Comparative Evaluation of theIn VitroAntimycobacterial Activities of Six Aminoglycoside Antibiotics Using an Agar Dilution Method

Given the increasing prevalence of mycobacterial resistance to aminoglycoside antibiotics, we examined the susceptibility of 76 clinical isolates of mycobacteria to arbekacin, amikacin, gentamicin, kanamycin, tobramycin and streptomycin using an agar dilution method. Only arbekacin and amikacin showed excellent therapeutic potential (minimum inhibitory concentrationis (MICs) < or =0.25-4 microg/ml) against 30 isolates of rapidly growing mycobacteria, including Mycobacterium fortuitum, M. chelonae and a related organism, Nocardia asteroides. The MIC(90)of tobramycin against 23 isolates of M. avium complex was 8 microg/ml, while that of the other 5 aminoglycosides ranged from 64-256 microg/ml. Of the 23 M. tuberculosis isolates tested, 5 showed aminoglycoside resistance (MICs 128 to > or =1,024 microg/ml), while the others were variably susceptible (MICs < or =0.25-32 microg/ml) to all 6 aminoglycosides. The chemotherapeutic potential of arbekacin, amikacin and streptomycin as treatment of tuberculosis was apparent; however, proper patient management would be required to control against the emergence of the drug-resistant strains during prolonged treatment.

Nocardiosis in a tertiary care hospital in North India and review of patients reported from India

Nocardiosis, an uncommon infection of the past, is being increasingly reported in recent years with rise of immunosuppressed patients. In India, very few centers have reported this disease. The present report describes twelve consecutive cases of nocardiosis reported over a period of 26 months (January 2004 to March 2006) from a tertiary care center in north India. The patients were predominantly males (75%) with age range of 8-65 years and mean age of 38.4 years. Eleven patients had known underlying illness including renal transplantation, human immunodeficiency virus infection, and long-term steroid therapy. One patient with cerebral nocardiosis had no detectable predisposing factor. Infection involved central nervous system (3 cases), lungs (5 cases), subcutaneous tissue (1 case), and anterior mediastinum (1 case). Disseminated infection was documented in two patients. Nocardia asteroides complex was incriminated in six patients, N. brasiliensis in five and N. otitidiscaviarum in one patient. All the isolates were sensitive to co-trimoxazole, amikacin, cefotaxime and imipenem. Good therapeutic response was observed in 10 (90.9%) of 11 patients treated with antibiotics including co-trimaxazole, cephalosporins, amikacin, and imipenem alone or in combination. The series of nocardiosis reported from India has also been reviewed.

Case report: Nocardia asteroides mycetoma

Primary cutaneous infections with Nocardia asteroides are rare and have been reported in immunocompromised patients. Herein, we report a case of primary cutaneous Nocardia asteroides mycetoma of the skin in an immunocompetent individual. The infection was treated successfully with trimethoprim-sulfamethoxazole. Because a prolonged incubation time is required for the cultures and since additional biochemical tests are necessary for identification of this species, the clinician should alert the microbiology laboratory when such an infection is suspected clinically.

Reactive cutaneous cytophagocytosis in nocardiosis

Cutaneous nocardiosis, which usually manifests in the form of pustules, abscesses, or subcutaneous nodules, is occasionally found in immunocompromised patients. A 59-yr-old Korean man with myasthenia gravis and thymoma developed nodular skin lesions on his trunk. Histopathologically, abscess formation with a dense infiltrate of neutrophils and many cytophagic histiocytes were observed. Numerous filamentous organisms, which turned out to be Nocardia asteroides by culture, were also found. After sulfamethoxazole-trimethoprim therapy, all of the skin lesions rapidly decreased in size, with a marked diminution of the number of cytophagic histiocytes, and cleared up within four months. On reporting a case of cutaneous nocardiosis showing unusual histopathologic findings, we considered that reactive conditions should be included in the differential diagnosis of the cutaneous cytophagocytosis, and that nocardiosis could be one of the diseases showing reactive cytophagocytosis.

Molecular and biochemical analysis of AST-1, a class A beta-lactamase from Nocardia asteroides sensu stricto

A beta-lactamase gene was cloned from a Nocardia asteroides sensu stricto clinical isolate. A recombinant plasmid, pAST-1, expressed the beta-lactamase AST-1 in Escherichia coli JM109. Its pI was 4.8, and its relative molecular mass was 31 kDa. E. coli JM109(pAST-1) was resistant to penicillins and narrow-spectrum cephalosporins. The beta-lactamase AST-1 had a restricted hydrolytic activity spectrum. Its activity was partially inhibited by clavulanic acid but not by sulbactam and tazobactam. AST-1 is an Ambler class A beta-lactamase sharing 65% amino acid identity with beta-lactamase FAR-1, the most closely related enzyme.

[Thoracic nocardiasis associated with macrophage activation syndrome]

Nocardiasis is an uncommon bacterial disease often observed in immunodepressed patients. Its interactions with the immune system remain poorly known. We report a case of Nocardia asteroides thoracic nocaridiasis in an African subject who also had macrophage activation syndrome. We recall the classic data on nocardiasis in Africa and emphasize the importance of emergence in HIV-infected subjects. The association between nocardiasis and macrophage activation syndrome suggest a possible pathogenic mechanism involving the immune system (lymphocytes and macrophages) and Nocardia asteroides.

