Campylobacter and fluoroquinolones: a bias data set?

Campylobacter jejuni Isolation/Enumeration from Environmental Samples

Currently, there is no universally accepted standard media or method for the recovery of Campylobacter species. This is likely due to the ubiquity of the organism in nature, the complex sample matrices from which the organism is often recovered, as well as the fragile/viable-but nonculturable state the organism assumes in response to stress. The use of a sterile filter placed upon a nonselective Brucella Agar Blood Plate (BAB), followed by incubation at 37 °C in a hydrogen-containing atmosphere (Campycheck), is one method to recover stressed and emerging Campylobacter spp. from complex environmental matrices; however, this technique does not currently allow for the enumeration of the recovered organisms. Enumeration is performed using serial dilutions of sample homogenate plated onto modified Campy-Cefex media followed by incubation at either 37 °C or 42 °C in a microaerobic atmosphere.

Application of high-throughput sequencing to measure the performance of commonly used selective cultivation methods for the foodborne pathogen Campylobacter

Campylobacter is an important foodborne human pathogen, which has traditionally been studied using a variety of selective cultivation methods. Here we use next-generation sequencing to ask the following: (i) how selective are commonly used Campylobacter cultivation methods relative to the initial sample and (ii) how do the specificity and sensitivity of these methods compare with one another? To answer these questions, we used 16S rRNA tagged-pyrosequencing to sequence directly from a pooled fecal sample representing a c. 16,000 bird poultry flock and compared these data to exhaustive sequencing of colonies formed after plating. We compared five commonly used media [Cefex, Cape Town, modified cefoperazone charcoal deoxycholate agar (mCCDA), Campy-Line agar (CLA), and Campy-CVA agar (CVA)], two incubation atmospheres (10% CO(2), 5% O(2), 85% N(2) and 10% CO(2), 10% H(2), 80% N(2)), and two incubation temperatures (37 and 42 °C). Analysis of 404,104 total sequence reads, including 19 472 total fecal reads, revealed Campylobacter represented only a small proportion (< 0.04%) of sequences present in the feces, but 88-97% of sequences from each media type. Incubation atmosphere had little effect on recovery, but a significant difference in media specificity (more non-Campylobacter OTUs; P = 0.028) was found at 42 vs. 37 °C. The most common non-Campylobacter sequence type was Proteus, which ranged from 0.04% of sequences (mCCDA) to 10.8% (Cape Town). High-throughput sequencing provides a novel and powerful approach to measure the performance of selective media, which remain widely used for research and regulatory purposes.

Comparison of three selective media and validation of the VIDAS Campylobacter assay for the detection of Campylobacter jejuni in ground beef and fresh-cut vegetables

In this study, three different selective media, modified cefoperazone charcoal deoxycholate agar (mCCDA), Karmali agar, and Preston agar, were compared for isolating Campylobacter jejuni from artificially contaminated ground beef and fresh-cut vegetables that have different levels of background microflora. Concurrently, an automated enzyme-linked immunosorbent assay method for detecting Campylobacter spp. (VIDAS Campylobacter) was evaluated by comparing it with the culture methods. Food samples inoculated with C. jejuni were enriched in Bolton broth at 42°C for 44 h and then streaked onto the three different selective media, followed by incubation under microaerobic conditions at 42°C for 48 h. The enriched Bolton broth (1 ml) was used in the VIDAS Campylobacter assay. No statistical differences in sensitivities were observed between the three selective media for ground beef and fresh-cut vegetables, but the selectivity of Preston agar was better (P < 0.05) than those of mCCDA and Karmali agar. The VIDAS Campylobacter assay showed a recovery rate similar (P > 0.05) to those of all of the medium combinations in ground beef. However, more positive samples (P < 0.05) were detected with the VIDAS Campylobacter than with the selective agars, except for the combinations of mCCDA plus Preston agar or mCCDA plus Karmali agar plus Preston agar in fresh-cut vegetables.

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.

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.

