Reduced EDHF responses and connexin activity in mesenteric arteries from the insulin-resistant obese Zucker rat

AIMS/HYPOTHESIS

The objective of this study was to examine the effect of insulin resistance on endothelium-derived hyperpolarising factor (EDHF) and small mesenteric artery endothelial function using 25-week-old insulin-resistant obese Zucker rats (OZRs) and lean littermate control rats (LZRs). The involvement of gap junctions and their connexin subunits in the EDHF relaxation response was also assessed.

METHODS

Mesenteric arteries were evaluated using the following assays: (1) endothelial function by pressure myography, with internal diameter recorded using video microscopy; (2) connexin protein levels by western blotting; and (3) Cx mRNA expression by real-time PCR.

RESULTS

Relaxations in response to acetylcholine were significantly smaller in mesenteric arteries from the OZRs than the LZRs, whereas there was no difference in relaxations in response to levcromakalim. Responses to acetylcholine were not altered by nitric oxide inhibitors, but were abolished by charybdotoxin in combination with apamin, which blocked the EDHF component of the response. 40Gap27 significantly attenuated the response to acetylcholine in the LZRs, but had no effect in the OZRs. Connexin 40 protein and Cx40 mRNA levels in mesenteric vascular homogenates were significantly smaller in the OZRs than in the LZRs, with no difference in connexin 43 or Cx43 mRNA levels.

CONCLUSIONS/INTERPRETATION

These findings demonstrate that endothelial dysfunction in mesenteric arteries from the insulin-resistant OZRs can be attributed to a defect in EDHF. The results also suggest that the defective EDHF is at least partly related to an impairment of connexin 40-associated gap junctions, through a decrease in connexin 40 protein and Cx40 mRNA expression in the OZRs.

Reduced fear and aggression and altered serotonin metabolism in Gtf2ird1-targeted mice

The GTF2IRD1 general transcription factor is a candidate for involvement in the varied cognitive and neurobehavioral symptoms of the microdeletion disorder, Williams-Beuren syndrome (WBS). We show that mice with heterozygous or homozygous disruption of Gtf2ird1 exhibit decreased fear and aggression and increased social behaviors. These findings are reminiscent of the hypersociability and diminished fear of strangers that are hallmarks of WBS. Other core features of WBS, such as increased anxiety and problems with spatial learning were not present in the targeted mice. Investigation of a possible neurochemical basis for the altered behaviors in these mice using high-performance liquid chromatography analysis showed increased levels of serotonin metabolites in several brain regions, including the amygdala, frontal cortex and parietal cortex. Serotonin levels have previously been implicated in fear and aggression, through modulation of the neural pathway connecting the prefrontal cortex and amygdala. These results suggest that hemizygosity for GTF2IRD1 may play a role in the complex behavioral phenotype seen in patients with WBS, either individually, or in combination with other genes, and that the GTF2I transcription factors may influence fear and social behavior through the alteration of neurochemical pathways.

Antibacterial activity within degradation products of biological scaffolds composed of extracellular matrix

Biological scaffolds composed of extracellular matrix (ECM) have been shown to be resistant to deliberate bacterial contamination in preclinical in vivo studies. The present study evaluated the degradation products resulting from the acid digestion of ECM scaffolds for antibacterial effects against clinical strains of Staphylococcus aureus and Escherichia coli. The ECM scaffolds were derived from porcine urinary bladder (UBM-ECM) and liver (L-ECM). These biological scaffolds were digested with acid at high temperatures, fractionated using ammonium sulfate precipitation, and tested for antibacterial activity in a standardized in vitro assay. Degradation products from both UBM-ECM and L-ECM demonstrated antibacterial activity against both S. aureus and E. coli. Specific ammonium sulfate fractions that showed antimicrobial activity varied for the 2 different ECM scaffold types. The results of this study suggest that several different low-molecular-weight peptides with antibacterial activity exist within ECM and that these peptides may help explain the resistance to bacterial infection provided by such biological scaffolds.

