A study of the anaerobic bacterial flora of the female genital tract in health and disease

Semi-quantitative and qualitative bacterial assessment of the vaginal and cervical flora of a total of 202 women was carried out over a period of six months to determine the bacterial flora in three groups of women and changes caused by prior use of antibiotics. The number was made up of 32 healthy volunteers, 80 women with gynaecological problems and 90 women with gynaecological infections who had had antibiotic treatment prior to this study. Standard methods were used for the investigations. Five main genera of anaerobic bacteria were isolated from all patients. They included, the Bacteroides spp., Prevotella spp., Porphyromonas spp., Peptostreptococcus spp. and Clostridium spp. Five non-sporing gram negative anaerobic bacteria constituted the bulk of the flora including Prevotella bivia, P. disiens, P. melanogenica, P. asaccharolytica and B. fragilis. The predominant flora was P. bivia occurring in 61 pc of cervical swab specimens of the 80 women with proven gynaecological infections who had not used antibiotics and accounting for 27 pc of the total number of Gram-negative anaerobic bacteria isolated. Escherichia coli and Staphylococcus epidermidis were the most frequently encountered aerobic bacteria. The semi-quantitative counts of the different bacterial species in the patient group were significantly higher than in the control group of healthy individuals (p < 0,025). Similarly, prior antibiotic administration significantly reduced the population and quantitative count of the anaerobic bacteria.     

Characteristics of fauces microflora in children treated in intensive care units]

Characteristic features of fauces aerobic microflora in children treated in intensive care units (ICU) were analysed. For comparison fauces microflora in children outpatients and in children patients from general surgical units was investigated. A retrospective analysis of all the smears without exception for 2 years (a total of 2120) revealed a direct dependence of the changes in the fauces microflora composition on the patient condition and the antibiotic load. It was shown that the fauces indigenic microflora in ICU patients was more often replaced by enterococci, gramnegative enteric bacteria and nonfermenting bacteria which are not usual under the normal conditions. The flora in such cases was represented by monoculture. Thus, microorganisms natural for the fauces i.e. Haemophilus influenzae and Neisseria spp. were not practically detected in the fauces of the ICU patients (0.5 and 0.4 per cent, respectively). Grampositive cocci in the children of the surgical units and in the outpatients included alpha-hemolytic streptococci in association with beta-hemolytic or nonhemolytic streptococci. No such bacteria were isolated from the ICU newborns. The associations of gramnegative organisms from the ICU patients included 40 variants. Seventy-eight association variants of Pseudomonas aeruginosa were mainly represented by the combinations with Serratia spp. and Klebsiella spp. as well as with coagulase negative staphylococci or enterococci, especially in the ICU newborns. The results of the study demonstrated that the target-aimed antibiotic therapy providing eradication of P.aeruginosa in the ICU patients was not always justified because of possible superinfection practically due to any organism from the association. Massive antibiotic therapy with pressing on gramnegative flora in the ICU patients induced selective contamination of the mucosa by polyresistant enterococci thus increasing their potential role in the development of hospital infections.     

Bacteriological study of oral open abscesses

Although studies of bacteriology of closed oral abscesses have been extensively done, there are few studies on microorganisms involving open oral abscesses. We examined bacteriologically three open abscesses with precaution against bacterial contamination with oral normal flora and saliva, when sampling. The specimens were subjected to aerobic and anaerobic cultures within 2 hours after sampling. All three cases were infected with 5 to 14 species of aerobic and anaerobic bacteria; Streptococcus spp., Prevotella intermedia and other Prevotella spp. were predominant in all three cases. All six Prevotella spp. isolated were beta-lactamase producers, being resistant to beta-lactam antibiotics. These results emphasize the importance of prompt anaerobic culture for the bacteriological study of open oral abscess and the significance of nitrocefin test to detect beta-lactamase produced by oral isolates, especially Prevotella spp.     

Anaerobes in genitourinary infections in men

Urethral and sub-preputial swabs from 150 men were examined. There was a strong association between the isolation of anaerobic bacteria, particularly Bacteroides spp, and a clinical diagnosis of balanoposthitis, non-specific urethritis (NSU), or both. Aerobic bacteria formed the predominant flora in 28 healthy controls whereas anaerobes were predominant in specimens from 79 patients with balanoposthitis, from 24 with NSU, and from 19 with both. Bacteroides spp were the commonest isolates in all patient groups; B asaccharolyticus, B melaninogenicus ss intermedius, B ureolyticus, and B bivius were the most common species. The results obtained with the two swabs were identical except that Gardnerella vaginalis was isolated from the urethral swab only in five patients.     

