The large plasmid carried class 1 integrons mediated multidrug resistance of foodborne Salmonella Indiana.

Salmonella enterica serovar Indiana (S. Indiana) has aroused widespread concern as an important zoonotic pathogen. The molecular mechanism of multidrug resistance (MDR) in S. Indiana is not known and should be assessed. We aim to investigate the molecular mechanism of MDR and the importance of large plasmids carried class 1 integrons in the MDR of foodborne S. Indiana. Class 1 integrons in 48 S. Indiana isolates and 200 isolates of 7 other Salmonella serotypes were detected by polymerase chain reaction (PCR). To analyze the antimicrobial resistance genes (ARGs) of two S. Indiana isolates, designated S. Indiana 15 and S. Indiana 222, next-generation sequencing (NGS) was performed, and the resulting sequences were compared with the complete nucleotide sequences of S. Indiana D90 and S. Indiana C629. Comparative functional analysis was conducted between the intI1 (1,014 bp) of S. Indiana 222 and the intI1 (699 bp) of S. Indiana 15. Plasmid conjugation transfer analysis was performed to analyze the horizontal gene transfer of the integrons-related resistance genes with integron-positive and integron-negative Salmonella isolates. 64.58% of S. Indiana isolates carried class 1 integrons, which was significantly higher than that of other Salmonella serotypes (p < 0.001). The NGS results showed that the S. Indiana 15 and S. Indiana 222 isolates carried a large plasmid with a class 1 integron and multiple ARGs, similar to S. Indiana D90 and S. Indiana C629. Two integrases found in S. Indiana isolates belong to class 1 integrases and could integrate resistance genes into specific integration sites of the integrons. The conjugation frequency of intI1 (1,014 bp) was 6.08 × 10-5, which was significantly higher than that of intI1 (699 bp) (p < 0.01). The large plasmids carrying a class 1 integron and the number of ARGs were strongly correlated (p < 0.001). The conjugation frequency of integron-positive S. Indiana recipient isolates was significantly higher than that of integron-negative recipient isolates (p < 0.05). S. Indiana containing large plasmids carrying a class 1 integron more easily captured resistance genes from other bacteria (S. Enteritidis and S. Derby), which could be an important cause of the emerging pandemic of MDR clones. Graphical abstractS. Indiana containing large plasmids carrying a class 1 integron more easily captured resistance genes from other bacteria (S. Enteritidis and S. Derby), which could be an important cause of the emerging pandemic of MDR clones.

Systematic evaluation of potential pathogenicity of Salmonella Indiana.

Salmonella Indiana has emerged in recent years as an important zoonotic pathogen, but its pathogenicity has not been fully elucidated. In this study, using in vivo and in vitro animal and cellular experimental model systems, we evaluated the pathogenicity of Salmonella Indiana (S. Indiana) compared with three other serotypes of Salmonella, S. Enteritidis, S. Typhimurium and S. Thompson. The animal experiments included observations of clinical symptoms, pathological changes and determination of median lethal dose in mice. The adhesion and invasiveness and intracellular proliferative capacity of Salmonella in vitro were measured with the murine macrophage-like cell line RAW264.7 cells and the human colon adenocarcinoma cell line Caco-2 cells. The results of animal experiments showed that S. Indiana, S. Enteritidis, S. Typhimurium and S. Thompson caused histopathological changes in most organs to varying degrees, primarily in the liver and intestine of mice. The gross lesions included white necrotic foci on the liver surface with different levels. The histopathological changes of monocyte/macrophage infiltration and coagulative necrosis were observed in the liver. Intestinal villi became short and were sloughed off, and lymphocyte infiltration was found in the submucosa. Compared with the other serotypes, the pathological changes caused by S. Indiana were slighter and had a relatively high median lethal dose in mice. The results of adhesion and invasion tests showed that the intracellular growth trend of most Salmonella strains was positively correlated with the number of pathogens adhering to and invading cells. Compared with the strains of the other three serotypes, most S. Indiana strains exhibited significantly lower adhesion and invasiveness to RAW264.7 and Caco-2 cells within 30 min. Most S. Indiana strains displayed twice to four times lower intracellular proliferation within 24 h in RAW264.7 cells. In conclusion, S. Indiana was pathogenic, but its pathogenicity was lower than that of S. Typhimurium and S. Enteritidis, and was similar to that of S. Thompson.

Combination of multilocus sequence typing and pulsed-field gel electrophoresis reveals an association of molecular clonality with the emergence of extensive-drug resistance (XDR) in Salmonella.

