Analysis of topoisomerase mutations in fluoroquinolone-resistant and -susceptible Campylobacter jejuni strains isolated in Senegal

In this study, topoisomerase mutations in ciprofloxacin-resistant and -susceptible Campylobacter jejuni were analysed by DNA sequencing. In certain ciprofloxacin-resistant C. jejuni, the mechanism of resistance was complex. The Thr86-Ala substitution in the GyrA protein appears to play a role in increasing the minimum inhibitory concentration of nalidixic acid only. In addition, isolates with this amino acid change and those resistant to quinolones but lacking a mutation in the GyrA quinolone resistance-determining region could be derived from two different clones. Based on gyrA and gyrB polymorphisms, C. jejuni isolates from the Dakar region of Senegal appeared to be less diverse than those from other countries. Moreover, C. jejuni isolates in Senegal appeared to differ from European isolates by lack of a silent mutation at codon 120 of the gyrA gene.

Trends in antimicrobial resistance in Campylobacter spp. causing traveler's diarrhea

The aim of this study was to analyze the evolution of the levels of resistance to nine antimicrobial agents in clinical isolates of Campylobacter spp. causing traveler's diarrhea during the period from 1993 to 2003. The antimicrobial resistance levels to ampicillin, amoxicillin plus clavulanic acid, chloramphenicol, tetracycline, erythromycin, gentamicin, clindamicin, nalidixic acid and ciprofloxacin were established by the method of Kirby-Bauer. Two subperiods (1993-1998 and 1999-2003) were chosen to compare the evolution of the levels of antimicrobial resistance. Mantel-Haenszel or Fisher's exact test was performed to determine statistical significance. High levels of resistance to four out of nine antimicrobial agents tested were detected: ampicillin (66.3%), nalidixic acid (52.2%), ciprofloxacin (46.7%), and tetracycline (42.4%). In addition, resistance levels of 20.6% to amoxicillin plus clavulanic acid were detected. An increase in the resistance levels between the two subperiods analyzed for those five antimicrobial agents was observed. This increase was statistically significant for ampicillin, nalidixic acid, and ciprofloxacin. Two cases of therapeutic failure during treatment with ciprofloxacin were detected. The level of resistance to the most commonly used antibacterial agents in the developing world is increasing in Campylobacter spp., the increase in the resistance to quinolones being of special concern.

Zoonotic bacterial populations, gut fermentation characteristics and methane production in feedlot steers during oral nitroethane treatment and after the feeding of an experimental chlorate product

Nitroethane inhibits the growth of certain zoonotic pathogens such as Campylobacter and Salmonella spp., foodborne pathogens estimated to cause millions of human infections each year, and enhances the Salmonella- and Escherichia coli-killing effect of an experimental chlorate product being developed as a feed additive to kill these bacteria immediately pre-harvest. Limited studies have shown that nitroethane inhibits ruminal methane production, which represents a loss of 2-12% of the host's gross energy intake and contributes to global warming and destruction of the ozone layer. The present study was conducted to assess the effects of 14-day oral nitroethane administration, 0 (0X), 80 (1X) or 160 (2X)mg nitroethane/kg body weight per day on ruminal and fecal E. coli and Campylobacter, ruminal and fecal methane-producing and nitroethane-reducing activity, whole animal methane emissions, and ruminal and fecal fermentation balance in Holstein steers (n=6 per treatment) averaging 403+/-26 (SD) kg BW. An experimental chlorate product was fed the day following the last nitroethane administration to determine effects on E. coli and Campylobacter. The experimental chlorate product decreased (P<0.001) fecal, but not ruminal (P>0.05) E. coli concentrations by 1000- and 10-fold by 24 and 48 h, respectively, after chlorate feeding when compared to pre-treatment concentrations (>5.7 log(10) colony forming units/g). No effects (P>0.05) of nitroethane or the experimental chlorate product were observed on fecal Campylobacter concentrations; Campylobacter were not recovered from ruminal contents. Nitroethane treatment decreased (P<0.01) ruminal (8.46, 7.91 and 4.74+/-0.78 micromol/g/h) and fecal (3.90, 1.36 and 1.38+/-0.50 micromol/g/h) methane-producing activity for treatments 0X, 1X and 2X, respectively. Administration of nitroethane increased (P<0.001) nitroethane-reducing activity in ruminal, but not fecal samples. Day of study affected ruminal (P<0.0001) but not fecal (P>0.05) methane-producing and nitroethane-reducing activities (P<0.01); treatment by day interactions were not observed (P>0.05). Ruminal accumulations of acetate decreased (P<0.05) in 2X-treated steers when compared with 0X- and 1X-treated steers, but no effect (P>0.05) of nitroethane was observed on propionate, butyrate or the acetate to propionate ratio. Whole animal methane emissions, expressed as L/day or as a proportion of gross energy intake (%GEI), were unaffected by nitroethane treatment (P>0.05), and were not correlated (P>0.05) with ruminal methane-producing activity. These results demonstrate that oral nitroethane administration reduces ruminal methane-producing activity but suggest that a microbial adaptation, likely due to an in situ enrichment of ruminal nitroethane-reducing bacteria, may cause depletion of nitroethane, at least at the 1X administration dose, to concentrations too low to be effective. Further research is warranted to determine if the optimization of dosage of nitroethane or related nitrocompouds can maintain the enteropathogen control and anti-methanogen effect in fed steers.

