Macrolide-resistant Campylobacter: the meat of the matter

Erythromycin Restores Osteoblast Differentiation and Osteogenesis Suppressed by Porphyromonas gingivalis Lipopolysaccharide

The macrolide erythromycin (ERM) inhibits excessive neutrophil accumulation and bone resorption in inflammatory tissues. We previously reported that the expression of developmental endothelial locus-1 (DEL-1), an endogenous anti-inflammatory factor induced by ERM, is involved in ERM action. Furthermore, DEL-1 is involved in the induction of bone regeneration. Therefore, in this study, we investigated whether ERM exerts an osteoblastogenic effect by upregulating DEL-1 under inflammatory conditions. We performed in vitro cell-based mechanistic analyses and used a model of Porphyromonas gingivalis lipopolysaccharide (LPS)-induced periodontitis to evaluate how ERM restores osteoblast activity. In vitro, P. gingivalis LPS stimulation suppressed osteoblast differentiation and bone formation. However, ERM treatment combined with P. gingivalis LPS stimulation upregulated osteoblast differentiation-related factors and Del1, indicating that osteoblast differentiation was restored. Alveolar bone resorption and gene expression were evaluated in a periodontitis model, and the results confirmed that ERM treatment increased DEL-1 expression and suppressed bone loss by increasing the expression of osteoblast-associated factors. In conclusion, ERM restores bone metabolism homeostasis in inflammatory environments possibly via the induction of DEL-1.

Resistance to Antibiotics in Thermophilic Campylobacters

Campylobacter jejuni (C. jejuni) is one of the most frequent causes of bacterial enterocolitis globally. The disease in human is usually self-limiting, but when complications arise antibiotic therapy is required at a time when resistance to antibiotics is increasing worldwide. Mechanisms of antibiotic resistance in bacteria are diverse depending on antibiotic type and usage and include: enzymatic destruction or drug inactivation; alteration of the target enzyme; alteration of cell membrane permeability; alteration of ribosome structure and alteration of the metabolic pathway(s). Resistance of Campylobacter spp. to antibiotics, especially fluoroquinolones is now a major public health problem in developed and developing countries. In this review the mechanisms of resistance to fluoroquinolones, macrolides, tetracycline, aminoglycoside and the role of integrons in resistance of Campylobacter (especially at the molecular level) are discussed, as well as the mechanisms of resistance to β-lactam antibiotics, sulphonamides and trimethoprim. Multiple drug resistance is an increasing problem for treatment of campylobacter infections and emergence of resistant strains and resistance are important One Health issues.

Characterization of Campylobacter associated gastric enteritis among patients with Human Immunodeficiency Virus (HIV) in a hospital in Accra, Ghana

BACKGROUND

Campylobacter infections in HIV positive patients often present with substantial mortality and morbidity when compared to HIV negative patients.

AIM

This study assessed the prevalence of Campylobacter, antibiotic resistance phenotypes and genetic factors, and risk of Campylobacter infection associated with living in close proximity to domestic animals in HIV patients with gastric enteritis at Korle-Bu Teaching Hospital, Accra, Ghana.

METHODS

Resistance to different antibiotics was assessed with Kirby-Bauer disk diffusion method. In addition, all the Campylobacter isolates were tested for ampicillin (blaOXA-61), erythromycin (aph-3-1), tetracycline tet(O), streptomycin (aadE), and the energy-dependent multi-drug efflux pump (cmeB) resistance genes using multiplex polymerase chain reaction.

RESULTS

Out of a total of 140 (97 females and 43 males) tested patients, 71 (50.7%) patients were positive for Campylobacter coli. Female patients aged within 31-40 years (31.6%) and 41-50 years (31.6%) had high frequency of Campylobacter infection. Most of the infected patients lived in close proximity to chickens (53.5%), however, some patients (14.1%) lived in close proximity to goats. Phenotypic resistance evaluation revealed widespread resistance to ampicillin (100%), tetracycline (100%), ciprofloxacin (71.8%), erythromycin (69%), and gentamicin (49.3%). However, limited no of isolates contained blaOXA-61 (1.41%), cmeB (7.0%) and tet(O (7.0%) resistance genes.

