366 Statistical analysis
CRAB growth in air was expressed as number of colony forming units (CFU) per 1,000 L of air. We devised a scoring system to assess CRAB growth from patient and environmental samples semiquantitatively: 0 for no growth, 1 for growth in enrichment culture only, 2 for growth ≤10 CFU from direct plating, 3 for 10–100 CFU, and 4 for ≥100 CFU. We used Spearman’s rank correlation to test the association between CRAB growth in air samples and in patient and environmental cultures, and between CRAB growth in air and time since last chlorhexidine wash. We used a t test to test the association between CRAB growth in air and antibiotic use. Statistical analyses were performed using SPSS version 25 software (IBM, Armonk, NY).
Results
Overall, 10 patients with CRAB in respiratory cultureswere included in the study: 8 had clinical CRAB infection and 2 were
colonized.All patientshadCRABgrowth in respiratory (sputumor buccalmucosa) and skin samples taken on the study day. The mean agewas 51 years (range, 18–76 years) and 8 patients were male. Furthermore, 9 patients were mechanically ventilated throughout the entire sampling period and 1 patient was weened during sampling and was spontaneously breathing through a tracheostomy. In addition, 7 patients were on antibiotics with in vitro activity against CRAB. Total sampling time was 70 hours (140 sampling periods),
during which 252,000 L of air (25,200 L per patient) was sampled; 72,000 L of air (40 sampling periods) was sampled during patient care; and 180,000 L of air (100 sampling periods) was sampled while no treatment activity was occurring in the room. CRAB was detected in 39,600 L of sampled air (16%). Quantitative analysis revealed a mean of 0.36 CRAB CFU per 1,000 L of air (range, 0–1.15 CFU/1,000 L). The yield was similar for 5% blood agar and CHROMagar MDR Acinetobacter plates. Air samples were taken from the surroundings of all 10 patients;
samples from air surrounding 8 of these were positive for CRAB. For all 8 patients, there was a positive air culture during patient care; for 3 patients, an air culture was also positive during a period of no treatment activity. CRAB was isolated from air during 19 of 40 sampling periods (47.5%) during patient care and during 3 of 100 sampling periods (3%) without treatment activity. Mean CRAB growth was higher during periods of treatment activity than during periods of no activity: 1.17 CFU per 1,000 L of air (range, 0–5 CFU/1,000 L) versus 0.02 CFU per 1,000 L (range, 0–0.1 CFU/1,000 L). Endotracheal suctioning, changing of bed sheets, and diaper changing were the activities most likely to be associated with contamination of air (Table 1). We found no association between CRAB growth in the air
surrounding a patient and the degree of CRAB growth in the patient’s respiratory tract or skin, time since last chlorhexidine wash, or antibiotic treatment. The immediate environments of these patients were heavily contaminated by CRAB: CRAB was isolated from 9 of 10 bed rails, 9 of 10 bedsheets, 9 of 10 monitor screens, 8 of 10 bed head outlets, and walls near 4 of 10 patients. There was no correlation between CRAB growth in air and the environmental contamination score.
Discussion
We detected CRAB in the air adjacent to ventilated patients with CRAB respiratory colonization or infection. Air contamination was intermittent; CRAB was detected almost half of the time
Madelyn Mousa et al
Table 1. Carbapenem-Resistant A. baumannii (CRAB) Growth in Air Samples by Type of Treatment Activity during Sampling
Activity
Open system endotracheal suctioning
Closed system endotracheal suctioning
Changing of bed sheets Changing of diaper
Other treatment activity No treatment activity
Total Air Sampled, ×1,000 La
21.6 9
21.6 5.4
25.2 180
Sampled Air With CRAB Growth, ×1,000 L (% of
Total Air Sampled) 16.2 (75)
7.2 (80)
16.2 (75) 3.6 (66.7) 10.8 (42.9) 5.4 (3)
Time Spent on Activity, % of Total Sampling Timea
8.6 3.6
8.6 2.1
10.0 71.4
aBecause some activities were performed together during the 30-minute sampling period, total air sampled and activities add up to >100%.
during periods of patient care but in only 3% of periods without treatment activity. Air contamination was almost 60 times greater during treatment activities, especially during endotracheal suction- ing, changing of bedsheets, and diaper changing. Measures to limit the spread of multidrug-resistant bacteria are
aimed at preventing contact transmission. However, reports of aerosolized bacteria such as S. aureus suggest that droplet aerosol dissemination may also be an important route for environmental contamination and possibly patient-to-patient transmission.8 A recent study found clonal relatedness between Acinetobacter strains isolated from air and subsequent clinical strains, suggesting the possibility of airborne transmission.10 Although it is premature to recommend airborne isolation of patients with respiratory CRAB, recognizing the possibility of droplet aerosol dissemina- tion, especially during patient care activities that generate CRAB aerosols, has implications for infection control. Our study has several limitations. First, our sample size was
small. Second, most patients had an active infection; their CRAB load may have been higher, potentially causing greater spread of CRAB into the environment. Third, we sampled air in only 1 loca- tion; thus, we could not evaluate the distance of CRAB spread. In conclusion, CRAB contaminates air surrounding ventilated
patients with CRAB respiratory infection or carriage, especially during patient care activities. Our results support previous studies suggesting the risk of droplet aerosol transmission.
Acknowledgments. The work performed by Madelyn Mousa was part of the requirements for a medical doctor (MD) degree, Sackler Faculty of Medicine, Tel Aviv University, Israel.Wethank Dr Elizabeth Temkin for her helpful com- ments on this manuscript.
Financial support. This work was supported by the European Commission FP7 AIDA project “Preserving Old Antibiotics for the Future: Assessment of Clinical Efficacy by a Pharmacokinetic/Pharmacodynamic Approach to Optimize Effectiveness and Reduce Resistance for Off-Patent Antibiotics” (grant no. Health-F3-2011-278348).
Conflicts of interest. All authors report no conflict of interest related to this article.
References
1. Peleg AY, de Breij A, AdamsMD, et al. The success of Acinetobacter species: genetic, metabolic, and virulence attributes. PLoS One 2012;7:e46984.
2. Peleg AY, Seifert H, Paterson DL. Acinetobacter baumannii: emergence of a successful pathogen. Clin Microbiol Rev 2008;21:538–582.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132
