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. 2022 Dec 2;13:1071278. doi: 10.3389/fmicb.2022.1071278

FIGURE 6.

FIGURE 6

Glutamine promotes gentamicin-mediated killing. (A) Percent survival of K12-RGEN in the presence of the indicated concentration of glutamine and 10 μg gentamicin. (B) Percent survival of K12-RGEN in the presence of the indicated concentration of gentamicin and with or without 20 mM glutamine. (C) Percent survival of K12-RGEN in the indicated incubation time plus 20 mM glutamine and 10 μg gentamicin. The concentration of K12-RGEN in (A–C) was 5 × 108 CFU/ml. (D) MIC measurement of clinically isolated bacterial strains in four to six kinds of antibiotics commonly used in clinical practice. Purple indicates resistant; orange indicates intermediate; dark gray indicates susceptible. For AMX, CRO, FOX, CFP, CAZ, MEM, GEN, CIP, TET, CLDM, PMB, LVFX, CZ, CT, TOB, CAP, and ROX, the standard was according to reference (CLSI, 2012). For ATM, OFX, and AK, the standard was according to reference (Kahlmeter et al., 2006). For MXF and BLFX, susceptible, intermediate, and resistant E. coli were defined as MIC ≤ 0.025, MIC = 0.05, and MIC ≥ 0.1 and MIC ≤ 0.05, MIC = 0.1, and MIC ≥ 0.2, respectively. (E) Percent survival of clinically isolated strains in the presence or absence of gentamicin (Y1 at 2 μg/ml; Y4, Y7 at 2.5 μg/ml; Y22 at 100 μg/ml; K. pneumoniae KPN48 (2 μg/ml); E. tarda EIB202 (2 μg/ml); P. aeruginosa PA41 (1 μg/ml), or in the presence of both gentamicin and 20 mM glutamine. (F) Percent survival of K12-RGEN in the indicated antibiotics (SCF, 10 μg/ml; OFX, 1.5 μg/ml; TOB, 2.5 μg/ml; FFC, 40 μg/ml) with and without 20 mM glutamine. The concentration of clinically isolated strains in (E) and K12-RGEN in (F) was 1 × 106 CFU/ml. Amoxicillin (AMX), Ceftriaxone (CRO), Cefoxitin (FOX), Cefoperazone (CFP), Cefoperazone-sulbactam (SCF), Ceftazidime (CAZ), Aztreonam (ATM), Meropenem (MEM), Gentamicin (GEN), Amikacin (AK), Ciprofloxacin (CIP), Moxifloxacin (MXF), Balofloxacin (BLFX), Ofloxacin (OFX), Tetracycline (TET), Clindamycin (CLDM), Polymyxin B (PMB), Levofloxacin (LVFX), Cefazolin (CZ), Colistin (CT), Tobramycin (TOB), Chloramphenicol (CAP), Roxithromycin (ROX), Florfenicol (FFC). Results are displayed as mean ± SEM and three biological repeats are performed. Significant differences are identified. **p < 0.01.