Emergence of fluoroquinolone resistance in Campylobacter jejuni and Campylobacter coli in subjects from Finland

Antibiotic Resistance in Bacteria—A Review

Background: A global problem of multi-drug resistance (MDR) among bacteria is the cause of hundreds of thousands of deaths every year. In response to the significant increase of MDR bacteria, legislative measures have widely been taken to limit or eliminate the use of antibiotics, including in the form of feed additives for livestock, but also in metaphylaxis and its treatment, which was the subject of EU Regulation in 2019/6. Numerous studies have documented that bacteria use both phenotypis and gentic strategies enabling a natural defence against antibiotics and the induction of mechanisms in increasing resistance to the used antibacterial chemicals. The mechanisms presented in this review developed by the bacteria have a significant impact on reducing the ability to combat bacterial infections in humans and animals. Moreover, the high prevalence of multi-resistant strains in the environment and the ease of transmission of drug-resistance genes between the different bacterial species including commensal flora and pathogenic like foodborne pathogens (E. coli, Campylobacter spp., Enterococcus spp., Salmonella spp., Listeria spp., Staphylococcus spp.) favor the rapid spread of multi-resistance among bacteria in humans and animals. Given the global threat posed by the widespread phenomenon of multi-drug resistance among bacteria which are dangerous for humans and animals, the subject of this study is the presentation of the mechanisms of resistance in most frequent bacteria called as “foodborne pathoges” isolated from human and animals. In order to present the significance of the global problem related to multi-drug resistance among selected pathogens, especially those danger to humans, the publication also presents statistical data on the percentage range of occurrence of drug resistance among selected bacteria in various regions of the world. In addition to the phenotypic characteristics of pathogen resistance, this review also presents detailed information on the detection of drug resistance genes for specific groups of antibiotics. It should be emphasized that the manuscript also presents the results of own research i.e., Campylobacter spp., E. coli or Enetrococcus spp. This subject and the presentation of data on the risks of drug resistance among bacteria will contribute to initiating research in implementing the prevention of drug resistance and the development of alternatives for antimicrobials methods of controlling bacteria.

Transferable Mechanisms of Quinolone Resistance from 1998 Onward

While the description of resistance to quinolones is almost as old as these antimicrobial agents themselves, transferable mechanisms of quinolone resistance (TMQR) remained absent from the scenario for more than 36 years, appearing first as sporadic events and afterward as epidemics. In 1998, the first TMQR was soundly described, that is, QnrA. The presence of QnrA was almost anecdotal for years, but in the middle of the first decade of the 21st century, there was an explosion of TMQR descriptions, which definitively changed the epidemiology of quinolone resistance. Currently, 3 different clinically relevant mechanisms of quinolone resistance are encoded within mobile elements: (i) target protection, which is mediated by 7 different families of Qnr (QnrA, QnrB, QnrC, QnrD, QnrE, QnrS, and QnrVC), which overall account for more than 100 recognized alleles; (ii) antibiotic efflux, which is mediated by 2 main transferable efflux pumps (QepA and OqxAB), which together account for more than 30 alleles, and a series of other efflux pumps (e.g., QacBIII), which at present have been sporadically described; and (iii) antibiotic modification, which is mediated by the enzymes AAC(6')Ib-cr, from which different alleles have been claimed, as well as CrpP, a newly described phosphorylase.

Antimicrobial resistance mechanisms among Campylobacter

Campylobacter jejuni and Campylobacter coli are recognized as the most common causative agents of bacterial gastroenteritis in the world. Humans most often become infected by ingesting contaminated food, especially undercooked chicken, but also other sources of bacteria have been described. Campylobacteriosis is normally a self-limiting disease. Antimicrobial treatment is needed only in patients with more severe disease and in those who are immunologically compromised. The most common antimicrobial agents used in the treatment of Campylobacter infections are macrolides, such as erythromycin, and fluoroquinolones, such as ciprofloxacin. Tetracyclines have been suggested as an alternative choice in the treatment of clinical campylobacteriosis but in practice are not often used. However, during the past few decades an increasing number of resistant Campylobacter isolates have developed resistance to fluoroquinolones and other antimicrobials such as macrolides, aminoglycosides, and beta-lactams. Trends in antimicrobial resistance have shown a clear correlation between use of antibiotics in the veterinary medicine and animal production and resistant isolates of Campylobacter in humans. In this review, the patterns of emerging resistance to the antimicrobial agents useful in treatment of the disease are presented and the mechanisms of resistance to these drugs in Campylobacter are discussed.

Campylobacter spp. as a Foodborne Pathogen: A Review

Campylobacter is well recognized as the leading cause of bacterial foodborne diarrheal disease worldwide. Symptoms can range from mild to serious infections of the children and the elderly and permanent neurological symptoms. The organism is a cytochrome oxidase positive, microaerophilic, curved Gram-negative rod exhibiting corkscrew motility and is carried in the intestine of many wild and domestic animals, particularly avian species including poultry. Intestinal colonization results in healthy animals as carriers. In contrast with the most recent published reviews that cover specific aspects of Campylobacter/campylobacteriosis, this broad review aims at elucidating and discussing the (i) genus Campylobacter, growth and survival characteristics; (ii) detection, isolation and confirmation of Campylobacter; (iii) campylobacteriosis and presence of virulence factors; and (iv) colonization of poultry and control strategies.

