Report on an outbreak of postinjection abscesses due to Mycobacterium abscessus, including management with surgery and clarithromycin therapy and comparison of strains by random amplified polymorphic DNA polymerase chain reaction.

An outbreak of postinjection abscesses occurred in Barranquilla, Colombia, and was associated with local injections of lidocaine given in a single physician's office. Over a 5-month period, 350 (18%) of approximately 2,000 injected patients developed localized cutaneous abscesses or cellulitis; of 210 abscess specimens that were cultured, 205 were positive for rapidly growing mycobacteria, subsequently identified as Mycobacterium abscessus. The source of the outbreak was not identified. M. abscessus could not be characterized by pulsed-field gel electrophoresis, but all isolates were identical in terms of drug and heavy metal resistance patterns and random amplified polymorphic DNA PCR profiles. We believe this is the first report of the use of this latter technique for investigation of an outbreak due to M. abscessus. Therapy with a combination of surgical excision and 3-6 months' administration of clarithromycin was successful for 95% of 148 patients treated in this manner; in contrast, therapy was successful for less than one-third of patients treated with surgery alone or clarithromycin alone. This is the largest of the nine known outbreaks of postinjection abscesses that have occurred due to rapidly growing mycobacteria and is the first in which an effective method of therapy was demonstrated.

Nocardia pseudobrasiliensis sp. nov., a new species of Nocardia which groups bacterial strains previously identified as Nocardia brasiliensis and associated with invasive diseases.

We studied five strains of a new Nocardia taxon recently identified among Nocardia brasiliensis strains associated with invasive diseases (R. J. Wallace, Jr., B. A. Brown, Z. Blacklock, R. Ulrich, K. Jost, J. M. Brown, M. M. McNeil, G. Onyi, V. A. Steingrube, and J. Gibson, J. Clin. Microbiol. 33:1528-1533, 1995) to determine their taxonomic status. Several characteristics of these organisms, including the presence of chemotype IV cell walls, nocardomycolic acids, a predominant menaquinone similar to that of Nocardia asteroides ATCC 19247T (T = type strain), and G+C contents ranging from 67 to 68 mol%, are characteristics of the genus Nocardia. Phylogenies based on small-subunit ribosomal DNA sequences clearly confirmed that all five strains belong to the genus Nocardia and occur on a single branch that is clearly distinct from N. brasiliensis. This branch forms a clade with Nocardia vaccinii, Nocardia nova, Nocardia otitidiscaviarum, and Nocardia seriolae. The five new strains exhibited high levels of DNA relatedness with each other, as determined by DNA-DNA hybridization experiments (S1 nuclease procedure), but not with N. brasiliensis strains or with strains of the four phylogenetically related Nocardia species mentioned above. The five new strains differ from N. brasiliensis in the following characteristics: mycolic acid pattern, decomposition of adenine, nitrate reduction, and antimicrobial agent susceptibilities. Therefore, we propose that these strains belong to a new species, Nocardia pseudobrasiliensis. The type strain is strain ATCC 51512, which was isolated from a leg abscess on a patient suffering from ulcerative colitis.

New Nocardia taxon among isolates of Nocardia brasiliensis associated with invasive disease.

Nocardia brasiliensis, the second most frequently isolated aerobic actinomycete in the clinical laboratory, is usually associated with localized cutaneous infections. However, 22% of 238 N. brasiliensis isolates from the United States and 12% of 66 isolates from Queensland, Australia, which had been collected over a 17-year period, were associated with extracutaneous and/or disseminated diseases. Of the 62 invasive isolates, 37 (60%) were susceptible to ciprofloxacin and/or were susceptible to clarithromycin and resistant to minocycline, compared with only 6 (3%) of 242 localized cutaneous isolates. The 43 isolates with this susceptibility pattern appeared to define a new taxon. They were similar to Nocardia asteroides complex isolates clinically in proportions from persons with pulmonary (70%), central nervous system (23%), and/or disseminated diseases (37%) in the setting of corticosteroids (74%) or AIDS (14%). This putative new taxon differed from N. brasiliensis in the hydrolysis of adenine (92 versus 4%), beta-lactamase patterns on isoelectric focusing, and the presence of two early mycolic acid-ester peaks by high-performance liquid chromatography. Restriction analysis of a 439-bp fragment of the 65-kDa heat shock protein gene revealed that N. brasiliensis and the new taxon had different restriction patterns with 8 of the 11 enzymes tested. Screening of invasive isolates of N. brasiliensis for susceptibility to ciprofloxacin will identify most isolates of the new taxon, which likely represents a new Nocardia species.

