Natural products are important sources for the discovery of anti-tumor drugs. Evodiamine is the main alkaloid component of the traditional Chinese herb Wu-Chu-Yu, and it has weak antitumor activity. In recent years, a number of highly active antitumor candidates have been discovered with a significant progress. This article reviews the research progress of evodiamine-based antitumor drug design strategies, in order to provide reference for the development of new drugs with natural products as leads.

Objective To investigate the clinical characteristics and prognosis of pneumococcal meningitis(PM),and drug sensitivity of Streptococcus pneumoniae(SP)isolates in Chinese children.Methods A retrospective analysis was conducted on clinical information,laboratory data,and microbiological data of 160 hospitalized children under 15 years old with PM from January 2019 to December 2020 in 33 tertiary hospitals across the country.Results Among the 160 children with PM,there were 103 males and 57 females.The age ranged from 15 days to 15 years,with 109 cases(68.1% )aged 3 months to under 3 years.SP strains were isolated from 95 cases(59.4% )in cerebrospinal fluid cultures and from 57 cases(35.6% )in blood cultures.The positive rates of SP detection by cerebrospinal fluid metagenomic next-generation sequencing and cerebrospinal fluid SP antigen testing were 40% (35/87)and 27% (21/78),respectively.Fifty-five cases(34.4% )had one or more risk factors for purulent meningitis,113 cases(70.6% )had one or more extra-cranial infectious foci,and 18 cases(11.3% )had underlying diseases.The most common clinical symptoms were fever(147 cases,91.9% ),followed by lethargy(98 cases,61.3% )and vomiting(61 cases,38.1% ).Sixty-nine cases(43.1% )experienced intracranial complications during hospitalization,with subdural effusion and/or empyema being the most common complication[43 cases(26.9% )],followed by hydrocephalus in 24 cases(15.0% ),brain abscess in 23 cases(14.4% ),and cerebral hemorrhage in 8 cases(5.0% ).Subdural effusion and/or empyema and hydrocephalus mainly occurred in children under 1 year old,with rates of 91% (39/43)and 83% (20/24),respectively.SP strains exhibited complete sensitivity to vancomycin(100% ,75/75),linezolid(100% ,56/56),and meropenem(100% ,6/6).High sensitivity rates were also observed for levofloxacin(81% ,22/27),moxifloxacin(82% ,14/17),rifampicin(96% ,25/26),and chloramphenicol(91% ,21/23).However,low sensitivity rates were found for penicillin(16% ,11/68)and clindamycin(6% ,1/17),and SP strains were completely resistant to erythromycin(100% ,31/31).The rates of discharge with cure and improvement were 22.5% (36/160)and 66.2% (106/160),respectively,while 18 cases(11.3% )had adverse outcomes.Conclusions Pediatric PM is more common in children aged 3 months to under 3 years.Intracranial complications are more frequently observed in children under 1 year old.Fever is the most common clinical manifestation of PM,and subdural effusion/emphysema and hydrocephalus are the most frequent complications.Non-culture detection methods for cerebrospinal fluid can improve pathogen detection rates.Adverse outcomes can be noted in more than 10% of PM cases.SP strains are high sensitivity to vancomycin,linezolid,meropenem,levofloxacin,moxifloxacin,rifampicin,and chloramphenicol.[Chinese Journal of Contemporary Pediatrics,2024,26(2):131-138]

Objective:The main purpose of this study is to analyse the current situation and inequity status of children's medical security in China from the vision of children first.Methods:Using data from the China Family Panel Studies 2020 and based on the framework of universal health coverage cube,multivariate regression is used to analyse the differences in medical security between children and adults and among groups of children.Results:The participation rate of children in China is 80.96%,out-of-pocket ratios are 64.71%and 90.09%for inpatient and outpatient groups respectively.In terms of participation rate,insured children are less than that of adults(OR=0.434,P＜0.01);within children's groups,attending school(OR=2.075,P＜0.01)significantly increases children's participation rate,while left-behind by parent(s)(OR=0.791,P＜0.05)significantly decrease children's participation rate.With respect to service and cost coverage,children have higher out-of-pocket ratios compared to adults(β=0.066,P＜0.01);within children's groups,children eged 6 years and older have lower out-of-pocket medical expenses(β＜-0.316,P＜0.01),children with higher family income(β＜-0.022,P＜0.05),participated(β=-0.033,P＜0.01),and hospitalized(β=-0.270,P＜0.01)have lower out-of-pocket ratios.Conclusion:Double in equality exists in children's medical security in China.The level of children's health security in China is significantly lower than that of adults;within children's groups,children aged 0～5 years,not in school,left-behind by parent(s),and from lower-income families are more vulnerable.It is proposed to focus on increasing the participation rate of children through measures such as optimizing the contribution for children and launching family joint insurance.Policy design should also consider the needs of children and raise the level of children's benefits.Meanwhile,the focus should be on helping vulnerable groups in children,so as to ultimately achieve"children first"in health security.