Traveler's diarrhea in Thailand: randomized, double-blind trial comparing single-dose and 3-day azithromycin-based regimens with a 3-day levofloxacin regimen

BACKGROUND

Traveler's diarrhea in Thailand is frequently caused by Campylobacter jejuni. Rates of fluoroquinolone (FQ) resistance in Campylobacter organisms have exceeded 85% in recent years, and reduced fluoroquinolone efficacy has been observed.

METHODS

Azithromycin regimens were evaluated in a randomized, double-blind trial of azithromycin, given as a single 1-g dose or a 3-day regimen (500 mg daily), versus a 3-day regimen of levofloxacin (500 mg daily) in military field clinics in Thailand. Outcomes included clinical end points (time to the last unformed stool [TLUS] and cure rates) and microbiological end points (pathogen eradication).

RESULTS

A total of 156 patients with acute diarrhea were enrolled in the trial. Campylobacter organisms predominated (in 64% of patients), with levofloxacin resistance noted in 50% of Campylobacter organisms and with no azithromycin resistance noted. The cure rate at 72 h after treatment initiation was highest (96%) with single-dose azithromycin, compared with the cure rates of 85% noted with 3-day azithromycin and 71% noted with levofloxacin (P=.002). Single-dose azithromycin was also associated with the shortest median TLUS (35 h; P=.03, by log-rank test). Levofloxacin's efficacy was inferior to azithromycin's efficacy, except in patients with no pathogen identified during the first 24 h of treatment or in patients with levofloxacin-susceptible Campylobacter isolates, in whom it appeared to be equal to azithromycin. The rate of microbiological eradication was significantly better with azithromycin-based regimens (96%-100%), compared with levofloxacin (38%) (P=.001); however, this finding was poorly correlated with clinical outcome. A higher rate of posttreatment nausea in the 30 min after receipt of the first dose (14% vs. <6%; P=.06) was observed as a mild, self-limited complaint associated with single-dose azithromycin.

CONCLUSIONS

Single-dose azithromycin is recommended for empirical therapy of traveler's diarrhea acquired in Thailand and is a reasonable first-line option for empirical management in general.

Dissemination of fluoroquinolone-resistant Campylobacter spp. within an integrated commercial poultry production system

While characterizing the intestinal bacterial community of broiler chickens, we detected epsilon-proteobacterial DNA in the ilea of 3-day-old commercial broiler chicks (J. Lu, U. Idris, B. Harmon, C. Hofacre, J. J. Maurer, and M. D. Lee, Appl. Environ. Microbiol. 69:6816-6824, 2003). The sequences exhibited high levels of similarity to Campylobacter jejuni and Campylobacter coli sequences, suggesting that chickens can carry Campylobacter at a very young age. Campylobacter sp. was detected by PCR in all samples collected from the ilea of chicks that were 3 to 49 days old; however, it was detected only in the cecal contents of chickens that were at least 21 days old. In order to determine whether the presence of Campylobacter DNA in young chicks was due to ingestion of the bacteria in food or water, we obtained commercial broiler hatching eggs, which were incubated in a research facility until the chicks hatched. DNA sequencing of the amplicons resulting from Campylobacter-specific 16S PCR performed with the ileal, cecal, and yolk contents of the day-of-hatching chicks revealed that Campylobacter DNA was present before the chicks consumed food or water. The 16S rRNA sequences exhibited 99% similarity to C. jejuni and C. coli sequences and 95 to 98% similarity to sequences of other thermophilic Campylobacter species, such as C. lari and C. upsaliensis. The presence of C. coli DNA was detected by specific PCR in the samples from chicks obtained from a commercial hatchery; however, no Campylobacter was detected by culturing. In order to determine whether the same strains of bacteria were present in multiple levels of the integrator, we cultured Campylobacter sp. from a flock of broiler breeders and their 6-week-old progeny that resided on a commercial broiler farm. The broiler breeders had been given fluoroquinolone antibiotics, and we sought to determine whether the same fluoroquinolone-resistant strain was present in their progeny. The isolates were typed by pulsed-field gel electrophoresis, which confirmed that the parental and progeny flocks contained the same strain of fluoroquinolone-resistant C. coli. These data indicate that resistant C. coli can be present in multiple levels of an integrated poultry system and demonstrated that molecular techniques or more sensitive culture methods may be necessary to detect early colonization by Campylobacter in broiler chicks.

