Molecular and virulence characteristics of carbapenem-resistant Acinetobacter baumannii isolates: A prospective cohort study

doi:10.21203/rs.3.rs-3240469/v1

This study aimed to characterise the molecular features and virulence profile of carbapenem-resistant Acinetobacter baumannii (CRAB) isolates. Clinical CRAB isolates were obtained from blood cultures of adult patients with CRAB bacteraemia, collected between July 2015 and July 2021 in a Korean hospital. Real-time polymerase chain reaction was used to detect 13 virulence genes, genotyping was conducted via multilocus sequence typing (MLST), and a Tenebrio molitor infection model was selected for survival analysis. A total of 170 clinical CRAB isolates harboured the bla_OXA−23 and bla_OXA−51 genes. MLST genotyping identified 11 CRAB sequence types (STs), of which ST191 was the most predominant (25.7%). Virulence genes were distributed as follows: basD, 58.9%; espA, 15.9%; bap, 92.4%; ata, 86.5%; chop, 7.1%; ompA, 77.1%; pbpG; 93.5%; bfmR, 92.9%; fhaB, 70.6%; abeD, 99.4%; cpaA, 0.6%; lipA, 99.4%; and recA, 100%. In the T. molitor model, ST195 showed a significantly higher mortality rate (73.3% vs. 66.7%, p = 0.015) and ST451 displayed a lower mortality rate (60.0% vs. 73.3%, p = 0.007) compared to counterpart groups. Our findings provided insight on the microbiological features of CRAB blood isolates. A potential framework for using a T. molitor infection model to characterise CRAB pathogen virulence is suggested.

Biological sciences/Microbiology

Health sciences/Medical research

Acinetobacter baumannii

multidrug-resistant

genotyping

virulence factors

Tenebrio molitor

Acinetobacter baumannii is an undoubtedly significant nosocomial pathogen with attributable mortality rates ranging from 8.4–36.5% [1]. Bacteraemia and ventilator-associated pneumonia are the major nosocomial human infections caused by this pathogen. Due to its multidrug resistance and virulence potential, A. baumannii can be associated with unfavourable treatment outcomes. Indeed, carbapenem-resistant A. baumannii (CRAB) has been ranked as a high priority antibiotic-resistant pathogen and an urgent threat by the Centers for Disease Control and Prevention of the United States [2]. According to Korean Antimicrobial Resistance Monitoring System and Korean Nosocomial Infections Surveillance System data, the resistance rate of A. baumannii to imipenem in the Republic of Korea (ROK) increased to 85% in 2015 and 93.5% in 2022, thereby representing a major public threat [3, 4].

Identifying the molecular features and mechanism of virulence is crucial for containing transmission and reducing mortality amidst an increasing number of CRAB infections. In the ROK, a drastic increase in Acinetobacter isolates with bla_OXA−23 genes has been observed since the mid-2000s [5]. Moreover, ST191 A. baumannii harbouring bla_OXA−23 has been held responsible for the high rate of carbapenem resistance recorded in the ROK between 2009 and 2012 [6, 7]. In addition to its complex mechanism of antibiotic resistance, CRAB also carries several virulence genes that may result in the clinical deterioration of patients with illnesses. Unfortunately, little is known about the distribution and clinical implications of virulence genes in this bacterium. Previous studies have suggested that several virulence genes are prevalent in A. baumannii isolates and may be linked with antibiotic resistance [8–11]. Concerningly, recent evidence suggests that a hypervirulent strain of CRAB has evolved, associated with high mortality and even clonal transmission within hospitals [12–14]. However, few studies have focused on the distribution of virulence genes via multilocus sequence typing (MLST) of CRAB blood isolates. The aim of this study was to investigate the molecular characteristics of CRAB blood isolates and to evaluate the survival rates of Tenebrio molitor that had been infected with CRAB strains exhibiting different molecular features.

Bacterial strains and antibiotic susceptibility test

This prospective cohort study was performed in a 1,048-bed university-affiliated hospital in the ROK. Clinical CRAB isolates were obtained from blood cultures of adult patients diagnosed with CRAB bacteraemia between July 2015 and July 2021. This study was approved by the Institutional Review Board of Korea University Anam Hospital [No. 2022AN0292] and the requirement for written informed consent was waived. The study was conducted in accordance with the ethical guidelines and regulations outlined in the Declaration of Helsinki.