Objective: This cross-sectional investigation aimed to determine the incidence, clinical characteristics, prognosis, and related risk factors of olfactory and gustatory dysfunctions related to infection with the SARS-CoV-2 Omicron strain in mainland China. Methods: Data of patients with SARS-CoV-2 from December 28, 2022, to February 21, 2023, were collected through online and offline questionnaires from 45 tertiary hospitals and one center for disease control and prevention in mainland China. The questionnaire included demographic information, previous health history, smoking and alcohol drinking, SARS-CoV-2 vaccination, olfactory and gustatory function before and after infection, other symptoms after infection, as well as the duration and improvement of olfactory and gustatory dysfunction. The self-reported olfactory and gustatory functions of patients were evaluated using the Olfactory VAS scale and Gustatory VAS scale. Results: A total of 35 566 valid questionnaires were obtained, revealing a high incidence of olfactory and taste dysfunctions related to infection with the SARS-CoV-2 Omicron strain (67.75%). Females(χ2=367.013, P<0.001) and young people(χ2=120.210, P<0.001) were more likely to develop these dysfunctions. Gender(OR=1.564, 95%CI: 1.487-1.645), SARS-CoV-2 vaccination status (OR=1.334, 95%CI: 1.164-1.530), oral health status (OR=0.881, 95%CI: 0.839-0.926), smoking history (OR=1.152, 95%CI=1.080-1.229), and drinking history (OR=0.854, 95%CI: 0.785-0.928) were correlated with the occurrence of olfactory and taste dysfunctions related to SARS-CoV-2(above P<0.001). 44.62% (4 391/9 840) of the patients who had not recovered their sense of smell and taste also suffered from nasal congestion, runny nose, and 32.62% (3 210/9 840) suffered from dry mouth and sore throat. The improvement of olfactory and taste functions was correlated with the persistence of accompanying symptoms(χ2=10.873, P=0.001). The average score of olfactory and taste VAS scale was 8.41 and 8.51 respectively before SARS-CoV-2 infection, but decreased to3.69 and 4.29 respectively after SARS-CoV-2 infection, and recovered to 5.83and 6.55 respectively at the time of the survey. The median duration of olfactory and gustatory dysfunctions was 15 days and 12 days, respectively, with 0.5% (121/24 096) of patients experiencing these dysfunctions for more than 28 days. The overall self-reported improvement rate of smell and taste dysfunctions was 59.16% (14 256/24 096). Gender(OR=0.893, 95%CI: 0.839-0.951), SARS-CoV-2 vaccination status (OR=1.334, 95%CI: 1.164-1.530), history of head and facial trauma(OR=1.180, 95%CI: 1.036-1.344, P=0.013), nose (OR=1.104, 95%CI: 1.042-1.171, P=0.001) and oral (OR=1.162, 95%CI: 1.096-1.233) health status, smoking history(OR=0.765, 95%CI: 0.709-0.825), and the persistence of accompanying symptoms (OR=0.359, 95%CI: 0.332-0.388) were correlated with the recovery of olfactory and taste dysfunctions related to SARS-CoV-2 (above P<0.001 except for the indicated values). Conclusion: The incidence of olfactory and taste dysfunctions related to infection with the SARS-CoV-2 Omicron strain is high in mainland China, with females and young people more likely to develop these dysfunctions. Active and effective intervention measures may be required for cases that persist for a long time. The recovery of olfactory and taste functions is influenced by several factors, including gender, SARS-CoV-2 vaccination status, history of head and facial trauma, nasal and oral health status, smoking history, and persistence of accompanying symptoms.
