A pseudo-outbreak of disseminated cryptococcal disease after orthotopic heart transplantation

Cryptococcal infection is the third most common invasive fungal infection (IFI) among solid-organ transplant (SOT) recipients and is considered an important opportunistic infection due to its significant morbidity and mortality. To determine whether a cluster of cryptococcosis in heart transplant patients was of nosocomial nature, three cases of orthotopic heart transplant recipients with postoperative disseminated cryptococcal infection were investigated and paired with an environmental survey in a tertiary care hospital. The infection prevention department conducted a multidisciplinary investigation, which did not demonstrate any evidence of health care-associated environmental exposure. Moreover, multilocus sequence typing showed that one isolate was unique and the two others, although identical, were not temporally related and belong to the most common type seen in the Southern US. Additionally, all three patients had preexisting abnormalities of the CT chest scan and various degrees of acute and chronic rejection. Reactivation was suggested in all three patients. Screening methods may be useful to identify at risk patients and trigger a prophylactic or preemptive approach. However, more data is needed.

Cerebral perfusion pressure for prediction of recurrent intracranial hypertension after primary decompressive craniectomy

BACKGROUND

Decompressive craniectomy (DC) with dural grafting may be performed in patients with moderate (Glasgow-Coma-Scale [GCS] score 9-12 points) or severe traumatic brain injury (TBI; GCS score <or= 8 points) and threatening herniation. However, its effectiveness especially after primary craniectomy is still discussed due to missing evidence of improved outcome. The objectives of this study were to show the incidence of recurrent intracranial hypertension after primary DC, to identify predictive parameters for secondary DC, and to evaluate the long-term neurological performance 12 months after TBI.

METHODS

Between 01/1997 and 06/2001 all consecutive patients admitted with moderate or severe isolated TBI were enrolled in this study. They were treated according to the guidelines of the European Brain Injury Consortium, and the American Association of Neurosurgical Surgeons (AANS) for the management of severe TBI. Process and clinical data as well as every intervention were registered prospectively. The long-term neurological status was reassessed using the Glasgow Outcome Score (GOS) 12 months after TBI. Statistical comparison was performed using Mann-Whitney-U test, and multivariate testing by means of logistic regression analysis.

RESULTS

Fifty-one (43 males, 8 females; median age 51.4 years) of 119 isolated TBI patients were included. Ten patients (8 males, 2 females; median age 38.4 years) underwent secondary extended or contralateral DC in their clinical course. Three of them (30%) died at a median of 1 day after revision respectively 6 days after TBI. According to univariate analysis, secondary DC significantly correlated with arterial hypotension (p = 0.020) and otorrhagia at admission (p = 0.041), skull base fracture (p = 0.011) and decreased maximum cerebral perfusion pressure (CPP; p = 0.006) after primary surgery. Multivariate analysis identified decreased maximum CPP as the only independent predictive parameter (p = 0.036) for secondary DC and unfavourable GOS after 12-months follow-up.

CONCLUSION

Arterial hypotension, otorrhagia at admission and skull base fractures are negatively influencing the mortality and morbidity of patients with isolated moderate or severe TBI. However, only decreased maximum CPP may independently indicate secondary DC after primary craniectomy in case of recurrent intracranial hypertension.

[Capsule endoscopy: indication, diagnosis and patient management in the doctor's office]

In this prospective clinical study, 50 consecutive patients in whom there was an indication for capsule endoscopy were evaluated with regard to indication, examination course, outcome and modifications to patient management, and the data obtained analysed. In 88% of the patients, capsule endoscopy revealed pathological changes. Patient management was modified in 78% of the cases.