Campylobacter susceptibility to ciprofloxacin and corresponding fluoroquinolone concentrations within the gastrointestinal tracts of chickens

AIMS

This study evaluated the relationship between Campylobacter susceptibility and enteric fluoroquinolone concentrations in chickens treated with different doses of enrofloxacin.

METHODS AND RESULTS

All chickens were challenged with seven fluoroquinolone sensitive Campylobacter jejuni (6.6 x 10(6) CFU per bird) at 2 weeks posthatch. At 26 days of age chickens were treated with 0 (n = 29 birds), 25 mg ml(-1) enrofloxacin (Baytril, Bayer Corp., Shawnee Mission, KS, USA) for 3 days (n = 45 birds) or 50 mg ml(-1) enrofloxacin for 7 days (n = 65 birds) in the drinking water. The crop, upper ileum, lower ileum, ceca and colon contents were collected from both enrofloxacin treatment groups (n = 5 birds per day per treatment group) and nonmedicated controls. The minimum inhibitory concentration (MIC) of ciprofloxacin for Campylobacter increased for isolates from both treatment groups within the first day of dosing and the daily average ranged from 1.4 to 6.5 microg ml(-1) throughout the study. Although enteric fluoroquinolone concentrations were higher (P < 0.05) in birds dosed with 50 mg ml(-1)vs 25 mg ml(-1) enrofloxacin, there were no differences between the isolates collected from these groups for MIC values.

CONCLUSION

These data indicate, for the doses used, differences in gut fluoroquinolone concentrations do not produce isolates of Campylobacter with differing susceptibility to ciprofloxacin.

SIGNIFICANCE AND IMPACT OF THE STUDY

Using the manufacturers lowest, shortest duration dose vs the highest, longest duration dose of enrofloxacin did not change Campylobacter susceptibility to ciprofloxacin. However, ciprofloxacin MIC values for Campylobacter determined in this study were lower than previously reported.

Antimicrobial resistance in Campylobacter jejuni and Campylobacter coli strains isolated in 1991 and 2001-2002 from poultry and humans in Berlin, Germany

The susceptibilities of 430 Campylobacter jejuni strains and 79 C. coli strains to six antimicrobial agents were tested and analyzed. The two sets of strains originated from retail market chicken and turkey samples and from humans, respectively, in Berlin, Germany. Two groups of isolates, one dating from 1991 and the other dating from 2001-2002, were tested. Of the Campylobacter sp. isolates recovered from humans in 2001-2002, 45.1% were resistant to ciprofloxacin, 37.8% were resistant to tetracycline, 12.8% were resistant to ampicillin, and 50.0% were resistant to trimethoprim-sulfamethoxazole. All isolates were susceptible to gentamicin, while the overall rate of resistance to erythromycin was 6.1%. During the 10 years between the two sampling times, the rates of resistance to ciprofloxacin (P<0.001), ampicillin (P=0.035), and tetracycline (P=0.01) increased significantly among strains isolated from humans. Furthermore, among human C. coli strains the rate of resistance to erythromycin rose from 7.1% in 1991 to 29.4% in 2001-2002. In comparison, Campylobacter sp. isolates from poultry already had high rates of resistance in 1991. Different rates of resistance to tetracycline among isolates from chickens and turkeys suggested the development of resistance during antimicrobial treatment in food animals. Thus, discrepancies in the antimicrobial resistance rates among Campylobacter isolates originating from poultry and humans support the hypothesis that at least some of the resistant Campylobacter strains causing infection in humans come from sources other than poultry products.