Antimicrobial susceptibility profile of soil isolates of Nocardia asteroides from Kuwait

OBJECTIVES

To find the antimicrobial susceptibility profile of 42 soil isolates of Nocardia asteroides against 14 antimicrobial agents representing beta-lactams, aminoglycosides, ciprofloxacin, minocycline, erythromycin and third generation cephalosporins.

METHODS

The antimicrobial susceptibility was determined by the disk diffusion method using Mueller-Hinton agar medium. A homogeneous suspension giving an inoculum of 106-108 CFU/mL was used to streak the plates. The zone of inhibition was read after 36-48 h of incubation at 37 degrees C.

RESULTS

All the soil isolates of N. asteroides were susceptible to amikacin, imipenem and tobramycin. Susceptibility to cephalosporins was quite variable; 86% of the isolates were susceptible to cefotaxime, 57% to ceftriaxone and 40% to cefamandole. Fifty-seven per cent of the isolates showed intermediate susceptibility to cefamandole, 33% to ceftriaxone and 5% to cefotaxime. Ninety-three per cent of the isolates were resistant to sulfamethoxazole alone or in combination with trimethoprim.

CONCLUSIONS

The study reports a wide variation in the antimicrobial susceptibility profile of soil isolates of N. asteroides originating from a single geographical area. Of interest is the finding that over 90% of N. asteroides isolates were resistant to sulfamethoxazole without any previous exposure to this drug. This may have serious therapeutic implications as sulphonamides or the combination of trimethoprim-sulfamethoxazole is the therapy of choice for nocardiosis. Demonstration of resistance to beta-lactam antibiotics may be attributed to the presence of beta-lactamases which was detectable in > 90% of the soil strains of N. asteroides. The study underscores the importance of antimicrobial susceptibility testing for clinical isolates of Nocardia since individual strains show considerable differences in their susceptibility patterns necessitating therapeutic adjustments.

Clinicomicrobiological review of Nocardia keratitis

PURPOSE

To present the clinical profile, laboratory results, and outcome of treatment in 16 patients with Nocardia keratitis.

METHODS

A retrospective review of 16 culture-proven cases of Nocardia keratitis was done. Clinical and microbiologic data were analyzed.

RESULTS

Nocardia constituted 1.7% of laboratory-confirmed bacterial keratitis and was seen predominantly in male subjects (13 of 16) with a mean age of 39.1 years. Although the predisposing factor was unknown in the majority, a definite history of trauma was present in four (25%) cases. Patchy stromal infiltrates were seen in 12 patients. Wreath pattern of infiltrates (six of 16) and hypopyon (nine of 16) were notable features. Nocardia was detectable in corneal scrapings of 10 patients with Gram stain and all patients with 1% acid-fast preparation (six of six). Nocardia asteroides was the causative agent in all except one (N. caviae). All isolates were sensitive to gentamicin; however, topical 30% sulfacetamide was the preferred drug for treatment. Favorable outcome (healed scar) was achieved in 11.

CONCLUSION

Although Nocardia keratitis is a rare condition, a high index of clinical suspicion should be kept in agricultural workers or in patients with trauma who have patchy stromal infiltrates. Sulfonamides are the initial drug of choice, and gentamicin could be an effective alternative. If recognized early, Nocardia keratitis responds to medical treatment with good visual recovery.

Cerebral nocardia abscesses in a patient with AIDS: correlation of magnetic resonance and white cell scanning images with neuropathological findings

We present a case of cerebral nocardiosis in a patient with AIDS. Space-occupying lesions were identified using magnetic resonance imaging (MRI) and white cell scanning. Nocardia asteroides was isolated from blood cultures. The patient's response to treatment with amikacin, imipenem and ceftriaxone was followed clinically and radiologically. When he died 6 months later, N. asteroides was isolated at post-mortem from a cerebral abscess. Although cerebral infections associated with the infiltration of neutrophils are rare in patients with AIDS, this case demonstrates that indium-labelled neutrophils can be used to identify a brain abscess and monitor its response to antimicrobial therapy.

Non-inducible, mainly cell-associated beta-lactamase from Nocardia asteroides strain 108

The beta-lactamase of the soil-borne strain 108 (parental strain) of Nocardia asteroides is a non-inducible enzyme mainly associated with the cells; it can be efficiently extracted by ultrasonication and SDS treatment. Crude enzyme preparations showed penicillinase and cephalosporinase activity. The kinetics of beta-lactamase production and in-vitro susceptibility to combinations of beta-lactam antibiotics plus beta-lactamase inhibitors have been studied in two stable overproducer mutants (A14 and B1) obtained by mutagenization of the parental strain with nitrosoguanidine. The cell-associated enzyme increased with bacterial growth in parental and mutant strains and was particularly abundant in stationary phase cells. The beta-lactamase inhibitors sulbactam and clavulanic acid decreased MIC values of penicillins more efficiently in the parental strain than in mutants, thus indicating some involvement of the enzyme in the resistance of N. asteroides strain 108 to beta-lactam antibiotics.

