In vitro antimicrobial effects of various combinations of penicillin and clindamycin against four strains of Streptococcus pyogenes

Previous studies using mouse models of Streptococcus pyogenes necrotizing fasciitis demonstrated that clindamycin had greater efficacy than penicillin. Frequently both agents are used concurrently in the treatment of severe S. pyogenes infections. This study investigated interactions between penicillin and clindamycin. E-test and broth microdilution assays suggested additivity or indifference, while timed-killing assays demonstrated concentration-dependent variable effects. Timed-kill studies utilizing clinical concentrations suggest that there is no antagonism with the combination of drugs but that the combination does not have a bactericidal advantage over either penicillin or clindamycin alone.

Radiation-induced transformation of SV40-immortalized human thyroid epithelial cells by single exposure to plutonium alpha-particles in vitro

Human thyroid carcinomas have been induced following exposure of SV40-immortalized human thyroid epithelial cells in vitro to single doses (0.14 Gy to 1.57 Gy) of 3.26 MeV alpha-particles from a plutonium 238 source. Tumours were detected between 50 and 160 days following subcutaneous transplantation of the irradiated cells in athymic mice. No tumours were observed following transplantation of unirradiated cells. The relative biological effectiveness (RBE) of the alpha-particles, estimated from cell survival curves, was 4.8 at 50% survival and 3.3 at 5% survival. A first estimate of the RBE at peak tumour induction was 3.8. This system provides a means of studying the mechanisms of tumourigenesis in human thyroid epithelial cells induced by ionizing radiations, including tumours induced by single alpha particles such as from environmental natural radon and polonium and artificial plutonium and americium, and those induced by beta- or Auger-emissions from particular iodine isotopes.

Induction and rejoining of DNA double-strand breaks in Chinese hamster V79-4 cells irradiated with characteristic aluminum K and copper L ultrasoft X rays

Characteristic aluminum K (AlK) (energy of 1.5 keV) and copper L (CuL) (energy of approximately 0.96 keV) ultrasoft X rays have been used to investigate the effectiveness of the numerous low-energy secondary electrons produced by low-linear energy transfer (LET) ionizing radiation. Cellular inactivation and induction and rejoining of DNA double-strand breaks (DSBs) in Chinese hamster V79-4 cells irradiated as monolayers with these ultrasoft X radiations have been studied under aerobic and anaerobic conditions. The mean cell thickness, determined by confocal laser scanning fluorescence microscopy, was used to calculate the mean dose to the nucleus of the irradiated cells. Relative to 60Co gamma rays, the relative biological effectiveness (RBE) for cellular inactivation at 10% survival is 1.7 +/- 0.1 and 2.3 +/- 0.3 for AIK and CuL ultrasoft X rays, respectively. The RBE values for induction of DSBs of 2.5 +/- 0.2 and 3.0 +/- 0.3 for AlK and CuL X rays, respectively, were determined after irradiation at 277 K using the technique of pulsed-field gel electrophoresis. Induction of DSBs is linearly dependent on dose. Oxygen enhancement ratios of 1.9 and 2.1 for cellular inactivation and DSB induction, respectively, were obtained with AIK X rays. These values are less than those for 60Co gamma radiation. The repair kinetics for rejoining of DSBs after a dose of 15 Gy is similar for both X-ray energies and 60Co gamma rays with a first half-life of 18-22 +/- 5 min. From these studies, it is suggested that induction of DSBs by low-LET radiations such as 60Co gamma rays reflects clustered damage produced predominantly by low-energy electron "track ends," which represent about 30% of the total dose.

Screening, prevention, counseling, and treatment for the complications of type II diabetes mellitus. Putting evidence into practice

PURPOSE

To summarise current knowledge of interventions that should improve the care of patients with type II diabetes mellitus. Interventions lie within the realms of preventions, screening, and treatment, all of which are focused on office practice.

METHODS

Review of the literature by a multidisciplinary team involved in the care of patients with diabetes, followed by synthesis of the literature into a clinical care guideline. Literature was identified through consultation with experts and a focused MEDLINE search.