Prevalence, antibiograms, and transferable tet(O) plasmid of Campylobacter jejuni and Campylobacter coli isolated from raw chicken, pork, and human clinical cases in Korea

The antibiotic resistance patterns and prevalence of the transferable tet(O) plasmid were investigated in Campylobacter jejuni and Campylobacter coli isolates from raw chicken, pork, and humans with clinical campylobacteriosis. A total of 180 C. jejuni and C. coli isolates were identified, and the prevalence rates of C. jejuni and C. coli in raw chicken samples were 83% (83 of 100) and 73% (73 of 100), respectively. Twelve percent (6 of 50) and 10% (5 of 50) of pork samples were contaminated with C. jejuni and C. coli, respectively. Disk diffusion susceptibility testing revealed that the most frequently detected resistance was to tetracycline (92.2%), followed by nalidixic acid (75.6%), ciprofloxacin (65.0%), azithromycin (41.5%), ampicillin (33.3%), and streptomycin (26.1%). Of the C. jejuni and C. coli isolates, 65.7% (n=109) contained plasmids carrying the tet(O) gene. Six C. jejuni isolates and two C. coli isolates with high-level resistance to tetracycline (MIC=256 microg/ml) harbored the tet(O) plasmid, which is transferable to other C. jejuni and C. coli isolates. These results demonstrate the presence of an interspecies transferable plasmid containing the tet(O) gene and a high prevalence of antibiotic resistance in Korean Campylobacter isolates and provide an understanding of the antibiotic resistance distribution among Campylobacter species in Korea.

A survey of fluoroquinolone resistance in Escherichia coli and thermophilic Campylobacter spp. on poultry and pig farms in Great Britain

AIMS

To estimate the proportions of farms on which broilers, turkeys and pigs were shedding fluoroquinolone (FQ)-resistant Escherichia coli or Campylobacter spp. near to slaughter.

METHODS AND RESULTS

Freshly voided faeces were collected on 89 poultry and 108 pig farms and cultured with media containing 1.0 mg l(-1) ciprofloxacin. Studies demonstrated the specificity of this sensitive method, and both poultry and pig sampling yielded FQ-resistant E. coli on 60% of farms. FQ-resistant Campylobacter spp. were found on around 22% of poultry and 75% of pig farms. The majority of resistant isolates of Campylobacter (89%) and E. coli (96%) tested had minimum inhibitory concentrations for ciprofloxacin of > or =8 mg l(-1). The proportion of resistant E. coli and Campylobacter organisms within samples varied widely.

CONCLUSIONS

FQ resistance is commonly present among two enteric bacterial genera prevalent on pig and poultry farms, although the low proportion of resistant organisms in many cases requires a sensitive detection technique.

SIGNIFICANCE AND IMPACT OF THE STUDY

FQ-resistant bacteria with zoonotic potential appear to be present on a high proportion of UK pig and poultry farms. The risk this poses to consumers relative to other causes of FQ-resistant human infections remains to be clarified.

Key role of Mfd in the development of fluoroquinolone resistance in Campylobacter jejuni

Campylobacter jejuni is a major food-borne pathogen and a common causative agent of human enterocolitis. Fluoroquinolones are a key class of antibiotics prescribed for clinical treatment of enteric infections including campylobacteriosis, but fluoroquinolone-resistant Campylobacter readily emerges under the antibiotic selection pressure. To understand the mechanisms involved in the development of fluoroquinolone-resistant Campylobacter, we compared the gene expression profiles of C. jejuni in the presence and absence of ciprofloxacin using DNA microarray. Our analysis revealed that multiple genes showed significant changes in expression in the presence of a suprainhibitory concentration of ciprofloxacin. Most importantly, ciprofloxacin induced the expression of mfd, which encodes a transcription-repair coupling factor involved in strand-specific DNA repair. Mutation of the mfd gene resulted in an approximately 100-fold reduction in the rate of spontaneous mutation to ciprofloxacin resistance, while overexpression of mfd elevated the mutation frequency. In addition, loss of mfd in C. jejuni significantly reduced the development of fluoroquinolone-resistant Campylobacter in culture media or chickens treated with fluoroquinolones. These findings indicate that Mfd is important for the development of fluoroquinolone resistance in Campylobacter, reveal a previously unrecognized function of Mfd in promoting mutation frequencies, and identify a potential molecular target for reducing the emergence of fluoroquinolone-resistant Campylobacter.

Activities of telithromycin, erythromycin, fluoroquinolones, and doxycycline against Campylobacter strains isolated from Finnish subjects

The in vitro susceptibilities of 478 Campylobacter jejuni and Campylobacter coli strains isolated from Finnish subjects during 2002 to 2004 were determined. Susceptibility to erythromycin remained high, and telithromycin did not offer any advantage over erythromycin. Reduced susceptibilities to fluoroquinolones and doxycycline were detected almost exclusively among isolates of foreign origin.

Acquisition of quinolone resistance and point mutation of the gyrA gene in Campylobacter jejuni isolated from broilers and in vitro-induced resistant strains

A dramatic rise in the number of resistant Campylobacter to quinolones has been documented in human patients and domestic animals. In this study, the mechanism of acquisition of quinolone resistance was studied by detecting point mutations in the gyrA gene of Campylobacter strains obtained from broilers and strains with in vitro-induced resistance. The minimal inhibitory concentrations (MICs) of norfloxacin (NFLX) and ofloxacin (OFLX) for the strains that had no point mutation were slightly increased from the source strain (Campylobacter jejuni ATCC 33560). The MICs of nalidixic acid (NA), NFLX, and OFLX for the strains that had the point mutation at Thr-86 were 100 or 200 microg/ml, 50 microg/ml, and 25 microg/ml, respectively. The MIC of NA for the strain that had a point mutation at Asp-90 higher than those for the strains that had the point mutation at Thr-86, but the MICs of NFLX and OFLX were relatively lower than those for the strains that had point mutation at Thr-86. These findings suggest that the degree of antimicrobial resistance against NA, NFLX, and OFLX in the in vitro-induced C. jejuni strains was associated with the location of the point mutation in gyrA. On the other hand, a point mutation in all seven resistant strains isolated from broilers was located only at Thr-86, while the MICs of the three quinolones varied in each wild strain. This suggests that another mechanism might also be involved in the acquisition of quinolone resistance in C. jejuni wild strains.