Female ; Humans ; Adolescent ; SARS-CoV-2 ; Smell ; COVID-19/complications* ; Cross-Sectional Studies ; COVID-19 Vaccines ; Incidence ; Olfaction Disorders/etiology* ; Taste Disorders/etiology* ; Prognosis

Objective:To assess the clinical effectiveness and safety of Omalizumab for treating pediatric allergic asthma in real world in China.Methods:The clinical data of children aged 6 to 11 years with allergic asthma who received Omalizumab treatment in 17 hospitals in China between July 6, 2018 and September 30, 2020 were retrospectively analyzed.Such information as the demographic characteristics, allergic history, family history, total immunoglobulin E (IgE) levels, specific IgE levels, skin prick test, exhaled nitric oxide (FeNO) levels, eosinophil (EOS) counts, and comorbidities at baseline were collected.Descriptive analysis of the Omalizumab treatment mode was made, and the difference in the first dose, injection frequency and course of treatment between the Omalizumab treatment mode and the mode recommended in the instruction was investigated.Global Evaluation of Treatment Effectiveness (GETE) analysis was made after Omalizumab treatment.The moderate-to-severe asthma exacerbation rate, inhaled corticosteroid (ICS) dose, lung functions were compared before and after Omalizumab treatment.Changes in the Childhood Asthma Control Test (C-ACT) and Pediatric Asthma Quality of Life Questionnaire (PAQLQ) results from baseline to 4, 8, 12, 16, 24, and 52 weeks after Omalizumab treatment were studied.The commodity improvement was assessed.The adverse event (AE) and serious adverse event (SAE) were analyzed for the evaluation of Omalizumab treatment safety.The difference in the annual rate of moderate-to-severe asthma exacerbation and ICS reduction was investigated by using t test.The significance level was set to 0.05.Other parameters were all subject to descriptive analysis.A total of 200 allergic asthma patients were enrolled, including 75.5% ( n=151) males and 24.5% ( n=49) females.The patients aged (8.20±1.81) years. Results:The median total IgE level of the 200 patients was 513.5 (24.4-11 600.0) IU/mL.Their median treatment time with Omalizumab was 112 (1-666) days.Their first dose of Omalizumab was 300 (150-600) mg.Of the 200 cases, 114 cases (57.0%) followed the first Omalizumab dosage recommended in the instruction.After 4-6 months of Omalizumab treatment, 88.5% of the patients enrolled ( n=117) responded to Omalizumab.After 4 weeks of treatment with Omalizumab, asthma was well-controlled, with an increased C-ACT score [from (22.70±3.70) points to (18.90±3.74) points at baseline]. Four-six months after Omalizumab administration, the annual rate of moderate-to-severe asthma exacerbation had a reduction of (2.00±5.68) per patient year( t=4.702 5, P<0.001), the median ICS daily dose was lowered [0 (0-240) μg vs. 160 (50-4 000) μg at baseline] ( P<0.001), the PAQLQ score was improved [(154.90±8.57) points vs. (122.80±27.15) points at baseline], and the forced expiratory volume in one second % predicted (FEV 1%pred) was increased [(92.80±10.50)% vs. (89.70±18.17)% at baseline]. In patients with available evaluations for comorbidities, including allergic rhinitis, atopic dermatitis or eczema, urticaria, allergic conjunctivitis and sinusitis, 92.8%-100.0% showed improved symptoms.A total of 124 AE were reported in 58 (29.0%) of the 200 patients, and the annual incidence was 0(0-15.1) per patient year.In 53 patients who suffered AE, 44 patients (83.0%) and 9 patients (17.0%) reported mild and moderate AE, respectively.No severe AE were observed in patients.The annual incidence of SAE was 0(0-1.9) per patient year.Most common drug-related AE were abdominal pain (2 patients, 1.0%) and fever (2 patients, 1.0%). No patient withdrew Omalizumab due to AE. Conclusions:Omalizumab shows good effectiveness and safety for the treatment of asthma in children.It can reduce the moderate-to-severe asthma exacerbation rate, reduce the ICS dose, improve asthma control levels, and improve lung functions and quality of life of patients.

