Shiga Toxin-Producing Escherichia coli in Plateau Pika (Ochotona curzoniae) on the Qinghai-Tibetan Plateau, China

Characteristics of Shiga Toxin-Producing Escherichia coli Circulating in Asymptomatic Food Handlers

Shiga toxin-producing Escherichia coli (STEC) is a foodborne zoonotic pathogen that causes diarrhea, hemorrhagic colitis (HC), and hemolytic uremic syndrome (HUS) worldwide. Since the infection can be asymptomatic, the circulation of STEC in some asymptomatic carriers, especially in healthy-food-related professionals, is not yet well understood. In this study, a total of 3987 anal swab samples from asymptomatic food handlers were collected, and ten swabs recovered STEC strains (0.251%). Of the ten STEC isolates, seven serotypes and eight sequence types (ST) were determined using whole genome sequencing (WGS). Two stx1 subtypes (stx1a and stx1c) and four stx2 subtypes (stx2a, stx2b, stx2d, and stx2e) were detected. Seven different insertion sites were found in fourteen Stx prophages, and the dmsB and yfhL were the newly identified insertion sites. The ten strains showed the variable Stx transcription levels after the mitomycin C induction. The whole-genome phylogeny indicated that the strains from the asymptomatic food handlers were genetically distant from the strains of HUS patients. The STEC isolates circulating in asymptomatic carriers might pose a low potential to cause disease.

Antimicrobial Resistance Surveillance of Tigecycline-Resistant Strains Isolated from Herbivores in Northwest China

There is no doubt that antimicrobial resistance (AMR) is a global threat to public health and safety, regardless of whether it’s caused by people or natural transmission. This study aimed to investigate the genetic characteristics and variations of tigecycline-resistant Gram-negative isolates from herbivores in northwest China. In this study, a total of 300 samples were collected from various provinces in northwest China, and 11 strains (3.67%) of tigecycline-resistant bacteria were obtained. In addition, bacterial identification and antibiotic susceptibility testing against 14 antibiotics were performed. All isolates were multiple drug-resistant (MDR) and resistant to more than three kinds of antibiotics. Using an Illumina MiSeq platform, 11 tigecycline-resistant isolates were sequenced using whole genome sequencing (WGS). The assembled draft genomes were annotated, and then sequences were blasted against the AMR gene database and virulence factor database. Several resistance genes mediating drug resistance were detected by WGS, including fluoroquinolone resistance genes (gyrA_S83L, gyrA_D87N, S83L, parC_S80I, and gyrB_S463A), fosfomycin resistance genes (GlpT_E448K and UhpT_E350Q), beta-lactam resistance genes (FtsI_D350N and S357N), and the tigecycline resistance gene (tetR N/A). Furthermore, there were five kinds of chromosomally encoded genetic systems that confer MDR (MarR_Y137H, G103S, MarR_N/A, SoxR_N/A, SoxS_N/A, AcrR N/A, and MexZ_K127E). A comprehensive analysis of MDR strains derived from WGS was used to detect variable antimicrobial resistance genes and their precise mechanisms of resistance. In addition, we found a novel ST type of Escherichia coli (ST13667) and a newly discovered point mutation (K127E) in the MexZ gene of Pseudomonas aeruginosa. WGS plays a crucial role in AMR control, prevention strategies, as well as multifaceted intervention strategies.

Antimicrobial resistance surveillance of Escherichia coli from chickens in the Qinghai Plateau of China

Antimicrobial resistance (AMR) may lead to worldwide epidemics through human activities and natural transmission, posing a global public safety threat. Colistin resistance mediated by the mcr-1 gene is the most prevalent among animal-derived Escherichia coli, and mcr-1-carrying E. coli have been frequently detected in central-eastern China. However, animal-derived E. coli with AMR and the prevalence of mcr-1 in the Qinghai Plateau have been rarely investigated. Herein, 375 stool samples were collected from 13 poultry farms in Qinghai Province and 346 E. coli strains were isolated, of which eight carried mcr-1. The AMR rates of the E. coli strains to ampicillin, amoxicillin/clavulanic acid, and tetracycline were all above 90%, and the resistance rates to ciprofloxacin, cefotaxime, ceftiofur, and florfenicol were above 70%. Multidrug-resistant strains accounted for 95.66% of the total isolates. Twelve E. coli strains showed colistin resistance, from which a total of 46 AMR genes and 36 virulence factors were identified through whole-genome sequencing. The mcr-1 gene resided on the IncHI2, IncI2-type and IncY-type plasmids, and mcr-1 was located in the nikA-nikB-mcr-1-pap2 gene cassette (three strains) or the pap2-mcr-1-ISApl1 structure (one strain). Completed IncI2-type plasmid pMCR4D31–3 sequence (62,259 bp) revealed that it may cause the horizontal transmission of mcr-1 and may increase the risk of its spread through the food chain. Taken together, the AMR of chicken-derived E. coli in the plateau is of concern, suggesting that it is very necessary for us to strengthen the surveillance in various regions under the background of one health.