Public health consequences of macrolide use in food animals: a deterministic risk assessment

The potential impact on human health from antibiotic-resistant bacteria selected by use of antibiotics in food animals has resulted in many reports and recommended actions. The U.S. Food and Drug Administration Center for Veterinary Medicine has issued Guidance Document 152, which advises veterinary drug sponsors of one potential process for conducting a qualitative risk assessment of drug use in food animals. Using this guideline, we developed a deterministic model to assess the risk from two macrolide antibiotics, tylosin and tilmicosin. The scope of modeling included all label claim uses of both macrolides in poultry, swine, and beef cattle. The Guidance Document was followed to define the hazard, which is illness (i) caused by foodborne bacteria with a resistance determinant, (ii) attributed to a specified animal-derived meat commodity, and (iii) treated with a human use drug of the same class. Risk was defined as the probability of this hazard combined with the consequence of treatment failure due to resistant Campylobacter spp. or Enterococcus faecium. A binomial event model was applied to estimate the annual risk for the U.S. general population. Parameters were derived from industry drug use surveys, scientific literature, medical guidelines, and government documents. This unique farm-to-patient risk assessment demonstrated that use of tylosin and tilmicosin in food animals presents a very low risk of human treatment failure, with an approximate annual probability of less than 1 in 10 million Campylobacter-derived and approximately 1 in 3 billion E. faecium-derived risk.

Risk factors for antibiotic resistance in Campylobacter spp. isolated from raw poultry meat in Switzerland

Background

The world-wide increase of foodborne infections with antibiotic resistant pathogens is of growing concern and is designated by the World Health Organization as an emerging public health problem. Thermophilic Campylobacter have been recognised as a major cause of foodborne bacterial gastrointestinal human infections in Switzerland and in many other countries throughout the world. Poultry meat is the most common source for foodborne cases caused by Campylobacter. Because all classes of antibiotics recommended for treatment of human campylobacteriosis are also used in veterinary medicine, in view of food safety, the resistance status of Campylobacter isolated from poultry meat is of special interest.

Methods

Raw poultry meat samples were collected throughout Switzerland and Liechtenstein at retail level and examined for Campylobacter spp. One strain from each Campylobacter-positive sample was selected for susceptibility testing with the disc diffusion and the E-test method. Risk factors associated with resistance to the tested antibiotics were analysed by multiple logistic regression.

Results

In total, 91 Campylobacter spp. strains were isolated from 415 raw poultry meat samples. Fifty-one strains (59%) were sensitive to all tested antibiotics. Nineteen strains (22%) were resistant to a single, nine strains to two antibiotics, and eight strains showed at least three antibiotic resistances. Resistance was observed most frequently to ciprofloxacin (28.7%), tetracycline (12.6%), sulphonamide (11.8%), and ampicillin (10.3%). One multiple resistant strain exhibited resistance to five antibiotics including ciprofloxacin, tetracycline, and erythromycin. These are the most important antibiotics for treatment of human campylobacteriosis. A significant risk factor associated with multiple resistance in Campylobacter was foreign meat production compared to Swiss meat production (odds ratio = 5.7).

Conclusion

Compared to the situation in other countries, the data of this study show a favourable resistance situation for Campylobacter strains isolated from raw poultry meat produced in Switzerland. Nevertheless, the prevalence of 19% ciprofloxacin resistant strains is of concern and has to be monitored. "Foreign production vs. Swiss production" was a significant risk factor for multiple resistance in the logistic regression model. Therefore, an adequate resistance-monitoring programme should include meat produced in Switzerland as well as imported meat samples.

Susceptibilities of Campylobacter jejuni isolates from Germany to ciprofloxacin, moxifloxacin, erythromycin, clindamycin, and tetracycline

To elucidate Campylobacter jejuni resistance to antibiotics in Germany, MICs of ciprofloxacin, moxifloxacin, erythromycin, clindamycin, and tetracycline were determined (using agar dilution) for 144 clinical isolates. The data indicate a considerable ciprofloxacin resistance (45.1%) without a clonal relationship of the strains and a greater in vitro activity of moxifloxacin, erythromycin, and clindamycin.

Antimicrobial resistance of Campylobacter jejuni and Campylobacter coli isolates from broiler chickens isolated at an Irish poultry processing plant

AIMS

The antibiotic susceptibility of Campylobacter jejuni and Campylobacter coli isolates from broiler chickens were determined in order to evaluate the level of antibiotic resistance of Campylobacter species in the Irish poultry industry.

METHODS AND RESULTS

Seventy-eight Camp. jejuni and 22 Camp. coli strains were examined for susceptibility to eight antibiotics using the disc diffusion assay. The highest level of resistance of the Camp. jejuni isolates was recorded to ampicillin (35.9%), followed by 20.5% to tetracycline, 20.5% to naladixic acid, 17.9% to ciprofloxacin, 10.2% to erythromycin, 2.5% to streptomycin and 1.2% to kanamycin. Multidrug resistance to two or more antibiotics was seen for 30.7% of Camp. jejuni strains. Resistance of the Camp. coli isolates was shown to ampicillin (9%) and tetracycline (18.2%).

