Case series of ovarian neuroendocrine carcinoma: overview of clinicopathological features.

BACKGROUND: Ovarian neuroendocrine carcinoma (O-NEC) is a relatively uncommon neoplasm, and the current knowledge regarding its diagnosis and management is limited. In this series, our objective was to provide an overview of the clinicopathological characteristics of the disease by analyzing clinical case data to establish a theoretical foundation for the diagnosis and management of O-NEC. CASE PRESENTATION: We included three patients in the present case series, all of whom were diagnosed with primary O-NEC based on pathomorphological observation and immunohistochemistry. Patient 1 was a 62-year-old patient diagnosed with small cell carcinoma (SCC) of the pulmonary type. Post-surgery, the patient was diagnosed with stage II SCC of the ovary and underwent standardized chemotherapy; however, imaging examinations conducted at the 16-month follow-up revealed the existence of lymph node metastasis. Unfortunately, she passed away 21 months after the surgery. The other two patients were diagnosed with carcinoid tumors, one at age 39 and the other at age 71. Post-surgery, patient 2 was diagnosed with a carcinoid in the left ovary, whereas patient 3 was diagnosed with a carcinoid in her right ovary based on clinical evaluation. Neither of the cases received adjuvant therapy following surgery; however, they have both survived for 9 and 10 years, respectively, as of date. CONCLUSION: Primary O-NECs are rare and of diverse histological types, each of which has its own unique biological features and prognosis. SCC is a neoplasm characterized by high malignancy and a poor prognosis, whereas carcinoid tumors are of lesser malignancy and have a more favorable prognosis.

Efficient ilamycins production utilizing Enteromorpha prolifera by metabolically engineered Streptomyces atratus.

With the invasion of green tides and the increase of urban green areas worldwide, multimillion tons of Enteromorpha need to be reutilized. In this study, Enteromorpha prolifera powder is considered a promising biomass resource for the production of commercial chemical products production. Ilamycins, novel cyclic heptapeptides with significant anti-TB activities, are isolated from Streptomyces atratus SCSIO ZH16, a deep-sea-derived strain. Using EP powder as a nitrogen source, the production of ilamycins reached 709.97 mg/L through optimization of the nitrogen source using the engineered strain S. atratus SCSIO ZH16 ΔR. After mutant strain constructions and tests, strain S. atratus SCSIO ZH16 ΔR::bldD EP powder achieved a higher production titer of ilamycins. Furthermore, the production titer of ilamycins and ilamycin E reached 1561.77 mg/L and 745.44 mg/L, respectively, in a 5 L bioreactor. This study suggests that E. prolifera is a promising and eco-friendly nitrogen source for the production of ilamycins.

Risk factors of temperature increase after cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy.

Background: Cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) is the standard treatment for patients with peritoneal cancer (PC). Following CRS-HIPEC, patients may also face risks caused by whole body hyperthermia. This study analyzed the incidence of temperature increases following CRS-HIPEC and identified the attendant risk factors. Methods: A retrospective analysis was carried out among 458 patients who received CRS-HIPEC at the Fourth Hospital of Hebei Medical University between August 2018 and January 2021. The patients were divided into two groups according to post-HIPEC axillary temperature (≥38°C), with the demographics and the laboratory test results subsequently analyzed and compared, and the risk factors pertaining to temperature increases analyzed using univariate and multivariate logistic regression. Results: During CRS-HIPEC, 32.5% (149/458) of the patients with a temperature increase had an axillary temperature of not lower than 38°C, and 8.5% (39/458) of the patients with hyperpyrexia had an axillary temperature of not lower than 39°C. Female gender, gynecological malignancies, type of chemotherapy drug, increased postoperative neutrophil percentage, and a sharp drop in postoperative prealbumin were associated with the incidence of a temperature increase and axillary temperatures of >38°C. Among these factors, the type of chemotherapy drug was identified as an independent risk factor for a temperature increase during CRS-HIPEC. Conclusion: By determining the risk factors pertaining to temperature increases during CRS-HIPEC, medical staff can identify the attendant risks among the patients and thus take preventive measures in a timely manner to maintain the patient's body temperature at a stable level. This suggests that further clinical research should be conducted to build a risk-prediction model for temperature increases following CRS-HIPEC.

