Structure of the streptococcal endopeptidase IdeS, a cysteine proteinase with strict specificity for IgG

Pathogenic bacteria have developed complex and diverse virulence mechanisms that weaken or disable the host immune defense system. IdeS (IgG-degrading enzyme of Streptococcus pyogenes) is a secreted cysteine endopeptidase from the human pathogen S. pyogenes with an extraordinarily high degree of substrate specificity, catalyzing a single proteolytic cleavage at the lower hinge of human IgG. This proteolytic degradation promotes inhibition of opsonophagocytosis and interferes with the killing of group A Streptococcus. We have determined the crystal structure of the catalytically inactive mutant IdeS-C94S by x-ray crystallography at 1.9-A resolution. Despite negligible sequence homology to known proteinases, the core of the structure resembles the canonical papain fold although with major insertions and a distinct substrate-binding site. Therefore IdeS belongs to a unique family within the CA clan of cysteine proteinases. Based on analogy with inhibitor complexes of papain-like proteinases, we propose a model for substrate binding by IdeS.     

Inhibitor of streptokinase gene expression improves survival after group A streptococcus infection in mice

The widespread occurrence of antibiotic resistance among human pathogens is a major public health problem. Conventional antibiotics typically target bacterial killing or growth inhibition, resulting in strong selection for the development of antibiotic resistance. Alternative therapeutic approaches targeting microbial pathogenicity without inhibiting growth might minimize selection for resistant organisms. Compounds inhibiting gene expression of streptokinase (SK), a critical group A streptococcal (GAS) virulence factor, were identified through a high-throughput, growth-based screen on a library of 55,000 small molecules. The lead compound [Center for Chemical Genomics 2979 (CCG-2979)] and an analog (CCG-102487) were confirmed to also inhibit the production of active SK protein. Microarray analysis of GAS grown in the presence of CCG-102487 showed down-regulation of a number of important virulence factors in addition to SK, suggesting disruption of a general virulence gene regulatory network. CCG-2979 and CCG-102487 both enhanced granulocyte phagocytosis and killing of GAS in an in vitro assay, and CCG-2979 also protected mice from GAS-induced mortality in vivo. These data suggest that the class of compounds represented by CCG-2979 may be of therapeutic value for the treatment of GAS and potentially other gram-positive infections in humans.     

Incomplete Kawasaki disease associated with complicated Streptococcus pyogenes pneumonia: A case report

A three-year-old boy presented with community-acquired pneumonia complicated by empyema. Streptococcus pyogenes (group A streptococcus) was identified on culture of the pleural fluid. The patient improved with antibiotic therapy and drainage of the empyema.During his convalescence, the patient developed persistent fever, lethargy and anorexia. His inflammatory markers were elevated, and repeat cultures were negative. Although the patient had none of the classical mucocutaneous features of Kawasaki disease, an echocardiogram was performed, which revealed coronary artery dilation.The patient was diagnosed with incomplete Kawasaki disease and treated with intravenous immunoglobulin and high-dose acetylsalicylic acid. The fever subsided within 48 h.To the authors’ knowledge, the present report is the first report of Kawasaki disease associated with complicated S pyogenes pneumonia. It emphasizes the importance of considering incomplete Kawasaki disease among children with persistent fever, the role of echocardiography in diagnosis, and the potential link between Kawasaki disease and superantigen-producing organisms such as S pyogenes.     

Primary peritonitis due to group A Streptococcus in a previously healthy pediatric patient

Primary peritonitis remains a rare disease in otherwise healthy children, with group A Streptococcus (GAS) being a particularly unusual cause. A case involving a 14-year-old girl, who presented with an ‘acute abdomen’ and was taken to the operating room for urgent laparoscopy, is reported. Abdominal and pelvic structures were only minimally inflamed, as was the appendix. Peritoneal fluid and blood cultures both grew pure cultures of GAS. The patient’s course was complicated by streptococcal toxic shock syndrome. She fortunately made a full recovery. The present report highlights the diagnostic and treatment dilemmas associated with GAS primary peritonitis.     

