Effects of sub-inhibitory concentrations of meropenem and tigecycline on the expression of genes regulating pili, efflux pumps and virulence factors involved in biofilm formation by Acinetobacter baumannii

Figures & data

Table 1 Primers used in this study

Gene	Primer 5' to 3’	Ref.
abaI	F-CCGCCTTCCTCTAGCAGTCA R- AAAACCCGCAGCACGTAATAA	^Citation4
pgaA	F- GCCGACGGTCGCGATA C R-ATGCACATCACCAAAACGGTACT	^Citation4
csuE	F- TCAGACCGGAGAAAAACTTAACG R- GCCGGAAGCCGTAT GTAGAA	^Citation4
bap	F- AATGCACCGGTACTTGATCC R- TATTGC CTGCAGGGTCAGTT	^Citation4
16SrRNA	F-ACTCCTACGGGAGGCAGCAGT R-TATTACCG CGGCTGCTGGC	^Citation4
bfmS	F- ACCGCCCGTAATCCGAAC R- TGAACTTATTCCACCGCCTTTA	^Citation5
bfmR	F- GTTTAACCGTTTGTCGTG R- GTGGTTGAACTGGTTTCG	^Citation5
adeB	F-CTTGCATTTACGTGTGGTGT R-GCTTTTCTACTGCACCCAAA	^Citation23
adeJ	F- GGTCATTAATATCTTTGGC R- GGTACGAATACCGCTGTCA	^Citation23
adeG	F- TTCATCTAGCCAAGCAGAAG R- GTGTAGTGCCACTGGTTACT	^Citation23
abaR	F- ACCTCTTGTTTGGTCGAGTCA R- CGTGCTTCCTCCCAAAAAT	^Citation24

Table 2 Antibiotic susceptibility of strains in planktonic and biofilm mode

Strain	Meropenem		Amikacin		Tigecycline		Levofloxacin		Cefepime
	MIC	MBEC	MIC	MBEC	MIC	MBEC	MIC	MBEC	MIC	MBEC
AB10	128	2048	64	1024	4	128	4	256	16	256
AB13	64	512	128	2048	2	64	64	1024	256	4096
AB32	512	4096	512	8192	16	512	64	512	128	1024
AB55	2	256	32	512	4	256	4	128	8	128

Abbreviations: MIC, minimum inhibitory concentration; MBEC, minimum biofilm eradication concentration.

Figure 1 Biofilm formation by A. baumannii strains in the presence of sub-MICs of tigecycline and meropenem. Error bars represent the standard deviations; *significant difference at a P-value of 0.05. REF: A. baumannii 19606.

Abbreviations: A. baumannii, Acinetobacter baumannii; MIC, minimum inhibitory concentration; REF, reference srain.

Figure 2 Effect of tigecycline at sub-MICs on the expression levels of the efflux pumps, pili regulation and biofilm involved genes in A. baumannii strains. Error bars represent the standard deviations; *significant difference at a P-value of 0.05.

Abbreviations: A. baumannii, Acinetobacter baumannii; MIC, minimum inhibitory concentration.

Figure 3 Effect of meropenem at sub-MICs on the expression levels of the efflux pumps, pili regulation and biofilm involved genes in A. baumannii strains. Error bars represent the standard deviations; *significant difference at a P-value of 0.05.

Abbreviations: A. baumannii, Acinetobacter baumannii; MIC, minimum inhibitory concentration.

Table 3 Association between biofilm formation and the gene expression profiles of A. baumannii strains at sub-MICs of tigecycline

Strain	bap	ompA	csuE	pgaA	abaI	abaR	bfmS	bfmR	adeB	adeJ	adeG
AB10	0.965*	0.886*	0.963*	0.990*	0.974*	0.990*	0.957*	0.911*	0.962*	0.382	0.938*
AB13	0.997*	0.506	0.906*	0.971*	0.994*	0.988*	0.936*	0.950*	0.994*	0.448	0.887*
AB32	0.957*	0.522	0.962*	0.997*	0.937*	0.983*	0.974*	0.965*	0.963*	0.523	0.883*
AB55	0.897*	0.484	0.224	0.992*	0.897*	0.932*	0.270	0.231	0.997*	0.302	0.512

Note: *Significant P-value at the level of 0.05.

Abbreviation: MIC, minimum inhibitory concentration.

Table 4 Association between biofilm formation and the gene expression profiles of A. baumannii strains at sub-MICs of meropenem

Strain	bap	ompA	csuE	pgaA	abaI	abaR	bfmS	bfmR	adeB	adeJ	adeG
AB10	0.975*	0.989*	0.770*	0.976*	0.911*	0.887*	0.977*	0.953*	0.764*	0.033	0.943*
AB 13	0.994*	0.116	0.990*	0.049	0.974*	0.998*	0.964*	0.978*	0.992*	0.516	0.984*
AB 32	0.989*	0.834*	0.977*	0.983*	0.978*	0.980*	0.964*	0.987*	0.924*	0.083	0.957*
AB 55	0.986*	0.902*	0.789*	0.836*	0.891*	0.932*	0.892*	0.872*	0.924*	0.259	0.990*
ATCC19606

Note: *Significant P-value at the level of 0.05 (2-tailed).

Abbreviations: A. baumannii, Acinetobacter baumannii; MIC, minimum inhibitory concentration..

Table 5 Association between Quorum sensing with the gene expression profiles of A. baumannii strains at sub-MICs of tigecycline

Strain	bap	ompA	csuE	pgaA	abaR	bfmS	bfmR	adeB	adeJ	adeG
AB 10	0.884*	0.955*	0.943*	0.937*	0.981*	0.888*	0.814*	0.877*	0.440	0.938*
AB 13	0.991*	0.497	0.943*	0.981*	0.984*	0.957*	0.959*	0.985*	0.416	0.907*
AB 32	0.946*	0.247	0.983*	0.951*	0.975*	0.978*	0.979*	0.953*	0.248	0.975*
AB 55	0.998*	-0.444	0.212	0.929*	0.982*	-0.445	0.259	0.891*	0.339	0.465
ATCC19606

Note: *Significant P-value at the level of 0.05 (2-tailed).

Abbreviations: A. baumannii, Acinetobacter baumannii; MIC, minimum inhibitory concentration.

Table 6 Association between Quorum sensing and the gene expression profiles of A. baumannii strains at sub-MICs of meropenem

Strain	bap	ompA	csuE	pgaA	abaR	bfmS	bfmR	adeB	adeJ	adeG
AB 10	0.911*	0.956*	0.974*	0.856*	0.998*	0.947*	0.993*	0.905*	-0.142	0.971*
AB 13	0.979*	-0.002	0.991*	-0.050	0.970*	0.997*	0.996*	0.988*	0.476	0.992*
AB 32	0.974*	0.831*	0.998*	0.935*	0.998*	0.916*	0.998*	0.930*	0.754*	0.993*
AB 55	0.953*	0.969*	0.993*	0.940*	0.993*	0.995*	0.995*	0.996*	-0.098	0.891*
ATCC19606

Note: *Significant P-value at the level of 0.05 (2-tailed).

Abbreviations: A. baumannii, Acinetobacter baumannii; MIC, minimum inhibitory concentration.

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