All isolates collected on the first day of bacteraemia. Non-repetitive CRAB isolates were identified using a MicroScan WalkAway-96 Plus system (Beckman Coulter, Inc., Fullerton, CA, USA) in a routine laboratory diagnostic scheme. The minimal inhibitory concentrations (MICs) were determined via the agar dilution method, and the breakpoints of the antibiotic susceptibility test were interpreted according to the 2017 Clinical Laboratory Standards Institute guidelines [15]. Carbapenem resistance was defined as resistance to imipenem, at MICs of ≥ 8 µg/mL [15].

Virulence and antimicrobial resistant genes

Multiplex real-time polymerase chain reaction (PCR) assays were performed to detect virulence and antimicrobial resistant genes in CRAB isolates [16]. Thirteen virulence genes (basD, espA, ompA, bap, bfmR, pbpG, fhaB, cpaA, ata, recA, lipA, abeD, and chop) and two carbapenemase genes (bla_OXA−23 and bla_OXA−51) were detected using specific primers (Supplementary Table S1). Virulence genes were associated with siderophore synthesis (basD), bacterial adhesion (espA, bap, ata, chop), biofilm formation (ompA, pbpG), glycoconjugates (bfmR), host cell death (fhaB, abeD), toxin production (cpaA, lipA), and stress response (recA) [17–20]. The PCR cycling conditions were as follows: denaturation at 95 ℃ for 5 min, annealing between 50 ℃ and 61 ℃ for 30–45 s, and extension at 72 ℃ for 1 min (for 34 cycles). The presence of amplified PCR products was determined via electrophoretic separation using 2% agarose gels and visualised with a transilluminator.

Genotypes according to MLST

For MLST genotyping, seven housekeeping genes (gltA, gyrB, gdhB, recA, cpn60, gpi, and rpoD) were amplified and sequenced for A. baumannii, as described previously [21], using specific primers (Supplementary Table S2). MLST was performed using the Oxford scheme, and the sequence types (STs) were assigned using tools available in the A. baumannii MLST database (https://pubmlst.org/organisms/acinetobacter-baumannii).

Virulence assay

A virulence assay was performed using T. molitor larvae (mealworms), as described previously [22]. The larvae were maintained in a plastic box containing wheat bran. CRAB isolates were placed in a brain-heart infusion broth and incubated overnight at 37°C. Next, subcultures were grown on blood agar plates that were incubated for 24 h at 37°C. The cultured CRAB was then suspended in insect saline (130 mM NaCl, 5 mM KCl, and 1 mM CaCl₂) at a concentration of 10⁹ CFU/mL. Using an insulin syringe, 10 µL of the CRAB suspension (at 10⁶ CFU/µl) was injected into a T. molitor larva; in the control group, 10 µL of sterilised insect saline solution was injected instead. Post injection, all larvae were raised in Petri dishes for 72 h at 25°C. Their survival rates were calculated according to melanisation (using a sample of three sets of five larvae per strain).

Statistical analyses

Categorical variables were summarised as frequencies and analysed with the Pearson’s chi-squared or Fisher’s exact test. Continuous variables were expressed as medians with interquartile ranges and were analysed with Student’s t-test. The difference in mortality rates of T. molitor larvae infected with CRAB isolates containing different STs was evaluated via one-way ANOVA. Statistical significance was set at p < 0.05. SPSS v23.0 for Windows software (SPSS Inc., Chicago, IL., USA) was used to conduct statistical analyses.

Antimicrobial susceptibility of CRAB isolates

A total of 170 CRAB blood isolates were collected; all were resistant to three or more antimicrobial agents and therefore considered to be multidrug resistant. The antibiotic resistance patterns of these isolates are shown in Table 1. The highest resistance rate was detected against ciprofloxacin and imipenem (100%), followed by piperacillin (99.4%), cefepime (99.4%), ampicillin/sulbactam (97.6%), gentamicin (90%) and minocycline (10%). The bla_OXA−23 and bla_OXA−51 genes were identified in all strains (Table 2).

