**2.2 Common sources: respiratory and urinary tract**

Infections of the lower respiratory and urinary tracts comprise the majority of sepsis presentations to the ED. Community-acquired pneumonia (CAP) can be caused by a variety of bacterial and viral pathogens, with *Strepotococcus pneumoniae* being the most common bacterial etiology in those requiring hospitalization [13]. Other commonly implicated organisms include *Haemophilus influenzae, Mycoplasma pneumoniae,* and respiratory viruses. In patients requiring admission to a critical care unit, *S. pneumoniae* is still the most common etiologic organism but *Legionella pneumophila, Staphylococcus aureus,* gram-negative bacilli and influenza virus are more common [14]. Risk factors for drug resistance in CAP include age > 65, alcoholism, medical comorbidities, immunocompromise, immunosuppressive medication use, and use of beta-lactam, macrolide, or fluorquinolone antibiotics in the last 3–6 months [15]. Patients with hospitalization within three months have increased risk for hospital-acquired pneumonia with nosocomial organisms and their antibiotic regimens should include adequate coverage for *Staphylococcus aureus* and *Psuedomonas auerginosa,* which are more common in this population [15].

Infections of the urinary tract account for 40% of cases of nosocomial sepsis and the risk of infection is greatest in patients with structural or functional genitourinary abnormalities [16]. Sepsis from urinary source is more common in females [17].

Uncomplicated cystitis and pyelonephritis in women is typically caused by *Escherichia coli,* though *Proteus mirabilis, Klebsiella pneumoniae,* and *Streptococcus saprophyticus* are also relatively common [18]. As such, empiric treatment for uncomplicated urinary tract infections is best tailored to the regional *E. coli* sensitivities [18]. A complicated urinary tract infection is one which is associated with a condition that increases the risk for therapeutic failure [19]. These risk factors include diabetes, pregnancy, ureterolithiasis, renal failure, >7 days of symptoms, or an indwelling urinary device [19]. The microbial spectrum of complicated UTI is more varied and includes not only the typical organisms associated with uncomplicated UTI but also *Pseudomonas, Staphylococcus*, and *Serratia* species as well as fungi [19]. Complicated lower urinary tract infections may be managed as an outpatient; indications for hospitalization include inability to tolerate oral therapy or suspected infection with an organism resistant to oral therapies, such as extended-spectrum beta-lactamase producing organisms (ESBLs) [19].
