Increased saturated triacylglycerol levels in plasma membranes of human neutrophils stimulated by lipopolysaccharide

Neutrophils isolated from patients with bacterial infections or stimulated in vitro with lipopolysaccharide (LPS) produce a high resolution, lipid-dominated spectrum on 1H-NMR spectroscopy (May et al, 1993. J. Infect. Dis. 168: 386-392). We have investigated the origin of this lipid signal using NMR and chemical analyses of both whole neutrophils and purified plasma membranes. Plasma membranes from neutrophils that had been stimulated with 50 microg/ml LPS exhibited the high resolution 1H-NMR signal, and contained double the triacylglycerol (TAG) content of plasma membranes isolated from resting cells. Chemical analysis of the whole cells indicated that the TAG also increased at the cellular level (1.7-fold) after stimulation with LPS. Diradylglycerol increased 2- to 3-fold in both whole cells and plasma membranes after stimulation, but was only a minor component compared with TAG. The plasma membrane protein/phospholipid ratio increased 2.6-fold, whereas cholesterol (free and esterified) was unchanged. The membranes from LPS-stimulated neutrophils exhibited increased fluidity, as judged by increased merocyanine 540 binding, consistent with a 2-fold reduction in cholesterol/phospholipid ratio. LPS induced a shift in fatty acid content of whole cell polar lipids towards more oleic acid and less palmitic acid, whereas the neutral lipid fraction contained increased amounts of palmitic and stearic acids. The TAG fraction of plasma membrane lipids contained increased amounts of palmitic acid when prepared from cells stimulated with LPS. We conclude that the 1H-NMR signal in LPS-stimulated neutrophils arises from increased amounts of plasma membrane TAG with an elevated content of palmitic acid.

Identification of pathogenic yeasts of the imperfect genus Candida by polymerase chain reaction fingerprinting

With the increase in the number of immunocompromised hosts, the number of fungal pathogens has increased markedly. Identification and classification, especially of yeast species and strains, is often difficult when based solely on phenotypic characteristics. Since it became clear that different fungal pathogens require specific treatment strategies, there is a need for simple, rapid and reliable methods to identify fungal isolates. Polymerase chain reaction (PCR) fingerprinting was successfully applied here to identify yeast isolates. Microsatellite [(GTG)5; (GACA)4] and minisatellite [(5'GAGGGTGGCGGTTCT 3'), derived from the core-sequence of the phage M13] specific primers were used as single primers in the PCR to amplify hypervariable interrepeat DNA sequences from over 200 European, American and Australian clinical isolates within the genus Candida. Each species, represented by its type strain, could be identified by a specific multilocus pattern, allowing for the assignment of all the isolates to the appropriate species. Intra-species variation in the multilocus profiles was about 20% compared to inter-species variation, which was up to 80%. Anamorph-teleomorph pairs could be identified by highly homologous PCR fingerprint patterns. PCR fingerprinting was more discriminatory when compared with routinely used biochemical tests (Vitek YBC and API ID 32C). PCR fingerprinting has proven to be a powerful tool for the identification of medically important yeasts. It is rapid, sensitive, reliable, highly reproducible, stable in vitro and in vivo, and applicable to large scale experiments. Potential applications include: yeast taxonomy, epidemiology, environmental surveys, and improvement of the diagnosis of mycotic diseases.