Table 1

MIC₅₀ and MIC₉₀ values and antimicrobial susceptibility (%) of CRAB isolates
Antibiotics	MIC (mg/L)			Percentage of susceptible isolates (%)
Antibiotics	MIC₅₀	MIC₉₀	Range	Percentage of susceptible isolates (%)
Imipenem	≥ 16	≥ 16	> 8 to ≥ 16	0
Ampicillin/sulbactam	> 16	≥ 32	4 to ≥ 32	2.4
Minocycline	≤ 1	8	≤ 0.5 to ≥ 16	90.0
Ciprofloxacin	≥ 4	≥ 4	≥ 2 to ≥ 4	0
Piperacillin	≥ 128	≥ 128	≥ 64 to ≥ 128	0.6
Cefepime	≥ 64	≥ 64	≥ 8 to ≥ 64	0.6
Gentamicin	> 16	≥ 16	≥ 1 to ≥ 16	10.0
MIC, minimum inhibitory concentration

Table 2

Distribution of virulence and antimicrobial resistant genes according to CRAB isolate sequence types
Virulence gene, n (%)
N (%)	ST191 (n = 49)	ST195 (n = 28)	ST208 (n = 9)	ST357 (n = 1)	ST369 (n = 7)	ST451 (n = 27)	ST469 (n = 2)	ST491 (n = 4)	ST784 (n = 23)	ST1599 (n = 9)	ST1653 (n = 1)	NT (n = 10)
basD (100)	30 (61.2)	26 (92.9)	2 (22.2)	1 (100)	6 (85.7)	12 (44.4)	2 (100)	3 (75.0)	9 (39.1)	2 (22.2)	1 (100)	6 (60.0)
espA (27)	7 (14.3)	7 (25.0)	0	0	7 (100)	2 (7.41)	0	0	1 (4.35)	2 (22.2)	0	1 (100)
ompA (131)	40 (81.6)	28 (100)	2 (22.2)	1 (100)	6 (85.7)	18 (66.7)	2 (100)	4 (100)	11 (47.8)	9 (100)	1 (100)	9 (90.0)
bap (157)	47 (95.9)	26 (92.9)	9 (100)	1 (100)	7 (100)	27 (100)	2 (100)	1 (25.0)	23 (100)	9 (100)	1 (100)	4 (40.0)
bfmR (158)	45 (91.8)	27 (96.4)	8 (88.9)	1 (100)	7 (100)	27 (100)	2 (100)	4 (100)	17 (13.9)	9 (100)	1 (100)	10 (100)
pbpG (159)	44 (89.8)	27 (96.4)	9 (100)	1 (100)	7 (100)	25 (92.6)	2 (100)	4 (100)	21 (91.3)	9 (100)	1 (100)	9 (90.0)
fhaB (120)	48 (98.0)	1 (3.6)	9 (100)	1 (100)	7 (100)	27 (100)	2 (100)	0	13 (56.5)	9 (100)	0	3 (30.0)
cpaA (1)	1 (2.04)	0	0	0	0	0	0	0	0	0	0	0
ata (147)	48 (98.0)	26 (92.9)	9 (100)	1 (100)	2 (28.6)	26 (96.3)	2 (100)	0	22 (95.7)	8 (88.9)	1 (100)	2 (20.0)
recA (170)	49 (100)	28 (100)	9 (100)	1 (100)	7 (100)	27 (100)	2 (100)	4 (100)	23 (100)	9 (100)	1 (100)	10 (100)
lipA (169)	49 (100)	27 (96.4)	9 (100)	1 (100)	7 (100)	27 (100)	2 (100)	4 (100)	23 (100)	9 (100)	1 (100)	10 (100)
abeD (169)	49 (100)	27 (96.4)	9 (100)	1 (100)	7 (100)	27 (100)	2 (100)	4 (100)	23 (100)	9 (100)	1 (100)	10 (100)
chop (12)	1 (2.0)	2 (7.1)	0	0	1 (14.3)	1 (3.7)	0	3 (75.0)	0	0	0	4 (40.0)
Antimicrobial resistant gene, n (%)
bla_OXA−23 (170)	49 (100)	28 (100)	9 (100)	1 (100)	7 (100)	27 (100)	2 (100)	4 (100)	23 (100)	9 (100)	1 (100)	10 (100)
bla_OXA−51 (170)	49 (100)	28 (100)	9 (100)	1 (100)	7 (100)	27 (100)	2 (100)	4 (100)	23 (100)	9 (100)	1 (100)	10 (100)
ST, sequence type

MLST analysis of CRAB isolates

Our MLST analysis revealed 11 different STs in 160 (94.1%) of the CRAB isolates: ST191, ST195, ST208, ST357, ST369, ST451, ST469, ST491, ST784, ST1599, and ST1653 (Supplementary Table S3). Of these, ST191 was the most abundant type, occurring in 49 (28.8%) isolates. However, ST191 was mostly isolated from 2015 to 2018 samples, while ST195 was mainly found in samples collected between 2019 and 2021. ST451 (n = 27) occurred evenly throughout the study period. ST491 (n = 4), ST1599 (n = 9), ST469 (n = 2), and ST357 (n = 1) were mainly recorded after 2017 (Fig. 1).

