The role of SnRK2 in the response to stress, the growth and development of plants / 生物工程学报

Sucrose non-fermenting-1-related protein kinase 2 (SnRK2) is a specific Ser/Thr protein kinase in plants. SnRK2 can regulate the expression of downstream genes or transcription factors through phosphorylation of substrates to achieve stress resistance regulation in different tissue parts, and make plants adapt to adverse environment. SnRK2 has a small number of members and a molecular weight of about 40 kDa, and contains a conserved N-terminal kinase domain and a divergent C-terminal regulatory domain, which plays an important role in the expression of enzyme. This review summarized the recent research progresses on the discovery, structure, and classification of SnRK2, and its function in response to various stresses and in regulating growth and development, followed by prospecting the future research direction of SnRK2. This review may provide a reference for genetic improvement of crop stress resistance.

Isolation and Antibiotic Resistance of Achromobacter xylosoxidans from Non-respiratory Tract Clinical Samples: A 10-year Retrospective Study in a Tertiary-care Hospital in Hungary

Aims: To assess the prevalence of A. xylosoxidansisolated from non-respiratory tract samples from adult inpatients and outpatients and the antibiotic resistance levels at a tertiary-care teaching hospital in Szeged, Hungary retrospectively, during a 10-year study period.Study Design:Retrospective microbiological study.Place and Duration of Study:1stof January 2008 -31stof December 2017 at the University of Szeged, which is affiliated with the Albert Szent-Györgyi Clinical Center, a primary-and tertiary-care teaching hospital in the Southern GreatPlain of Hungary.Methodology:Data collection was performed electronically. Antimicrobial susceptibility testing (AST) was performed using disk diffusion method and when appropriate, E-tests on Mueller–Hinton agar plates. Results:During the 10-year study period, a total of 68 individual A. xylosoxidansisolates were identified (6.8±3.6/year, range: 0-11 isolates). The frequency of isolation in the first half of the study period (2008-2017) was n=22, while in 2013-2017, this number was n=46. The majorityof isolates (51 out of 68) were from inpatient departments. 32 out of 68 patients were female (female-to-male ratio: 0.89).The susceptibilities of the respectiveA. xylosoxidansisolates (n=68) were the following: high levels of susceptibility for imipenem and meropenem (n=63; 92.6%), and moxifloxacin (n=55; 80.9%), while higher rates of resistance were detected for sulfamethoxazole/trimethoprim (susceptible: n=36; 52.9%), ciprofloxacin (susceptible: n=40; 58.8%) and almost all isolates were resistant to ceftazidime (susceptible: n=3; 4.4%) and cefepime (n=2; 2.9%).Conclusion:The existing literature on Achromobacterinfections in the context of non-respiratory human infections is scarce, as the incidence of these pathogens in clinically-relevant syndromes in low. The developments in diagnostic technologies in routine clinical microbiology will probably lead to a shift in the isolation frequency of these bacteria in the future

Analysis on the change of distribution of the major non-fermenting bacilli and the sensitivity of antibiotics from 2014 to 2016 / 国际检验医学杂志

Objective To investigate the distribution and antibiotics resistance of the major non-fermenting bacteria in our hospital from 2011 to 2016 ,then provide a reference for clinic practice .Methods Retrospective-ly analyze clinical distribution and antimicrobial susceptibility of 2398 non-fermenting bacteria from 2014 to 2016 .Results Over the past 3 years ,2398 main non fermented bacteria were isolated ,mainly 1019 strains of Acinetobacter Bauman (42 .5％ ) ,followed by Pseudomonas aeruginosa 1016 (42 .4％ ) .The main non fermen-tative bacteria isolated from ICU were 727 strains (30 .3％ ) ,ranking the first in all departments ,and the Acin-etobacter Bauman was the top .The sensitivity rate of Acinetobacter Bauman to antibiotics was decreasing year by year ,as low as 25 .0％ -40 .0％ .Especially in ICU ,the sensitivity rates were less than 10 .0％ .The suscep-tibility rates of Pseudomonas aeruginosa to a variety of antibiotics ,such as ceftazidime ,cefepime ,imipenem , ciprofloxacin ,levofloxacin ,were all increased ,and the sensitivity was >70 .0％ .Conclusion Acinetobacter and Pseudomonas aeruginosa were the main pathogenic bacteria in the clinical distribution of non fermenting bacte-ria .The most sensitive rate of the former to antibiotics was decreasing year by year ,especially the ICU situa-tion was severe ,the sensitivity of the latter was increasing year by year ,which was beneficial to the clinical se-lection of antimicrobial agents .

