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Laboratory tests that can be helpful in guiding antimicrobial therapy include antimicrobial susceptibility testing, determination of bacterial beta-lactamase production, assay of serum inhibitory and bactericidal activity, and assay of specific antibiotic levels in serum. Susceptibility studies should be performed on any microorganism that is isolated from normally sterile body fluid in the presence of clinical evidence of infection. The standardized disk test provides results that should be comparable from laboratory to laboratory. Dilution methods, however, allow determination of the minimal concentration of an agent which inhibits growth, and this value can be correlated with blood, urine, and other body fluid levels of the antimicrobial agent. Determination of serum bactericidal activity is, in effect, an assay of the activity of antimicrobial-containing serum; it indirectly measures the combined effects of susceptibility of the test organism and serum concentration of the antimicrobial agent. Accurate measurement of serum concentrations of antimicrobial agents may be important when treatment includes agents that have a narrow margin between therapeutic and toxic levels such as the aminoglycosides (especially gentamicin) or in patients with renal failure, who may accumulate unusually high levels of antimicrobial agents normally excreted by the kidneys.

The sera and polymorphonuclear leukocytes (PMNs) of healthy human subjects were tested against several isolates of Bacteroides fragilis. All sera killed most of the fecal isolates, but were active aganist only one of the clinical isolates. The degree of killing was directly related to the serum concentration but was independent of the bacterial inoculum within the range of bacterial concentrations studied. The serum bactericidal activity was heat-labile. Engulfment and killing of B. fragilis by PMNs were demonstrated consistently. The opsonim involved in phagocytosis was also heat liable. Calculations involving log-transformed data permitted the quantitative study of the separate and combined effects of serum and PMNs on bacteria which were killed by serum alone. Whereas serum alone usually killed 0.5 log of serum-sensitive bacteria, the addition of PMNs was usually associated with one log further killing. The studies reported here demonstrate the presence of heat-labile serum factors in normal human sera which killed B. fragilis directly and which promote its phagocytosis and killing by PMNs. These observations provide a foundation for investigations into host defense mechanisms against anaerobes.

In this placebo-paired, double-blind study, 13 of 45 schizophrenic patients showed an acute improvement in schizophrenic symptoms following d-amphetamine infusion (20 mg). The 18 patients who worsened tended to have higher CSF 3-methoxy-4-hydroxyphenylglycol levels than did those who improved. d-Amphetamine blood levels and clinical descriptors of schizophrenic subgroups did not differentiate patients who improved from those who worsened; however, patients who improved had been significantly more psychotic before the infusion. Patients who worsened had been more psychotic than those who did not change. The authors suggest that those who did not change. The authors suggest that sensitivity to dopamine stimulation in schizophrenia is state-dependent rather than trait-dependent and that the simple, undirectional hypothesis of schizophrenia needs to be reformulated.

During a 3 1/2 year period anaerobic septic arthritis was diagnosed in 43 patients (46 joints). The hip and knee accounted for 83% of the infected joints. Anaerobic infections complicated elective musculoskeletal surgery in 23 patients, including 21 with total joint arthroplasties. An additional 12 patients developed septic arthritis following surgical treatment of traumatic injuries of an extremity. Gram-positive cocci were the anaerobes most commonly found in these two groups of surgical patients, accounting for 64% of the isolates; Peptococcus magnus was the most common organism. In contrast, gram-negative bacilli (especially Bacteroides fragilis) comprised 63% of the anaerobes isolated from eight patients with chronic debilitating diseases who had not had prior surgery. Only anaerobes were recovered from approximately half of all the patients with septic arthritis while mixed aerobic-anaerobic cultures accounted for the remainder. Adequate treatment required aggressive surgery and prolonged (minimum of three weeks) antimicrobial therapy. Infected total joint arthroplasties had to be removed. Loss of joint function occurred in six patients with posttraumatic infections when surgery was delayed or antimicrobials were inadequate. Outcome was poorest in the patients with chronic debilitating diseases, four of whom died.