Compartment-specific phosphorylation of phosducin in rods underlies adaptation to various levels of illumination

Phosducin is a major phosphoprotein of rod photoreceptors that interacts with the Gbetagamma subunits of heterotrimeric G proteins in its dephosphorylated state. Light promotes dephosphorylation of phosducin; thus, it was proposed that phosducin plays a role in the light adaptation of G protein-mediated visual signaling. Different functions, such as regulation of protein levels and subcellular localization of heterotrimeric G proteins, transcriptional regulation, and modulation of synaptic transmission have also been proposed. Although the molecular basis of phosducin interaction with G proteins is well understood, the physiological significance of light-dependent phosphorylation of phosducin remains largely hypothetical. In this study we quantitatively analyzed light dependence, time course, and subcellular localization of two principal light-regulated phosphorylation sites of phosducin, serine 54 and 71. To obtain physiologically relevant data, our experimental model exploited free-running mice and rats subjected to controlled illumination. We found that in the dark-adapted rods, phosducin phosphorylated at serine 54 is compartmentalized predominantly in the ellipsoid and outer segment compartments. In contrast, phosducin phosphorylated at serine 71 is present in all cellular compartments. The degree of phosducin phosphorylation in the dark appeared to be less than 40%. Dim light within rod operational range triggers massive reversible dephosphorylation of both sites, whereas saturating light dramatically increases phosphorylation of serine 71 in rod outer segment. These results support the role of phosducin in regulating signaling in the rod outer segment compartment and suggest distinct functions for phosphorylation sites 54 and 71.

The other group G Streptococcus: increased detection of Streptococcus canis ulcer infections in dog owners

beta-Hemolytic Lancefield group G Streptococcus dysgalactiae and Streptococcus canis cannot be distinguished when only Lancefield typing is performed. Phenotypic testing and 16S rRNA gene sequencing identified S. canis associated with ulcer infections in dog owners. Because S. canis may be incorrectly identified (published biochemical descriptions are inconsistent), there may be an underestimation of the true number of infections. Identification of group G streptococci to the species level could have epidemiological and clinical implications.

Laforin is a cell membrane and endoplasmic reticulum-associated protein tyrosine phosphatase

Lafora disease (LD) is the only progressive myoclonus epilepsy with polyglucosan bodies. Among conditions with polyglucosan bodies, LD is unique for the subcellular location of its polyglucosans in neuronal perikarya and dendrites and not in axons. Here we report that the protein encoded by the EPM2A gene, which is mutated in LD, localizes at the plasma membrane and the endoplasmic reticulum and that it is a functional protein tyrosine phosphatase. The significance of these findings in the epilepsy of LD and in the origin and characteristic subcellular location of Lafora bodies is discussed.

Thrombocytopenic purpura associated with brucellosis: report of 2 cases and literature review

Mild hematologic abnormalities are common in the course of human brucellosis; however, they generally resolve promptly with treatment of the disease. Occasionally, thrombocytopenia is severe and can be associated with bleeding into the skin (purpura) and from mucosal sites. We describe 2 patients infected with Brucella melitensis who presented with thrombocytopenic purpura, and we review 41 additional cases from the literature. Patients ranged in age from 2 to 77 years, and both sexes were affected equally. In the majority of cases, examination of the bone marrow revealed abundant megakaryocytes. Possible mechanisms involved in thrombocytopenia include hypersplenism, reactive hemophagocytosis, and immune destruction of platelets. Recognition of this complication is essential, since hemorrhage into the central nervous system is associated with a high mortality rate.

Immunoprophylaxis against klebsiella and pseudomonas aeruginosa infections. The Federal Hyperimmune Immunoglobulin Trial Study Group

To determine if passive immunization could decrease the incidence or severity of Klebsiella and Pseudomonas aeruginosa infections, patients admitted to intensive care units of 16 Department of Veterans Affairs and Department of Defense hospitals were randomized to receive either 100 mg/kg intravenous hyperimmune globulin (IVIG), derived from donors immunized with a 24-valent Klebsiella capsular polysaccharide plus an 8-valent P. aeruginosa O-polysaccharide-toxin A conjugate vaccine, or an albumin placebo. The overall incidence and severity of vaccine-specific Klebsiella plus Pseudomonas infections were not significantly different between the groups receiving albumin and IVIG. There was some evidence that IVIG may decrease the incidence (2.7% albumin vs. 1.2% IVIG) and severity (1.0% vs. 0.3%) of vaccine-specific Klebsiella infections, but these reductions were not statistically significant. The trial was stopped because it was statistically unlikely that IVIG would be protective against Pseudomonas infections at the dosage being used. Patients receiving IVIG had more adverse reactions (14.4% vs. 9.2%).

