Thermonuclease seroinhibition test for distinguishing Staphylococcus aureus from other coagulase-positive staphylococci

Since coagulase-positive staphylococci from animals are heterogeneous, another test is necessary to distinguish Staphylococcus aureus from them. Staphylococcal thermonucleases appear to be heterogeneous; antisera raised against S. aureus isolated from humans inhibit thermonuclease activity as demonstrated by the metachromatic well-agar diffusion method. The serological specificity of the thermonuclease elaborated by S. aureus of human origin was demonstrated using three antisera and 407 strains of staphylococci from diverse human and animal sources.

Quantitative microbiology of traumatic orthopedic wounds

Quantitative bacterial and fungal cultures carried out on 116 speciments of tissue debrided from traumatic orthopedic wounds yielded 118 bacterial and 8 fungal isolates. The organisms obtained reflected primarily the resident flora of the skin.

Disk agar diffusion susceptibility testing of yeasts

A disk agar diffusion method was developed for testing the susceptibility of rapidly growing yeasts in vitro. A totally defined, completely synthetic agar culture medium (synthetic amino acid medium, fungal) and clinical isolates of Candida spp. and Torulopsis glabrata were used. Turbidimetric adjustment of cell suspensions resulted in standard, reproducible inocula, which gave sharp, clear zones of inhibition when applied by an agar overlay method. Optimal disk loads were determined for amphotericin B, amphotericin B methyl ester, 5-fluorocytosine, clotrimazole, and miconazole. Disk potencies were stable over a 2-month period when stored in a vacuum desiccator at -30 degrees C. Using an error ratebounded classification, the zones of inhibition were correlated with both broth dilution and agar dilution minimum inhibitory concentrations (MICs). With amphotericin B and amphotericin B methyl ester, all isolates were susceptible, yielding zone diameters which clustered within 5 mm. Overall correlations between zone diameters and broth dilution MICs with 5-fluorocytosine, miconazole, and clotrimazole were 97, 96, and 82% (excluding T. glabrata), respectively; correlations of zone diameters with agar dilution MICs were 96, 92, and 88%, respectively. Disk diffusion susceptibility testing of yeasts appears to be generally applicable. However, when results are equivocal, quantitative test methods should be used.

Infective endocarditis caused by Streptococcus bovis resistant to the lethal effect of penicillin G

Penicillin G alone is generally recommended for the treatment of infective endocarditis caused by Streptococcus bovis because clinical isolates of S bovis are represented as being uniformly and markedly susceptible to penicillin G. However, two strains of S bovis recovered from two patients with bacterial endocarditis were resistant to the lethal effect of penicillin G. Combination therapy, cefazolin sodium and gentamicin sulfate in patient 1 and penicillin G and gentamicin in patient 2, was necessary; synergy, as manifested by lethal activity against the infecting strains, was demonstrated in the laboratory. We stress the need to determine the minimal lethal concentration of penicillin G for clinical isolates of S bovis. Until such information is available, particularly in life-threatening infections, combination drug therapy, consisting of an aminocyclitol added to a beta-lactam antimicrobic, should be used.

Comparative susceptibility of four kinds of pathogenic fungi to amphotericin B and amphotericin B methyl ester

The activity of amphotericin B methyl ester was compared with that of amphotericin B, using Candida albicans (34 isolates), Torulopsis glabrata (12 isolates), Filobasidiella neoformans (stat. conid. Cryptococcus neoformans) (14 isolates), and Coccidioides immitis (37 isolates) and tube dilution in a totally synthetic, completely defined medium (SAAMF) with inocula of 10(4) colony-forming units per ml. Minimal inhibitory concentrations were read after 24 h at 34 degrees C for C. albicans and T. glabrata, and after 48 h at 34 degrees C for C. immitis and F. neoformans. Minimal lethal concentrations were determined by subculture of 10% of the volume of the cultures without evident growth onto Sabouraud glucose agar medium. Overall, amphotericin B methyl ester was slightly less active than amphotericin B, with the differences attaining statistical significance for: (i) inhibition of C. albicans and T. glabrata and (ii) killing of T. glabrata.