Salmonellae is one of the most important foodborne pathogens and becomes resistant to multiple antibiotics, which represents a significant challenge to food industry and public health. However, a molecular signature that can be used to distinguish antimicrobial resistance profile, particularly multi-drug resistance or extensive-drug resistance (XDR). In the current study, 168 isolates from the chicken and pork production chains and ill chickens were characterized by serotyping, antimicrobial susceptibility test, multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). The results showed that these isolates belonged to 13 serotypes, 14 multilocus sequence types (STs), 94 PFGE genotypes, and 70 antimicrobial resistant profiles. S. Enteritidis, S. Indiana, and S. Derby were the predominant serotypes, corresponding to the ST11, ST17, and ST40 clones, respectively and the PFGE Cluster A, Cluster E, and Cluster D, respectively. Among the ST11-S. Enteritidis (Cluster A) and the ST40-S. Derby (Cluster D) clones, the majority of isolates were resistant to 4-8 antimicrobial agents, whereas in the ST17S. Indiana (Cluster E) clone, isolates showed extensive-drug resistance (XDR) to 9-16 antimicrobial agents. The blaTEM-1-like gene was prevalent in the ST11 and ST17 clones corresponding to high ampicillin resistance. The blaTEM-1-like, blaCTX-M, blaOXA-1-like, sul1, aaC4, aac(6')-1b, dfrA17, and floR gene complex was highly prevalent among isolates of ST17, corresponding to an XDR phenotype. These results demonstrated the association of the resistant phenotypes and genotypes with ST clone and PFGE cluster. Our results also indicated that the newly identified gene complex comprising blaTEM-1-like, blaCTX-M, blaOXA-1-like, sul1, aaC4, aac(6')-1b, dfrA17, and floR, was responsible for the emergence of the ST17S. Indiana XDR clone. ST17 could be potentially used as a molecular signature to distinguish S. Indiana XDR clone.

Vibrio parahaemolyticus Strains of Pandemic Serotypes Identified from Clinical and Environmental Samples from Jiangsu, China.

Vibrio parahaemolyticus has emerged as a major foodborne pathogen in China, Japan, Thailand, and other Asian countries. In this study, 72 strains of V. parahaemolyticus were isolated from clinical and environmental samples between 2006 and 2014 in Jiangsu, China. The serotypes and six virulence genes including thermostable direct hemolysin (TDR) and TDR-related hemolysin (TRH) genes were assessed among the isolates. Twenty five serotypes were identified and O3:K6 was one of the dominant serotypes. The genetic diversity was assessed by multilocus sequence typing (MLST) analysis, and 48 sequence types (STs) were found, suggesting this V. parahaemolyticus group is widely dispersed and undergoing rapid evolution. A total of 25 strains of pandemic serotypes such as O3:K6, O5:K17, and O1:KUT were identified. It is worth noting that the pandemic serotypes were not exclusively identified from clinical samples, rather, nine strains were also isolated from environmental samples; and some of these strains harbored several virulence genes, which may render those strains pathogenicity potential. Therefore, the emergence of these "environmental" pandemic V. parahaemolyticus strains may poses a new threat to the public health in China. Furthermore, six novel serotypes and 34 novel STs were identified among the 72 isolates, indicating that V. parahaemolyticus were widely distributed and fast evolving in the environment in Jiangsu, China. The findings of this study provide new insight into the phylogenic relationship between V. parahaemolyticus strains of pandemic serotypes from clinical and environmental sources and enhance the MLST database; and our proposed possible O- and K- antigen evolving paths of V. parahaemolyticus may help understand how the serotypes of this dispersed bacterial population evolve.

Prevalence and diversity of enterotoxin genes with genetic background of Staphylococcus aureus isolates from different origins in China.