MAIN RESULTS

An algorithm-based guideline for screening and treatment of the complications of diabetes was developed. The emphasis is on prevention of atherosclerotic disease, and prevention, screening, and early treatment of microvascular disease. Implementation of these practices has the potential to significantly improve quality of life and increase life expectancy in patients with type II diabetes mellitus.

Clostridium perfringens enterotoxin lacks superantigenic activity but induces an interleukin-6 response from human peripheral blood mononuclear cells

We investigated the potential superantigenic properties of Clostridium perfringens enterotoxin (CPE) on human peripheral blood mononuclear cells (PBMC). In contrast to the findings of a previous report (P. Bowness, P. A. H. Moss, H. Tranter, J. I. Bell, and A. J. McMichael, J. Exp. Med. 176:893-896, 1992), two different, biologically active preparations of CPE had no mitogenic effects on PBMC. Furthermore, PBMC incubated with various concentrations of CPE did not elicit interleukin-1, interleukin-2, gamma interferon, or tumor necrosis factor alpha or beta, which are cytokines commonly associated with superantigenic stimulation. However, CPE did cause a dose-related release of interleukin-6 from PBMC cultures.

Alpha toxin from Clostridium perfringens induces proinflammatory changes in endothelial cells

Alpha toxin from Clostridium perfringens type A, a phospholipase C, has been implicated in many of the localized and systemic features of gas gangrene. We demonstrated that human endothelial cells synthesize two vasoactive lipids, platelet-activating factor (PAF) and prostacyclin, in response to alpha toxin treatment. The stimulated synthesis of PAF required the enzymatic activity of the toxin and subsequent protein kinase C activation. Alpha toxin-treated endothelial cells accumulated the products of the phospholipase C reaction, diacylglycerol and ceramide, and exhibited a decrease in the enzymatic precursors phosphatidylcholine and sphingomyelin. Furthermore, the temporal accumulation of PAF depended on the concentration of the toxin in the overlying medium and was blocked in the presence of a neutralizing antibody. The cultured endothelial cells also exhibited enhanced neutrophil adhesion in response to alpha toxin which was mediated through the PAF receptor and P-selectin. P-selectin expression by endothelial cells and extravascular neutrophil accumulation were also observed in tissue sections from alpha toxin-injected Sprague-Dawley rats. These endothelial cell-mediated processes are important in maintaining vascular homeostasis and, when activated in a dysregulated manner by C. perfringens alpha toxin, may contribute to localized and systemic manifestations of gas gangrene including enhanced vascular permeability, localized neutrophil accumulation, and myocardial dysfunction.

Clostridial gas gangrene: evidence that alpha and theta toxins differentially modulate the immune response and induce acute tissue necrosis

The rapid extension of necrosis and an absence of polymorphonuclear leukocytes (PMNL) at the site of infection are two hallmarks of Clostridium perfringens gas gangrene. While both alpha and theta toxins profoundly affect PMNL function and viability in vitro, their roles in muscle destruction and impairment of the inflammatory response in vivo have not been investigated. Comparative histopathologic examinations were performed on animals infected with either wild-type C. perfringens, or isogenic, toxin-deficient mutants of C. perfringens. Tissue destruction was modest in animals infected with the alpha toxin-deficient mutant; destruction was more pronounced in tissues infected with the theta toxin-deficient mutant or the wild-type strain. alpha and theta toxins also displayed differing abilities to modulate the inflammatory response. Histopathologic studies in which recombinant toxins were injected together with killed, washed C. perfringens further substantiated these tissue-destructive and differential antiinflammatory effects.

Familial transmission of a serious disease--producing group A streptococcus clone: case reports and review

Invasive group A streptococcus (GAS) infections are emerging diseases; however, person-to-person transmission of invasive GAS producing life-threatening infection has been observed rarely. We report a small intrafamilial cluster of life-threatening GAS infections. A previously healthy 47-year-old father developed necrotizing fasciitis of the neck. Two days later, his 16-year-old daughter developed streptococcal angina, pneumonia, and pleural empyema. Both patients had signs of streptococcal toxic shock syndrome. Pulsed field gel electrophoresis revealed that the M6 strains of GAS isolated from the father and daughter had identical patterns. Cases of person-to-person transmission of invasive GAS infection reported in the literature are also reviewed.