Comparison of agar dilution, broth microdilution, disk diffusion, E-test, and BACTEC radiometric methods for antimicrobial susceptibility testing of clinical isolates of the Nocardia asteroides complex

An evaluation was undertaken to determine the optimal method for the in vitro susceptibility testing of 26 Nocardia asteroides complex isolates to the following antimicrobial agents: amikacin, ampicillin, amoxicillin-clavulanate, ceftriaxone, ciprofloxacin, erythromycin, imipenem, minocycline, and trimethoprim-sulfamethoxazole. Five testing methods were studied including the agar dilution, broth microdilution, and disk diffusion methods, the epsilometer test (E-test), and the BACTEC radiometric method. Results for each antimicrobial agent and each testing method were interpreted as indicating susceptibility, intermediate susceptibility, or resistance according to current guidelines of the National Committee for Clinical Laboratory Standards (NCCLS) for bacteria that grow aerobically and were then compared to a "gold standard" susceptibility test result. The gold standard result for each Nocardia isolate was established by a consensus of the results of the majority of testing methods used in the study. When the results were combined for all antimicrobial agents tested against all Nocardia isolates by all methods, the BACTEC radiometric method produced the highest level of agreement (97.9%) with the consensus results and had the fewest very major (n = 1), major (n = 2), and minor (n = 2) errors. In contrast, the results of the agar dilution method were in least agreement (93.2%) with the consensus results, and this method also produced the most very major (n = 8), major (n = 4), and, along with the disk diffusion method, minor (n = 6) errors. For all test methods, interpretive errors were most frequent when testing ampicillin or amoxicillin-clavulanate. Moreover, for all Nocardia nova isolates tested, ampicillin susceptibility results by any of the testing methods were not in agreement with the results of testing for beta-lactamase by the nitrocefin (Cefinase) disk method. We conclude that among the methods evaluated, the BACTEC radiometric method appeared to be the best for determining the in vitro susceptibilities of members of the N. asteroides complex to a panel of nine antimicrobial agents. However, none of the test methods, including the BACTEC method, accurately predicted the ampicillin resistance of the N. nova isolates tested, all of which produced beta-lactamase. Presuming that this beta-lactamase hydrolyzes ampicillin, this disparity may relate to the NCCLS breakpoints that were used, which may require modification for this antimicrobial agent when tested against N. nova isolates.

Adrenal insufficiency, recurrent bacteremia, and disseminated abscesses caused by Nocardia asteroides in a patient with acquired immunodeficiency syndrome

Nocardia asteroides is an opportunistic pathogen of increasing incidence in human immunodeficiency virus (HIV)-infected persons. The lungs are the most common site of infection, followed by the brain; involvement of other extrapulmonary sites is less common. We describe a patient with acquired immunodeficiency syndrome who presented with a number of unique manifestations of nocardial infection: the first reported case of bilateral adrenal abscesses with adrenal insufficiency, the first case of a renal abscess due to N. asteroides alone, and the first case of recurrent, symptomatic bacteremia. A review of the literature on nocardial infections in HIV-positive individuals is presented.

[Nocardiosis in patients with human immunodeficiency virus infection in Spain]

BACKGROUND

Nocardia usually infects immunosuppressed patients, particularly with cellular immunity deficiency. Nevertheless, despite severe immunosuppression in patients infected with HIV, nocardiosis is rare among these patients. We report here two cases of nocardiosis in patients with HIV infection and review spanish literature up to 1993, with an analysis of the characteristics of this infection in our country.

METHODS AND RESULTS

The two patients consumed drugs parenterally and Nocardia organism were recovered in blood cultures after 48 hours of inoculation in standard culture media. The source of the infection was cutaneous in one patient, over an area of venipuncture, and pulmonary in the other patient. Previously, eleven cases of nocardiosis had been reported in the spanish literature in patients infected with HIV. Eighty-four percent were males, and all of them consumed drugs parenterally and displayed a severe cellular immunodepression; the total CD4 lymphocyte count was lower than 100/mm3 in patients when this finding was available (6/13). At diagnosis only one patient received prophylaxis against other type of infection with antibiotics theoretically effective against Nocardia at diagnosis. The Nocardia species recovered more frequently was asteroides (77%) and the most common location was the skin (54%). Treatments more frequently employed were sulfametoxazole-trimethoprim (45%) and sulfadiazine (36%), with a good response except in those with cerebral involvement.

CONCLUSIONS

Nocardiosis in patients with HIV infection is rare in Spain. In contrast with other geographical areas skin involvement was the more common form of infection. Prophylaxis with sulfametoxazole-trimethoprim against other infections could be responsible for a lower than expected incidence among this type of patients.

[Clinical and bacteriological aspects of nocardiasis. 9 cases]

OBJECTIVES

Nocardial infection is usually localized in the immunocompetent patient and occurs as an opportunistic disseminated infection in about half of the cases in immunoincompetents patients.

METHODS

We report a retrospective assessment of 9 cases of nocardial infection diagnosed between January 1991 and February 1994.

RESULTS

Six of the patients were immunodepressed: 3 had a disseminated infection with pulmonary (n = 2), brain (n = 2), skin (n = 3) and/or ocular (n = 1) localizations. There were 3 immunocompetent patients with an isolated local infection: skin and bone mycetoma, knee joint and lung. Diagnosis was made on samples obtained invasively in 7 patients. Nocardia asteroides was isolated in 5 patients, N. farcinica in 3 and N. caviae in 1. These organisms showed in vitro sensitivity to amoxicillin-clavulanic acid 5/9, cefotaxime 5/9 (0/3 for N. farcinica), imipeneme 7/9, amikacin 8/8, minocyclin 5/8, pefloxacin 0/8 and trimethoprime-sulfamethoxazol (TMP-SMX) 3/9. Clinical outcome was favourable in all cases and was not always correlated with laboratory sensitivity.