Objective: To explore the epidemiological characteristic of a COVID-19 outbreak caused by 2019-nCoV Omicron variant BF.7 and other provinces imported in Shenzhen and analyze transmission chains and characteristics. Methods: Field epidemiological survey was conducted to identify the transmission chain, analyze the generation relationship among the cases. The 2019-nCoV nucleic acid positive samples were used for gene sequencing. Results: From 8 to 23 October, 2022, a total of 196 cases of COVID-19 were reported in Shenzhen, all the cases had epidemiological links. In the cases, 100 were men and 96 were women, with a median of age, M (Q₁, Q₃) was 33(25, 46) years. The outbreak was caused by traverlers initial cases infected with 2019-nCoV who returned to Shenzhen after traveling outside of Guangdong Province.There were four transmission chains, including the transmission in place of residence and neighbourhood, affecting 8 persons, transmission in social activity in the evening on 7 October, affecting 65 persons, transmission in work place on 8 October, affecting 48 persons, and transmission in a building near the work place, affecting 74 persons. The median of the incubation period of the infection, M (Q₁, Q₃) was 1.44 (1.11, 2.17) days. The incubation period of indoor exposure less than that of the outdoor exposure, M (Q₁, Q₃) was 1.38 (1.06, 1.84) and 1.95 (1.22, 2.99) days, respcetively (Wald χ²=10.27, P=0.001). With the increase of case generation, the number and probability of gene mutation increased. In the same transmission chain, the proportion of having 1-3 mutation sites was high in the cases in the first generation. Conclusions: The transmission chains were clear in this epidemic. The incubation period of Omicron variant BF.7 infection was shorter, the transmission speed was faster, and the gene mutation rate was higher. It is necessary to conduct prompt response and strict disease control when epidemic occurs.
Male ; Humans ; Female ; SARS-CoV-2 ; COVID-19/epidemiology* ; Disease Outbreaks ; Epidemics ; China/epidemiology*

Objective: To analyze the prevalence and the risk factors of fungal sepsis in 25 neonatal intensive care units (NICU) among preterm infants in China, and to provide a basis for preventive strategies of fungal sepsis. Methods: This was a second-analysis of the data from the "reduction of infection in neonatal intensive care units using the evidence-based practice for improving quality" study. The current status of fungal sepsis of the 24 731 preterm infants with the gestational age of <34⁺⁰ weeks, who were admitted to 25 participating NICU within 7 days of birth between May 2015 and April 2018 were retrospectively analyzed. These preterm infants were divided into the fungal sepsis group and the without fungal sepsis group according to whether they developed fungal sepsis to analyze the incidences and the microbiology of fungal sepsis. Chi-square test was used to compare the incidences of fungal sepsis in preterm infants with different gestational ages and birth weights and in different NICU. Multivariate Logistic regression analysis was used to study the outcomes of preterm infants with fungal sepsis, which were further compared with those of preterm infants without fungal sepsis. The 144 preterm infants in the fungal sepsis group were matched with 288 preterm infants in the non-fungal sepsis group by propensity score-matched method. Univariate and multivariate Logistic regression analysis were used to analyze the risk factors of fungal sepsis. Results: In all, 166 (0.7%) of the 24 731 preterm infants developed fungal sepsis, with the gestational age of (29.7±2.0) weeks and the birth weight of (1 300±293) g. The incidence of fungal sepsis increased with decreasing gestational age and birth weight (both P<0.001). The preterm infants with gestational age of <32 weeks accounted for 87.3% (145/166). The incidence of fungal sepsis was 1.0% (117/11 438) in very preterm infants and 2.0% (28/1 401) in extremely preterm infants, and was 1.3% (103/8 060) in very low birth weight infants and 1.7% (21/1 211) in extremely low birth weight infants, respectively. There was no fungal sepsis in 3 NICU, and the incidences in the other 22 NICU ranged from 0.7% (10/1 397) to 2.9% (21/724), with significant statistical difference (P<0.001). The pathogens were mainly Candida (150/166, 90.4%), including 59 cases of Candida albicans and 91 cases of non-Candida albicans, of which Candida parapsilosis was the most common (41 cases). Fungal sepsis was independently associated with increased risk of moderate to severe bronchopulmonary dysplasia (BPD) (adjusted OR 1.52, 95%CI 1.04-2.22, P=0.030) and severe retinopathy of prematurity (ROP) (adjusted OR 2.55, 95%CI 1.12-5.80, P=0.025). Previous broad spectrum antibiotics exposure (adjusted OR=2.50, 95%CI 1.50-4.17, P<0.001), prolonged use of central line (adjusted OR=1.05, 95%CI 1.03-1.08, P<0.001) and previous total parenteral nutrition (TPN) duration (adjusted OR=1.04, 95%CI 1.02-1.06, P<0.001) were all independently associated with increasing risk of fungal sepsis. Conclusions: Candida albicans and Candida parapsilosis are the main pathogens of fungal sepsis among preterm infants in Chinese NICU. Preterm infants with fungal sepsis are at increased risk of moderate to severe BPD and severe ROP. Previous broad spectrum antibiotics exposure, prolonged use of central line and prolonged duration of TPN will increase the risk of fungal sepsis. Ongoing initiatives are needed to reduce fungal sepsis based on these risk factors.