CONCLUSION

HIV patients with gastric enteritis were infected with resistant Campylobacter coli. Further studies are required to examine correlation of infected patients with C. coli and risk of living in close proximity to poultry birds. There is the need for routine investigation of Campylobacter in patients with gastroenteritis in order to assist in the development of strategies for combating diseases involving resistant zoonotic bacteria strains.

Campylobacter jejuni bacteremia in a patient with asplenia and enteritis

Campylobacter bacteremia is an unusual presentation of a common infectious disease such as enteritis. We provide key teaching points about its presentation, risk factors, diagnosis and treatment.

Antimicrobial susceptibility of Campylobacter jejuni and Campylobacter coli: comparison between Etest and a broth dilution method

Background

Campylobacter is a leading cause of foodborne gasteroenteritis worldwide. Antimicrobial susceptibility testing for Campylobacter spp. is not routinely performed by most clinical laboratories. However, the emergence of resistant isolates strengthens the importance of antimicrobial susceptibility testing and the critical need for epidemiologic surveillance. The aim of this study was to compare the efficacy of Etest and Sensititre kit (a broth microdilution method) as methods for susceptibility tests and the critical need for epidemiologic surveillance. The aim of this study was to compare the efficacy of Etest and Sensititre kit (a broth microdilution method) as methods for susceptibility testing of Campylobacter spp. to tetracycline, erythromycin, and ciprofloxacin.

Methods

Sixty-six Campylobacter isolates were collected from feces samples and subjected to susceptibility testing by Etest and Sensititre, a broth microdilution kit for tetracycline, erythromycin, and ciprofloxacin. Minimal inhibitory concentration (MIC) results of each method were determined and compared.

Results

Similar MIC interpretations for tetracycline, erythromycin, and ciprofloxacin were found in 97%, 98.5%, and 100% of the isolates, respectively, indicating a good level of agreement between Etest and Sensititre (p < 0.0001); additionally, the correlation between the two methods was highly significant for the three tested antibiotics (p < 0.0001).

Conclusions

Both the broth microdilution and the Etest are reliable and convenient methods for testing antimicrobial susceptibility of Campylobacter spp. The Sensititre kit has the advantages of high availability and the automation.

Genetic Basis and Clonal Population Structure of Antibiotic Resistance in Campylobacter jejuni Isolated From Broiler Carcasses in Belgium

Human campylobacteriosis is the leading food-borne zoonosis in industrialized countries. This study characterized the clonal population structure, antimicrobial resistance profiles and occurrence of antimicrobial resistance determinants of a set of Campylobacter jejuni strains isolated from broiler carcasses in Belgium. Minimum inhibitory concentrations (MICs) against five commonly-used antibiotics (ciprofloxacin, nalidixic acid, tetracycline, gentamicin, and erythromycin) were determined for 204 C. jejuni isolates. More than half of the isolates were resistant to ciprofloxacin or nalidixic acid. In contrast, a lower percentage of screened isolates were resistant to gentamicin or erythromycin. C. jejuni isolates resistant to ciprofloxacin and/or nalidixic acid were screened for the substitution T86I in the quinolone resistance determining region (QRDR) of the gyrA gene, while C. jejuni isolates resistant to tetracycline were screened for the presence of the tet(O) gene. These resistance determinants were observed in most but not all resistant isolates. Regarding resistance to erythromycin, different mutations occurred in diverse genetic loci, including mutations in the 23S rRNA gene, the rplD and rplV ribosomal genes, and the intergenic region between cmeR and cmeABC. Interestingly, and contrary to previous reports, the A2075G transition mutation in the 23S rRNA gene was only found in one strain displaying a high level of resistance to erythromycin. Ultimately, molecular typing by multilocus sequence typing revealed that two sequence types (ST-824 and ST-2274) were associated to quinolones resistance by the presence of mutations in the gene gyrA (p = 0.01). In addition, ST-2274 was linked to the CIP-NAL-TET-AMR multidrug resistant phenotype. In contrast, clonal complex CC-45 was linked to increased susceptibility to the tested antibiotics. The results obtained in this study provide better understanding of the phenotypic and the molecular basis of antibiotic resistance in C. jejuni, unraveling some the mechanisms which confer antimicrobial resistance and particular clones associated to the carriage and spread of resistance genes.

