Epidemiological trends in serotypes distribution and antimicrobial resistance in Salmonella from humans in Taiwan, 2004-2022.

Objectives: Salmonella, a zoonotic pathogen, significantly impacts global human health. Understanding its serotype distribution and antimicrobial resistance is crucial for effective control measures and medical interventions. Methods: We collected Salmonella isolates and demographic data from Taiwanese hospitals between 2004 and 2022, analyzing their serotypes and antimicrobial susceptibility. Results: Among 40,595 isolates, salmonellosis predominated in children aged 0-4 (61.2%) years and among males (55.2%). Males also showed higher rates of extraintestinal infections (18.1% vs 16.0%, P <0.001), particularly, in the ≥65 years age group (52.4%). The top five serovars were S. Enteritidis (32.8%), S. Typhimurium (21.7%), S. Newport (6.2%), S. Stanley (4.7%), and S. Anatum (4.0%). Notably, S. Enteritidis prevalence increased from 23.9% (2004-2005) to 43.6% (2021-2022). Antimicrobial resistance was high, with a 51.6% multidrug resistance (MDR) rate. Disturbingly, MDR rates exceeded 90% in serovars Albany, Schwarzengrund, Choleraesuis, and Goldcoast. Resistance to key therapeutic agents, azithromycin, cefotaxime, and ciprofloxacin, exhibited concerning upward trends, and the surge in cefotaxime and ciprofloxacin resistance was closely linked to the emergence and spread of MDR S. Anatum and S. Goldcoast clones. Conclusions: Prioritizing control measures against S. Enteritidis and closely monitoring the prevalence and spread of MDR clones are imperative to mitigate Salmonella infections in Taiwan.

Antimicrobial resistance and genetic relatedness among Campylobacter coli and Campylobacter jejuni from humans and retail chicken meat in Taiwan.

OBJECTIVES: Campylobacter is a significant zoonotic pathogen primarily transmitted through poultry. Our study aimed to assess antimicrobial resistance and genetic relationships among Campylobacter isolates from retail chicken meat and humans in Taiwan. METHODS: Campylobacter isolates were analysed using whole-genome sequencing to investigate their antimicrobial resistance, genetic determinants of resistance, and genotypes. RESULTS: Campylobacter coli and Campylobacter jejuni accounted for 44.9% and 55.1% of chicken meat isolates, and 11.4% and 88.6% of human isolates, respectively. C. coli displayed significantly higher resistance levels. Furthermore, isolates from chicken meat exhibited higher levels of resistance to most tested antimicrobials compared to isolates from humans. Multidrug resistance was observed in 96.3% of C. coli and 43.3% of C. jejuni isolates from chicken meat and 80.6% of C. coli and 15.8% of C. jejuni isolates from humans. Macrolide resistance was observed in 85.5% of C. coli isolates, primarily attributed to the erm(B) rather than the A2075G mutation in 23S rRNA. Among the 511 genomes, we identified 133 conventional MLST sequence types, indicating significant diversity among Campylobacter strains. Notably, hierarchical Core-genome multilocus sequence typing clustering, including HC0, HC5, and HC10, revealed a significant proportion of closely related isolates from chicken meat and humans. CONCLUSIONS: Our research highlights significant associations in antimicrobial resistance and genetic relatedness between Campylobacter isolates from chicken meat and humans in Taiwan. The genetic analysis data suggest that campylobacteriosis outbreaks may occur more frequently in Taiwan than previously assumed. Our study emphasizes the need for strategies to control multidrug-resistant strains and enhance outbreak prevention.

Shigellosis in Taiwan: An old enteric pathogen with changing epidemiology and increasing antimicrobial resistance.

While the incidence of shigellosis has decreased in developed nations due to improved living conditions and healthcare systems, it remains prevalent in economically developing regions. In recent years, a resurgence of shigellosis has been observed in the United States, Europe, and Taiwan, primarily among men having sex with men and people living with human immunodeficiency virus, along with a rise in antimicrobial resistance. This study aims to review the historical epidemiological trends and drug resistance in shigellosis, with a focus on Taiwan. A comprehensive search was conducted using various databases and sources, including non-English literature in Japanese and Chinese. In developed countries, Shigella sonnei and Shigella flexneri are the most common species, while Shigella dysenteriae infections are sporadic. In Taiwan, the classification and prevalence of Shigella species have evolved over time, with S. flexneri and S. sonnei being the predominant strains. Fluoroquinolone resistance and azithromycin non-susceptibility are the ongoing threat. In conclusion, shigellosis remains a significant global health concern, with recent increases in certain populations and antimicrobial resistance. Further research is necessary to understand the clinical significance and risk factors associated with asymptomatic carriers and to assess the impact of behavioral modifications and interventions in high-risk populations.

