Invasive group A streptococcal infections: T1M1 isolates expressing pyrogenic exotoxins A and B in combination with selective lack of toxin-neutralizing antibodies are associated with increased risk of streptococcal toxic shock syndrome.

Analysis of 132 group A streptococcal (GAS) isolates from 151 invasive episodes, including streptococcal toxic shock syndrome (STSS), from 1983 to 1995 showed great genetic variation by use of T serotyping in combination with restriction fragment length polymorphism. In contrast, genetically homogenous T1M1 isolates appeared in epidemic patterns with significantly increased risk of STSS. The speA gene, with the allelic variants speA2 and speA3 carried by the T1M1 and T3M3 serotypes, respectively, was strongly associated with STSS. Infection with a GAS isolate carrying speA, alcohol abuse, and malignancy recently treated with cytostatic drugs were factors independently related to STSS. Neutralization of SpeA lymphocyte mitogenicity was totally absent in sera from patients with STSS and low in sera from persons with uncomplicated bacteremia compared with levels in sera from uncomplicated erysipelas. Neutralization of SpeB was significantly lower in sera of patients with STSS than in sera from persons with bacteremia or erysipelas.     

Low antibody levels against cell wall-attached proteins of Streptococcus pyogenes predispose for severe invasive disease

Acute-phase serum samples from 70 patients with group A streptococcal (GAS) invasive disease were analyzed for IgG antibodies against 6 recently characterized GAS virulence factors (SclA, SclB, GRAB, MtsA, EndoS, and IdeS) and SpeB. Antibody levels against the cell wall-attached GAS antigens SclA, SclB, and GRAB were significantly lower in patients with severe invasive disease (streptococcal toxic shock syndrome [STSS] and/or necrotizing fasciitis [NF]; n=35), compared with levels in patients with nonsevere GAS bacteremia (n=35). Among patients with severe invasive disease, significantly lower antibody levels against GRAB were found in patients with STSS (n=10) than in patients with NF (n=17). Antibody levels against SpeB in patients with severe bacteremia were similar to those in patients with nonsevere bacteremia, and levels in patients with STSS were similar to those in patients with NF. The data indicate that immunity to cell wall-attached proteins may play a role in the protection against severe invasive disease and that antibodies against GRAB may be of importance in the pathogenesis of STSS.     

外科住院患者感染耐甲氧西林凝固酶阴性葡萄球菌的耐药基因检测及耐药性分析

目的对南京市外科住院患者感染的耐甲氧西林凝固酶阴性葡萄球菌的耐药相关基因进行检测,以更好地控制病原菌耐药性,减少外科感染。方法从南京市多家医院外科住院患者各类临床标本分离耐甲氧西林凝固酶阴性葡萄球菌70株,经纯培养获单菌落后进行鉴定,并进行药敏试验,然后对耐药基因进行PCR测序,对PCR扩增产物进行电泳检测并记录。结果耐甲氧西林凝固酶阴性葡萄球菌对于头孢噻肟和红霉素100%耐药,对万古霉素耐药率为0,对其他抗菌药物的耐药率大小依次为:左氧氟沙星>诺氟沙星>氨苄西林>妥布霉素>环丙沙星>克林霉素>头孢曲松>庆大霉素>四环素>利福平。PCR检测耐药基因,3株只携带mecA 1种耐药基因。15株携带2种耐药基因,分别为:ermA+mecA、aac(6′)/aph(2′′)+mecA和aph(3′)-III+mecA和tetM+mecA。29株携带3种耐药基因,携带方式分别为:ermA+aac(6′)/aph(2′′)+mecA、aph(3′)-III+ermA+mecA、ermA+tetM+mecA、aac(6′)/aph(2′′)+aph(3′)-III+mecA、aac(6′)/aph(2′′)+tetM+mecA和tetM+aph(3′)-III+mecA。20株携带4种耐药基因,携带方式分别为:aac(6′)/aph(2′′)+tetM+ermA+mecA、aph(3′)-III+tetM+aac(6′)/aph(2′′)+mecA、aph(3′)-III+tetM+ermA+mecA和aph(3′)-III+aac(6′)/aph(2′′)+ermA+mecA。有3株携带5种耐药基因,即ermA+aph(3′)-III+tetM+aac(6′)/aph(2′′)+mecA。结论耐甲氧西林凝固酶阴性葡萄球菌对常用抗菌药物的耐药性普遍较高,5种耐药基因在菌株中出现的频率不同,但所有病原菌都存在mecA基因,因而该菌的耐药性可能与mecA基因有关。     

