Table 2.

Co-occurrence of commensal bacteria and potentially pathogenic microorganisms from the oral cavity among e-cigarette users, smokers of cigarettes and non-smokers

Microorganisms	E-cigarette users n = 40	Smokers of cigarettes n = 43	Non-smokers n = 42	P-value
Commensal bacteria with potentially pathogenic microorganisms:	15/40 (37.5%)a	6/43 (14%)b	13/42 (31%)	< 0.05
Commensal bacteria + S. aureus	2/40	1/43**	5/42
Commensal bacteria + C. albicans	3/40**	2/43	0/42
Commensal bacteria + Streptococcus pyogenes	0/40	1/43**	1/42
Commensal bacteria + E. coli	3/40	1/43	0/42
Commensal bacteria + Enterobacter sp.	2/40**	2/43	1/42
Commensal bacteria + K. oxytoca	1/40	1/43*	0/42
Commensal bacteria + K. pneumoniae	1/40	0/43	0/42
Commensal bacteria + Citrobacter sp.	1/40	0/43	0/42
Commensal bacteria + Providencia sp.	0/40	0/43	1/42
Commensal bacteria + P. aeruginosa	1/40	0/43	1/42
Commensal bacteria + Providencia sp. + P. aeruginosa	1/40	0/43	0/42
Commensal bacteria + Citrobacter sp. + C. albicans	0/40	0/43	1/42
Commensal bacteria + S. aureus + C. albicans	0/40	0/43	1/42**
Commensal bacteria + S. aureus + K. oxytoca	0/40	0/43	1/42
Commensal bacteria + E. coli + P. aeruginosa + C. albicans	0/40	0/43	1/42
Commensal bacteria only	25/40 (62.5%)a	37/43 (86%)b	29/42 (69%)	< 0.05

^*P < 0.05 for a-b (statistical significance), NS – non significant;

Commensal bacteria: Streptococcus viridans group +++, Neisseria sp. ++ (in each sample) and Staphylococci coagulase- negative + (some samples)**.