Evaluation of two rapid methods to screen pathogens from stool specimens.

Two rapid methods, the Enteric Pathogen Screen (EPS) cards of the AutoMicrobic system (Vitek Systems, Inc., Hazelwood, MO) and the Bactigen Salmonella-Shigella latex agglutination (LPA) method (Wampole Laboratories, Cranbury, NJ) were compared with conventional biochemical tests to screen stool cultures having suspicious colonial morphologic characteristics for the presence of Salmonella and Shigella in a study of 481 isolates from stool specimens and 104 stock cultures. Compared with conventional testing, overall, 327 of 394 (83%) clinically irrelevant organisms resulted in a report of no Salmonella spp., Shigella spp., or Yersinia enterocolitica with EPS. Four hundred forty-nine of 457 (98%) of clinically irrelevant organisms yielded negative LPA results. Because the LPA method is faster, eliminates more clinically irrelevant organisms from further testing, and does not require the use of an expensive identification system, the authors believe that it is better suited for direct screening for Salmonella and Shigella for most clinical laboratories.

Hodgkin's disease presenting as a parasternal chest wall mass.

A 53 year-old Moroccan woman presented with a tender parasternal mass. Computerized tomography showed a mediastinal mass protruding through the sternum. Cytologic examination of fluid collected from the mass repeatedly showed acute inflammation. Tuberculostatics were started. Since patient did not improve on tuberculostatics, a small supraclavicular lymph node was removed. Histologic examination showed Morbus Hodgkin of the nodular sclerosing type. Ultimately, cytologic examination of fluid from the parasternal mass showed atypical cells. Response on chemotherapy was excellent with complete disappearance of the parasternal mass. This is a very unusual extranodal presentation of Hodgkin's disease.

Update on antiviral therapy for genital herpes infection.

For the primary infection of genital herpes, antiviral therapy with acyclovir is the gold standard. For recurrences, there are two options: antiviral treatment of each outbreak as it arises, or suppression of outbreaks with daily oral therapy. Patients tend to prefer the latter because it can decrease the number and severity of outbreaks, but it increases asymptomatic viral shedding and, therefore, the risk of unwittingly transmitting herpes simplex virus to uninfected sexual partners.

Comparison of broth microdilution and agar dilution for susceptibility testing of Neisseria gonorrhoeae.

Broth microdilution was compared with agar dilution to test the susceptibilities of 170 clinical isolates of Neisseria gonorrhoeae to several antimicrobial agents. Percents agreement between the two methods within 1 doubling dilution were 98.8% for enoxacin, 94.3% for penicillin G, 93.5% for spectinomycin, and 98.4% for ceftriaxone.

The effect of sublethal concentrations of aminoglycosides on adherence of Pseudomonas aeruginosa to hamster tracheal epithelium.

Perfused hamster tracheal explants were used to examine the adherence of mucoid and non-mucoid strains of Pseudomonas aeruginosa to intact tracheal epithelium when grown in 0.5 MIC of tobramycin or gentamicin. Tracheal explants were perfused for 2 h with 10(7) cfu of P. aeruginosa grown overnight in trypticase soy broth containing 0.5 MIC of tobramycin or gentamicin or without antibiotics. After infection, the explants were washed and a 4 mm section was homogenized, diluted and plated for colony counts. Mucoid strains of P. aeruginosa grown in the presence of the aminoglycosides did not produce alginate and were not as adherent as the same strains which were not grown in antibiotics. Adherence of non-mucoid strains of P. aeruginosa grown in sublethal concentrations of the aminoglycosides was not significantly reduced compared with the adherence of the same strains which were not exposed to antibiotics. These results indicate that mucoid strains of P. aeruginosa growing in the presence of sublethal concentrations of aminoglycosides do not produce alginate and may not colonize the epithelial surface.

The effect of sublethal levels of antibiotics on the pathogenicity of Pseudomonas aeruginosa for tracheal tissue.

Hamster tracheal organ cultures were used to evaluate the ability of two aminoglycoside and two beta-lactam antibiotics to protect the epithelium from damage due to Pseudomonas aeruginosa infection. Hamster tracheal explants were infected with strains of P. aeruginosa for 4 h and washed to remove nonadherent organisms. The explants were incubated for an additional 18 h in fresh minimal essential medium containing inhibitory or subinhibitory concentrations of antibiotics. The explants were examined by scanning electron microscopy and bacterial elastase and exotoxin A production was detected by ELISA and a western blot assay respectively. Concentrations of aminoglycosides below the MIC for the infecting strain protected the epithelium from damage and inhibited the production of exotoxin and elastase. The beta-lactam antibiotics were not protective and epithelial damage was observed at antibiotic levels equal to or higher than the MIC for that strain. The beta-lactam treated cultures continued to release elastase and exotoxin A at antibiotic concentrations equivalent to or higher than the MIC for that strain. Thus subinhibitory levels of aminoglycoside antibiotics could protect the infected epithelium from damage by inhibiting the release of toxic substances from the invading bacteria. In contrast, bacteria exposed to beta-lactam antibiotics may continue to release extracellular toxins which can damage the tissue.

Clinical significance of Candida species isolated from cerebrospinal fluid following neurosurgery.

Twenty-one patients for whom adequate clinical data were available were identified in a retrospective review of cases of Candida species isolated from cerebrospinal fluid (CSF) following neurosurgery; 86% had indwelling cerebrospinal devices (shunts). Candida species were isolated from multiple CSF samples from 10 patients; CSF samples from seven of 10 were initially drawn through indwelling devices and those from nine of 10 were obtained by subsequent lumbar punctures. All of these patients were treated with antifungals, although therapy was delayed in 50% of cases until the second positive culture was reported. In 11 cases, Candida was the only isolate recovered from CSF samples drawn through indwelling devices; cultures of subsequent CSF samples obtained by lumbar puncture were negative in 10 of 11 cases. Only two patients for whom a single culture was positive for Candida species were treated with antifungals (both of whom were symptomatic), and none of the untreated patients died of infection. The clinical significance of a single positive CSF sample drawn through an indwelling device is difficult to assess, and a definitive diagnosis may require repeated cultures of CSF samples obtained by lumbar puncture.