Acute phlegmonous gastritis complicated by delayed perforation

Here,we report on a case of acute phlegmonous gastritis(PG)complicated by delayed perforation.A51-year-old woman presented with severe abdominal pain and septic shock symptoms.A computed tomography scan showed diffuse thickening of the gastric wall and distention with peritoneal fluid.Although we did not find definite evidence of free air on the computed tomography(CT)scan,the patient’s clinical condition suggested diffuse peritonitis requiring surgical intervention.Exploratory laparotomy revealed a thickened gastric wall with suppurative intraperitoneal fluid in which Streptococcus pyogenes grew.There was no evidence of gastric or duodenal perforation.No further operation was performed at that time.The patient was conservatively treated with antibiotics and proton pump inhibitor,and her condition improved.However,she experienced abdominal and flank pain again on postoperative day 10.CT and esophagogastroduodenoscopy showed a large gastric ulcer with perforation.Unfortunately,although the CT showed further improvement in the thickening of the stomach and the mucosal defect,the patient’s condition did not recover until a week later,and an esophagogastroduodenoscopy taken on postoperative day 30 showed suspected gastric submucosal dissection.We performed total gastrectomy as a second operation,and the patient recovered without major complications.A pathological examination revealed a multifocal ulceration and necrosis from the mucosa to the serosa with perforation.     

Extracellular deoxyribonuclease made by group A Streptococcus assists pathogenesis by enhancing evasion of the innate immune response

Many pathogenic bacteria produce extracellular DNase, but the benefit of this enzymatic activity is not understood. For example, all strains of the human bacterial pathogen group A Streptococcus (GAS) produce at least one extracellular DNase, and most strains make several distinct enzymes. Despite six decades of study, it is not known whether production of DNase by GAS enhances virulence. To test the hypothesis that extracellular DNase is required for normal progression of GAS infection, we generated seven isogenic mutant strains in which the three chromosomal- and prophage-encoded DNases made by a contemporary serotype M1 GAS strain were inactivated. Compared to the wild-type parental strain, the isogenic triple-mutant strain was significantly less virulent in two mouse models of invasive infection. The triple-mutant strain was cleared from the skin injection site significantly faster than the wild-type strain. Preferential clearance of the mutant strain was related to the differential extracellular killing of the mutant and wild-type strains, possibly through degradation of neutrophil extracellular traps, innate immune structures composed of chromatin and granule proteins. The triple-mutant strain was also significantly compromised in its ability to cause experimental pharyngeal disease in cynomolgus macaques. Comparative analysis of the seven DNase mutant strains strongly suggested that the prophage-encoded SdaD2 enzyme is the major DNase that contributes to virulence in this clone. We conclude that extracellular DNase activity made by GAS contributes to disease progression, thereby resolving a long-standing question in bacterial pathogenesis research.     

IgG glycan hydrolysis by a bacterial enzyme as a therapy against autoimmune conditions

EndoS from Streptococcus pyogenes efficiently hydrolyzes the functionally important and conserved N-linked glycan of IgG in human blood. Repeated i.v. administration of EndoS in rabbits completely hydrolyzes the glycans of the whole IgG pool, despite the generation of anti-EndoS antibodies. EndoS administration had no apparent effects on the health of the animals. EndoS hydrolysis of the IgG glycan has profound effects on IgG effector functions, such as complement activation and Fc receptor binding, suggesting that the enzyme could be used as an immunomodulatory therapeutic agent against IgG-mediated diseases. We demonstrate here that EndoS indeed has a protective effect in a mouse model of lethal IgG-driven immune (or idiopathic) thrombocytopenic purpura. EndoS pretreatment of pathogenic antibodies inhibits the development of disease, and the enzyme also rescues mice from already established disease when severe thrombocytopenia and s.c. bleeding have developed. These results identify EndoS as a potential therapeutic agent against diseases where pathogenic IgG antibodies are important and further emphasize antibody glycans as possible targets in future therapies against antibody-mediated autoimmune conditions.     

Induction of group A Streptococcus virulence by a human antimicrobial peptide

Group A streptococci (Streptococcus pyogenes or GAS) freshly isolated from individuals with streptococcal sore throat or invasive ("flesh-eating") infection often grow as mucoid colonies on primary culture but lose this colony appearance after laboratory passage. The mucoid phenotype is due to abundant production of the hyaluronic acid capsular polysaccharide, a key virulence determinant associated with severe GAS infections. These observations suggest that signal(s) from the human host trigger increased production of capsule and perhaps other virulence factors during infection. Here we show that subinhibitory concentrations of the human antimicrobial cathelicidin peptide LL-37 stimulate expression of the GAS capsule synthesis operon (hasABC). Up-regulation is mediated by the CsrRS 2-component regulatory system: it requires a functional CsrS sensor protein and can be antagonized by increased extracellular Mg(2+), the other identified environmental signal for CsrS. Up-regulation was also evident for other CsrRS-regulated virulence genes, including the IL-8 protease PrtS/ScpC and the integrin-like/IgG protease Mac/IdeS, findings that suggest a coordinated GAS virulence response elicited by this antimicrobial immune effector peptide. LL-37 signaling through CsrRS led to a marked increase in GAS resistance to opsonophagocytic killing by human leukocytes, an in vitro measure of enhanced GAS virulence, consistent with increased expression of the antiphagocytic capsular polysaccharide and Mac/IdeS. We propose that the human cathelicidin LL-37 has the paradoxical effect of stimulating CsrRS-regulated virulence gene expression, thereby enhancing GAS pathogenicity during infection. The ability of GAS to sense and respond to LL-37 may explain, at least in part, the unique susceptibility of the human species to streptococcal infection.     

