1228 infection control & hospital epidemiology october 2017, vol. 38, no. 10


table 1. Culture-Confirmed S. aureus (MRSA and MSSA) Infections in Adults and Children, Stratified by Site of Care and Demographic Characteristics, University of Chicago Medicine, January 2006 through March 2014 (n=10,889)


Adults (n=7,226), No. (%) MRSA Inpatient


Outpatient ED


Total MRSAb MSSA Inpatient


Outpatient ED


Total MSSAc


Insurance Type Public Private


Sex


Uninsured, unknown Female


Male


Age, y 0–2 3–5


5–17


18–44 45–65 65+


1,878 (26.0) 1,574 (21.8) 401 (5.5)


3,853 (53.3) 5,087 (72.1)


1,490 (21.1) 649 (9.0)


3,679 (50.9) 3,547 (49.1)


… … …


2,651 (36.7) 2,847 (39.4) 1,728 (23.9)


resistant Staphylococcus aureus; N/A not applicable. aComparing adults and children. bNo encounter type recorded for 28 MRSA isolates. cNo encounter type recorded for 45 MSSA isolates.


to assess for colonization. The distribution among adults and children and demographic characteristics of patients are shown in Table 1. Adult MRSA and MSSA infections more often occurred in the inpatient setting than did those in children. Children were more likely to have public insurance than adults. Approximately 41% of children with S. aureus infections were <2 years of age (Table 1).


Clinical Syndromes


The most common clinical syndrome caused by MRSA and MSSA in both adults and children was SSTI in 2006–2014. 86.6% of children and 62.2% of adults with MRSA infections had SSTIs, while 66.6% of children and 51.5% of adults with MSSA infections had SSTIs. The next most common clinical syndrome was respiratory, accounting for 13.9% and 8.2% of S. aureus infections in adults and children, respectively (Table 2).


Total MRSA and MSSA Incidence


For children and adults combined in 2006–2013, the cumu- lative incidence of MRSA infections declined by an average of


5.2% per year (P<.001), and MSSA infections did not change significantly overall (Figure 1a). Among children, all MRSA infections decreased on average by 10.5% per year (P<.001). Adult MRSA infections decreased to a lesser extent (−4.5% on average per year; P<.001) (Figure 1b). In contrast to MRSA, the change in MSSA cumulative incidence was quite different in children and adults. For adults in all care settings combined, MSSA infections increased by an average of 1.9% per year (P=.007) while for children they decreased by an average of 5.1% per year (P<.001). There was also a significant decline in CAMRSA as a percent


of all MRSA by year (−2.8% on average per year; P<.001) (Figure 1c).


Staphylococcus aureus SSTIs


In children, a significant decrease in S. aureus SSTI cumulative incidence was observed in 2006–2013 (−6.8% peryearonaver- age, P<.001). In contrast, no significant change was observed in adults. Whenexaminedbysiteof careat UCM,a significant decrease in outpatient (−7.4%; P=.01), inpatient (−4.3%;


577 (15.8) 457 (12.5) 466 (12.7) 1,500 (40.2)


<.001


2,958 (83.6) 461 (13.0) 244 (6.7)


.713


1,858 (50.7) 1,805 (49.3)


N/A


1,504 (41.1) 664 (18.1) 1,495 (40.8) … … …


1,504 (13.8) 664 (6.1)


1,495 (13.7) 2,651 (24.4) 2,847 (26.2) 1,728 (15.9)


NOTE. ED, emergency department; MSSA, methicillin-susceptible Staphylococcus aureus; MRSA, methicillin-


5,537 (50.9) 5,352 (49.2)


1,613 (22.3) 915 (12.7) 778 (10.8) 3,306 (45.8)


Children


(n=3,663), No. (%) P Valuea <.001


703 (9.7) 240 (6.6)


1,214 (33.1) 2,157 (58.9)


<.001


2,455 (22.5) 2,031 (18.7) 867 (8.0)


5,398 (49.6) 8,045 (75.9)


1,951 (18.4) 600 (5.7)


Total (n=10,889), No. (%)


2,316 (21.3) 1,155 (10.6) 1,992 (18.3) 5,491 (50.4)


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