Infection Control & Hospital Epidemiology


Table 1. General Characteristics of the Study Population Variable


Median age, years (IQR) Age ≤28 d


Female gender Black race


Hispanic ethnicity


Underlying medical conditionsa Prematurity Malignancy


Congenital heart disease Neurologic conditions Short gut


Solid organ transplant End-stage renal disease


Acquisition Community acquired


Community-onset healthcare associated


Nosocomial


Source of bacteremia CLABSI


Endocarditis


Musculoskeletal infection Skin and soft-tissue infection Surgical site infection Urinary tract infection


Bacteremia without a focus Other


57 (23.6) 95 (39.4)


89 (36.9)


105 (43.6) 21 (8.7) 36(14.9) 12 (5) 6 (2.5) 3 (1.2)


41 (17) 18 (7.5)


Note. IQR, interquartile range; CLABSI, central-line–associated bloodstream infection. aMost common underlying conditions listed, categories are not mutually exclusive.


48 (40.3) 33 (27.7)


38 (31.9)


28 (23.5) 16 (13.4) 36 (30.2) 11 (9.2) 5 (4.2) 0


13 (10.9) 10 (8.4)


0 57 (55.3) 46 (44.6)


74 (71.8) 4 (3.9) 0


1 (0.9) 1 (0.9) 1 (0.9)


16 (15.5) 7 (6.7)


9 (47.4) 5 (26.3)


5 (26.3) <.001


3 (15.7) 1 (5.3) 0 0 0


2 (10.5) 12 (63.1) 1 (5.3)


335


Total, No. (%) 1.3 (0.2–7.9) 31 (12.9) 105 (43.5) 45 (18.6) 102 (42.3) 189 (78.4) 43 (17.8) 48 (19.9) 30 (12.4) 9 (3.7)


26 (10.7) 8 (3.3) 4 (1.7)


S. aureus (n=119), No. (%)


3.54 (0.3–11.5) 13 (10.9) 49 (41.2) 20 (16.8) 50 (42)


77 (64.7) 17 (14.3) 12 (10.1) 18 (15.1) 3 (2.5)


10 (8.4) 2 (1.7) 2 (1.7)


CoNS (n=103), No. (%)


0.91 (0.16–7.9) 14 (13.5) 47 (45.6) 22 (21.3) 44 (42.7) 101 (98.1) 24 (23.3) 35 (33.9) 12 (11.6) 2 (1.9)


14 (13.6) 6 (5.8) 2 (1.9)


Enterococcus spp (n=19), No. (%)


0.9 (0.12–5.8) 4 (21.1) 9 (47.4) 3 (15.8) 8 (42.1) 11 (57.8) 2 (10.5) 1 (5.3) 0


4 (21.1) 2 (10.5) 0 0


P Value .01 .40 .76 .67 1


<.001 .17


<.001 .19


.005 .45 .20 1


<.001


were performed with Stata version 15 software (Stata Corp, College Station, TX).


Results


During the study period, 404 viable isolates were obtained from 389 unique patients. Moreover, 254 patients with blood cultures positive for CoNS had complete medical records and 151 of these were considered to be contaminants. After excluding these con- taminants, 103 CoNS, 119 S. aureus, and 19 Enterococcus isolates (totaling 241 unique isolates from 238 patients) were included in final analyses. The median age of studied patients was 1.3 years (interquartile range [IQR], 0.2–7.9 years), and 78.4% of patients had underlying medical conditions (Table 1). Significant differences in age, comorbidities, and diagnoses existed between patients with bacteremia due to CoNS, S. aureus, and enterococci. 7 different CoNS species were identified byMALDI-TOF MS: S.


epidermidis (n = 70), S. hominis (n = 22), S. haemolyticus (n = 4), S. capitis (n = 3), S. warnerii (n = 2), S. lugdenensis (n = 1), and S. saprophyticus (n = 1). Most enterococci were E. faecalis


(n = 16, 84.2%) with the remainder being E. faecium (n = 3). Among S. aureus isolates, 25 of 119 (21%) were methicillin resistant.


Antiseptic tolerance genes


Overall, 83 of 103 CoNS isolates (80.6%) possessed either qacA/B or smr compared to 44 of 119 of S. aureus isolates (37%) and 7 of 16 E. faecalis isolates (43.8%) and none of 3 E. faecium isolates (P < .001) (Fig. 1). The qacA/B gene was detected in 16 of 119 S. aureus isolates (13.4%), 73 of 103 CoNS isolates (70.8%), and 7 of 16 of E. faecalis isolates (43.8%; P < .001). The smr gene was detected in 28 of 119 S. aureus isolates (23.5%), 34 of 103 CoNS isolates (33%), and 4 of 16 E. faecalis isolates (25%; P=.28). Both AT genes were detected in 24 of 103 CoNS isolates (23.3%), 4 of 16 E. faecalis isolates (25%), and none of the S. aureus isolates (P < .001). The proportion of CoNS isolates withAT geneswassimilaramong isolates considered true infec- tions (83 of 103, 80.6%) and contaminants (128 of 151, 84.7%; P = .39). Sequenced qacA/B-and smr-PCR products obtained


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