Generation of Th17 cells in response to intranasal infection requires TGF-β1 from dendritic cells and IL-6 from CD301b+ dendritic cells

Intranasal (i.n.) infections preferentially generate Th17 cells. We explored the basis for this anatomic preference by tracking polyclonal CD4⁺ T cells specific for an MHC class II-bound peptide from the mucosal pathogen Streptococcus pyogenes. S. pyogenes MHC class II-bound peptide-specific CD4⁺ T cells were first activated in the cervical lymph nodes following i.n. inoculation and then differentiated into Th17 cells. S. pyogenes-induced Th17 formation depended on TGF-β1 from dendritic cells and IL-6 from a CD301b⁺ dendritic cell subset located in the cervical lymph nodes but not the spleen. Thus, the tendency of i.n. infection to induce Th17 cells is related to cytokine production by specialized dendritic cells that drain this site.Th17 cells are a subset of CD4⁺ helper T cells that orchestrate protective immunity to extracellular bacterial and fungal pathogens, predominantly at epithelial surfaces (1). T-cell antigen receptor (TCR) recognition of an MHC class II-bound peptide (p:MHCII) on an antigen-presenting cell causes Th17 cells to secrete the signature cytokine IL-17A, which acts primarily by increasing chemokine production in epithelial tissues to enable the recruitment, activation, and migration of neutrophils and monocytes (1).In vitro studies have shown that naive CD4⁺ T cells differentiate into Th17 cells when stimulated by p:MHCII ligands in the presence of transforming growth factor-β1 (TGF-β1) and IL-6 (2-4). Similarly, TGF-β1 is required for Th17 differentiation during the induction of experimental autoimmune encephalomyelitis (EAE) (5). Th17 cells are also generated during intranasal (i.n.) infection by Streptococcus pyogenes, and TGF-β1 receptor signaling and IL-6 are involved (6, 7). However, Th17 cell formation in the small intestine does not depend on TGF-β1 (8) and requires IL-1β but not IL-6 (9). Additionally, Kuchroo and colleagues reported that although Th17 differentiation was normally dependent on IL-6, it could occur without it through an IL-21–dependent pathway if regulatory T cells were absent (10).Infection via the i.n. route may induce Th17 cells because nasal-associated lymphoid tissue (NALT) contains specialized antigen-presenting cells that preferentially produce IL-1β or IL-6 and TGF-β1. Here, we tested this idea by studying the primary immune response to i.n. infection with S. pyogenes bacteria (11). We found that S. pyogenes p:MHCII-specific Th17 cell formation depended on TGF-β1 from dendritic cells and IL-6 from a CD301b⁺ dendritic cell subset located in the cervical lymph nodes (CLNs) but not the spleen.     

Molecular identification of potential pathogens in water and air of a hospital therapy pool

Indoor warm-water therapy pool workers in a Midwestern regional hospital were diagnosed with non-tuberculosis pulmonary hypersensitive pneumonitis and Mycobacterium avium infections. In response, we conducted a multiseason survey of microorganisms present in this therapy pool water, in biofilms associated with the pool containment walls, and in air immediately above the pool. The survey used culture, microscopy, and culture-independent molecular phylogenetic analyses. Although outfitted with a state-of-the-art UV-peroxide disinfection system, the numbers of bacteria in the therapy pool water were relatively high compared with the potable water used to fill the pool. Regardless of the source, direct microscopic counts of microbes were routinely approximately 1,000 times greater than conventional plate counts. Analysis of clone libraries of small subunit rRNA genes from environmental DNA provided phylogenetic diversity estimates of the microorganisms collected in and above the pool. A survey of >1,300 rRNA genes yielded a total of 628 unique sequences, the most common of which was nearly identical to that of M. avium strains. The high proportion of clones with different Mycobacterium spp. rRNA genes suggested that such organisms comprised a significant fraction of microbes in the pool water (to >30%) and preferentially partition into aerosols (to >80%) relative to other waterborne bacteria present. The results of the study strongly validate aerosol partitioning as a mechanism for disease transfer in these environments. The results also show that culture protocols currently used by public health facilities and agencies are seriously inadequate for the detection and enumeration of potential pathogens.     

