多重耐药伤寒沙门菌耐药基因的研究

目的 检测多重耐药伤寒沙门菌对抗菌药物的敏感性及其耐药基因定位。方法 随机选取实验室保存的5株耐药菌和1株敏感菌,用纸片扩散法检测对12种抗菌药物的敏感性。用利舍平抑制试验检测菌株是否存在药物外排系统。PCR法检测TEM型β-内酰胺酶基因、aac(6′)-Ⅰb和aac3-Ⅱ型氨基糖苷类修饰酶基因、qacEΔ1-sul1耐消毒剂和磺胺基因、catA和catB氯霉素乙酰基转移酶基因以及cmlA氯霉素外排泵蛋白基因等7种耐药基因。结果 5株多重耐药菌对氨苄西林、哌拉西林、头孢呋辛、头孢西丁、卡那霉素、庆大霉素、复方磺胺甲噁唑及氯霉素等8种抗菌药物全部耐药,对美罗培南、头孢哌酮、头孢吡肟全部敏感;对头孢噻吩中度敏感。1株无质粒pRST98的菌株对上述药物全部敏感。利舍平抑制试验均为阴性。4株耐药菌TEM型β-内酰胺酶基因检测为阳性。全部耐药菌株aac3-Ⅱ、qacEΔ1-sul1、catA基因均为阳性,而aac(6′)-Ⅰb、catB和cmlA基因均为阴性。 结论 多重耐药伤寒沙门菌质粒pRST98上同时存在多种耐药基因, 是导致菌株同时对多种结构各异的抗生素耐药的原因。     

Prevalence of Malaria in Pregnant Women in Lagos, South-West Nigeria

Prevalence rates reported for malaria in pregnancy in Nigeria vary considerably. The accuracy of results of malaria diagnosis is dependent on training, experience, and motivation of the microscopist as well as the laboratory facility available. Results of training programmes on malaria microscopy have shown low levels of sensitivity and specificity of those involved in malaria diagnosis routinely and for research. This study was done to ascertain the true prevalence of malaria in pregnancy in Lagos, South-West Nigeria. A total of 1,084 pregnant women were recruited into this study. Blood smears stained with Giemsa were used for malaria diagnosis by light microscopy. Malaria infection during pregnancy presents mostly as asymptomatic infection. The prevalence of malaria in this population was 7.7% (95% confidence interval; 6.2-9.4%). Factors identified to increase the risk of malaria infection include young maternal age (< 20 years), and gravidity (primigravida). In conclusion, this study exposes the over-diagnosis of malaria in pregnancy and the need for training and retraining of laboratory staffs as well as establishing the malaria diagnosis quality assurance programme to ensure the accuracy of malaria microscopy results at all levels.     

Characteristics of lipopolysaccharides ofSalmonella typhi isolated from carriers and patients suffering from typhoid fever

Lipopolysaccharides (LPS) ofSalmonella typhi strains, isolated from carriers and patients suffering from typhoid fever, were characterised according to their biochemical properties, morphological structure and degree of aggregation of complexes. All preparations of LPS, regardless of their origin, were morphologically heterogeneous. Free electrophoresis and immunoelectrophoresis demonstrated that LPS preparations were composed of components possessing different mobilities in electric fields. LPS of bacterial strains isolated from both carriers and patients, split upon reaction in immunoelectrophoresis with specific antiserum 73, rabbit antiserum toSalmonella typhi Vi Bhatnagar and 0–901 split into anodic and cathodio fractions. The anodic fraction reacted similarly as Vi antigen. LPS fromSalmonella typhi Ty-2 yielded only the cathodic fraction, typical for O antigen. LPS from strains whioh were passaged twice in nutritional medium possessed identical properties as LPS from fresh cultures ofSalmonella typhi. Electron microscopy revealed that LPS appears as long bands, rods, ellipsoid forms and amorphous material. Contrary to amorphous material, the bands, rods and ellipsoid forms possessed three-layer structure.     

Detection of microbial variants of Salmonella typhi in the bone marrow of typhoid patients and carriers

The immunofluorescence test with the use of antisera to S. typhi and its L-forms permits the detection of the infective agent in bone marrow smears. This diagnostic method is particularly important in cases of carrier state in the latent phase and in differential diagnosis. As revealed in this study, the microbial variants of S. typhi, reacting with antiserum to its L-forms, are present in the bone marrow of carriers. They are localized, as a rule, on the membranes of lymphoid and erythroid cells, which probably leads to the formation of rosettes.     

Surveillance for typhoid fever in Matsuyama city during 1974-1981 and detection of Salmonella typhi in sewage and river waters

Eighty-two cases of typhoid fever were found in Matsuyama city in the period from 1974 to 1981. Seventy-six cases were found to be infected with Salmonella typhi other three with Salmonella paratyphi A, and the remaining three were diagnosed only clinically. The strains of S. typhi isolated from these patients showed such a variety of Vi-phage types as D1, D2, E1, M1, 53 and degraded Vi-positive strain (DVS). The concurrent survey of the city sewage and river waters for typhoid bacilli was conducted with total 578 samples taken therefrom. S. typhi was isolated from 120 of those samples. The Vi-phage types of the isolates were closely related with those of the isolates from the patients. The periodical examinations of the city sewage and the draining river may serve as a useful means for the controlling typhoid fever epidemics.     