Effects of low concentrations of erythromycin, penicillin, and virginiamycin on bacterial resistance development in vitro

Distillers grains are co-products of the corn ethanol industry widely used in animal feed. We examined the effects of erythromycin, penicillin, and virginiamycin at low concentrations reflective of those detected in distillers grains on bacterial resistance selection. At 0.1 µg/ml erythromycin, macrolide-resistant mutants were induced in one Campylobacter coli and one Enterococcus faecium strain, while these strains plus three additional C. coli, one additional E. faecium, and one C. jejuni also developed resistance when exposed to 0.25 µg/ml erythromycin. At 0.5 µg/ml erythromycin, a total of eight strains (four Campylobacter and four Enterococcus) obtained macrolide-resistant mutants, including two strains from each genus that were not selected at lower erythromycin concentrations. For penicillin, three of five E. faecium strains but none of five Enterococcus faecalis strains consistently developed resistance at all three selection concentrations. Virginiamycin at two M₁:S₁ ratios did not induce resistance development in four out of five E. faecium strains; however, increased resistance was observed in the fifth one under 0.25 and 0.5 µg/ml virginiamycin selections. Although not yet tested in vivo, these findings suggest a potential risk of stimulating bacterial resistance development in the animal gut when distillers grains containing certain antibiotic residues are used in animal feed.

Epidemiological relationships of Campylobacter jejuni strains isolated from humans and chickens in South Korea

Thirty-nine human isolates of Campylobacter jejuni obtained from a national university hospital during 2007-2010 and 38 chicken isolates of C. jejuni were collected from poultry farms during 2009-2010 in South Korea were used in this study. Campylobacter genomic species and virulence-associated genes were identified by PCR. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were performed to compare their genetic relationships. All isolates were highly resistant to ciprofloxacin, nalidixic acid, and tetracycline. Of all isolates tested, over 94% contained seven virulence associated genes (flaA, cadF, racR, dnaJ, cdtA, cdtB, and cdtC). All isolates were classified into 39 types by PFGE clustering with 90% similarity. Some chicken isolates were incorporated into some PFGE types of human isolates. MLST analysis for the 39 human isolates and 38 chicken isolates resulted in 14 and 23 sequence types (STs), respectively, of which 10 STs were new. STs overlapped in both chicken and human isolates included ST-21, ST-48, ST-50, ST-51, and ST-354, of which ST-21 was the predominant ST in both human and chicken isolates. Through combined analysis of PFGE types and STs, three chicken isolates were clonally related to the three human isolates associated with food poisoning (VII-ST-48, XXII-ST-354, and XXVIII-ST-51). They were derived from geographically same or distinct districts. Remarkably, clonal spread of food poisoning pathogens between animals and humans was confirmed by population genetic analysis. Consequently, contamination of campylobacters with quinolone resistance and potential virulence genes in poultry production and consumption may increase the risk of infections in humans.

Constitutive and Inducible Expression of the rRNA Methylase Gene erm(B) in Campylobacter

Macrolides are the antimicrobials of choice for treating human campylobacteriosis. The recent emergence of erm(B) in Campylobacter bacteria threatens the utility of this class of antibiotics. Here we report the constitutive and inducible expression of erm(B) in Campylobacter isolates derived from diarrheal patients and food-producing animals. Constitutive expression of erm(B) was associated with insertion and deletion in the regulatory region of the gene, providing the first documentation of the differential expression of erm(B) in Campylobacter bacteria.