Acquired resistance of Nocardia brasiliensis to clavulanic acid related to a change in beta-lactamase following therapy with amoxicillin-clavulanic acid.

Previous studies have demonstrated that Nocardia brasiliensis is susceptible to amoxicillin-clavulanic acid and that its beta-lactamases are inhibited in vitro by clavulanic acid. A cardiac transplant patient with disseminated infection caused by N. brasiliensis was treated with this drug combination with good response, but relapsed while still on therapy. The relapse isolate was found to be identical to the initial isolate by using genomic DNA restriction fragment patterns obtained by pulsed field gel electrophoresis, but it was resistant to amoxicillin-clavulanic acid. On isoelectric focusing, the beta-lactamase from the relapse isolate exhibited a shift in the isoelectric point (pI) of its major band from 5.10 to 5.04 compared with the enzyme from the pretreatment isolate. As determined by using values of the amount of beta-lactamase inhibitor necessary to give 50 +/- 5% inhibition of beta-lactamase-mediated hydrolysis of 50 microM nitrocefin, the beta-lactamase of the relapse isolate was also 200-fold more resistant than the enzyme from the pretreatment isolate to clavulanic acid and was more resistant to sulbactam, tazobactam, cloxacillin, and imipenem. The beta-lactamase of the relapse isolate exhibited a 10-fold decrease in hydrolytic activity for cephaloridine and other hydrolyzable cephalosporins compared with that for nitrocefin. Acquired resistance to amoxicillin-clavulanic acid in this isolate of N. brasiliensis appears to have resulted from a mutational change affecting the inhibitor and active site(s) in the beta-lactamase.

Beta-lactam resistance in Nocardia brasiliensis is mediated by beta-lactamase and reversed in the presence of clavulanic acid.

Forty clinical isolates and the type strain of Nocardia brasiliensis were screened for susceptibility to 20 beta-lactams. Isolates exhibited a single pattern of resistance, with large zones of inhibition by disk diffusion and low MICs by broth and agar dilutions only to cefotaxime, ceftriaxone, ceftizoxime, Augmentin, and Timentin. All strains produced beta-lactamase, with five different enzyme patterns by isoelectric focusing. Despite the differences in their isoelectric points, the enzymes had the same substrate profiles, with equivalent activity against penicillin, ampicillin, cefamandole, cephalothin, and cephalordine. In an in vitro assay, the enzymes were highly susceptible to clavulanic acid. The MIC50 and MIC90 for the combination of amoxicillin and clavulanic acid (Augmentin) was 2 and 4 micrograms/ml, respectively, compared with 16 micrograms/ml for both values for amoxicillin alone. These studies suggest that beta-lactamase is the major mechanism of beta-lactam resistance in this species and that Augmentin is the first oral beta-lactam with good potential for treating infections due to N. brasiliensis.

Routine radiographic screening of the chest in pregnant women: is it indicated?

Experience with routine antepartum chest radiographic screening from July 1, 1976, through June 30, 1977, in a city-county hospital which serves a predominantly black indigent population was reviewed. The 5422 routine screening chest radiographs produced an extremely low yield of pathology (11 cases), and only 3 of the 11 cases were not suspected from the history or physical examination. Only 2 cases of active pulmonary tuberculosis were discovered, and both patients were recent immigrants from countries with a much higher incidence of tuberculosis. This low case finding probably reflects the general decline in incidence of pulmonary tuberculosis in the United States and suggests that routine screening chest radiographs (done primarily to exclude tuberculosis) are no longer indicated in our pregnant population.

Amebic peritonitis following rupture of an amebic liver abscess. Successful treatment of two patients.

We present two successfully treated cases of amebic peritonitis. Acute peritonitis secondary to intra-abdominal rupture of an amebic liver abscess is an infrequent but serious complication of invasive amebiasis. Its diagnosis should be considered in anyone with a suspected liver abscess, jaundice, or diarrhea in whom peritonitis develops. This diagnosis should be further suggested in the United States if the patient is a male and is of Mexican origin in areas where this racial group constitutes the majority of cases of amebic disease. Use of radioisotope liver scans and the demonstration of serum precipitins to Endamoeba histolytica may provide rapid evidence of invasive disease, although surgical intervention is often necessary to make a specific diagnosis. Emetine hydrochloride alone or followed by metronidazole combined with surgical drainage is the current treatment for amebic peritonitis.