Page 217 - 2021_12-Haematologica-web

Letters to the Editor
specifically, S. aureus was identified during the flu season in 24% of episodes (Online Supplementary Table S1), a rate that did not differ from that of the other episodes of ACS (35%; P=0.3).
The baseline characteristics were similar between the two groups, except the presence of a more frequent prior history of S. aureus infections in the S. aureus group, as compared with the control group (28% vs. 6%; P=0.01) (Online Supplementary Table S1). Despite similar rates of influenza and pneumococcal vaccination, the pneumo- coccal vaccination strategies differed (13-valent pneumo- coccal vaccine only: none in the S. aureus group vs. 17% in the control group; P=0.02).
The characteristics, management and outcomes of ACS were also similar between the two groups. Post-hospital outcomes marginally differed, in terms of number of and time to hospital readmission for vaso-occlusive crisis or ACS (Online Supplementary Figure S2).
Among the 29 ACS episodes with S. aureus, 21 isolates (72%) were sent to the National Staphylococcus Reference Center for genotyping analysis. S. aureus strains were genetically diverse, covering the four acces- sory gene regulator groups and assigned to 12 clonal complexes (CC) (Table 2). At least one toxin gene was found in 13 isolates (62%); two methicillin-sensitive (MSSA) isolates (10%) had a gene coding for panton- valentine leukocidin (PVL).
This study underlines the importance and the clonal
diversity of S. aureus during severe episodes of ACS. Although unrelated to the influenza epidemic, ACS asso- ciated with S. aureus appeared inversely related to the pneumococcal vaccination strategy, raising the question of how the pneumococcal vaccination may affect the nasopharyngeal colonization of those patients. A history of S. aureus infection was associated with the subsequent development of a documented ACS episode with S. aureus.
In our study, one quarter of the episodes of ACS were associated with S. aureus, although this microorganism is infrequently involved in community-acquired LRTI4 and in ACS.1 Current guidelines advise using antibiotics tar- geting S. pneumoniae and intracellular bacteria.5 In our series, S. pneumoniae was identified in only four episodes of ACS (accounting for 5% of episodes with a complete microbiological investigation) including two co-infec- tions with S. aureus. This low proportion of S. pneumoniae is probably due to the good pneumococcal vaccination coverage in our cohort. One hypothesis explaining the increase in the prevalence of S. aureus could be a decrease in the carriage of S. pneumoniae related to the extensive vaccination in this fragile population. The effectiveness of pneumococcal vaccination has led to the decrease in invasive pneumococcal infection in SCD patients, and may have changed the prevalence of S. aureus infection in this population.6 An inverse relationship between the oropharyngeal carriage of S. pneumoniae and S. aureus
Figure 1. Selection of the episodes of acute chest syndrome. §The microbiological investigation was incomplete in 42 episodes, including 26 episodes (25 patients) with no respiratory tract samples, 14 episodes (14 patients) with no blood culture, and 16 episodes (14 patients) with no pneumococcal and legionella urinary antigen testing. Altogether, 77 episodes (in 74 patients) with a complete microbiological investigation were analyzed, including 29 episodes (24%) asso- ciated with Staphylococcus aureus (S. aureus) in 28 patients (1 patient had two episodes of acute chest syndrome [ACS] associated with S. aureus), and 48 episodes (in 49 patients) associated either with another microorganism or with no microorganism.
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