CONCLUSIONS

The majority of Camp. jejuni strains were susceptible to antibiotics commonly used for human therapy. Camp. coli strains showed very low resistance levels and were susceptible to six of the eight antimicrobial agents studied.

SIGNIFICANCE AND IMPACT OF THE STUDY

Levels of Camp. jejuni and Camp. coli antimicrobial resistance in Irish poultry production was assessed to determine the current situation in Ireland. The prevalence of antibiotic resistance of Campylobacter strains isolated from broiler chickens was low.

Occurrence and resistance to antibiotics of Campylobacter jejuni and Campylobacter coli in animals and meat in northeastern Italy

A study was carried out in northeastern Italy during 2000 and 2001 to investigate the occurrence of Campylobacter jejuni and Campylobacter coli in animals, cattle, pigs, and broilers, and raw meat, beef, pork, and chicken. Campylobacter spp. were detected in 53.9% of the cattle, 63.5% of the pigs, and 82.9% of the broilers examined. Chicken meat was frequently contaminated (81.3%), while lower rates were found in pork meat (10.3%) and beef (1.3%). The resistance to antibiotics of the strains was also investigated, and compared to that of human clinical isolates. C. coli was generally more resistant than C. jejuni. Resistance to quinolones was frequently observed in C. coli isolated in chicken meat (78.6%); slightly lower rates were found in C. jejuni isolated in broilers (42.2%), chicken meat (52.8%), and humans (38.2%). C. coli was also frequently resistant to tetracycline in all sources, while resistance to streptomycin was most frequently observed in pig isolates (89.4%).

Travellers' diarrhoea

Risk of travellers' diarrhoea is about 7% in developed countries and 20-50% in the developing world. Options for prevention include education and chemoprophylaxis. Vaccination is a promising but incomplete option. Achieving behaviour modification of food and water choices among tourists is difficult. Bismuth subsalicylate (BSS)-containing compounds are about 62% effective in the prevention of travellers' diarrhoea. Antibiotics are about 84% effective in preventing travellers' diarrhoea. Routine prophylaxis of travellers' diarrhoea, especially with antibiotics, should be discouraged. Oral rehydration is generally important in the treatment of diarrhoea, but travellers' diarrhoea is only infrequently dehydrating in adults. The addition of oral rehydration solutions confers no additional benefit to loperamide in the treatment of travellers' diarrhoea in adults. Presently, the most active of the antibiotics routinely available for treatment are members of the fluoroquinolone group. Antibiotics that are not absorbed such as aztreonam and a rifampicin-like agent, rifaximin, are both effective. The latter might become a therapy of choice once it is routinely available, due to predictably less adverse reactions with a non-absorbed antibiotic. Preliminary results with azithromycin look very promising. Less severe disease can be treated with a variety of non-antibiotic agents (e.g. BSS-containing compounds, loperamide and a calmodulin inhibitor, zaldaride). The combination of an antibiotic and loperamide is superior to treatment with either agent alone in a several studies and is arguably the treatment of choice for distressing travellers' diarrhoea.

Antimicrobial susceptibilities of Campylobacter strains isolated from Finnish subjects infected domestically or from those infected abroad

The in vitro susceptibilities of 678 Campylobacter jejuni and Campylobacter coli strains isolated from stool samples of the same number of Finnish subjects were studied. A total of 523 patients, representing inhabitants from throughout Finland, had not traveled abroad within the 2 weeks prior to becoming ill, whereas 155 persons had presumably acquired their infections abroad. The antimicrobial agents studied were erythromycin, ciprofloxacin, levofloxacin, trovafloxacin, and moxifloxacin. The MICs of these antimicrobial agents were determined by the agar dilution method. The growth of all domestic isolates was inhibited by erythromycin at concentrations of 4 microg/ml, and for these isolates the fluoroquinolone MICs at which 90% of isolates are inhibited (MIC(90)s) ranged from 0.06 to 0.5 microg/ml. For the foreign isolates, the erythromycin MIC(90) was still low (4 microg/ml), but their susceptibilities to fluoroquinolones were clearly reduced (MIC(90)s, 8 to 64 microg/ml). Of the four different fluoroquinolones studied, ciprofloxacin was the least active (MIC(90), 64 micro g/ml).

gyrA polymorphism in Campylobacter jejuni: detection of gyrA mutations in 162 C. jejuni isolates by single-strand conformation polymorphism and DNA sequencing

Mutations in the quinolone resistance-determining region of the gyrA gene from 138 ciprofloxacin-resistant (MIC, > or =4 microg/ml) and 24 ciprofloxacin-susceptible (MIC, < or =1 microg/ml) clinical Campylobacter jejuni isolates were subjected to single-strand conformation polymorphism analysis and sequencing. All of the isolates could be assigned to three genotypic clusters based on silent mutations. All resistant isolates had a point mutation at codon 86.