Microbiology of common infections in the upper respiratory tract

The management of upper respiratory tract infections has become more difficult because of the recent increase in the number of penicillin-resistant organisms. The bacteria that predominate in otitis media and sinusitis can resist penicillin through the production of the enzyme beta-lactamase (Haemophilus influenzae and Moraxella catarrhalis in acute infections and Staphylococcus aureus and Prevotella and Fusobacteria spp in chronic infections) or through changes in penicillin-binding sites (Streptococcus pneumoniae). beta-lactamase-producing bacteria can express their pathogenicity directly through their ability to cause infections and indirectly by production of the enzyme, thus protecting penicillin-susceptible pathogens from penicillins. This phenomenon may explain penicillin's failure in the treatment of Group A beta-hemolytic streptococcal (GABHS) tonsillitis. An additional cause for penicillin failure is the absence among the normal tonsillar bacterial flora of streptococcal species that are capable of interfering with the growth of GABHS. Proper use of antimicrobial therapy, including those therapies that are effective against penicillin-resistant bacteria, is the cornerstone of management of upper respiratory tract infections.     

The relationship between the quantity of heavy metal and PAHs in fly ash

Several species of the genus Haemophilus are well known etiological agents of pneumonia, meningitis, conjunctivitis, epiglottitis and chancroid. However, identification and speciation of Haemophilus is both time consuming and labor intensive. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI/TOF-MS) has been used by several investigators to profile proteins from intact and disrupted bacteria; consequently, MALDI/TOF-MS has emerged as a powerful tool in diagnostic bacteriology. This paper reports the use of MALDI/TOF-MS as a technique for the rapid identification and speciation of Haemophilus. This technique was used to not only identify the pathogen, H. ducreyi, but also to determine strain differences from different isolates. Mass spectral 'fingerprints' were obtained which permitted the rapid speciation of not only pathogenic forms of Haemophilus, but also those bacteria which are normally regarded as non-pathogenic and members of the normal flora. MALDI/TOF mass spectra can be acquired in 10 min, allowing the identification of Haemophilus spp. within 24 h rather than the 48 h or more needed for traditional bacteriological methods. In addition, these are the first mass spectral fingerprints available in the literature for many of these organisms.     

Heparan sulfate staining of the glomerular basement membrane in relation to circulating anti-DNA and anti-heparan sulfate reactivity: a longitudinal study in NZB/W F1 mice

BACKGROUND: Pyroglyphid mites are considered a major cause of house dust allergy. The occurrence and possible pathogenic role of other biologic components of house dust, in particular bacteria, has received less attention. OBJECTIVE: The aim of this study was to examine bacteria present in the samples of house dust from beds, in comparison to fungi and mites recovery. METHODS: Samples of bed dust were collected from 40 homes in Upper Silesia (Poland). Of these, 19 came from the homes of people with asthma caused by house dust and 21 from the homes of people without allergy. The concentrations of bacteria, fungi, mites, and endotoxin and species composition of microflora and acarofauna were determined. RESULTS: The overall mean concentrations of mesophilic bacteria, thermophilic bacteria and fungi, including yeasts, were, respectively, 1.6 x 10(6), 1.7 x 10(3), and 1.6 x 10(4) CFU/g. Samples contained an average of 8.4 mites/g and the ten samples assayed for bacterial endotoxin averaged 80.4 ng/mg. A total of 55 species of bacteria, 40 of fungi and 13 of mites were found. Gram-positive cocci (mostly Staphylococcus spp.) were the predominant mesophilic bacteria, followed by corynebacteria and Bacillus spp. Thermophilic bacteria were represented only by actinomycetes, with Thermoactinomyces vulgaris predominant. The most numerous fungi were Penicillium spp. and Aspergillus spp. followed by yeasts. The most abundant mites were Dermatophagoides spp. which formed > 85% of the total count. There were no significant differences between the homes of allergic and nonallergic people in the concentrations of total bacteria, fungi, and mites. Bacillus, Aspergillus and total filamentous fungi (molds), but not yeasts, were significantly more numerous in the homes of people with asthma caused by house dust. CONCLUSION: The results suggest that some species of bacteria and filamentous fungi should be considered potential causes of house dust allergy.     

