Susceptibilities among bacterial pathogens isolated from patient groups frequently admitted to the emergency department, 2003-2004

Abstract

Study objectives: Community-acquired pneumonia, hospital-acquired pneumoniae, skin and soft tissue infections, and urinary tract infections can be caused by a variety of Gram-positive and Gram-negative bacterial pathogens, often requiring physicians to use empiric therapy, especially when patients are encountered in the emergency department (ED). We reviewed recent in vitro susceptibility for ceftriaxone, fluoroquinolones, other β-lactams, and clinically relevant comparators. Methods: Susceptibility data from January 2003 to February 2004 were analyzed from the Surveillance Network Database-USA, an electronic network that collects data from more than 300 microbiology laboratories in the United States. Data were analyzed for Streptococcus pneumoniae (SP), Streptococcus pyogenes (SPY), oxacillin-susceptible Staphylococcus aureus (OSSA), Haemophilus influenzae (HI), Klebsiella pneumoniae (KP), and Escherichia coli (EC) isolates from lower respiratory tract, skin and soft tissue, and urinary tract infections of outpatients aged 18 years or older, hospitalized patients including ICU patients aged 18 years or older, and elderly (≥65 years) nursing home patients. National Committee for Clinical Laboratory Standards (2004) breakpoints were used to interpret as susceptible or resistant. Results: Resistance rates for lower respiratory tract infections among SP ICU patients and outpatients (n=2,863; 1,038), respectively, for amoxicillin-clavulanate (0.6, 1.5%), levofloxacin (1.7, 1.4%), and ceftriaxone (1.4, 0.9%) were the lowest of the agents tested. For SP from ICU patients and outpatients, penicillin resistance was greater than 16% and macrolide resistance was greater than 31%. For HI from ICU patients and outpatients (n=1,116 and 440), all isolates were susceptible to ceftriaxone and levofloxacin. Resistance rates were less than 5% for amikacin, cefepime, and ceftriaxone among lower respiratory tract infections for ICU patients and outpatients among KP (n=4,431 and 703) and EC (n=3,076 and 473), whereas fluoroquinolone resistance rates were greater than 9% among KP and greater than 29% among EC. For SST, 46.7% (n=31,726) and 57.1% (n=32,832) of SA were oxacillin-susceptible from ICU patients and outpatients, respectively. Among OSSA, 100% of ICU patient (n=2,082) and 99.6% of outpatient (n=2,082) isolates tested were susceptible to ceftriaxone. For skin and soft tissue infections, 100% of SPY were susceptible to ceftriaxone, cefepime, levofloxacin, and penicillin. For SST, resistance ranged from 1% to 3% for ceftriaxone and 15% to 24% for fluoroquinolones for EC and from 2% to 4% for ceftriaxone and 7% to 11% for fluoroquinolones for KP. According to resistance rates for urinary tract infection, amikacin, cefepime, and ceftriaxone were the most active agents tested, regardless of ICU patient or outpatient status. This same trend was seen for EC and KP from urinary tract infection of elderly patients in nursing homes. Conclusion: The prevalence of resistance varies by organism and drug. Traditional broad-spectrum cephalosporins such as ceftriaxone retain activity to a wide range of pathogens associated with infections commonly encountered in the ED, including resistant SP and HI. Of concern is the frequent occurrence of fluoroquinolone resistance for EC, as great as 32% for lower respiratory tract infections, 24% for skin and soft tissue infections, and 33% for nursing home urinary tract infections, in addition to the high prevalence of oxacillin resistance among SA from skin and soft tissue infections. These data confirm the importance of antibiograms in selecting appropriate therapies in the ED.