Superbugs causing ventilator associated pneumonia in a tertiary care hospital and the return of pre‑antibiotic era.

The rise in super bugs causing Ventilator‑Associated Pneumonia (VAP) is a major cause of mortality and morbidity despite recent advances in management owing to the looming ‘antibiotic apocalypse’. The aetiology and susceptibility pattern of the VAP isolates varies with patient population, type of intensive care unit (ICU) and is an urgent diagnostic challenge. The present study carried out for a period of one year in a tertiary care hospital, enrolled patients on mechanical ventilation (MV) for ≥48 hrs. Endotracheal aspirates (ETA) from suspected VAP patients were processed by semi quantitative method. Staphylococus aureus, members of Enterobacteriaceae were more common in early onset VAP (EOVAP), while Nonfermenting Gram negative bacilli (NFGNB) were significantly associated with late onset VAP (LOVAP). Most of the isolates were multi drug resistant (MDR) super bugs. With limited treatment options left for this crisis situation like the pre‑antibiotic era; it is an alarm for rational antibiotic therapy usage and intensive education programs.

Bacilos gramnegativos no fermentadores en agua embotellada: susceptibilidad antimicrobiana y formación de biopelículas / Non fermenting Gram negative bacilli in bottled water: antimicrobial susceptibility and biofilms formation

El agua puede ser un vehículo para agentes patógenos y oportunistas portadores de multiresistencia y con capacidad de formar biopelículas (CFB). Se evaluó la presencia de indicadores microbiológicos y bacilos gramnegativos no fermentadores (BGNNF) en agua potable envasada y se estudió la susceptibilidad antimicrobiana y la CFB de los mismos. Se seleccionaron al azar 50 muestras de 250 mL obtenidos de envases de agua potable (20 L), provenientes de igual número de hogares. A cada muestra le fue realizado recuento de heterótrofos aerobios (vertido en placa), coliformes totales y termotolerantes (filtración por membrana), CFB (microplaca) y susceptibilidad antimicrobiana (Kirby-Bauer). El 92% y el 84% de las muestras presentaron coliformes totales y termotolerantes respectivamente, valores por encima de lo establecido en la Gaceta Oficial Venezolana N.° 36.395, mientras que el 86% presentó heterótrofos aerobios con cuentas >100 UFC/mL. El mayor porcentaje de BGNNF aislados pertenecía al complejo Acinetobacter baumannii/calcoaceticus (29,3%), seguido de Pseudomonas aeruginosa (17,4%), con moderada capacidad de formar biopelículas. No hubo asociación significativa entre la resistencia antimicrobiana y la CFB (p>0,05). Un porcentaje elevado de las muestras, no se ajustó a los parámetros microbiológicos establecidos en Gaceta, por lo que no se garantiza la inocuidad de las mismas.

Water can be a vehicle for multiresistant carrier pathogenic and opportunist agents with biofilm forming capacity (BFC). The presence of microbiological indicators and non fermenting Gram negative bacilli (NFGNB) was evaluated in bottled drinking water, as well as their antimicrobial susceptibility and BFC. Fifty 250 mL drinking water samples were randomly selected from 20 L drinking water bottles from the same number of homes. Each sample was tested for aerobic heterothrophics (discharged in a plate) counts, total and thermo tolerant coliforms (membrane filtration), BFC (microplate) and antimicrobial susceptibility (Kirby-Bauer). The results showed that 92% and 84% of the samples carried total and thermo tolerant coliforms respectively, values above those established in the Venezuelan Official Gazette N.o 36,395, while 86% presented aerobic heterothrophics with counts >100 CFU/mL. The highest percentage of isolated NFGNBs belonged to the Acinetobacter baumannii/calcoaceticus complex (29.3%), followed by Pseudomonas aeruginosa (17.4%) which has a moderate biofilm formation capacity. There was no significant association between antimicrobial resistance and the BFC (p>0.05). A high percentage of the samples were not adjusted to the biological parameters established in the Official Government Gazette; therefore, it is not possible to guarantee their safety.