Oxidative stress and the mobilisation of arachidonic acid in stimulated human platelets: role of hydroxyl radical

Platelet functions, including eicosanoid biosynthesis, can be significantly altered by exposure to reactive oxygen species. We utilised the redox properties of the phenazine derivative, pyocyanin, to generate low micromolar levels of reactive oxygen species in order to investigate the metabolism of arachidonic acid by human platelets under oxidative stress. Eicosanoid production by platelets, pre-labelled with [3H]arachidonic acid (AA) and stimulated with the calcium ionophore A23187, was inhibited in the presence of pyocyanin. In contrast, platelets pre-treated with pyocyanin and concurrently exposed to A23187 and AA showed no evidence of inhibition. Analysis of the free label content of labelled, pyocyanin-treated platelets after stimulation revealed diminished levels of total free label and a corresponding increase in labelled phospholipid. Prior treatment with the antioxidants, superoxide dismutase, catalase or the hydroxyl radical scavenger, mannitol, before the addition of pyocyanin afforded protection against loss of eicosanoid production and restored AA release. We conclude that hydroxyl radicals inhibit one or more steps in the cascade leading to phospholipase A2 activation and release of arachidonic acid from platelet phospholipid stores.

Modulation of neutrophil superoxide response and intracellular diacylglyceride levels by the bacterial pigment pyocyanin

Low concentrations of pyocyanin are reported to enhance superoxide production by human neutrophils exposed to various stimuli, yet the mechanism remains unknown. Using lucigenin-enhanced chemiluminescence, we examined the kinetics of the neutrophil superoxide response in the presence of pyocyanin. At all concentrations (12.5 to 200 microM), pyocyanin decreased the peak superoxide response while prolonging the duration of the response. The prolonged response may be associated with an observed increase in intracellular diacylglyceride levels due to pyocyanin exposure.

Identification of extracellular phospholipase B, lysophospholipase, and acyltransferase produced by Cryptococcus neoformans

We recently identified phospholipase activity as a potential virulence factor of Cryptococcus neoformans. We have now defined the nature of the phospholipase activity produced by a clinical isolate of C. neoformans var. neoformans, under native conditions, by 1H and 31P nuclear magnetic resonance (NMR) spectroscopy and thin-layer chromatography (TLC) of radiolabelled substrates. Glycerophosphocholine was identified by NMR spectroscopy as the sole phospholipid degradation product of the reaction between substrate phosphatidylcholine (PC) and cryptococcal culture supernatants indicating the presence of phospholipase B (PLB). No lysophosphatidylcholine (lyso-PC) or products indicative of phospholipase C, phospholipase D, or other lipase activity were identified. Use of PC and lyso-PC containing radiolabelled acyl chains and separation of products by TLC confirmed the PLB and lysophospholipase (LPL) activities. Lysophospholipase transacylase (LPTA) activity was identified by the formation of radioactive PC from lyso-PC. Extracellular enzyme production was maximal after 6 to 10 h in fresh medium. Assay conditions were optimized for pH, linearity with time, enzyme concentration, and saturation by substrates to allow comparison with phospholipases from other organisms. LPL activity was 10- to 20-fold greater than PLB activity, with mean (+/- standard deviation) specific activities of 34.9 +/- 7.9 and 3.18 +/- 0.2 micromol of substrate hydrolyzed per min per mg of protein, respectively. The response of PLB to increasing substrate concentrations was bimodal, whereas inhibition of LPL and LPTA activities occurred at concentrations of substrate lyso-PC greater than 200 microM. Enzyme activities were stable at acid pH (3.8), with pH optima of 3.5 to 4.5. Activities were unchanged in the presence of exogenous serine protease inhibitors, divalent cations, and EDTA. We conclude that C. neoformans produces highly active extracellular PLB, LPL, and LPTA under native conditions.

Phospholipase activity in Cryptococcus neoformans: a new virulence factor?

Fifty isolates of Cryptococcus neoformans were examined for extracellular phospholipase production after inoculation onto egg yolk agar; 49 produced a pericolonial precipitate indicative of phospholipase activity. Phospholipase B (PLB), lysophospholipase, and lysophospholipase-transacylase activities were identified by radiometric analysis in supernatants from 4 clinical isolates. The ratio of colony diameter to colony plus precipitate on agar (Pz) correlated with PLB activity. Phospholipase production was similar in 12 environmental and 13 clinical isolates of C. neoformans var. gattii. Environmental strains of C. neoformans var. neoformans (n = 8) produced more phospholipase at 72 h than did 17 clinical isolates (mean Pz, 0.57 vs. 0.72; P < .01); however, Pz values were similar at 96 h. Quantitation of cryptococci in the lungs and brains of BALB/c mice inoculated intravenously with 4 strains expressing high, intermediate, or low phospholipase activity revealed a correlation between phospholipase activity and virulence. Phospholipases secreted by C. neoformans may be implicated in virulence.

