Misconceptions in interpretation of antimicrobial resistance data

indicate the increasing awareness of antimicrobial resistance and the need for antibiotic stewardship, but also illustrate misconceptions that adversely affect patient management and antibiotic prescribing. Failure to distinguish colonisation from infection. Specimens such as urine, sputa or pus swabs, collected from non-sterile sites, are liable to contamination with the normal resident flora or with acquired colonising organisms. Pointers to genuine infection include relevant clinical symptoms and signs, pus cells on microscopy and a pure or predominant growth of a recognised pathogen on culture. Diagnosis of infection is facilitated by submitting appropriately collected specimens. In their article on urinary tract infections among outpatient attendees in Bloemfontein, Bosch et al. 1 provide no details of the type or quality of urine samples submitted and do not indicate quantitative counts, which are standard methods developed to increase accuracy in the diagnosis of urinary tract infections. No information about clinical symptoms is provided, despite asymptomatic bacteriuria requiring treatment only in certain specified circumstances, such as pregnancy or before urological surgery. 4 Their data therefore provide useful information on antibiotic resistance patterns in urine samples submitted from outpatients, but not necessarily on outpatients with urinary tract infections. Similarly Truong et al. 3 fail to distinguish colonisation from infection in their study on skin and soft-tissue infections with Staphylococcus aureus in Botswana. Failure to differentiate between community and hospital-acquired infections. Major risk factors for infection or colonisation with resistant organisms are prior hospitalisation and antibiotic exposure. Attendance at certain outpatient healthcare facilities, such as dialysis units or chemotherapy units, can be included in a broader definition of healthcare-associated infections. The length of time following discharge during which a patient is still at risk of hospital-acquired infection is debatable – 2-3 months may be reasonable, though colonisation with organisms such as Acinetobacter baumannii may last for 6 months or more. 5 In southern Africa, many chronically ill HIV-infected patients are exposed to multiple antibiotics and repeated hospitalisation for long periods, and constitute a pool of patients at high risk for infection or colonisation with resistant organisms. 6 This is illustrated by Heysell et al. 2 among patients hospitalised with TB in rural KwaZulu-Natal; 9/11 (82%) patients with methicillin-resistant S. aureus (MRSA) carriage on admission had been hospitalised in the past 2 years, compared with only 17/41 (41%) of those without MRSA carriage on admission. Although MRSA carriage was not associated with HIV status, it was significantly associated …