Networks and tuberculosis: an undetected community outbreak involving public places

After decades of decline in developed countries, there was a resurgence of tuberculosis in the mid-1980s accompanied by increased recognition that this infectious disease has long remained a major public health problem at the global level. New methods from molecular biology, in particular DNA 'fingerprinting' (of Mycobacterium tuberculosis), made it clear that current transmission and recent infection (in contrast to reactivation of earlier, latent infection) were much more significant than previously believed. Studies of tuberculosis outbreaks using these new tools pointed to complex networks through which infection was spreading and highlighted the need for new approaches to outbreak investigation and disease control. In the study reported here a new approach--combining methods from molecular biology, epidemiology and network analysis--was used to examine an outbreak of tuberculosis in Houston, Texas. Initial investigation using conventional strategies revealed few contacts among 37 patients with identical (six-band) DNA (IS6110-based) fingerprints but subsequent research uncovered over 40 places (including many gay bars) to which patients in this outbreak could be linked. Network methods were used to reconstruct an outbreak network and to quantify the relative importance (here, 'betweenness' centrality) of different actors (persons and places) playing a role in the outbreak. The multidisciplinary work provides the basis for a new approach to outbreak investigation and disease control.

Evaluation of Etest for susceptibility testing of multidrug-resistant isolates of Mycobacterium tuberculosis

To prescribe effective treatment schemes for patients with tuberculosis, more-efficient susceptibility testing techniques for Mycobacterium tuberculosis are needed, especially in regions with multidrug resistance. Etest (AB BIODISK, Solna, Sweden) is a simple technique that provides quantitative drug susceptibility results for M. tuberculosis in 5 to 10 days from a culture grown at low cost. The performance of Etest was compared to that of the reference proportion method, using 95 M. tuberculosis clinical isolates of which 42.1% (40 of 95) were resistant to at least one antibiotic by the reference method. Overall agreement between Etest and the reference method was 98.9% (94 of 95) for detection of multidrug resistance; for resistance to individual drugs, agreement was 97.9% (93 of 95) for rifampin, 96.0% (92 of 95) for ethambutol, 94.7% (90 of 95) for isoniazid, and 85.3% (81 of 95) for streptomycin. This study supports the utility of Etest for timely detection of drug resistance in M. tuberculosis and for use in tuberculosis control programs.

Multisite reproducibility of Etest for susceptibility testing of Mycobacterium abscessus, Mycobacterium chelonae, and Mycobacterium fortuitum

A multicenter study was conducted to assess the inter- and intralaboratory reproducibility of the Etest for susceptibility testing of the rapidly growing mycobacteria. The accuracy also was evaluated by comparing Etest results to those obtained by broth microdilution. Ten isolates (four of the Mycobacterium fortuitum group, three of Mycobacterium abscessus, and three of Mycobacterium chelonae) were tested against amikacin, cefoxitin, ciprofloxacin, clarithromycin, doxycycline, imipenem, and trimethoprim-sulfamethoxazole in each of four laboratories. At each site, isolates were tested three times on each of three separate days (nine testing events per isolate) using common lots of media and Etest strips. Interlaboratory agreement among MICs (i.e., mode +/- 1 twofold dilution) varied for the different drug-isolate combinations and overall was best for trimethoprim-sulfamethoxazole (75% for one isolate and 100% for all others), followed by doxycycline and ciprofloxacin. Interlaboratory agreement based on interpretive category also varied and overall was best for doxycycline (100% for all isolates), followed by trimethoprim-sulfamethoxazole and ciprofloxacin. Interlaboratory reproducibility among MICs was most variable for imipenem, and agreement by interpretive category was lowest for imipenem and amikacin. Modal Etest MICs agreed with those by broth microdilution only for doxycycline and the sulfonamides. For all other drugs, the modal MICs by the two methods differed by more than +/- 1 twofold dilution for one or more isolates. In all cases, the Etest MIC was higher and would have caused reports of false resistance. In summary, the Etest in this evaluation did not perform as well as broth microdilution for susceptibility testing of the rapidly growing mycobacteria. It was problematic for most species and drugs, primarily because of a trailing endpoint and/or high MICs compared to broth. Its use will necessitate further investigation, including determination of the optimal medium and incubation conditions and clarification of endpoint interpretation.