Changes in cellular and plasma membrane phospholipid composition after lipopolysaccharide stimulation of human neutrophils, studied by 31P NMR

Lipopolysaccharide (endotoxin, LPS) exerts potent proinflammatory effects on neutrophils which may involve membrane phospholipid metabolism. The cellular and plasma membrane phospholipid composition of resting neutrophils and those stimulated with 50 microg ml(-1) LPS were studied by 31P NMR and chemical analysis. A rapid new method for plasma membrane purification was employed, involving the direct lysis of cytoplasts. Chemical analyses showed that, although total cellular phospholipid content did not change with LPS stimulation, there was twice the amount of phospholipid present in plasma membranes isolated from stimulated cells, resulting in a lowered cholesterol/phospholipid ratio. Since internal membranes have lower cholesterol content this result is consistent with an origin from insertion of these membranes (most probably from the endoplasmic reticulum) into the plasma membrane, thereby increasing its fluidity. The individual phospholipid classes of both cells and membranes were quantified by 31P-NMR spectroscopy after dissolution in sodium cholate without prior extraction of lipids, allowing partial resolution of the major phospholipid classes and ether-linked phospholipids. Ether-linked lipids were distinguished from diacyl phospholipids by hydrolysis of lipid extracts with HCl and phospholipase A1, There was a significant increase in phosphatidylserine in both cells and plasma membranes after stimulation, with a decrease in the phosphatidylethanolamine (diacyl and plasmalogen) content in the cells. Plasma membranes from stimulated cells exhibited a significant decrease in a phospholipid tentatively identified as 2-arachidonoyl-1-alkyl-sn-glycero-3-phosphocholine, a precursor of the lipid inflammatory mediator, platelet-activating factor. This report is the first to elaborate the changes in phospholipid composition in human neutrophils as a whole, and in plasma membranes separated from them, before and after stimulation by the physiological activator, LPS.

Characterization of Cryptococcus neoformans by random DNA amplification

Random amplified polymorphic DNA (RAPD) was optimized and used to distinguish between the varieties and serotypes of Cryptococcus neoformans. The RAPD technique distinguished between serotypes A, D or AD within C. neoformans var. neoformans, and revealed further differentiation within each serotype. Four RAPD profiles were clearly recognizable within C. neoformans var. gattii, although its two serotypes, B and C, were only differentiated with one primer combination out of seven.

Managing HIV. Part 7: Professional issues. 7.1 HIV infection control in medical practice

Reports of cross-infection with HIV and hepatitis C during routine surgery in Sydney have refocused attention on preventing transmission of HIV and other blood-borne viruses in the health care setting. This review examines the risks of transmission in medical practice, summarises infection control measures and examines issues regarding the HIV-infected health care worker.

Natural environmental sources of Cryptococcus neoformans var. gattii

We sought evidence for new environmental sources of Cryptococcus neoformans var. gattii by random amplification of polymorphic DNA (RAPD) analysis of isolates from 29 animals with a restricted territorial range in five Australian states. Twenty-three of the 29 isolates and 45 of 45 eucalypt isolates tested previously exhibited one RAPD profile, VGI. RAPD profile VGII was identified in 6 of 17 isolates from domesticated species but in none of 12 native species. Four VGII isolates originated from an area of Western Australia with no natural stands of known eucalypt host, indicating the existence of at least one unrecognized natural source of C. neoformans var. gattii.