Isolation and Antimicrobial Susceptibility Profile of Escherichia coli O157 : H7 from Raw Milk of Dairy Cattle in Holeta District, Central Ethiopia

A cross-sectional study was conducted in small, medium, and large-scale dairy farms of Holeta district to isolate, identify, and antimicrobial susceptibility profile of Escherichia coli O157 : H7 in raw milk of dairy cattle. A total of 210 lactating cows were selected for raw milk samples, and 19% (40/210) were found to be positive for E. coli whereas 5.2% (11/210) were confirmed as E. coli O157 : H7 positive using the Escherichia coli O157 latex test. Accordingly, all E. coli was highly susceptible to Ciprofloxacin (100%), Gentamycin (100%), Oxytetracycline (100%), and Tetracycline (63.63%). Furthermore, the resistance of 72.73%, 54.54%, 54.54%, and 45.45% was developed to Cefoxitin, Sulphamethoxazole, Cloxacillin, and Streptomycin, respectively. Factors such as parity, age, body condition, herd size, milk yield, udder hygiene, and udder lesion showed a statistically significant ( $p<0.05$ ) association with the occurrence of E. coli infection in dairy cattle. In conclusion, in this study, a higher prevalence of Escherichia coli O157 : H7 and its drug susceptibility profile is an alarm for the health of the public, and awareness creation to the farm owners and the community is recommended.

Molecular characterization of antimicrobial resistance and virulence genes of Escherichia coli isolates from bovine mastitis

Background and Aim:

Mastitis is a common and economically important disease in dairy cattle. It remains one of the most common reasons for the extensive use of antimicrobials in dairy farms leading to the emergence of antimicrobial-resistant pathogens. The aim of this study was to determine the patterns of antimicrobial resistance of Escherichia coli isolates from bovine mastitis and to identify prominent antimicrobial resistance and virulence genes among isolated strains.

Materials and Methods:

Antimicrobial susceptibility testing against six antibiotic groups, including tetracyclines, aminoglycosides, beta-lactams, macrolides, sulfonamides, and fluoroquinolones was performed using the disk diffusion method. PCR was performed on resistant isolates to detect resistance and virulence genes using commercially available primers.

Results:

Out of 216 milk samples cultured, 14 samples yielded E. coli isolates. All isolates (100%) were resistant to ampicillin, amoxicillin, procaine penicillin, streptomycin, oxytetracycline, and sulfamethoxazole-trimethoprim. Only one isolate (7%) was sensitive to gentamicin, and all isolates (100%) were sensitive to enrofloxacin and ciprofloxacin. All isolates carried at least one resistance gene against one or more of the major antibiotic groups. All isolates carried the ereA, tetG, tetE, and tetB genes, followed by tetA (93%), ampC (86%), strA (86%), sul1 (78%), tetD (71%), tetC (57%), aadA (57%), and strB (36%). The lowest percentage of isolates carried bla1 (17%) and bla2 (12%) genes, and none of the isolates carried the qnrA gene. Most of the isolates (93%) carried the Shiga toxin 1 virulence gene, followed by complement resistance protein (79%), intimin (64%), Shiga toxin 2 (36%), cytotoxic necrotizing factor (35%), aerotaxis receptor (21%), and type 1 fimbriae (15%).

Conclusion:

Results of this study indicate that the high percentages of E. coli isolate from bovine mastitis are resistant to two or more of the major antibiotic groups, irrespective of the presence or absence of relevant resistance or virulence genes.

Genetic diversity, antimicrobial resistance and extended-spectrum β-lactamase type of Escherichia coli isolates from chicken, dog, pig and yak in Gansu and Qinghai Provinces, China

OBJECTIVES

In this study, the genetic diversity, phylogenetic grouping, antimicrobial resistance and extended-spectrum β-lactamase (ESBL) types of Escherichia coli isolates from chickens, dogs, pigs and yaks in six prefectures of Gansu and Qinghai Provinces, China, were investigated.