Mosquito-transmitted malaria acquired in Texas

Malaria was endemic in the United States before World War II. However, locally acquired malaria was thought to have been eradicated. Since the mid-1980s, cases of locally acquired malaria have been described. We report the case of a 62-year-old man who came to the Houston Veterans Affairs Medical Center with fever, malaise, and weakness and was found to have Plasmodium vivax infection on peripheral blood smear. He had not left the country for 37 years and had no previous history of malaria. On specific questioning, he mentioned heavy exposure to mosquitoes. Thus, malaria was presumably transmitted locally by mosquitoes. Subsequently, two other cases of apparently locally acquired, mosquito-transmitted malaria were identified in Houston. Symptoms, signs, and general laboratory test results do not typically suggest a specific diagnosis. Therefore, malaria should be considered in all patients with febrile illnesses, even those without a history of travel.

Disseminated herpesvirus infection during pregnancy

A case of disseminated herpes simplex virus infection during pregnancy is reported, and 26 similar cases are reviewed. The present case was unusual in that it occurred in the 12th week of gestation, whereas all but one of the other cases occurred in the second or third trimester. This rare complication is generally preceded by a flu-like prodrome with or without oral or genital lesions. The clinical presentation is (1) encephalitis without hepatic involvement, (2) hepatitis with or without central nervous system findings, or (3) disseminated skin lesions. When the liver is involved, rapidly progressive hepatic necrosis and severe coagulopathy are common and the mortality is high. Early diagnosis and early institution of antiviral chemotherapy with acyclovir greatly improve the outcome for both mother and infant.

The current spectrum of Staphylococcus aureus infection in a tertiary care hospital

Staphylococcus aureus remains a prominent cause of community- and hospital-acquired infection. This study reviewed 162 cases of S. aureus infection occurring in 120 adults who were hospitalized at a Veterans Affairs Medical Center and referred for consultation to the Infectious Disease Service. There were 37 cases of skin and soft tissue infection, 5 pyomyositis, 34 osteomyelitis, 13 septic arthritis, 19 pneumonia, 3 empyema, 5 pyelonephritis, 37 vascular infection, 3 epidural abscess, and 6 miscellaneous infections. Bacteremia was documented in 56 of 119 (47%) cases in which blood cultures were obtained, indicating the serious nature of the infections in many cases. Staphylococcus aureus is widely prevalent in healthy persons. Given its ubiquity and the capacity to cause a broad array of infections, an effective host response must play an important role in preventing infection. This host response is immunologically nonspecific, in that it depends upon the effectiveness of mechanical barriers to invasion and, once invasion takes place, the interaction of PMN, complement, and antibody that is probably present in serum of all immunologically competent adults rather than sensitization of B or T lymphocytes by any identifiable antigens specific to S. aureus. Analysis of the present cases calls attention to S. aureus as an opportunistic pathogen, 1 that only infrequently causes serious infection in otherwise healthy persons. Nearly every patient in this series had 1 or more medical condition thought to predispose to infection; 279 such conditions were identified, representing an average of 2.3 per person. A break in the natural barrier to infection was also present in the majority of cases, for example, trauma, wound, or pre-existing decubitus ulcer in skin and soft tissue infections; endotracheal tube in pneumonia; and a catheter bypassing urethra or skin in urinary and vascular infections, respectively. The tendency for patients to be infected with S. aureus repeatedly (mean number of infections, 1.4 per patient) reflects the chronicity of many predisposing factors and, perhaps, of colonization as well. Staphylococcus aureus has a special predilection to cause infections involving prosthetic devices, perhaps related to its affinity for fibronectin, laminin, and other serum proteins that can mediate attachment to foreign material; 46 of 162 (28%) infections were associated with the presence of a foreign body. Such infections are difficult to eradicate with antibiotic therapy alone, perhaps because of a change in the metabolic state of adherent bacteria, and removal of the foreign body is generally required for cure.(ABSTRACT TRUNCATED AT 400 WORDS)

Serologic diagnosis of human brucellosis: analysis of 214 cases by agglutination tests and review of the literature