Complex transmission dynamics of clonally related virulent Mycobacterium tuberculosis associated with barhopping by predominantly human immunodeficiency virus-positive gay men

Limited data suggest that measures to reduce tuberculosis transmission should be based on locations rather than on personal contacts. Molecular epidemiologic methods (analysis of IS6110 patterns, spoligotypes, variable numbers of tandem DNA repeats, and automated DNA sequence data) identified a cohort of 48 persons who were infected with progeny of the same Mycobacterium tuberculosis strain. Epidemiologic investigation documented that a large proportion of the patients were gay white human immunodeficiency virus-positive men. Most practiced barhopping, an activity that involved patronizing many bars in the same neighborhood each night. Few subjects were directly linked to more than 1 or 2 other persons by conventional investigation methods, which shows that the transmission dynamics were unusually complex compared with most previously described episodes of strain spread. The data support the concept that identification of locations where pathogen dissemination likely occurs may provide additional strategies for targeted tuberculosis control.

Multisite reproducibility of results obtained by the broth microdilution method for susceptibility testing of Mycobacterium abscessus, Mycobacterium chelonae, and Mycobacterium fortuitum

A multicenter study was conducted to assess the interlaboratory reproducibility of broth microdilution testing of the more common rapidly growing pathogenic mycobacteria. Ten isolates (four Mycobacterium fortuitum group, three Mycobacterium abscessus, and three Mycobacterium chelonae isolates) were tested against amikacin, cefoxitin, ciprofloxacin, clarithromycin, doxycycline, imipenem, sulfamethoxazole, and tobramycin (M. chelonae only) in four laboratories. At each site, isolates were tested three times on each of three separate days (nine testing events per isolate) with a common lot of microdilution trays. Agreement among MICs (i.e., mode +/- 1 twofold dilution) varied considerably for the different drug-isolate combinations and overall was best for cefoxitin (91.7 and 97.2% for one isolate each and 100% for all others), followed by doxycycline, amikacin, and ciprofloxacin. Agreement based on the interpretive category, using currently suggested breakpoints, also varied and overall was best for doxycycline (97.2% for one isolate and 100% for the rest), followed by ciprofloxacin and clarithromycin. Reproducibility among MICs and agreement by interpretive category was most variable for imipenem. Based on results reported from the individual sites, it appears that inexperience contributed significantly to the wide range of MICs of several drugs, especially clarithromycin, ciprofloxacin, and sulfamethoxazole. New interpretive guidelines are presented for the testing of M. fortuitum against clarithromycin; M. abscessus and M. chelonae against the aminoglycosides; and all three species against cefoxitin, doxycycline, and imipenem.

Clindamycin resistance among erythromycin-resistant Streptococcus pneumoniae

The increasing proportion of Streptococcus pneumoniae isolates with reduced susceptibility to penicillin has created an urgent need for therapeutic alternatives to some beta-lactam agents. Clindamycin is an antimicrobial agent with excellent bioavailability after oral administration which has been considered for the therapy of community-acquired pneumococcal otitis media. Using the Etest methodology, we have studied the in vitro susceptibility of 59 erythromycin-resistant strains of S. pneumoniae to clindamycin, penicillin, trimethoprim-sulfamethoxazole, and rifampin. The study also addressed the impact of the susceptibility test medium [Mueller-Hinton (MH) vs IsoSensitest (Iso), both 5% blood supplement] on the results. A total of 20 isolates (37%) displayed constitutive clindamycin resistance on Iso blood agar, compared with only 11 (22%) on MH blood agar. The remaining nine strains found to be clindamycin susceptible on MH manifested resistance only with erythromycin induction. Resistance to penicillin, rifampin, and trimethoprim-sulfamethoxazole in erythromycin-resistant isolates was 83%, 2%, and 85%-89% (medium dependent), respectively. These results indicate that the choice of susceptibility test medium affects the expression (constitutive or inducible) of macrolide-lincosamide-streptogramin (MLS) resistance in S. pneumoniae. In addition, the common assumption that erythromycin resistance in S. pneumoniae implies clindamycin resistance may need to be reconsidered and routine susceptibility tests (including induction if MH medium is used) should be considered for MLS-class drugs.

