Bulgecin A as a β-lactam enhancer for carbapenem-resistant Pseudomonas aeruginosa and carbapenem-resistant Acinetobacter baumannii clinical isolates containing various resistance mechanisms

Figures & data

Figure 1 Bulgecin A.

Table 1 MIC (mg/L) results for clinical strains

Strain	Aztreonam	Meropenem	Imipenem	Amp/sulb	PCR
ACB UH83 (OXA-24)	>128	>32	>32	S (Microscan)	+OXA-24
ACB UH10 (TEM-1)	n/a	1	1	R (Microscan)	−OXA-24, +TEM
PSDA CL231 (PDC-5)	n.d.	16	16	n/a	−OXA-24, −VIM −KPC, −PAβN
PSDA R96 (VIM-2)	32	128 128 with PAβN	256	n/a	+VIM, −OXA, −KPC, −PAβN, inhibition
PSDA VA efflux + strain 860 (this study)	64	16 1 with PAβN	4	n/a	−VIM, OXA, KPC, +PAβN inhibition

Abbreviations: Amp/sulb, ampicillin/sulbactam; ACB, Acinetobacter baumannii; MIC, minimum inhibitory concentration; PAβN, Phe-Argβ-naphthylamide; PCR, polymerase chain reaction; PSDA, Pseudomonas aeruginosa; n/a, not applicable; n.d., not determined.

Figure 2 Growth curves of ACB clinical strains with antibiotics and BlgA extract.

Notes: (A) Escherichia coli MC1061 positive control with inoculum 1 µL of a 1:10 dilution of overnight culture with 0.01 mg/L aztreonam and 10% BlgA extract. (B) Growth curves of MDR Acinetobacter baumannii strain UH83 with inoculum 1 µL of a 1:10 dilution of overnight culture (OD_{600 nm} vs time in minutes). Diamonds (top curve), no antibiotics; squares, 0.02 mg/L meropenem alone; triangles, 10% bulgecin extract alone; circles (bottom curve), 10% bulgecin extract with 0.02 mg/L meropenem (three determinations ±5% error). (C) Growth curves of A. baumannii strain UH10 with inoculum 1 µL of a 1:10 dilution of overnight culture (OD_{600 nm} vs time in minutes). Diamonds (top curve), no antibiotics; squares, 0.03 mg/L ampicillin/0.15 mg/L sulbactam alone; triangles, 10% bulgecin extract alone; circles (bottom curve), 10% bulgecin extract with 0.03 mg/L ampicillin/0.15 mg/L sulbactam (three determinations ±5% error).

Figure 3 Growth curves of PSDA clinical strains with antibiotics and BlgA extract.

Notes: (A) Growth curves of CR-PSDA strain CL-231 PDC-5 hyperproducing strain 1 µL of 1:1 overnight culture inoculum (OD_{600 nm} vs time in minutes). Diamonds (top curve), no antibiotics; squares, 0.03 mg/L meropenem alone; triangles, 10% bulgecin extract alone; circles (bottom curve), 10% bulgecin extract with 0.03 mg/L meropenem (three determinations ±5% error). (B) Growth curves of CR-PSDA strain 860 efflux strain 1 µL of 1:2 overnight culture inoculum (OD_{600 nm} vs time in minutes). Diamonds (top curve), no antibiotics; squares, 0.03 mg/L meropenem alone; triangles, 10% bulgecin extract alone; circles (bottom curve), 10% bulgecin extract with 0.03 mg/L meropenem (three determinations ±5% error). (C) Growth curves of CR-PSDA strain 860 efflux strain 1 µL of 1:10 overnight culture inoculum (OD_{600 nm} vs time in minutes). Diamonds (top curve), no antibiotics; squares, 0.03 mg/L meropenem alone; triangles, 10% bulgecin extract alone; circles (bottom curve), 10% bulgecin extract with 0.03 mg/L meropenem (three determinations ±5% error). (D) CR-PSDA strain R96 VIM-2 producer 1 µL of 1:10 overnight culture inoculum (OD_{600 nm} vs time in minutes). Diamonds (top curve), no antibiotics; squares, 0.03 mg/L meropenem alone; triangles, 10% bulgecin extract alone; circles (bottom curve), 10% bulgecin extract with 0.03 mg/L meropenem (three determinations ±5% error).
Abbreviation: CR-PSDA, carbapenem-resistant Pseudomonas aeruginosa.

Figure 4 IC₅₀ expressed as percent concentration of bulgecin A extract to inhibit VIM-2 β-lactamase hydrolysis activity.