Dissemination of antimicrobial resistant strains of Campylobacter coli and Campylobacter jejuni among cattle in Washington State and California

The purpose of this study was to investigate the genetic similarity of Campylobacter jejuni and Campylobacter coli with similar antimicrobial resistance phenotypes, isolated from cattle on different farms and at different times, in order to evaluate the possible existence of disseminated antimicrobial resistant clones. PFGE after SmaI and KpnI restriction identified 23 and 16 distinct PFGE patterns among 29 C. jejuni and 66 C. coli isolates, respectively. In C. coli, 51 (77%) of the resistant isolates demonstrated one of the four indistinguishable PFGE patterns, whereas only 24% doxycycline resistant C. jejuni shared one of the two indistinguishable PFGE patterns. The genetic mechanisms of resistance were homogeneous within and between these clonal types. Genetically indistinguishable (clonal) groups of C. coli accounted for most Campylobacter sp. with multiple antimicrobial resistance observed in this study, consistent with a role for clonal dissemination in the epidemiology of resistance in this species.

A meta-analysis on the effects of antibiotic treatment on duration of symptoms caused by infection with Campylobacter species

Eleven randomized, controlled trials of antibiotic treatment versus placebo in patients with Campylobacter species infection were pooled in a meta-analysis. Antibiotic treatment shortened the duration of intestinal symptoms by 1.32 days (95% confidence interval, 0.64-1.99; P<.0001). Because of problems with drug resistance, a restrictive attitude towards the administration of antibiotics in uncomplicated cases is advised.

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.

Campylobacter fetus bacteraemia in a healthy individual: clinical and therapeutical implications

Campylobacter species are well-recognized common causes of gastrointestinal infections. While Campylobacter jejuni is probably the most common Campylobacter isolated in humans, Campylobacter fetus is rather infrequent and mostly related with bacteraemia. Even on such occasions, it seems that immunocompetent individuals are spared. We report a case of C. fetus bacteraemia in a healthy-except for impaired fasting glucose (IFG) levels-farmer, presenting as an acute febrile syndrome and treated successfully as brucellosis.

Antibiotic-resistant Campylobacter: could efflux pump inhibitors control infection?

Campylobacter is the most common cause of bacterial gastroenteritis in the world. Poultry is the main reservoir of human infections. The widespread use of antibiotics in agriculture and veterinary medicine has resulted in the emergence of an increasing number of antibiotic-resistant Campylobacter strains that can be transmitted to humans through the food chain. Of particular concern to public health is the prevalence of resistance to macrolides and fluoroquinolones that are used in the treatment of life-threatening campylobacteriosis. The CmeABC efflux system has been shown to contribute to the intrinsic and acquired resistance to these antibiotics. In addition, by mediating resistance to bile, it is essential for colonization of the chicken gut in vivo. Inhibition of CmeABC may provide an effective means of reversing antibiotic resistance and decreasing the transmission of Campylobacter via the food chain. This would positively impact on public health by decreasing the morbidity, mortality and increased healthcare costs associated with the treatment of antibiotic-resistant Campylobacter.