Molecular mechanisms of quinolone, macrolide, and tetracycline resistance among Campylobacter isolates from initial stages of broiler production

The aim of this study was to investigate the resistance mechanisms of quinolones, macrolides and tetracycline in campylobacter isolates from grandparent and parent broiler breeders in Spain. Twenty-six isolates were investigated for quinolone resistance, three isolates for macrolide resistance and 39 for tetracycline resistance. All of the quinolone-resistant isolates possessed the mutation Thr86Ile in the quinolone resistance-determining region of gyrA and one isolate possessed the mutation Pro104Ser. Only one Campylobacter coli population (defined by restriction fragment length polymorphism-polymerase chain reaction of flaA and pulsed field gel electrophoresis) was resistant to erythromycin, and the mutation A2075G (23S rDNA) was responsible for macrolide resistance. The tetO gene was found in all of the tetracycline-resistant isolates. Twenty-two out of the 39 isolates investigated by Southern blot possessed chromosomic location of tetO and 17 were located on plasmids. Most of the plasmids with tetO were of around 60 kb and conjugation was demonstrated in a selection of them. In conclusion, we showed that Thr86Ile is highly prevalent in quinolone-resistant isolates as well as mutation A2075G in macrolide-resistant isolates of poultry origin. More variability was found for tetO. The possibility of horizontal transmission of tetO among campylobacter isolates is also an issue of concern in public health.

Antibiotic susceptibility pattern and genotyping of campylobacter species isolated from children suffering from gastroenteritis

PURPOSE

To study the prevalence and the antimicrobial resistance of campylobacter species isolated from children suffering from gastroenteritis .

MATERIALS AND METHODS

A total of 125 stool samples were collected from children with gastroenteritis. The identification of isolates was performed with conventional methods as well as with molecular methods based on 16SrRNA species-specific gene amplification by PCR and product analysis. Resistance pattern of the isolated strains was determined using agar dilution method.

RESULTS

Conventional methods including sodium hippurate hydrolysis revealed that 12 (9.6%) samples were positive for Campylobacter species. Ten out of 12 Campylobacter spp. were identified as Campylobacter jejuni and 2 as Campylobacter coli but PCR assay revealed that five samples only were positive for Campylobacter and all were C. jejuni. Antimicrobial susceptibility to 10 antimicrobials was performed and all isolates (five isolates of C. jejuni) were susceptible to chloramphenicol, gentamicin and amikacin but all were resistant to ceftriaxone.

CONCLUSION

PCR assay method allows reliable detection of C. jejuni. C. jejuni was the most prevalent Campylobacter species. Gentamicin, amikacin and chloramphenicol were the most effective antibiotic.

Evaluation of potassium-clavulanate-supplemented modified charcoal-cefoperazone-deoxycholate agar for enumeration of Campylobacter in chicken carcass rinse

Potassium-clavulanate-supplemented modified charcoal-cefoperazone-deoxycholate agar (C-mCCDA) that was described in our previous study was compared with original mCCDA for the enumeration of Campylobacter in pure culture and chicken carcass rinse. The quantitative detection of viable Campylobacter cells from a pure culture, plated on C-mCCDA, is statistically similar (P > 0.05) to mCCDA. In total, 120 chickens were rinsed using 400 mL buffered peptone water. The rinses were inoculated onto C-mCCDA and mCCDA followed by incubation at 42 °C for 48 h. There was no statistical difference between C-mCCDA (45 of 120 plates; mean count, 145.5 CFU/mL) and normal mCCDA (46 of 120 plates; mean count, 160.8 CFU/mL) in the isolation rate and recovery of Campylobacter (P > 0.05) from chicken carcass rinse. The Pearson correlation coefficient value for the number of Campylobacter cells recovered in the 2 media was 0.942. However, the selectivity was much better on C-mCCDA than on mCCDA plates (P < 0.05). Significantly fewer C-mCCDA plates (33 out of 120 plates; mean count, 1.9 CFU/mL) were contaminated with non-Campylobacter cells than the normal mCCDA plates (67 out of 120 plates; mean count, 27.1 CFU/mL). The C-mCCDA may provide improved results for enumeration of Campylobacter in chicken meat alternative to mCCDA with its increased selectivity the modified agar possess.