Staphylococcal enterotoxins (SE) induce toxin-mediated diseases, such as food poisoning. In the present study, 568 isolates from different sources were tested for the prevalence of 18 SE genes and performed spa typing. In addition, we characterized the relationships between the distribution of SE genes and molecular clones based on multilocus sequence typing (MLST), spa and staphylococcal cassette chromosome mec (SCCmec) typing in selected 250 isolates. Approximately 54.40% of the isolates from different sources harbored one or more SE genes forming 120 distinct gene profiles. Seven genes, sea, seb, seg, seo, sem, seq, and sel were more frequently detected. The distributions of the SE genes among the isolates from human, animals, and foodborne origins were highly different with isolates from environments (P<0.01). The classic SE genes in both foodborne and human origin isolates were significantly higher than that in animal origin isolates (P<0.01), whereas the prevalence of genes of egc cluster and the other genes was similar in human, animal, and foodborne origin isolates (P>0.05). We identified two important gene clusters, sea-sek-seq, which is closely related to hospital-acquired (HA) methicillin-resistant Staphylococcus aureus (MRSA)-III, and the egc cluster, which accounts for nearly half of all genes. Approximately 71% isolates could be typed by spa, yielding 103 spa types, of which 18 spa types were primary types. In clonal complex (CC) 239, an important Asian HA-MRSA-III clone from humans, nearly all isolates harbored complete or partial sea-sek-seq cluster; the main spa types were t030 and t037. In CC630, an important new community-associated (CA) MRSA-V CC in China, only sporadic SE genes, three main spa types, t4549, t2196, and t377 were observed. The egc cluster coexisting with other genes was present in isolates of CC5, CC9, CC1281, CC1301, CC30 and sequence type (ST) 25, but completely absent in isolates of CC239, CC59, CC7, and CC88. The results illustrate the genetic clonal diversity and the identity of S. aureus isolates from different sources with respect to SE genes and highlight a correlation between SE genes or gene clusters and CCs, spa, and MRSA clones. The foodborne and human origin isolates were the main potential causes of classic staphylococcal foodborne poisonings, whereas isolates harboring novel genes were new potential hazards to food safety.

Molecular epidemiological characteristics and clonal genetic diversity of Staphylococcus aureus with different origins in China.

To understand the intrinsic links and epidemic features of Staphylococcus aureus, isolates of this bacterium were collected from different origins in China. A total of 503 isolates from different sources were tested for the presence of methicillin-resistant Staphylococcus aureus (MRSA) and types of staphylococcal cassette chromosome mec (SCCmec) elements. Of these isolates, 250 were analyzed by multilocus sequence typing (MLST). Results showed that MRSA isolates account for 21.67% and have five types. SCCmec type I, II, and III isolates were all from humans, while SCCmec type IV, V, and untypeable MRSA isolates were from clinical origin, pigs, raw milk, or environments. The results by MLST showed considerable molecular heterogeneity in 52 different sequence types (STs) including 16 novel STs, which yielded 7 clonal complexes (CCs) and 5 doublets (Ds). The results from these analyses showed that hospital-acquired MRSA (HA-MRSA), rather than community-associated MRSA (CA-MRSA), remained the major pathogenic bacterium in the clinical setting. CA-MRSA infections have been increasing and forming new pandemic clones. CC630, CC239, D9, and D398 were important clones in this study. CC630 was a new epidemic CA clone circulating among humans, environments, and animals. CC239 was a HA-MRSA-III pandemic clone of clinical origin. The D9 clone was a livestock-associated (LA) clone, which up to now, has spread only in livestock and has not been found in humans that live in Jiangsu province. In Europe and America, there are many reports of the ST398-LA-clone in pigs and in humans who are in contact with pigs. However, various studies in China, including this one, indicate that the ST398 clone could be a CA clone rather than an LA clone. This clone also has been infecting humans for about 2 decades.

Phenotypic and genotypic characterization of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible Staphylococcus aureus (MSSA) from different sources in China.

A diverse collection of 261 Staphylococcus aureus strains from human, animal, food, and environmental sources were tested for the presence and type of SCCmec elements, antibiotic susceptibility to various antibiotics, and non-ß-lactam antibiotic resistance genes. About 18.39% (48/261) of strains were methicillin-resistant S. aureus (MRSA) including 29.75% (36/121) human strains of which 29 strains were hospital-acquired MRSA (HA-MRSA) and 7 strains were community-associated MRSA (CA-MRSA) and 19.67% (12/61) animal strains that all were CA-MRSA strains. The percentage of CA-MRSA strains from animals was significantly higher than that from human (p<0.01). Most of MRSA strains and a part of methicillin-susceptible S. aureus (MSSA) strains harbored unique combinations of non-ß-lactamase genes aac(6')/aph(2″), aph(3')-III, ant (4',4″), ermA, ermC, mrsA, tetM, and tetK. Antibiotic resistance genes were detected more frequently in HA-MRSA strains than in CA-MRSA strains (p<0.01). MRSA strains and MSSA strains had 22 and 39 antibiotic profiles to 15 tested antibiotics, respectively. The resistant proportion was higher in HA-MRSA strains than in CA-MSSA strains for various antibiotics, as well as higher in MRSA strains than in MSSA strains. Animal MRSA reservoirs (particularly pigs and cows) might represent an important source of human CA-MRSA. CA-MRSA strains might acquire more different resistance genes gradually, depending on the selective pressure of antibiotics in different regions or environments. CA-MRSA is not yet endemic in China, but could be prevalent in future, contributing to its acquiring more resistance genes and huge animal sources. Infection with multidrug-resistant MSSA strains acquired from food, animal, and human sources might also become a significant problem for human medicine, which warrants further study.