Totally synthetic medium for susceptibility testing

The results of disk diffusion and plate dilution susceptibility testing of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Proteus mirabilis on media gelled with agar-agar or with a synthetic hydrogel were compared. Synthetic hydrogel can be combined with a totally defined synthetic amino acid medium to yield a reproducible, totally defined, synthetic solid medium without the antagonistic or booster effects of some components of agar. Such a medium could be used as a reference medium for susceptibility testing.

Stability of four antifungal antimicrobics in vitro

The stability of amphotericin B, amphotericin B methyl ester, 5-fluorocytosine, and miconazole was assessed under conditions encountered in bioassay and susceptibility testing in vitro. Although the amphotericins were labile as compared with other drugs, tests should be reliable with all four antimicrobics in view of the rapid action of the polyenes and the relatively slow action of 5-fluorocytocine and miconazole.

Comparative pharmacology of amphotericin B and amphotericin B methyl ester in the non-human primate, Macacca mulatta

The pharmacokinetics of amphotericin B methyl ester hydrochloride (AME) and commercial deoxycholate-stabilized amphotericin B (AMB) were compared after single doses of 5 mg and 1 mg/kg of body weight, respectively, given intravenously in a period of 3 h to adult female rhesus monkeys (Macaca mulatta). By bioassay, the concentrations of AME were 12.2 to 7.2 times higher in the serum and 7.8 to 2.5 times higher in the urine during the 8 h after infusion. The decline in concentrations of the drugs in sera was consistent with a three-compartment, open pharmacokinetic model; rate constants of transfer of the drugs between the compartments and volumes of distribution were calculated. The overall rate of elimination from the central compartment (the bloodvascular space) was about four times greater for AME than for AMB. Serum urea nitrogen and creatinine concentrations were mildly and transiently increased after infusion of AME, whereas the more severe azotemia that followed infusion of AMB persisted for 5 days. AME was less toxic and achieved a greater urinary outfall than AMB. As the antifungal activity of AME is comparable to that of AMB by testing in vitro, further study is warranted.

Nafcillin concentration in cerebrospinal fluid during treatment of staphylococcal infections

The nafcillin concentration of simultaneous cerebrospinal fluid (CSF) and serum specimens from nine patients being treated with parenteral nafcillin for staphylococcal infection were measured. Marked variations in the ratio of CSF/serum nafcillin concentration were observed. However, the concentration of nafcillin in the CSF was greater than the minimum lethal concentration (MLC) for Staphylococcus aureus in eight of the nine patients. In five patients with CSF pleocytosis, the nafcillin concentration was three to 100 times the MLC. These results support the recommendation to use nafcillin in doses of at least 100 to 200 mg/kg body weight-day for treatment of meningitis caused by S. aureus.

Reproducible method for induction of pulmonary coccidioidomycosis in mice

Intranasal instillation of an inoculum has been suggested as a method for establishment of experimental pulmonary infections. Because we encountered untoward variation in rates and times of death with use of this method for inducing coccidioidomycosis in mice, a simple method for direct intratracheal infection was devised. With doses of 50 or 100 arthrospores of Coccidioides immitis, mortality rates were 80%-90% from 14 to 25 days after infection by the intratracheal route and 20%-60% from 12 to 24 days after infection by the intranasal route. The procedure for intratracheal infection caused only slight morbidity, and the method resulted in consistent rates of disease.