CONCLUSION

TMP-SMX remains the reference antibiotic. For one patient, only TMP-SMX (resistant in vitro) was effective; with all the other antibiotic tried (sensitive in vivo) treatment failed.

Use of yeast killer system to identify species of the Nocardia asteroides complex

We evaluated the ability of the yeast killer system to differentiate members belonging to the Nocardia asteroides complex (Nocardia asteroides, Nocardia farcinica, and Nocardia nova). Nocardia strains were selected randomly from clinical isolates. Type strains of each Nocardia species and recognized killer yeasts were taken from different collections. A clear area of inhibition surrounding the yeast cells demonstrated a positive killer effect on Nocardia spp. Two yeast strains, Pichia mrakii (K9) and Pichia lynferdii (K76), showed different killer activities against each Nocardia species. The group N. asteroides was identified as K9+ K76-, the group N. farcinica was identified as K9- K76-, and the group N. nova was identified as K9+ K76+. The three killer identifications correlated with specific taxonomic groups determined by using classical methods. The yeast killer system may be a useful means for identifying organisms within the N. asteroides complex.

Nocardial brain abscess: treatment strategies and factors influencing outcome

The successful management of nocardial brain abscess remains problematic. The authors report 11 cases of nocardial brain abscess treated between 1971 and 1993 and review 120 cases reported since 1950. The clinical findings included focal deficits in 55 patients (42%), nonfocal findings in 36 (27%), and seizures in 39 (30%). Extraneural nocardiae were present in 66% of the cases; pulmonary (38%) and cutaneous/subcutaneous (20%) locations were the most frequent. The abscesses were single in 54% of the patients, multiple in 38%, and of unknown number in 8%. Forty-four of 131 patients (34%) were immunocompromised; since 1975, 18 of 40 immunocompromised patients (45%) were transplant recipients and six (15%) had human immunodeficiency virus. The mortality rate was 24% after initial craniotomy and excision (11/45), 50% after aspiration/drainage (17/34), and 30% after nonoperative therapy (7/23); 29 cases (22%) were diagnosed at autopsy. The mortality rate was 33% in patients with single abscesses and 66% in those with multiple abscesses (P < 0.0003). There was no difference in the mortality rates of immunocompromised and nonimmunocompromised patients treated before computed tomography (CT) was available; since the advent of CT, however, the mortality rate has been significantly higher in immunocompromised patients (55% vs. 20%, P < 0.05). Although the mortality rate for nocardial brain abscesses has dropped almost 50% since the advent of CT, it has remained virtually unchanged in immunocompromised patients and is three times higher than that of other bacterial brain abscesses (30% vs. 10%). The authors recommend image-directed stereotactic aspiration for diagnosis; however, craniotomy and total excision are necessary in most cases, because nocardial abscesses are usually multiloculated. Patients with minimal neurological deficits or small abscesses may be treated initially with antibiotics alone. Sulfonamides, alone or in combination with trimethoprim, are most effective and should be continued for at least 1 year. Minocycline, imipenem, or aminoglycoside in combination with a third-generation cephalosporin may be used with reasonably good success as second-line agents in cases of allergy or nonresponsiveness to sulfa agents.

Activity of antimicrobial drugs evaluated by agar dilution and radiometric methods against strains of Nocardia asteroides isolated in Italy from immunocompromised patients

Benzylpenicillin, amoxicillin, amoxicillin plus clavulanic acid, cephalothin, cephaloridine, cefotaxime, imipenem, erythromycin, clarithromycin, azithromycin, amikacin, ciprofloxacin and trimethoprim-sulfamethoxazole were tested in vitro by the agar dilution method against eleven strains of Nocardia asteroides isolated both from AIDS and other immunocompromised patients. Imipenem, amikacin and trimethoprim-sulfamethoxazole were shown to be the most active drugs with minimum inhibitory concentrations (MIC) values nearly always lower than concentrations achievable in blood. Ciprofloxacin, cephaloridine and cefotaxime were moderately active, while the remaining drugs were totally ineffective. When susceptibility was assessed by the radiometric method the MIC90 values were uniformly lower than those in the agar method, possibly due to lower inactivation of drugs during incubation. The two methods showed a good correlation only for imipenem, amikacin and ciprofloxacin. The results obtained by the radiometric method seem to indicate that, as for mycobacteria, this method may also give a more accurate evaluation of the antimicrobial susceptibility of Nocardiae.

Nocardiosis in renal transplant recipients undergoing immunosuppression with cyclosporine

Nine cases of nocardiosis were diagnosed among 1,255 renal transplant recipients given cyclosporine (CsA)-prednisone for immunosuppression between August 1980 and March 1992 (incidence, 0.7%). Of these nine patients presenting with nocardiosis 32-1,806 days after transplantation, eight had pulmonary involvement, two had skin manifestations (one with localized disease), and one had a cerebral abscess and a pleural effusion. All cases required aggressive diagnostic procedures. Nocardia asteroides was isolated in seven cases and Nocardia brasiliensis in two. All but one case was cured. Included among the cures were all of four cases treated with amoxicillin/clavulanic acid. Therapy with CsA-prednisone was continued throughout the infection in eight cases. Analysis of a group of 154 historical controls who received azathioprine (AZA)-prednisone for immunosuppression after renal transplantation (performed before 1980 at the same center) revealed four cases of nocardiosis (incidence, 2.6%). Thus nocardiosis is apparently less common among renal transplant recipients given CsA-prednisone than among those given AZA-prednisone. The clinical presentation of nocardiosis in renal transplant recipients is variable, with pulmonary involvement predominating. Diagnosis requires an aggressive approach. Chemotherapy is successful in most cases, including those treated with amoxicillin/clavulanic acid when the isolate is susceptible.