Metronidazole. A therapeutic review and update

The nitroimidazole antibiotic metronidazole has a limited spectrum of activity that encompasses various protozoans and most Gram-negative and Gram-positive anaerobic bacteria. Metronidazole has activity against protozoans like Entamoeba histolytica, Giardia lamblia and Trichomonas vaginalis, for which the drug was first approved as an effective treatment. Anaerobic bacteria which are typically sensitive are primarily Gram-negative anaerobes belonging to the Bacteroides and Fusobacterium spp. Gram-positive anaerobes such as peptostreptococci and Clostridia spp. are likely to test sensitive to metronidazole, but resistant isolates are probably encountered with greater frequency than with the Gram-negative anaerobes. Gardnerella vaginalis is a pleomorphic Gram-variable bacterial bacillus that is also susceptible to metronidazole. Helicobacter pylori has been strongly associated with gastritis and duodenal ulcers. Classic regimens for eradicating this pathogen have included metronidazole, usually with acid suppression medication plus bismuth and amoxicillin. The activity of metronidazole against anaerobic bowel flora has been used for prophylaxis and treatment of patients with Crohn's disease who might develop an infectious complication. Treatment of Clostridium difficile-induced pseudomembraneous colitis has usually been with oral metronidazole or vancomycin, but the lower cost and similar efficacy of metronidazole, coupled with the increased concern about imprudent use of vancomycin leading to increased resistance in enterococci, have made metronidazole the preferred agent here. Metronidazole has played an important role in anaerobic-related infections. Advantages to using metronidazole are the percentage of sensitive Gram-negative anaerobes, its availability as oral and intravenous dosage forms, its rapid bacterial killing, its good tissue penetration, its considerably lower chance of inducing C. difficile colitis, and expense. Metronidazole has notable effectiveness in treating anaerobic brain abscesses. Metronidazole is a cost-effective agent due to its low acquisition cost, its pharmacokinetics and pharmacodynamics, an acceptable adverse effect profile, and its undiminished antimicrobial activity. While its role as part of a therapeutic regimen for treating mixed aerobic/anaerobic infections has been reduced by newer, more expensive combination therapies, these new combinations have not been shown to have any therapeutic advantage over metronidazole. Although the use of metronidazole on a global scale has been curtailed by newer agents for various infections, metronidazole still has a role for these and other therapeutic uses. Many clinicians still consider metronidazole to be the 'gold standard' antibiotic against which all other antibiotics with anaerobic activity should be compared.     

Expression pattern and cellular distribution of the murine homologue of AF10

The microbiologists use the term corynebacteria to describe aerobically growing, asporogenous, irregularly sharped gram-positive rods. They comprise strictly aerobic bacteria isolated from environment as well as preferentially anaerobic bacteria found in clinical specimens. A large part of these bacteria is considered as commensal of skin and mucous membranes. This group of organisms has recently been subjected to considerable taxonomic revisions, which have resulted in the proposal of several new species, many of them representing previous Centers for Diseases Control coryneform groups. Moreover, recent investigations demonstrated the existence of a pathogenic role for some of them. These bacteria comprise well-known pathogens such as C. diphtheriae responsible for diphtheria, Actinomyces spp. responsible for actinomycosis and Arcanobacterium haemolyticum recovered from pharyngitis, but other corynebacteria were related to particular infections. For example, the lipophilic and antibiotics multiresistant species Corynebacterium urealyticum and C. jeikeium were found to be responsible for urinary tract infections and septicemias, respectively. The recently described species Turicella otitidis was found to be implicated in otitis media and C. seminale were recovered from genital specimens of male patients. Implantation of material devices, use of broad-spectrum antibiotics led to an increase of sepsis due to the species C. jeikeium and C. amycolatum. Many of the new Actinomyces species grow well under aerobic conditions and are often implicated in various abscesses. Moreover an increase of immunocompromised patients led to the development of infections due to the aerobic actinomycete Rhodococcus equi. The association of some corynebacteria with particular diseases should prompt the microbiologist to identify these bacteria when they are encountered in a pathogenic situation. Identification of the major part of corynebacteria isolated from clinical specimens can now be achieved by using recent schemes.     