Smart deworming collar: A novel tool for reducing Echinococcus infection in dogs.

Echinococcosis is a serious zoonotic parasitic disease transmitted from canines to humans and livestock. Periodic deworming is recommended by the WHO/OIE as a highly effective measure against echinococcosis. However, manual deworming involves significant challenges, particularly in remote areas with scarce resources. The insufficient awareness delivering praziquantel (PZQ) baits for dogs leads to low compliance rate. The aim of this study was therefore to develop a novel smart collar for dogs to address these challenges. We developed a smart Internet of Things (IoT)-based deworming collar which can deliver PZQ baits for dogs automatically, regularly, quantitatively with predominant characteristics of being waterproof, anti-collision, cold-proof and long life battery. Its performance was tested in two remote locations on the Tibetan Plateau. A cross-sectional survey was conducted to evaluate the compliance of the dog owners. Further, a randomized controlled study was performed to evaluate the difference between smart-collar deworming and manual deworming. The collar's effectiveness was further assessed on the basis of Generalized Estimation Equations (GEE). The testing and evaluation was done for 10 smart deworming collars in factory laboratory, 18 collars attached for 18 dogs in Seni district, Tibet Autonomous Region, China, and 523 collars attached for 523 dogs in Hezuo city, Gansu province, China. The anti-collision, waterproof, and coldproof proportion of the smart collars were 100.0%, 99.5%, and 100.0%, respectively. When compared to manual deworming, the dogs' risk of infection with Echinococcus on smart-collar deworming is down to 0.182 times (95% CI: 0.049, 0.684) in Seni district and 0.355 (95%CI: 0.178, 0.706) in Hezuo city, the smart collar has a significant protective effect. The owners' overall compliance rate to attach the smart collars for their dogs was 89%. The smart deworming collar could effectively reduce the dogs' risk of infection with Echinococcus in dogs, significantly increase the deworming frequency and coverage and rapidly remove worm biomass in dogs. Thus, it may be a promising alternative to manual deworming, particularly in remote areas on the Tibetan Plateau.

A remote management system for control and surveillance of echinococcosis: design and implementation based on internet of things.