The survival of six species of anaerobic bacteria was studied in simple or commercially available diluents. Bacteroides fragilis and Fusobacterium nucleatum showed excellent survival in all diluents including distilled water. Fusobacterium mortiferum survived well in all diluents except water and water supplemented with 0.1% gelatain. Clostridium perfringens survived best in phosphate-buffered saline with gelatin. Peptococcus asaccharolyticus required gelatin added to the basic diluent, and Streptococcus intermedius showed excellent survival only in minimal essential medium with gelatin. These diluents could provide effective and economical alternatives to more complex and costly diluents often used in work with anaerobic bacteria.

A case of giant cell arteritis is reported that was detected by bone marrow biopsy. The histopathologic features of the bone marrow lesion included an enlarged artery, whose wall showed intimal thickening, fibrinoid necrosis, destruction of the internal elastic lamina, and multinucleated giant cells. The demonstration of involvement of bone marrow vessels by giant cell arteritis reaffirms the systemic nature of the disease. Bone marrow biopsy is not the method of choice for establishment of the diagnosis of giant cell arteritis, but it may lead to the diagnosis in rare instances.

Simple pour plate and spectrophotometric techniques for the evaluation of growth curves of several anaerobic bacteria on solid media are described. Three basic patterns of anaerobic growth were observed. The curves obtained were very reproducible when studied on separate occasions. The curves obtained by spectrophotometric measurement were comparable to those obtained by the pour plate method, especially when a large bacterial inoculum was used. Limitations in the interpretation of the results are discussed. The methods and principles reported could provide the basis for the determination of bacterial growth on solid media using other organisms and different experimental conditions.

Anaerobic isolates were tested for bacterial inhibitory activity. Of 144 isolates, 102 were from oropharynegeal washings, and 42 were from clinical specimens. Thirteen facultative bacterial species (seven members of the Enterobacteriaceae and six species of gram-positive cocci) were used as indicators of inhibition. Eleven anaerobic species were isolated from oral secretions. All isolates of Bacteroides melaninogenicus, the most commonly recovered species, consistently inhibited several species of indicator bacteria. Bacteroides fragilis, Bacteroides oralis, and Peptostreptococcus anaerobius had unprecictable inhibitory activity, whereas most of the other oral anaerobes were noninhibitory. The 42 clinical species were generally noninhibitory.

In a new method of anaerobic culture, a transparent, gas-impermeable bag is used and the anaerobic environment is established with copper sulfate-saturated steel wool. An Alka-Seltzer tablet generates carbon dioxide. The agar plate surface can be inspected through the bag at any time without interrupting the anaerobic atmosphere or disturbing other specimens. Methylene blue indicator strips are completely reduced by 4 h after the bag is set up and have remained reduced for as long as 3 weeks. Growth of 16 different stock culture anaerobes was generally equivalent by the bag and GasPak jar methods. Yield and growth of anaerobic isolates also were equivalent with 7 of 10 clinical specimens; from the other 3 specimens, 13 isolates were recovered, 5 by both the bag and jar methods and the rest by one method or the other. No consistent differences were found between the anaerobic bag and GasPak jar methods in the yield of anaerobes from clinical specimens. Early growth (24 h of incubation) of anaerobes from one specimen was detected with the bag method.

Eighty-four anaerobic fecal isolates obtained from five healthy volunteers were tested for their ability to inhibit in vitro growth of eight species of Enterobacteriaceae, four species of faculative gram-positive cocci, and Pseudomonas aeruginosa. Forty-nine of the 84 anaerobic isolates (58%) inhibited the growth of at least one indicator bacterium. Isolates of Bacteroides and Bifidobacterium spp. were most consistently inhibitory. Anaerobic cocci and clostridia were infrequently inhibitory; eubacteria showed no inhibitory activity. Serratia marcescens was the indicator most often inhibited; 54% of all anaerobic isolates tested, all of nine Bifidobacterium isolates and 33 of 43 Bacteroides isolates inhibited this organism. No anaerobes inhibited the growth of Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Citrobacter freundii, Citrobacter diversus or Streptococcus faecalis.