Distribution of virulence factors in CRAB isolates

The distribution of virulence genes was as follows: 58.9% basD (siderophore synthesis); 15.9% espA, 92.4% bap, 86.5% ata, and 7.1% chop (bacterial adhesion); 77.1% ompA and 93.5% pbpG (biofilm formation); 92.9% bfmR (glycoconjugates); 70.6% fhaB and 99.4% abeD (host cell death); 0.6% cpaA and 99.4% lipA (toxin production); and 100% recA (stress response) (Table 2). We found that 1 isolate carried 12 virulence genes, 11 isolates carried 11 virulence genes, 49 isolates carried 10 virulence genes, 52 isolates carried 9 virulence genes, 37 isolates carried 8 virulence genes, 14 isolates carried 7 virulence genes, 5 isolates carried 6 virulence genes, and 1 isolate carried 5 virulence genes. Occasionally, the frequency of a virulence gene differed according to ST (Table 2).

Virulence assay

The overall mortality of CRAB-inoculated T. molitor was 70.4%. Mortality rates of T. molitor larvae infected with CRAB isolates showed statistically significant differences among different STs (Table 3): ST1599 vs ST191 (p = 0.004), ST1599 vs ST195 (p = 0.002), ST1599 vs ST208 (p = 0.042), and ST1599 vs ST369 (p = 0.01).

Differences in microbiological characteristics of CRAB among major STs

CRAB isolates with ST191 displayed a significantly lower resistance rate to minocycline than the non-ST191 group (2.0% vs. 13.3%, p = 0.027), while isolates with ST451 possessed a higher resistance rate to minocycline than the non-ST451 group (33.3% vs. 5.6%, p < 0.001). The ST195 group showed a lower resistance rate to tigecycline compared to the non-ST195 group (4.2% vs. 22.1%, p = 0.042). Additionally, the ST191 group showed a higher prevalence than the non-ST191 group in virulence genes such as fhaB (host cell death; 98% vs. 59.5%, p < 0.001) and ata (bacterial adhesion; 98.0% vs. 81.8%, p = 0.005). In contrast, the ST195 group had a higher predominance than the non-ST195 group in terms of basD (siderophore synthesis; 92.9% vs. 52.1%, p < 0.001) and ompA (biofilm formation; 100% vs. 72.5%, p = 0.002) genes. Of note, the ST195 group showed a significantly higher T. molitor mortality rate compared to the non-ST195 group (73.3 vs. 66.7%, p = 0.015), but mortality was lower in the ST451 group compared to the non-ST451 group (60.0% vs. 73.3%, p = 0.007) (Table 4).

Table 4

Comparison of microbiological characteristics according to the main CRAB blood isolate sequence types
	ST191 (n = 49)	Non-ST191 (n = 121)	p value	ST195 (n = 28)	Non-ST195 (n = 142)	p value	ST451 (n = 27)	Non-ST451 (n = 143)	p value
Antimicrobial resistance, n (%)
Imipenem	49 (100)	121 (100)	-	28 (100)	142 (100)		27 (100)	143 (100)	-
Ampicillin/sulbactam	48 (98.0)	118 (97.5)	0.864	28 (100)	138 (97.2)	0.369	25 (92.6)	141 (98.6)	0.059
Minocycline	1 (2.0)	16 (13.3)	0.027	1 (3.6)	16 (11.3)	0.211	9 (33.3)	8 (5.6)	< 0.001
Virulence genes, n (%)
basD	30 (61.2)	70 (57.9)	0.686	26 (92.9)	74 (52.1)	< 0.001	12 (44.4)	88 (61.5)	0.098
espA	7 (14.3)	20 (16.5)	0.717	7 (25.0)	20 (14.1)	0.149	2 (7.4)	25 (17.5)	0.189
ompA	40 (81.6)	91 (75.2)	0.367	28 (100)	103 (72.5)	0.002	18 (66.7)	113 (79.0)	0.161
bap	47 (95.9)	110 (90.9)	0.266	26 (92.9)	131 (92.3)	0.913	27 (100)	130 (90.9)	0.103
bfmR	45 (91.8)	113 (93.4)	0.721	27 (96.4)	131 (92.3)	0.431	27 (100)	131 (91.6)	0.118
pbpG	44 (89.8)	115 (95.0)	0.208	27 (96.4)	132 (93.0)	0.495	25 (92.6)	134 (93.7)	0.829
fhaB	48 (98.0)	72 (59.5)	< 0.001	1 (3.6)	119 (83.8)	< 0.001	27 (100)	93 (65.0)	< 0.001
cpaA	1 (2.0)	0	0.115	0	1 (0.7)	0.656	0	1 (0.7)	0.663
ata	48 (98.0)	99 (81.8)	0.005	26 (92.9)	121 (85.2)	0.280	26 (96.3)	121 (84.6)	0.104
recA	49 (100)	121 (100)	-	28 (100)	142 (100)	-	27 (100)	143 (100)	-
lipA	49 (100)	120 (99.2)	0.523	27 (96.4)	142 (100)	0.024	27 (100)	142 (99.3)	0.663
abeD	49 (100)	120 (99.2)	0.523	27 (96.4)	142 (100)	0.024	27 (100)	142 (99.3)	0.663
chop	1 (2.0)	11 (9.1)	0.104	2 (7.1)	10 (7.0)	0.985	1 (3.7)	11 (7.7)	0.458
T. molitormortality rates % (IQR)	73.3 (60–80)	66.7 (60–80)	0.092	73.3 (66.7–80)	66.7 (60–80)	0.015	60.0 (46.7–73.3)	73.3 (60–80)	0.007
IQR, interquartile range