Drug susceptibility and analysis using pulsed-field gel electrophoresis of Streptococcus pyogenes strains isolated from the patients with streptococcal toxic shock syndrome (STSS) in Japan

Previously, we have performed T typing of Streptococcus pyogenes strains isolated from patients with streptococcal toxic shock syndrome (STSS) in Japan, and streptococcal pyrogenic exotoxin (SPE) typing for epidemiological examination. In this study, we conducted a drug sensitivity test using these strains, and investigated the results of gene analysis by pulse-field gel electrophoresis (PFGE) of S. pyogenes strains derived from patients with STSS, the patient's family, and patients other than those with STSS. To clarify the relationship between the host and bacterial factors, we investigated the association between clinical symptoms and T typing of the isolated strains/production of streptococcal pyrogenic exotoxin. There were no strains resistant to beta-lactams, and only 1 strain was resistant to multiple agents other than beta-lactams. The PFGE pattern of T1 type strains was classified into 2 ; the pattern was consistent between the strains derived from patients with STSS and those derived from the patient's family. The PFGE pattern of T3 type strains was classified into 5 (IV) ; Pattern I, which was most frequently observed, was detected in both the strains derived from patients with STSS/non-STSS. However, Patterns II and III were detected only in the strains derived from patients with non-STSS. Patterns IV and V were detected only in the strains derived from patients with STSS. When examining the association between clinical symptoms and bacterial factors, disseminated intravascular coagulation (DIC) was associated with T1-SPE B-producing strains, and pharyngitis was associated with T3-SPE A-producing strains. In the future, the relationship between the host and bacterial factors should be further investigated.     

耐红霉素肺炎链球菌的分子生物学研究

目的研究耐红霉素肺炎链球菌的分子生物学特点。方法社区获得性肺炎呼吸道标本分离的肺炎链球菌共45株,进行抗生素药物敏感性试验,对耐药菌株采用PCR方法检测红霉素的耐药基因ermA/ermB/mefA,同时采用脉冲场凝胶电泳技术和青霉素结合蛋白基因多态性追踪耐药菌株之间的同源性,以获得耐药菌株的分子流行病学特点。结果45株肺炎链球菌中对红霉素耐药24株,均为多耐药肺炎链球菌;青霉素耐药14株,其中11株（78.6%）同时耐红霉素。22株（92%）的红霉素耐药株为MLS表型,即同时耐克林霉素,2株为M型耐药。经PCR扩增,20株（83.3%）具有ermA/B基因,6株（25.0%）同时有erm和mef基因,2株（8.3%）只有mef基因,2株未能检测到erm或mef基因。脉冲场凝胶电泳和青霉素结合蛋白基因多态性检测未发现不同地区相同的耐药克隆株。结论erm基因编码的核糖体突变是肺炎链球菌耐红霉素的主要机制,本研究未发现不同地区相同的耐药克隆株。     

Quantitative and qualitative comparison of virulence traits,including murine lethality,among different M types of group A streptococci

Epidemiological studies have proposed an association between group A streptococci (GAS) bearing a particular M serological type and pathologic conditions such as streptococcal toxic shock syndrome (STSS). M1 and M3 GAS are isolated from STSS cases more frequently, whereas M4 and M12 GAS are isolated from non-STSS cases more frequently. To investigate whether there is any difference contributing the M-type association among GAS, we compared various virulence traits, including the murine lethality of M4, M12, M1, and M3 GAS clinical isolates, which are not clonally related to one another. Murine lethality, the activities of superantigens, streptolysin O, and nicotinamide adenine dinucleotide glycohydrolase, and the presence of the speA and speC genes were closely associated with M type. These results indicate that M types may serve, in part, as markers for strains/clones with particular profiles of virulence traits and mouse lethality.     