Origin of Vibrio parahaemolyticus O3:K6 pandemic clone.

O3:K6 pandemic clone of Vibrio parahaemolyticus has caused outbreaks in coastal countries since 1996. Mutilocus sequence typing (MLST) is an important tool to trace the source and analysis the evolution of bacteria. Based on MLST, the first pandemic clonal complex (CC) of V. parahaemolyticus has been confirmed. In this study, 57 pandemic strains, 27 pathogenic strains (tdh or trh positive) and 36 nonpathogenic strains isolated from China were analyzed with MLST. Forty-seven unique sequence types, one clonal complex (CC) and one doublet (D) were identified by eBURST and Mega4 analyses. CC corresponded to not only the known O3:K6 pandemic clone (including ST-3, ST-192, ST-227) but nonpathogenic clone (including ST-3, S-T2, ST-196, ST-220, ST-226). ST-3 was the founder of the complex. STs of the isolates were not inevitably associated with the presence or number of the accessory genes or the serotypes of the isolates. The ancestor strain of O3:K6 pandemic clone was originated from an environmental nonpathogenic O3:K6, ST-3 strain. The pandemic O3:K6 clone was developed from this strain in approximately 1996 by laterally transferring large fragments of genes including systematic functional genes and genomic islands.

Distribution of genes encoding four pathogenicity islands (VPaIs), T6SS, biofilm, and type I pilus in food and clinical strains of Vibrio parahaemolyticus in China.

Vibrio parahaemolyticus is a major cause of foodborne gastroenteritis in China, Japan, and other countries. The pandemic O3:K6 clone, which harbors thermostable direct hemolysin [tdh] gene and toxRS/new gene, is mainly responsible for the foodborne outbreaks after 1995. Previous studies showed that genes in the pathogenicity island-1 (VPaI-1) and VPaI-5 are harbored only by pandemic strains, whereas genes in VPaI-7 and type III secretion system 2 are closely associated with tdh-positive strains of V. parahaemolyticus. In this study, we examined the distribution of genes encoding VPaI-2, VPaI-3, VPaI-4, VPaI-6, type VI secretion systems (T6SS), biofilm, and type I pilus in 71 food and 116 clinical strains of V. parahaemolyticus. The results showed that most of the pandemic strains of V. parahaemolyticus harbored the complete genes of VPaI-2, T6SS, and type I pilus. In contrast, most of the pathogenic strains (harboring tdh gene or TDH-related hemolysin [trh] gene) and nonpathogenic strains (harboring neither tdh gene nor trh gene) contained partial genes of VPaI-2, T6SS, and type I pilus. Genes of VPaI-4 were exclusively present in the pandemic strains. Genes of VPaI-3 were present in most of the pandemic strains and a small percentage of nonpathogenic strains, mainly O3:K6 strains. VPaI-6 and biofilm-associated genes were harbored by almost all the strains, irrespective of their pandemic, pathogenic, or nonpathogenic traits.

Serodiversity, pandemic O3:K6 clone, molecular typing, and antibiotic susceptibility of foodborne and clinical Vibrio parahaemolyticus isolates in Jiangsu, China.