The serum agglutination test (SAT) and 2-mercaptoethanol (2ME) agglutination were used in studies of the sera of 214 patients in whom brucellosis was suspected. On the basis of historical, epidemiologic, clinical, and serologic data, four groups were identified: group I (108 cases) had negative agglutination reactions, and brucellosis was considered unlikely; group II (57 cases) had positive agglutination reactions, and active brucellosis was diagnosed; group III (37 cases) had positive agglutination reactions, but other factors--notably, a history of prior infection--made inactive brucellosis likely; and group IV (12 cases) had positive agglutination reactions, but insufficient data were available for further classification. Most patients with active brucellosis had agglutinin titers of greater than or equal to 160; however, no single titer was always diagnostic. Although more sensitive tests are available, agglutination reactions provide data sufficient to differentiate active from inactive disease when other factors are considered and follow-up sera are tested. This article discusses individual cases and reviews the literature on the diagnosis of brucellosis.

Concomitant neurocysticercosis and brucellosis

A young Mexican woman had headache and left arm weakness develop shortly after immigrating to the United States. A solitary cerebral cysticercus was found at surgery, but, instead of the expected finding of clear fluid, the cyst contained pus from which Brucella melitensis was cultured. Although the patient had no signs or symptoms suggestive of brucellosis, agglutination studies revealed IgM and IgG antibodies consistent with active brucellosis. Clinicians should be alert to the possibility of multiple infections in immigrants from countries where parasites and bacteria that are uncommon in the United States are endemic.

Infections associated with prosthetic devices: magnitude of the problem

The number and diversity of prosthetic devices inserted into patients continue to increase each year. Despite technological advances in the design and manufacture of prostheses and improved surgical techniques, infection remains a serious and potentially fatal complication. Although the incidence of serious infections remains low (averaging a few per cent for totally implanted devices), the consequences of an infected prosthesis can be disastrous. The incidence of infections related to temporary or partially implanted devices is even higher than for prostheses completely covered by the skin. In addition to excess morbidity and occasionally mortality, prosthesis-related infections add to the costs of medical care and to prolonged hospitalization. the magnitude of the problem is greatly underappreciated, in part due to the care of such infections on a piecemeal basis by numerous and diverse health care specialists.

Periprosthetic candidal infections following arthroplasty

Candidal infection after prosthetic arthroplasty has been reported in six previous cases, to which four cases are now added. Candida albicans was the offending organism in four patients, Candida parapsilosis in three, Candida tropicalis in two, and Candida (Torulopsis) glabrata in one. None of the 10 patients had evidence of disseminated candidiasis, and, except for the uniform presence of a prosthesis, other underlying factors that are generally associated with candidal infections were present in only three. Clinical features that distinguished periprosthetic from natural bone and joint infection included an older patient population, the usual lack of predisposing factors other than the prosthesis, and the absence of evidence of disseminated candidiasis. All patients were treated with removal of the prosthesis and antifungal therapy, consisting of amphotericin B alone (six patients) or combined with 5-fluorocytosine (three patients) or ketoconazole (one patient). Infection appeared to be cured in nine of the 10 patients, but the follow-up was less than 1 year in five cases. Replacement with a new prosthetic joint was attempted in only two cases and successful in only one. Direct inoculation of organisms during surgery or transient unrecognized candidemia may initiate periprosthetic infection, which might then be promoted by favorable local factors, both mechanical and molecular. The role of prosthetic materials, candidal adhesins, and human factors such as fibronectin in initiating these infections has yet to be characterized.

Native valve endocarditis caused by dysgonic fermenter type 2 bacilli

A chronic alcoholic who had casual contact with dogs developed subacute tricuspid endocarditis caused by the unusual gram-negative bacillus dysgonic fermenter type 2 (DF-2). Despite recurrent pulmonary emboli, the patient had an apparent successful response to 6 weeks of penicillin therapy. Two weeks after discharge, he experienced congestive heart failure necessitating tricuspid valvulectomy. No evidence of active infection was found in tissue removed at surgery. Despite the achievement of a bacteriologic cure, surgery for residual valve damage is not uncommon in endocarditis, regardless of the microbial etiology. In this case, alcoholism was the only risk factor predisposing to infection presumably contracted from exposure to dogs.

Infections in prosthetic devices

Infection in prosthetic devices is a rare but potentially serious complication of prosthesis implant surgery. Infections associated with a variety of permanently implanted devices are reviewed in the context of recent knowledge of the host-prosthesis interaction.