[Bacterial meningitis with Campylobacter fetus manifesting chronic clinical course]

A 43-year-old man with no past history of underlying disease was admitted to an affiliated hospital, complaining of high fever and severe headache. Polynuclear dominant pleocytosis in the cerebrospinal fluid (CSF) suggested bacterial meningitis. He was immediately treated with several antibiotics, then his clinical symptoms improved, although intractable headache relapsed after withdrawal of the initial therapy. Thereafter he consulted our hospital for a second opinion. CSF examination in our hospital demonstrated mononuclear dominant pleocytosis with normal sugar value. However, bacterial culture of the CSF specimen yielded a gram-negative bacillus that was finally identified as a Campylobacter fetus on Skirrow's culture. Treatment with meropenem and other antibiotics improved both the clinical symptoms and CSF findings. Thus, meningitis with a Campylobacter fetus could manifest a chronic and atypical clinical course, careful attention should be paid to establish an early diagnosis.

Isolation of a Lactobacillus salivarius strain and purification of its bacteriocin, which is inhibitory to Campylobacter jejuni in the chicken gastrointestinal system

We evaluated anti-Campylobacter jejuni activity among >1,200 isolates of different lactic acid bacteria. Lactobacillus salivarius strain NRRL B-30514 was selected for further study. The cell-free, ammonium sulfate precipitate from the broth culture was termed the crude antimicrobial preparation. Ten microliters of the crude preparation created a zone of C. jejuni growth inhibition, and growth within the zone resumed when the crude preparation was preincubated with proteolytic enzymes. Bacteriocin OR-7, derived from this crude preparation, was further purified using ion-exchange and hydrophobic-interaction chromatography. The determined amino acid sequence was consistent with class IIa bacteriocins. Interestingly, OR-7 had sequence similarity, even in the C-terminal region, to acidocin A, which was previously identified from L. acidophilus and had activity only to gram-positive bacteria, whereas OR-7 had activity to a gram-negative bacterium. Bacteriocin activity was stable following exposure to 90 degrees C for 15 min, also consistent with these types of antibacterial peptides. The purified protein was encapsulated in polyvinylpyrrolidone and added to chicken feed. Ten day-of-hatch chicks were placed in each of nine isolation units; two groups of birds were challenged with each of four C. jejuni isolates (one isolate per unit). At 7 days of age, one group of birds was treated with bacteriocin-emended feed for 3 days, and one group was left untreated. At 10 days of age, the birds were sacrificed and the challenge strain was enumerated from the bird cecal content. Bacteriocin treatment consistently reduced colonization at least one millionfold compared with levels found in the untreated groups. Nonchallenged birds were never colonized by C. jejuni. Bacteriocin from L. salivarius NRRL B-30514 appears potentially very useful to reduce C. jejuni in poultry prior to processing.

Strain and host characteristics of Campylobacter jejuni infections in Finland

The relative importance of different risk-factors for Campylobacter infections and the role of bacterial strain and host characteristics are uncertain. Swimming in natural sources of water was recently described as a novel independent risk-factor for domestically-acquired Campylobacter infections. The present study investigated exposure factors and demographical characteristics (collected in a questionnaire), and determined whether Campylobacter jejuni serotypes could be linked to each other or to the severity of the disease in domestically-acquired sporadic C. jejuni infections during a seasonal peak in Finland. Swimming was associated positively with an age of <or= 5 years, and C. jejuni serotype Pen 6,7 was found significantly more frequently among patients who reported swimming. The geographical distribution among serotypes differed, in that 54% of the isolates belonging to the Pen 4 complex serotype were identified in the Helsinki area, and 74% of the Pen 21 isolates were from the Kuopio area. Pen 57 was associated with a disease of shorter duration, but no serotype could be linked to hospitalisation or antimicrobial therapy. However, advanced age was associated with hospitalisation and a longer period of hospitalisation. Risk-factors and sources of infection for C. jejuni infection may not be identical for all individuals. This study supports the concept that individuals belonging to different age groups and living in different geographical areas may acquire C. jejuni infections from different sources.