Proposed MIC quality control guidelines for National Committee for Clinical Laboratory Standards susceptibility tests using seven veterinary antimicrobial agents: ceftiofur, enrofloxacin, florfenicol, penicillin G-novobiocin, pirlimycin, premafloxacin, and spectinomycin

The present multicenter study proposes broth microdilution quality control (QC) ranges for the antimicrobial agents ceftiofur, enrofloxacin, florfenicol, penicillin G-novobiocin, pirlimycin, premafloxacin, and spectinomycin, which are used in veterinary practice. Six separate laboratories tested replicates of National Committee for Clinical Laboratory Standards (NCCLS)-recommended QC organisms (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 29213, and Enterococcus faecalis ATCC 29212) on medium lots both common and unique to all laboratories. The proposed ranges were within 3 or 4 log2 dilution steps of the modal MICs for all organism-antimicrobial agent pairs, depending on their MIC distributions. With > or = 94.7% of all MIC results being within the proposed QC ranges, all combinations tested comply with NCCLS guidelines and all have been accepted by the NCCLS subcommittee developing susceptibility testing procedures for veterinary laboratories.

Testing of Mycobacterium tuberculosis susceptibility to ethambutol, isoniazid, rifampin, and streptomycin by using Etest

Etest (AB BIODISK, Solna, Sweden) is a precise MIC method and the practical method of choice for the susceptibility testing of many fastidious organisms, including rapidly growing mycobacteria. Methods recommended by the National Committee for Clinical Laboratory Standards for the susceptibility testing of Mycobacterium tuberculosis include the Bactec (Becton Dickinson, Sparks, Md.) broth and agar proportion methods. A comparison of Etest with the Bactec broth method for testing the susceptibility of M. tuberculosis to four first-line antituberculous agents demonstrated equivalent interpretive results for 100% of the isolates tested. Agreements with agar proportion MICs, within +/-2 log2 dilutions, were 90, 93, 100, and 94% for ethambutol, isoniazid, rifampin, and streptomycin, respectively. Etest MICs were easily read within 5 to 10 days of inoculation. Preparation of the inoculum with a turbidity equivalent to a McFarland 3.0 standard prepared from growth on an agar surface and with a broth with a Bactec growth index of > 999 yielded equivalent results. Clinical isolates for which the MICs were reproducible were also identified as possible quality control strains. The Etest method appears to be an alternative method for testing the susceptibility of M. tuberculosis isolates to the four most commonly used therapeutic agents.

Comparison of Etest and National Committee for Clinical Laboratory Standards broth macrodilution method for antifungal susceptibility testing: enhanced ability to detect amphotericin B-resistant Candida isolates

The National Committee for Clinical Laboratory Standards (NCCLS) proposed macrobroth reference method (M27P) for susceptibility testing of yeasts is technically difficult. We evaluated Etest, a simple agar-based MIC methodology, as a possible alternative. In studies of six yeast quality control strains, Etest yielded results identical to those obtained by the NCCLS reference method for both amphotericin B and fluconazole. In studies of 91 clinical Candida isolates, agreement +/- 2 dilutions between the two methods was 95% for fluconazole with phosphate-buffered RPMI 1640 agar and 96 to 97% for amphotericin B with either MOPS (morpholinepropanesulfonic acid)-buffered RPMI 1640 agar or antibiotic medium 3 agar. While the two methods had excellent general agreement, testing of a collection of amphotericin B-resistant isolates demonstrated that, unlike the NCCLS reference method, Etest readily identified the resistant isolates and could do so with a defined medium. Etest is equivalent to the NCCLS proposed method for susceptibility testing of yeasts and superior in its ability to detect amphotericin B resistance.