Concordance of clinical and environmental isolates of Cryptococcus neoformans var. gattii by random amplification of polymorphic DNA analysis and PCR fingerprinting

Sixty-one clinical and forty-nine environmental isolates of Cryptococcus neoformans var. gattii from Australia and the United States were analyzed by random amplification of polymorphic DNA (RAPD), using 12- to 22-mer primers in pairs, and/or PCR fingerprinting with a single primer derived from the microsatellite core sequence of the wild-type phage M13 (5' GAGGGTGGCGGTTCT 3'). Three major genetic profiles were identified by both typing techniques. A single RAPD profile (VGI) predominated among clinical isolates (44 of 48, 92%) and isolates from host eucalypts (45 of 45, 100%) from Australia. Of the 94 Australian isolates, 4 (3 clinical and 1 environmental) were assigned to profile VGII; 2 of these were recovered from patients and one was recovered from plant debris from Western Australia. Only one Australian clinical isolate was assigned to profile VGIII. A different distribution of RAPD profiles (four VGIII, two VGII, and one VGI) was found among four clinical and three environmental isolates from the United States. RAPD profiles of 8 of the 101 isolates studied revealed minor genetic variants, 4 of profile VGI and 4 of profile VGII. Genetic concordance between the majority of clinical and environmental isolates in Australia is consistent with the hypothesis that human disease is acquired from exposure to host eucalypts. Profiles of clinical isolates were independent of body site of infection, and profiles of all isolates were stable over time. Analysis by PCR fingerprinting confirmed the RAPD results. A second RAPD profile (VGII) was associated with infection in southwest Western Australia, where the two host eucalypts do not occur naturally. This raises the possibility of an alternative and as yet unidentified natural habitat of C. neoformans var. gattii. Our results indicate that RAPD analysis is a sensitive and useful method for investigating environmental sources of human infection with this biotype.

Identification by random amplification of polymorphic DNA of a common molecular type of Cryptococcus neoformans var. neoformans in patients with AIDS or other immunosuppressive conditions

Sixty clinical isolates of Cryptococcus neoformans var. neoformans were analyzed by random amplification of polymorphic DNA (RAPD) using 12- to 22-mer primers in pairs. Five major profiles, which clearly distinguished between serotypes A (profiles I-III), AD (profile IV), and D (profile V), were identified. Forty-two of 58 serotype A isolates were assigned to profile I, 13 to profile II, and 3 to profile III. Profile I compromised 5 subtypes (profiles Ia-Ie), with 37 to 42 isolates in profile Ia. Twenty-seven of 28 isolates from patients with AIDS belonged to profile Ia (P<.001), as did 7 of 10 isolates from otherwise immunocompromised patients. Isolates from immunocompetent hosts were broadly distributed (profile I, 8 isolates; profile II, 10 isolates; profile III, 2 isolates). RAPD profiles were independent of body site and geographic origin of isolates. Isolates pairs from 3 patients produced identical profiles. A predominant genetic profile among serotype A strains from AIDS patients has not been reported previously.

Inhibition of the human platelet cyclooxygenase response by the naturally occurring phenazine derivative, 1-hydroxyphenazine

The phenazine derivative, 1-hydroxyphenazine (OHP), is produced in vivo by Pseudomonas aeruginosa, an organism that colonises the airways of patients with cystic fibrosis. While known to inhibit leukotriene production by human neutrophils, the effects of OHP on cyclooxygenase pathways have not previously been reported. We used [3H] arachidonic acid (AA) under conditions of concurrent labelling-stimulation or pre-labelling for one hour followed by stimulation to determine the effects of OHP on the production of cyclooxygenase metabolites by human platelets stimulated with the calcium ionophore, A23187. Thromboxane B2 (TxB2) and 12-hydroxyheptadecatrienoic acid (HHT) production was inhibited in a dose-dependent manner by OHP using either pre-labelled or concurrently labelled platelets. However, production of 12-hydroxyeicosatetraenoic acid (12-HETE) was not diminished. Determination of the amount of total free label (AA+non-esterified AA metabolites) after stimulation of pre-labelled platelets indicated a dose-dependent inhibition of the release of AA from phospholipid by OHP. This was reflected in a corresponding increase in phospholipid AA content. These data indicate that phenazine derivatives of bacterial origin exhibit complex interactions with pathways of arachidonic acid metabolism in host cells. These effects may prove to be of pharmacological importance.

