Prolonged diarrhea due to ciprofloxacin-resistant campylobacter infection

Antimicrobial activity of two propolis samples against human Campylobacter jejuni

The aim of this study was to analyze the antimicrobial activity of two ethanolic extracts of propolis (EEPs) and selected flavonoids against 16 Campylobacter jejuni clinical isolates and several Gram-positive and Gram-negative human pathogens. The antimicrobial activity of EEPs and flavonoids was evaluated by the agar well diffusion method. The EEPs inhibited the growth of C. jejuni, Enterobacter faecalis, and Staphylococcus aureus. The most active flavonoid was galangin, with the highest percentage of sensitivity among C. jejuni strains (68.8%); lower percentages of sensitivity were observed for quercetin (50%). The minimal inhibitory concentrations (MICs) of EEPs and flavonoids for C. jejuni isolates were determined by the agar dilution method. EEPs showed MIC values of 0.3125-0.156 mg/mL for all C. jejuni strains; galangin and quercetin gave MICs ranging from 0.250 to 0.125 mg/mL. Thus propolis preparations could be used as support to traditional therapy for Campylobacter infection, especially when the antibiotic agents show no activity against this microorganism.

The epidemiology of travelers' diarrhea in Incirlik, Turkey: a region with a predominance of heat-stabile toxin producing enterotoxigenic Escherichia coli

This study evaluated travelers' diarrhea among US military personnel on short-term deployment to Incirlik Air Base, Turkey, from June through September 2002. Upon reporting for care for travelers' diarrhea, subjects were enrolled into the study and completed a series of questionnaires and provided stool specimens for pathogen identification and antimicrobial susceptibility testing. Fifty-three percent of the 202 participating subjects had a pathogen isolated from their stool. Enterotoxigenic Escherichia coli (ETEC) was the predominant pathogen (41%), followed by Campylobacter spp. (12%). The most common ETEC phenotype recovered was stable toxin (ST) CS6 (47% of all ETEC). Most (91.1%) of the cases presented with water diarrhea regardless of isolated pathogen. However, there were some differences in nongastrointestinal symptoms among subjects with Campylobacter spp. All illnesses were well managed with antibiotics with or without loperamide with a median time to the last unformed stool of 9 h (interquartile range, 1-32 h). We found no food or environmental factors associated with a differential risk of infection with a specific pathogen. Travelers' diarrhea among a US military population in and around Incirlik, Turkey, can commonly be attributed to ETEC and Campylobacter spp. The high proportion of ST-only-producing CS6 ETEC in this region highlights the pathogen's worldwide diversity. Future studies of travelers' diarrhea in this population should adapt more novel microbiologic techniques such as polymerase chain reaction and enhanced culture methods to increase the likelihood of identifying pathogenic E. coli.

Antimicrobial resistance profiling and molecular subtyping of Campylobacter spp. from processed turkey

BACKGROUND

Campylobacter is a major cause of human disease worldwide and poultry are identified as a significant source of this pathogen. Most disease in humans is associated with the consumption of contaminated poultry or cross-contamination with other foods. The primary drugs of choice for treatment of human campylobacteriosis include erythromycin and ciprofloxacin. In this study, we investigated the prevalence of resistance to erythromycin and ciprofloxacin in Campylobacter isolates recovered from turkey carcasses at two processing plants in the Upper Midwest US. Further analysis of a subset of isolates was carried out to assess resistance and genotype profiles.