Evaluation of a commercial rRNA amplification assay for direct detection of Mycobacterium tuberculosis in processed sputum

A commercial assay (Amplified Mycobacterium tuberculosis Direct Test, Gen Probe) which combines transcription-mediated amplification of target rRNA with amplicon detection by a chemiluminescent DNA probe for the rapid detection of Mycobacterium tuberculosis in sputum was evaluated. The test was applied to consecutively collected, NALC/NaOH processed sputum sediments from two laboratories (H and L), each serving a different population of patients with pulmonary tuberculosis. Results were compared to those of fluorochrome staining and culture. A total of 760 specimens obtained from 246 patients were used for the study. The test was positive in 141 of 144 (98%) specimens that were fluorochrome-positive and culture-positive for Mycobacterium tuberculosis. Fifteen of 31 specimens that were fluorochrome-negative, culture-positive were also assay-positive. A total of 312 specimens (100 patients) from laboratory H (prevalence = 10%) and 448 specimens (146 patients) from laboratory L (prevalence = 34%) were analyzed. Compared to culture, test sensitivity, specificity, positive predictive and negative predictive values were 65%, 99%, 94% and 97%, respectively, for laboratory H and 93%, 99%, 99% and 97%, respectively, for laboratory L. If the results were analyzed on the basis of at least one concordant result between the amplification assay and culture in three sputum samples per patient, then the sensitivity, specificity, positive and negative predictive values for identifying infected patients was 70%, 99%, 87% and 97%, respectively, for laboratory H, and 100%, 98%, 96% and 100%, respectively, for laboratory L.

Etest for susceptibility testing of Mycobacterium tuberculosis and Mycobacterium avium-intracellulare

Methods currently used for susceptibility testing of Mycobacterium, including agar dilution and the Bactec radiometric method, are based on the proportion technique using a single critical concentration of antibiotic. Preliminary studies were conducted with Mycobacterium species by using the Etest method, a gradient minimum inhibitory concentration technique, well described for susceptibility testing of other fastidious and slow-growing organisms. Excellent correlation was demonstrated between Etest and agar dilution with rifampin-susceptible and -resistant isolates of M. tuberculosis and ciprofloxacin-resistant and -susceptible isolates of Mycobacterium avium-intracellulare.

Characterization by automated DNA sequencing of mutations in the gene (rpoB) encoding the RNA polymerase beta subunit in rifampin-resistant Mycobacterium tuberculosis strains from New York City and Texas

Automated DNA sequencing was used to characterize mutations associated with rifampin resistance in a 69-bp region of the gene, rpoB, encoding the beta subunit of RNA polymerase in Mycobacterium tuberculosis. The data confirmed that greater than 90% of rifampin-resistant strains have sequence alterations in this region and showed that most are missense mutations. The analysis also identified several mutant rpoB alleles not previously associated with resistant organisms and one short region of rpoB that had an unusually high frequency of insertions and deletions. Although many strains with an identical IS6110 restriction fragment length polymorphism pattern have the same variant rpoB allele, some do not, a result that suggests the occurrence of evolutionary divergence at the clone level.

Molecular epidemiology of beta-lactamase-producing enterococci

Plasmids from the first six reported beta-lactamase-producing (Bla+) enterococci were compared for genetic relatedness. Bla+ enterococcal plasmids from strains isolated in Houston, Tex.; Philadelphia, Pa.; Connecticut; and Pittsburgh, Pa., had heterogeneous HaeIII and MspI-ClaI restriction endonuclease digestion patterns. A staphylococcal beta-lactamase probe hybridized to all six Bla+ enterococcal plasmids, but hybridization was detected on different HaeIII and MspI-ClaI fragments of the six plasmids. An enterococcal gentamicin resistance (Gmr) probe hybridized to a common 3.9-kilobase HaeIII fragment from the five Gmr plasmids. The Houston plasmid was cross-hybridized to the other five strains, and moderate to extensive homology was demonstrated. Bla+ enterococcal plasmids from a broad geographic range are heterogeneous with respect to size and restriction endonuclease digestion patterns but contain homologous genetic material, including Bla+ and Gmr determinants.