Antimicrobial susceptibilities of Campylobacter strains isolated from broilers in the southern part of Japan from 1995 to 1999

Cecal contents (16 samples/each flock) of broilers derived from 212 flocks were investigated for colonization of Campylobacter from 1995 to 1999 in the southern part of Japan, and the isolates were tested for antimicrobial susceptibilities. C. jejuni-positive flocks numbered 42 (19.8%) and C. coli-positive ones 26 (12.3%); Campylobacter spp. were recovered from 68 flocks (32.1%) in total. MICs of ampicillin, erythromycin (EM), tetracycline, nalidixic acid (NA), norfloxacin (NFLX), and ofloxacin (OFLX) to these 68 Campylobacter isolates were determined. Quinolone-resistant Campylobacter isolates numbered 22 (32.4%). All the isolates except one were cross-resistant to NA, OFLX, and NFLX. A high frequency of quinolone-resistance was found in both C. jejuni and C. coli, whereas a high level of EM-resistance was found in only C. coli strains. All C. jejuni isolates were sensitive to EM.

Quinolone and macrolide resistance in Campylobacter jejuni and C. coli: resistance mechanisms and trends in human isolates

The incidence of human Campylobacter jejuni and C. coli infections has increased markedly in many parts of the world in the last decade as has the number of quinolone-resistant and, to a lesser extent, macrolide-resistant Campylobacter strains causing infections. We review macrolide and quinolone resistance in Campylobacter and track resistance trends in human clinical isolates in relation to use of these agents in food animals. Susceptibility data suggest that erythromycin and other macrolides should remain the drugs of choice in most regions, with systematic surveillance and control measures maintained, but fluoroquinolones may now be of limited use in the empiric treatment of Campylobacter infections in many regions.

Campylobacters: the most common bacterial enteropathogens in the Nordic countries

Campylobacters have been known as important human pathogens since the late 1970s. Campylobacter jejuni and coli are the most common bacterial enteropathogens in the developed countries. During the past years an increasing incidence of campylobacteriosis has been reported in many developed countries. C. jejuni is the most common Campylobacter species while C. coli accounts for about 5-10% of the cases. Although the genome of C. jejuni NCTC 11168 strain was sequenced recently, the exact pathogenetic mechanisms are still not known. Furthermore, there are no reliable animal models available. The epidemiology of this common infection is not well understood; however, eating and handling poultry, contaminated drinking water, and contact with pet animals have been recognized as important risk factors. Most of the cases are sporadic although large water-borne outbreaks have also been reported. Discriminatory typing methods are helpful in tracing the sources and transmission routes. In addition to traditional serotyping, genotyping methods, such as pulsed-field gel electrophoresis, have been developed. As Campylobacter infections probably precede Guillan-Barré syndrome in many cases, a great interest has lately been focused on the possible triggering mechanisms underlying this phenomenon.

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.

Infectious diarrhea

Infectious diarrhea is an extremely common illness that affects millions of Americans annually. For most patients, the illness is a self-limited one. Its major risk is dehydration. However, for some patients, diarrhea can lead to severe dehydration or be associated with bacteremia and metastatic infection. Patients with these conditions require prompt treatment. A large number of organisms have been associated with diarrhea in humans, and most laboratories routinely screen for Salmonella, Shigella, and Campylobacter. Other bacteria, parasites, and viruses account for a significant percentage of diarrhea cases and frequently go undetected. This article summarizes many of these pathogens and describes the settings in which they can be acquired. Food distribution networks have made the delivery of previously rare foods to remote areas a commonplace occurrence; this has also led to new challenges in the diagnosis and prevention of food-borne illnesses. Outbreaks of diarrhea now frequently extend across many states. The identification of a rare strain of a bacterial pathogen or changes in the isolation rate of common pathogens may be early clues to the cause of such an ongoing outbreak. Most enteric pathogens cause disease by either stimulating the secretion of fluids at the level of the small bowel or by irritating and invading the colon. Organisms that cause disease by the latter mechanism have the potential to invade the blood stream and spread to other parts of the body, including the bones and the central nervous system. Several organisms have been associated with specific postinfectious syndromes that are responsible for additional morbidity and mortality. The antibiotic resistance of bacterial pathogens has been increasing, and this has a limiting effect on the empiric treatment choices available for suspected bacterial diarrhea. Careful attention to local sensitivity patterns and appropriate testing of the patient's isolate are among the important factors that lead to successful treatment decisions.

The effects of antibiotic usage in food animals on the development of antimicrobial resistance of importance for humans in Campylobacter and Escherichia coli

Modern food animal production depends on use of large amounts of antibiotics for disease control. This provides favourable conditions for the spread and persistence of antimicrobial-resistant zoonotic bacteria such as Campylobacter and E. coli O157. The occurrence of antimicrobial resistance to antimicrobials used in human therapy is increasing in human pathogenic Campylobacter and E. coli from animals. There is an urgent need to implement strategies for prudent use of antibiotics in food animal production to prevent further increases in the occurrence of antimicrobial resistance in food-borne human pathogenic bacteria such as Campylobacter and E. coli.

Quinolone-resistant Campylobacter jejuni infections in Minnesota, 1992-1998. Investigation Team

BACKGROUND

Increasing resistance to quinolones among campylobacter isolates from humans has been reported in Europe and Asia, but not in the United States. We evaluated resistance to quinolones among campylobacter isolates from Minnesota residents during the period from 1992 through 1998.

METHODS

All 4953 campylobacter isolates from humans received by the Minnesota Department of Health were tested for resistance to nalidixic acid. Resistant isolates and selected sensitive isolates were tested for resistance to ciprofloxacin. We conducted a case-comparison study of patients with ciprofloxacin-resistant Campylobacter jejuni isolated during 1996 and 1997. Domestic chicken was evaluated as a potential source of quinolone-resistant campylobacter.

