H. cinaedi strains generally show low MIC values for carbapenems, aminoglycosides, and tetracycline (MIC90 ≦1 μg/ml for imipenem, gentamicin, and tetracycline). Penicillins and cephalosporins show moderate MIC values (MIC90 = 16 μg/ml for ampicillin, and carbenicillin, MIC90 = 8 μg/ml for amoxicillin, cefepime, and ceftriaxone). In contrast, H. cinaedi, which has well known resistance to macrolides [57] and [73], has

particularly high MIC values (MIC90 > 64 μg/ml for erythromycin). Although there are some reports from before the current decade describing Epigenetics Compound Library supplier susceptibility to quinolones [18], [21], [22], [57] and [74], more recently in Japan and elsewhere H. cinaedi isolates have shown high resistance to quinolones (MIC90 = 64 μg/ml for ciprofloxacin and levofloxacin) due to point mutation(s) of DNA gyrase genes. Almost the same MIC values are reported by other researchers [75]. MIC values Selleckchem STA-9090 of recent isolates from several hospitals in Japan are summarized in Table 3. It is well known that efflux pumps contribute to antimicrobial resistance in many cases. The resistance nodulation cell division (RND) type multidrug efflux transporters are the clinically relevant chromosomally encoded fundamental antimicrobial resistance

mechanisms in Gram-negative bacteria [76]. We identified two genes (locus-tags HCN_0595 and HCN_1563) in the chromosome of H. cinaedi PAGU 611 encoding the hydrophobe/amphiphile efflux-1 sub-family of the RND family [43] and [77]. The genes were also conserved in other H. cinaedi genomic strains of CCUG 18818 and ATCC BAA-847 [48]. HCN_0595 orthologs are found in various species among the genus Helicobacter (e.g. H. pylori 26695 and H. hepaticus

ATCC 51449), while HCN_1563 orthologs are found only in enterohepatic Helicobacter species (e.g. H. hepaticus ATCC 51449) examined. A phylogenetic tree was constructed using COBALT software ( Fig. 6) [78]. HCN_1563 pump is between CmeB of C. jejuni and BepE pump of Brucella suis, both of which are major antimicrobial resistance contributors, while HCN_0595 pump is between HefC of H. pylori and CmeF of C. jejuni, both of which are likely to be small or secondary contributors. The CmeABC pump contributes to the acquired resistance of C. jejuni to macrolides and fluoroquinolones [79] and [80]; HCN_1563 pump of H. cinaedi may be associated with resistance to these drugs. for Another eight putative drug transporter genes (one belonging to the major facilitator family, one to the ATP-binding cassette family, two to the multidrug and toxin extrusion family, and four to the small multidrug resistance family) are found in the genome of H. cinaedi PAGU 611. The orthologs are also encoded in H. cinaedi ATCC BAA-847 and H. hepaticus ATCC 51449 [77]. It is not clear how the gene products operate and how they contribute to antimicrobial resistance, and further investigation is needed. Various antibiotic agents alone or in combination have been successfully used for treating infections caused by H.