Phenotypic and genotypic anti-microbial resistance profiles of campylobacters from untreated feedlot cattle and their environment

Anti-microbial resistance is an emerging public health issue. Farmed animals may act as reservoirs and potential sources of anti-microbial resistant Campylobacters. The aim of this study was to investigate the anti-microbial resistance profile of cattle and environmental Campylobacter isolates from normal untreated feedlot cattle, the role of the gyrA Thr-86-Ile mutation in ciprofloxacin-resistant Campylobacter jejuni isolates and the involvement of the tripartite CmeABC efflux system for multi-resistant C. jejuni isolates. The phenotypic anti-microbial resistance testing was carried out on 500 Campylobacter isolates (445 cattle isolates and 55 environmental isolates). In general, there was a higher level of anti-microbial resistance for the environmental isolates compared with the animal isolates, 45% of the animal isolates were resistant to one or more of the seven anti-microbials compared with 84% of the environmental isolates. The combined cattle and environmental Campylobacters had 34 (6.8%) isolates resistant to three or more of the seven anti-microbials tested on all isolates and 11 (2.2%) isolates were resistant to the seven anti-microbials. There was a substantial level of ciprofloxacin-resistant Campylobacters in both animal (8.5%) and environmental (21.8%) isolates. The gyrA Thr-86-Ile mutation was only present in five of 22 ciprofloxacin-resistant C. jejuni isolates investigated. No multi-drug-resistant associated mutation was detected in the CmeB or the CmeR regions investigated. In conclusion, our study observed a substantial level of Campylobacter anti-microbial resistance, highlighting the need for an active anti-microbial surveillance program for food animals in Ireland and the importance of the chosen sampling point can have on the findings of such a program.

Macrolide resistance in Campylobacter jejuni and Campylobacter coli

Infection with Campylobacter jejuni is now considered to be the most common cause of acute bacterial gastroenteritis in humans worldwide. It occurs more frequently than infections caused by Salmonella species, Shigella species, or Escherichia coli O157:H7. Although C. jejuni is also recognized for its association with serious post-infection neurological complications, most patients with C. jejuni infections have a self-limited illness. Nevertheless, a substantial proportion of these infections are treated with antibiotics. These include severe and prolonged cases of enteritis, infections in immune-suppressed patients, septicaemia and other extra-intestinal infections. Under these circumstances, erythromycin is often recommended as the drug of first choice. However, erythromycin-resistant Campylobacter have emerged during therapy with macrolides. Moreover, the widespread use of macrolides, including erythromycin, in veterinary medicine has accelerated this resistance trend. Several countries including Canada, Japan and Finland have reported C. jejuni isolates with low and stable rates of macrolide resistance. In contrast, the increasing level of macrolide resistance in C. jejuni is becoming a major public health concern in other parts of the world such as the United States, Europe and Taiwan. Macrolide resistance in Campylobacter is mainly associated with point mutation(s) occurring in the peptidyl-encoding region in domain V of the 23S rRNA gene, the target of macrolides. Several rapid and practical techniques have recently been developed for the identification of macrolide-resistant isolates of C. jejuni. The aim of this mini-review is to give an overview of the worldwide distribution of macrolide resistance in C. jejuni and Campylobacter coli as well as its possible association with the massive use of these agents in food animals. Mechanisms implicated in macrolide resistance in C. jejuni and also techniques that have been developed for the efficient detection of macrolide-associated mutation(s) will be discussed in detail.

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.

Effect of Glycerol Monocaprate (Monocaprin) on Broiler Chickens: An Attempt at Reducing Intestinal Campylobacter Infection

Attempts have been made by several workers to prevent or to reduce colonization of Campylobacter in the intestines of broiler chickens by adding antibacterial agents to their food, but the results have varied. Monocaprin, the 1-monoglyceride of capric acid, has been found to be very active in killing Campylobacter in vitro. It was therefore studied whether Campylobacter infection in chickens would be affected by adding emulsions of monocaprin to their drinking water and feed. It was found that treatment with monocaprin in water and feed did not prevent spread of Campylobacter from artificially infected to noninfected 24-d-old chickens, but Campylobacter counts in cloacal swabs were significantly reduced, particularly during the first 2 d of treatment. There was also a significant reduction in the Campylobacter counts in cloacal swabs of naturally infected 36-d-old broilers that were treated for 3 d prior to slaughter. Addition of monocaprin to drinking water and feed 2 to 3 d before slaughter might therefore be considered as a means of reducing Campylobacter infection in broilers, possibly in conjunction with other antibacterial agents such as short-chain organic acids. Further studies are needed to determine whether this would reduce carcass contamination.

A case of perinatal sepsis by Campylobacter fetus subsp. fetus infection successfully treated with carbapenem--case report and literature review

Infection due to Campylobacter fetus subsp. fetus during pregnancy is uncommon in humans. We report a case of a pregnant woman who experienced premature labor. The infant was diagnosed with neonatal sepsis due to C. fetus subsp. fetus, and was successfully treated with carbapenem. Maternal clinical symptoms and severe villitis suggested that the route of fetal infection was hematogenous spread. We also review previous reports in the literature that describe this infection during pregnancy.