Emm typing by genetic identification of Streptococcus dysgalactiae subsp. equisimilis and susceptibility to oral antibiotics

A total of 593 beta-hemolytic streptococci belonging to Lancefield group A (GAS), group C (GCS) or group G (GGS) according to agglutination tests were collected from 11 medical institutions between September 2003 and October 2005. In total, 128 strains were identified as Streptococcus dysgalactiae subsp. equisimilis (S. equisimilis) using physiological tests. Of these strains, 5 strains were agglutinated to Lancefield group A, 17 strains to group C, and 106 strains to group G. Most of these strains were largely isolated from clinical specimens collected from young patients with respiratory infections and middle-aged patients (in their 40s); most of the strains were isolated from blood, atretic pus, or joint fluid. Genetic analysis of the emm gene encoding the M protein revealed that these strains could be classified into 27 types. Also, many emm types were found in strains isolated from normally aseptic clinical specimens. In addition, all strains tested had slo, sagA, and skcg genes, which contributed to their virulence. The susceptibility of the strains to oral penicillin and cephalosporin antibiotics was excellent, with MICs ranging from 0.016 to 0.031mg/mL. In contrast, strains carrying the macrolide resistant elements of the ermA, ermB, and mefA genes and strains showing a high resistance to levofloxacin were also confirmed in this study. These results suggest that beta-hemolytic streptococci, except for S. pyogenes and S. agalactiae, should be reconsidered as a causative pathogen in streptococcal infections.     

Role of a type IV-like secretion system of Streptococcus suis 2 in the development of streptococcal toxic shock syndrome

Streptococcus suis serotype 2 (S. suis 2) has evolved into a highly invasive pathogen that was found to be the cause of 2 large-scale outbreaks of streptococcus toxic shock syndrome (STSS) in China. However, the mechanism of action of this non-group A streptococcal (GAS) S. suis-caused STSS is still unknown. Previously, we identified a unique pathogenicity island (PAI) designated 89K that is specific to the STSS-causing epidemic strains of S. suis 2. In this study, we further report a functional type IV-like secretion system (T4SS-like system) harbored in the 89K PAI that contributes to the development of STSS. Knockout of the 2 key components (VirD4-89K and VirB4-89K) of the T4SS-like system eliminated the lethality of the highly virulent strain and impaired its ability to trigger host immune response in experimental infection of mice. Our findings provide a new insight into the pathogenesis of STSS caused by the highly pathogenic S. suis 2 isolates.     

Prevalence of S315T mutation within the katG gene in isoniazid-resistant clinical Mycobacterium tuberculosis isolates from Dubai and Beirut.

OBJECTIVE: To determine the prevalence of S315T mutation within the katG gene that confers clinically significant resistance to isoniazid in isoniazid-resistant Mycobacterium tuberculosis isolates recovered from tuberculosis patients in Dubai and Beirut. METHOD: A total of 28 and 17 isoniazid-resistant and seven and six susceptible clinical M. tuberculosis isolates from Dubai and Beirut, respectively, were tested. The presence of S315T mutation in the katG gene was detected by amplification of the DNA region around codon 315 by polymerase chain reaction followed by restriction digestion with Msp I to generate restriction fragment length polymorphism. The genotyping of the isolates carrying S315T mutation was carried out by touchdown double-repetitive-element PCR (DRE-PCR). RESULTS: The mutation S315T was detected in 18 (64%) of 28 isoniazid-resistant isolates from Dubai and in six (35%) of 17 resistant strains from Beirut. None of the susceptible strains contained this mutation. The genotyping studies showed that the majority of the isolates carrying the S315T mutation exhibited unique DNA banding patterns. CONCLUSION: The data show a varying prevalence of S315T mutation within the katG gene in M. tuberculosis strains isolated from the two geographical locations, Dubai and Beirut.     