Vibrio parahaemolyticus is a major foodborne pathogen in China, Japan, and other Asian countries. In this study, we collected 437 strains of V. parahaemolyticus and investigated their serotypes, distribution of virulence genes, and presence of pandemic O3:K6 clone strains. A total of 327 strains were isolated from food and 110 strains were isolated from active surveillance hospitals or food outbreaks during 2005 to 2008. Presence of the tdh and trh genes is the key characteristic of virulent strains. Positive for both the tdh gene and group-specific polymerase chain reaction is the key characteristic of pandemic strains. A total of 9 O serogroups and 62 serovars were identified in all strains. Nine O serogroups and 56 serovars existed in 327 foodborne strains, and 6 O serogroups and 20 serovars existed in 110 clinical strains. Among the 327 food isolates, 6 isolates belonged to the pandemic clone with the orf8 gene (1 isolate was O1:KUT (untyped) and 5 isolates were O3:K6) and 4 isolates carried the trh gene (2 isolates belonged to O1:KUT and 2 isolates belonged to O5:KUT and O5:K17). Seventy-nine percent of the clinical isolates were pandemic strains, 9.4% of which lacked the orf8 gene. O3:K6 was the main serovar of the pandemic strains accounting for 83.5% of the clinical pandemic strains. Pandemic clonal serovars included O3:K6, O1:KUT, O1:K25, O1:K26, and O4:K68, and the newly emerging serovars O1:K36, O3:K25, and O3:K68 identified in the current study. O3:K6 was the dominant serovar in pandemic strains. All pandemic isolates had identical arbitrarily primed polymerase chain reaction fragment patterns, but did not share similar antibiotic sensitivity patterns. These results suggest that high serodiversity of V. parahaemolyticus was present in foodborne strains. Pathogenic isolates, especially pandemic isolates, were present in high-priced iced seafood and became the potential risk factor in food.

Predictive model of Vibrio parahaemolyticus growth and survival on salmon meat as a function of temperature.

The growth and survival curves of a strain of pandemic Vibrio parahaemolyticus TGqx01 (serotype O3:K6) on salmon meat at different storage temperatures (range from 0 degrees C to 35 degrees C) were determined. In order to model the growth or inactivation kinetics of this pathogen during storage, the modified Gompertz and Weibull equations were chosen to regress growth and survival curves, respectively, and both equations produced good fit to the observed data (the average R2 value equals to 0.990 for modified Gompertz and 0.920 for Weibull equation). The effect of storage temperature on the specific growth rate (mu) was modeled by square root type equation, and the relationship between mu and lag time (lambda) was described by a rule of mu x lambda = constant. The shape factor (n) and scale factor (b) values of the Weibull equations versus the temperature (degrees C) were plotted and the temperature effects on these parameters were described by two linear empirical equations. The predicted growth and survival curves from the model were compared to real enumeration results, using the correlation coefficient (R2), bias factor (Bf) and accuracy factor (Af), to assess the performance of the established model. The results showed that the overall predictions for V. parahaemolyticus TGqx01 growth or inactivation on salmon at tested temperatures agreed well with observed plate counts, and the average R2, Bf and Af values were 0.958, 1.019 and 1.035, respectively.

Systematic functional pandemic strain-specific genes, three genomic islands, two T3SSs in foodborne, and clinical Vibrio parahaemolyticus isolates in China.

Vibrio parahaemolyticus is one of the most important pathogens capable of causing foodborne gastroenteritis in China, Japan, and other countries. Pathogenic V. parahaemolyticus has been known to produce either thermostable direct hemolysin (TDH), TDH-related hemolysin (TRH), or both. The emergence of a new clone in 1995, V. parahaemolyticus O3:K6, has resulted in the first documented pandemic spread of V. parahaemolyticus. In this study, 235 isolates from clinical and food sources were characterized by determining the presence of known virulence factors (tdh, trh), systematic genetic markers (toxRS/new, pandemic group-specific sequence [PGS], orf8) specific for V. parahaemolyticus O3:K6 clone and its clonal derivatives, three important genomic islands (GIs) (VPaI-1, VPaI-5, and VPaI-7), and two type III secretion systems (T3SS1 and T3SS2). Our results showed that all 235 isolates harbored all or part of the T3SS1 genes. All the 103 tdh-positive strains harbored all or part of the VPaI-7 and T3SS2 genes. A total of 91 isolates including six foodborne isolates belonged to a pandemic clone in which eight isolates lacked orf8. All pandemic strains harbored VPaI-1 and VPaI-5 except one O4:K68 strain that lacked VPaI-5 altogether. Twelve clinical pathogenic strains had VPaI-7 and T3SS2 but lacked VPaI-1 and VPaI-5. Thirteen nonpathogenic clinical strains and 119 foodborne strains, including six foodborne pathogenic trh-positive strains, only harbored T3SS1 genes. These results indicated that O3:K6 and its serovariants were the main pandemic clone in China. VPaI-1 and VPaI-5 genes were specifically correlated with pandemic strains while VPaI-7 and T3SS2 were closely associated with tdh-positive strains.

[Isolation and identification of a Staphylococcus aureus small colony variants].