RESULTS

The proportion of quinolone-resistant C. jejuni isolates from humans increased from 1.3 percent in 1992 to 10.2 percent in 1998 (P<0.001). During 1996 and 1997, infection with quinolone-resistant C. jejuni was associated with foreign travel and with the use of a quinolone before the collection of stool specimens. However, quinolone use could account for no more than 15 percent of the cases from 1996 through 1998. The number of quinolone-resistant infections that were acquired domestically also increased during the period from 1996 through 1998. Ciprofloxacin-resistant C. jejuni was isolated from 14 percent of 91 domestic chicken products obtained from retail markets in 1997. Molecular subtyping showed an association between resistant C. jejuni strains from chicken products and domestically acquired infections in Minnesota residents.

CONCLUSIONS

The increase in quinolone-resistant C. jejuni infections in Minnesota is largely due to infections acquired during foreign travel. However, the number of quinolone-resistant infections acquired domestically has also increased, largely because of the acquisition of resistant strains from poultry. The use of fluoroquinolones in poultry, which began in the United States in 1995, has created a reservoir of resistant C. jejuni.

Antimicrobial resistance of clinical strains of Campylobacter jejuni subsp. jejuni isolated from 1985 to 1997 in Quebec, Canada

The antimicrobial resistance of 158 Campylobacter jejuni strains isolated from humans in Quebec, Canada, from 1995 to 1997 was compared to the resistance of 47 and 86 strains of C. jejuni isolated in 1985 and 1986 and in 1992 and 1993, respectively. Of the 291 C. jejuni strains tested, no strain was resistant to erythromycin. Compared to the C. jejuni strains isolated in 1985 and 1986, the C. jejuni strains isolated in 1992 and 1993 were more resistant to tetracycline (40.7 versus 19.1%, respectively; P = 0. 01) but not to nalidixic acid or ciprofloxacin (P > 0.05). Compared to the C. jejuni strains isolated in 1992 and 1993 and in 1985 and 1986, the C. jejuni strains isolated from 1995 to 1997 were more resistant to tetracycline (55.7% versus 40.7 and 19.1%, respectively; P = 0.03 and P < 0.001, respectively) to nalidixic acid (13.9% versus 4.7 and 0%, respectively; P = 0.02 and P = 0.007, respectively), and to ciprofloxacin (12.7% versus 3.5 and 0%, respectively; P = 0.02 and P = 0.009, respectively).

Resistance to antimicrobial agents used for animal therapy in pathogenic-, zoonotic- and indicator bacteria isolated from different food animals in Denmark: a baseline study for the Danish Integrated Antimicrobial Resistance Monitoring Programme (DANMAP)

This study describes the establishment and first results of a continuous surveillance system of antimicrobial resistance among bacteria isolated from pigs, cattle and broilers in Denmark. The three categories of bacteria tested were: 1) indicator bacteria (Escherichia coli, Enterococcus faecalis, Enterococcus faecium), 2) zoonotic bacteria (Campylobacter coli/jejuni, Salmonella enterica, Yersinia enterocolitica), and 3) animal pathogens (E. coli, Staphylococcus aureus, coagulase-negative staphylococci (CNS), Staphylococcus hyicus, Actinobacillus pleuropneumoniae). A total of 3304 bacterial isolates collected from October 1995 through December 1996 were tested for susceptibility to all major classes of antimicrobial agents used for therapy in Denmark. Bacterial species intrinsically resistant to an antimicrobial were not tested towards that antimicrobial. Acquired resistance to all antimicrobials was found. The occurrence of resistance varied by animal origin and bacterial species. In general, resistance was observed more frequently among isolates from pigs than from cattle and broilers. The association between the occurrence of resistance and the consumption of the antimicrobial is discussed, as is the occurrence of resistance in other countries. The results of this study show the present level of resistance to antimicrobial agents among a number of bacterial species isolated from food animals in Denmark. Thus, the baseline for comparison with future prospective studies has been established, enabling the determination of trends over time.

Travelers' diarrhea. Epidemiology, prevention, and self-treatment

Risk factors for travelers' diarrhea include adventurous behavior, consumption of unclean water or food, and special hosts like those taking long acting H2 blockers. Approaches to prevention include education about risk factors, which often fails to lead to modification of risky behavior, and chemoprophylaxis with bismuth subsalicylate-containing compounds or antimicrobial agents. Chemoprophylaxis is generally discouraged except in special circumstances and in high-risk hosts. Self-treatment of travelers' diarrhea is successful in limiting the course of diarrhea and minimizing losses of vacation and business time. Current therapeutic options, in order of increasing effectiveness, include attapulgite, BSS-containing compounds, loperamide, antimicrobial agents such as the fluoroquinolones, and the combination of loperamide and an antimicrobial agent. Under study are a nonabsorbed antimicrobial agent, rifaximin, and a novel calmodulin inhibitor, zaldaride. Development and evaluation of vaccines against enterotoxigenic Escherichia coli and Shigella are proceeding apace but are not yet available for routine use.

Typing of human Campylobacter jejuni isolates in Finland by pulsed-field gel electrophoresis

A total of 69 pulsed-field gel electrophoresis (PFGE) types were identified among 176 Campylobacter jejuni isolates from Finnish patients. In two geographic areas studied, five predominant PFGE types comprised over 40% of the isolates. One-third of the isolates had unique PFGE types. In small outbreaks, identical PFGE patterns were demonstrated, indicating a common source of infection.