Dynamics of the penA gene in serogroup C meningococcal strains

The transpeptidase encoding region of the penA gene was sequenced in 44 meningococcal strains (41 serogroup C [23 characterized as serotype 2b and 18 as serotype 2a] and 3 serogroup B [B:2b:P1.2,5]). All strains were characterized by multilocus sequence typing and were determined to be susceptible or intermediate resistant to penicillin (Pen(s) or Pen(i), respectively). A high degree of homology was found among the penA alleles identified in the Pen(s) strains. All the Pen(i) C:2b strains, which belonged to 2 different clonal complexes, showed the same penA gene allele. This fact suggests that 1 of the clonal complexes acquired that allele, spreading it to the other by horizontal transfer. The same allele also was found in the B:2b strains studied, indicating that 1 of the Pen(i) C:2b strains underwent a capsular switching event. A different mosaic penA allele was identified in the Pen(i) C:2a strains, which belonged to the ET37 cluster.     

上海地区儿童化脓性链球菌的红霉素耐药基因研究

目的 了解上海地区化脓性链球菌对红霉素的耐药情况及耐药基因谱的特点.方法 2004年11月至2006年6月经复旦大学附属儿科医院传染病门诊诊断为猩红热的患儿,其咽拭子培养分离获得100株化脓性链球菌.应用PCR及序列分析法检测红霉素耐药基因mefA、ermA、ermB在该批菌株中的分布规律及其与红霉素耐药性的关系.结果上海地区化脓性链球菌的红霉素耐药率为98%,克林霉素耐药率为95%,两者耐药性的一致率为97%.100株菌株中含ermB基因的化脓性链球菌94株,占所有菌株的94%,对红霉索耐药率为100%;含mefA基因的化脓性链球菌16株,占所有菌株的16%,对红霉素耐药率为100%;100株菌株中未发现ermA基因.5株菌株未发现ermB基因及mefA基因,其中2株对红霉素敏感,3株对红霉素耐药.mefA基因单独阳性的菌株仅占1%.结论上海地区化脓性链球菌对红霉奈普遍具有较高耐药率,且与克林霉素存在较严重的交叉耐药.ermB基因是决定上海地区化脓性链球菌对红霉素耐药的重要基因.     

Antimicrobial sensitivity and characterization of Streptococcus pyogenes strains isoleated from a scarlatina outbreak

OBJECTIVE: To evaluate the in vitro activities of 13 antimicrobial agents against 47 group A Streptococcus pyogenes (GAS) strains, and to determine the presence of genes encoding streptococcal pyrogenic exotoxin A (SpeA) and the M-protein serotypes. MATERIALS AND METHODS: A cross-sectional study was conducted at Centro de Salud Dr. José Castro Villagrana, during a scarlet fever outbreak occurring between December 1999 and January 2000, among 137 children at Colegio Espíritu de América. Minimum Inhibitory Concentrations (MICs) were obtained by the semiautomated microdilution method. Automated DNA sequencing was used for analysis of sequence variation in genes encoding the M protein, and SpeA. RESULTS: All strains were sensitive to betalactams and clindamycin. Six (12.7%) were resistant to erythromycin. The M2 type was the most frequently isolated GAS (27); almost all (96%) bacteria with the SpeA gene had the gene encoding the M2 protein. CONCLUSIONS: The recent resurgence of GAS infections calls for molecular epidemiology research and studies on the sensitivity to macrolides and beta-lactams.     

Invasive group A streptococcal infections in Sweden in 1994 and 1995: epidemiology and clinical spectrum

A nationwide study of invasive group A streptococcal (GAS) infections in Sweden during 1994-1995 was carried out. All Swedish microbiological laboratories were asked to report isolates of GAS from normally sterile sites. During the study period they were also asked to send their isolates for T typing. Questionnaires were sent to the physicians in charge of each patient. The incidence, serotype, clinical presentation, symptoms and outcome were recorded. Clinical data were obtained for 468 of 556 patients with GAS bacteraemia. The lethality rate was 16%, but was much higher (37%) in the 113 patients who developed streptococcal toxic shock syndrome (STSS). Streptococci of serotype T1 dominated during the study period and were linked to the increase in invasive GAS infections. They also carried an increased risk of causing STSS. Invasive streptococcal disease with STSS most often has an unknown primary focus or is associated with soft tissue infections. Invasive streptococcal disease not associated with STSS most often has a skin infection as portal of entry or else an unknown focus.     