Macrolides and lincosamides in cattle and pigs: use and development of antimicrobial resistance

Macrolides and lincosamides are important antibacterials for the treatment of many common infections in cattle and pigs. Products for in-feed medication with these compounds in combination with other antimicrobials are commonly used in Europe. Most recently approved injectable macrolides have very long elimination half-lives in both pigs and cattle, which allows once-only dosing regimens. Both in-feed medication and use of long-acting injections result in low concentrations of the active substance for prolonged periods, which causes concerns related to development of antimicrobial resistance. Acquired resistance to macrolides and lincosamides among food animal pathogens, including some zoonotic bacteria, has now emerged. A comparison of studies on the prevalence of resistance is difficult, since for many micro-organisms no agreed standards for susceptibility testing are available. With animal pathogens, the most dramatic increase in resistance has been seen in the genus Brachyspira. Resistance towards macrolides and lincosamides has also been detected in staphylococci isolated from pigs and streptococci from cattle. This article reviews the use of macrolides and lincosamides in cattle and pigs, as well as the development of resistance in target and some zoonotic pathogens. The focus of the review is on European conditions.

The design of a capsule polysaccharide conjugate vaccine against Campylobacter jejuni serotype HS15

Campylobacter jejuni infection is now the main cause of diarrhea-related illnesses in humans. An efficacious vaccine for the traveler and developing world market would be welcomed. We are engaged in the discovery and characterization of serotype-specific C. jejuni capsule polysaccharides (CPSs) to study their role in virulence and as protective vaccine antigens. Our prototype conjugate vaccine with serotype HS23 CPS (strain 81-176) has been shown to fully protect non-human primates against diarrhea inflicted by C. jejuni HS23, but ultimately, a useful CPS-based vaccine will have to be multivalent. To this end, we describe here the creation of a CPS-conjugate vaccine against C. jejuni serotype HS15. Structural analysis revealed that a repeating block consisting of L-α-arabinofuranose (Ara) and 6-deoxy-L-α-gulo-heptopyranose (6d-gulo-Hep) comprised the CPS of serotype HS15 type strain ATCC 43442 [→3)-α-L-Araf-(1→3)-6d-L-α-gulo-Hepp(1→](n). Strategically, the non-reducing end of the CPS was activated and used in the attachment of CPS to CRM₁₉₇ to yield a conjugate vaccine. A serological assessment of the CPS(HS15)-CRM₁₉₇ conjugate with an anti-HS15 polyclonal antibody confirmed the conservation of antigenic epitopes, and subsequent inoculation of mice with CPS(HS15)-CRM₁₉₇ revealed that this conjugate was indeed capable of raising anti-CPS(HS15) antibodies.

Comparison of 2 types of broths and 3 selective agars for the detection of Campylobacter species in whole-chicken carcass-rinse samples

In this study, we compared the effectiveness of 2 types of Bolton broths and 3 selective media for isolating Campylobacter spp. from naturally contaminated whole-chicken carcass-rinse samples. One hundred chickens were rinsed with buffered peptone water, and the rinses were added to 2× Bolton broth (with or without blood supplementation). The samples were incubated and then streaked onto Preston agar, modified cefoperazone charcoal deoxycholate agar (mCCDA), and Campy-Cefex agar, which was followed by incubation under microaerobic conditions. No statistical differences were observed (P > 0.05) in isolation rate and selectivity between the 2 types of Bolton broths. Among the 3 selective agars, Preston agar yielded a significantly (P < 0.05) better isolation rate and selectivity. The Campy-Cefex agar, which is recommended by many food authorities for its high quantitative detection ability, showed extensive contamination with competing microorganisms and exhibited the lowest isolation rate and selectivity.

Campylobacter antimicrobial resistance in Peru: a ten-year observational study

Background

Campylobacter jejuni and Campylobacter coli are food-borne pathogens of great importance and feature prominently in the etiology of developing world enteritis and travellers’ diarrhoea. Increasing antimicrobial resistant Campylobacter prevalence has been described globally, yet data from Peru is limited. Our objective was to describe the prevalence trends of fluoroquinolone and macrolide-resistant C. jejuni and C. coli stool isolates from three regions in Peru over a ten-year period.

