Absence of class 1 and class 2 integrons among Campylobacter jejuni and Campylobacter coli isolated from poultry in Italy.

in the GenBank non-redundant DNA database was examined. Two additional cases of ISAba1 associated with distinct ampC alleles were found in accession numbers EU604835 8 and AY325306. 3 In both of them, the IS was again in the same orientation and separated from the ATG initiation codon of ampC by 9 bp. The number of single nucleotide differences between the various ampC alleles is shown in Table 1. Two ceftazidime and cefotaxime resistant isolates in our collection that did not belong to GC1 or GC2 were found to carry ISAba1 upstream of ampC, and these were also sequenced. D46 isolated in 2010 in Sydney, Australia was ST110 (Oxford scheme) and RBH2 isolated in 1999 in Brisbane, Australia was ST125 (Oxford scheme). Each contained a distinct ampC allele (Table 1) and ISAba1 was again appropriately oriented and 9 bp away from the ampC initiation codon (GenBank accession numbers KF030679 and KF030678). The simplest explanation for the finding that ISAba1 was found in the same position and orientation relative to six different ampC alleles is that ISAba1 has repeatedly inserted at exactly the same position. Additional support for this conclusion comes from an examination of the sequences of ISAba1. A total of 10 single nucleotide polymorphisms, most of them near the ends of the IS, were found in various combinations when the six ISAba1 sequences were compared, and this suggests that different IS variants were inserted. The currently unexplained site specificity could contribute to the importance of this mechanism of resistance to third-generation cephalosporins. A detailed examination of the location of ISAba1 upstream of the intrinsic oxa-Ab gene, which it also activates, may shed further light on this issue. 5 Nigro SJ, Post V, Hall RM. Aminoglycoside resistance in multiply antibiotic-resistant Acinetobacter baumannii belonging to global clone 2 from Australian hospitals. 6 Mak JK, Kim MJ, Pham J et al. Antibiotic resistance determinants in nosocomial strains of multidrug-resistant Acinetobacter baumannii. 7 Hamidian M, Hall RM. AbaR4 replaces AbaR3 in a carbapenem resistant Acinetobacter baumannii isolate belonging to global clone 1 from an Australian hospital. 8 Lee HY, Chen CL, Wang SB et al. Imipenem heteroresistance induced by imipenem in multidrug-resistant Acinetobacter baumannii: mechanism and clinical implications. 9 Hamidian M, Hancock DP, Hall RM. Horizontal transfer of an ISAba125-activated ampC gene between Acinetobacter baumannii strains leading to cephalosporin resistance. Sir, Since their discovery in the late 1980s, integrons have been revealed to play …