幽门螺杆菌对克拉霉素的耐药性与23S rRNA基因突变相关性分析

[目的]研究本地区幽门螺杆菌（Helicobacter pylori,HP）的克拉霉素耐药与23S rRNA基因位点突变的关系,为临床根除HP治疗提供依据.[方法]入选消化性溃疡患者180例,在胃窦小弯侧距幽门2～3cm范围内取1块胃黏膜组织行常规病理检查,在胃窦小弯侧、十二指肠球部、胃体大弯侧各取1块黏膜行HP培养,对HP阳性分离菌株进行药敏实验.选取其中克拉霉素耐药菌株35例及敏感菌株30例,对23S rRNA基因PCR扩增后进行全基因测序对比分析.[结果] 180例中HP阳性率占76.11％,活检组织培养HP阳性率占73.89％.药敏检查结果克拉霉素耐药率为33.08％.HP23S rRNA测序结果显示存在多位点突变,耐药组及非耐药组中T2182C普遍存在,A2143G、A2142G和A2097G在耐药组中多见,A2097C、A2097T仅在敏感组中发现,差异有统计学意义.[结论]本地区HP对克拉霉素耐药率高,克拉霉素耐药菌株A2143G、A2142G和A2097G位点突变高于敏感组,建议根据药敏试验指导根除HP方案.     

结核分枝杆菌西安分离株北京家族基因型检测及其耐药相关性研究

目的了解西安市结核分枝杆菌临床分离株的耐药情况及其与北京家族基因型(Beijing Family)的相关性,为有效防治结核病提供依据。方法对临床分离结核分枝杆菌采用绝对浓度法进行药物敏感性检测。间隔寡核苷酸分型(Spoli-gotyping)方法进行北京家族基因型鉴定。结果统计学分析采用χ2检验。结果104株结核分枝杆菌对4种一线抗结核药物,异烟肼(INH)、利福平(RFP)、链霉素(SM)和乙胺丁醇(EMB),全部敏感的菌株为71株(68.3%);耐药菌株33株(31.7%),其中,单耐药菌株12株(11.5%),耐多药菌株21株(20.2%)。结核分枝杆菌对4种一线药物INH、RFP、SM和EMB的耐药率分别为24.04%(25/104)、18.69%(19/104)、16.34%(17/104)和2.88%(3/104)。104株结核分枝杆菌中北京家族基因型(BeijingFamily)占全部菌株的83.7%,非北京家族基因型占16.3%。87株北京家族基因型菌株中耐药菌株28株(32.18%),敏感菌株59株(67.82%),而17株非北京家族基因型菌株中耐药菌株5株(29.41%),敏感菌株为12株(70.59%)。经统计学分析其差异无统计学意义(χ2=0.05,P>0.05)。结论西安市分枝杆菌的耐药情况较为严重。结核分枝杆菌北京家族基因型与耐药性之间无明显相关性。     

Sequence variation in group A Streptococcus pili and association of pilus backbone types with lancefield T serotypes

BACKGROUND: We previously reported that group A Streptococcus (GAS) pili are the T antigens described by Rebecca Lancefield. We also showed that these pili, constituted by backbone, ancillary 1, and ancillary 2 proteins, confer protection against GAS challenge in a mouse model. METHODS: We evaluated pilus distribution and conservation by sequencing the subunits of 39 new GAS isolates and used immunoblot analysis and agglutination assays to define the specificity of T sera to pilus subunits. RESULTS: GAS pili are encoded by 9 different islands within which backbone protein, ancillary protein 1, and ancillary protein 2 cluster in 15, 16, and 5 variants, respectively. Immunoblot and agglutination assays revealed that T type is determined by the backbone variant. This observation enabled us to set up a simple polymerase chain reaction assay to define the T type of GAS isolates. CONCLUSIONS: We propose the use of a tee gene sequence typing, analogous to the emm gene typing, as a valuable molecular tool that could substitute for the serological T classification of GAS strains. From our sequence analysis and from recent epidemiological data, we estimate that a vaccine comprising a combination of 12 backbone variants would protect against > 90% of currently circulating strains.     