Epidemiological trends and antimicrobial resistance in Salmonella enterica serovar Typhimurium clones in Taiwan between 2004 and 2019.

OBJECTIVES: We investigated the temporal trends of Salmonella enterica serovar Typhimurium (S. Typhimurium) clones in Taiwan from 2004 to 2019, focusing on antimicrobial resistance (AMR), resistance genetic determinants, and plasmid types. METHODS: Salmonella isolates were characterized using pulsed-field gel electrophoresis (PFGE), whole-genome sequencing, and antimicrobial susceptibility testing. Clones were defined using PFGE clustering and the hierarchical cgMLST clustering (HierCC) assignments. RESULTS: Seven major S. Typhimurium clones, HC100_2, 13, 41, 305, 310, 501, and 46261, accounted for 97.6% (8079/8275) of human isolates in Taiwan. Each clone displayed a unique AMR profile, resistance genetic determinants, and plasmid types. Four highly resistant clones (HC100_2, 41, 305, and 310) exhibited multiple resistance in 86.5% to 96.1% of isolates. HC100_305 and HC100_2 were pandemic multidrug-resistant clones, characterized by resistance to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline (ACSSuT) and ASSuT, respectively. The prevalence of the ACSSuT clone decreased from 68.7% of S. Typhimurium isolates in 2004 to 1.7% in 2019, while the ASSuT clone emerged in 2007 and became the largest clone after 2010. Several plasmids, including IncHI2-IncHI2A, IncC, IncFIB(K), and IncI1-1(α), carried multiple resistance genes or were associated with the carriage of mph(A), blaCMY-2, and blaDHA-1. CONCLUSIONS: Between 2004 and 2019, Taiwan experienced the emergence, prevalence, and subsequent decline of several highly resistant S. Typhimurium clones. The clones defined using the HierCC approach have global comparability. The increasing resistance to third-generation cephalosporins, cephamycins, ciprofloxacin, and azithromycin in recent years poses a significant medical concern.

Chromosome-Borne CTX-M-65 Extended-Spectrum ß-Lactamase-Producing Salmonella enterica Serovar Infantis, Taiwan.

A CTX-M-65‒producing Salmonella enterica serovar Infantis clone, probably originating in Latin America and initially reported in the United States, has emerged in Taiwan. Chicken meat is the most likely primary carrier. Four of the 9 drug resistance genes have integrated into the chromosome: blaCTX-M-65, tet(A), sul1, and aadA1.

Antimicrobial Resistance and Mechanisms of Azithromycin Resistance in Nontyphoidal Salmonella Isolates in Taiwan, 2017 to 2018.

Antimicrobial resistance was investigated in 2,341 nontyphoidal Salmonella (NTS) isolates recovered from humans in Taiwan from 2017 to 2018 using antimicrobial susceptibility testing. Azithromycin resistance determinants were detected in 175 selected isolates using PCR and confirmed in 81 selected isolates using whole-genome sequencing. Multidrug resistance was found in 47.3% of total isolates and 96.2% of Salmonella enterica serovar Anatum and 81.7% of S. enterica serovar Typhimurium isolates. Resistance to the conventional first-line drugs (ampicillin, chloramphenicol, and cotrimoxazole), cefotaxime and ceftazidime, and ciprofloxacin was found in 32.5 to 49.0%, 20.3 to 20.4%, and 3.2% of isolates, respectively. A total of 76 (3.1%) isolates were resistant to azithromycin, which was associated with mph(A), erm(42), erm(B), and possibly the enhanced expression of efflux pump(s) due to ramAp or defective ramR. mph(A) was found in 53% of the 76 azithromycin-resistant isolates from 11 serovars and located in an IS26-mph(A)-mrx(A)-mphR(A)-IS6100 unit in various incompatibility plasmids and the chromosomes. erm(42) in S. enterica serovar Albany was carried by an integrative and conjugative element, ICE_erm42, and in S. enterica serovar Enteritidis and S. Typhimurium was located in IS26 composite transposons in the chromosomes. erm(B) was carried by IncI1-I(α) plasmids in S. Enteritidis and S. Typhimurium. ramAp was a plasmid-borne ramA, a regulatory activator of efflux pump(s), found in only S. enterica serovar Goldcoast. Since the azithromycin resistance determinants are primarily carried on mobile genetic elements, they could easily be disseminated among human bacterial pathogens. The ramAp-carrying S. Goldcoast isolates displayed azithromycin MICs of 16 to 32 mg/L. Thus, the epidemiological cutoff value of ≤16 mg/L of azithromycin proposed for wild-type NTS should be reconsidered. IMPORTANCE Antimicrobial resistance in NTS isolates is a major public health concern in Taiwan, and the mechanisms of azithromycin resistance are rarely investigated. Azithromycin and carbapenems are the last resort for the treatment of invasive salmonellosis caused by multidrug-resistant (MDR) and extensively drug-resistant Salmonella strains. Our study reports the epidemiological trend of resistance in NTS in Taiwan and the genetic determinants involved in azithromycin resistance. We point out that nearly half of NTS isolates from 2017 to 2018 are MDR, and 20% are resistant to third-generation cephalosporins. The azithromycin resistance rate (3.1%) for the NTS isolates from Taiwan is much higher than those for the NTS isolates from the United States and Europe. Our study also indicates that azithromycin resistance is primarily mediated by mph(A), erm(42), erm(B), and ramAp, which are frequently carried on mobile genetic elements. Thus, the azithromycin resistance determinants could be expected to be disseminated among diverse bacterial pathogens.