BACKGROUND: As a neglected cross-species parasitic disease transmitted between canines and livestock, echinococcosis remains a global public health concern with a heavy disease burden. In China, especially in the epidemic pastoral communities on the Qinghai-Tibet Plateau, the harsh climate, low socio-economic status, poor overall hygiene, and remote and insufficient access to all owned dogs exacerbate the difficulty in implementing the ambitious control programme for echinococcosis. We aimed to design and implement a remote management system (RMS) based on internet of things (IoT) for control and surveillance of echinococcosis by combining deworming devices to realise long-distance smart deworming control, smooth statistical analysis and result display. New methods and tools are urgently needed to increase the deworming coverage and frequency, promote real-time scientific surveillance, and prevent transmission of echinococcosis in remoted transmission areas. METHODS: From 2016 to 2019, we had cooperated and developed the smart collar and smart feeder with the Central Research Institute of Shanghai Electric Group Co., Ltd. (Shanghai, China) and Shenzhen Jizhi Future Technology Co., Ltd. (Shenzhen, China). From September 2019 to March 2020, We had proposed the RMS based on IoT as a novel tool to control smart deworming devices to deliver efficient praziquantel (PZQ) baits to dogs regularly and automatically and also as a smart digital management platform to monitor, analyse, and display the epidemic trends of echinococcosis dynamically, in real time in Hezuo City, Gannan Tibetan Autonomous Prefecture, Gansu Province, China. Starting from January 2018, The RMS has been maintained and upgraded by Shanghai Yier Information Technology Co., Ltd (Shanghai, China). The database was based on MySQL tools and the Chi-square test was used to probe the difference and changes of variables in different groups. RESULTS: The smart collars are fully capable of anti-collision, waterproof, and cold-proof performance, and the battery's energy is sufficient, the anti-collision rate, water-proof rate, cold-proof rate and voltage normal rate is 99.6% (521/523), 100.0% (523/523), 100.0% (523/523) and 100.0% (523/523), respectively. The RMS can accurately analyse the monitoring data and parameters including positive rates of canine faeces, and the prevalence of echinococcosis in the general population livestock, and children. The data of dogs deworming and surveillance for echinococcosis is able to be controlled using RMS and has expanded gradually in townships to the whole Hezuo region. The automatic delivering PZQ rate, collar positioning rate, deliver PZQ reminding rate, and fault report rate is 91.1% (1914/2102), 92.1% (13 580/14 745), 92.1% (1936/2102) and 84.7% (1287/1519), respectively. After using the RMS from 2019, the missing rate of monitoring data decreased from 32.1% (9/28) to 0 (0/16). A total of 48 administrators (3, 3, 8, 11, 23 at the provincial, municipal, county, township, village levels, respectively) participated in the questionnaire survey, with 93.8% of its overall satisfaction rate. CONCLUSIONS: The existing difficulties and challenges in the way of prevention and control for echinococcosis can partially be resolved using the innovative, IoT-based technologies and tools. The proposed RMS advance the upgrade of existing manual prevention and control models for echinococcosis, especially in the current ongoing COVID-19 pandemic, as social distance and community blockade continue.

Natural products for treating colorectal cancer: A mechanistic review.

Colorectal cancer (CRC) is one of the most common types of cancers in humans and is closely linked to the global cancer-related mortalities worldwide. Molecular pathological epidemiology studies can reveal the risk factors of CRC and contribute to biomarker research and precision medicine. The current clinical treatment for CRC mainly involves surgery and chemotherapy. However, because of the occurrence of side effects and the emergence of drug resistance, there is an urgent need to find new and more effective drugs for CRC treatment. An increasing number of studies have demonstrated that many natural products possess effective anti-CRC effects and may serve as alternative chemotherapy agents for CRC treatment. In this review, we summarize the natural products with anti-CRC effects from different sources based on the chemical structures such as alkaloids, polysaccharides, polyphenols, terpenoid, unsaturated fatty acids, and discuss the natural product-derived drugs used clinically for colorectal cancer treatment. Furthermore, natural products of marine origin are also discussed for their enormous potential to serve as the candidate drugs. Notably, we generalize the experiment-based molecular mechanisms and the regulatory networks whereby natural products exert anticancer effects on cell proliferation, metastasis, apoptosis, autophagy, and angiogenesis.

MLVA and MLST typing of Brucella from Qinghai, China.

BACKGROUND: The Qinghai-Tibet Plateau (QTP) of China is an extensive pastoral and semi-pastoral area, and because of poverty and bad hygiene conditions, Brucella is highly prevalent in this region. In order to adequately prevent this disease in the QTP region it is important to determine the identity of Brucella species that caused the infection. METHODS: A total of 65 Brucella isolates were obtained from human, livestock and wild animals in Qinghai, a Chinese province in east of the QTP. Two molecular typing methods, MLVA (multi-locus variable-number tandem-repeat analysis) and MLST (multi locus sequence typing) were used to identify the species and genotypes of these isolates. FINDINGS: Both MLVA and MLST typing methods classified the 65 isolates into three species, B. melitensis, B. abortus and B. suis, which included 60, 4 and 1 isolates respectively. The MLVA method uniquely detected 34 (Bm01 ~ Bm34), 3 (Ba01 ~ Ba03), and 1 (Bs01) MLVA-16 genotypes for B. melitensis, B. abortus and B. suis, respectively. However, none of these genotypes exactly matched any of the genotypes in the Brucella2012 MLVA database. The MLST method identified five known ST types: ST7 and ST8 (B. melitensis), ST2 and ST5 (B. abortus), and ST14 (B. suis). We also detected a strain with a mutant type (3-2-3-2-?-5-3-8-2) of ST8 (3-2-3-2-1-5-3-8-2). Extensive genotype-sharing events could be observed among isolates from different host species. CONCLUSIONS: There were at least three Brucella (B. melitensis, B. abortus and B. suis) species in Qinghai, of which B. melitensis was the predominant species in the area examined. The Brucella population in Qinghai was very different from other regions of the world, possibly owing to the unique geographical characteristics such as extremely high altitude in QTP. There were extensive genotype-sharing events between isolates obtained from humans and other animals. Yaks, sheep and blue sheep were important zoonotic reservoirs of brucellosis causing species found in humans.