The effect of biocides on the microflora of soils and their degradation. II. Correlations between a changed population of micro-organisms and the degradation of straw (author's transl)

Fungi are of precedent importance for the decomposition of straw in comparison with bacteria and actinomycetes. Several genera and species are able to replace one another. For the fungi, by biocides easier reduced than other kinds of organisms, an inhibition of the decomposition of straw by application of fungicides is possible. An unrestricted or promoted flora of bacteria is not able to replace a restricted flora of fungi. The decomposition of straw cannot be stopped completely. Certain types of fungi locate in higher quantities as a result of the elimination of the competition by bacteria and in dependence on the used antibiotic. Then the special intensity of the decomposition of straw depends on the cellulase-activity of the in each case located fungi. In order to stop the decomposition of straw completely it is necessary to inhibit both the physiologically active bacteria (pseudomonads and bacteria) and the fungi for a longer period of time. Combinations of bactericides and fungicides can bring about synergistic decomposition retarding effects. A persistent stimulation of the straw-decomposition by application of active substances was not successful.     

Microbiology of liver and spleen abscesses

To study the aerobic and anaerobic microbiology of liver and spleen abscesses and correlate the results with predisposing factors, potential causes and routes of infection, clinical and laboratory data of 48 patients with liver abscesses and 29 with spleen abscesses treated between 1970 and 1990 were reviewed retrospectively. In liver abscesses, a total of 116 isolates (2.4 isolates/specimen) was obtained; 43 were aerobic and facultative species (0.9 isolates/specimen) and 73 were anaerobic species or microaerophilic streptococci (1.5 isolates/specimen). Aerobic bacteria only were isolated from 12 (25%) abscesses, anaerobic bacteria only from eight (17%), and mixed aerobic and anaerobic bacteria from 28 (58%); polymicrobial infection was present in 38 (79%). The predominant aerobic and facultative isolates were Escherichia coli (11 isolates), Streptococcus group D (8), Klebsiella pneumoniae (5) and Staphylococcus aureus (4). The predominant anaerobes were Peptostreptococcus spp. (18 isolates), Bacteroides spp. (13), Fusobacterium spp. (10), Clostridium spp. (10) and Prevotella spp. (4). There were 12 isolates of micro-aerophilic streptococci. S. aureus and beta-haemolytic streptococci were associated with trauma; Streptococcus group D, K. pneumoniae and Clostridium spp. with biliary disease; and Bacteroides spp. and Clostridium spp. with colonic disease. In splenic abscesses, a total of 56 isolates (1.9 isolates/specimen) was obtained; 23 were aerobic and facultative species (0.8 isolates/specimen), 31 were anaerobic species or micro-aerophilic streptococci (1.1 isolates/specimen) and two were Candida albicans. Aerobic bacteria only were isolated from nine (31%) abscesses, anaerobic bacteria from eight (28%), mixed aerobic and anaerobic bacteria from 10 (34%) and C. albicans in two (7%); polymicrobial infection was present in 16 (55%). The predominant aerobic and facultative isolates were E. coli (5 isolates), Proteus mirabilis (3), Streptococcus group D (3), K. pneumoniae (3) and S. aureus (4). The predominant anaerobes were Peptostreptococcus spp. (11 isolates), Bacteroides spp. (5), Fusobacterium spp. (3) and Clostridium spp. (3). S. aureus, K. pneumoniae and Streptococcus group D were associated with endocarditis, E. coli with urinary tract and abdominal infection, Bacteroides spp. and Clostridium spp. with abdominal infection and Fusobacterium spp. with respiratory infection.     

Demodex folliculorum and topical treatment: acaricidal action evaluated by standardized skin surface biopsy

Resistance to third-generation cephalosporins mediated by beta-lactamases is an increasing problem for clinical therapeutics. A wide range of Enterobacteriaceae produce these AmpC enzymes (Bush-Jacoby-Medeiros group 1), including Enterobacter spp., Citrobacter freundii, Morganella morganii, Providencia spp., and Serratia marcescens. Resistance via this mechanism has been shown to be statistically correlated with the use of some third-generation cephalosporins, and the infections caused by these stably derepressed enzyme-producing species seem to occur most frequently in the seriously ill. More recently the genes encoding this enzyme have been documented on plasmids capable of transfer into other species such as Klebsiella pneumoniae. Fourth-generation cephalosporins, with stability and low affinity for the Amp C beta-lactamases and the ability to penetrate rapidly into the periplasmic space of Gram-negative organisms, offer a viable alternative in the treatment of these infections or as empiric regimens. Furthermore, these compounds (example: cefpirome) possess greater potency against the frequently occurring Gram-positive cocci such as oxacillin-susceptible staphylococci and the streptococci (including some penicillin-resistant strains) as compared to previously used anti-pseudomonal cephalosporias, ceftazidime.     