Genomic Surveillance of Listeria monocytogenes in Taiwan, 2014 to 2019.

Listeria monocytogenes is a life-threatening foodborne pathogen. Here, we report the genomic characterization of a nationwide dataset of 411 clinical and 82 food isolates collected in Taiwan between 2014 and 2019. The observed incidence of listeriosis increased from 0.83 to 7 cases per million population upon implementation of mandatory notification in 2018. Pregnancy-associated cases accounted for 2.8% of human listeriosis and all-cause 7-day mortality was of 11.9% in nonmaternal-neonatal listeriosis. L. monocytogenes was isolated from 90% of raw pork and 34% of chicken products collected in supermarkets. Sublineages SL87, SL5, and SL378 accounted for the majority (65%) of clinical cases. SL87 and SL378 were also predominant (57%) in food products. Five cgMLST clusters accounted for 57% clinical cases, suggesting unnoticed outbreaks spanning up to 6 years. Mandatory notification allowed identifying the magnitude of listeriosis in Taiwan. Continuous real-time genomic surveillance will allow reducing contaminating sources and disease burden. IMPORTANCE Understanding the phylogenetic relationship between clinical and food isolates is important to identify the transmission routes of foodborne diseases. Here, we performed a nationwide study between 2014 and 2019 of both clinical and food Listeria monocytogenes isolates and sequenced their genomes. We show a 9-fold increase in listeriosis reporting upon implementation of mandatory notification. We found that sublineages SL87 and SL378 predominated among both clinical (50%) and food (57%) isolates, and identified five cgMLST clusters accounting for 57% of clinical cases, suggestive of potential protracted sources of contamination over up to 6 years in Taiwan. These findings highlight that mandatory declaration is critical in identifying the burden of listeriosis, and the importance of genome sequencing for a detailed characterization of the pathogenic L. monocytogenes genotypes circulating in Asia.

Demographic Features of Invasive Meningococcal Disease in Taiwan, 1993 to 2020, and Genetic Characteristics of Neisseria meningitidis Isolates, 2003 to 2020.