Lower respiratory tract in patients with malignant tumor of fermentation bacteria infection of bacterial drug resistance analysis / 国际检验医学杂志

Objective To understand the drug resistance in cancer patients with secondary non-fermenting bacterial lower respir-atory tract infection in order to provide a basis for clinical rational use of antibacterial drugs.Methods The lower respiratory tract specimens were collected from the patients with malignant tumor and identified by the fully automated microbial identification sys-tem,the drug susceptibility test was performed by using K-B method and the drug susceptibility test results were judged according to CLSI 2012 standard.The data were analyzed by the WHONET 5.6 software.Results 172 strains of non-fermenting bacteria were isolated from the lower respiratory tract specimens in the patients with malignant tumors,in which Pseudomonas aeruginosa was maximum,accounted for 45.9%,followed by Acinetobacter baumannii and Stenotrophomonas maltophilia ,accounted for 36. 0% and 10.5 % respectively.The drug susceptibility test showed that five kinds of non-fermenter demonstrated the high resistance or multi-resistance to multiple antibacterial drugs.Conclusion Non-fermenting bacterial multi-drug resistant phenomenon is seri-ous,clinic should pay attention to non-fermenting bacterial infection and drug resistance monitoring,antibacterial drugs should be rationally used according to the drug susceptibility test results in order to reduce the generation of drug-resistant strains.

Distribution and antibiotic resistance profile of nonfermentative gram negative bacteria / 中国感染与化疗杂志

Objective To investigate the clinical distribution and antibiotic resistance of the nonfermenting bacterial strains isolated in Beijing Anzhen Hospital from 2008 to 2012.Methods The bacteria were identified by VITEK-compact system and Phoenix 100 system. Antimicrobial susceptibiity was tested by dilution method. Results A total of 2 450 strains of nonfermentative gram-negative bacteria were isolated from clinical specimens. Acinetobacter baumannii, Pseudomonas aeruginosa and Stenotrophomonas maltophilia accounted for 57.2%,25.5% and 10.0%.Specimens were mostly collected from respiratory tract (80.9%),followed by blood (8.1%)and wound exudates (3.9%).The strains were mainly collectd from ICU (50.0%),cardiac surgery ward (17.0%)and respiratory medical ward (11.5%).The prevalence of imipenem-resistant A.baumannii was 62.3%,79.2%,70.4%,76.1%,67.8% from 2008 to 2012.The prevalence of imipenem-resistant P.aeruginosa was 28.7%,25.0%,27.6%,31.1% and 32.0%.S.maltophilia strains showed the highest susceptibility to trimethoprim-sulfamethoxazole and levofloxacin.Conclusions The high prevalence of antibiotic-resistant non-fermenting bacteria poses a great challenge to clinicins. The rational treatment choice should be based on the result of suseptibility testing.

Metallo-β-lactamase-production in meropenem-susceptible Pseudomonas aeruginosa isolates: risk for silent spread

The aim of this study was to characterize two metallo-β-lactamases (MBLs)-producing Pseudomonas aeruginosa clinical isolates showing meropenem susceptibility. Antimicrobial susceptibility was assessed by automated testing and Clinical and Laboratory Standards Institute agar dilution method. MBL production was investigated by phenotypic tests. Molecular typing was determined by pulsed field gel electrophoresis (PFGE). MBL-encoding genes, as well as their genetic context, were identified by polymerase chain reaction (PCR) and sequencing. The location of blaIMP-16 was determined by plasmid electrophoresis, Southern blot and hybridization. Transcriptional levels of blaIMP-16, mexB, mexD, mexF, mexY, ampC and oprD were determined by semi-quantitative real time PCR. The P. aeruginosa isolates studied, Pa30 and Pa43, showed imipenem and meropenem susceptibility by automated testing. Agar dilution assays confirmed meropenem susceptibility whereas both isolates showed low level of imipenem resistance. Pa30 and Pa43 were phenotypically detected as MBL producers. PFGE revealed their clonal relatedness. blaIMP-16 was identified in both isolates, carried as a single cassette in a class 1 integron that was embedded in a plasmid of about 60-Kb. Pa30 and Pa43 overexpressed MexAB-OprM, MexCD-OprJ and MexXY-OprM efflux systems and showed basal transcriptional levels of ampC and oprD. MBL-producing P. aeruginosa that are not resistant to meropenem may represent a risk for therapeutic failure and act as silent reservoirs of MBL-encoding genes.