Future perspectives,applications and challenges of genomic epidemiology studies for food-borne pathogens: A case study of Enterohemorrhagic Escherichia coli (EHEC) of the O157:H7 serotype

The shiga-toxin (Stx)-producing human pathogen Escherichia coli serotype O157:H7 is a highly pathogenic subgroup of Stx-producing E. coli (STEC) with food-borne etiology and bovine reservoir. Each year in the U. S., approximately 100,000 patients are infected with enterohemorrhagic E. coli (EHEC) of the O157:H7 serotype. This food-borne pathogen is a global public health threat responsible for widespread outbreaks of human disease. Since its initial discovery in 1982, O157:H7 has rapidly become the dominant EHEC serotype in North America. Hospitalization rates among patients as high as 50% have been reported for severe outbreaks of human disease. Symptoms of disease can rapidly deteriorate and progress to life-threatening complications such as Hemolytic Uremic Syndrome (HUS), the leading cause of kidney failure in children, or Hemorrhagic Colitis. In depth understanding of the genomic diversity that exists among currently circulating EHEC populations has broad applications for improved molecular-guided biosurveillance, outbreak preparedness, diagnostic risk assessment, and development of alternative toxin-suppressing therapeutics.     

An unusual case of Streptococcus anginosus group pyomyositis diagnosed using direct 16S ribosomal DNA sequencing

Bacteria belonging to the Streptococcus anginosus group (Streptococcus intermedius, Streptococcus constellatus and Streptococcus anginosus) are capable of causing serious pyogenic infections, with a tendency for abscess formation. The present article reports a case of S anginosus group pyomyositis in a 47-year-old man. The pathogen was recovered from one of two blood cultures obtained from the patient, but speciation was initially not performed because the organism was considered to be a contaminant (viridans streptococci group). The diagnosis was ultimately confirmed using 16S ribosomal DNA sequencing of purulent fluid obtained from a muscle abscess aspirate. The present case serves to emphasize that finding even a single positive blood culture of an organism belonging to the S anginosus group should prompt careful evaluation of the patient for a pyogenic focus of infection. It also highlights the potential utility of 16S ribosomal DNA amplification and sequencing in direct pathogen detection from aspirated fluid in cases of pyomyositis in which antimicrobial therapy was initiated before specimen collection.     

Pseudomonas syringae manipulates systemic plant defenses against pathogens and herbivores

Many pathogens are virulent because they specifically interfere with host defense responses and therefore can proliferate. Here, we report that virulent strains of the bacterial phytopathogen Pseudomonas syringae induce systemic susceptibility to secondary P. syringae infection in the host plant Arabidopsis thaliana. This systemic induced susceptibility (SIS) is in direct contrast to the well studied avirulence/R gene-dependent resistance response known as the hypersensitive response that elicits systemic acquired resistance. We show that P. syringae-elicited SIS is caused by the production of coronatine (COR), a pathogen-derived functional and structural mimic of the phytohormone jasmonic acid (JA). These data suggest that SIS may be a consequence of the previously described mutually antagonistic interaction between the salicylic acid and JA signaling pathways. Virulent P. syringae also has the potential to induce net systemic susceptibility to herbivory by an insect (Trichoplusia ni, cabbage looper), but this susceptibility is not caused by COR. Rather, consistent with its role as a JA mimic, COR induces systemic resistance to T. ni. These data highlight the complexity of defense signaling interactions among plants, pathogens, and herbivores.     