We present the demographic features of invasive meningococcal disease (IMD) in Taiwan between 1993 and 2020 and the genetic characteristics of Neisseria meningitidis isolates recovered from 2003 to 2020. IMD was rare in Taiwan between 1993 and 2020, with an annual incidence ranging from 0.009 to 0.204 per 100,000 people. The case fatality rate (CFR) declined from 18.1% for patients in 1993 to 2002 to 9.8% in 2003 to 2020. Infants less than 12 months were most susceptible to the disease. N. meningitidis serogroup B (NmB) was most predominant, responsible for 81.2% (134/165) of the IMD cases in 2003 to 2020. The majority of the isolates recovered from 2003 to 2020 belonged to 4 worldwide-spread hyperinvasive clonal complexes (cc), cc4821 (30.3%), cc32 (19.4%), cc41/44 (12.7%), cc23 (7.3%), and also a newly assigned clonal complex, cc3439 (10.3%). Core genome multilocus sequence typing (cgMLST) profile comparisons revealed that the cc4821 isolates with a T-to-I substitution at position 91 in gyrA were closely related to those originating from China. Of the 165 isolates, 20.0% and 53.3% were predicted to be covered by the Bexsero and Trumenba vaccines, respectively, whereas, 77.0% and 46.7% remained indeterminate. In conclusion, N. meningitidis isolates recovered in Taiwan between 2003 and 2020 were mostly highly diverse. Most IMD cases appeared sporadically and were caused by localized strains, although some patients were infected by recently introduced strains. cgMLST is a powerful tool for the rapid comparison of genetic relatedness among a large number of isolates. cgMLST profiling, based on 1,241 core genes, and strain tracking can be performed on the website of cgMLST@Taiwan (http://rdvd.cdc.gov.tw/cgMLST/). IMPORTANCE N. meningitidis can cause life-threatening invasive meningococcal disease (IMD), including meningitis and sepsis, resulting in a high CFR and long-term sequelae in survivors. Here, we report the demographic features of IMD in Taiwan over a 28-year period (1993 to 2020) and the genetic characteristics of N. meningitidis isolates recovered from patients with IMD over an 18-year period (2003 to 2020). We conducted a whole-genome sequence analysis to characterize the genetic features of the isolates and developed a cgMLST scheme for epidemiological investigation and strain tracking. The findings can be beneficial in understanding the epidemiology of IMD in Taiwan, the genetic characteristics of the bacterial strains, and the distribution of vaccine antigens for vaccine development and implementation.

Changing epidemiology of shigellosis in Taiwan, 2010-2019: an emerging threat to HIV-infected patients and men who have sex with men.

Shigellosis appears to increase in certain at-risk populations in developed countries. Based on the nationwide surveillance, the annual incidence of shigellosis in Taiwan (1999-2019) was 0.38-5.77 cases per 100,000 people. Indigenous shigellosis has mostly affected men who have sex with men (MSM) and people living with HIV (PLWH) since 2015. In this retrospective study, compared with those diagnosed before 2015, indigenous cases diagnosed during 2015-2019 mostly occurred in male adults (96.0% vs 47.1%, P < 0.001), with a longer hospital stay (median 5.0 vs 3.5 days, P = 0.029) and different coinfections. The predominant strains in 2015 and 2016 were ciprofloxacin-resistant Shigella sonnei and azithromycin non-susceptible Shigella flexneri (S. flexneri) 3a, which had been replaced by ciprofloxacin-resistant S. flexneri 2a since 2018. Notably, six indigenous cases were caused by cefotaxime-resistant S. flexneri. Inappropriate use of empiric antibiotic treatment was common. In conclusion, there is an ongoing spread of ciprofloxacin-resistant shigellosis among PLWH and MSM and cefotaxime-resistant S. flexneri is an emerging threat in Taiwan.

Antimicrobial Resistance in Campylobacter coli and Campylobacter jejuni from Human Campylobacteriosis in Taiwan, 2016 to 2019.

Campylobacter coli and Campylobacter Jejuni are highly resistant to most therapeutic antimicrobials in Taiwan; rapid diagnostics of resistance in bacterial isolates is crucial for the treatment of campylobacteriosis. We characterized 219 (40 C. coli and 179 C. jejuni) isolates recovered from humans from 2016 to 2019 using whole-genome sequencing to investigate the genetic diversity among isolates and the genetic resistance determinants associated with antimicrobial resistance. Susceptibility testing with 8 antimicrobials was conducted to assess the concordance between phenotypic resistance and genetic determinants. The conventional and core genome multilocus sequence typing analysis revealed diverse clonality among the isolates. Mutations in gyrA (T86I, D90N), rpsL (K43R, K88R), and 23S rRNA (A2075G) were found in 91.8%, 3.2%, and 6.4% of the isolates, respectively. The horizontally transferable resistance genes ant(6)-I, aad9, aph(3')-IIIa, aph(2″), blaOXA, catA/fexA, cfr(C), erm(B), lnu, sat4, and tet were identified in 24.2%, 21.5%, 33.3%, 11.9%, 96.3%, 10.0%, 0.9%, 6.8%, 3.2%, 13.2%, and 96.3%, respectively. High-level resistance to 8 antimicrobials in isolates was 100% predictable by the known resistance determinants, whereas low-level resistance to azithromycin, clindamycin, nalidixic acid, ciprofloxacin, and florfenicol in isolates was associated with sequence variations in CmeA and CmeB of the CmeABC efflux pump. Resistance-enhancing CmeB variants were identified in 62.1% (136/219) of isolates. In conclusion, an extremely high proportion of C. coli (100%) and C. jejuni (88.3%) were multidrug-resistant, and a high proportion (62.5%) of C. coli isolates were resistant to azithromycin, erythromycin, and clindamycin, which would complicate the treatment of invasive campylobacteriosis in this country.