RESULTS

Campylobacter isolates from plant A (n = 439; including 196 C. coli and 217 C. jejuni) and plant B (n = 362, including 281 C. coli and 62 C. jejuni) were tested for susceptibility to ciprofloxacin and erythromycin using agar dilution. C. coli were more frequently resistant than C. jejuni in both plants, including resistance to ciprofloxacin (28% of C. jejuni and 63% of C. coli, plant B; and 11% of C. coli, plant A). Erythromycin resistance was low among C. jejuni (0% plant A and 0.3% plant B) compared to C. coli (41%, plant A and 17%, plant B). One hundred resistant and susceptible isolates were selected for additional antimicrobial susceptibility testing, restriction fragment length polymorphism analysis of the flaA gene (fla typing), and pulsed-field gel electrophoresis (PFGE). Fla-PFGE types obtained (n = 37) were associated with a specific plant with the exception of one type that was isolated from both plants. C. coli isolates (n = 65) were grouped into 20 types, while C. jejuni isolates (n = 35) were grouped into 17 types. Most isolates with identical fla-PFGE patterns shared identical or very similar antimicrobial resistance profiles. PFGE alone and composite analysis using fla-PFGE with resistance profiles separated C. jejuni and C. coli into distinct groups.

CONCLUSION

Ciprofloxacin and erythromycin resistance in Campylobacter recovered from processed turkey occurred more frequently among C. coli than C. jejuni. Fla-PFGE types were associated with a particular species, antimicrobial resistance profiles, and a specific plant. Molecular subtyping in this study provided more information about the relationships among antimicrobial-resistant Campylobacter at the processing level.

Trends of norfloxacin and erythromycin resistance of Campylobacter jejuni/Campylobacter coli isolates recovered from international travelers, 1994 to 2006

BACKGROUND

Campylobacter sp. is a major cause of bacterial enterocolitis and travelers' diarrhea. Empiric treatment regimens include fluoroquinolones and macrolides.

METHODS

Over the period 1994 to 2006, 724 Campylobacter jejuni/Campylobacter coli isolates recovered from international travelers at the outpatient clinic of the Institute of Tropical Medicine, Antwerp, Belgium, were reviewed for their susceptibility to norfloxacin and erythromycin.

RESULTS

Norfloxacin resistance increased significantly over time in isolates from travelers returning from Asia, Africa, and Latin America. For the years 2001 to 2006, norfloxacin resistance rates were 67 (70.5%) of 95 for Asia, 20 (60.6%) of 33 for Latin America, and 36 (30.6%) of 114 for Africa. The sharpest increase was noted for India, with no resistance in 1994, but 41 (78.8%) of 52 resistant isolates found during 2001 to 2006. Erythromycin resistance was demonstrated in 20 (2.7%) isolates, with a mean annual resistance of 3.1% +/- 2.8%; resistance increased over time, with up to 3(7.5%) of 40 and 3 (8.6%) of 35 resistant isolates in 2004 and 2006, respectively (p < 0.05); there was no apparent geographic association. Combined resistance to norfloxacin and erythromycin was observed in five isolates.

CONCLUSIONS

The high resistance rates to fluoroquinolones warrant reconsideration of their use as drugs of choice in patients with severe gastroenteritis when Campylobacter is the presumed cause. Continued monitoring of the incidence and the spread of resistant Campylobacter isolates is warranted.

Use of Antimicrobial Agents in Veterinary Medicine and Implications for Human Health

This review discusses why veterinary usage of antimicrobial agents is wrongly accused of causing a substantial part of the problem of resistant human pathogens. Without doubt, resistant organisms in animals are selected by veterinary antimicrobials. However, these are not a major human health risk either because the role of veterinary usage in selection or propagation is insignificant, or because resistant populations selected by veterinary usage do not pose a substantial risk to human health. Indeed, resistant bacterial infections in humans causing serious quantitative and qualitative health consequences are rarely food-borne and are not the same as those selected by veterinary usage of antimicrobial agents. The available evidence for veterinary selection of resistance, transmission to humans, and subsequent health consequences are reviewed for food-borne zoonotic pathogens. A risk assessment strategy is proposed to quantify potential hazards in order to decide on the most effective risk management strategy.