[An Epidemiological Survey on Echinococcosis in Yushu Prefecture of Qinghai Province].

Objective: To investigate the prevalence of echinococcosis in Yushu Prefecture of Qinghai Province in 2012. Methods: Two to three towns were selected in each of Chengduo, Nangqian, Qu malai, Yushu, Zaduo and Zhiduo Counties from June to August in 2012. Ultrasound examination was conducted for residents aged over 1 year, and ELISA was performed to detect serum antibody against Echinococcus. Visceral dissection was performed to detect hydatid infection in rodents and livestock. ELISA was used to detect Echinococcus antigen in collected dog feces. Results: A total of 7 025 residents received ultrasound examination, of whom 319 showed hydatid cysts with a morbidity rate of 4.54%. ELISA showed a serum antibody positive rate of 16.38% （457/2 790）. The mobidity of hydatid disease was highest in Chengduo County （7.41%, 181/2 444）, and the rate of serum antibody was highest in Yushu County （23.18%, 127/548）. The morbidity and serum antibody in males were 3.91% （118/3 018） and 13.93% （172/1 235） respectively, and those in females were 5.02% （201/4 007） and 18.33% （285/1 555）. In terms of age distribution, the morbidity was relatively higher in residents of 60- （8.39%, 38/453） and 40- years （6.61%, 67/1 014）; and the rate of serum antibody was highest in residents over 70 years （33.93%, 19/56）. In terms of occupation, the morbidity was relatively higher in herdsmen （5.28%, 252/4 777）, Herdsmen-peasants （6.52%, 24/368）, and religious workers（3.37%, 11/326）, while the rate of serum antibody was relatively higher in children（24%, 6/25）, religious workers （18.79%, 31/165） and herdsmen（18.34%, 328/1 788）. In terms of education level, the morbidity and the rate of serum antibody were both highest in the uneducated（5.04%, 41/4 779; 18.34%, 359/1 958, respectively）. In terms of residential pattern, the morbidity and the rate of serum antibody were both highest in those who were settled in winter and nomadic in summer （8.25%, 227/2 753; 19.48%, 158/811, respectively）. There were significant differences in the morbidity and the rate of serum antibody in aspects of residential region, sex, age, occupation, education level and residential pattern (P<0.05 or P<0.01). In 872 rodents detected, the Echinococcus hydatid rate was 0.46% （4/872）, while in 809 cattle and sheep detected, the Echinococcus hydatid rate was 10.14% （82/809）. The fecal antigen positive rate in 838 samples of dog feces was 10.74%（90/838）. Conclusion: It shows a high morbidity of hydatid diesease and serum antibody positive rate in residents, a high Echinococcus hydatid rate in cattle and sheep, and a high fecal antigen positive rate in dogs in Yushu Prefecture.

[Survey on Echinococcosis in Maqing County of Qinghai Province].