Infant ; Infant, Newborn ; Humans ; Birth Weight ; Intensive Care Units, Neonatal ; Retrospective Studies ; Tertiary Care Centers ; Infant, Extremely Low Birth Weight ; Gestational Age ; Infant, Extremely Premature ; Sepsis/epidemiology* ; Retinopathy of Prematurity/epidemiology* ; Bronchopulmonary Dysplasia/epidemiology*

Professor Mao Xiejun wrote a report about dental education of China in 1935. From 1948 to 1950, he published three articles containing the educational idea of "developing dentistry into stomatology". When he served as the director of the Faculty of Dentistry of Peking University Medical School in July 1950, he proposed to rename the Faculty of Dentistry into the Faculty of Stomatology,which were approved by the Ministry of Health and the Ministry of Education of the People's Republic of China in one month. The Chinese Medical Association established the Society of Stomatology the next year. Later, dentistry was successively changed into stomatology, and medical content was integrated into dental education, which was of great significance and far-reaching influence. During the developments of the thought of stomatological education in China, Professor Mao Xiejun evidently played a pivotal role. In this paper, the formation process of the thoughts of stomatological education related to professor Mao Xiejun's contribution is elucidated through studying the archives, personal letters, and historical documents, so as to enrich the researches on the history of stomatology in China and to facilitate better understanding and promoting the development of stomatology.
Humans ; Oral Medicine/education* ; Education, Dental ; China ; Universities

OBJECTIVE: To assess the efficacy and safety of Bushen Huoxue Formula (BSHXF) for the treatment of discogenic low-back pain (DLBP). METHODS: This was a parallel, double-blind, randomized, clinical trial performed between May 2019 and June 2020. Seventy patients were assigned by computerized random number table to the treatment group (lumbar traction and BSHXF, 35 cases) or the control group (lumbar traction and placebo, 35 cases). The patients received intervention for 3 weeks. Assessment was conducted before treatment and at week 1, 2, 3 during treatment. Primary outcome was the self-reported score of Oswestry Disability Index (ODI). Secondary outcomes included Visual Analog Scale (VAS), clinical efficacy rate by minimal clinically important difference (MCID) as well as lumbar tenderness, muscle tone and lumbar spine mobility. Adverse reactions were recorded. Follow-up was performed at 1 and 3 months after the end of treatment. RESULTS: In the treatment group, ODI score was significantly decreased compared with baseline (P<0.05) and the control group at 2- and 3- week treatment. Similarly, VAS score decreased compared with the baseline (P<0.05) and was lower than that in the control group at 2- and 3- week treatment (P<0.05). The clinical efficacy rate of the treatment group was higher than that of the control group after treatment [32.35% (11/34) vs. 3.13% (1/32), P<0.05). Moreover, the tenderness, and muscle tone, as well as the back extension and left flexion in lumbar spine mobility in the treatment group at 3-week treatment were significantly improved compared with the control group (P<0.05). Follow-up showed that at 1-month after treatment, the treatment group had better outcomes than the control group with regard to a total score of ODI and VAS scores, as well as clinical efficacy rate (all P<0.05). Moreover, VAS score was still significantly lower than the control group at 3-month follow-up (P<0.05). No adverse reactions were reported during the study. CONCLUSION BSXHF combined with lumbar traction can significantly improve the clinical symptoms including pain intensity, functionality, muscle tone, and lumbar spine mobility in DLBP patients. (Registration No. ChiCTR1900027777).