METHODS

E. coli was isolated from diarrhoeic and healthy faecal samples. Multilocus sequence typing (MLST), phylogenetic grouping, antimicrobial resistance and ESBL profiles were investigated.

RESULTS

A total of 142 MLST sequence types (STs) were identified from 400 E. coli isolates. eBURST clustering analysis resolved the 142 STs into 19 clonal complexes (CCs) and 67 singletons. PCR phylogenetic typing determined the isolation rate of potentially pathogenic B2/D group isolates among all E. coli to be 12.5% from healthy animal samples and 17.5% from diarrhoeic samples. Antimicrobial susceptibility testing revealed 78 antimicrobial resistance patterns. E. coli resistance rates were highest to doxycycline, ampicillin and tetracycline, whereas polymyxin B and meropenem had the lowest resistance rates. All polymyxin B-resistant E. coli isolates were positive for the mcr-1 gene. A total of 62 ESBL-producing isolates were identified. The ESBL prevalence was 55.0% in diarrhoeic samplings and 5.6% in healthy animals. TEM (82.3%) was the predominant ESBL type, followed by CTM (43.5%) and SHV (19.4%).

CONCLUSION

E. coli isolates in the study area have a high diversity of genetic and antimicrobial resistance patterns but a relatively low isolation rate of potentially pathogenic phylogroups. However, the somewhat high isolation rate of multidrug-resistant E. coli, particularly ESBL-producing isolates, requires continual surveillance of E. coli from animals in these areas.

Two Prevalent Listeria ivanovii subsp. ivanovii Clonal Strains With Different Virulence Exist in Wild Rodents and Pikas of China

Listeria ivanovii subsp. ivanovii is an intracellular bacterium distributed widely in nature, causing the listeriosis in ruminants and humans. Previous researches had isolated 116 strains of L. ivanovii subsp. ivanovii from wild rodents and pikas of different regions in China, and the predominant sequence types were ST1 and ST2. In this study, we first investigated the biological characteristics and virulence of these two clonal strains including motility, metabolism and virulence in cells and mouse model. The results demonstrated the ST1 strains exhibited motility, wide metabolic activity and hypervirulence, whereas the ST2 strains showed non-motility, relative lower metabolic activity and virulence. Considering the transmissible ability from wild rodents and pikas to ecological environment, the L. ivanovii subsp. ivanovii with potential pathogenicity to humans and ruminants should be monitored.

Agromyces badenianii sp. nov., isolated from plateau pika (Ochotona curzoniae)

Two aerobic, Gram-stain-positive, catalase-positive, non-motile and rod-shaped bacterial strains, designated MF30-A^T and MF845, were isolated from the intestinal contents of plateau pika collected from the Qinghai-Tibet Plateau. Optimal growth of these two strains was observed under aerobic conditions at pH 7.0 and 28 °C. The 16S rRNA gene sequences of the isolates had highest similarities of 98.5 and 98.4 % to Agromyces fucosus, respectively. In the 16S rRNA gene and polygenetic trees, strains MF30-A^T and MF845 were clearly distinct from other species. The two strains could not produce acid from arbutin, d-fructose, D-sucrose, glycogen, salicin or starch. Production of β-glucosidase by these strains was negative. The major fatty acids of these strains were anteiso-C_{15 : 0}, anteiso-C_{17 : 0} and iso-C_{16 : 0}. Strain MF30-A^T contained galactose, rhamnose and ribose as cell wall sugars and MK-12 and MK-11 as predominant menaquinones. The major polar lipids in strain MF30-A^T were diphosphatidylglycerol, phosphatidylglycerol and a glycolipid, while the peptidoglycan contained alanine, glutamic acid, glycine and 2,4-diaminobutyric acid. The G+C contents of the DNA of strains MF30-A^T and MF845 were 69.8 mol% and 69.7 mol%, respectively. The average nucleotide identity and digital DNA-DNA relatedness values of the two strains with all available genomes of the genus Agromyces were far below the respective thresholds of 95 and 70 %, respectively. All genotypic and phenotypic data indicated that strains MF30-A^T and MF845 should be classified as novel members of the genus Agromyces, for which the name Agromyces badenianii sp. nov. is proposed. The type strain is MF30-A^T (=CGMCC 1.16469^T=DSM 106183^T).