OBJECTIVE: To understand the status of echinococcosis in Maqing County of Qinghai Province in order to facilitate echinococcosis control in this region. METHODS: Ultrasonic scanning and indirect hemagglutination assay were used to detect echinococcosis infection in residents >1 year old, according to the People's Republic of China Health Industry Standard--Diagnostic Criteria for Hydatid Disease (WS257-2006). Meanwhile, ELISA was used o detect the Echinococcus antigen in dog's feces collected in Youyun, Dangluo and Xiadawu townships. RESULTS: Ultrasonic scanning showed that the prevalence of hydatid disease in the residents was 7.4% (116/1 561), cystic hydatid disease 5.3% (82/1 561), alveolar hydatid disease 2.2% (34/1 561). The serum positive rate in human population was 23.8%(307/1 288). Of the 82 cases of cystic hydatid disease, 23 cases (28.1%) had the hydatid cyst with a diameter of >10 cm. The prevalence in males and females in the county was 5.3% (40/753) and 9.4% (76/808), respectively (P<0.05). Among populations with different occupations, the highest prevalence of hydatid disease fell into houseworkers (11/61, 18.0%), monks (5/41, 12.2%) and herdsmen (84/758, 11.1%). Among the age groups, the groups of >60 years (24/132, 18.2%) and 30-40 years (31/302, 10.3%) had higher prevalence of hydatid disease. The three townships with the higher prevalence were Youyun (29/247, 11.7%), Changmahe (6/63, 9.5%) and Dangluo (54/645, 8.4%). Of the 199 samples of dog's feces, 54 were positive for Echinococcus antigens (27.1%), with a positive rate of 40.4% (23/57) in Youyun towship, being significantly higher than in the other two (P<0.05). CONCLUSION: Maqin county is a co-endemic area of cystic echinococcosis and alveolar echinococcosis. The prevalence is higher in females and those over 60 years-old.

Laparoscopic vaginoplasty using a single peritoneal flap: 10 years of experience in the creation of a neovagina in patients with Mayer-Rokitansky-Küster-Hauser syndrome.

OBJECTIVE: To assess anatomical and functional outcomes of a novel laparoscopic vaginoplasty technique using a single peritoneal flap (SPF) in patients with Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome. DESIGN: Prospective follow-up study. SETTING: University-based tertiary-care hospital. PATIENT(S): Patients with MRKH syndrome (n = 83) and randomly selected frequency-matched age-comparable healthy women serving as controls (n = 85). INTERVENTION(S): From March 2004 to March 2014, a total of 83 patients with MRKH syndrome underwent laparoscopic vaginoplasty using an SPF. MAIN OUTCOME MEASURE(S): Intraoperative parameters, postoperative parameters, and anatomical outcomes were recorded. The functional results of patients who became sexually active were assessed using the Female Sexual Function Index (FSFI) questionnaire and were compared with those of the controls. RESULT(S): Laparoscopic vaginoplasty using an SPF was successfully performed in all 83 patients, with no intraoperative complications. The mean operative time and intraoperative blood loss were, respectively, 71.2 ± 18.9 minutes and 88.5 ± 57.2 ml. The mean length and width of the neovagina at the 6-month follow-up examination were, respectively, 8.2 ± 0.8 cm and 3.0 ± 0.6 cm. Anatomical success was achieved in all patients. At 12 months after surgery, functional success, as assessed by the FSFI questionnaire, was achieved in 95.3% of patients. The FSFI scores did not differ significantly between patients with MRKH and healthy women in a control group. CONCLUSION(S): Laparoscopic vaginoplasty using an SPF may be a feasible and effective approach that has satisfactory anatomical and functional outcomes for patients with MRKH syndrome.

Molecular identification of Taenia mustelae cysts in subterranean rodent plateau zokors (Eospalax baileyi).