Use of imipenem in the treatment of pulmonary nocardiosis

A case of pulmonary nocardiosis with empyema in a 55-year-old man with macroglobulinemic lymphoma is presented. Treatment with imipenem followed by oral trimethoprim-sulfamethoxazole (TMP-SMX) resolved his symptoms and cleared the roentgenographic abnormalities. This case illustrates the clinical potential of imipenem against Nocardia.

In vitro germicidal activity of teat dips against Nocardia asteroides and other udder pathogens

Nine commercial teat dip formulations containing 1.94% linear dodecylbenzene sulfonic acid, or 1% available iodine from nonylphenoxypoly (ethyleneoxy) ethanol-iodine complex, or .5% chlorhexidine acetate were tested for contamination with aerobic and anaerobic bacteria and their in vitro germicidal activity against Staphylococcus aureus, Streptococcus agalactiae, Escherichia coli, and Nocardia asteroides. All products were free of bacteria when neutralized samples were tested on blood agar or liquid thioglycollate media. To test for in vitro efficacy, each teat dip preparation was mixed with a suspension of one of the pathogenic test organisms containing 10(8) bacteria/ml (final concentration) for .5 to 15 min. Viable bacteria were evaluated by direct plating of neutralized aliquots and by filtration techniques. All products were effective against E. coli, Staph. aureus, and Strep. agalactiae. With N. asteroides, the direct plating method gave equivocal results. The filtration experiments indicated that all teat dips containing dodecylbenzene sulfonic acid and nonylphenoxypoly (ethyleneoxy) ethanol-iodine complex were effective against all four pathogens. Three of the teat dips containing chlorhexidine acetate were ineffective against N. asteroides. The fourth teat dip, containing chlorhexidine acetate and an emollient, was partially effective.

The timing of exposure of mononuclear phagocytes to recombinant interferon gamma and recombinant tumor necrosis factor alpha alters interactions with Nocardia asteroides

Nocardia asteroides modulates phagocyte function and grows within macrophages. Because interferon gamma (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) have been shown to activate macrophages to kill a variety of microorganisms, the effects of IFN-gamma and TNF-alpha on the activation of murine macrophages and human monocytes to kill nocardiae were studied. It was found that macrophages or monocytes treated with either IFN-gamma, TNF-alpha, or lipopolysaccharide as a secondary signal did not demonstrate increased microbicidal activity against N. asteroides even though these phagocytes were effective at killing the fungus Coccidioides immitis and the protozoan Toxoplasma gondii. Preincubation of phagocytes for 24 h with these compounds resulted in an enhancement of nocardial growth. In contrast, coincubation of these factors with the nocardiae and mononuclear cells during phagocytosis resulted in inhibition of nocardial growth even though this bacterium was not killed. Therefore, the specific timing of the exposure of the phagocyte in vitro to IFN-gamma or TNF-alpha has a significant effect on its ability to alter nocardial growth.

Localized cutaneous nocardiosis in Japan. A new case

We report a case of localized cutaneous nocardiosis due to Nocardia asteroides, appearing on the anterior surface of the right forearm of a 29-year-old woman. Examination of the skin revealed a firm subcutaneous nodule measuring 32 x 20 mm and accompanied with a small ulcer. The histology of the lesion showed granulomatous changes interspersed with large numbers of polymorphonuclear leukocytes. On Gram staining, a few bacillary bodies were found scattered through the lesion, but no grains were detected. The classification of the clinical types of cutaneous nocardiosis is discussed, and the Japanese literature on localized cutaneous nocardiosis is examined.

Influence of nutritional factors on growth and hydrolytic enzyme production in Nocardia asteroides

The growth and production of hydrolytic enzymes such as alpha-amylase, esterase and peroxidase as influenced by the type of media, carbon and nitrogen sources and C:N ratio were monitored in Nocardia asteroides at 37 degrees C. Sabouraud dextrose and the synthetic media yielded maximum growth compared with tryptic soy broth. Among the carbon sources (dextrose, fructose, sucrose, maltose, starch and citrate), monosaccharides supported maximum growth and induced higher alpha-amylase activity but repressed the peroxidase activity. On the other hand, the disaccharides and starch produced less growth but induced maximum esterase and peroxidase activities. Glutamate among the nitrogen sources (nitrate, nitrite, ammonium, hydroxylamine, glutamate and casein) supported maximum growth. Glutamate, nitrate and casein induced alpha-amylase and esterase activities but suppressed peroxidase activity. Nitrite, ammonium and hydroxylamine stimulated peroxidase activity to the maximum but repressed alpha-amylase and esterase activities. Low, medium and high C:N ratios induced maximum peroxidase, esterase and alpha-amylase activities, respectively.

Two cases of Nocardia asteroides sternotomy infection treated with ofloxacin and a review of other active antimicrobial agents

Two patients who developed post-operative sternotomy infections due to Nocardia asteroides were treated successfully with ofloxacin, in vitro susceptibility of the organisms being used as a guide to dosage. The place of this drug in the treatment of infection due to Nocardia asteroides merits further investigation.