A stochastic assessment of the public health risks of the use of macrolide antibiotics in food animals

Campylobacteriosis is an important food-borne illness with more than a million U.S. cases annually. Antibiotic treatment is usually not required. However, erythromycin, a macrolide antibiotic, is recommended for the treatment of severe cases. Therefore, it is considered a critically important antibiotic and given special attention as to the risk that food animal use will lead to resistant infections and compromised human treatment. To assess this risk, we used a retrospective approach; estimating the number of campylobacteriosis cases caused by specific meat consumption utilizing the preventable fraction. We then determined the number of cases with macrolide resistance Campylobacter spp. based on a linear model relating the resistance fraction to on-farm macrolide use. In this article, we considered the uncertainties in the parameter estimates, utilized a more elaborate model of resistance development and separated C. coli and C. jejuni. There are no published data for the probability of compromised treatment outcome due to macrolide resistance. Therefore, our estimates of compromised treatment outcome were based on data for fluoroquinolone-resistant infections. The conservative results show the human health risks are extremely low. For example, the predicted risk of suboptimal human treatment of infection with C. coli from swine is only 1 in 82 million; with a 95% chance it could be as high as 1 in 49 million. Risks from C. jejuni in poultry or beef are even less. Reduced antibiotic use can adversely impact animal health. These low human risks should be weighed against the alternative risks.

Effect of antimicrobial dosage regimen on Salmonella and Escherichia coli isolates from feeder swine

A body of evidence exists that suggests that antimicrobial use in food animals leads to resistance in both pathogenic and commensal bacteria. This study focused on the impact of three different antimicrobial regimes (low-level continuous, pulse, and no antimicrobial) for two antimicrobials (chlortetracycline and tylosin) on the presence of Salmonella spp. and on the prevalence of antimicrobial resistance of both Salmonella spp. and nonspecific Escherichia coli in fecal samples from feeder swine. The prevalence of fecal samples positive for Salmonella spp. significantly decreased between the samples taken at feeder placement compared to samples taken when the animals were close to market weight. Differences in resistance of Salmonella spp. did not appear to be influenced by dosing treatment including the control. Analysis of antimicrobial resistance examining both susceptibility and resistance, as well as MIC outcomes, demonstrated that only resistance to cephalothin increased in E. coli under the pulse chlortetracycline treatment. These results suggest that the dosing regimes examined in this study did not lead to an increase in either the prevalence of Salmonella spp. or the prevalence of antimicrobial resistance in isolates of Salmonella spp. or E. coli.

The US National Antimicrobial Resistance Monitoring System

The use of antimicrobial agents in food animals can select for resistant bacterial pathogens that may be transmitted to humans via the commercial meat supply. In the USA, the FDA’s Center for Veterinary Medicine regulatory duties require a determination that antimicrobial drugs are safe and effective for use in food animals. In addition, a qualitative assessment of risks to human health from antimicrobial resistance requires development. This risk assessment process is supported by data generated by the FDA’s National Antimicrobial Resistance Monitoring System (NARMS) for enteric bacteria. NARMS data on antimicrobial susceptibility among Salmonella, Campylobacter, Escherichia coli and Enterococcus is collected. Research activities defining the genetic bases of resistance helps to understand the potential public health risks posed by the spread of antimicrobial resistance from food animal antimicrobial use. These activities help insure that antimicrobials are used judiciously to promote human and animal health.