Structure and distribution of an unusual chimeric genetic element encoding macrolide resistance in phylogenetically diverse clones of group A Streptococcus

The resistance of group A Streptococcus (GAS) to macrolide antibiotics is now a worldwide problem. Preliminary sequencing of the genome of an erythromycin-resistant serotype M6 clone that was responsible for a pharyngitis outbreak in Pittsburgh, Pennsylvania, was conducted to determine the structure of the genetic element containing the mefA gene, which encodes a macrolide efflux protein. The mefA gene is associated with a 58.8-kb chimeric genetic element composed of a transposon inserted into a prophage. This element also encodes a putative extracellular protein with a cell-wall anchoring motif (LPKTG) located at the carboxyterminus. The mefA element was present in phylogenetically diverse GAS strains isolated throughout the United States. Culture supernatants, prepared after mitomycin C treatment, of a strain representing the outbreak clone contained mefA element DNA in a DNAse-resistant form. Together, these data provide new information about the molecular genetic basis of macrolide resistance and dissemination in GAS strains.     

黑龙江省未经治疗的艾滋病患者蛋白酶和反转录酶基因型耐药性检测与分析

目的 对黑龙江省流行的HIV-1毒株的蛋白酶基因及反转录酶基因进行基因型耐药分析,为开展大规模临床抗病毒治疗提供本底数据.方法 采用套式-PCR法扩增黑龙江省内49例HIV-1感染者及AIDS患者外周血单个核细胞中前病毒cDNA的部分蛋白酶和反转录酶基因,分析基因序列,与国际耐药数据库比对,分析耐药变异.结果 49例患者HIV毒株亚型分析为B'亚型.在扩增出蛋白酶基因的47份标本中,未发现对蛋白酶抑制剂的原发突变,但发现大量对蛋白酶抑制剂的次要突变,V771占91.5%、L63P占76.6%、I93L占74.5%、E35D占61.7%、R57K占19.1%、R41K占10.6%、A71V占8.5%、M36I占8.5%、L10I占6.4%、D60E占6.4%、L89M占4.2%和G16E占2.1%.在扩增出反转录酶基因的44份标本中,1份有反转录酶抑制剂的原发突变M184I,占2.3%,均有反转录酶抑制剂的次要突变,I135L/T/R/V占81.8%、V106I占22.7%、V179D/E占11.4%、R211K占9.1%、L214F占4.5%、V189I占4.5%和V108I占2.3%.结论 目前在黑龙江省未接受抗反转录病毒治疗的患者中未发现对蛋白酶抑制剂耐药的原发突变,耐药突变处于低水平,但应及时进行耐药突变检测,防止多重耐药和交叉耐药的出现和流行.     

Antibiotic resistance genes detected by multiplex PCR assays in Staphylococcus epidermidis strains isolated from dialysis fluid and needles in a dialysis service

The rate of the onset of methicillin-resistant Staphylococcus epidermidis infections is increasing in Tunisia. We have isolated 32 S. epidermidis strains from dialysis fluid and needle cultures in dialysis service. The strains were identified by classic methods (colonial morphology, Gram staining, catalase test, coagulase test, and DNase test) as well as by API ID32 Staph. Susceptibilities to 18 antibiotics were tested with the ATB Staph kit. Most of the tested strains were resistant to penicillin. In addition, the presence of multidrug resistant strains that showed resistance to different antibiotics was recorded. We have characterized these strains by multiplex PCR assay to identify intercellular adhesion genes icaA/icaD associated with the adhesiveness of staphylococci in biomaterials, and to identify representative resistant genes: oxacillin resistance, mecA; erythromycin methylase (ermA, ermB, and ermC), and macrolide efflux gene (msrA and mef). The frequency of the carriage of these genes was icaA/icaD (71.9%), mecA (78.1%), ermA (12.5%), ermB (31.3%), ermC (53.1%), msrA (68.8%), and mef (O%). Although the carriage of the genes and the results of susceptibility testing did not match exactly, it could be judged that the PCR identification of antibiotic resistance genes is rapid and supplementary methods for identifying staphylococci or epidemiological study used for the control of nosocomial infection.