antimicrob Chemother 2006; 59:1230-6. [PMID: 17118938 DOI: 10.1093/jac/dkl470] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Campylobacter is the most common cause of bacterial gastroenteritis in the world. Poultry is the main reservoir of human infections. The widespread use of antibiotics in agriculture and veterinary medicine has resulted in the emergence of an increasing number of antibiotic-resistant Campylobacter strains that can be transmitted to humans through the food chain. Of particular concern to public health is the prevalence of resistance to macrolides and fluoroquinolones that are used in the treatment of life-threatening campylobacteriosis. The CmeABC efflux system has been shown to contribute to the intrinsic and acquired resistance to these antibiotics. In addition, by mediating resistance to bile, it is essential for colonization of the chicken gut in vivo. Inhibition of CmeABC may provide an effective means of reversing antibiotic resistance and decreasing the transmission of Campylobacter via the food chain. This would positively impact on public health by decreasing the morbidity, mortality and increased healthcare costs associated with the treatment of antibiotic-resistant Campylobacter.
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Affiliation(s)
- Teresa Quinn
- Centre for Food Safety, School of Agriculture, Food Science and Veterinary Medicine, University College Dublin Belfield, Dublin 4, Ireland
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257
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Andersson DI. The biological cost of mutational antibiotic resistance: any practical conclusions? Curr Opin Microbiol 2006; 9:461-5. [PMID: 16890008 DOI: 10.1016/j.mib.2006.07.002] [Citation(s) in RCA: 299] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2006] [Accepted: 07/21/2006] [Indexed: 10/24/2022]
Abstract
A key parameter influencing the rate and trajectory of the evolution of antibiotic resistance is the fitness cost of resistance. Recent studies have demonstrated that antibiotic resistance, whether caused by target alteration or by other mechanisms, generally confers a reduction in fitness expressed as reduced growth, virulence or transmission. These findings imply that resistance might be reversible, provided antibiotic use is reduced. However, several processes act to stabilize resistance, including compensatory evolution where the fitness cost is ameliorated by additional mutation without loss of resistance, the rare occurrence of cost-free resistance mechanisms and genetic linkage or co-selection between the resistance markers and other selected markers. Conceivably we can use this knowledge to rationally choose and design targets and drugs where the costs of resistance are the highest, and where the likelihood of compensation is the lowest.
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Affiliation(s)
- Dan I Andersson
- Department of Medical Biochemistry and Microbiology, Uppsala University, Box 582, S-751 23 Uppsala, Sweden.
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258
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Luangtongkum T, Morishita TY, Ison AJ, Huang S, McDermott PF, Zhang Q. Effect of conventional and organic production practices on the prevalence and antimicrobial resistance of Campylobacter spp. in poultry. Appl Environ Microbiol 2006; 72:3600-7. [PMID: 16672508 PMCID: PMC1472326 DOI: 10.1128/aem.72.5.3600-3607.2006] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Intestinal tracts of broilers and turkeys from 10 conventional broiler farms and 10 conventional turkey farms, where antimicrobials were routinely used, and from 5 organic broiler farms and 5 organic turkey farms, where antimicrobials had never been used, were collected and cultured for Campylobacter species. A total of 694 Campylobacter isolates from the conventional and organic poultry operations were tested for antimicrobial resistance to nine antimicrobial agents by the agar dilution method. Although Campylobacter species were highly prevalent in both the conventional and organic poultry operations, the antimicrobial resistance rates were significantly different between the organic operations and the conventional operations. Less than 2% of Campylobacter strains isolated from organically raised poultry were resistant to fluoroquinolones, while 46% and 67% of Campylobacter isolates from conventionally raised broilers and conventionally raised turkeys, respectively, were resistant to these antimicrobials. In addition, a high frequency of resistance to erythromycin (80%), clindamycin (64%), kanamycin (76%), and ampicillin (31%) was observed among Campylobacter isolates from conventionally raised turkeys. None of the Campylobacter isolates obtained in this study was resistant to gentamicin, while a large number of the isolates from both conventional and organic poultry operations were resistant to tetracycline. Multidrug resistance was observed mainly among Campylobacter strains isolated from the conventional turkey operation (81%). Findings from this study clearly indicate the influence of conventional and organic poultry production practices on antimicrobial resistance of Campylobacter on poultry farms.