Susceptibility of three groups of Staphylococcus aureus to newer antimicrobial agents

Because of the need for non-beta-lactam antimicrobics with antistaphylococcal activity, 14 antimicrobics (3 penicillinase-resistant penicillins, 7 aminocyclitols [5 new], 2 macrolides [1 new], clindamycin, and a new polysaccharide, everninomicin) were tested in vitro for activity against 22 penicillin-susceptible, 51 penicillin-resistant, and 47 methicillin-resistant strains of Staphylococcus aureus. Gentamicin, tobramycin, sisomicin, and verdamicin inhibited almost all strains at concentrations less than 1 mug/ml. The methicillin-resistant strains were as susceptible as other strains to the aminocyclitols and everninomicin. In contrast, many of the methicillin-resistant strains were also resistant to erythromycin, rosamicin, and clindamycin at attainable serum concentrations. The use of the bacterial synthetic amino acid medium, in comparison with Mueller-Hinton broth, resulted in an increase in the observed resistance of methicillin-resistant strains to the penicillinase-resistant semisynthetic penicillins.

Bacteriology of the lower respiratory tract as determined by fiber-optic bronchoscopy and transtracheal aspiration

For assessment of the validity of cultures of tracheobronchial secretions and exudates (TBSE) obtained by fiber-optic bronchoscopy, the aerobic and anaerobic flora of expectorated saliva and TBSE obtained by fiber-optic bronchoscopy from nine healthy volunteers and eight patients were compared with those obtained by fiber-optic bronchoscopy as well). Normal volunteers yielded both aerobic and anaerobic bacteria in amounts usually less than 104.5 colony-forming units (cfu)/ml in TBSE obtained by fiberoptic bronchoscopy. In patients with chronic bronchitis, 42 isolates of aerobic bacteria (104-105.5 cfu/ml) and only 10 isolates of anaerobes (usually less than 104 cfu/ml) were reovered from 15 samples obtained by trantracheal aspiration. The data lead to the conclusion that low-level contamination (less than or equal to 104 cfu/ml) with oral flora is common in TBSE obtained by fiber-optic bronchoscopy. A single potential pathogen in numbers of greater than or equal to 105 cfu/ml may be of etiologic significance, particularly if recovered from purulent drainage material from a localized portion of the lung. Under circumstances in which quantitative bacteriology cannot be done, TBSE obtained by transtracheal aspiration will most reliably reflect the bacterial flora present in the lung.

Effect of culture media on the antifungal activity of miconazole and amphotericin B methyl ester

The capacity of four culture media to obfuscate the antifungal activity of miconazole and amphotericin B methyl ester was evaluated qualitatively by examination of five isolates each of Candida albicans, Candida tropicalis, Candida parapsilosis, Torulopsis glabrata, and Cryptococcus neoformans, and quantitatively by determination of the absolute minimal inhibitory concentrations for a strain of C. albicans. Miconazole, like the predecessor imidazole (clotrimazole), was antagonized by two complex, undefined media (Sabouraud's glucose and brain-heart infusion agars) but not by either of two synthetic formulations (synthetic amino acid medium, fungal and modified yeast-nitrogen base). The antifungal activity of amphotericin B methyl ester, like that of the parent compound amphotericin B, was not materially affected by the culture medium used for testing. When added separately to synthetic amino acid medium (fungal), neither purines nor pyrimidines antagonized miconazole. Ether extraction of Sabouraud's glucose agar failed to diminish the antagonism of this medium for miconazole.

Induction of resistance in Staphylococcus aureus and Klebsiella pneumoniae by exposure to cephalothin and cefoxitin

Six strains each of Staphylococcus aureus and Klebsiella pneumoniae were exposed to subinhibitory, but serially incremental, concentrations of cephalothin and cefoxitin in a totally defined liquid culture medium. After exposure to cephalothin, the level of resistance to both drugs increased; the gain was greater against cephalothin and among the strains of K. pneumoniae. After exposure to cefoxitin, resistance to both drugs developed; this resistance was greater against cefoxitin and among the strains of K. pneumoniae. Acquired resistance was not lost after serial subculture in drug-free medium. Qualitative tests revealed no cephalosporinase activity in the resistant straphylococci and in four of the strains of K. pneumoniae. Two strains of K. pneumoniae, which had been isolated from a patient before and after failure of treatment with cephalothin, respectively, had no demonstrable cephalosporinase activity as isolated but developed activity after exposure to cephalothin in vitro.