Investigation of a salmonellosis outbreak linked to French toast sandwich with the use of surveillance camera, Taiwan, 2018.

Salmonella is a leading cause of foodborne outbreaks in Taiwan. On 27 April 2018, a salmonellosis outbreak among customers of a restaurant was reported to the Taiwan CDC. We investigated the outbreak to identify infection sources and prevent further transmission. We interviewed ill customers and their dining companions. We conducted a case-control study to identify foods associated with the illness. Case-patients were those who had diarrhoea within 72 h after eating at the restaurant during 16-27 April 2018. Specimens, food samples and environmental samples were collected and tested for enteric pathogens. Salmonella isolates were analysed with pulse-field gel electrophoresis and whole-genome sequencing. We inspected the restaurant sanitation and reviewed kitchen surveillance camera recordings. We identified 47 case-patients, including one decedent. Compared with 44 controls, case-patients were more likely to have had a French toast sandwich (OR: 102.4; 95% CI: 18.7-952.3). Salmonella Enteritidis isolates from 16 case-patients shared an indistinguishable genotype. Camera recordings revealed eggshell contamination, long holding time at room temperature and use of leftovers during implicated food preparation. Recommendations for restaurant egg-containing food preparation are to use pasteurised egg products and ensure a high enough cooking temperature and long enough cooking time to prevent Salmonella contamination.

Emergence of Vibrio cholerae O1 Sequence Type 75 in Taiwan.

We investigated the epidemiology of cholera in Taiwan during 2002-2018. Vibrio cholerae sequence type (ST) 75 clone emerged in 2009 and has since become more prevalent than the ST69 clone from a previous pandemic. Closely related ST75 strains have emerged in 4 countries and may now be widespread in Asia.

Emergence of Multidrug-Resistant Salmonella enterica Serovar Goldcoast Strains in Taiwan and International Spread of the ST358 Clone.

Salmonella enterica serovar Goldcoast infection was rare in Taiwan; it was not detected in routine surveillance from 2004 to 2013. This serovar was first identified in 2014, but the frequency of infection remained low until 2017. From 2014 to 2016, all but one isolate was pan-susceptible. S Goldcoast infections abruptly increased in 2018, and all isolates were multidrug-resistant (MDR). All MDR isolates harbored an IncHI2 plasmid, and the majority carried 14 antimicrobial resistance genes, aac(3)-IId, aadA22, aph(3')-Ia, aph(6)-Id, blaTEM-1B, blaCTX-M-55, lnu(F), floR, qnrS13, arr-2, sul2, sul3, tet(A), and dfrA14. S Goldcoast strains recovered in Taiwan and 96 of 99 strains from Germany, the Netherlands, the United Kingdom, and the United States belonged to sequence type 358 (ST358). Whole-genome single-nucleotide polymorphism and core genome multilocus sequence type analyses revealed that all strains of the ST358 clone shared a high degree of genetic relatedness. The present study highlighted that a dramatic increase in S Goldcoast infections followed the emergence of MDR strains and indicated that a genetically closely related S Goldcoast ST358 clone may have widespread significance internationally.

New Multidrug-Resistant Salmonella enterica Serovar Anatum Clone, Taiwan, 2015-2017.

In 2011, a Salmonella enterica serovar Anatum clone emerged in Taiwan. During 2016-2017, infections increased dramatically, strongly associated with emergence and spread of multidrug-resistant strains with a plasmid carrying 11 resistance genes, including blaDHA-1. Because these resistant strains infect humans and food animals, control measures are urgently needed.

Genetic Relationships among Multidrug-Resistant Salmonella enterica Serovar Typhimurium Strains from Humans and Animals.

We identified 20 to 22 resistance genes, carried in four incompatibility groups of plasmids, in each of five genetically closely related Salmonella enterica serovar Typhimurium strains recovered from humans, pigs, and chickens. The genes conferred resistance to aminoglycosides, chloramphenicol, sulfonamides, trimethoprim, tetracycline, fluoroquinolones, extended-spectrum cephalosporins and cefoxitin, and azithromycin. This study demonstrates the transmission of multidrug-resistant Salmonella strains among humans and food animals and may be the first identification of mphA in azithromycin-resistant Salmonella strains in Taiwan.