Methods

Surveillance for enteric pathogens was conducted in Lima, Iquitos and Cusco between 2001 and 2010. Campylobacter stool isolates were tested for susceptibilities to ciprofloxacin, azithromycin and erythromycin. Susceptibilities were reviewed for 4652 isolates from Lima ( n = 3419), Iquitos ( n = 625) and Cusco ( n = 608).

Results

Comparing the study periods of 2001-2005 and 2006-2010, prevalence of ciprofloxacin-resistant C. jejuni isolates rose in the study areas of Lima (73.1% to 89.8%, p < 0.001) and Iquitos (24.1% to 48.9%, p < 0.001). Ciprofloxacin-resistant C. coli rates also increased in Lima (48.1% to 87.4%, p < 0.001) and Cusco (10.0% to 65.9%, p = 0.005). Small but significant increases in azithromycin-resistant and erythromycin-resistant C. jejuni prevalence were noted in Iquitos (2.2% to 14.9%, p < 0.001; 3.2% to 14.9%, p = 0.002), and erythromycin-resistant C. coli rates increased in Lima (0.0% to 5.3%, p = 0.038). The prevalence of C. jejuni isolates resistant to both ciprofloxacin and azithromycin increased in Iquitos (0.3% to 14.9%, p < 0.001) and Lima (0.3% to 1.6%, p = 0.011), and prevalence of C. jejuni isolates resistant to both ciprofloxacin and erythromycin rose in Iquitos (0.0% to 14.9%, p < 0.001). Ciprofloxacin and erythromycin resistant C. coli prevalence increased in Lima (0.0% to 5.3%, p = 0.034).

Conclusions

These results have implications for the empirical management of enterocolitis in Peru. Ongoing surveillance is essential to guide appropriate antimicrobial use in this setting. Local epidemiological studies to explore the relationship between increasing antimicrobial resistance and agricultural or human antibiotic use may be valuable.

Three cases of acute gastroenteritis caused by high-level macrolideresistant Campylobacter: drug resistance mechanisms and clinical characteristics

We report 3 cases of acute gastroenteritis caused by high-level macrolide-resistant Campylobacter. The clinical characteristics of patients were studied, and the rplD, rplV, and 23S rRNA domain V genes were sequenced to detected resistance-related mutations.

Identification and antimicrobial resistance of campylobacter species isolated from animal sources

Background:Campylobacter spp. are together with Salmonella spp. the leading causes of human bacterial gastroenteritis worldwide. The most commonly isolated species in humans are Campylobacter jejuni and C. coli. The isolation, identification, and antimicrobial resistance of Campylobacter spp. from poultry and raw meat from slaughterhouses, has been investigated for the first time in Greece. During the period from August 2005 to November 2008 a total of 1080 samples were collected: (a) 830 fecal samples from five poultry farms, (b) 150 cecal samples from chicken carcasses in a slaughterhouse, and (c) 100 fecal samples from one pig farm near the region of Attica. The identification of the isolates was performed with conventional (sodium hippurate hydrolysis and commercial identification system (Api CAMPY system, bioMerieux, France), as well as with and molecular methods based on 16S rRNA species specific gene amplification by PCR and subsequent sequence analysis of the PCR products. Results: Sixteen Campylobacter strains were isolated, all collected from the poultry farms. None of the strains was identified as C. jejuni. Antimicrobial susceptibility to six antimicrobials was performed and all the strains were susceptible to ciprofloxacin, amoxicillin–clavulanic acid, and gentamicin. Thirteen out of 14 C. coli were resistant to erythromycin and all C. coli strains were resistant to ampicillin. Conclusion: Our results emphasize the need for a surveillance and monitoring system with respect to the prevalence and antimicrobial resistance of Campylobacter in poultry, as well as for the use of antimicrobials in veterinary medicine in Greece.

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.

Study of the molecular mechanisms involved in high-level macrolide resistance of Spanish Campylobacter jejuni and Campylobacter coli strains

OBJECTIVES

To investigate the molecular mechanisms involved in the high-level erythromycin resistance of clinical Spanish Campylobacter jejuni and Campylobacter coli strains.