d-Amphetamine (20 mg) was administered intravenously in a double-blind design to 17 schizophrenic patients with and without concurrent 3-week lithium carbonate pretreatment to evaluate the lithium attenuation of d-amphetamine effects which we had observed in affective disorder patients. Lithium significantly attenuated the acute d-amphetamine-induced changes in an activation-euphoria cluster and in the mannerisms and posturing item of the Brief Psychiatric Rating Scale. Because the psychosis-increasing effects of d-amphetamine were not significantly decreased, it is conceivable that the d-amphetamine-induced changes in activation and euphoria and in psychosis are regulated by different dopamine mechanisms. The small clinical effects seen at 3 weeks of lithium treatment in schizophrenic patients could be mediated by dopamine.

Results of antimicrobial susceptibility testing of anaerobic bacteria isolated at the Mayo Clinic were reviewed for 1982 through 1987 and compared with a previous survey during 1977 through 1981 at this institution. Between the earlier and the later period, clindamycin resistance increased in the Bacteroides fragilis group (from 4% of isolates to 8%). We noted continuing penicillin resistance among Bacteroides species other than B. fragilis and rare penicillin resistance among Fusobacterium organisms, with four isolates during the 1982 through 1987 period being beta-lactamase producers. The high levels of resistance to some agents seen in certain Clostridium species in 1977 through 1981 were not as great in the current survey. No major changes were noted in the susceptibilities of C. perfringens, anaerobic non-spore-forming gram-positive bacilli, and anaerobic gram-positive cocci.

Based on specific criteria, tardive dyskinesia was diagnosed in 6 out of 29 young schizophrenic male inpatients. We compared several biochemical parameters in these six dyskinesia patients with those in six matched controls. The patients with dyskinesia had significantly lower platelet monoamine oxidase activity and significantly higher plasma dopamine-beta-hydroxylase activity as compared with the controls, thus confirming our previous findings in a population of elderly female inpatients. The dyskinetic and nondyskinetic groups did not differ from each other in mean whole blood serotonin concentration and mean serum neuroleptic concentration as measured with a radioreceptor binding assay. Possible significance of our results is discussed.

Response to neuroleptic drug treatment in ten chronic schizophrenic patients with enlarged cerebral ventricles was compared with ten similar patients with normal ventricles. The groups were closely matched for age, age at onset of illness, years of illness and hospitalization, drug dosage, and plasma neuroleptic concentration as measured by radioreceptor assay. Response was significantly worse in the patients with enlarged ventricles. This finding supports the notion that ventricular enlargement is clinically relevant in patients with chronic schizophrenia and that patients with this abnormality may have a biologically different illness than similar patients without it.

Tobramycin, a new aminocyclitol antimicrobial agent, was administered parenterally to 28 patients infected with gram-negative bacilli. The dosage was 1.5 mg/kg every 8 hours, except in patients with renal insufficiency in whom the dosage interval was 10 times the serum creatinine in hours. Serum levels after intramuscular administration were 3.9 +/- 1.6 mug/ml and 1.0 +/- 0.7 mug/ml at 2 and 8 hours, respectively. Serum levels after intravenous administration were 4.6 +/- 0.5 mug/ml, 2.3 +/- 0.6 mug/ml, and 0.6 +/- 0.8 mug/ml at 15 minutes, 1 hour, and 8 hours, respectively. Clinical isolates included 21 of Pseudomonas aeruginosa, 6 of Klebsiella pneumoniae, 2 of Serratia marcescens, and also isolates of E. coli, Proteus mirabilis, and Enterobacter. The minimum inhibitory concentrations (MICs) of tobramycin, gentamicin, sisomicin, and amikacin were determined for these organisms. Clinical results included 18 cures, 3 improvements, 2 indeterminates, and 6 failures. Minimal hepatic and renal toxicity was observed.