Drug-resistant Nocardia asteroides infection in a patient with acquired immunodeficiency syndrome

We have reported what we believe to be the first case of disseminated infection due to a multiply drug resistant strain of Nocardia asteroides in a patient with the acquired immunodeficiency syndrome and concomitant disseminated histoplasmosis. This strain of the organism fits a pattern of susceptibility that is rare among N asteroides isolates in general and has been called the type 5 pattern, described as a resistance to broad spectrum cephalosporins, ciprofloxacin, and all aminoglycosides except amikacin. The recognition of disease due to this group of organisms is especially important in patients with AIDS because sulfonamides, considered the drugs of choice for treatment of N asteroides infection, are associated with a high incidence of adverse effects in these patients.

Acid and alkali as aids in differentiation of pathogenic Nocardia and for their isolation from clinical specimens

The tolerance of Nocardia brasiliensis, Nocardia asteroides and Nocardia caviae to different concentrations of acids and alkalis was studied in this work. The purpose was to determine their use: (a) in the differentiation of species; (b) for decontamination of clinical materials during the isolation of pathogenic Nocardia. The results showed (1) that both 2 M NH3 and 0.05 M H2SO4 solutions are useful for differentiating species. They can also be used as a complementary method for identification. (2) That both 1 M NH3 and 0.05 M H2SO4 solutions were useful for decontamination of clinical materials during the isolation of pathogenic Nocardia.

Cefotaxime-resistant Nocardia asteroides strains are isolates of the controversial species Nocardia farcinica

A recent study of Nocardia asteroides revealed that 95% of clinical strains had one of five antibiotic resistance patterns. We found the pattern of resistance to cefotaxime and cefamandole in 19% of 200 clinical N. asteroides isolates. Isolates with this drug resistance pattern were from numerous geographic sources and were associated with significant clinical disease (56% of patients had disseminated infections). Phenotypic studies revealed that these isolates were relatively homogeneous and matched previous descriptions and reference strains of the controversial species N. farcinica. Growth at 45 degrees C, acid production from rhamnose, ability to utilize acetamide as a nitrogen and carbon source, and resistance to tobramycin and cefamandole were features of N. farcinica that could be tested in the clinical laboratory and allowed their distinction from N. asteroides. The serious nature of disease due to N. farcinica and its resistance to the newer cephalosporins suggest a clinical need for laboratory identification of this species. (Current tests used in clinical laboratories do not distinguish N. farcinica from N. asteroides.) This is the first recognition that N. farcinica has a specific drug resistance pattern and confirms the previously described concept that drug resistance patterns of N. asteroides may be associated with specific taxonomic groups.

Nocardia infection in the acquired immunodeficiency syndrome

A case of Nocardia asteroides pneumonia in a patient with the acquired immunodeficiency syndrome who was intolerant of sulfadiazine is described. On cefuroxime, the patient had a complete resolution of his Nocardia pneumonia. Disk-diffusion and broth microdilution antibiotic susceptibility testing (MIC less than or equal to 2 micrograms/ml) strongly supported the use of cefuroxime as treatment in this patient. Susceptibility testing with newer cephalosporins should be considered for all significant Nocardia isolates.

[In vitro susceptibility of pathogenic Nocardia to beta-lactam antibiotics, especially imipenem, a carbapenem antibiotic]

In vitro antibacterial activity of 30 beta-lactam antibiotics including 2 beta-lactamase inhibitors (clavulanic acid and sulbactam) against 2 major pathogenic Nocardia, i.e. Nocardia asteroides group and Nocardia brasiliensis was studied. Among the antibiotics tested, a newly developed carbapenem antibiotic, imipenem (IPM), was found to be the most active, followed by oxacephem group antibiotic flomoxef (FMOX). IPM exhibited activity against only N. asteroides group (N. asteroides, Nocardia farcinica and Nocardia nova). On the other hand, FMOX showed activity against all pathogenic Nocardia tested. A 2- to 30-fold decreases in minimum inhibitory concentration (MIC) for N. asteroides, N. brasiliensis and N. farcinica was noted when antibiotics and beta-lactamase inhibitors were combined compared to antibiotics alone. Further combination and enzymatic studies indicated that all pathogenic Nocardia possess beta-lactamase except for a half of the strains of N. nova. These species' specific sensitivity patterns of pathogenic Nocardia are discussed in this paper with references to their taxonomic positions.

Antimicrobial synergism in the therapy of experimental cerebral nocardiosis

A mouse model of cerebral nocardiosis was used to determine the efficacy of synergistic antimicrobial combinations in reducing bacterial colony counts per gram of brain tissue. The combinations of imipenem-cefotaxime and imipenem-trimethoprim/sulphamethoxazole (TMP/SMP) were compared with each other and with each agent used alone. A saline treated control group was also included. At the completion of 72 h of therapy the combinations of imipenem-cefotaxime and imipenem-TMP/SMX were the most effective in reducing bacterial colony counts. These were statistically superior to cefotaxime and TMP/SMX used alone but not statistically superior to imipenem alone. TMP/SMX was not effective in this model and was inferior to all other antibiotic treatments.