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Affiliation(s)
- Taradon Luangtongkum
- Department of Veterinary Preventive Medicine, Ohio State University, 1920 Coffey Road, Columbus, OH 43210, USA
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259
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Doyle MP, Erickson MC. Emerging microbiological food safety issues related to meat. Meat Sci 2006; 74:98-112. [PMID: 22062720 DOI: 10.1016/j.meatsci.2006.04.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2006] [Revised: 04/20/2006] [Accepted: 04/24/2006] [Indexed: 12/09/2022]
Abstract
Avian influenza viruses and antibiotic-resistant pathogens have become topics of current public health interest. This paper will focus on the significance of these pathogens to the meat industry as well as other emerging microbiological food safety topics likely to impact the meat industry. These include surveillance of foodborne pathogens, microbial source tracking, risk assessment, and human populations at increased risk of infection by foodborne microbes. These emerging issues will likely lead to even greater challenges to producing microbiologically safe meat products than the industry has ever experienced. However, accompanying such challenges will be innovative solutions that provide even greater public health protection to meat-containing foods.
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Affiliation(s)
- M P Doyle
- Center for Food Safety, University of Georgia, 1109 Experiment Street, Griffin, GA 30223, USA
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260
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Zhang Q, Sahin O, McDermott PF, Payot S. Fitness of antimicrobial-resistant Campylobacter and Salmonella. Microbes Infect 2006; 8:1972-8. [PMID: 16714138 DOI: 10.1016/j.micinf.2005.12.031] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2005] [Accepted: 12/28/2005] [Indexed: 11/26/2022]
Abstract
Campylobacter and Salmonella are the most commonly reported bacterial causes of human foodborne infections, and increasing proportions of these pathogens become resistant to medically important antimicrobial agents, imposing a burden on public health. Acquisition of resistance to antibiotics affects the adaptation and evolution of Salmonella and Campylobacter in various environments. Many resistance-conferring mutations entail a biological fitness cost, while others (e.g. fluoroquinolone resistance in Campylobacter) have no cost or even enhanced fitness. In Salmonella, the fitness disadvantage due to antimicrobial resistance can be restored by acquired compensatory mutations, which occur both in vitro and in vivo. The compensated or even enhanced fitness associated with antibiotic resistance may facilitate the spread and persistence of antimicrobial-resistant Salmonella and Campylobacter in the absence of selection pressure, creating a significant barrier for controlling antibiotic-resistant foodborne pathogens.
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Affiliation(s)
- Qijing Zhang
- Department of Veterinary Microbiology and Preventive Medicine, Iowa State University, Ames, IA 50011, USA.
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261
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Kos VN, Keelan M, Taylor DE. Antimicrobial susceptibilities of Campylobacter jejuni isolates from poultry from Alberta, Canada. Antimicrob Agents Chemother 2006; 50:778-80. [PMID: 16436744 PMCID: PMC1366894 DOI: 10.1128/aac.50.2.778-780.2006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
One hundred four isolates of Campylobacter jejuni from poultry in Alberta, Canada, collected during 2001 were tested for resistance to 10 antimicrobial agents using agar dilution. This study provides a baseline of resistance profiles and the mechanisms of resistance observed in C. jejuni in poultry from Alberta, Canada.
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Affiliation(s)
- Veronica N Kos
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
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262
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Wang HH, Manuzon M, Lehman M, Wan K, Luo H, Wittum TE, Yousef A, Bakaletz LO. Food commensal microbes as a potentially important avenue in transmitting antibiotic resistance genes. FEMS Microbiol Lett 2006; 254:226-31. [PMID: 16445749 DOI: 10.1111/j.1574-6968.2005.00030.x] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The rapid emergence of antibiotic-resistant (ART) pathogens is a major threat to public health. While the surfacing of ART food-borne pathogens is alarming, the magnitude of the antibiotic resistance (AR) gene pool in food-borne commensal microbes is yet to be revealed. Incidence of ART commensals in selected retail food products was examined in this study. The presence of 10(2)-10(7) CFU of ART bacteria per gram of foods in many samples, particularly in ready-to-eat, 'healthy' food items, indicates that the ART bacteria are abundant in the food chain. AR-encoding genes were detected in ART isolates, and Streptococcus thermophilus was found to be a major host for AR genes in cheese microbiota. Lactococcus lactis and Leuconostoc sp. isolates were also found carrying AR genes. The data indicate that food could be an important avenue for ART bacterial evolution and dissemination. AR-encoding plasmids from several food-borne commensals were transmitted to Streptococcus mutans via natural gene transformation under laboratory conditions, suggesting the possible transfer of AR genes from food commensals to human residential bacteria via horizontal gene transfer.
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Affiliation(s)
- Hua H Wang
- Department of Food Science and Technology, The Ohio State University, Columbus, OH, USA.
