Carbapenem-Resistant Gram-Negative Bacilli Causing Ventilator Associated Pneumonia: Study of MASTDISCS Combi Carba Plus for Detection of Carbapenemase Producing Enterobacterales

Figures & data

Table 1 Demographic and Clinical Data of Studied Patients

Variable	Median (IQR)/N (%)
Age (years)	47(32–63)
Sex
Male	51(61.4)
Female	32(38.6)
Comorbidities
Trauma	24(28.9)
Diabetes mellitus	10(12)
Liver failure	6(7.2)
Renal failure	11(13.3)
Cancer	11(13.3)
Ischemic insult	15(18.1)
Chest disease	6(7.2)
Days of hospitalization	14(10–20)
Days of ventilation	10(7–13)
Outcome
Death	25(30.1)
Survival	58(69.9)

Table 2 Genotypic Detection of Carbapenemase Genes in Carbapenem-Resistant Gram-Negative Bacilli

Organism		PCR
	Total	blaKPC +ve	blaNDM +ve	blaOXA-48+ve	blaKPC + blaNDM +ve	blaKPC+blaOXA-48 (+ve)	blaNDM + blaOXA- 48 (+ve)	Negative for All Genes
	N (%)
Klebsiella pneumoniae	29 (34.9)	11 (37.9)	6(20.7)	6(20.7)	2(6.9)	2(6.9)	–	2(6.9)
Klebsiella oxytoca	3 (3.6)	2(66.7)	1(33.3)	–	–	–	–	–
Pseudomonas aeruginosa	15 (18.1)	1(6.7)	5(33.3)	4(26.7)	4(26.7)	–	–	1(6.7)
Acinetobacter baumannii	17 (20.5)	4(23.5)	5(29.4)	4(23.5)	–	–	2(11.8)	2(11.8)
E. coli	10 (12)	6(60)	2(20)	2(20)	–	–	–	–
Proteus mirabilis	3(3.6)	–	2(66.7)	1(33.3)	–	–	–	–
Serratia marcescens	2(2.4)	–	2(100)	–	–	–	–	–
Enterobacter cloacae	3(3.6)	2(66.7)	1(33.3)	–	–	–	–	–
Enterobacter aerogenes	1(1.2)	1(100)	–	–	–	–	–	–
Total	83	27 (32.5)	24(28.9)	17(20.5)	6(7.2)	2(2.4)	2(2.4)	5(6)

Figure 1 Agarose gel electrophoresis of bla_KPC, bla_NDM, and bla_OXA-48 carbapenemase genes amplicons. DNA ladder 100 bp in lane 1. (A) Lanes (2, 3, 4 and 5) positive for bla_KPC gene (798bp). (B) Lanes (3, 4, and 6) positive for bla_NDM gene (621bp). (C) lanes (5, 6): positive for bla_OXA-48 gene (438 bp).

Abbreviations: DNA, deoxyribonucleic acid; bp, base pair.

Table 3 MASTDISCS Combi Carba Plus Disc System Results in Carbapenem-Resistant Gram-Negative Bacilli

Organism		Carba Test
	Total	KPC+ve	MBL+ve	OXA-48+ve	Negative	Not Tested
	N (%)
Klebsiella pneumoniae	29 (34.9)	10(34.5)	10(34.5)	7(24.1)	2(6.9)	–
Klebsiella oxytoca	3 (3.6)	1(33.3)	1(33.3)	1(33.3)	–	–
Pseudomonas aeruginosa	15 (18.1)	–	–	–	–	15(100)
Acinetobacter baumannii	17 (20.5)	–	–	–	–	17(100)
E. coli	10 (12)	3(30)	4(40)	2(20)	1(10)	–
Proteus mirabilis	3 (3.6)	–	2(66.7)	1(33.3)	–	–
Serratia marcescens	2(2.4)	–	1(50)	–	1(50)	–
Enterobacter cloacae	3 (3.6)	2(66.7)	1(33.3)	–	–	–
Enterobacter aerogenes	1 (1.2)	–	–	1(100)	–	–
Total	83	16(19.3)	19(22.9)	12(14.5)	4(4.8)	32(38.6)

Figure 2 Positive results of MAST-Carba plus assay .(A) KPC positive, the diameter difference between disc C and disc A was ≥5 mm and <5 mm difference between disc B or disc D and disc A. (B) MBL positive, the diameter difference between disc B and disc A was ≥5 mm and <5 mm difference between disc C or disc D and disc A. (C) OXA-48 positive, the zone of inhibition around disc E was ≤10 mm with no synergy between discs A–D.

Table 4 Sensitivity, Specificity, Positive and Negative Predictive Values of MASTDISCS Combi Carba Plus Disc System in Comparison to PCR

	PCR (KPC, MBL, OXA-48		Sensitivity (%)	Specificity (%)	PPV (%)	NPV (%)
KPC	Positive	Negative
Positive	12	4	46.2	84	75	60
Negative	14	21
MBL
Positive	11	8	68.8	77.1	57.9	84.4
Negative	5	27
OXA-48
Positive	9	3	81.8	92.5	75	94.9
Negative	2	37

Table 5 Univariate Cox Proportional Hazards Regression of the Association Between Demographic and Clinical Variables with Respect to Overall Survival

Variable	Hazard Ratio (95% CI)	P-value*
Klebsiella pneumonia	0.9(0.4–2.1)	0.9
Pseudomonas aeruginosa	3.4(1.3–8.8)	0.006
Acinetobacter baumannii	1.2(0.5–2.8)	0.7
Positive PCR-KPC	0.95(0.4–2.1)	0.9
Positive PCR-MBL	1.6(0.7–3.6)	0.3
Positive PCR-OXA	1.5(0.7–3.2)	0.4
Ventilation days (<15 days)	3.9(1.4–10.7)	0.008
Age (≥50)	1.4(0.6–3)	0.4
Sex (Female)	2.01(0.9–4.7)	0.09

Note: *log rank test.