The toxins of group A streptococcus, the flesh eating bacteria

Streptococcus pyogenes causes a wide variety of infections in individuals of all ages in most countries of the world. Because of the frequency with which these infections occur, physicians are quite familiar with the diversity of clinical presentations associated with the Group A streptococcus. Yet in the late 1980's, a severe form of streptococcal infection, the Streptococcal Toxic Shock Syndrome, emerged and has persisted for the last 10 years. This syndrome is associated with invasive soft tissue infections and the early onset of shock and organ failure. The purpose of this paper is to briefly describe the epidemiologic and clinical features of the Streptococcal Toxic Shock Syndromes and to emphasize the role that toxins produced by S. pyogenes play in the pathogenesis of this disease.

Superantigens: their role in infectious diseases

In the last 10 years many of the superantigens of the microbial world have been defined and the mechanisms of cellular interaction between lymphocytes and antigen presenting cells has been elucidated in great detail. The consequences of superantigen stimulation of the immune system, though less well defined, can be considered in three separate stages: T-cell proliferation, apoptosis, and recovery. Understanding these stages may explain why diverse superantigens may cause markedly different clinical processes ranging from acute shock to chronic arthritis and may form the basis for novel treatments of these diverse diseases.

The toxic shock syndromes

Because of the frequency with which Staphylococcus aureus and Streptococcus pyogenes infections occur, physicians are quite familiar with the diversity of their clinical presentations. In the 1970s, however, shock associated with multiorgan failure was described in menstruating female patients as well as in male patients following a variety of surgical procedures, such as rhinoplasty. This previously undescribed presentation of S. aureus infection, termed staphylococcal toxic shock syndrome, was associated with unique strains of S. aureus. In the mid-1980s, the emergence of streptococcal toxic shock syndrome was heralded by several case reports describing patients with group A streptococcal infections associated with shock and organ failure. This article compares the differences in the epidemiologic, clinical, and pathophysiologic features of the toxic shock syndromes.

Ultrasoft 1.5 keV aluminum K X rays are efficient producers of complex chromosome exchange aberrations as revealed by fluorescence in situ hybridization

The electron pairs generated by ultrasoft 1.5 keV aluminum K X-ray photons deposit their energy in tracks of length < 70 nm and provide an ideal tool for analyzing the spatial distribution of breaks and misrepair processes. We have undertaken the analysis of changes in chromosome structure produced by aluminum K X rays in untransformed HF12 human fibroblasts in G1 phase using fluorescence in situ hybridization (FISH). Multicolored chromosome-specific DNA probes for chromosomes 1 and 2 and an alpha-satellite pan-centromeric probe were used to examine in vitro radiation-induced chromosome-type exchange aberrations. After mean doses of 0.37-2.93 Gy the relative frequencies of complex exchanges, derived from three or more breaks in two or more chromosomes, ranged from 15-35%. For the classic break-age-and-rejoining theory to hold, very large interaction distances are needed to account for this high frequency of multibreak interactions, unless many sites pre-exist where several different chromosomes come very close together. Alternatively, damaged DNA may be able to interact with adjacent undamaged DNA, obviating the need for large rejoining distances.

Invasive group A streptococcal disease

The emergence of severe group A streptococcal (GAS) infection since the 1980s has now been reported from most parts of the world. Many of these cases have been associated with deep-seated infection associated with shock and multiple-organ failure and are defined as streptococcal toxic shock syndrome (StrepTSS). Strains of GAS isolated from patients with invasive disease have been predominantly of M types 1 and 3, which produce either pyrogenic exotoxin A or B or both. In this article, the clinical and demographic features of streptococcal bacteremia, myositis, and necrotizing fasciitis are presented and compared with those of StrepTSS. Current concepts about the pathogenesis of invasive streptococcal infection are also discussed, in terms of the interaction between GAS virulence factors and host-defense mechanisms. Finally, the efficacy of clindamycin, the failure of penicillin, and new ideas for future treatment of serious streptococcal infections are outlined.