Prevalência de bacilos Gram-negativos não fermentadores de pacientes internados em Porto Alegre-RS / Prevalence of non-fermenting Gram-negative bacilli among inpatients from Porto Alegre-RS

INTRODUÇÃO: Os bacilos Gram-negativos não fermentadores (BGNNF) são frequentemente associados às infecções hospitalares. Além da alta incidência, esses microrganismos possuem resistência a diversos antimicrobianos. OBJETIVO: Analisar a prevalência e o perfil de resistência de BGNNF. MÉTODOS: Foram analisados 14.971 laudos de pacientes em um hospital privado de Porto Alegre-RS, no período de maio de 2006 a março de 2008, sem distinção de sexo e idade. RESULTADOS E CONCLUSÃO: Foram isoladas 326 amostras de BGNNF. As espécies mais prevalentes foram: Pseudomonas aeruginosa (65,03 por cento), Acinetobacter baumannii (16,56 por cento) e Stenotrophomonas maltophilia (9,5 por cento). Outras espécies apresentaram índices inferiores a 5 por cento. Os microrganismos foram isolados de diversos sítios infecciosos. Os materiais biológicos que apresentaram maior positividade para esses microrganismos foram o aspirado traqueal (38,34 por cento), o escarro (18,71 por cento) e a urina (15,95 por cento). A resistência bacteriana mostrou-se mais expressiva a tetraciclinas (89,57 por cento) e sulfametoxazol/trimetoprima (79,75 por cento). Os antimicrobianos mais ativos foram polimixina B, com 100 por cento de sensibilidade, e piperaciclina/tazobactam, com 75,2 por cento de sensibilidade.

INTRODUCTION: The non-fermenting Gram-negative bacilli (NFGNB) have been widely associated with nosocomial infections. Not only are these microorganisms highly prevalent but they are also highly resistant to NFGNB. OBJECTIVE: To assess the prevalence and resistance profile of non-fermenting Gram-negative bacilli. METHODS: 14.971 patient reports from a private hospital in Porto Alegre, Rio Grande do Sul, from May/2006 to March/2008 were analyzed. RESULTS AND CONCLUSION: Three hundred twenty-six samples of non-fermenting Gram-negative bacilli were isolated. The most prevalent species were Pseudomonas aeruginosa (65.03 percent), Acinetobacter baumannii (16.56 percent), and Stenotrophomonas maltophilia (9.5 percent). Other species showed rates lower than 5 percent. The microorganisms were isolated from several infectious sites and the biological materials that showed higher positivity were the following: tracheal aspirate (38.34 percent), spittle (18.71 percent) and urine (15.95 percent). Bacterial resistance was higher with tetracyclines (89.57 percent) and sulfamethoxazole/trimethoprim (79.75 percent). The most active antimicrobials were polymyxin B and piperacillin/tazobactam with 100 percent and 75.2 percent sensibility, respectively.

Criterios de ensayo, interpretación e informe de las pruebas de sensibilidad a los antibióticos en los bacilos gram negativos no fermentadores de importancia clínica: recomendaciones de la Subcomisión de Antimicrobianos de la Sociedad Argentina de Bacteriología, Micología y Parasitología Clínicas, Asociación Argentina de Microbiología / Antimicrobial susceptibility testing in clinically relevant non-fermenting gram-negative bacilli: recommendations from the Antimicrobial Agents Subcommittee of the Sociedad Argentina de Bacteriología, Micología y Parasitología Clínicas, Asociación Argentina de Microbiología

En este documento se dan a conocer una serie de recomendaciones para el ensayo, la lectura, la interpretación y el informe de las pruebas de sensibilidad a los antimicrobianos para los bacilos gram negativos no fermentadores (BGNNF) que se aíslan en humanos. Se adoptaron como base las recomendaciones internacionales, las de la Subcomisión de Antimicrobianos de la Sociedad Argentina de Bacteriología, Micología y Parasitología Clínicas y las de un grupo de expertos invitados. Se incluye, además, la nomenclatura actualizada de los BGNNF y la descripción de algunas de sus características individuales, de sus resistencias naturales o habituales a los antimicrobianos de uso clínico y de los mecanismos responsables de tales resistencias. También se indican los agentes antimicrobianos que se deberían ensayar frente a las distintas especies, con la especificación de cuáles deberían ser informados, y su ubicación estratégica en las placas de cultivo para poder detectar los mecanismos de resistencia más frecuentes y relevantes. Por último, se detallan los métodos de detección y de confirmación fenotípica de la presencia de b-lactamasas emergentes en Argentina, como las carbapenemasas clases A y B.