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263
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Khachatryan AR, Hancock DD, Besser TE, Call DR. Antimicrobial drug resistance genes do not convey a secondary fitness advantage to calf-adapted Escherichia coli. Appl Environ Microbiol 2006; 72:443-8. [PMID: 16391076 PMCID: PMC1352232 DOI: 10.1128/aem.72.1.443-448.2006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Maintenance of antimicrobial drug resistance in bacteria can be influenced by factors unrelated to direct selection pressure such as close linkage to other selectively advantageous genes and secondary advantage conveyed by antimicrobial resistance genes in the absence of drug selection. Our previous trials at a dairy showed that the maintenance of the antimicrobial resistance genes is not influenced by specific antimicrobial selection and that the most prevalent antimicrobial resistance phenotype of Escherichia coli is specifically selected for in young calves. In this paper we examine the role of secondary advantages conveyed by antimicrobial resistance genes. We tested antimicrobial-susceptible null mutant strains for their ability to compete with their progenitor strains in vitro and in vivo. The null mutant strains were generated by selection for spontaneous loss of resistance genes in broth supplemented with fusaric acid or nickel chloride. On average, the null mutant strains were as competitive as the progenitor strains in vitro and in newborn calves (in vivo). Inoculation of newborn calves at the dairy with antimicrobial-susceptible strains of E. coli did not impact the prevalence of antimicrobial-resistant E. coli. Our results demonstrate that the antimicrobial resistance genes are not responsible for the greater fitness advantage of antimicrobial-resistant E. coli in calves, but the farm environment and the diet clearly exert critical selective pressures responsible for the maintenance of antimicrobial resistance genes. Our current hypothesis is that the antimicrobial resistance genes are linked to other genes responsible for differential fitness in dairy calves.
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Affiliation(s)
- Artashes R Khachatryan
- Department of Veterinary Microbiology and Pathology, 402 Bustad Hall, Pullman, WA 99164-7040, USA
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264
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Keller J, Perreten V. Genetic diversity in fluoroquinolone and macrolide-resistant Campylobacter coli from pigs. Vet Microbiol 2005; 113:103-8. [PMID: 16289952 DOI: 10.1016/j.vetmic.2005.10.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2005] [Revised: 10/05/2005] [Accepted: 10/11/2005] [Indexed: 11/30/2022]
Abstract
The genetic diversity of 115 Campylobacter coli strains, isolated from pigs of 59 geographical distant farms in Switzerland, were characterized on the basis of their DNA fingerprints and resistance to macrolides and fluoroquinolones. Sequence analysis showed that the macrolide-resistant isolates had a point mutation in the 23S ribosomal RNA (rRNA) genes (A2075G) and that the fluoroquinolone-resistant isolates had a point mutation in the gyrase gene gyrA (C257T). One fluoroquinolone-resistant strain had an additional transition mutation in the gyrB gene (A1471C). The flaA restriction fragment length polymorphism (RFLP) genotyping revealed that 57% of the isolates were genetically different. Point mutations in the 23S rRNA and gyrA genes could be found in both genetically distant and genetically related isolates. Additionally, isolates with and without point mutations were found within individual farms and on different farms. This study showed that the ciprofloxacin and erythromycin-resistant C. coli population present on the pig farms is not issued from a common ancestral clone, but individual Campylobacter strains have most likely mutated independently to acquire resistances under the selective pressure of an antibiotic.
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Affiliation(s)
- Jan Keller
- Institute of Veterinary Bacteriology, University of Berne, Längass-Strasse 122, Postfach, CH-3001 Bern, Switzerland
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265
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Abstract
This review describes characteristics of the family Campylobacteraceae and traits of Campylobacter jejuni. The review then focuses on the worldwide problem of C. jejuni antimicrobial resistance and mechanisms of pathogenesis and virulence. Unravelling these areas will help with the development of new therapeutic agents and ultimately decrease illness caused by this important human pathogen.
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Affiliation(s)
- W J Snelling
- School of Biomedical Sciences, University of Ulster, Coleraine, Co., Londonderry, UK.
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266
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Abstract
Quinolones are one of the largest classes of antimicrobial agents used worldwide. This review considers the quinolones that are available currently and used widely in Europe (norfoxacin, ciprofloxacin, ofloxacin, levofloxacin and moxifloxacin) within their historical perspective, while trying to position them in the context of recent and possible future advances based on an understanding of: (1) their chemical structures and how these impact on activity and toxicity; (2) resistance mechanisms (mutations in target genes, efflux pumps); (3) their pharmacodynamic properties (AUC/MIC and Cmax/MIC ratios; mutant prevention concentration and mutant selection window); and (4) epidemiological considerations (risk of emergence of resistance, clonal spread). Their main indications are examined in relation to their advantages and drawbacks. Overall, it is concluded that these important agents should be used in an educated fashion, based on a careful balance between their ease of use and efficacy vs. the risk of emerging resistance and toxicity. However, there is now substantial evidence to support use of the most potent drug at the appropriate dose whenever this is required.
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Affiliation(s)
- F Van Bambeke
- Unit of Cellular and Molecular Pharmacology, Catholic University of Louvain, Brussels.
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267
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Deresinski S. In the Literature. Clin Infect Dis 2005. [DOI: 10.1086/432914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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