Humans ; Intervertebral Disc Degeneration/therapy* ; Low Back Pain/drug therapy* ; Lumbar Vertebrae ; Pain Measurement ; Treatment Outcome

Objective: To analyze the clinical epidemiological characteristics including composition of pathogens , clinical characteristics, and disease prognosis acute bacterial meningitis (ABM) in Chinese children. Methods: A retrospective analysis was performed on the clinical and laboratory data of 1 610 children <15 years of age with ABM in 33 tertiary hospitals in China from January 2019 to December 2020. Patients were divided into different groups according to age,<28 days group, 28 days to <3 months group, 3 months to <1 year group, 1-<5 years of age group, 5-<15 years of age group; etiology confirmed group and clinically diagnosed group according to etiology diagnosis. Non-numeric variables were analyzed with the Chi-square test or Fisher's exact test, while non-normal distrituction numeric variables were compared with nonparametric test. Results: Among 1 610 children with ABM, 955 were male and 650 were female (5 cases were not provided with gender information), and the age of onset was 1.5 (0.5, 5.5) months. There were 588 cases age from <28 days, 462 cases age from 28 days to <3 months, 302 cases age from 3 months to <1 year of age group, 156 cases in the 1-<5 years of age and 101 cases in the 5-<15 years of age. The detection rates were 38.8% (95/245) and 31.5% (70/222) of Escherichia coli and 27.8% (68/245) and 35.1% (78/222) of Streptococcus agalactiae in infants younger than 28 days of age and 28 days to 3 months of age; the detection rates of Streptococcus pneumonia, Escherichia coli, and Streptococcus agalactiae were 34.3% (61/178), 14.0% (25/178) and 13.5% (24/178) in the 3 months of age to <1 year of age group; the dominant pathogens were Streptococcus pneumoniae and the detection rate were 67.9% (74/109) and 44.4% (16/36) in the 1-<5 years of age and 5-<15 years of age . There were 9.7% (19/195) strains of Escherichia coli producing ultra-broad-spectrum β-lactamases. The positive rates of cerebrospinal fluid (CSF) culture and blood culture were 32.2% (515/1 598) and 25.0% (400/1 598), while 38.2% (126/330)and 25.3% (21/83) in CSF metagenomics next generation sequencing and Streptococcus pneumoniae antigen detection. There were 4.3% (32/790) cases of which CSF white blood cell counts were normal in etiology confirmed group. Among 1 610 children with ABM, main intracranial imaging complications were subdural effusion and (or) empyema in 349 cases (21.7%), hydrocephalus in 233 cases (14.5%), brain abscess in 178 cases (11.1%), and other cerebrovascular diseases, including encephalomalacia, cerebral infarction, and encephalatrophy, in 174 cases (10.8%). Among the 166 cases (10.3%) with unfavorable outcome, 32 cases (2.0%) died among whom 24 cases died before 1 year of age, and 37 cases (2.3%) had recurrence among whom 25 cases had recurrence within 3 weeks. The incidences of subdural effusion and (or) empyema, brain abscess and ependymitis in the etiology confirmed group were significantly higher than those in the clinically diagnosed group (26.2% (207/790) vs. 17.3% (142/820), 13.0% (103/790) vs. 9.1% (75/820), 4.6% (36/790) vs. 2.7% (22/820), χ²=18.71, 6.20, 4.07, all P<0.05), but there was no significant difference in the unfavorable outcomes, mortility, and recurrence between these 2 groups (all P>0.05). Conclusions: The onset age of ABM in children is usually within 1 year of age, especially <3 months. The common pathogens in infants <3 months of age are Escherichia coli and Streptococcus agalactiae, and the dominant pathogen in infant ≥3 months is Streptococcus pneumoniae. Subdural effusion and (or) empyema and hydrocephalus are common complications. ABM should not be excluded even if CSF white blood cell counts is within normal range. Standardized bacteriological examination should be paid more attention to increase the pathogenic detection rate. Non-culture CSF detection methods may facilitate the pathogenic diagnosis.
Adolescent ; Brain Abscess ; Child ; Child, Preschool ; Escherichia coli ; Female ; Humans ; Hydrocephalus ; Infant ; Infant, Newborn ; Male ; Meningitis, Bacterial/epidemiology* ; Retrospective Studies ; Streptococcus agalactiae ; Streptococcus pneumoniae ; Subdural Effusion ; beta-Lactamases