Escherichia coli strains producing a novel Shiga toxin 2 subtype circulate in China

Shiga toxin (Stx) is the key virulence factor in Shiga toxin producing Escherichia coli (STEC), which can cause diarrhea and hemorrhagic colitis with life-threatening complications. Stx comprises two toxin types, Stx1 and Stx2. Several Stx1/Stx2 subtypes have been identified in E. coli, which are variable in sequences, toxicity and host specificity. Here, we report the identification of a novel Stx2 subtype, designated Stx2k, in E. coli strains widely detected from diarrheal patients, animals, and raw meats in China over time. Stx2k exhibits varied cytotoxicity in vitro among individual strains. The Stx2k converting prophages displayed considerable heterogeneity in terms of insertion site, genetic content and structure. Whole genome analysis revealed that the stx_2k-containing strains were genetically heterogeneous with diverse serotypes, sequence types, and virulence gene profiles. The nine stx_2k-containing strains formed two major phylogenetic clusters closely with strains belonging to STEC, enterotoxigenic E. coli (ETEC), and STEC/ETEC hybrid. One stx_2k-containing strain harbored one plasmid-encoded heat-stable enterotoxin sta gene and two identical copies of chromosome-encoded stb gene, exhibiting STEC/ETEC hybrid pathotype. Our finding enlarges the pool of Stx2 subtypes and highlights the extraordinary genomic plasticity of STEC strains. Given the wide distribution of the Stx2k-producing strains in diverse sources and their pathogenic potential, Stx2k should be taken into account in epidemiological surveillance of STEC infections and clinical diagnosis.

High prevalence of non-O157 Shiga toxin-producing Escherichia coli in beef cattle detected by combining four selective agars

Background

Shiga toxin-producing Escherichia coli (STEC) are emerging foodborne pathogens that are public health concern. Cattle have been identified as the major STEC reservoir. In the present study, we investigated the prevalence and characteristics of STEC strains in beef cattle from a commercial farm in Sichuan province, China.

Results

Among 120 beef cattle fecal samples, stx genes were positive in 90% of samples, as assessed using TaqMan real-time PCR, and 87 (72.5%) samples were confirmed to yield at least one STEC isolate by culture using four selective agars, MacConkey, CHROMagar™ ECC, modified Rainbow® Agar O157, and CHROMagar™ STEC, from which 31, 32, 91, and 73 STEC strains were recovered, respectively. A total of 126 STEC isolates were selected and further characterized. Seventeen different O:H serotypes were identified, all of which belonged to the non-O157 serotypes. One stx₁ subtype (stx_1a) and three stx₂ subtypes (stx_2a, stx_2c, and stx_2d) were present among these isolates. The intimin encoding gene eae, and other adherence-associated genes (iha, saa, and paa) were present in 37, 125, 74, and 30 STEC isolates, respectively. Twenty-three isolates carried the virulence gene subA, and only one harbored both cnf1 and cnf2 genes. Three plasmid-origin virulence genes (ehxA, espP, and katP) were present in 111, 111, and 7 isolates, respectively. The 126 STEC isolates were divided into 49 pulsed-field gel electrophoresis (PFGE) patterns.

Conclusions

Our study showed that the joint use of the selective MacConkey and modified Rainbow® Agar O157 agars increased the recovery frequency of non-O157 STEC strains in animal feces, which could be applied to other samples and in regular STEC surveillance. Moreover, the results revealed high genetic diversity of non-O157 STEC strains in beef cattle, some of which might have the potential to cause human diseases.

Electronic supplementary material

The online version of this article (10.1186/s12866-019-1582-8) contains supplementary material, which is available to authorized users.