AnIdent is a new 4-hr system for the identification of anaerobic bacteria that depends upon detection of a unique set of preformed enzymes. A single AnIdent test speciated 76% of 333 anaerobes (89% agreement with a conventional system used at the Mayo Anaerobe Laboratory) without any repeat or supplemental testing (level 1). Additional testing increased the identification rate to 93% (level 2). We conclude that AnIdent is a reliable method for identifying clinically significant anaerobes which only occasionally requires the use of a small number of simple supplemental tests and avoids the necessity for performing gas-liquid chromatography.

The value of a routine 48-h anaerobic subculture of blood cultures was assessed in our laboratory over a 4-month period. Excluding presumed contaminants, anaerobes represented 51 (6.9%) of the total number of 734 positive cultures. Sixteen isolates (all Bacteroides) from six patients were detected by the anaerobic subculture. All but one of these were also detected macroscopically. Excluding the one isolate, the routine anaerobic subculture hastened the identification of anaerobic organisms by only 1 day in two patients. We conclude that a routine anaerobic subculture is not indicated for the detection of anaerobic bacteremia.

The peripheral interactions of amphetamine with antipsychotic agents may elucidate some central mechanisms by which these drugs affect the behavioral responses to amphetamine. The authors studied the effects of intravenous amphetamine on plasma levels of norepinephrine (NE), dopamine-beta-hydroxylase (DBH), pulse rate, and blood pressure in schizophrenic patients. Amphetamine increased plasma NE, pulse rate, and blood pressure without significantly changing plasma DBH. DBH activity was similar in drug-free schizophrenic and normal subjects. Neither pimozide nor lithium altered these amphetamine effects nor changed any of the cardiovascular parameters measured in the drug-free subjects. Pimozide and lithium alter behavior and the behavioral effects of amphetamine, but neurotransmitters other than NE may be involved.

Seventy patients with substantiated anaerobic infections were treated parenterally with clindamycin or chloramphenicol in a prospective, double-blind, randomized study. No significant differences in clinical response or toxicity were noted between the two groups of patients.

During a two-year period, 1,892 patients underwent biliary tract surgery at the Mayo Clinic. Both aerobic and anaerobic bile cultures were performed in 371 patients and 253 of these were positive. Anaerobes were isolated from 100 patients, although only twice in pure culture. Only aerobes grew from cultures from 153 patients. One hundred cases of biliary tract infections involving anaerobes and an equal number involving aerobes only were reviewed in order to determine their clinical characteristics. Prominent features of anaerobic bactibilia included (1) a history of complex, multiple, biliary tract surgeries often involving biliary-intestinal anastomoses and common bile duct manipulation, (2) severe symptoms, (3) high incidence of postoperative infectious complications, especially wound infections. Further analysis of anaerobic biliary infections suggested that Bacteroides fragilis was more often associated with serious pathologic conditions of the biliary tract than was Clostridium.

Four methods for detecting beta-lactamase activity in anaerobic bacteria were evaluated and compared to a nitrocefin saturated filter paper test. The methods studied were Cefinase, PADAC, Beta Lactam, and the slide iodometric technique. Fifty anaerobes were tested including species of Bacteroides, Fusobacterium, and Clostridium. The percentages of agreement with the nitrocefin test are: Cefinase 100%, PADAC 96%, slide iodometric 78%, and Beta Lactam 72%. Positive nitrocefin tests have been shown to correlate with a penicillin MIC greater than 0.78 micrograms/ml.