Antimicrobial resistance in Campylobacter jejuni from humans and broilers in Norway

In this study comprising isolates from 2001 to 2003, resistance was considerably more widespread among Campylobacter jejuni from humans infected abroad than infected within Norway. The discrepancy was particularly notable for fluoroquinolone resistance (67.4% vs. 6.5%). This is probably a reflection of a low resistance prevalence in Norwegian broiler isolates (1.2% fluoroquinolone resistant).

Epidemiology of Campylobacter jejuni and Campylobacter coli infections in the Zenica--Doboj Canton, Bosnia and Herzegovina--a laboratory based surveillance in the 1999-2001 period

Previous studies in the Zenica--Doboj Canton, Bosnia and Herzegovina, indicated some different epidemiological features of Campylobacter infections and high degree of antimicrobial resistance. Therefore, it was important to investigate epidemiology of Campylobacter jejuni and Campylobacter coli infections by demographic features and antimicrobial resistance in the 1999-2001 period. A total number of 40 (75.5%) C. jejuni and 13 (24.5%) C. coli non-repeated clinical isolates were analyzed. More than half of isolates, 30 (56.6%) were from urban dwellers. Campylobacter isolates mainly obtained from children under 6 years of age, 42 (79.2%), resulting in far off highest incidence rate of 41.4/100,000/year in this age group. There was noted high degree of resistance to ciprofloxacin in children less than 6 years of age (14.3%), and extremely high overall erythromycin-resistance rate (30%). Campylobacteriosis in this region is a public health concern not in the term of the number reported cases, but of distinctive epidemiologic features.

The Dynamics of Antimicrobial-Resistant Campylobacter jejuni on Japanese Broiler Farms

We investigated for dynamics of Campylobacter clones on 2 different managerial broiler farms. Campylobacter isolates were differentiated by resistance typing and molecular typing methods. On farm I, the same C. jejuni clones resistant to fluoroquinolone and oxytetracycline were isolated after one and half years again and another susceptible clone was invaded. The susceptible clone was isolated again after half year. Broiler flocks on the farm may be repeatedly infected with a few C. jejuni clones. On farm II, new clones including antimicrobial resistant one, were often invaded. The change of predominant C. jejuni clone in each flock on both the farms was observed, in the absence of antimicrobial selective pressure.

Emergence of Fluoroquinolone Resistance in Campylobacter jejuni in Chickens Exposed to Enrofloxacin Treatment at the Inherent Dosage Licensed in Japan

The objective of the present study was to determine whether selection of fluoroquinolone resistance could be easily induced in Campylobacter jejuni-colonized chickens by treatment with enrofloxacin of representative fluoroquinolones at the inherent dosage licensed in Japan (50 ppm in drinking water for 3 days). In the case of isolates from chickens of study 1, an increase in the population of susceptible isolates appeared after the cessation of treatment and maintained throughout the experiments. On the contrary, our results of study 2 demonstrated that administration of enrofloxacin generated a rapid increase of fluoroquinolone resistance in C. jejuni showing the mutation of Asp-90-Asn in the gyrA gene. Present results indicate that the enrofloxacin treatment for broilers at the inherent dosage is able to select fluoroquinolone resistance in C. jejuni. We conclude that whatever enrofloxacin dosage is used, an emergence of fluoroquinolone resistant of C. jejuni occurs.

Relative contribution of target gene mutation and efflux to varying quinolone resistance in Irish Campylobacter isolates

The contribution of target gene mutations and active efflux to varying levels of quinolone resistance in Irish Campylobacter isolates was studied. The Thr-86-Ile modification of GyrA did not correlate with the level of quinolone resistance. The efflux pump inhibitor Phe-Arg-beta-Naphthylamide (PAbetaN) had no effect on the MICs to ciprofloxacin. In contrast, a PAbetaN sensitive efflux system contributed to the low-level nalixidic acid resistance phenotype. The lack of effect of PAbetaN in high-level resistant nalidixic isolates may be attributable to mutations identified in the CmeB efflux pump of these isolates. PAbetaN may have limited diagnostic value in the assessment of the contribution of efflux pump activity to ciprofloxacin resistance in Campylobacter.