Table 2 Discriminatory volatile metabolites of the pan metabolome (excluding core metabolites).

Putative Identification	Class	RI	Match Score	Variable Importance Rank				Species	DA^‡
Putative Identification	Class	RI	Match Score	RF	Linear SVM	PLS-DA	Overall	Species	DA^‡
*More abundant in CPE cultures*
2,3,3-trimethylpentane	CH	738	934	210	342	32	194.6	Kp	***
Unknown hydrocarbon	CH	843	—	215	361	38	204.4	Kp	***
Unknown hydrocarbon	CH	875	—	207	236	37	160.1	Kp	***
Unknown benzene derivative	BEN	1055	—	208	284	36	175.9	Kp	***
Unknown hydrocarbon	CH	1510	—	213	331	31	191.5	Kp	***
Unknown hydrocarbon	CH	1516	—	210	333	32	191.6	Kp	***
Unknown hydrocarbon	CH	1555	—	212	347	36	198.2	Kp	***
Unknown ester	EST	1081	—	9	13	7	9.7	Kp, Eco	33.79
Unknown hydrocarbon	CH	994	—	9	20	6	11.5	Kp, Eco	24.80
Unknown hydrocarbon	CH	859	—	52	208	15	91.5	Kp	20.63
4-methyloctane	CH	865	900	26	587	20	210.9	Kp, Eco	14.12
Unknown hydrocarbon	CH	819	—	89	181	24	98.0	Kp	8.58
Unknown ester	EST	747	—	33	135	40	69.3	Kp	6.18
Unknown hydrocarbon	CH	1222	—	302	69	190	186.9	Ecl	5.83
Unknown 4-ketone	KET	1013	892	237	68	218	174.1	Kp, Eco	1.78
Unknown alcohol	ALC	815	—	239	90	189	172.3	Ecl	1.26
*More abundant in non-CPE cultures*
Octanal	ALD	1046	—	21	220	134	125.1	Kp, Eco	0.80
Hexanal	ALD	839	836	16	108	21	48.3	Kp, Eco	0.62
Unknown alcohol	ALC	1116	—	43	186	52	93.6	Kp, Eco	0.56
Unknown S-containing	S-C	1048	—	224	102	397	241.1	Eco	0.25
Unknown N-containing	N-C	911	—	11	34	3	16.0	Kp	0.18
Ethylcyclohexane	CH	844	835	28	24	20	23.9	Kp, Eco	0.05
Unknown N-containing	N-C	989	—	37	49	9	31.3	Kp	0.00
Unknown alcohol	ALC	1196	—	260	72	132	154.9	Ecl	0.00

RI: Experimentally-determined retention index; DA: Differential abundance (average compound abundance in CPE cultures divided by average compound abundance in non-CPE cultures); ALC: alcohol; ALD: aldehyde; BEN: benzene derivative; CH: hydrocarbon; EST: ester; KET: ketone; N-C: nitrogen-containing; S-C: sulfur-containing;—: Match score not provided for compounds without putative identifications; Kp: K. pneumoniae; Eco: E. coli; Ecl: E. cloacae; ^‡calculated using only the species observed to produce the metabolite; ***Not detected in non CPE cultures. Bolded feature ranks indicate that the metabolite was included amongst the top 20% most highly discriminatory metabolites for that algorithm.

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