The role of seafood in foodborne diseases in the United States of America

In the United States of America, seafood ranked third on the list of products which caused foodborne disease between 1983 and 1992. Outbreaks connected with fish vectors were caused by scombroid, ciguatoxin, bacteria and unknown agents; in shellfish, unknown agents, paralytic shellfish poisoning, Vibrio spp. and other bacteria, followed by hepatitis A virus, were responsible for the outbreaks. At least ten genera of bacterial pathogens have been implicated in seafood-borne diseases. Over the past twenty-five years, bacterial pathogens associated with faecal contamination have represented only 4% of the shellfish-associated outbreaks, while naturally-occurring bacteria accounted for 20% of shellfish-related illnesses and 99% of the deaths. Most of these indigenous bacteria fall into the family Vibrionaceae which includes the genera Vibrio, Aeromonas and Plesiomonas. In general, Vibrio spp. are not associated with faecal contamination and therefore faecal indicators do not correlate with the presence of Vibrio. Viruses are the most significant cause of shellfish-associated disease: in New York State, for example, 33% and 62% of 196 outbreaks between 1981 and 1992 were caused by Norwalk virus and gastrointestinal viruses (small round structured viruses), respectively. In addition, several illnesses are a result of toxic algal blooms, the growth of naturally occurring bacteria and diatoms causing neurotoxic shellfish poisoning, paralytic shellfish poisoning, diarrhoetic shellfish poisoning, amnesic shellfish poisoning and ciguatera. Current estimates place the annual number of ciguatera cases at 20,000 world-wide. Scombroid poisoning is the most significant cause of illness associated with seafood. Scombrotoxin is of bacterial origin and halophilic Vibrio spp. causing high histamine levels are implicated as the source. Scombroid poisoning is geographically diverse and many species have been implicated, namely: tuna, mahi-mahi, bluefish, sardines, mackerel, amberjack and abalone. Temperature abuse has been cited as a major cause of scombroid poisoning. For routine work, the use of faecal indicators to predict the relative level of faecal contamination should not be disposed of. However, the main source of seafood illness is due to species which are not predicted by these organisms. In order to protect public health, routine surveillance using new pathogen-specific techniques such as polymerase chain reaction should be used. This, in combination with risk assessment methods and hazard analysis and critical control points, will begin to address the need for improvement in the safety of seafood.     

Multiple lungs tumors found 17 years after hysterectomy--a case of benign metastasizing leiomyoma

Fifty-five samples of pus were collected from 51 acute, non-perforated, two spontaneously ruptured and two recurrent peritonsillar abscesses (35 males and 18 females; median age 18 years) and analysed regarding (i) aerobic and anaerobic bacteria (standard culturing), (ii) morphology of bacteria and inflammatory cells (direct microscopy of acridine orange-stained material), and (iii) the percentage of bacteria coated with immunoglobulins IgG, secretory IgA (SIgA) and IgM and complement cleavage product C3b (immunofluorescence assay). Seventy-one per cent of the abscesses harboured a mixed bacterial flora of various aerobes and anaerobes. In none of the cases with a single bacterial species (27 per cent) could immunoglobulin- or complement-coated bacteria be found. In abscesses with a mixed flora, 18 per cent harboured IgG-coated, 15 per cent SIgA-coated, five per cent IgM-coated and five per cent C3b-coated bacteria, respectively. All pus samples contained inflammatory cells in abundance but they were mostly deformed and only occasionally could intracellular bacteria be recognized. Insufficient immunoglobulin-coating of bacteria might be an important aetiopathogenic factor in the development of a peritonsillar abscess. Bactericide in the abscesses is accomplished chiefly by protective mechanisms not dependent on antigen recognition by antibodies.     

Klebsiella spp. as nosocomial pathogens: epidemiology, taxonomy, typing methods, and pathogenicity factors

Bacteria belonging to the genus Klebsiella frequently cause human nosocomial infections. In particular, the medically most important Klebsiella species, Klebsiella pneumoniae, accounts for a significant proportion of hospital-acquired urinary tract infections, pneumonia, septicemias, and soft tissue infections. The principal pathogenic reservoirs for transmission of Klebsiella are the gastrointestinal tract and the hands of hospital personnel. Because of their ability to spread rapidly in the hospital environment, these bacteria tend to cause nosocomial outbreaks. Hospital outbreaks of multidrug-resistant Klebsiella spp., especially those in neonatal wards, are often caused by new types of strains, the so-called extended-spectrum-beta-lactamase (ESBL) producers. The incidence of ESBL-producing strains among clinical Klebsiella isolates has been steadily increasing over the past years. The resulting limitations on the therapeutic options demand new measures for the management of Klebsiella hospital infections. While the different typing methods are useful epidemiological tools for infection control, recent findings about Klebsiella virulence factors have provided new insights into the pathogenic strategies of these bacteria. Klebsiella pathogenicity factors such as capsules or lipopolysaccharides are presently considered to be promising candidates for vaccination efforts that may serve as immunological infection control measures.     