Modeling the relationship between food animal health and human foodborne illness

To achieve further reductions in foodborne illness levels in humans, effective pre-harvest interventions are needed. The health status of food animals that are destined to enter the human food supply chain may be an important, although often overlooked, factor in predicting the risk of human foodborne infections. The health status of food animals can potentially influence foodborne pathogen levels in three ways. First, diseased animals may shed higher levels of foodborne pathogens. Second, animals that require further handling in the processing plant to remove affected parts may lead to increased microbial contamination and cross-contamination. Finally, certain animal illnesses may lead to a higher probability of mistakes in the processing plant, such as gastrointestinal ruptures, which would lead to increased microbial contamination and cross-contamination. Consequently, interventions that reduce the incidence of food animal illnesses might also help reduce bacterial contamination on meat, thereby reducing human illness. Some of these interventions, however, might also present a risk to human health. For example, the use of antibiotics in food animals can reduce rates of animal illness but can also select for antibiotic-resistant bacteria which can threaten human treatment options. In this study, we present a mathematical model to evaluate human health risks from foodborne pathogens associated with changes in animal illness. The model is designed so that potential human health risks and benefits from interventions such as the continued use of antibiotics in animal agriculture can be evaluated simultaneously. We applied the model to a hypothetical example of Campylobacter from chicken. In general, the model suggests that very minor perturbations in microbial loads on meat products could have relatively large impacts on human health, and consequently, small improvements in food animal health might result in significant reductions in human illness.

FoodNet: overview of a decade of achievement

The Foodborne Diseases Active Surveillance Network (FoodNet) performs active, population-based laboratory surveillance for nine common foodborne pathogens and one syndrome in a catchment area of 44.5 million persons. FoodNet surveillance data are an important resource for examining trends in specific diseases over time. Population surveys and laboratory surveys have been used to estimate the burden of disease, for example that there are 38.6 cases of Salmonella infection for each reported case. FoodNet case-control studies have identified new risk factors for E. coli O157, Campylobacter, and several Salmonella serotypes. FoodNet sites have demonstrated the value of delivered stool kits for improving the rate of confirming an etiology in foodborne disease outbreaks. FoodNet helps build capacity for foodborne disease surveillance in participating sites and through close collaborations with PulseNet, EHS-Net, Global SalmSurv, and other partners.

Re-analysis of the risks attributed to ciprofloxacin-resistant Campylobacter jejuni infections

Recent publications were compared and analysed in addition to novel surveillance data to assess the hypothesis that fluoroquinolone-resistant Campylobacter infections are causing more severe disease than susceptible infections. The available data did not support this hypothesis. There was no significant difference in duration of disease between susceptible and resistant infections. However, both for resistant and susceptible infections, disease symptoms were prolonged by on average 1-2 days for Campylobacter cases acquired during foreign travel. Nevertheless, the likelihood and duration of hospitalisation were not increased for cases related to foreign travel. These observations were confirmed by a new analysis of almost 11,000 cases. We conclude that fluoroquinolone-resistant Campylobacter infections are not more severe than susceptible infections.

Comparison of antimicrobial resistance of Campylobacter jejuni isolated from humans, chickens, raw milk, and environmental water in Québec

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.

Fluoroquinolone-resistant Campylobacter species and the withdrawal of fluoroquinolones from use in poultry: a public health success story

Campylobacter species cause 1.4 million infections each year in the United States. Fluoroquinolones (e.g., ciprofloxacin) are commonly used in adults with Campylobacter infection and other infections. Fluoroquinolones (e.g., enrofloxacin) are also used in veterinary medicine. Human infections with fluoroquinolone-resistant Campylobacter species have become increasingly common and are associated with consumption of poultry. These findings, along with other data, prompted the US Food and Drug Administration to propose the withdrawal of fluoroquinolone use in poultry in 2000. A lengthy legal hearing concluded with an order to withdraw enrofloxacin from use in poultry (effective in September 2005). Clinicians are likely to continue to encounter patients with fluoroquinolone-resistant Campylobacter infection and other enteric infection because of the continued circulation of fluoroquinolone-resistant Campylobacter species in poultry flocks and in persons returning from foreign travel who have acquired a fluoroquinolone-resistant enteric infection while abroad. Judicious use of fluoroquinolones and other antimicrobial agents in human and veterinary medicine is essential to preserve the efficacy of these important chemotherapeutic agents.