Acute brucella ileitis

Human brucellosis is an enteric fever in which systemic symptoms are generally more prominent than gastrointestinal complaints. During an outbreak of infection caused by Brucella melitensis, linked to ingestion of unpasteurized goat milk cheese, we treated a child with radiographic evidence of acute ileitis. Alimentary tract involvement in brucellosis is reviewed.

Manifestations of sepsis

The clinical manifestations of sepsis may be flagrant or subtle. Awareness of the signs and symptoms of sepsis allows early recognition and prompt, appropriate management. The clinical presentation, relative frequency, and current pathophysiologic understanding of the manifestations of sepsis are reviewed. Special emphasis is placed on the cardiopulmonary manifestations, which are examined in a temporal sequence of preshock, early shock, and late shock states. While therapy for the underlying infection (such as antibiotics and drainage of abscesses) is often sufficient, therapy for the specific manifestations of sepsis may also be necessary. Guidelines for therapy for these manifestations of sepsis are given.

Bacterial remnants in an aortic valve after treatment for staphylococcal endocarditis

A patient with staphylococcal endocarditis was treated for 6 weeks with high doses of nafcillin. Despite a prompt clinical response and bacteriologic cure, residual damage to the aortic valve led to severe congestive heart failure necessitating surgery. Valve tissue obtained at surgery was sterile, but organisms consistent with staphylococci were observed in the inflammatory infiltrate by light and electron microscopy.

Urban outbreak of goat cheese brucellosis

In 1983 an outbreak of human brucellosis caused by Brucella melitensis occurred among residents of a predominantly Hispanic neighborhood in Houston, TX. The source of the infections was traced to unpasteurized goats' milk cheese imported from Mexico. Nineteen of the 31 patients who contracted the disease were members of 5 families, which included 11 children ranging in age from 2 to 17 years. Infection was generally associated with protein complaints and a paucity of physical findings. Both immunoglobulin M and immunoglobulin G agglutinins were present in acute phase sera in the majority of patients, and low titers of immunoglobulin M antibodies remained in the sera of 43% who were retested 2 years later. Trimethoprim-sulfamethoxozole was highly effective in the treatment of children with brucellosis and was associated with no relapses.

Antimicrobial susceptibility of clinical isolates of Brucella

A number of antimicrobial agents have been used in the treatment of human brucellosis with varying effectiveness. The purpose of this study was to test the in vitro susceptibility of isolates of four Brucella species to a variety of antimicrobial agents, and to study in vitro synergy of combinations of agents. Minimal inhibitory concentrations (MICs) were determined using conventional broth microdilution methods and commercially available systems. Conventional checkerboard synergy microdilutions were prepared for gentamicin or streptomycin plus tetracycline, and rifampicin plus tetracycline. Synergy or antagonism was determined by the fractional inhibitory concentration index. Penicillin G and ampicillin showed in vitro activity against Brucella (MIC90 4 micrograms/ml), whereas the antipseudomonal penicillins were less active (carbenicillin MIC90 12 micrograms/ml, piperacillin MIC90 32 micrograms/ml). Among the third generation cephalosporins tested, cefotaxime (MIC90 2 micrograms/ml) demonstrated greatest activity. As a class, aminoglycosides were equivalent (MIC90 1-4 micrograms/ml). All strains were sensitive to tetracycline (MIC90 0.25 microgram/ml), trimethoprim-sulfamethoxazole (MIC90 1/19 micrograms/ml), and rifampin (MIC90 1 microgram/ml). Erythromycin (MIC90 greater than 8 micrograms/ml) and vancomycin (MIC90 greater than 16 micrograms/ml) demonstrated no activity. In vitro synergy (fractional inhibitory concentration index less than 0.5) was demonstrated with tetracycline plus rafampin in six of eight isolates tested.

Culture-negative endocarditis with purpura and arterial emboli

We have presented a case of culture-negative endocarditis in which purpura and arterial emboli were the major findings, and in which echocardiograms were normal, but angiograms revealed vegetations and unsuspected severe aortic valve insufficiency.