Molecular changes in Entamoeba histolytica in response to bacteria

Entamoeba histolytica, the protozoan parasite, is the causative agent of amoebiasis. The degree of virulence, as inferred from invasiveness, of potentially pathogenic strains may be regulated by both host and parasite factors that determine the gut environment. One such factor that plays an important role is the bacterial flora in the gut. Previous studies have clearly shown that bacterial flora is an important determinant of virulence in E. histolytica. However, the exact nature of changes induced in E. histolytica in response to bacteria and their role in virulence is not clear. In this study the levels of a number of molecules potentially important in virulence mechanisms were determined in E. histolytica cells grown with and without normal human bacterial flora, using enzyme-linked immunosorbent assay. Significant changes were observed only after the E. histolytica cells had been adapted to grow with bacterial flora for a number of generations, and not in short term culture.     

Blood viscosity disorders as an etiopathological factor in sudden deafness]

This study was conducted to determine the relationship between lactobacilli and bacterial species associated with bacterial vaginosis in pregnancy and the prevalence of H2O2-producing and non-producing strains of lactobacilli in pregnant women whose vaginal flora had already been analysed. Information was available for 174 pregnant women whose vaginal flora had been evaluated previously by examining gram-stained vaginal smears: 50 had grade III flora (bacterial vaginosis). 50 grade II flora, 41 flora graded as abnormal which then reverted to grade I (revertants) and 33 normal flora (controls). Lactobacilli were isolated from 19 of 50 women whose vaginal flora was grossly abnormal culturally and categorised as grade III by Gram staining. In 6 of these 50 women lactobacilli were isolated in large numbers, i.e. 10(5)-10(6) cfu/ml. H2O2-producing strains of lactobacilli were isolated from 11 of 12 women with grade III flora who were randomly selected from this group. Thus, in those 11 women it appears that H2O2-producing lactobacilli had not protected them from developing bacterial vaginosis. Bacterial species associated with vaginosis were isolated in high numbers from a large proportion of women in the revertant and grade II groups in association with high counts of lactobacilli. Thus, in some women it is possible that a change to an abnormal flora could occur before the complete disappearance of lactobacilli. It is concluded that bacterial vaginosis may develop in some women despite the presence of H2O2-producing strains of lactobacilli and that other factors, as yet unidentified, might be conducive to the appearance of abnormal bacterial flora with progression to vaginosis.     

Applications of electron paramagnetic resonance spectroscopy to study interactions of iron proteins in cells with nitric oxide

Nitric oxide and species derived from it have a wide range of biological functions. Some applications of electron paramagnetic resonance (EPR) spectroscopy are reviewed, for observing nitrosyl species in biological systems. Nitrite has long been used as a food preservative owing to its bacteriostatic effect on spoilage bacteria. Nitrosyl complexes such as sodium nitroprusside, which are added experimentally as NO-generators, themselves produce paramagnetic nitrosyl species, which may be seen by EPR. We have used this to observe the effects of nitroprusside on clostridial cells. After growth in the presence of sublethal concentrations of nitroprusside, the cells show they have been converted into other, presumably less toxic, nitrosyl complexes such as (RS)2Fe(NO)2. Nitric oxide is cytotoxic, partly due to its effects on mitochondria. This is exploited in the destruction of cancer cells by the immune system. The targets include iron-sulfur proteins. It appears that species derived from nitric oxide such as peroxynitrite may be responsible. Addition of peroxynitrite to mitochondria led to depletion of the EPR-detectable iron-sulfur clusters. Paramagnetic complexes are formed in vivo from hemoglobin, in conditions such as experimental endotoxic shock. This has been used to follow the course of production of NO by macrophages. We have examined the effects of suppression of NO synthase using biopterin antagonists. Another method is to use an injected NO-trapping agent, Fe-diethyldithiocarbamate (Fe-DETC) to detect accumulated NO by EPR. In this way we have observed the effects of depletion of serum arginine by arginase. In brains from victims of Parkinson's disease, a nitrosyl species, identified as nitrosyl hemoglobin, has been observed in substantia nigra. This is an indication for the involvement of nitric oxide or a derived species in the damage to this organ.