Antimicrobial susceptibility patterns of Nocardia asteroides

Testing of the susceptibility to 12 antimicrobial agents, including beta-lactams, aminoglycosides, ciprofloxacin, and erythromycin, was performed by broth microdilution on 78 consecutive clinical isolates of Nocardia asteroides. Surprisingly, a limited number of patterns of susceptibility were identified that included all drug classes, with 95% of isolates exhibiting one of five patterns. One group (17%) exhibited resistance to the broad-spectrum cephalosporins, one group (18%) was susceptible to both ampicillin and erythromycin, one group (17%) was susceptible to ampicillin and carbenicillin but intermediate in susceptibility to imipenem, and the most common group (35%) was resistant to ampicillin but susceptible to the broad-spectrum cephalosporins and imipenem. The most active parenteral agents were amikacin (95%), imipenem (88%), ceftriaxone (82%), and cefotaxime (82%), while the most active oral agents were the sulfonamides (100%), minocycline (100%), and ampicillin (40%). Additional studies are needed to determine whether differences in beta-lactamases relate to varying beta-lactam resistance and whether taxonomic differences that correlate with the different susceptibility groups can be identified.

Differentiation between genera Rhodococcus and Nocardia by susceptibility testing to kanamycin and some other antituberculosis agents

The test for susceptibility to kanamycin is useful for differentiating between the genera Rhodococcus and Nocardia. All rhodococci except R. equi, R. erythropolis, and R. aurantiacus are susceptible to kanamycin, whereas all nocardiae except N. otitidis-caviarum are resistant to kanamycin. Tests for susceptibility to rifampicin, streptomycin, and minocycline also are useful for differentiating among the species of each genus.

Cure of brain abscess caused by Nocardia asteroides resistant to multiple antibiotics

A 29-year-old man with pulmonary infiltrates due to pulmonary alveolar proteinosis had Nocardia asteroides pneumonia and brain abscess. The nocardial infections persisted after therapy with sulfonamides, minocycline, and cefotaxime. Based on the susceptibility studies and serum antibiotic concentrations, he was treated with minocycline, 400 to 600 mg daily, cefotaxime, 12 to 30 gm daily, and probenecid for 15 months. Proteinuria observed near the completion of therapy was transient. Three years after therapy, the infections appear to have been cured.

Susceptibility testing of Nocardia species for the clinical laboratory

Not all patients are able to tolerate or show a favorable response to the treatment of choice for Nocardia, the sulfonamides. Many new drugs are available with good activity against N. asteroides, the most common pathogenic species, although susceptibility to these agents, including amikacin, amoxicillin/clavulanic acid, and the third generation cephalosporins, is variable. For these and other reasons, we recommend routine susceptibility testing of Nocardia. Disk diffusion testing on Mueller Hinton agar is the best currently available clinical method. A suggested control strain and tentative susceptible and resistant breakpoints for 12 antimicrobial agents are provided. This includes agents not previously evaluated, including cefotaxime, amikacin, ciprofloxacin, and doxycycline. The zones of inhibition were all larger than those currently used by the NCCLS for rapidly growing bacteria, and the disk breakpoints generally fit best with the MIC breakpoints used with the dilution susceptibility method (M7-T). A broth microdilution MIC method is described that showed good correlation with disk diffusion results, but need additional study. Because of limited experience in most laboratories with this species, reliance on a good reference laboratory for confirmatory susceptibility testing is recommended. Beta-lactamase testing is not helpful, as almost all Nocardia produce beta-lactamase, although many isolates retain susceptibility to selected beta-lactams.

Susceptibility of Nocardia asteroides to new quinolones and beta-lactams

The susceptibility of 31 strains of Nocardia asteroides to various quinolones and beta-lactams, as well as coumermycin, amikacin, and minocycline, was determined by the agar dilution technique. Ciprofloxacin was the most active fluoroquinolone tested on a weight basis, as it inhibited approximately 50% of the isolates at achievable drug levels in serum. Ceftriaxone and cefpirome were the most active cephalosporins in this system with MICs of 8 micrograms/ml for 80% of strains tested. Imipenem, amikacin, and minocycline were the most effective agents tested.

Contribution of neutrophils and cell-mediated immunity to control of Nocardia asteroides in murine lungs

To distinguish between the contributions of neutrophils and cell-mediated immunity to defense against Nocardia asteroides in the lung, we induced pneumonia in BALB/c mice by intranasal inoculation. We studied the course of pneumonia by histology, bronchoalveolar lavage, and quantification of colony-forming units in lungs. Mice with intact host defenses had an initial inflammatory response, consisting mostly of neutrophils, followed by a mononuclear cell infiltrate. Nocardiae were eradicated during the seven days after inoculation. Mice in which the early, predominantly neutrophil inflammatory response was prevented with mechlorethamine or antiserum to neutrophils had little inflammation, and nocardiae grew extensively. Mice in which cell-mediated immunity was impaired with cyclosporin A or cortisone acetate developed abscesses; neutrophils were abundant, but nocardiae proliferated. The occurrence of these three separate and distinct patterns suggested that both neutrophils and cell-mediated immunity are necessary for optimal control of N. asteroides infection.

Amikacin-containing regimens for treatment of nocardiosis in immunocompromised patients

Eight patients with disseminated infections due to multi-resistant Nocardia asteroides were administered amikacin in combination with other effective antibiotics for a duration of 2 to 12 months. Seven patients were considered cured at follow-up after two years.