Genetic and phenotypic diversity among isolates of Streptococcus pyogenes from invasive infections

To determine if recent cases of invasive group A streptococcal disease were caused by strains with a unique characteristic, 117 isolates Streptococcus pyogenes from patients with a variety of diseases, including necrotizing fasciitis and toxic shock syndrome, were analyzed. Significant genomic heterogeneity was observed among selected isolates, as determined using pulsed-field gel electrophoresis. The frequency of the bacteriophage-associated streptococcal erythrogenic toxin genes A and C (speA and speC) among the isolates was 44% (49/112) and 34% (38/112), respectively. Forty-three percent of speA-positive isolates produced streptococcal erythrogenic toxin (SPE) A in vitro. Seventy-six percent (85/112) of isolates produced SPE B in vitro, and in contrast to SPE A, little variation in the concentration of SPE B in broth culture supernatants was detected. The genetic and phenotypic heterogeneity observed among isolates from recent cases of severe infection does not support a clonal basis for the resurgence of invasive streptococcal infections.

Group A streptococcal bacteremia: the role of tumor necrosis factor in shock and organ failure

Severe group A streptococcal infections associated with early onset shock and multiorgan failure define the streptococcal toxic shock syndrome. In the United States, group A streptococcal strains most commonly isolated are M types 1 and 3, which produce pyrogenic exotoxin type A. The role of tumor necrosis factor (TNF)-alpha and the dynamics of cardiovascular and laboratory abnormalities were investigated in a baboon model of group A Streptococcal bacteremia that mimics human Streptococcal toxic shock syndrome. Profound hypotension, leukopenia, metabolic acidosis, renal impairment, thrombocytopenia, and disseminated coagulopathy developed within 3 h after intravenous infusion of M type 3, pyrogenic exotoxin A-producing group A streptococci. Serum TNF-alpha peaked at 3 h and returned to baseline by 10 h. Mortality was 100%. Anti-TNF-alpha monoclonal antibody treatment markedly improved mean arterial blood pressure, tissue perfusion, and survival, suggesting that TNF-alpha plays an important role in the induction of shock and organ failure in group A streptococcal bacteremia.

Spread of serious disease-producing M3 clones of group A streptococcus among family members and health care workers

Streptococcus pyogenes causes a variety of diseases ranging from mild pharyngitis to severe toxic shock syndrome (TSS) and acute rheumatic fever. Since 1987 there has been a resurgence of severe group A streptococcus infections including TSS, necrotizing fasciitis, and myositis. Using molecular and serotyping procedures, we recently studied two clusters of group A streptococcus disease that occurred within separate family units. The first cluster involved two family members (one with TSS and one with necrotizing fasciitis) and three health care workers who attended one of the index patients. The second cluster included a mother (with necrotizing fasciitis of the hand) and her three children. Group A streptococci isolated from individuals within both cluster groups were serotype M3;T3/13/B3264, and pulsed field gel electrophoresis revealed that all isolates except one had identical fingerprints of Sma I-digested chromosomal DNA. The findings demonstrate the potential for spread of serious group A streptococcus disease among individuals and the need for barrier protection when health care workers are exposed to secretions from infected individuals.

Progressive myoclonus epilepsy with focal brainstem degeneration and paternal inheritance. An autopsy report of 4 cases from 2 pedigrees

Four autopsied cases of myoclonus, ataxia, and epilepsy from 2 separate pedigrees are described. An identical pattern of focal brainstem lesions was found in all the cases with selective and symmetrical degeneration of the dentate and second order somatosensory nuclei. The combined clinical and pathological features did not appear to match any familial disorder previously described as causing progressive myoclonus epilepsy. Myoclonus epilepsy with ragged red fibres was excluded on the grounds of paternal inheritance and negative muscle biopsy findings, but the more acute lesions seen in 1 case are reminiscent of those found in Leigh's syndrome, and suggest that some other form of inherited defect of oxidative metabolism may be involved.