Cryptococcal disease of the CNS in immunocompetent hosts: influence of cryptococcal variety on clinical manifestations and outcome

We performed a retrospective review of cases of cerebral cryptococcosis among patients admitted to 12 Australian teaching hospitals between 1985 and 1992. Of 118 cases identified, 35 occurred in immunocompetent hosts. When cases due to Cryptococcus neoformans variety neoformans were compared with those due to Cryptococcus neoformans variety gattii, we found that the latter tended to occur in healthy hosts whose residence or job was located in a rural area, and cerebral mass lesions and/or hydrocephalus and pulmonary mass lesions were more common. For a subgroup of patients with infection due to C. neoformans variety gattii, multiple enhancing lesions were observed on cerebral computed tomograms, and papilledema, high CSF and serum cryptococcal antigen titers, and a worse prognosis (despite prolonged amphotericin B therapy and intraventricular shunt insertion) were also noted. No significant difference in clinical course or outcome in terms of variety of C. neoformans was noted for patients with cryptococcal meningitis whose computed tomographic scans appeared normal on presentation.

Eicosapentaenoic acid modulates neutrophil leukotriene B4 receptor expression in cystic fibrosis

In patients with cystic fibrosis (CF), high intrapulmonary concentrations of the neutrophil chemotaxin leukotriene B4 (LTB4) are associated with specific reduction of LTB4-induced chemotaxis of circulating neutrophils. The chemotactic abnormality is partially corrected by dietary supplementation with eicosapentaenoic acid (EPA). LTB4-induced neutrophil chemotaxis is mediated by specific, high-affinity, cell surface LTB4 receptors. The hypotheses that neutrophil LTB4 receptors are down-regulated in CF, and that EPA normalizes receptor expression, were tested by measuring the number (Rmax) and affinity (Kd) of LTB4 receptors on neutrophils from eight CF patients before and after EPA (6 weeks of 2.7 g/day), and from nine normal individuals. High-affinity receptor Rmax was depressed in CF patients (0.6 +/- 0.2 x 10(4)/cell (mean +/- s.d.) versus 1.8 +/- 0.7 x 10(4)/cell in normals), but corrected to normal (2.0 +/- 1.9 x 10(4)/cell) after EPA. High-affinity receptor Kd was depressed in CF patients (0.4 +/- 0.3 nM versus 1.4 +/- 0.5 nM in normals), and also corrected to normal with EPA (1.4 +/- 1.2 nM). Low-affinity receptors were depressed, but did not change significantly with EPA. These results indicate that neutrophil responses in chronic inflammatory lung disease can be influenced directly by LTB4 receptor modulation, and that this effect of EPA predominates over alterations in neutrophil signal transduction in situations of chronic exposure to LTB4.

Amebic abscess of the spleen complicated by metronidazole-induced neurotoxicity: case report

We describe a patient with a liver abscess due to Entamoeba histolytica, in whom metronidazole therapy (total dose, 21 g over 14 days) was complicated by reversible deafness, tinnitus, and ataxia and who relapsed 5 months later with a splenic abscess. Two courses of tinidazole (the second in combination with percutaneous aspiration of the abscess) were required to achieve cure.

Hospital practices influence the pattern of infective endocarditis

OBJECTIVE

To identify factors contributing to infective endocarditis at a major teaching hospital.

METHODS

Retrospective review of clinical records of patients diagnosed with endocarditis by standard case definitions with respect to causative organisms, clinical features and outcome.