Therapy of experimental cerebral nocardiosis with imipenem, amikacin, trimethoprim-sulfamethoxazole, and minocycline

A mouse model of cerebral nocardiosis was used to determine relative antibiotic efficacy by reducing bacterial colony counts per gram of brain tissue. The antimicrobial agents employed were demonstrated in vitro to be inhibitory to most strains of Nocardia asteroides at very low concentrations. The agents used in this study were imipenem-cilastatin, amikacin, trimethoprim-sulfamethoxazole, and minocycline. Antibiotics were administered every 4 h for 72 h before animal sacrifice. Bacterial colony counts were assayed at various time points before the completion of therapy. Imipenem-cilastatin and amikacin were the most effective agents tested. Trimethoprim-sulfamethoxazole was less effective than imipenem and amikacin but more effective than minocycline. Minocycline did not eradicate intracerebral organisms and was similar to saline (control) in its effects.

Lack of synergy between phagocytes and antimicrobials against Nocardia asteroides

Previous observations suggested that synergy between antimicrobials and phagocytes may occur during Nocardia asteroides infection. We incubated N. asteroides with seven antimicrobials, and then exposed the nocardiae to phagocytes. Neutrophils and monocytes killed about half the nocardiae whether or not the nocardiae had been preincubated with antimicrobials. We also determined whether exposure to neutrophils led to increased susceptibility of nocardiae to antimicrobials, and it did not. We found no evidence for synergy between antimicrobials and phagocytes in host defence against this bacterium.

In-vitro susceptibility of Nocardia asteroides to 21 beta-lactam antibiotics, in combination with three beta-lactamase inhibitors, and its relationship to the beta-lactamase content

Twelve strains of Nocardia asteroides were studied for their susceptibility to 21 beta-lactam antibiotics, alone or in combination with clavulanic acid, sulbactam, or BLP 2013, and for their content of beta-lactamase. Eleven strains were shown to have beta-lactamase activities, which gave three different patterns after analytical isoelectric focusing. The only strain with no detectable beta-lactamase was the most susceptible to the antibiotics tested. The other strains containing beta-lactamases showed almost the same susceptibility profile. Clavulanic acid was the only beta-lactamase inhibitor to show a significant synergistic effect when combined with penicillins.

Effects of hemodialysis on the pharmacokinetics of amoxicillin/clavulanic acid combination

The effects that renal disease and hemodialysis have on the pharmacokinetics of amoxicillin/clavulanic acid combination were studied in a patient receiving this combination for the treatment of a Nocardia asteroides infection. Hemodialysis increased the clearance of both substances as evidenced by lower serum concentrations during the on-dialysis day, i.e., 2.3 +/- 0.8 vs. 5.9 +/- 1.2 micrograms/ml for clavulanic acid and 8.0 +/- 1.8 vs. 12.4 +/- 0.9 micrograms/ml for amoxicillin. Clavulanic acid appeared to be influenced to a greater extent as compared to amoxicillin because of its higher extraction ratio (0.74 vs. 0.44) as well as a higher observed ratio of amoxicillin to clavulanic acid during the on-dialysis day (3.59 +/- 1.27 vs. 2.28 +/- 0.65; p less than 0.05). Comparison of the area under the serum concentration-time (AUC) during the off-dialysis day with published AUC values suggested accumulation of amoxicillin/clavulanic acid. These data indicate that dosage adjustments for amoxicillin/clavulanic acid may be required in patients with chronic renal failure who are on hemodialysis. Further studies in this patient population are needed before specific dosing guidelines can be provided.

In vitro susceptibility of Nocardia asteroides to 25 antimicrobial agents

Fifty-two clinical isolates of Nocardia asteroides were tested by agar dilution for their susceptibility to 25 antimicrobial agents. In general, susceptibility could not be predicted based on the antibiotic class tested. However, the beta-lactams, including third-generation cephalosporins, were generally ineffective (MIC for 90% of the organisms [MIC90], between 64 and greater than 256 micrograms/ml), whereas minocycline and doxycycline were generally effective (MIC90, 4 and 8 micrograms/ml, respectively). Cycloserine was not effective below 60 micrograms/ml. The MIC50 and MIC90 of sulfamethoxazole was 16 and 32 micrograms/ml, respectively, and that of trimethoprim varied widely (16 and greater than 256 micrograms/ml, respectively). Based on MIC90 data, only doxycycline, minocycline, sulfamethoxazole, and imipenem could be applied empirically.

Synergistic action of trimethoprim and sulfamethoxazole for Nocardia asteroides: efficacious therapy in five patients

Eighteen isolates of Nocardia asteroides were tested for in vitro susceptibility to trimethoprim (TMP) and sulfamethoxazole (SMZ) alone and in various combinations using disc and paper strip diffusion tests. TMP-SMZ showed synergistic action for two-thirds of teh nocardia isolates tested. Five patients with Nocardia pneumonia were treated with TMP-SMZ and all were cured. Four of the patients' isolates were tested and all showed synergistic patterns of inhibition with the spaced disc and paper strip methods. The agar diffusion disc and synergy tests of TMP-SMZ appear to correlate with clinical usefulness when the Nocardia are susceptible with large zones of inhibition around the combination TMP-SMZ disc.

A cephalosporin active in vivo against Nocardia: efficacy of cefotaxime in murine model of acute pulmonary nocardiosis

Cefotaxime, a cephalosporin drug, has been shown to be active in vitro against nocardiae, a finding confirmed in this study. Pharmacokinetic studies were performed in mice to define regimens which provided peak serum levels comparable to that achieved in man with currently used doses. These regimens were shown to be effective with only short courses of therapy of rapidly progressive and highly lethal N. asteroides infection, produced by pulmonary challenge of mice. This suggests the possible utility of this drug in human nocardiosis.