Cestode larvae spend one phase of their two-phase life cycle in the viscera of rodents, but cases of cestodes infecting subterranean rodents have only been rarely observed. To experimentally gain some insight into this phenomenon, we captured approximately 300 plateau zokors (Eospalax baileyi), a typical subterranean rodent inhabiting the Qinghai-Tibet Plateau, and examined their livers for the presence of cysts. Totally, we collected five cysts, and using a mitochondrial gene (cox1) and two nuclear genes (pepck and pold) as genetic markers, we were able to analyze the taxonomy of the cysts. Both the maximum likelihood and Bayesian methods showed that the cysts share a monophyly with Taenia mustelae, while Kimura 2-parameter distances and number of different sites between our sequences and T. mustelae were far less than those found between the examined sequences and other Taeniidae species. These results, alongside supporting paraffin section histology, imply that the cysts found in plateau zokors can be regarded as larvae of T. mustelae, illustrating that zokors are a newly discovered intermediate host record of this parasite.

[Carbon disulfide exposure level of workers in a chemical fiber industry].

OBJECTIVE: To investigate the exposure levels of carbon disulfide (CS(2)) for a chemical fiber industry. METHODS: The concentration of CS(2) was monitored in representative workshops and types of work, and the datas of that over the years were collected. RESULTS: The short-term exposure concentration of CS(2) about 80% of the type of work was less than or equal to 10 mg/m(3), which of more than 90% was less than or equal to 20 mg/m(3). The time weighted average concentration of CS(2) about 70% of the type of work was less than or equal to 5 mg/m(3), which of more than 90% was less than or equal to 10 mg/m(3). The short-term exposure concentration of CS(2) which was more than 15 mg/m(3) or the time weighted average concentration of CS(2) which was more than 30 mg/m(3) was only for little type of work. CONCLUSION: The concentration of CS(2) for the most type of work was lower, but there were still a number of types of work exposuring the higher concentration, which exceed the national occupational exposure limits.

Genetic loci controlling lethal cell death in tomato caused by viral satellite RNA infection.

Cucumber mosaic virus (CMV) associated with D satellite RNA (satRNA) causes lethal systemic necrosis (LSN) in tomato (Solanum lycopersicum), which involves programmed cell death. No resistance to this disease has been found in tomato. We obtained a line of wild tomato, S. habrochaitis, with a homogeneous non-lethal response (NLR) to the infection. This line of S. habrochaitis was crossed with tomato to generate F1 plants that survived the infection with NLR, indicating that NLR is a dominant trait. The NLR trait was successfully passed on to the next generation. The phenotype and genotype segregation was analyzed in the first backcross population. The analyses indicate that the NLR trait is determined by quantitative trait loci (QTL). Major QTL associated with the NLR trait were mapped to chromosomes 5 and 12. Results from Northern blot and in situ hybridization analyses revealed that the F1 and S. habrochaitis plants accumulated minus-strand satRNA more slowly than tomato, and fewer vascular cells were infected. In addition, D satRNA-induced LSN in tomato is correlated with higher accumulation of the minus-strand satRNA compared with the accumulation of the minus strand of a non-necrogenic mutant D satRNA.

(E)-N'-(4-Meth-oxy-benzyl-idene)-3-nitro-benzohydrazide.

In the title compound, C(15)H(13)N(3)O(4), the two substituted benzene rings form a dihedral angle of 5.0 (3)°. In the crystal, inter-molecular N-H⋯O hydrogen bonds link mol-ecules into chains along the b axis.

(E)-N'-(2-Meth-oxy-benzyl-idene)-3-nitro-benzohydrazide.

In the title compound, C(15)H(13)N(3)O(4), the two substituted benzene rings form a dihedral angle of 10.9 (3)°. In the crystal, inter-molecular C-H⋯O and N-H⋯O hydrogen bonds link mol-ecules into chains running parallel to [101].

{4-Bromo-2-[2-(isopropyl-amino)ethyl-imino-meth-yl]phenolato}thio-cyanato-copper(II).

In the title mononuclear Schiff base copper(II) complex, [Cu(C(12)H(16)BrN(2)O)(NCS)], the Cu(II) ion is coordinated by two N atoms and one O atom from a Schiff base ligand, and by one N atom from a thio-cyanate anion, giving a square-planar geometry. There are long-range inter-actions between the Cu atom and S [3.151 (5) Å] and Br [3.929 (5) Å] atoms above and below the square plane.