Activities, achievements, and lessons learned during the first 10 years of the Foodborne Diseases Active Surveillance Network: 1996-2005

Since the establishment of the Foodborne Diseases Active Surveillance Network (FoodNet) in 1996, it has been an essential resource for the surveillance and investigation of foodborne disease in the United States. FoodNet has had a major impact on food safety because it conducts population-based, active surveillance for laboratory-confirmed infections from 9 pathogens commonly transmitted through food. Each year, FoodNet publishes the National Report Card on Food Safety, which is used by regulatory agencies, industry and consumer groups, and public health personnel to prioritize and evaluate food safety interventions and monitor progress toward national health objectives. FoodNet also determines the human-health impact of foodborne illness by conducting related epidemiological studies that contribute to the estimates of the overall burden of foodborne illness, attribute the burden of foodborne illness to specific foods and settings, and address important foodborne disease-related issues, such as antimicrobial resistance and sequelae from foodborne infections. This article summarizes the activities, achievements, and lessons learned during the first 10 years of FoodNet.

High level of ciprofloxacin resistance and its molecular background among Campylobacter jejuni strains isolated in the United Arab Emirates

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.

Increase in nalidixic acid resistance among non-Typhi Salmonella enterica isolates in the United States from 1996 to 2003

Fluoroquinolones commonly are used to treat adult Salmonella infections. Fluoroquinolone treatment has failed for persons infected with nalidixic acid-resistant Salmonella. From 1996 to 2003, state public health laboratories forwarded 12,252 non-Typhi Salmonella enterica isolates to the Centers for Disease Control and Prevention for antimicrobial susceptibility testing; 203 (1.6%) of the isolates were nalidixic acid resistant, and 14 (7%) of those were ciprofloxacin resistant. Resistance to nalidixic acid significantly increased from 0.4% in 1996 to 2.3% in 2003. All ciprofloxacin-resistant isolates had at least one point mutation in the quinolone resistance determining region (QRDR) of gyrA and did not harbor qnr or have point mutations in the QRDR of gyrB, parC, or parE. Continued surveillance of antimicrobial resistance among non-Typhi S. enterica isolates is needed to mitigate the increasing prevalence of nalidixic acid resistance.

Current and future developments in travelers' diarrhea therapy

Diarrhea continues to be the leading health problem among international travelers to developing tropical and semi-tropical regions. Despite more than 50 years of research providing information about the etiology and pathogenesis of the disease, the rate of illness and consequences remain unchanged. An estimated 40% of travelers to developing nations will become ill with diarrhea. Although travelers' diarrhea is considered a self-limited disease, novel and effective approaches to disease prevention and treatment have been realized in recent years. Also, recent evidence has identified a potential for long-term complications of the illness, including postinfectious irritable bowel syndrome. With the advent of poorly absorbed (<0.4%) rifaximin, a treatment option for the common watery diarrhea syndrome equivalent to previously used absorbed antibacterial drugs has emerged. Rifaximin with an excellent safety profile and limited potential to induce coliform resistance, prevents most of the diarrhea that would otherwise occur. With further studies in different settings, new consideration should be given to the routine use of chemoprophylaxis for travelers to high-risk countries. Antibacterial drugs will continue to be the optimal treatment for travelers' diarrhea subjects for the most part caused by bacterial enteropathogens and shorten the duration of diarrhea by 1-2 days compared with no active drug treatment.

Potential Impacts of Antibiotic Use in Poultry Production

The ways in which antibiotics are used in poultry production have changed considerably during the past decade, mainly because of concerns about potential negative human health consequences caused by these uses. Human health improvements directly attributable to these antibiotic-use changes are difficult to demonstrate. Given that some antibiotics will continue to be used in the poultry industry, methods are needed for estimating the causal relationship between these antibiotic uses and actual animal and human health impacts. This is a challenging task because of the numerous factors that are able to select for the emergence, dissemination, and persistence of antibiotic resistance. Managing the potential impacts of antibiotic use in poultry requires more than a simple estimation of the risks that can be attributed to the use of antibiotics in poultry. Risk models and empirical studies that evaluate interventions that are capable of minimizing the negative consequences associated with specific antibiotic uses are desperately needed.