Turbid saline suspensions (0.35 ml, approximately 10(9) organisms) of a strain of beta-lactamase-producing Bacteroides intermedius were injected subcutaneously into the right groin of ICR male mice. Therapeutic intraperitoneal doses of clindamycin, metronidazole, or penicillin were administered 4 hr later, and thereafter at successive 8-hr intervals for a total of 12 doses. Necropsy with culture of the infection site was performed 4 hr after the final dose. None of 10 clindamycin-treated animals and none of 10 metronidazole-treated animals developed abscesses, and all cultures taken from the injection sites were sterile. Eight of 10 (80%) penicillin-treated animals developed subcutaneous abscesses; B. intermedius was recovered in pure cultures from all abscesses at necropsy. Nine of 10 (90%) untreated control animals inoculated with the same beta-lactamase-producing B. intermedius strain developed abscesses, all of which were culture-positive. The data indicate that treatment with clindamycin and metronidazole prevented the formation of subcutaneous abscesses in mice inoculated with a beta-lactamase-producing strain of B. intermedius. On the other hand, penicillin failed to prevent the formation of abscesses, 80% of which grew the inoculated organism.

Platelet monoamine oxidase activity (MAO) was studied serially over time in 16 chronic schizophrenic patients when medication free and then when medicated. Thirteen of the 16 patients had significant decreases in platelet MAO activity following neuroleptic drug treatment. The change in MAO activity was found to be correlated with response to treatment and to dose of medication.

Laboratory tests that can be helpful in guiding antimicrobial therapy include antimicrobial susceptibility testing, determination of bacterial beta-lactamase production, assay of serum inhibitory and bactericidal activity, and assay of specific antibiotic levels in serum. Susceptibility studies should be performed on any microorganism that is isolated from normally sterile body fluid (blood, cerebrospinal fluid, pleural fluid, synovial fluid) in the presence of clinical evidence of infection. The standardized disk test provides results that should be comparable from laboratory to laboratory. Dilution methods, however, allow determination of the minimum concentration of an agent which inhibits growth (MIC), and this value can be correlated with blood, urine, and other body fluid levels of the antimicrobial agent. Determination of serum bactericidal activity is, in effect, an assay of the activity of antimicrobial-containing serum; it indirectly measures the combined effects of susceptibility of the test organism and serum concentration of the antimicrobial agent. Accurate measurement of serum concentrations of antimicrobials may be important when treatment includes agents that have a narrow margin between their therapeutic and their toxic levels such as the aminoglycosides (especially gentamicin) or in patients with renal failure, who may accumulate unusually high levels of antimicrobials normally excreted by the kidneys.

The activity of sulfamethoxazole (SMX), trimethoprim (TMP), and the combination of the two was determined against a variety of anaerobic bacteria. Brucella agar was somewhat inhibitory for SMX and TMP but activity was good and equivalent in Diagnostic Sensitivity Test Agar (Oxoid) and Mueller-Hinton agar and the latter was selected for use in these studies. Agar dilution susceptibility tests showed that 95 of 98 anaerobic isolates were resistant to >/=100 mug of SMX per ml and 85 were resistant to >/=6.25 mug of TMP per ml. "Checkerboard" agar dilution studies of combined activity showed that 66 of 72 isolates were resistant to >/= (100 mug of SMX per ml + 6.25 mug of TMP per ml) and only six isolates were susceptible to the synergistic activity of the combination. The majority of 32 isolates tested by the disk diffusion method were also resistant to SMX and TMP individually and to the combination 25-mug disk. Correlation between agar dilution minimal inhibitory concentration and disk zone size results was in general good for individual agents. Four Bacteroides fragilis isolates were inhibited by the combination 25-mug disk but were resistant to SMX + TMP by agar dilution "checkerboard." This discrepancy may have been due to different incubation periods since disk results also showed resistance when read after 48 h (as is done with agar dilution) rather than the standard 24 h for disk tests. These studies suggest that SMX and TMP, either individually or in combination, are not active against the great majority of anaerobic bacteria.