We demonstrated an evolutionary change in CRAB from blood isolates collected in a hospital, as evidenced in the emergence of new bacterial STs. During the study period, ST191 harbouring the bla_OXA−23 carbapenemase gene was the most prevalent genotype present, and a marked increase in genomic variation was observed after 2019. To the best of our knowledge, this study is the first to evaluate the virulence of CRAB isolates and associated mortality in a T. molitor larva infection model.

CRAB isolates displayed an extensive drug-resistant phenotype, being highly resistant to all clinically available antimicrobial agents, which is consistent with previous findings in the ROK [9, 23]. Our results also revealed that all CRAB isolates harboured bla_OXA−23 genes, which previous studies have identified as the most prevalent carbapenemase gene carried by A. baumannii [24–27]. Our findings suggest that the genetic evolution enabling bla_OXA−23 expression in CRAB contributed to this bacterium establish itself as a highly successful nosocomial pathogen in the clinical setting.

Furthermore, ST191 was the predominant CRAB isolate until 2018, whereafter ST195 became more prevalent. This same shift in the predominant ST—from ST191 to ST195—was also reported in Hong Kong following the emergence of CRAB ST195 harbouring the bla_OXA−23 gene [28]. However, our study demonstrated that ST451 first emerged in 2016, and it has been steadily discovered during study period. A previous study in the ROK similarly reported that ST451 was the prevalent ST between 2016 and 2018, in the context of clonal evolution related to antimicrobial resistance [9]. Indeed, all the prevalent STs we recorded—ST191, ST195, and ST 451—are well-known multidrug-resistant clones [11].

Several virulence factors may influence disease progression into critical illness, related to functions such as transmission, binding to host structures, cellular damage, and invasion. Consistent with previous research, we found that the stress response-associated recA was present in all CRAB isolate samples [10]. The remaining virulence genes showed differential distributions according to ST. A correlation between virulence genes and multidrug-resistant phenotypic differences of CRAB isolates have been suggested previously [9–11]. Selection pressure may drive the formation of virulence factors and acquisition of multidrug resistance in the process of adaptation, facilitating the survival of these isolates in a clinical setting.

Previous reports have also suggested a positive relationship between biofilm formation and antibiotic resistance in A. baumannii isolates [29, 30]. Although our study did not confirm the biofilm-forming capacity of CRAB isolates, we assessed the frequency of biofilm-associated gene occurrence in CRAB that harbour bla_OXA−23, recording 15.9%, 92.4%, 86.5%, 7.1%, 77.1%, and 93.5% for espA, bap, ata, chop, ompA, and pbpG, respectively. Particularly the ompA and bap genes are essential for bacterial adhesion to human epithelial cells, the development of biofilms, and antimicrobial resistance [31, 32]. In Iran and Korea, respectively, A. baumannii isolates harbouring ompA (81% and 69%) and bap (92% and 100%) genes were similarly identified [30, 33–35]. The surveillance of and control measures against CRAB isolates with biofilm-associated genes could be essential to containing their emergence and transmission.