New insights and directions in travelers' diarrhea

Since first studied more than 5 decades ago the risk of travelers'diarrhea for persons going from industrialized regions to developing countries has remained high. Most cases of illness are caused by bacterial agents. Travelers' diarrhea is associated with temporary disability and it may progress to chronic intestinal illness and postinfectious irritable bowel syndrome. Exercising care about food and beverage intake, the use of rifaximin prophylaxis for selective patients, and self-treatment of all resultant illness will continue to be the way in which the disease is prevented or managed best by travelers. Future approaches will be aimed at making host regions safer and providing more effective methods of treatment and prevention of enteric disease during short-term international travel.

Low-Level Fluoroquinolone Resistance among Campylobacter jejuni Isolates in Australia

BACKGROUND

Ciprofloxacin-resistant Campylobacter jejuni isolates obtained from infected patients in Australia have not been detected in studies of isolates from specific geographic areas. The Australian government has prohibited the use of fluoroquinolone in food-producing animals. To assess the impact of this policy, we have examined the antimicrobial susceptibility of isolates from 5 Australian states.

METHODS

We conducted a period-prevalence survey of the susceptibility of C. jejuni isolates to 10 antimicrobial agents. C. jejuni isolates obtained from 585 patients from 5 Australian states (Queensland, South Australia, Tasmania, Victoria, and Western Australia) were identified by means of notifiable disease databases and were systematically selected from September 2001 to August 2002.

RESULTS

Among locally acquired infections, only 2% of isolates (range, 0%-8% in different states) were resistant to ciprofloxacin. The locally acquired isolates also exhibited resistance to sulfisoxazole (55%), ampicillin (46%), roxithromycin (38%), tetracycline (7%), nalidixic acid (6%), chloramphenicol (3%), erythromycin (3%), gentamicin (2%), and kanamycin (0.2%). Treatment with antimicrobial agents in the 4 weeks before onset was not associated with ciprofloxacin resistance.

CONCLUSIONS

The very low level of ciprofloxacin resistance in C. jejuni isolates likely reflects the success of Australia's policy of restricting use of fluoroquinolones in food-producing animals.

Emerging microbiological food safety issues related to meat

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.

Antibiotic resistance of retail food and human Campylobacter isolates on the island of Ireland from 2001-2002

The antimicrobial resistance profiles of Campylobacter isolates recovered from a range of retail food samples (n=374) and humans (n=314) to eight antimicrobial compounds were investigated. High levels of resistance in food C. jejuni isolates were observed for ceftiofur (58%), ampicillin (25%) and nalidixic acid (17%) with lower levels observed for streptomycin (7.9%) and chloramphenicol (8.3%). A total of 80% of human C. jejuni isolates were resistant to ceftiofur, while 17% showed resistance to ampicillin and nalidixic acid, 8.6% to streptomycin and 4.1% to chloramphenicol. Resistance to clinically relevant antimicrobials such as erythromycin, ciprofloxacin and tetracycline was 6.7, 12, and 15% respectively for all food isolates and was similar to corresponding resistance prevalences observed for human isolates, where 6.4, 12 and 13% respectively were found to be resistant. Comparisons of C. jejuni isolates in each location showed a high degree of similarity although some regional variations did exist. Comparison of total C. jejuni and C. coli populations showed minor differences, with C. jejuni isolates more resistant to ampicillin and ceftiofur. Multidrug resistance patterns showed some profiles common to human and clinical isolates.

The epidemiology of antibiotic resistance in Campylobacter

Antibiotic resistance, particularly with the fluoroquinolones and macrolide antibiotics, has now emerged globally with thermophilic campylobacters, including Campylobacter jejuni and C. coli, giving rise to concerns about how these organisms have acquired such resistance characteristics, as well as consequences for human and animal treatment. This review examines (i) the clinical epidemiology of antibiotic resistance in human and animal thermophilic campylobacters, (ii) an update on resistance rates globally, (iii) surveillance of antimicrobial resistance in campylobacters originating from animals, particularly poultry, (iv) the role of the environment in the acquisition and transmission of antibiotic-resistant campylobacters, as well as (v) issues of biocide resistance in campylobacters.