Screening for and surveillance of gastric cancer

Although the prevalence of gastric cancer (GC) progressively decreased during the last decades, due to improved dietary habit, introduction of food refrigeration and recovered socio-economic level, it still accounts for 10% of the total cancer-related deaths. The best strategy to reduce the mortality for GC is to schedule appropriate screening and surveillance programs, that rises many relevant concerns taking into account its worldwide variability, natural history, diagnostic tools, therapeutic strategies, and cost-effectiveness. Intestinal-type, the most frequent GC histotype, develops through a multistep process triggered by Helicobacter pylori (H. pylori) and progressing from gastritis to atrophy, intestinal metaplasia (IM), and dysplasia. However, the majority of patients infected with H. pylori and carrying premalignant lesions do not develop GC. Therefore, it remains unclear who should be screened, when the screening should be started and how the screening should be performed. It seems reasonable that screening programs should target the general population in eastern countries, at high prevalence of GC and the high-risk subjects in western countries, at low prevalence of GC. As far as concern surveillance, currently, we are lacking of standardized international recommendations and many features have to be defined regarding the optimal diagnostic approach, the patients at higher risk, the best timing and the cost-effectiveness. Anyway, patients with corpus atrophic gastritis, extensive incomplete IM and dysplasia should enter a surveillance program. At present, screening and surveillance programs need further studies to draw worldwide reliable recommendations and evaluate the impact on mortality for GC.     

The pathogen Batrachochytrium dendrobatidis disturbs the frog skin microbiome during a natural epidemic and experimental infection

Symbiotic microbial communities may interact with infectious pathogens sharing a common host. The microbiome may limit pathogen infection or, conversely, an invading pathogen can disturb the microbiome. Documentation of such relationships during naturally occurring disease outbreaks is rare, and identifying causal links from field observations is difficult. This study documented the effects of an amphibian skin pathogen of global conservation concern [the chytrid fungus Batrachochytrium dendrobatidis (Bd)] on the skin-associated bacterial microbiome of the endangered frog, Rana sierrae, using a combination of population surveys and laboratory experiments. We examined covariation of pathogen infection and bacterial microbiome composition in wild frogs, demonstrating a strong and consistent correlation between Bd infection load and bacterial community composition in multiple R. sierrae populations. Despite the correlation between Bd infection load and bacterial community composition, we observed 100% mortality of postmetamorphic frogs during a Bd epizootic, suggesting that the relationship between Bd and bacterial communities was not linked to variation in resistance to mortal disease and that Bd infection altered bacterial communities. In a controlled experiment, Bd infection significantly altered the R. sierrae microbiome, demonstrating a causal relationship. The response of microbial communities to Bd infection was remarkably consistent: Several bacterial taxa showed the same response to Bd infection across multiple field populations and the laboratory experiment, indicating a somewhat predictable interaction between Bd and the microbiome. The laboratory experiment demonstrates that Bd infection causes changes to amphibian skin bacterial communities, whereas the laboratory and field results together strongly support Bd disturbance as a driver of bacterial community change during natural disease dynamics.Symbiotic interactions between microbes and multicellular organisms are ubiquitous. In recent years, research to understand the complex microbial communities living in or on multicellular organisms (termed the microbiome) has sparked fundamental changes in our understanding of the biology of metazoans (1–5). The microbiome can affect host health directly by influencing metabolism (6), development (7), inflammation (8), or behavior (9), but it may also influence host health indirectly through interactions with infectious pathogens. The microbiome may interact with pathogens through competition for resources, release of antimicrobial compounds, contact-dependent antagonism, or modulation of the host immune response (10), and an “imbalanced” microbiome may leave the host more susceptible to pathogen infection (11, 12). At the same time, an invading pathogen may disrupt the microbiome (10, 13–15). Thus, the microbiome may play a role in disease resistance, or may itself be disturbed or altered by invading pathogens. Although a wealth of recent research has described associations between microbiome composition and a variety of syndromes in both humans and animals (16–25), documentation of microbiome responses to natural epidemics of known infectious pathogens is rare.Chytridiomycosis is an emerging infectious disease of amphibians caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd). Bd is an aquatic fungus that infects the skin of amphibians and disrupts osmoregulation, a critical function of amphibian skin (26). Chytridiomycosis can be fatal, and the severity of disease symptoms has been linked to Bd load, which is a measure of the density of Bd cells infecting the host (27, 28). Bd has a broad host range spanning hundreds of amphibian species, and has been implicated in population extinctions and species declines worldwide (29–34). Efforts to understand and mitigate the effects of Bd have led to research examining the potential for symbiotic bacteria to increase resistance to infection by the pathogen (35, 36). Bacterial species isolated from the skin of amphibians have been shown to inhibit the growth of Bd and other fungal pathogens in culture (37–39), possibly by producing antifungal metabolites (40, 41). In a controlled laboratory experiment, inundation of Rana muscosa with the bacterium Janthinobacterium lividium protected frogs from subsequent Bd infection (42). These and other studies highlight the possible role of bacteria in resistance to chytridiomycosis, but critical questions remain. First, most research has focused on the ability of cultured bacteria to prevent Bd infection, whereas very little is known about whether Bd infection alters the diverse skin microbiome. Examining this latter concept is critical both to a basic understanding of how the microbiome interacts with pathogens and to conservation efforts because Bd-induced perturbations of the microbiome could undermine attempts to mitigate effects of Bd infection through augmentation with particular bacteria. A second knowledge gap is the paucity of comprehensive culture-independent assessments of the amphibian microbiome, which are important because the vast majority of environmental and symbiotic microbes are not readily cultured, and culture-based methods can lead to severe underestimates of diversity and biased assessment of community composition (43). Few studies have applied next-generation sequencing methods to characterize the microbial communities on amphibian skin (44–47), and, to our knowledge, none have done so in the context of Bd infection. A final challenge to understanding interactions between Bd and bacteria stems from the difficulties of drawing direct connections between laboratory and field studies. Laboratory studies are essential for definitive identification of cause and effect. However, complex natural microbiomes can be impossible to recreate in the laboratory, and field studies are needed to show whether processes identified in the laboratory are relevant in nature.We present paired laboratory and field studies using high-throughput 16S amplicon pyrosequencing both to document associations between Bd infection and the amphibian skin bacterial microbiome in nature and to deduce causal relationships in an experiment. Our work centers on the Sierra Nevada yellow-legged frog, Rana sierrae, which is severely threatened by, and has already suffered drastic declines due to, Bd (28, 48). We surveyed frogs from four distinct R. sierrae populations to test if differences in skin bacterial communities are associated with the intensity of pathogen infection. We then conducted a laboratory experiment to establish causal relationships underlying Bd-bacterial community associations. The data establish a strong effect of Bd infection on the composition of the amphibian skin bacterial microbiome that is consistent between the laboratory experiment and naturally occurring Bd dynamics in wild frog populations.     