Moxalactam was administered (20 mg/kg intravenously every 8 hours) as single-drug empiric antimicrobial therapy to 63 patients with bacteremia who were neither neutropenic nor immunosuppressed. Six patients (10%) had microorganisms that were susceptible to moxalactam and resistant to all other antimicrobial agents tested; two patients (3%) had microorganisms that were resistant to moxalactam and other agents tested. Of these 63 patients, 47 (75%) were cured with moxalactam therapy. Nine patients (14%) had breakthrough bacteremia while receiving other antimicrobial therapy and were cured subsequently with moxalactam therapy alone. The two major risk factors for failure of moxalactam therapy were polymicrobial bacteremia and an extrahepatic intra-abdominal source of infection; these two conditions frequently coexisted. Six of nine patients with polymicrobial bacteremia died. Superinfection (one pseudomonal, five enterococcal) was responsible for 6 of the 16 treatment failures. Enterococcal superinfection occurred exclusively among patients who had received relatively prolonged therapy with moxalactam for extrahepatic intra-abdominal infection, especially intraabdominal abscess. These five patients died, and postmortem examination showed that enterococcal superinfection was the major cause of death in all. Mild, reversible adverse reactions associated with use of moxalactam occurred in 14 of the 63 patients (22%). None had clinically overt bleeding. The use of moxalactam alone seems to be safe and effective and a cost-effective alternative empiric antimicrobial therapy for most patients with bacteremia who are not immunosuppressed or neutropenic and who are not at high risk of having Pseudomonas or polymicrobial bacteremia.

The in vitro inhibitory activity of spectinomycin was tested against various anaerobic bacteria. Different results were obtained with different media and with different initial pH's of the media. The highest minimum inhibitory concentrations for Bacteroides fragilis ([Formula: see text] 128 mug/ml) were obtained with the use of Wilkins-Chalgren agar (pH 7.2) and Brucella blood agar (pH 7.0). Brucella blood agar at higher pH's (7.4 and 8.0) and Mueller-Hinton and Diagnostic Sensitivity Test agars produced lower minimum inhibitory concentrations (32 and 64 mug/ml). This same relationship between spectinomycin activity and pH of the medium was, in general, observed with these media and other anaerobes, including isolates of B. melaninogenicus, Fusobacterium, gram-positive cocci, Clostridium perfringens, and C. ramosum. The variable results observed in this study and in two others make it difficult to predict the clinical usefulness of spectinomycin in the treatment of anaerobic infections. It is probably most appropriate to be guided by results obtained with Wilkins-Chalgren agar and the method proposed as a reference to the National Committee for Clinical Laboratory Standards. These results indicate that spectinomycin is not a potent inhibitor of B. fragilis or other clinically significant anaerobes.

Forty-six patients with cholangitis were randomized to receive therapy with mezlocillin sodium (24 patients) or a combination of ampicillin sodium--gentamicin sulfate (22 patients). The biliary concentration of mezlocillin was 112 times higher than that of ampicillin and 778 times higher than that of gentamicin. The ratio of the concentration in serum or bile over the minimum inhibitory concentration against aerobic gram-negative bacilli (therapeutic index) was higher for mezlocillin than for either ampicillin or gentamicin. Twenty (83%) of 24 patients were cured following mezlocillin therapy compared with 9 (41%) of 22 patients after ampicillin-gentamicin therapy. The 3 patients with superinfection were in the ampicillin-gentamicin arm of the study. Fewer toxic or adverse effects occurred in association with mezlocillin treatment than with ampicillin-gentamicin treatment. Mezlocillin therapy was more effective, less toxic, and less expensive than treatment with ampicillin and gentamicin for patients with cholangitis.

Anaerobic septic arthritis and osteomyelitis are more common than previously believed. Recent experience suggests that because of the high morbidity associated with these conditions, a very aggressive surgical and medical treatment program is indicated.

Peptococcus indolicus was isolated from a skin lesion of a sheepherder. A case report is given, and microbiological features of this organism are described.