We furthermore evaluated the virulence of CRAB blood isolates using T. molitor larvae as an infection model. Mealworms are widely used to assess the pathogenic virulence of bacteria such as Listeria monocytogenes, Staphylococcus aureus, and Aeromonas hydrophila [36–38]. Galleria mellonella is another reliable model for evaluating CRAB strain pathogenicity [39]. Although none of these species can replace mammalian models, T. molitor larvae offer an attractive alternative for investigating host-pathogen interactions involving CRAB isolates due to their cost-effectiveness and ease of handling.

Interestingly, our study showed that the mortality rates of T. molitor larvae infected by CRAB isolates differed according to ST. The relative rarity of some STs, resulting in a corresponding small sample size of related blood isolates, prevented us from drawing definite conclusions in this regard. Nevertheless, ST195 larvae showed a significantly higher mortality rate than those in the non-ST195 group, while ST451 mealworms exhibited a lower mortality rate than those in the non-ST451 group. ST191 also displayed the trend of a higher mortality rate among larvae compared to the non-ST191 group, although this difference was not statistically significant. Cox-regression multivariable analysis in a clinical study with similar results found that ST191 was a risk factor associated with 30-day mortality in patients with A. baumannii bloodstream infections, while ST451 served as a protective factor [11]. The distribution of STs varies according to geographical location [14, 40]. In Taiwan, ST218 harbouring the bla_OXA−72 gene (which was not encountered in our study) was also reported as a hypervirulent strain, raising the possibility of intra-hospital transmission and mortality [14].

Our study demonstrated that ST191 exhibited a significantly lower resistance rate to minocycline than non-ST191 isolates, while ST451 showed the opposite result. Considering that the most dominant ST is shifting from ST191 to ST451, it is evident that CRAB isolates are evolving toward becoming more multidrug-resistant and virulent. As a result, delays in appropriate antibiotic administration and a more rapid disease progression may have a synergistic effect, contributing to treatment failure. The antibiotic susceptibility, genetic types, and virulence genes of CRAB blood isolates that constitute microbiological characteristics may well be related to each other.

There are some limitations to our study. First, all CRAB blood isolates were collected from a single hospital in the ROK, and a generalisation of results to other regions or healthcare facilities may be problematic. Further research is necessary, utilising larger sample sizes from different clinical settings, to fully understand CRAB microbiological characteristics. Second, we analysed only a limited number of virulence types and antibiotic resistance genes, disregarding other factors that could potentially contribute to CRAB infection pathogenicity. Finally, our virulence assay relied on an insect model, which may not accurately reflect the virulence of CRAB isolates in humans.

CRAB blood isolates with different STs exhibited differences in antibiotic susceptibility and virulence. Insights into dynamic changes in antibiotic resistance mechanisms and virulence factors among CRAB isolates are necessary for the effective control and treatment of CRAB infections. We propose the use of a T. molitor infection model as an alternative approach for evaluating the pathogenicity of CRAB isolates. Research with increased sample sizes obtained from a variety of settings is essential to further explore the microbiological properties of CRAB isolates.

Conflict of interest

The authors declare that they have no competing interests.

Funding

This study was supported by grants from Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health and Welfare, Republic of Korea (Grant Number: HI23C1297). The funding sources had no role in the study design, data collection, data analysis, decision to publish, or manuscript preparation.

Acknowledgements

None.

Data availability

The datasets generated during the current study are available in the NCBI GenBank database under accession numbers OR498912 - OR499081, [https://www.ncbi.nlm.nih.gov/nucleotide/]. Further information is provided from the corresponding author upon reasonable request.

Contributions

YKY conceived, designed, and performed this study. JWS, JYK, SBK, and JWS contributed to the data collection and analysis. SMP and YKJ performed the experiments. YKY, JWS, and SMP wrote the manuscript.

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Table 3 is available in the Supplementary Files section.

No competing interests reported.

Molecular and virulence characteristics of carbapenem-resistant Acinetobacter baumannii isolates: A prospective cohort study

Status:

Journal Publication

Version 1

Abstract

Figures

INTRODUCTION

METHODS

Bacterial strains and antibiotic susceptibility test

Virulence and antimicrobial resistant genes

Genotypes according to MLST

Virulence assay

Statistical analyses

RESULTS

Antimicrobial susceptibility of CRAB isolates

MLST analysis of CRAB isolates

Distribution of virulence factors in CRAB isolates

Virulence assay

Differences in microbiological characteristics of CRAB among major STs

DISCUSSION

Conclusion

Declarations

References

Tables

Additional Declarations

Supplementary Files

Status:

Journal Publication

Version 1