Geographical distribution of the five teaching hospitals in Guangzhou City
5 teaching hospitals are from the central region of Guangzhou (Figure 1B). GFPH and FAH are located in the Yuexiu district; TAH is located in the Tianhe district; GXH and GRCH are located in the Haizhu district. Those three districts have more than 70% of the medical resources of Guangzhou (Figure 1A).
Summary of 138 A. baumannii isolates
Among the 138 A. baumannii isolates, 66 isolates were from GFPH, 32 isolates were from FAH，29 isolates were from GRCH, 6 isolates were from TAH and 5 isolates were from GXH (Table 1). Most of the patients (55.8%, 77/138), received care in intensive care units (ICUs), followed by the Emergency department (8.7%, 12/138), Department of Respiratory medicine (8.0%, 11/138) and Burn surgery department (5.8%, 8/138) and others (21.7%, 30/138) (Figure 2A and Table 1). However, each hospital had its unique pattern. Compared to other hospitals, the GFPH had more patients from Department of Respiratory medicine while FAH showed more patients in Neurology department. In GRCH, most patients came from Emergency department (34.5%, 10/29）(Figure 2A).
The respiratory system (72.5%, 100/138) was the most common site where A. baumannii was found, followed by the blood (14.5%, 20/138）and wounds (6.5%, 9/138）. When comparing among hospitals, FAH had a higher portion of A. baumannii obtained from blood, while GFPH had more respiratory samples, and GRCH had more wound samples (Figure 2B).
Despite the clinical features of the A. baumannii isolates were vary by different hospitals, the antimicrobial susceptibility testing results were quite similar within the 5 hospitals. Among the 138 A. baumannii isolates, the susceptibility to polymyxin B was 99.1%, followed by tigecycline 89.8%, while its susceptibility to other antimicrobial agents was below 30% (Figure 3, supplementary table 2 and supplementary figure 1).
MLST and SBT- blaOXA-51-like genes
By using MLST, 66 A. baumannii isolates from GFPH were grouped into 15 different STs, including 5 existing STs and 8 novel STs (STn1 to STn8). ST195 was the most common STs (33.3%, 22/66). The clonal relationship analysis showed ST195, ST208, ST136, ST457, ST533, ST548, STn1, STn2, STn5, STn7 and STn8 formed a clone complex (CC), named CC195. ST195 was predicted to be the founder of CC195 (Supplementary figure 2A and Table 1).
MLST grouped 32 A. baumannii isolates from FAH into 12 different STs, including 3 existing STs and 9 novel STs (STn2 and STn9 to STn16). The most common STs were ST195 and ST208 (62.5%, 20/32). The clonal relationship analysis demonstrated those isolates formed two CCs, one is CC195 with the founder ST195 and the other CC including 2 new STs, STn9 and STn13 (Supplementary figure 2B). 29 A. baumannii isolates from GRCH were grouped into 9 different STs, including 6 existing STs and 3 novel STs (STn2, STn8 and STn17). ST195 was the most common ST (37.9%, 11/29). Those isolates formed a CC195 according to the clonal relationship analysis (Supplementary figure 2C and Table 1).
We analyzed 138 A. baumannii isolates from 5 hospitals. CC195, with its predicted founder ST195 (accounted for 35.5% of all isolates, 49/138), was the most epidemic STs (Figure 4A and Table 1). We combined 138 A. baumannii isolates with 225 A. baumannii isolates from MLST database (Accessed 22 Mar 2017) submitted by other researches from China and ran the clonal relationship analysis (Figure 4B, Table 1and Supplementary table 3). The results showed CC92, with its founder ST92, was the most epidemic STs in China. Additionally, we also found a new sub-CC195 is forming in Guangzhou, China, and derived from CC92. (Figure 4B).
According to the SBT-blaOXA-51-like genes, most A. baumannii isolates including all ST195 carried OXA-66 (95.7%, 132/138). Isolate_11 from GFPH carried OXA-199. Isolate_80, isolate_81, isolate_90 and isolate_98 from FAH carried OXA-68, OXA-121, OXA-441 and OXA-64 respectively. Isolate_80 and isolate_89 FAH carried a new blaOXA-51-like gene named OXA-n1.OXA-n1 has a C-insertion mutation at 200 bases which is different from OXA-66 (EF534257.1) (Table 1).