This document contains the recommendations for antimicrobial susceptibility testing of the clinically relevant non-fermenting gram-negative bacilli (NFGNB), adopted after conforming those from international committees to the experience of the Antimicrobial Agents Subcommittee members and invited experts. This document includes an update on NFGNB classification and description, as well as some specific descriptions regarding natural or frequent antimicrobial resistance and a brief account of associated resistance mechanisms. These recommendations not only suggest the antimicrobial drugs to be evaluated in each case, but also provide an optimization of the disk diffusion layout and a selection of results to be reported. Finally, this document also includes a summary of the different methodological approaches that may be used for detection and confirmation of emerging b-lactamases, such as class A and B carbapenemases.

Enumeration and identification of gram negative bacteria present in soil underlying urban waste-sites in southwestern Nigeria.

Samples of soils underlying wastes were collected from four sites representing four demographic regions of a medium sized town in southwestern Nigeria. Standard methods and reference strains of isolated bacteria were employed for identification. Evaluation of the enzymatic and biochemical reactions showed that all isolated and identified microbes were non-fermenting heterotrophic (HTB). For example, Klebsiella pnemuniae may be involved in wound infections, particularly following bowel surgery. Similarly, Pseudomonas aeruginosa can produce serious nosocomial infections if it gains access to the body through wounds or intravenous lines. From the 15 culure plates, 88 colonies with various characteristics were enumerated. They differed in aspect of viscosity and color. The bacterial species were identified by percent positive reactions while oxidative and sugar fermentation tests revealed various characteristics among the isolated strains. All of the isolates were negative for citrate utilization, gelatin liquefaction, nitrate reduction, methyl red and Voges Proskaur, motility and hydrogen sulphate production. The quantity of HTB present in an area serves as an index of the general sanitary conditions of that area. The presence of a large number of HTB, in an ecological area may be considered a liability, as it can enhance the spread of diseases and on a larger scale may enable epidemics to arise. Therefore, there is need for control of waste sites by recovery and regular germicidal sanitation.

Ocorrência de bactérias clinicamente relevantes nos resíduos de serviços de saúde em um aterro sanitário brasileiro e perfil de susceptibilidade a antimicrobianos / Occurrence of clinically relevant bacteria in health service waste in a Brazilian sanitary landfill and antimicrobial susceptibility profile

Os resíduos de serviços de saúde suscitam polêmica quanto a importância para a saúde humana, animal e ambiental. Avaliou-se a ocorrência de bactérias clinicamente relevantes na pilha de resíduos de serviços de saúde em um aterro sanitário e seu perfil de susceptibilidade aos antimicrobianos. Alíquotas de chorume foram processadas para isolamento seletivo de Staphylococcus sp, bastonetes Gram negativos da família Enterobacteriaceae e não fermentadores. Resistência bacteriana a todos os antimicrobianos testados foi observada em todos os grupos microbianos, além de resistência a mais de uma droga. Os resultados permitem sugerir que bactérias viáveis nos resíduos de serviços de saúde representam riscos à saúde humana e animal. Além disso, a ocorrência de linhagens multirresistentes sustenta a hipótese dos resíduos de serviços de saúde atuarem como reservatórios de marcadores de resistência, com impacto ambiental. A falta de legislação regional de segregação, tratamento e destino de resíduos podem expor diferentes populações a riscos de transmissão de doenças infecciosas associadas a microrganismos multirresistentes.