Antibiotic resistance patterns during aminoglycoside restriction

When amikacin first became available its use was restricted to prevent the emergence of resistant strains of gram-negative bacilli to this new agent. Gentamicin was the aminoglycoside most widely used at this time, and the incidence of gentamicin-resistant bacteria was 14%, while only 2.4% were resistant to amikacin. For a period of 15 months gentamicin use was restricted, and amikacin was used almost exclusively. Amikacin use was associated with a fall in the incidence of gentamicin-resistant bacteria to 9.2% (p less than .00005), while amikacin resistance remained unchanged at 2.2% (NS). During a period of 21 months after all aminoglycoside restrictions were lifted, gentamicin use again increased, and was accompanied by a return of gentamicin resistance to the baseline level of 15.3%. During this period, amikacin resistance also increased to 4.0% (p less than .0000001) but was due primarily to an increase in resistant Pseudomonas aeruginosa. Escherichia coli was the most frequently isolated gram-negative bacillus during all three periods, and it remained sensitive to both antibiotics regardless of the drug in use. In contrast, P. aeruginosa showed a high level of resistance to gentamicin, which fell when this antibiotic was restricted, only to return to a high level with reinstitution of gentamicin. While there was also an increase in amikacin resistant strains of P. aeruginosa with unrestricted aminoglycoside use, there was no apparent shift in the pattern of aminoglycoside modifying enzymes among a small random selection of amikacin-resistant bacteria. Impaired uptake of antibiotic was the predominant mechanism responsible for P. aeruginosa resistance among strains that did not produce aminoglycoside acetyltransferase (AAC)(6').

Pacemaker associated infection due to a corynebacterium species

Pacemaker associated infection (PAI) is a rare but often serious complication of permanent or temporary transvenous cardiac pacemakers. The major risk factor is recent or multiple pacemaker manipulations or surgical procedures. A PAI can occur at the time of insertion, from contiguous spread to the access site, or from transient bacteremia. We report a case of PAI of a retained pacemaker electrode from which a Corynebacterium species was isolated. Multiple preoperative cultures were sterile, but bacteria were isolated from tissue removed at surgery, and were seen around the wire deep inside a thrombus. The importance of cultures and special stains (including electron microscopy) of surgical materials is stressed, especially when dealing with microorganisms of ordinarily low virulence, or those that are commonly considered laboratory contaminants.

Phagocytosis and killing of Brucella by human polymorphonuclear leukocytes

Although cellular immunity involving activated macrophages is important in resistance to Brucella, serum factors and polymorphonuclear leukocytes (PMNLs) play some role in the initial response to infection. The interaction between human PMNLs and virulent and attenuated strains of Brucella abortus and Brucella melitensis was studied by in vitro techniques. Virulent and attenuated strains of both species were rapidly phagocytosed after opsonization with normal human serum (NHS); nonopsonized bacteria were not phagocytosed. In contrast, NHS devoid of detectable antibodies was bactericidal for strains of B. abortus but not of B. melitensis. In addition, intracellular killing of ingested bacteria was shown for virulent B. abortus but not for B. melitensis. Ultrastructural studies revealed morphological alterations in about one-half of phagocytosed B. abortus and B. melitensis after incubation for 10 min; thereafter, nearly 100% of B. abortus showed some degree of degeneration, whereas B. melitensis remained intact during 120 min of observation.

Human brucellosis

Despite advances in the control of the disease in animals, brucellosis is a zoonosis with important economic impact in the United States. It is estimated that cases of brucellosis in humans are underdiagnosed and underreported and that the disease continues to be a major human health hazard. Nine active cases of brucellosis in humans were documented in Houston, Texas between June 1981 and June 1982. These cases, plus an additional case of chronic brucellosis, served as the impetus for this review of the protean manifestations of the disease in humans.

Osteomyelitis beneath pressure sores

Twenty-eight pressure sores were evaluated prospectively. Osteomyelitis was reported histologically in nine of 28 bones and pressure-related changes were reported in 14 bones. Roentgenograms suggested the presence of osteomyelitis in four instances of histologically proved osteomyelitis. Technetium Tc 99m medronate bone scans were highly sensitive, showing increased uptake in all cases of osteomyelitis; however, increased uptake also occurred commonly in uninfected bones due to pressure-related changes or other noninfectious causes. Cultures of bone biopsy samples usually disclosed anaerobic bacteria, gram-negative bacilli, or both. The diagnosis of osteomyelitis must be considered if a pressure sore does not respond to local therapy. If the technetium Tc 99m medronate uptake is increased in the involved area, or roentgenographic findings are abnormal, the diagnosis can only be made with certainty by histologic examination of bone. Antibacterial treatment should be selected based on the results of bone culture.