Purulent pleurisy caused by Campylobacter lari

An 80-year-old debilitated patient developed purulent pleurisy caused by a Campylobacter lari isolate. The patient underwent surgical drainage and received antibiotic therapy with amoxicillin/clavulanic acid and ofloxacin. Antibiotic susceptibility data showed that the isolate was fully sensitive to clarithromycin, tetracycline, aminoglycosides. and ciprofloxacin. Imipenem and amoxicillin plus clavulanic acid were the most active beta-lactam agents.

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.

Disc susceptibility testing for thermomphilic campylobacters

The minimum inhibitory concentrations (MICs) and zone diameters around NCCLS strength discs of 100 clinical isolates of thermophilic Campylobacter species, including 79 strains of Campylobacter jejuni subsp. jejuni, 19 of C. coli and two of C. lari, plus three type strains of these species, were determined for erythromycin, clindamycin, nalidixic acid, norfloxacin, ciprofloxacin, ampicillin, piperacillin, cephalothin, ceftriaxone, chloramphenicol, gentamicin and tetracycline. Using error-rate bounded analysis and adjustment of MIC breakpoints to fit natural populations, tentative interpretive zone diameter criteria were set for each of the antimicrobials. Application of these criteria showed that resistance to quinolones was not detected in species other than C. lari. Two strains of C. jejuni subsp. jejuni were susceptible to cephalothin. The type strain of C. lari was susceptible to erythromycin and resistant to clindamycin. Full resistance to erythromycin, chloramphenicol or gentamicin was not found in any strain, while nine strains were resistant to tetracycline. This disc method should provide a simple approach to resistance detection for surveillance or routine testing of invasive isolates.

Sequential development of resistance to fluoroquinolones and erythromycin in an isolate of Campylobacter jejuni

A severe episode of Campylobacter jejuni gastroenteritis in a patient with HIV infection was treated with ciprofloxacin and, because of therapeutic failure, subsequently with roxithromycin. After treatment, C. jejuni was again isolated from feces and shown to be resistant to both drugs. We present molecular evidence of the sequential development of both types of resistance in the patient isolate. To our knowledge, this is the first case with documented evidence showing sequential emergence of resistance to fluoroquinolones and erythromycin in a strain of C. jejuni during treatment.

Reasons for the emergence of antibiotic resistance

The ability of many different species of bacteria, including those that cause diseases in humans, to resist the inhibitory action of antimicrobial agents has become a global problem. Resistance continues to spread not only in nosocomial pathogens but in several key community-acquired organisms as well. Appropriate control measures for such resistant organisms depend in part on the pathways by which resistance has arisen. Unfortunately, these pathways differ greatly from organism to organism and setting to setting. In addition, although the epidemiology of resistant organisms sometimes is similar to that of susceptible organisms of the same kind, in some situations it may be quite different. In this article, the authors highlight some of the pathways leading to the development of resistance in bacteria, the importance of antimicrobial use, and the relevance of these mechanisms to measures for the control of resistant bacteria in hospital and community settings.

Antibiotic susceptibility of campylobacter isolates from sewage and poultry abattoir drain water

In this study, the in vitro susceptibility of 209 campylobacter strains to the quinolones nalidixic acid, flumequine, ciprofloxacin, enrofloxacin, and to ampicillin, tetracycline and erythromycin was tested by the disk diffusion method. The strains were isolated from poultry abattoir effluent (DWA) and two sewage purification plants (SPA and SPB). Sewage purification plant SPA received mixed sewage, including that from a poultry abattoir, whereas SPB did not receive sewage from any meat-processing industry. The quinolone resistance of the DWA isolates ranged from 28% for enrofloxacin to 50% for nalidixic acid. The strains isolated from the sewage purification plants were more susceptible to the quinolones with a range of 11-18% quinolone resistance for SPB isolates to 17-33% quinolone resistance for SPA isolates. The susceptibility criteria as recommended by National Committee Clinical Laboratory Standards (USA) cannot readily be employed for campylobacter isolates. This investigation shows that the resistance of campylobacter bacteria is highest in the plant receiving sewage from a poultry slaughterhouse. Monitoring of antibiotic resistance of aquatic Campylobacter spp. is important, as surface waters are recognized as possible sources of infection.

The best of times, the worst of times. The global challenge of antimicrobial resistance

The development of resistance to antimicrobial agents by many bacterial pathogens has compromised traditional therapeutic regimens, making treatment of infections more difficult and frequently more expensive. Three factors have contributed to the development and spread of resistance: mutations in common genes that extend their spectrum of resistance, transfer of resistance genes among diverse microorganisms and increases in selective pressures in and outside of the hospital environment that enhance the development of resistant organisms. Some new resistance mechanisms are difficult to detect in the laboratory. Thus, resistant microorganisms may go unnoticed until they are widely disseminated in a hospital. The challenge for pharmacists, microbiologists and physicians is not only to contain the spread of existing resistant organisms, but also to prevent the emergence of new resistant pathogens by encouraging the rational and prudent use of antimicrobial agents.

Susceptibilities of fluoroquinolone-resistant strains of Campylobacter jejuni to 11 oral antimicrobial agents

The resistance of Campylobacter jejuni strains to the fluoroquinolones is increasingly frequent, and in our area it reaches nearly 50%. We studied the susceptibilities of 60 of these strains to 11 oral antibiotics. All strains except one were susceptible to the macrolides tested, with azithromycin being the most active agent tested. Of the rest of the antibiotics studied, amoxicillin-clavulanic acid, clindamycin, and fosfomycin displayed good in vitro activities. Knowledge of the susceptibilities of these microorganisms to a varied group of oral agents is necessary in view of the appearance of multiresistant strains, such as those included in our series.