Dissemination of mcr-1-Carrying Plasmids among Colistin-Resistant Salmonella Strains from Humans and Food-Producing Animals in Taiwan.

We detected the colistin resistance gene mcr-1 in four Salmonella serovars isolated from humans and animals with diarrhea. The resistance gene was carried on different plasmids. One mcr-1-carrying conjugative plasmid, a variant of pHNSHP45, was disseminated among Salmonella isolates recovered from humans, pigs, and chickens.

Azithromycin-Nonsusceptible Shigella flexneri 3a in Men Who Have Sex with Men, Taiwan, 2015-2016.

We report an outbreak of azithromycin-nonsusceptible Shigella flexneri 3a infection in Taiwan associated with men who have sex with men. The bacterial strains belonged to the sublineage A of a recently reported outbreak lineage associated with men who have sex with men, characterized by reduced azithromycin susceptibility and circulation in shigellosis low-risk regions.

Usefulness of pulsed-field gel electrophoresis profiles for the determination of Salmonella serovars.

We created a database consisting of a large number of Salmonella pulsed-field gel electrophoresis (PFGE) profiles covering a wide range of different serovars. This database was used for the prediction of the serovars based on the PFGE profiles for isolates from Taiwan and Denmark. The PFGE profiles proved very useful in the determination of a serovar although serovar prediction was more efficient for local isolates than those from a distant geographic area. To use a highly stringent band matching tolerance in the BioNumerics software is also important for the grouping of serovars.

An association of genotypes and antimicrobial resistance patterns among Salmonella isolates from pigs and humans in Taiwan.

We collected 110 Salmonella enterica isolates from sick pigs and determined their serotypes, genotypes using pulsed-field gel electrophoresis (PFGE), and antimicrobial susceptibility to 12 antimicrobials and compared the data with a collection of 18,280 isolates obtained from humans. The pig isolates fell into 12 common serovars for human salmonellosis in Taiwan; S. Typhimurium, S. Choleraesuis, S. Derby, S. Livingstone, and S. Schwarzengrund were the 5 most common serovars and accounted for a total of 84% of the collection. Of the 110 isolates, 106 (96%) were multidrug resistant (MDR) and 48 (44%) had PFGE patterns found in human isolates. S. Typhimurium, S. Choleraesuis, and S. Schwarzengrund were among the most highly resistant serovars. The majority of the 3 serovars were resistant to 8-11 of the tested antimicrobials. The isolates from pigs and humans sharing a common PFGE pattern displayed identical or very similar resistance patterns and Salmonella strains that caused severe infection in pigs were also capable of causing infections in humans. The results indicate that pigs are one of the major reservoirs to human salmonellosis in Taiwan. Almost all of the pig isolates were MDR, which highlights the necessity of strictly regulating the use of antimicrobials in the agriculture sector in Taiwan.

Protein interactions and regulation of EscA in enterohemorrhagic E. coli.

Infections caused by enterohemorrhagic Escherichia coli (EHEC) can lead to diarrhea with abdominal cramps and sometimes are complicated by severe hemolytic uremic syndrome. EHEC secretes effector proteins into host cells through a type III secretion system that is composed of proteins encoded by a chromosomal island, locus for the enterocyte effacement (LEE). EspA is the major component of the filamentous structure connecting the bacteria and the host's cells. Synthesis and secretion of EspA must be carefully controlled since the protein is prone to polymerize. CesAB, CesA2, and EscL have been identified as being able to interact with EspA. Furthermore, the intracellular level of EspA declines when cesAB, cesA2, and escL are individually deleted. Here, we report a LEE gene named l0033, which also affects the intracellular level of EspA. We renamed l0033 as escA since its counterpart in enteropathogenic E. coli has been recently described. Similar to CesAB, EscL, and CesA2, EscA interacts with EspA and enhances the protein stability of EspA. However, EscA is also able to interact with inner membrane-associated EscL, CesA2, and EscN, but not with cytoplasmic CesAB. In terms of gene organizations, escA locates in LEE3. Expression of EscA is faithfully regulated via Mpc, the first gene product of LEE3. Since Mpc is tightly regulated to low level, we suggest that EscA is highly synchronized and critical to the process of escorting EspA to its final destination.