313. Utilization of Methicillin Resistant Staphylococcus aureus Nares Screens for Empiric Antibiotic Therapy
Session: Poster Abstract Session: HAI: MSSA, MRSA, and other Gram-Positives
Thursday, October 27, 2016
Room: Poster Hall
Background: Methicillin resistant Staphylococcus aureus (MRSA) continues to be a burdensome hospital and community acquired pathogen, leading to excess morbidity, mortality and high heath care cost. As the empiric drug of choice for MRSA infections, vancomycin therapy has limitations such as side effects, emerging resistance, and selective pressures on nosocomial bacteria such as Enterococcus. Efficacy of MRSA surveillance screening to decrease in-hospital transmission is controversial, but colonization with MRSA is a known risk factor for developing infection with potential utility in designing empiric antibiotic therapy.

Methods: A retrospective chart review was completed on 3341 patients with any positive culture and nares screen performed from May 2013 to December 2014. Culture source, organism, and duration between screen and culture were collected. Patient in all clinical settings, and all specimen types were included.

Results: Of the 3341 cultures, 1962 (58.7%) were urine cultures, 316 (9.5%) were blood cultures, 732 (21.9%) were skin/soft tissue (SST) cultures, and 165 (4.9%) were respiratory cultures. The performance characteristics of nares screening is shown in the table below with no statistical difference between blood, SST or respiratory tract infections. Nares screening was statistically least predictive of urine infection. Average time between screen and culture was 124 days with the median time of 42 days. 23.6% of patients were colonized with MRSA and 58.4% of S. aureus cultured was resistant to methicillin.

Source

Sensitivity

Specificity

PPV

NPV

OR (95% CI, p)

Blood

51.0

74.5

26.9

89.2

3.05 (1.63-5.71, p=0.0005)

Urine

42.6

78.6

5.4

97.9

2.73 (1.57-4.74, p=0.0002)

Skin/Soft Tissue

49.6

80.7

35.9

88.0

4.12 (2.77-6.13, p<0.0001)

Respiratory Tract

57.6

81.8

44.2

88.5

6.1 (2.69-13.86, p<0.0001)

All

50.0

78.9

18.3

94.4

3.73 (2.92-4.78, p<0.0001)

Conclusion: Given the high NPV of nares screens, regardless of time between screen and culture proven infection, excluding empiric vancomycin may be considered in certain clinical scenarios, including de-escalation of antibiotics. This could potentially limit unnecessary vancomycin exposure and associated risks. These results show that MRSA colonization is a significant risk factor for developing subsequent infections, and further research aimed at reducing such risk with decontamination or other strategies is needed.

Jacqueline Burnell, MD1, Melanie Valentin-Torres, MD2, Sharon M Smith, PhD3 and Robert H K Eng, MD3, (1)Internal Medicine, Rutgers- New Jersey Medical School, Newark, NJ, (2)Infect Disease, NJ Medical School Rutgers, Newark, NJ, (3)Infectious Disease, VA New Jersey Healthcare System, East Orange, NJ

Disclosures:

J. Burnell, None

M. Valentin-Torres, None

S. M. Smith, None

R. H. K. Eng, None

Findings in the abstracts are embargoed until 12:01 a.m. CDT, Wednesday Oct. 26th with the exception of research findings presented at the IDWeek press conferences.