Identification and pathogenomic analysis of an Escherichia coli strain producing a novel Shiga toxin 2 subtype

Shiga toxin (Stx) is the key virulent factor in Shiga toxin-producing Escherichia coli (STEC). To date, three Stx1 subtypes and seven Stx2 subtypes have been described in E. coli, which differed in receptor preference and toxin potency. Here, we identified a novel Stx2 subtype designated Stx2h in E. coli strains isolated from wild marmots in the Qinghai-Tibetan plateau, China. Stx2h shares 91.9% nucleic acid sequence identity and 92.9% amino acid identity to the nearest Stx2 subtype. The expression of Stx2h in type strain STEC299 was inducible by mitomycin C, and culture supernatant from STEC299 was cytotoxic to Vero cells. The Stx2h converting prophage was unique in terms of insertion site and genetic composition. Whole genome-based phylo- and patho-genomic analysis revealed STEC299 was closer to other pathotypes of E. coli than STEC, and possesses virulence factors from other pathotypes. Our finding enlarges the pool of Stx2 subtypes and highlights the extraordinary genomic plasticity of E. coli strains. As the emergence of new Shiga toxin genotypes and new Stx-producing pathotypes pose a great threat to the public health, Stx2h should be further included in E. coli molecular typing, and in epidemiological surveillance of E. coli infections.

Prevalence, identification of virulence factors, O-serogroups and antibiotic resistance properties of Shiga-toxin producing Escherichia coli strains isolated from raw milk and traditional dairy products

Background

Shiga-toxigenic Escherichia coli strains are one of the most important foodborne bacteria with an emergence of antibiotic resistance. Foodborne STEC strains are mainly associated with presence of certain virulence factors and O-seogroups. The present investigation was done to study the distribution of virulence factors, O-serogroups and antibiotic resistance properties of Shiga-toxigenic Escherichia coli isolated from milk and dairy products.

Methods

Six-hundred samples were randomly collected and immediately transferred to laboratory. All samples were cultured and E. coli strains were isolated. STEC strains were identified based on the presence of putative virulence factors and subtypes. STEC isolates were subjected to multiplex PCR and disk diffusion methods.

Results

One-hundred and eighty-one out of 600 samples (30.16%) harbored E. coli. Prevalence of STEC strains was 10.66%. O157 (43.75%) and O26 (37.50%) were the most frequently identified serogroups. Aac(3)-IV (100%), CITM (96.87%) and tetA (76.56%) were the most commonly detected antibiotic resistance genes. STEC strains had the highest prevalence of resistance against ampicillin (100%), gentamicin (100%) and tetracycline (96.87%).

Conclusions

Kashk and dough were negative for presence of E. coli strains. High prevalence of resistant-O157 strains and simultaneous presence of multiple virulence factors pose an important public health problem regarding the consumption of raw milk and dairy products.

The first report of Cryptosporidium spp. in Microtus fuscus (Qinghai vole) and Ochotona curzoniae (wild plateau pika) in the Qinghai-Tibetan Plateau area, China

Cryptosporidium is one of the most important genera of intestinal zoonotic pathogens, which can infect various hosts and cause diarrhoea. There is little available information about the molecular characterisation and epidemiological prevalence of Cryptosporidium spp. in Microtus fuscus (Qinghai vole) and Ochotona curzoniae (wild plateau pika) in the Qinghai-Tibetan Plateau area of Qinghai Province, Northwest China. Therefore, the aim of this study was to determine Cryptosporidium species/genotypes and epidemiological prevalence in these mammals by detecting the SSU rRNA gene by PCR amplification. The Cryptosporidium spp. infection rate was 8.9% (8/90) in Qinghai voles and 6.25% (4/64) in wild plateau pikas. Positive samples were successfully sequenced, and the following Cryptosporidium species were found: C. parvum, C. ubiquitum, C. canis and a novel genotype in Qinghai voles and C. parvum and a novel genotype in wild plateau pikas. This is the first report of Cryptosporidium infections in M. fuscus and wild O. curzoniae in Northwest China. The results suggest the possibility of Cryptosporidium species transmission among these two hosts, the environment, other animals and humans and provide useful molecular epidemiological data for the prevention and control of Cryptosporidium infections in wild animals and the surrounding environments. The results of the present study indicate the existence of Cryptosporidium species infections that have potential public health significance. This is the first report of Cryptosporidium multi-species infections in these animal hosts.

