The role of myeloid cells in prevention and control of group A streptococcal infections

Group A Streptococcus(GAS;Streptococcus pyogenes)is one of the most versatile bacteria among human pathogens.Non-invasive GAS infections can cause common diseases,such as pharyngitis and impetigo.Severe invasive GAS infections can lead to rapid progressive and life-threatening manifestations,including necrotizing fasciitis and streptococcal toxic shock syndrome with high mortality rates ranging from 30%to 70%.Therefore,GAS is also known as"killer microbes"or"flesh-eating bacteria".During severe invasive GAS infections,anti-bacterial immunity is impeded by attenuation of the cellular components of innate immune responses.However,this loss of protection is compensated for by interferon-γ-producing immature myeloid cells,which are recruited upon severe invasive GAS infections in mouse models.In this review,we discuss and summarize the current knowledge on the role of interferon-γ-producing myeloid cells and other myeloid cells in the prevention and control of severe invasive GAS infections.

Group A streptococcal antigen exposed rat model to investigate neurobehavioral and cardiac complications associated with post-streptococcal autoimmune sequelae

Background:The neuropsychiatric disorders due to post-streptococcal autoimmune complications such as Sydenham's chorea(SC)are associated with acute rheumatic fever and rheumatic heart disease(ARF/RHD).An animal model that exhibits char-acteristics of both cardiac and neurobehavioral defects in ARF/RHD would be an important adjunct for future studies.Since age,gender,strain differences,and geno-types impact on the development of autoimmunity,we investigated the behavior of male and female Wistar and Lewis rat strains in two age cohorts(6 weeks and 12 weeks)under normal husbandry conditions and following exposure to group A streptococcus(GAS).Methods:Standard behavioral assessments were performed to determine the impair-ments in fine motor control(food manipulation test),gait and balance(beam walk-ing test),and obsessive-compulsive behavior(grooming and marble burying tests).Furthermore,electrocardiography,histology,and behavioral assessments were per-formed on male and female Lewis rats injected with GAS antigens.Results:For control Lewis rats there were no significant age and gender dependent differences in marble burying,food manipulation,beam walking and grooming be-haviors.In contrast significant age-dependent differences were observed in Wistar rats in all the behavioral tests except for food manipulation.Therefore,Lewis rats were selected for further experiments to determine the effect of GAS.After ex-posure to GAS,Lewis rats demonstrated neurobehavioral abnormalities and cardiac pathology akin to SC and ARF/RHD,respectively.Conclusion:We have characterised a new model that provides longitudinal stability of age-dependent behavior,to simultaneously investigate both neurobehavioral and cardiac abnormalities associated with post-streptococcal complications.

Invasive group B streptococcal infection in a patient with post splenectomy for hypersplenism secondary to liver cirrhosis and portal hypertension

BACKGROUND:Splenectomy in patients with liver cirrhosis(LC)is expected to become more common owing to its efficacy on portal hemodynamics.In this report we describe an alarming case of group B streptococcus(GBS)infection after splenectomy in a patient with LC.METHODS:A 72-year-old woman with a history of LC was admitted to our emergency department because of respiratory failure.The patient had received left lateral segmentectomy of the liver and splenectomy three months before admission.Pulmonary examination revealed significant wheezing during inspiration and expiration,but no crackles and stridor.Chest radiography and CT showed no infiltrates.A presumptive diagnosis of bronchial asthma caused by upper respiratory infection was made.Four days after admission,GBS infection was confirmed by blood culture and penicillin G was administered.Antibiotics were given intravenously for a total of 12 days.RESULTS:The patient was discharged on the 12th day after admission.CONCLUSIONS:Although efficacy of splenectomy in patients with LC has been reported,immune status should be evaluated for a longer period.Patients who have undergone splenectomy are highly susceptible to bacteria;moreover,LC itself is an independent risk factor for mortality in patients with sepsis.Since prophylaxis against GBS has not been established,immediate action should be taken.Emergency physicians should be aware of invasive GBS infection in the context of the critical risk factors related to splenectomy and LC,particularly the expected increase of splenectomy performed in LC patients.

Epidemiological and pathogenic study on the outbreak of toxic shock syndrome and meningocephalitis caused by swine streptococcus

Objective: To reveal the relationship between the biological characteristics of pathogen and the pig to human spread of the epidemic and infectious disease in 1998 in East China. Methods: Epidemiological survey, pathological examination of pigs and patients, and pathogen isolation were performed. Results: The disease had a character of quick onset, serious symptoms, short course and high mortality. The clinical manifestations and pathological changes of the disease were high fever, sometimes with nausea, vomiting and diarrhea, then might develop to myositis, fascitis, DIC, multiple organ failure, shock and usually died in 2 3 d. Among 25 patients, 16 manifested clinically as streptococcal toxic shock syndromes and 9 streptococcal meningiocephalitis syndrome. The mortality was 81 25% and 11 11% respectively. Pathogenic bacteria isolated from diseased pigs and patients were found to have some common characteristics in morphology, staining and biological characters. Conclusion: The pathogen isolated from the blood of patients and pigs were identified as streptococci.

Prevention of Perinatal Group B Streptococcus Infections

Group B streptococcus(GBS)is a leading cause of neonatal infection.Maternal vaginal-rectal colonization with GBS during the intrapartum period is a prerequisite for GBS early-onset disease(EOD).The obstetric measures for effective prevention of GBS EOD include universal prenatal screening by vaginal-rectal culture,correct specimen collection and processing,appropriate implementation of intrapartum antibiotic prophylaxis,and coordination with pediatric care providers.It is now recommended to universal screen GBS between 36^(0/7)and 37^(6/7)weeks of gestation and to identify groups of women who are eligible for intravenous intrapartum antibiotic prophylaxis as a means of preventing GBS EOD.

Rheumatic fever reappraised

Rheumatic fever is a complication following an episode of group A streptococcal pharyngitis. It is an acute immunologically mediated, multisystem inflammatory disorder. Acute rheumatic heart disease during the active phase of rheumatic fever sometimes progresses to chronic rheumatic heart disease. Despite its declining importance in industrialised countries rheumatic fever remains the leading cause of death from heart disease in children and young adults in less developed regions. Fifteen to twenty million new cases emerge every year in developing countries.~1