Rapid benefit-risk assessments: no escape from expert judgments in risk management

The "human health impacts assessment" described by Cox and Popken (this issue) is intended to be a benefit-risk tool that avoids pitfalls of using expert judgments for policy analysis or during strict application of the precautionary principle in risk management. The proposed benefit-risk calculation uses numerous assumptions and suppositions to calculate a ratio of quality-adjusted life years (QALYs) lost for the number of human illness days prevented by the use of a food-animal antimicrobial drug, to the number of human illness days caused by the use of the antimicrobial drug. Assumptions about data--e.g., expert judgments on the representativeness of parameter estimates--are commonly used in risk assessment and risk management, including Cox and Popken's method. Cox and Popken apply the technique to specific examples of enrofloxacin and macrolides antimicrobial drugs, sometimes used in broiler chickens for human food. Although enthusiastically portrayed as a straightforward calculation of QALYs lost for two decision alternatives, Cox and Popken were silent on the pivotal expert judgment subsumed in their method: quality weights for illnesses caused by antimicrobial-resistant and antimicrobial-sensitive microbes are tacitly assumed to be equal. Yet, the costs in terms of prolonged illness, additional medications, repeat medical visits, and dread of more serious sequelae are expected to differ substantially for antimicrobial-resistant versus antimicrobial-sensitive illnesses. Despite their enthusiasm to the contrary, the "human health impacts assessment" by Cox and Popken is not immune from expert judgments in risk management.

Antimicrobial Use and Outcomes in Patients with Multidrug-Resistant and Pansusceptible Salmonella Newport Infections, 2002–2003

Multidrug-resistant Salmonella Newport with decreased susceptibility to ceftriaxone (MDR-AmpC) is becoming increasingly common in its food animal reservoirs and in humans. Few data exist on rates of antimicrobial use or differences in clinical outcomes in persons infected with MDR-AmpC or other Salmonella strains. We conducted a case-comparison analysis of data from a multistate population-based case-control study to identify antimicrobial treatment choices and differences in clinical outcomes in those infected with MDRAmpC compared to pansusceptible S. Newport. Of isolates from 215 laboratory-confirmed S. Newport cases, 54 (25%) were MDR-AmpC, 146 (68%) were pansusceptible, and 15 (7%) had other resistance patterns; 146 (68%) patients with S. Newport were treated with antimicrobial agents and 66 (33%) were hospitalized. Over two-thirds of cases at low-risk for serious complications received antimicrobial therapy, most commonly with fluoroquinolones, to which this strain was susceptible. There were no significant differences in symptoms, hospitalization, duration of illness, or other outcomes between the persons infected with MDR-AmpC and pansusceptible S. Newport. Although currently prevalent MDR-AmpC S. Newport strains remains susceptible to the antimicrobial most commonly prescribed for it, continued efforts to reduce unnecessary use of antimicrobial agents in food animals and humans are critical to prevent further development of resistance to quinolones and cephalosporins, which is likely to lead to substantial adverse outcomes.

Poorly Absorbed Antibiotics for the Treatment of Traveler' Diarrhea

This article describes the use of poorly absorbed antibiotics for the treatment of traveler's diarrhea. Poorly absorbed oral antibiotics can deliver high concentrations of drug to the site of enteric infection with minimal risk of systemic adverse effects, toxicity, and drug interactions. Compared with systemically absorbed oral antibiotics, poorly absorbed oral antibiotics may be less associated with the pressure that leads to the development of bacterial resistance, because they do not affect bacteria outside the gastrointestinal tract. In clinical studies, poorly absorbed oral antibiotics, including aztreonam, bicozamycin, and rifaximin, were more effective than and as well tolerated as placebo; in particular, rifaximin was as effective as oral ciprofloxacin in reducing the duration of illness in traveler's diarrhea. More research is warranted to delineate the effects of poorly absorbed antibiotics in invasive infection and to assess the potential for the development of bacterial resistance.