Genetic diversity of the enterohaemolysin gene (ehxA) in non-O157 Shiga toxin-producing Escherichia coli strains in China

Non-O157 Shiga toxin-producing Escherichia coli (STEC) is increasingly recognized as an important enteric foodborne pathogen. The hallmark of the disease is the production of Shiga toxins; however, there are other virulence factors that contribute to the pathogenesis of STEC. This study aimed to investigate the prevalence and genetic diversity of the enterohaemolysin gene, ehxA, among non-O157 STEC strains from human, animal, and food sources. The ehxA gene was amplified from 138 (31.8%) of 434 non-O157 STEC strains, among which 36 unique ehxA sequences were identified. Based on ehxA sequence analysis, three phylogenetic ehxA groups (I II, and III) were determined. Correlations between ehxA groups and sources, serotypes, and virulent gene profiles were observed. The ehxA group II strains were mostly diarrhoeal patient-derived and may demonstrate higher pathogenic potential compared with the ehxA group I and group III strains. Five types of replicons (I1-Ig, FIB, K, F, and B/O) were identified in the 138 ehxA-positive strains, and 3.6%, 5.8%, and 52.2% of the strains harboured toxB, katP and espP genes, respectively, implying marked genetic diversity of ehxA containing plasmids in non-O157 STEC strains. Sequence-based ehxA genotyping might be important in modern strain typing and in epidemiological surveillance of non-O157 STEC infections.

Molecular and Phylogenetic Characterization of Non-O157 Shiga Toxin-Producing Escherichia coli Strains in China

Shiga toxin-producing Escherichia coli (STEC) causes diarrhea and hemorrhagic colitis with life-threatening complications, such as hemolytic uremic syndrome. The aim of this study was to assess the molecular epidemiologic features of non-O157 STEC strains from different resources in China and illustrate the role of animal reservoirs or animal-derived foodstuffs in human STEC infections. A collection of 301 non-O157 STEC isolates from domestic and wild animals (i.e., cattle, goat, pig, yak, pika, and antelope), raw meats (i.e., beef, pork, mutton, chicken, and duck), diarrheal patients, and healthy carriers in different regions of China were selected in this study. Of the 301 analyzed STEC isolates, 67 serogroups, and 118 serotypes were identified; this included some predominant serogroups associated with human disease, such as O26, O45, O103, O111, and O121. Eighteen different combinations of stx subtypes were found. Eleven isolates carried the intimin gene eae, 93 isolates contained ehxA, and 73 isolates carried astA. The prevalence of other putative adhesion genes saa, paa, efa1, and toxB was 28.90% (87), 6.98% (21), 2.31% (7), and 1% (3), respectively. The phylogenetic distribution of isolates was analyzed by multilocus sequence typing (MLST). Ninety-four sequence types were assigned across the 301 isolates. A subset of isolates recovered from yak and pika residing in the similar wild environments, Qinghai-Tibetan plateau, showed similar genetic profiles and more tendencies to cluster together. Isolates from goat and mutton exhibited close genetic relatedness with those from human-derived isolates, providing evidence that transmission may have occurred locally within intraspecies or interspecies, and importantly, from animal reservoirs, or raw meats to humans. Comparing isolates in this study with highly virulent strains by MLST, along with serotyping and virulence profiles, it is conceivable that some of isolates from goat, yak, or raw meats may have potential to cause human diseases.

Epidemiology and resistance features of Acinetobacter baumannii isolates from the ward environment and patients in the burn ICU of a Chinese hospital

Acinetobacter baumannii is an important opportunistic pathogen that causes severe nosocomial infections, especially in intensive care units (ICUs). Over the past decades, an everincreasing number of hospital outbreaks caused by A. baumannii have been reported worldwide. However, little attention has been directed toward the relationship between A. baumannii isolates from the ward environment and patients in the burn ICU. In this study, 88 A. baumannii isolates (26 from the ward environment and 62 from patients) were collected from the burn ICU of the Southwest Hospital in Chongqing, China, from July through December 2013. Antimicrobial susceptibility testing results showed that drug resistance was more severe in isolates from patients than from the ward environment, with all of the patient isolates being fully resistant to 10 out of 19 antimicrobials tested. Isolations from both the ward environment and patients possessed the β-lactamase genes bla OXA-51, bla OXA-23, bla AmpC, bla VIM, and bla PER. Using pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST), these isolates could be clustered into 4 major PFGE types and 4 main sequence types (ST368, ST369, ST195, and ST191) among which, ST368 was the dominant genotype. Epidemiologic and molecular typing data also revealed that a small-scale outbreak of A. baumannii infection was underway in the burn ICU of our hospital during the sampling period. These results suggest that dissemination of β-lactamase genes in the burn ICU might be closely associated with the high-level resistance of A. baumannii, and the ICU environment places these patients at a high risk for nosocomial infection. Cross-contamination should be an important concern in clinical activities to reduce hospitalacquired infections caused by A. baumannii.