The authors developed a rapid slide test modification of the iodometric method for detection of penicillinase produced by organisms growing on routine plating media. A loopful of colonies is scraped from the agar surface and emulsified in one drop of an iodine-penicillin solution on a glass slide. Addition of a drop of 0.4% starch solution results in a purple color when penicillinase is not present; a colorless reaction denotes a positive test. The slide test yielded positive results identical to those of a starch agar-plate method with 26 Staphylococcus aureus isolates; a further seven showed comparable negative tests. Penicillinase production was associated with a S. aureus penicillin MIC of greater than or equal to 0.5 micron/ml. All 15 Staphylococcus epidermidis isolates gave negative test results, as did 22 Bacteroides fragilis (MIC greater than or equal to 3.1). Twenty ampicillin-susceptible Haemophilus influenzae were negative by both the slide test and a Levinthal broth method; an additional five resistant (MIC greater than or equal to 10) isolates were positive by both methods. Twenty-eight (penicillin MIC greater than or equal to 0.8) of 50 Bacteroides melaninogenicus were slide test-positive for penicillinase. Two penicillinase-producing strains of Neisseria gonorrhoeae gave positive slide tests, while eight other non-penicillinase-producers were negative.

The present experiments demonstrate high affinity stereospecific binding of the dopaminergic ligand [3H]spiroperidol to rat renal membranes. The binding was saturable, regionally distributed, and showed the same specificity as the caudate [3H]spiroperidol site for displacement by dopaminergic antagonists. Since there is an association between hypertension and abnormalities of renal blood flow, which appears to be regulated in part by dopamine, [3H]spiroperidol binding was measured in kidneys of spontaneously hypertensive rats. In two independent experiments renal cortical [3H]spiroperidol stereospecific binding was increased in spontaneously hypertensive rats.

The factors influencing the in vitro activity of antibiotics during anaerobic incubation were studied by the disc method with a facultative organism, Escherichia coli. We observed the effects of incubation aerobically, anaerobically (Torbal jars), in a CO(2) incubator, and aerobically and anaerobically with all CO(2) removed. We also monitored pH changes during incubation and observed the effect of two different initial agar pH values (7.4 and 8.3). With aminoglycosides, zones were larger at pH 8.3 and, in each agar pH group, zones were decreased by incubation with increased CO(2) (anaerobically and CO(2) incubator). A fall in agar pH took place during the first 5 to 7 hr of incubation when increased CO(2) was present. Decreased aminoglycoside zones in the presence of increased CO(2) were due to fall in agar pH. Erythromycin showed the same zone size changes as the aminoglycosides. Chloramphenicol zones were somewhat smaller at the lower medium pH. Zones around tetracycline discs were largest after incubation anaerobically. Further aerobic (or CO(2)) incubation of plates after anaerobic incubation resulted in large "zones of relative inhibition" around the aminoglycoside discs. This suggests that these antibiotics had become more active after exposure to aerobic conditions. Our studies indicate that antibiotic susceptibility test results can be significantly altered by several components of anaerobic incubation including changes in agar pH and CO(2) concentration as well as anaerobiosis per se.

Five different anaerobic culture methods and several different media were compared for their ability to recover anaerobes from clinical specimens. Specimens were obtained from patients with documented infections, avoiding contamination with normal flora, and immediately placed in an anaerobic transporter. Each specimen was cultured by all methods and on all the various media. The comparative data indicate that anaerobic jars (GasPak and evacuation-replacement types) are just as effective in the recovery of clinically significant anaerobes as the more complex roll-tube and chamber methods employing prereduced media. Liquid media were disappointing as a "back-up" system but chopped-meat glucose was superior to two thioglycolate formulations. Growth of all anaerobes was poorer on selective media, but these media were very helpful in the workup of specimens containing mixed growth of anaerobic and facultative organisms. A variety of different anaerobes was isolated, but no very fastidious or extremely oxygen-sensitive organisms were recovered. This suggests that such organisms may not play a significant role in causing clinical infections.

The diagnosis of pyogenic vertebral osteomyelitis was made in seven narcotic addicts between 1967 and 1972. Vertebrae involved were either cervical or lumbar. Bacteriologic diagnosis was made in each case by percutaneous needle biopsy and aspiration. Staphylococcus aureus was cultured in two patients. Five patients had infections due to Gram-negative bacteria, including Klebsiella pneumoniae, Pseudomonas aeruginosa and Enterobacter. All patients were cured by treatment with antibiotics and immobilization.