METHODS

Overall susceptibilities of 678 C. jejuni and 119 C. coli strains, collected from 10 Spanish provinces during 2006 and 2007, were determined by Etest. In high-level erythromycin-resistant strains, molecular determinants were studied. The analysis was focused on region V of the 23S rRNA gene, the rplD and rplV ribosomal genes, and the regulatory region of the CmeABC efflux pump.

RESULTS

The global resistance rate to erythromycin was 3.8%. Among the resistant strains, 93% were C. coli and 7% were C. jejuni. The A2075G mutation in the 23S rRNA gene was detected in all of the resistant strains except for two, which carried the A2074G mutation. None of the ribosomal rplD and rplV genes harboured the described mutations that confer resistance to macrolides. Different mutations affecting the regulatory region of the CmeABC efflux pump were also found.

CONCLUSIONS

C. coli strains are clearly more resistant to erythromycin than C. jejuni. The mutation A2075G in the 23S rRNA gene was responsible for the resistance in most of the strains; A2074G was only found in two strains. Further studies are required to ascertain the effect of mutations in the regulatory region of cmeABC. Our data indicate that the rate of resistance was similar to that of other European countries.

Antimicrobial susceptibilities of multidrug-resistant Campylobacter jejuni and C. coli strains: in vitro activities of 20 antimicrobial agents

There is a paucity of information regarding antimicrobial agents that are suitable to treat severe infections caused by multidrug-resistant Campylobacter spp. Our aim was to identify agents that are potentially effective against multiresistant Campylobacter strains. The in vitro activities of 20 antimicrobial agents against 238 Campylobacter strains were analyzed by determining MICs by the agar plate dilution method or the Etest. These strains were selected from 1,808 Campylobacter isolates collected from Finnish patients between 2003 and 2005 and screened for macrolide susceptibility by using the disk diffusion test. The 238 strains consisted of 183 strains with erythromycin inhibition zone diameters of < or =23 mm and 55 strains with inhibition zone diameters of >23 mm. Of the 238 Campylobacter strains, 19 were resistant to erythromycin by MIC determinations (MIC > or = 16 microg/ml). Given that the resistant strains were identified among the collection of 1,808 isolates, the frequency of erythromycin resistance was 1.1%. All erythromycin-resistant strains were multidrug resistant, with 18 (94.7%) of them being resistant to ciprofloxacin (MIC > or = 4 microg/ml). The percentages of resistance to tetracycline and amoxicillin-clavulanic acid (co-amoxiclav) were 73.7% and 31.6%, respectively. All macrolide-resistant strains were susceptible to imipenem, meropenem, and tigecycline. Ten (52.6%) multiresistant strains were identified as being Campylobacter jejuni strains, and 9 (47.4%) were identified as being C. coli strains. These data demonstrate that the incidence of macrolide resistance was low but that the macrolide-resistant Campylobacter strains were uniformly multidrug resistant. In addition to the carbapenems, tigecycline was also highly effective against these multidrug-resistant Campylobacter strains in vitro. Its efficacy for the treatment of human campylobacteriosis should be evaluated in clinical trials.

Antibiotic resistance in Campylobacter: emergence, transmission and persistence

Campylobacter is a leading foodborne bacterial pathogen, which causes gastroenteritis in humans. This pathogenic organism is increasingly resistant to antibiotics, especially fluoroquinolones and macrolides, which are the most frequently used antimicrobials for the treatment of campylobacteriosis when clinical therapy is warranted. As a zoonotic pathogen, Campylobacter has a broad animal reservoir and infects humans via contaminated food, water or milk. Antibiotic usage in both animal agriculture and human medicine, can influence the development of antibiotic-resistant Campylobacter. This review will describe the trend in fluoroquinolone and macrolide resistance in Campylobacter, summarize the mechanisms underlying the resistance to various antibiotics and discuss the unique features associated with the emergence, transmission and persistence of antibiotic-resistant Campylobacter. Special attention will be given to recent findings and emphasis will be placed on Campylobacter resistance to fluoroquinolones and macrolides. A future perspective on antibiotic resistance and potential approaches for the control of antibiotic-resistant Campylobacter, will also be discussed.