Table 1.

Activity and morphological effect of classically used antibiotics and proton pump inhibitors on H. pylori.

Compound	H. pylori Strain(s)	Technic Determining Morphology	Technic Determining Viability	Main Results Covering the Morphological Transformation of H. pylori	Authors Interpretation	Bibliography
SUL TAZ CLV AMX AMX + CLV	ATCC 43504	Light microscopy, TEM	Culture	- Viability ↓ <1 log, 6 h, 10× MIC (CLV, SUL, and TAZ) - Coccoid forms with CLV, SUL, and TAZ (6 h, 10× MIC) - Viability ↓ 1 log, 3 h, MIC (AMX, AMX+CLV) - Coccoid forms with AMX and AMX+CLV (3 h, MIC) - Separation of membranes for all antimicrobials (3–6 h, MIC)	Bactericidal activity	[37]
AMX	ATCC 43504	TEM	Culture, Fluorescence (membrane integrity)	- Viability ↓ (3 log, 24 h, MIC) - Coccoid forms (2 h, MIC) - Membrane permeabilization (2 h, MIC)	Bactericidal activity	[38,39] *
CLR TET MTZ AMX	Tx30a	Light microscopy	Culture	- Total viability ↓ for all antibiotics (72 h, MIC) - ≥85% of coccoid forms for all antibiotics (72 h, MIC) - Approx. 30% (¼× MIC) and 70% (½× MIC) of coccoid forms with AMX (72 h) - <15% (¼× MIC) and 25–30% (½× MIC) of coccoid forms with CLR, TET, or MTZ (72 h)	Bactericidal activity, AMX is the strongest inducer of a spiral-to-coccoid form transformation	[40,41] *
AMX MTZ CLR	ATCC 700392	Light microscopy	Flow cytometry (membrane integrity)	- Approx. 30%, 40%, and 95% of coccoid forms with CLR, MTZ, and AMX, respectively (72 h, ½× MIC) - Viability ↓ of coccoid forms by 99.8%, 62.6%, and 0.03% with CLR, MTZ, and AMX, respectively (24 h, 2× MIC)	Bactericidal activity, lower susceptibility of coccoid forms to antibiotics (especially to AMX)	[42]
AMX	SS1	SEM	Culture, Fluorescence (membrane integrity)	- Total viability ↓ of spiral forms (24 h, MIC) - Viability ↓ of coccoid forms only by 20% (24 h, 20× MIC)	Bactericidal activity, coccoid forms are more tolerant to AMX than spiral forms	[43] *
Omeprazole	Clinical isolates	Light microscopy	Culture	- Viability ↓ was directly associated with an amount of coccoid forms - 10%, 40%, and 90% of coccoid forms after 3, 6, and 9 days, respectively (½× MIC) - Viability and spiral shape were recovered after 9–12 days of the omeprazole removal	Inhibitory activity with the reversibility of morphology	[44]

Symbols: decrease (↓), increase (↑). Abbreviations: clavulonate (CLV), sulbactam (SUL), tazobactam (TAZ), amoxicillin (AMX), clarithromycin (CLR), metronidazole (MTZ), tetracycline (TET), proton pump inhibitors (PPIs), scanning electron microscopy (SEM), transmission electron microscopy (TEM), minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC). * In studies marked with asterisks observations regarding antibiotics come from publications primarily focusing on new compounds with a potential anti-H. pylori activity.