Epidemiología y características clínicas de los episodios de bacteriemia por Streptococcus pyogenes en Cartagena (Murcia)

Introduction

A gradual increase in severe cases due to Streptococcus pyogenes or Streptococcus beta-hemolytic group A (SGA), has been detected in the last few decades.

Methods

Retrospective study of bacteremia due to S. pyogenes detected between January 2009 and January 2013 in Cartagena. The annual incidence for severe bacteremia has been estimated.

Results

Thirteen cases of SGA bacteremia were recorded. The incidence increased from 0.37 in 2009 to 2.5 cases/100,000 inhabitants in 2012. The predominant focus was skin and soft tissue infections (53%). Early mortality was 20%.

Conclusion

Severe streptococcal disease is rare, but affects individuals with good functional status, and is associated with a high mortality.     

2002～2003年中国社区呼吸道感染常见病原菌的耐药性监测

目的　调查 2 0 0 2～ 2 0 0 3年中国社区呼吸道感染常见病原菌的耐药性。方法　收集2 0 0 2年 4月～ 2 0 0 3年 4月全国 5个地区 5家医院社区呼吸道感染患者中分离的 779株肺炎链球菌、流感嗜血杆菌、卡它莫拉菌、A群 β溶血链球菌及苯唑西林敏感的金黄色葡萄球菌 (MSSA) ;同时收集北京市两家幼儿园儿童鼻咽携带的 185株肺炎链球菌、流感嗜血杆菌及卡它莫拉菌。琼脂稀释法测定头孢丙烯等 10种抗生素的最低抑菌浓度 (MICs)。结果　全国 5个地区 ,青霉素中介的肺炎链球菌(PISP)为 2 3 9% ,青霉素耐药 (PRSP)为 2 2 7%。PISP发生率从高至低依次为杭州 (4 4 1% )、武汉(2 6 2 % )、沈阳 (2 1 5 % )、上海 (2 0 8% )、北京 (18 5 % )、北京幼儿园 (12 7% ) ;而PRSP的排序则为北京幼儿园 (34 9% )、上海 (31 9% )、武汉 (2 7 9% )、杭州 (2 2 1% )、沈阳 (13 8% )、北京 (8 6 % )。肺炎链球菌对左氧氟沙星的敏感率为 96 3%。 9 5 %的流感嗜血杆菌和 87 4 %的卡它莫拉菌产生 β内酰胺酶 ,这两种菌对阿莫西林 /克拉维酸、头孢克洛、头孢丙烯、头孢呋辛、头孢曲松、阿奇霉素、左氧氟沙星的敏感率在 96 4 %～ 10 0 %之间。肺炎链球菌、A群 β溶血链球菌、MSSA对阿奇霉素耐药率高于 6 0 %。头孢丙烯对PISP