RESULTS

One hundred and ninety-three episodes of endocarditis seen between 1979 and 1992 at Westmead Hospital, Sydney, were reviewed. In the 174 cases where the causative organism was isolated, 75 (43%) were Staphylococcus aureus and 50 (29%) were viridans streptococci. Nosocomial acquisition and/or inter-hospital transfer accounted for 83 episodes; 48 (58%) S. aureus (P < 0.001) and nine (11%) viridans streptococci (P < 0.001). In cases from the local community, viridans streptococci were more common than S. aureus (37% versus 25%); these included 18 episodes (14 S. aureus) in intravenous drug users.

CONCLUSION

We conclude that, compared with community-acquired infections, the aetiology of endocarditis in a large teaching hospital is influenced strongly by the prevalence of nosocomial endocarditis and the need for interhospital transfer of complicated cases.

Subtyping of Mycobacterium avium complex (MAC) isolates by thin-layer chromatography--distribution of subtypes from patients with AIDS compared with clinically non-significant isolates

Thin-layer chromatography (TLC) was compared with seroagglutination for subtyping of Mycobacterium avium complex (MAC) bacteria. Seventy-five significant MAC isolates from patients with AIDS were typed by both methods and 36 isolates, judged to be clinically non-significant, were examined by TLC only. Overall, 75% of isolates tested were typable by seroagglutination and 91% by TLC; the results correlated between the two except for minor discrepancies. Serovars 1, 8 and 21 and mixed serovars 1-21 and 1-8-21 were common among isolates from AIDS patients and together represented 83% of isolates compared with only 36% in the non-significant group (odds ratio 8.4; 95% confidence interval 3.4-23.3). This difference remained significant after exclusion of serovar 41 (M. scrofulaceum), which was the commonest isolate (28%) in the non-significant group but was not isolated from patients with AIDS. TLC is useful to supplement seroagglutination for subtyping of MAC. Further study is required to determine whether apparent differences between isolates from patients with AIDS and from other sources reflect differences in virulence or in environmental prevalence of MAC subtypes.

Circulating polymorphonuclear leukocytes from patients with gram-negative bacteremia are not primed for enhanced production of leukotriene B4 or 5-hydroxyeicosatetraenoic acid

The hypothesis was tested that polymorphonuclear leukocytes (PMNL) from patients with gram-negative bacteremia are primed to produce leukotriene B4 (LTB4) or 5-hydroxyeicosatetraenoic acid (5-HETE), in response to concentrations of calcium ionophore A23187, which are substimulatory for control PMNL. PMNL from 11 bacteremic patients and 8 healthy subjects (11 samples) produced similar quantities of LTB4, omega-oxidation products of LTB4, and 5-HETE after incubation with 0.3 and 0.5 microM A23187 for 5 min. At the detection threshold of 0.3 microM A23187, LTB4 was present in PMNL preparations from 9 of 11 patients and 7 of 11 control samples and 5-HETE from the same 9 patients and from 6 controls. There was no correlation between LTB4 or 5-HETE and plasma levels of endotoxin. In this group of patients, priming of PMNL by gram-negative bacteremia did not lead to enhanced production of LTB4, its omega-oxidation products, or 5-HETE when PMNL were challenged with low concentrations of A23187.

The presence of cytoplasmic lipid droplets is not sufficient to account for neutral lipid signals in the 1H MR spectra of neutrophils

Stimulation of human peripheral blood neutrophils with lipopolysaccharide (LPS), arachidonic acid (AA) and oleic acid (OA) resulted in significant increases in cytoplasmic lipid droplets. This phenomenon was also observed in enucleated and degranulated cytoplasts prepared from neutrophils stimulated with LPS. In contrast, only LPS and high concentrations of OA (10 microM) produced an increase in the lipid intensities of the MR spectra of neutrophils as determined by COSY cross peak volume measurements. Lipid intensities in cells stimulated with OA (2.5 microM) and AA (2.5 microM) and phorbol myristate acetate (20 nM) were not elevated. LPS stimulation of resting cytoplasts resulted in increased lipid droplets but not MR lipid intensities. These data suggest that while cytoplasmic lipid droplets may correlate with MR lipid intensity under some circumstances, their presence is not sufficient to account for increased neutral lipid signals.