{4,4'-Dibromo-2,2'-[propane-1,3-diyl-bis(nitrilo-methyl-idyne)]diphenolato}zinc(II).

The title mononuclear zinc(II) complex, [Zn(C(17)H(14)Br(2)N(2)O(2))], possesses a crystallographically imposed C(2) axis. The Zn atom is four-coordinated by two O and two N atoms from two Schiff base ligands, forming a severely distorted square-planar geometry. The central C atom of the propyl group is disordered over two positions about the twofold axis.

{4-Bromo-2-[2-(methyl-amino-)ethyl-iminometh-yl]phenolato}thio-cyanato-copper(II).

In the title mononuclear copper(II) complex, [Cu(C(10)H(12)BrN(2)O)(NCS)], the Cu(II) ion is coordinated by two N atoms and one O atom from a Schiff base ligand, and by one N atom from a thio-cyanate anion, giving a square-planar geometry. In the crystal structure, symmetry-related mol-ecules are linked by an N-H⋯S hydrogen bond.

[An epidemiological survey on echinococcosis in Zhiduo County of Qinghai Province].

The survey was carried out in July, 2006 in Zhiduo County. The IHA and ELISA positive rate in human population was 4.5% (42/933) and 8.2% (76/931) respectively. Ultrasonography revealed a morbidity of 3.4% (33/979) with 3.2% Echinococcus granulosus and 0.2% of E. multilocularis respectively. Animal dissection showed an infection rate of 15.1% (14/93) in pikas with one infected by E. shiquicus proved by molecular biology. Coproantigen rate by ELISA was 62% (12/193) in dogs and 35.7% (5/14) in wolves. The results indicated that Zhiduo County is a mixed endemic area for echinococcosis.

Emergence of RmtB methylase-producing Escherichia coli and Enterobacter cloacae isolates from pigs in China.

OBJECTIVES: To investigate the occurrence of 16S rRNA methylases conferring high-level resistance to aminoglycosides in Enterobacteriaceae isolated from two pig farms in China. METHODS: Enterobacteriaceae isolated from 151 pig rectal swab samples and 9 environmental samples were screened for the presence of the rmtA, rmtB, armA and rmtC genes by PCR and sequencing. Conjugation experiments were carried out to study the transferability of the 16S rRNA methylase genes. All isolates and their transconjugants were tested for susceptibility to antimicrobial agents. The clonal relatedness of RmtB-producing Escherichia coli was assessed by PFGE with XbaI. RESULTS: Of 152 Enterobacteriaceae isolates recovered from pigs, 49 (32%) were positive for the rmtB gene, including 48 E. coli and a single isolate of Enterobacter cloacae. Of the nine Enterobacteriaceae isolates from environmental samples, no 16S rRNA methylase gene was identified. The 49 rmtB-positive isolates showed resistance to ampicillin, tetracycline and trimethoprim and also carried a bla(TEM) gene. Transfer of the rmtB and bla(TEM) genes by conjugation experiments of all 49 isolates was successful, suggesting that the rmtB-containing plasmids in the E. coli and E. cloacae isolates were self-transmissible. Conjugative transfer frequencies varied from 2.2 x 10(-10) to 1.3 x 10(-6) transconjugants per recipient. The transfer of non-aminoglycoside antimicrobial resistance traits was also observed in most cases. Forty-four rmtB-positive E. coli showed 30 different PFGE types. CONCLUSIONS: The rmtB gene was detected on conjugative plasmids of porcine E. coli and E. cloacae isolates. Both horizontal gene transfer and clonal spread were responsible for the dissemination of the rmtB gene. The emergence of 16S rRNA methylases in Enterobacteriaceae isolates is described for the first time in China. This is also the first report of rmtB-positive Enterobacteriaceae among healthy food-producing animals.