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Gene Review:

AAC(6')-Ib - AAC(6')-Ib

Escherichia coli

Dery, K.J. et al., Rather, P.N. et al., García, D.C. et al., Sarno, R. et al., Ploy, M.C. et al., et al.

Ploy, Denis, Courvalin, Lambert,

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Disease relevance of AAC(6')-Ib

After their introduction into an Escherichia coli strain harboring aac(6')-Ib by electroporation, some of these oligodeoxynucleotides decreased the level of resistance to amikacin [1].
A gene different from aac(6')-Ia, aac(6')-Ib and aac(6')-Ic encoding the AAC(6')-I activity was found in a 15.5-kb plasmid in Acinetobacter spp [2].
Plasmids from 27 Enterobacteriaceae contained and aac(6')-Ib gene and 26 of these carried sequences related to the Tn1331 transposon, whereas one Escherichia coli plasmid showed homology in another fragment of the Tn1331 transposase [2].

High impact information on AAC(6')-Ib

Since there were three possible translation initiation sites, the amino acid sequence at the N terminus of the aminoglycoside 6'-N-acetyltransferase type Ib [AAC(6')-Ib] was determined and was found to be SIQHF [3].
The aminoglycoside 6'-N-acetyltransferase type Ib, which is coded for by the aac(6')-Ib gene, mediates resistance to amikacin and other aminoglycosides [1].
The nucleotide sequence of aac(6')-Ib includes a region identical to that of the bla(TEM-1) gene [3].
Extraction of the periplasmic proteins of E. coli harboring aac(6')-Ib by spheroplast formation showed that most of the AAC(6')-Ib protein is present in the cytoplasm [3].
Thirteen strains had integrons with a single cassette: aac(3)-Ia (9 strains), ant(2")-Ia (2 strains), or aac(6')-Ib (2 strains); 1 had aac(6')-Ib and oxa20 cassettes and an unknown gene; and 1 had an integron containing ant(2")-Ia and an oxa3 cassette truncated by IS6100 [4].

Biological context of AAC(6')-Ib

This change resulted in the conversion of the AAC(6')-IIa substrate specificity to that of AAC(6')-Ib [5].
Analysis of additional amino acid substitutions within this region of AAC(6')-Ib support the model that we have identified an aminoglycoside binding domain of these proteins [5].
The oxa19 gene was found to be inserted, in a typical integron structure, immediately downstream from an aac(6')-Ib gene coding for an aminoglycoside acetyltransferase variant, which was called AAC(6')-Ib9 [6].
Sequencing of plasmids isolated from the transformants identified sul1, aac(6')-Ib and bla(CTX-M-2) [7].

Associations of AAC(6')-Ib with chemical compounds

An AAC(6')-Ib protein (encoded by the aacA4 gene; G. Tran Van Nhieu and E. Collatz, J. Bacteriol. 169:5708-5714, 1987) that results in resistance to amikacin but not gentamicin was found to share 82% sequence similarity with the AAC(6')-II protein [8].
Mutations shifting the specificity of the AAC(6')-Ib protein to that of the AAC(6')-IIa protein (i.e., gentamicin resistance and amikacin sensitivity) have been isolated [5].
These nine antimicrobial resistance mechanisms comprised two extended-spectrum beta-lactamases (ESBLs) (PER-2 and CTX-M-2), TEM-1-like, OXA-9-like, AAC(3)-IIa, AAC(6')-Ib, ANT(3")-Ia and resistance determinants to tetracycline and chloramphenicol [9].

References

Inhibition of aminoglycoside 6'-N-acetyltransferase type Ib-mediated amikacin resistance by antisense oligodeoxynucleotides. Sarno, R., Ha, H., Weinsetel, N., Tolmasky, M.E. Antimicrob. Agents Chemother. (2003) [Pubmed]
An 8-year study of resistance to amikacin in gram-negative bacilli isolates from patients with nosocomial infection at one hospital in Argentina. García, D.C., Woloj, G.M., Piñeiro, S., Sordelli, D.O., Kaufman, S. J. Med. Microbiol. (1995) [Pubmed]
The aminoglycoside 6'-N-acetyltransferase type Ib encoded by Tn1331 is evenly distributed within the cell's cytoplasm. Dery, K.J., Søballe, B., Witherspoon, M.S., Bui, D., Koch, R., Sherratt, D.J., Tolmasky, M.E. Antimicrob. Agents Chemother. (2003) [Pubmed]
Molecular characterization of integrons in Acinetobacter baumannii: description of a hybrid class 2 integron. Ploy, M.C., Denis, F., Courvalin, P., Lambert, T. Antimicrob. Agents Chemother. (2000) [Pubmed]
Genetic analysis of bacterial acetyltransferases: identification of amino acids determining the specificities of the aminoglycoside 6'-N-acetyltransferase Ib and IIa proteins. Rather, P.N., Munayyer, H., Mann, P.A., Hare, R.S., Miller, G.H., Shaw, K.J. J. Bacteriol. (1992) [Pubmed]
Novel OXA-10-derived extended-spectrum beta-lactamases selected in vivo or in vitro. Mugnier, P., Casin, I., Bouthors, A.T., Collatz, E. Antimicrob. Agents Chemother. (1998) [Pubmed]
Integron-mediated ESBL resistance in rare serotypes of Escherichia coli causing infections in an elderly population of Israel. Sompolinsky, D., Nitzan, Y., Tetry, S., Wolk, M., Vulikh, I., Kerrn, M.B., Sandvang, D., Hershkovits, G., Katcoff, D.J. J. Antimicrob. Chemother. (2005) [Pubmed]
Isolation, characterization, and DNA sequence analysis of an AAC(6')-II gene from Pseudomonas aeruginosa. Shaw, K.J., Cramer, C.A., Rizzo, M., Mierzwa, R., Gewain, K., Miller, G.H., Hare, R.S. Antimicrob. Agents Chemother. (1989) [Pubmed]
Multiple antibiotic-resistance mechanisms including a novel combination of extended-spectrum beta-lactamases in a Klebsiella pneumoniae clinical strain isolated in Argentina. Melano, R., Corso, A., Petroni, A., Centrón, D., Orman, B., Pereyra, A., Moreno, N., Galas, M. J. Antimicrob. Chemother. (2003) [Pubmed]

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