Isolation of a highly purified capsular polysaccharide from Salmonella enterica serovar Typhi (Salmonella typhi)--Vi-antigen and its use in serological diagnosis of typhoid fever

For use in differential diagnostics of typhoid fever, samples of the capsular polysaccharide from Salmonella enterica serovar Typhi (usually named Vi-antigen) were isolated and characterized by physicochemical and serological methods. It was shown that only the sample of Vi-antigen with the minimal (0.57%) admixture of the corresponding lipopolysaccharide (LPS) from S. typhi retained a high serological activity in the tests with monoreceptor anti-Vi sera. However, it exhibited a substantially weaker reaction with sera from normal donors and patients with acute nontyphoid salmonelloses, than Vi-antigen preparations with a higher (0.8-1.2%) LPS content. The chromatographically pure Vi-antigen was purified by triple reprecipitation with hexadecyltrimethylammonium bromide. The content of the LPS admixture in the resulting Vi-antigen samples was quantitatively determined by GC. A high purification level of the Vi-antigen from the LPS admixture allows us to hope that this preparation could serve as a basic component of the test system for the diagnostics of typhoid fever. The English version of the paper.     

The function of Salmonella typhi at different stages in the pathogenesis of typhoid infection

The complex study of the adhesive, colicinogenic and antigenic properties of S. typhi of different origin has revealed that adhesive properties can be observed more frequently in the strains isolated from the blood and bile and are completely absent in the strains isolated from feces. S. typhi strains of various origin do not essentially differ in their sensitivity to colicins and in the capacity for their production. Among the strains isolated from feces and bile, agents in the W-form occur more frequently than among the strains isolated from the blood. Escherichia coli, isolated from typhoid patients and carriers at the moment of the persistence of S. typhi in the body, are characterized by faintly pronounced antagonistic properties, enhanced sensitivity to colicins and rather pronounced hemagglutinating activity.     

大连市伤寒沙门菌耐药性及耐药基因分析

目的检测多重耐药伤寒沙门菌对抗菌药物的敏感性及其耐药基因携带情况,为伤寒沙门菌引起的腹泻治疗提供科学依据。方法采用微量肉汤稀释的方法测定大连地区临床分离的78株伤寒沙门菌对12种抗生素的敏感性;用PCR方法检测TEM型β内酰胺酶基因、catA和catB氯霉素乙酰基转移酶基因以及cmlA氯霉素外排泵蛋白基因、aac(6′)Ⅰb和aac3Ⅱ型氨基糖苷类修饰酶基因、qacEΔ1sul1耐消毒剂和磺胺基因、多重耐药外排基因acrB等8种耐药基因。结果78株沙门菌对12种药物有不同程度耐药(1.28%~74.35%)。得到9株多重耐药菌株,其中5株检出TEM型β内酰胺酶基因;7株耐氯霉素的伤寒沙门菌菌株中,2株仅检出catA基因,1株仅检出catB基因,1株仅检出cmlA氯霉素外排泵蛋白基因,2株同时检出catA基因和cmlA氯霉素外排泵蛋白基因;2株检出aac(6′)Ⅰb基因,1株检出aac3Ⅱ型氨基糖苷类修饰酶基因;4株检出耐消毒剂和磺胺基因qacEΔ1sul1;6株检出多重耐药外排基因acrB。结论大连地区临床分离的伤寒沙门菌存在严峻的耐药现象,多种耐药基因存在于耐药伤寒沙门菌中,可能是导致菌株对多种抗菌药物耐药的原因。     

Animal models of Salmonella infections: enteritis versus typhoid fever.

The most common disease syndromes caused by Salmonella serotypes in humans, typhoid fever and enteritis, can be modeled using Salmonella enterica serotype Typhimurium infections in mice and calves, respectively. This article reviews murine typhoid and bovine enteritis and discusses strengths, limitations and distinctive features of these animal models.     

Antibacterial efficacy of in-house designed cell-penetrating peptide against multi-drug resistant strains of Salmonella Enteritidis and Salmonella Typhimurium

The in vitro antibacterial efficacy of an in-house designed cell-penetrating peptide (CPP) variant of Cecropin A (1–7)-Melittin (CAMA) (CAMA-CPP) against the characterized multi-drug resistant (MDR) field strains of Salmonella Enteritidis and Salmonella Typhimurium were evaluated and compared with two identified CPPs namely, P7 and APP, keeping CAMA as control. Initially, the minimum inhibitory concentration (MIC) (μg ml⁻¹) of in-house designed CAMA-CPP, APP and CAMA was determined to be 3.91, whereas that of P7 was 7.81; however, the minimum bactericidal concentration (MBC) of all the peptides were twice the MIC. CAMA-CPP and CAMA were found to be stable under different conditions (high-end temperatures, proteinase-K, cationic salts, pH and serum) when compared to the other CPPs. Moreover, CAMA-CPP exhibited negligible cytotoxicity in HEp-2 and RAW 264.7 cell lines as well as haemolysis in the sheep and human erythrocytes with no adverse effects against the commensal gut lactobacilli. In vitro time-kill assay revealed that the MBC levels of CAMA-CPP and APP could eliminate the intracellular MDR-Salmonella infections from mammalian cell lines; however, CAMA and P7 peptides were ineffective. CAMA-CPP appears to be a promising antimicrobial candidate and opens up further avenues for its in vivo clinical translation.     

Genomic characterization of a multi-drug resistant,CTX-M-65-producing clinical isolate of Salmonella Infantis isolated in Brazil

A multi-drug resistant, CTX-M-65 producing Salmonella Infantis was identified from a patient in Brazil. Whole genome sequencing followed by hybrid assembly (short and long reads) indicated the presence of bla_CTX-M-65 in a pESI-like megaplasmid in this ST32 isolate and phylogenetic analysis showed high similarity with IncFIB S. Infantis isolates from food and poultry in the USA.