Escherichia coli O114:nonmotile as a pathogen in an outbreak of severe diarrhea associated with a day care center

Five infants from a day care center developed severe diarrhea associated with enteropathogenic Escherichia coli O114:nonmotile (EPEC O114:NM) and required hospitalization. Five additional cases of diarrhea associated with EPEC O114:NM subsequently occurred, four in hospital contacts of the patients and one in a household contact. Biochemically, all EPEC O114:NM isolates were sorbitol nonfermenters. All isolates produced low concentrations of cytotoxin with a mean of 10(1.23) CD50/mg of protein. Cytotoxin was not neutralized with antibody to Shiga-like toxin I or II. Heat-labile and heat-stable enterotoxins were not present by gene probe analysis. Stool isolates from 9 of 10 hospitalized infants were positive for EPEC adherence factor by colony blot DNA probe analysis. The severity of the disease, sorbitol nonfermentation, and presence of enteroadherence are unusual features of this organism.

Quantitative analysis and partial characterization of cytotoxin production by Salmonella strains

The pathogenesis of the wide-spectrum human disease caused by Salmonella species is poorly understood. Cytotoxin production by other enteric pathogens has been increasingly investigated recently, and data are accumulating regarding the role of cytotoxins in enteric infections and hemolytic uremic syndrome. We studied the cytotoxic activity of 131 Salmonella strains of the major serotypes, including 94 strains of Salmonella enteritidis, 12 strains of Salmonella typhi, and 25 strains of Salmonella choleraesuis. Cytotoxicity was quantitatively determined in sonic extracts by a [3H]thymidine-labeled HeLa cell assay. All Salmonella strains examined showed some degree of cytotoxic activity. The geometric means +/- standard deviations of the amounts of cytotoxin produced (50% cytotoxic dose per milligram of bacterial protein) were 27 +/- 2 for S. typhi, 65 +/- 2 for S. enteritidis, and 117 +/- 2 for S. choleraesuis. Analysis of variance showed that the differences in cytotoxin production by the three species were significant (P less than 0.001). No significant differences were found between stool isolates and invasive strains of the same species. Neutralization studies showed that the cytotoxins produced by all Salmonella strains were immunologically distinct from Shiga toxin and the closely related Shiga-like toxins produced by Escherichia coli. DNA hybridization studies with DNA probes for Shiga-like toxins of types I and II showed no hybridization. In each species the cytotoxin was heat labile and sensitive to trypsin treatment, which indicated that its active component was probably protein in nature. Upon ultrafiltration with Amicon membranes and gel filtration chromatography, cytotoxic activity was found in the molecular weight range of 56,000 to 78,000. Our findings indicate that salmonellae produce cytotoxin(s) that may play a role in the manifestations of the various species.

Comparison of two beta-lactamase-producing strains of Streptococcus faecalis

A second strain of enterococcus (PA) producing beta-lactamase (Bla+ phenotype) was compared with the previously reported Bla+ enterococcus, strain HH22. As with the original strain, there was a marked inoculum effect when PA was tested with penicillin, ampicillin, and piperacillin; no difference was noted with methicillin, cephalothin, imipenem, or vancomycin; the difference with ticarcillin was intermediate. High-level gentamicin resistance (Gmr) transferred from PA to an enterococcal recipient strain at a frequency approximately 100-fold lower than for HH22; all Gmr transconjugants from both strains were Bla+, but only PA showed linkage of Gmr and Bla+ with transfer of resistance to streptomycin, tetracycline, and chloramphenicol. EcoRI digestion of plasmid DNA from Gmr Bla+ transconjugants showed no similarities between the two strains. A 5.1-kilobase EcoRI Bla+-encoding fragment derived from HH22 was cloned into an Escherichia coli cloning vector and shown to hybridize to a 10.2-kilobase EcoRI fragment derived from PA; both fragments hybridized to an 840-base-pair staphylococcal Bla+ gene probe. These data indicate that the penicillinases are similar but encoded on different or differently arranged plasmids. The fact that both are transferable emphasizes the potential for this new streptococcal resistance determinant to disseminate.