Health service waste gives rise to controversy regarding its importance for human, animal and environmental health. Occurrences of clinically relevant bacteria in piles of health service waste in a sanitary landfill and their antimicrobial susceptibility profile were evaluated. Aliquots of leachate were processed for selective isolation of Staphylococcus sp, Gram-negative rods of the Enterobacteriaceae family and non-fermenters. Bacterial resistance to all the antimicrobials tested was observed in all microbial groups, including resistance to more than one drug. The results make it possible to suggest that viable bacteria in health service waste represent risks to human and animal health. Furthermore, occurrences of multiresistant strains support the hypothesis that health service waste acts as a reservoir for resistance markers, with an environmental impact. The lack of regional legislation concerning segregation, treatment and final disposal of waste may expose different populations to risks of transmission of infectious diseases associated with multiresistant microorganisms

Surveillance of Antimicrobial Resistance and Classification in Non-fermenting Bacteria Isolated from Lower Respiratory Tract for 3 Consecutive Years / 中华医院感染学杂志

OBJECTIVE To investigate the distribution and resistance of non-fermenting bacteria isolated from our hospital and offer the basis for the treatment of bacterial infection.METHODS Totally 2177 strains of non-fermenting bacteria were isolated from clinical sputum samples between Jan 2006 and Dec 2008.All of the isolated bacteria were identified with API identified test(API Inc,France) and Kirby-Bauer(K-B) test used for the antibiotics susceptive test.RESULTS From them the most common bacteria were Pseudomonas auruginosa(34.9%),followed by Acinetobacter baumannii(28.4%) and Stenotrophomonas maltophilia(11.4%).These bacteria had various resistances to the tested antibiotics.CONCLUSIONS Non-fermenting bacteria have high isolate rate and multi-antibiotic resistance,so antibiotics should be correctly used under the guidance of antibiotic susceptibility test.

Identification of protein kinase SNF1 in CitEST

SnRKs (Sucrose non-fermenting-1 related kinases) is a family of protein kinases found in many crops, such as Arabidopsis, rice, sugarcane, tomato and several other plant species. This family of proteins is also present in other organisms like Saccharomyces cerevisiae (sucrose non-fermenting-1 - Snf1) and in mammals (AMP-activated protein kinases - AMPKs). There is evidence that SnRKs play an important role in plant responses to nutritional and environmental stresses and that SnRKs also play a major role in controlling key enzymes in the biosynthetic pathways of plants. In this work, we identified 18 contigs and two singletons encoding putative SnRKs in the CitEST database. All of them present highly conserved N-terminal catalytic domain, which is found in the SnRKs families of several plant species. Through comparison with known SnRKs, we were able to classify them into three subfamilies.

Isolation and Identification of 236 Strains Non-fermenting Bacteria and Their Antibiotic Resistance Analysis / 医学研究杂志

Objective To investigate the distribution and resistance of non-fermenting bacteria isolated from our hospital and offer a basis for the treatment of bacterial infection.Methods 236 strains of non-fermenting bacteria were isolated from clinical samples between May.2004 and Dec.2006were identified with API identified test (API Inc.France) and Kirby-Bauer (K-B) test used for the antibiotics susceptivity test. Results Totally 236 strains of non-fermenting bacteria were isolated from the 1303 pathogenic strains. The most common bacteria were Pseudomonas auruginosa(57.6%),followed by Acinetobacter baumannii(7.6%)and Pseudomonas putida(6.4%).64%of non-fermenting bacteria were isolated from the sputum. these bacteria had various resistance to all detected antibiotics. Conclusions non-fermenting bacteria had high isolated rate and multi-antibiotic resistance,so antibiotics should be correctly under the guidance of antibiotic susceptibility testing.

Isolation and Identification of Non-fermenting Bacteria and Their Antibiotic Resistance Analysis / 中华医院感染学杂志

OBJECTIVE To investigate the distribution and resistance of non-fermenting bacteria isolated from(patients) in 2005 and offer a basis for the treatment of bacterial infection.METHODS The isolated bacteria were(identified) with API identified test(API Inc,France) and Kirby-Bauer(K-B) test used for the antibiotics(susceptivity) test.The data were analyzed by using WHONET-5 software.RESULTS Totally 604 strains of non-fermenting bacteria were isolated from the 2908 pathogenic strains.The most common bacteria were Pseudomonas aeruginosa(52.32%),followed by Stenotrophomonas maltophilia(14.07%) and Acinetobacter baumannii((13.74%)).76.32% of non-fermenting bacteria were isolated from the sputum.These bacteria had various(resistances) to all detected antibiotics.CONCLUSIONS Non-fermenting bacteria have high isolation rate and(multi-drug) resistance,so antibiotics should be used correctly under the guidance of antibiotic susceptibility testing.