Pseudomonas aeruginosa bacteraemia. Is pancreatobiliary disease a risk factor?

OBJECTIVE

To review changes in the epidemiology, course, and outcome of bacteraemia caused by Pseudomonas aeruginosa.

DESIGN AND SETTING

A retrospective, descriptive study of consecutive cases of P. aeruginosa bacteraemia occurring at a university teaching hospital.

PATIENTS AND METHODS

Between January 1980 and December 1989, 164 patients were admitted to Westmead Hospital with P. aeruginosa bacteraemia. Patients in whom there was no clinical evidence of sepsis were excluded from analysis leaving a cohort of 152 patients. Hospital records were reviewed and details of demography, clinical features, therapy, and outcome were recorded.

RESULTS

One hundred and fifty-five episodes of P. aeruginosa bacteraemia were recorded at an average rate of 0.39 per 1000 admissions per year. The respiratory and pancreatobiliary tracts were the most common sources of the bacteraemia. Pancreatobiliary disease, independent of an underlying malignancy or immunosuppression, emerged as a previously undescribed risk factor for pseudomonal bacteraemia (incidence of 3.0 episodes per 1000 hospital admissions for patients with this disease). The crude mortality rate was 52%; 35% was attributable to pseudomonal bacteraemia. Factors identified as being independently associated with an increased mortality included hypotension, age of 60 years or older, and the presence of an underlying malignancy. Combination therapy with an antipseudomonal penicillin and an aminoglycoside confers a significant survival advantage independent of underlying neutropenia.

CONCLUSIONS

Bacteraemia caused by P. aeruginosa remains an important cause of morbidity and mortality. Pancreatobiliary disease represents a new risk factor for P. aeruginosa bacteraemia, independent of an underlying malignancy or immunosuppression. It may be prudent to consider P. aeruginosa as a cause of sepsis in these circumstances, especially if there has been instrumentation of the biliary tree. Hypotension, age of 60 years or older, and the presence of an underlying malignancy were independently associated with significantly increased mortality. Appropriate antibiotic therapy consisting of an antipseudomonal beta-lactam in addition to an aminoglycoside resulted in a significant decrease in mortality compared with the use of an aminoglycoside alone, not only in the study population as a whole, but also in patients without neutropenia.

Proton magnetic resonance spectroscopy of polymorphonuclear leukocytes from patients with serious bacterial infections

Triacylglycerols in human neutrophils exposed to proinflammatory stimuli generate a high-resolution proton magnetic resonance (1H MR) spectrum. Lipid cross-peak F volumes in neutrophils from patients with inflammatory conditions were measured. Values in patients hospitalized with localized infections (14.4 +/- 9.0; mean +/- SD) or bacteremia (19.3 +/- 9.7) were significantly higher than in patients with noninflammatory conditions (6.2 +/- 5.3) and healthy controls (2.0 +/- 3.0; P < .001). The positive predictive value of F volumes > 10 was 93% for all infection; the negative predictive value of volumes < or = 10 was 68% for all infection and 92% for bacteremia. Plasma lipopolysaccharide (LPS) concentrations were highest in bacteremic patients but did not correlate with levels of tumor necrosis factor-alpha (TNF alpha) or interleukin-6. In vitro, LPS increased F volumes of control neutrophils from 2.0 +/- 3.0 to 37.2 +/- 6.7 (P < .001); TNF alpha had no effect. F volumes in 1H MR spectra may be useful clinically to discriminate between serious bacterial infection and other inflammatory conditions. TNF alpha is not the stimulus for generation of lipid spectra in vivo.