OBJECTIVE: Staphylococcus aureus small colony variants (S. aureus SCVs) could lead to persistent, recurrent infection with the characteristics of aminoglycosides antibiotics resistance, making them a big challenge for clinical diagnosis and therapy. We aimed at isolating and identifying isolates of S. aureus SCVs and providing the biological material of SCVs study in China. METHODS: The combination assays of observing colony phenotype, identification of the species-specific gene nuc of S. aureus by PCR amplification and a series of biochemical tests were conducted on 104 clinical isolates originally isolated from human, cow and environment. The suspected isolates were confirmed as S. aureus SCVs by complementation assay with supplementation of menadione, thiamine, thymine and haemin. RESULTS: One of the isolates from environment was identified as SCVs, named CDC54 with the species-specific gene nuc of Staphylococcus aureus (S. aureus) confirmed by PCR amplification, whose major phenotypes included smaller colony, decreased pigmentation, decreased coagulase, reduced fermentation of lactose, decreased haemolytic activity, increased resistance to aminoglycosides. CONCLUSION: The CDC54 will play an important role in studying prevention, control and pathogenesis for S. aureus SCVs infection.

Prevalence and antimicrobial resistance of foodborne pathogens isolated from food products in China.

This study was undertaken to investigate the prevalence of Salmonella, Listeria monocytogenes, Staphylococcus aureus, Vibrio parahaemolyticus, and Escherichia coli O157:H7 in Chinese food products. The prevalence of these pathogens was 3.46%, 5.79%, 7%, 0.24%, and 0%, respectively. Raw meats were mainly contaminated with Salmonella (39/365, 10.7%), L. monocytogenes (26/365, 7.1%), and S. aureus (40/365, 11%), while cooked food products were mainly contaminated with L. monocytogenes (45/384, 11.7%) followed by S. aureus (12/384, 3.1%), and raw milk was mainly contaminated with S. aureus (34/209, 16.3%) and Salmonella (4/209, 1.9%). Antimicrobial resistance was evaluated in Salmonella, L. monocytogenes, and S. aureus. Antimicrobial resistance for L. monocytogenes was most frequently observed for cefotaxime (51/72, 70.8%) followed by furazolidone (40/72, 55.6%). Multiple resistance (resistance to >or=2 antibiotics) was observed for 63.9% (46/72) of L. monocytogenes isolates. Resistance of Salmonella was most frequently observed to amoxicillin (11.6%), ticarcilline (11.6%), cephalothin (11.6%), and cefuroxime (11.6%). Multiple resistance was observed for 16.3% (7/43) of the Salmonella isolates. Staphylococcus aureus was resistant to penicillin (93.1%) followed by tetracycline and oxacillin COAG (49.4% and 37.9%, respectively). About 79% (69/87) of S. aureus isolated demonstrated multiple resistance. The data showed that raw meat, cooked food products, and raw milk were most commonly contaminated with foodborne pathogens and many pathogens were resistant to different antibiotics. The study provided useful information for assessment of the possible risk posed to Chinese consumers, which has significant public health impact in China.

[Analysis of correlation factors affecting the incidence of burn shock].

OBJECTIVE: To analyze the correlation factors affecting the incidence of burn shock, so as to provide guidance for the clinical treatment of shock after burns. METHODS: Retrospective analysis of clinical data of 15 624 patients hospitalized in our department from 1973 to 2005 was undertaken . The incidence of shock during every 10 years, as well as the relationship between shock incidence and age, burn area, interval between injury and hospitalization, and complications were analyzed statistically. RESULTS: The incidence of shock during 1973-1980, 1981-1990, 1991-2000 and 2001-2005 periods was 14.69%, 13.50%, 9.38% and 7.88%, respectively, and there was significant difference of shock incidence between each 10 years and its succeeding period (P < 0.01). The occurrence of shock was closely related to age, length of time between injury and hospitalization, and burn area. The shock incidence of children under 7 years old or elderly more than 60 years old was obviously higher than other age groups, and there was positive relationship between burn area and shock incidence. Moreover, the shock incidence of the patients hospitalized later than 4 to 12 hours after burn shock was also markedly higher than those hospitalized earlier (P < 0.01). In addition, the incidence of sepsis, alimentary tract hemorrhage, acute renal failure, pulmonary failure, and cardiac failure in patients with shock was obviously higher than those without shock (P < 0.01). CONCLUSION: For the children and aged people, special attention should be paid in the prevention and resuscitation of burn shock. Early fluid resuscitation is vital for the prevention of organ complication, and it is beneficial to promote wound healing.