Comparison of amphotericin B and amphotericin B methyl ester: efficacy in murine coccidioidomycosis and toxicity

The methyl ester of amphotericin B was compared with the parent compound, amphotericin B, in terms of therapeutic efficacy in experimental murine coccidioidomycosis and of toxicity. Infections were established by intraperitoneal or intratracheal inoculation with arthrospores. The mice were given either intraperitoneal or intravenous injections of drug for 30 days, according to several dosage schedules. At low doses, amphotericin B methyl ester was less effective therapeutically than was amphotericin B; however, at higher doses, amphotericin B was directly lethal and/or nephrotoxic, whereas the methyl ester was therapeutically effective and nontoxic. In contrast to amphotericin B, the methyl ester did not cause either azotemia or histopathologic changes in the kidneys.

Penetration of antimicrobial agents into bronchial secretions

The entry of ampicillin, cephalothin and gentamicin into traceobronchopulmonary secretions/exudates was assessed in 22 patients during 28, episodes of pneumonia or bronchitis. Specimens were collected from the lower respiratory tract via tracheostomies or endotracheal tubes using either the flexible fiberoptic bronchoscope (50 specimens) or an intratracheal catheter (59 specimens). Venous blood was obtained at the same time. The concentrations in the bronchial specimens were less than those in the corresponding serums, amounting to about 10 per cent with ampicillin, 25 per cent with cephalothin and equal to or greater than 40 per cent with gentamicin.

Susceptibility of coccidioides immitis, Candida albicans, and Cryptococcus neoformans to amphotericin B, flucytosine, and clotrimazole

Toxicity and failure of treatment with amphotericin B are stimuli for researchers to evaluate alternative antifungal antimicrobics. Also, data from susceptibility tests of Coccidioides immitis are sparse. With use of a defined, synthetic culture medium, C. immitis (25 strains). Candida albicans (21 strains), and Cryptococcus neoformans (21 strains) were tested against flucytosine, clotrimazole, and amphotericin B. Molecule for molecule, the sequency of activity was: clotrimazole greater than amphotericin B greater than flucytosine (totally inactive) C. immitis; and clotrimazole greater than amphotericin B greater than flucytosine with C. albicans and C. neoformans. With four strains of C. immitis, the minimal inhibitory concentration (of amphotericin B) was the same when inocula of arthrospores were tested as when corresponding spherules/endospores were tested simultaneously and identically. The clinical outcome of coccidioidomycosis in 17 patients treated with amphotericin B correlated best with minimal inhibitory concentration after incubation of cultures for 48 hr; a favorable response was associated with minimal inhibitory concentrations of less than or equal 1.0 mug/ml. Because clinical isolates of fungi appear to vary in susceptibility, in vitro tests may have clinical utility.

Trimethoprim-sulfamethoxazole in chronic bronchitis

Authenic tracheobronchial secretions/exudates (TBSE) were aspirated under direct vision via a sterile catheter passed through a fiberoptic bronchoscope from patients with chronic obstructive pulmonary disease complicated by chronic bronchitis. TBSE, saliva and blood were obtained during long-term administration of trimethoprim-sulfamethoxazole (TMP-SMX) and were assayed for drug content. Before and during treatment TBSE were cultured qualitatively and quantitatively for aerobic and anaerobic bacteria, fungi, mycoplasmas and viruses. Treatment with TMP-SMX was associated with a decrease in the recovery of Hemophilus influenzae, H. parainfluenzae, Klebsiella pneumoniae, Escherichia coli and Proteus mirabilis; however, little effect was observed on the typically nonpathogenic aerobic and anaerobic bacteria of the upper respiratory tract. TMP was found in saliva at concentrations greater than in serum. Both TMP and SMX entered TBSE in absolute and relative concentrations sufficient to take advantage of the potential for synergy against susceptible microorganisms. Patient tolerance of TMP-SMX was generally good and several patients reported a decrease in production of sputum during treatment.

