Antimicrobial activity against a global collection of skin and skin structure pathogens: results from the Tigecycline Evaluation and Surveillance Trial (T.E.S.T.), 2010–2014

• Thirty-eight percent of Staphylococcus aureus isolates were methicillin-resistant S. aureus; all were susceptible to tigecycline.
• Forty-three percent of Acinetobacter baumannii isolates were multidrug-resistant.
• There was a significant increase in A. baumannii resistance between 2010 and 2014 (p < 0.0001).
• There was a decrease in minocycline resistance among enterococci, Klebsiella pneumoniae, and Escherichia coli.

SummaryBackgroundAs part of the Tigecycline Evaluation and Surveillance Trial (T.E.S.T.) we report antimicrobial resistance among Gram-positive and Gram-negative isolates collected globally from integumentary sources between 2010 and 2014.MethodsMinimum inhibitory concentrations and antimicrobial resistance were determined according to Clinical and Laboratory Standards Institute guidelines (US Food and Drug Administration breakpoints against tigecycline). The Cochran–Armitage trend test was used to identify statistically significant changes in resistance.ResultsGlobal rates of methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant Acinetobacter baumannii were 38% and 43%, respectively. No S. aureus isolates were resistant to linezolid or vancomycin; all isolates were susceptible to tigecycline. Two percent of Enterococcus faecalis and 28% of Enterococcus faecium were vancomycin-resistant. Extended-spectrum β-lactamase (ESBL) producers accounted for 22% of Klebsiella pneumoniae and 16% of Escherichia coli. Resistance to minocycline among E. faecalis, E. faecium, K. pneumoniae, and E. coli decreased significantly (p < 0.0001). There were significant increases (p < 0.0001) in A. baumannii resistance to cefepime, ceftazidime, ceftriaxone, levofloxacin, meropenem, and piperacillin–tazobactam.ConclusionsAmong isolates from integumentary sources, rates of MRSA and ESBL-producing Enterobacteriaceae are stabilizing. Carbapenems and tigecycline have retained their in vitro activity against Gram-positive and Gram-negative organisms. Few agents were active against A. baumannii; its increasing resistance is cause for concern.