Necrotizing pneumonia and empyema caused by Bacillus cereus and Clostridium bifermentans

A patient with no known immune compromise presented with necrotizing pneumonia and a pleural effusion. Thoracentesis yielded a sanguinopurulent, foul smelling exudate that showed sheets of polymorphonuclear leukocytes and many gram-positive bacilli. A tube thoracostomy was performed and treatment with intravenous penicillin G was begun. Twenty-four hours later a Bacillus species later identified as Bacillus cereus was identified from aerobic cultures. Because the organism was resistant to penicillin, the patient was switched to intravenous chloramphenicol. A second organism was noted to grow slowly under anaerobic conditions and was later identified as Clostridium bifermentans. Despite initial clinical improvement, fever and empyema persisted resulting in a thoracotomy with resection of the infected lung and extensive decortication. Specimens from the lung tissue obtained at surgery also grew both Bacillus cereus and Clostridium bifermentans. Subsequent review of the original pleural fluid smears revealed a degree of pleomorphism that was not initially appreciated. Prompt surgical intervention combined with appropriate antibiotics resulted in a cure of this unusual aerobic/anaerobic infection.

Studies on the pathogenesis of the Jarisch-Herxheimer reaction: development of an animal model and evidence against a role for classical endotoxin

The etiology of the Jarisch-Herxheimer reaction is unknown, but the reaction may result from toxic products of dead or dying treponemes reacting with sensitized syphilitic tissues. Because of similarities of spirochetes with gram-negative bacteria, endotoxin has been proposed as the responsible toxin. In 19 patients with syphilis, a reaction occurred in 15 (79%) during treatment with penicillin. Endotoxemia was not found by the limulus amoebocyte lysate test. All animal model of the Jarisch-Herxheimer reaction was developed in rabbits infected with Treponema pallidum. When treated with penicillin, 18 (78%) of 23 rabbits infected 18-29 days previously developed a reaction that resembled that in humans. Endotoxemia was not detected by the lysate test. After the reaction, rabbits were not refractory to the pyrogenic effects of endotoxin, and syphilitic rabbits rendered tolerant to endotoxin still developed fever when treated with penicillin. These data suggest that classical endotoxin is not the cause of the Jarisch-Herxheimer reaction.

Staphylococcal nasal carriage and subsequent infection in peritoneal dialysis patients

Thirty patients undergoing long-term home-based peritoneal dialysis were monitored for 13 months for carriage of Staphylococcus aureus in the nares and for the development of infectious complications. The patients could be divided into three groups with regard to S aureus carriage: chronic, intermittent, and noncarriers. Twenty-five episodes of peritonitis and 20 episodes of catheter exit-site infections occurred during 268 patient-months of observation. Staphylococcus aureus accounted for eight episodes of peritonitis and 12 episodes of exit-site infection. Chronic and intermittent carriers of S aureus were found to be at higher risk of development of infection than noncarriers.

Clinical significance of coagulase-negative staphylococci

Although coagulase-negative staphylococci (C-NS) have been implicated in certain human infections, they are generally regarded as contaminants, and their clinical significance is questioned. To assess their role as pathogens, we studied 205 isolates of C-NS from wounds and body fluids (blood, urine, pleural and peritoneal fluids, etc.). Patient's charts were reviewed, and, by using strict criteria, a determination was made regarding the clinical significance of these isolates. The organisms were then identified to determine whether certain species of C-NS were associated with specific infections. S epidermidis sensu stricto accounted for 81% of the C-NS isolated. The frequencies of other species were: S. haemolyticus (6%), S. hominis (5%), S. capitis (4%), S. warneri (3%), and others (1%). Only two isolates were novobiocin resistant; neither was identified as S. saprophyticus. By using our criteria, 22% of the C-NS were considered to be clinically significant, and the majority of these (93%) was S. epidermidis. The most common source of the clinically relevant C-NS isolates was wounds. These data suggest that identification of C-NS species other than S. epidermidis may be of limited value in predicting clinical significance.