Human health consequences of antimicrobial drug-resistant Salmonella and other foodborne pathogens

There are several clinical and public health consequences associated with antimicrobial drug resistance in non-Typhi Salmonella species and other foodborne pathogens. If bacteria acquire resistance to clinically important antimicrobial drugs, early empirical treatment may fail, and there will be limitations in the choices of treatment after the establishment of microbial diagnosis. Drug-resistant gastrointestinal pathogens preferentially cause illness in persons receiving antimicrobial drugs for any medical condition. Consequently, emerging resistance in foodborne pathogens may result in increased burdens of illness and outbreaks in settings where patients are treated with antimicrobial drugs. Finally, resistance may be associated with increased virulence, and several epidemiological studies have demonstrated that infections with drug-resistant non-Typhi Salmonella serotypes and Campylobacter species are associated with excess mortality and morbidity. Mitigation of drug resistance in foodborne bacteria is likely to be of benefit for human health.

What's new in enteric infectious diseases at home and abroad

PURPOSE OF REVIEW

This review was designed to focus on the important research in the area of acute infectious diarrhea published within the past year. PubMed was reviewed for articles published in 2004 and 2005 relating to pathogen-specific diarrhea and for travelers' diarrhea to identify the newly published articles.

RECENT FINDINGS

New studies continue to show the importance of the diarrheagenic Escherichia coli as causes of acute and persistent diarrhea. Enteroaggregative E. coli has recently been shown to be an unrecognized cause of community-acquired diarrhea in infants in the USA. Genetic factors explain an increased susceptibility to travelers' diarrhea among international travelers. Also, poorly non-absorbed rifaximin (< 0.4%) was shown to be an effective drug when used prophylactically to prevent bacterial diarrhea during high risk travel.

SUMMARY

Studies will continue to define the etiology of diarrhea and to better understand the epidemiology and prevention of infectious diarrhea. Antibacterial resistance among enteric bacterial pathogens is a growing problem, leading to the search for newer antibacterial drugs. Diarrhea due to bacterial agents in international travelers can be prevented and treated successfully by antibacterial drugs. The nonabsorbed rifamycin drug, rifaximin, appears to be ideally suited to become the important new drug in prevention and treatment of travelers' diarrhea. Studies are underway to determine the value of the drug in preventing invasive forms of diarrhea during travel to Asia and in the prevention of the commonly occurring post-infectious irritable bowel syndrome.

Evidence of an Association Between Use of Anti-microbial Agents in Food Animals and Anti-microbial Resistance Among Bacteria Isolated from Humans and the Human Health Consequences of Such Resistance

Several lines of evidence indicate that the use of anti-microbial agents in food animals is associated with anti-microbial resistance among bacteria isolated from humans. The use of anti-microbial agents in food animals is most clearly associated with anti-microbial resistance among Salmonella and Campylobacter isolated from humans, but also appears likely among enterococci, Escherichia coli and other bacteria. Evidence is also accumulating that the anti-microbial resistance among bacteria isolated from humans could be the result of using anti-microbial agents in food animals and is leading to human health consequences. These human health consequences include: (i) infections that would not have otherwise occurred and (ii) increased frequency of treatment failures and increased severity of infection. Increased severity of infection includes longer duration of illness, increased frequency of bloodstream infections, increased hospitalization and increased mortality. Continued work and research efforts will provide more evidence to explain the connection between the use of anti-microbial agents in food animals and anti-microbial-resistant infections in humans. One particular focus, which would solidify this connection, is to understand the factors that dictate spread of resistance determinants, especially resistant genes. With continued efforts on the part of the medical, veterinary and public health community, such research may contribute to more precise guidelines on the use of anti-microbials in food animals.