A survey of Campylobacter bacteremia in three Danish counties, 1989 to 1994

Over a 5-year period (April 1989 to March 1994) bacteremia caused by Campylobacter species was diagnosed in 15 patients in a population of 1.3 million in three counties in Jutland province, Denmark. The incidence was 0.2/100,000/year and the ratio of blood to fecal isolates, was 0.008. Campylobacter coli and Campylobacter jejuni accounted for 6 cases each, Campylobacter fetus for 2, and in 1 case the species diagnosis was uncertain. Seven patients were males and 8 females; median age was 42 (range 15-90) years. 11 patients had underlying disorders, including immunological, neoplastic and vascular disease. In a 67-year-old man a Starr-Edwards prosthesis of the aortic valve was probably infected by C. fetus, as recurrent bacteremia resolved following valve replacement. Eight patients had pyrexia and diarrhea, whereas 7 had pyrexia with only slight intestinal discomfort or none at all. In 4 patients the bacteremia was associated with cutaneous cellulitis or vasculitis. 14 of 15 patients survived. Campylobacter bacteremia seems to be more common in Denmark than hitherto thought.

Epidemiology of quinolone resistance: Europe and North and South America

After nearly 10 years of fluoroquinolone usage for a wide range of bacterial infections, a striking difference has been observed in the incidence of bacterial resistance to fluoroquinolones between bacteria responsible for community- and hospital-acquired infections, respectively. Resistance is only rarely encountered among common pathogens. In most studies, 97 to 100% of all pathogens are fully susceptible to fluoroquinolones. In contrast, resistance to fluoroquinolones has emerged and increased among bacteria responsible for nosocomial infections. The incidence of resistance to fluoroquinolones varies between bacterial species, clinical settings and countries, and is related to local epidemic spread of a few clones. The highest incidence of resistance is observed in Pseudomonas aeruginosa, Acinetobacter spp., Serratia marcescens and, particularly, methicillin-resistant Staphylococcus aureus (MRSA): some investigators have reported 95 to 100% fluoroquinolone resistance among MRSA. Follow-up of trends in the resistance to fluoroquinolones based upon surveillance programmes are needed.

In vitro susceptibility of Campylobacter and Salmonella isolates from broilers to quinolones, ampicillin, tetracycline, and erythromycin

Recently, an increased resistance of Campylobacter to fluoroquinolones, a newer class of antimicrobial agents in both human and veterinary medicine, has been reported. Campylobacter isolates (617) from 150 broiler flocks were tested for their susceptibility to cephalothin (control), ampicillin, tetracycline, erythromycin, and the quinolones nalidixic acid, flumequine, enrofloxacin, and ciprofloxacin by a disc diffusion method. Almost complete cross-resistance was found between the quinolones tested. Campylobacter isolates (181, 29%), originating from 55 flocks (37%), were quinolone resistant. Salmonella isolates (94) from 40 flocks were also tested for their antimicrobial susceptibility. Eight isolates (8.5%), from three broiler flocks (7.5%), showed resistance to nalidixic acid and flumequine (and tetracycline), but not to ciprofloxacin or enrofloxacin.

Susceptibilities to 10 antimicrobial agents of 1,220 Campylobacter strains isolated from 1987 to 1993 from feces of pediatric patients

We report the in vitro antibiotic susceptibility of 1,220 strains belonging to the thermotolerant Campylobacter species, isolated from the feces of pediatric patients with diarrhea in the period from 1987 to 1993. The strains were identified as 1,148 C. jejuni isolates and 72 C. coli isolates. The overall results show that the strains showed drug resistance as follows: 51.8% to ampicillin, 4.4% to clindamycin, 2.6% to chloramphenicol, 21.2% to tetracycline, and 1% to gentamicin. Twenty-one strains (1.7%) displayed resistance to the combination of amoxicillin-clavulanic acid, and 3.2% of the strains were resistant to erythromycin (MIC of > or = 4 micrograms/ml), with a notable difference according to the species under consideration. While C. jejuni remained stable at 0.9 to 4% resistance to erythromycin, for C. coli the percentages detected ranged from 0 to 33%, with overall rates of 2.5 and 15.2% for the two species, respectively. Resistance to nalidixic acid (MIC of > or = 32 micrograms/ml) was found in 27.2% of the strains (27.8% for C. jejuni and 18% for C. coli), and resistance to ciprofloxacin (MIC of > or = 4 micrograms/ml) was found in 24.2% of the strains for C. jejuni and 15.2% for C. coli). Cross-resistance between nalidixic acid and ciprofloxacin was found in 89.1% of the strains (type 1 mutants), while 10.9% were resistant to nalidixic acid but susceptible to ciprofloxacin (type 2 mutants).

Increase of ciprofloxacin resistance in Campylobacter species in Styria, Austria

Salmonella spp. and thermophilic Campylobacter spp. are the most important diarrhea-causing pathogens in the area investigated in Styria, Austria. The isolation rate of Campylobacter in the more than 62,000 stool specimens investigated in the six-year period between 1988 and 1993 ranged between 1.90% in 1988 and 3.58% in 1991. The testing of susceptibility to nalidixic acid has been an usual characteristic for species identification. Nalidixic acid-resistant strains were rare in 1988-1990, but in the summer of 1991, we found an increasing number of these isolates. At the same time, we learnt about the increasing use of enrofloxacin in veterinary medicine, especially in the poultry industry, and therefore we started routine testing of Campylobacter spp. susceptibility to ciprofloxacin in 1992. In 1992, the resistance rate to ciprofloxacin was already 16.9%, rising to 22.1% in 1993.