Recovery from encephalomyelitis caused by Herpesvirus simiae. Report of a case

A 29-year-old monkey handler developed an acute encephalomyelitis with neuromuscular dysfunction that progressed to respiratory arrest on the 18th day of illness. Thereafter, with supportive care, the patient's condition improved steadily. The titer of neutralizing antibodies to H simiae rose from 1:4 (eighth day of illness) to 1:512 (47th day of illness). Apparently the fifth known survivor of H simiae (herpesvirus B) encephalomyelitis, this patient is also remarkable because of virtually complete recovery, apparently the second documented instance of a good outcome.

Bear meat trichinosis with a concomitant serologic response to Toxoplasma gondii

A severe case of trichinosis occurred following the ingestion of raw meat from a common black bear, Ursus americanus, that was shot in Butte County, California. Examination of steaks cut from the bear revealed heavy infection with T. spiralis. A good clinical response was obtained following treatment with prednisone (1 mg/kg body weight per day) and thiabendazole (50 mg/kg body weight per day); no toxic effects were observed. In comparison with the pre-treatment biopsy, a more intense inflammatory response was seen following the administration of thiabendazole. Nevertheless, a muscle biopsy taken several months after discharge still showed well-encapsulated, morphologically intact larvae. In addition to the expected immunological responses to T spiralis, a marked rise in titer of antibodies to Toxoplasms gondii was observed by the fluorescent antibody and Sabin-Feldman dye test methods. Since toxoplasma infection of muscle is widespread in man, it is possible that an unrelated disease of muscle could result in stimulation of anti-toxoplasma antibodies similar to the findings in polymyositis and dermatomyositis. Alternatively, the possibility that a dual infection was acquired from the bear meat cannot be excluded.

Microbial development of drug resistance: mechanisms and clinical significance

Bacteria have demonstrated a disconcerting ability to develop resistance to antimicrobial agents nearly as quickly as new compounds become available. During the past two decades the molecular bases of several types of resistance have been elucidated. Mechanisms of resistance include the transference of genetic material either through conjugation (involving direct contact between microorganisms), or indirectly through transduction (involving bacteriophages). In addition to this "infectious" drug resistance, genetic mutations which permit the utilization of new metabolic pathways, and the production of enzymes which can inactivate the antimicrobic have been described. One particularly complex problem has been the ability of many Enterobacteriaceae to develop resistance to multiple antimicrobials simultaneously. The possible effect of such an occurrence is illustrated by the recent epidemic of multiply resistant Salmonella typhi in Mexico. Because the typhoid bacilli shared an identical resistance pattern to an epidemic Shigella dysenteriae type 1 the in vivo interspecies transmission of resistance has been postulated. Understanding the various mechanisms of resistance development should allow more rational use of antimicrobial agents.

Entry of four tetracyclines into saliva and tears

Although meningococci are susceptible to the tetracyclines by testing in vitro, oxytetracycline (OC) and doxycycline (DC) have failed to eliminate carriage, whereas minocycline (MC) has been effective. Because these congeners differ in lipophilicity, they and tetracycline (TC) were studied in volunteers by assay of serum, saliva, and tears obtained after 5 days of treatment. OC and TC were undetectable or attained concentrations subinhibitory for meningococci in saliva and tears. The concentrations of MC in saliva and tears were equal to or greater than the average minimal inhibitory concentration as long as 12 h post-dose. Near inhibitory concentrations resulted with DC at 100 mg/day; yet, doubling the dose to 100 mg/12 h did not yield concentrations that exceeded the average minimal inhibitory concentration for meningococci. The previous reports of failure or meager entry of DC and MC into saliva probably reflected extraction of these drugs in the paraffin chewed by subjects to stimulate salivary flow. The efficiency of entry of the tetracyclines into the secretions of the noninflamed upper respiratory tract correlates with lipophilicity at physiological pH, enabling prediction of meningococcal chemoprophylactic efficacy.

