Is airborne transmission of Acinetobacter baumannii possible?
Healthcare-associated infections due to Acinetobacter species have traditionally been regarded a result of hand-borne transmission from a known patient or environmental source, or arising in patients with prior colonisation. Yakupogullari Y et al. noted increases in the incidence of Acinetobacter infections despite substantial reductions in other healthcare-associated infections in a large European healthcare facility, so sought to understand the potential dynamics of airborne spread as a way to understand local epidemiology (Am J Infect Control 2016; 44:1595-1599).
Prospective surveillance was performed in 2013, with air sampling performed in the ICU from 4 defined areas, as well as additional sampling (1m, 2m or 3m from bedside) for patients diagnosed with Acinetobacter infection. All A. baumannii isolates were molecularly typed (PCR) to investigate the clonal relationship between clinical samples and environmental air sampling. Study sites were all HEPA filtered.
A total of 186 air samples were collected (118 from defined regions of ICU; 68 from patients’ bedsides). A. baumannii was isolated from 26 (13.9%) of these, and 13 genetic clones were identified. A. baumannii existed at 0.39 CFU/m3 in the bedside air of infected patients, and was present at 0.27 CFU/m3 in other ICU areas. A clonal relationship was identified between air genotypes and clinical isolates, and the air closest to infected patients (1m) contained greater concentrations of the organism than air sampled at a greater distance from the patient (2m or 3m).
Findings demonstrate that ICU patients infected with A. baumannii can discharge the bacterium into the air. One limitation of the study is the small number of patients included in the cohort, and the lack of clinical information provided concerning cases. For example, it would be relevant to understand if patients were receiving targeted antimicrobial therapy for A. baumannii at time of sampling, and if patients were on closed-circuit ventilation systems. Notwithstanding these limitations, a healthcare facility with increasing incidence of infections despite appropriate implementation of staff hand hygiene measures and contact precautions may consider additional measures for control (e.g. negatively-pressured single-room).
Hospital-acquired Staphylococcus aureus bloodstream infections: significance of non-CVC-associated events
Bloodstream infection due to Staphylococcus aureus is associated with significantly morbidity, mortality and healthcare cost. While the presence of indwelling medical devices (e.g. central venous catheters, CVCs) is a recognised risk for infection, hospital-acquired infections may also arise in other settings. Kovacs C.S. et al. (Am J Infect Control 2016; 44:1252-1255) sought to determine the incidence, clinical characteristics and outcomes of primary hospital-acquired bloodstream infection (HABSI) due to S. aureus.
Retrospective analysis of all S. aureus HABSI at a US healthcare facility was performed for the period 2010-2013. National Healthcare Safety Network definitions for primary and secondary HABSI were applied. Primary HABSI that did not meet the definition for central-line associated bloodstream infection (CLABSI) was considered non-CLABSI. Potential risks for infection were gleaned by review of medical charts.
In total, 346 HABSIs due to S. aureus were identified (incidence 0.24/1000 patient days). A total of 122 primary infections were identified: 78 (64%) were CLABSIs, and 44 (36%) were non-CLABSIs. MRSA isolates comprised 48.7% and 43.2% of these groups, respectively. Twenty-six (43.1%) non-CLABSI events occurred in the presence of a peripheral intravenous catheter or midline catheter. Approximately half of infections had onset outside of an ICU ward. Mean time from hospital admission to onset of infection was shorter for non-CLABSI compared with CLABSI events (6 vs. 16.3 days, p=0.001). Complicated bacteraemia was more common in the non-CLABSI group (15.9% vs. 0%). 30-day all-cause mortality was comparable in for both groups (21.8% vs. 20.4%, p=0.86).
These findings highlight the burden of illness associated with non-CLABSI S. aureus bloodstream infections (significant mortality and complications), and the need for prevention programs to focus upon peripheral intravenous catheters and midline catheters. Such programs are required broadly in non-ICU settings. In light of the early onset of non-CLABSI infections, prevention programs must specifically include review of practices at time of hospital admission (e.g. management of peripheral intravenous catheters in transferred patients).