Lymphangiography in diagnosis of fever of unknown origin

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In vitro activity of cephalothin and three penicillins against Escherichia coli and Proteus species

The susceptibility of clinical isolates of Escherichia coli (67) and Proteus species (58) to cephalothin, ampicillin, benzyl penicillin, and phenoxymethyl penicillin was determined in vitro by using broth dilution and disk diffusion tests. The data were correlated by using a four-category scheme for interpreting minimal inhibitory concentrations (groups 1 to 4) as recommended by a subcommittee of an international collaborative study of susceptibility testing. With cephalothin and ampicillin, groups 1 (susceptible) and 2 (moderately susceptible) were susceptible by the disk test, and with benzyl penicillin, similar results were observed when the interpretive zone standards were changed. Strains categorized as group 4 (very resistant) were resistant by the disk method, but group 3 (moderately resistant) strains were not adequately distinguished by disk testing. Group 3 susceptibility to benzyl and phenoxymethyl penicillins can be predicted by extrapolating results from tests with ampicillin disks.

Convenient assay for staphylococcal nuclease by the metachromatic well-agar-diffusion technique

The metachromatic agar-diffusion (MAD) microslide technique was adapted for quantitative assay for staphylococcal thermonuclease in heterogeneous systems, such as milk and broth. When an enzyme-containing solution was placed in a well cut in the agar, a bright pink halo was obtained. The diameter of the pink zone of hydrolysis was related to time and temperature of incubation and to nuclease concentration. Concentrations of nuclease as low as 0.005 mug/ml and as high as 2.0 mug/ml were conveniently determined after 3 hr at 37 C.

Tolerance of staphylococcal thermonuclease to stress

Remarkable tolerance to prolonged heating, prolonged storage, and bacterial proliferation was exhibited by staphylococcal thermonuclease in foods and broth. A purified enzyme preparation added to Brain Heart Infusion broth was unaffected by the growth of five bacterial species. Minimal inactivation was effected by Bacillus subtilis. Optimal growth of Streptococcus faecalis var. liquifaciens caused extensive inactivation of thermonuclease. However, storage at room temperature or the addition of 5% NaCl caused only minimal inactivation.

Metachromatic agar-diffusion microslide technique for detecting staphylococcal nuclease in foods

The metachromatic agar-diffusion (MAD) microslide technique was shown to detect nanogram quantities of staphylococcal thermonuclease in various foods without prior extraction, purification, or concentration.

Influence of culture media on the antistaphylococcal activity of fosfomycin

Antagonism or double zones of inhibition (or both) resulted when Staphylococcus aureus was exposed to fosfomycin in Brain Heart Infusion, tryptic/papaic digest of casein/soybean, and Mueller Hinton culture media; neither occurred with a totally defined, completely synthetic medium. The extent of antagonism was quantitated by determination of the absolute minimal inhibitory concentration of fosfomycin in each medium. By using the synthetic medium and inducers, the hexose-phosphate transport system appeared to be more important than the alpha-glycerophosphate transport system in providing ingress of fosfomycin into staphylococci.

Nuclease production and lysostaphin susceptibility of Staphylococcus aureus and other catalase-positive cocci

Some strains of Staphylococcus epidermidis and Micrococcus sp. produce nucleases. However, thermal stability was shown to be unique to the nucleases of S. aureus. In addition, two micromethods for susceptibility testing to lysostaphin were more precise and convenient than anaerobic glucose fermentation in distinguishing between the genera Staphylococcus and Micrococcus.

Metachromatic agar-diffusion methods for detecting staphylococcal nuclease activity

Based on the metachromatic property of Toluidine Blue O, three, convenient agar-diffusion methods have been developed that enable detection of the nuclease of Staphylococcus aureus at concentrations as low as 0.005 mug/ml in agar and broth cultures. The interactions of agar and deoxyribonucleic acid with Toluidine Blue O are discussed.