The Role of Interventional Radiology in the Diagnosis and Treatment of Pulmonary Arteriovenous Malformations

Pulmonary arteriovenous malformations (PAVMs) are uncommon, predominantly congenital direct fistulous connections between the pulmonary arteries and pulmonary veins, resulting in a right to left shunt. Patients with PAVMs are usually asymptomatic with lesions detected incidentally when radiological imaging is performed for other indications. In this review, we discuss the classification and radiological features of PAVMs as well as their treatment and follow-up options, with a particular focus on percutaneous endovascular techniques and the evolution of the available equipment for treatment.

Spontaneous hemopneumothorax: Our experience with surgical management

Background

Spontaneous hemopneumothorax is rare, accounting for only 1%–12% of patients presenting with spontaneous pneumothorax. The optimal management of these patients remains controversial with no definitive guidelines on patient selection and timing of surgery. The aim of this study was to review our institution’s surgical experience in the management of patients with spontaneous hemopneumothorax.

Methods

We performed a retrospective review of all patients with spontaneous hemopneumothorax who underwent surgery from January 2000 to June 2013. Patient data were obtained from our institution’s primary spontaneous pneumothorax database.

Results

Of 510 patients who underwent surgery for spontaneous pneumothorax, 33 (6.4%) developed spontaneous hemopneumothorax. The mean age was 24.0 years (range 16–40 years). In 30 (90.9%) patients, it was their first presentation of pneumothorax. There were 25 (75.8%) patients with Vanderschueren stage III spontaneous pneumothorax. Blood loss ranged from 250 to 3000 mL (mean 1280 mL). In 28 patients, a torn adhesion band was the source of bleeding. Thoracotomy was the surgical approach in 9 (27.3%) patients, and video-assisted thoracic surgery was used in 24 (72.7%). One patient required reoperation for retained clots. There was no mortality.

Conclusion

Our results suggest that surgical management of spontaneous hemopneumothorax can be undertaken with minimal morbidity and mortality. With the increasing use of video-assisted thoracic surgery, definitive surgical management of spontaneous hemopneumothorax can be instituted earlier.

The pattern of utilisation and accuracy of a commercial nucleic acid amplification test for the rapid diagnosis of Mycobacterium tuberculosis in routine clinical practice

BACKGROUND

Several nucleic acid amplification (NAA) tests are available for the rapid detection of Mycobacterium tuberculosis (MTB) in clinical specimens.

AIMS

To identify the pattern of utilisation and accuracy of the AMPLICOR test in routine clinical practice in an acute care setting.

DESIGN

A retrospective descriptive study.

METHOD

We studied 159 consecutive specimens in which the AMPLICOR (Roche; Branchburg, NJ) test was requested by attending doctors. The sensitivities and specificities of the AMPLICOR for detection of active tuberculosis (TB) were calculated in relation to types of specimens, smear and culture results.

RESULTS

The number of requests more than doubled from 1999 to 2000. Thirty-eight percent of the specimens were not from the respiratory tract. The majority of the specimens had requests for one or more additional test (mean 1.8). The rate of active TB was 18%. The sensitivities of the AMPLICOR on per specimen, per patient, per smear negative specimen and per smear negative patient basis were found to be 81%, 80%, 66.7% and 71.4% respectively. The specificities for these groups accordingly were 99%, 98.6%, 99% and 98.6% respectively. The sensitivity and specificity for respiratory specimens were 97.5% and 98.5%, while for non-respiratory specimens, they were 60% and 100%. In smear negative specimens, the sensitivity and specificity for respiratory specimens were 60% and 98.5%, while for non-respiratory specimens, they were 75% and 100%. The AMPLICOR assay was negative in all 21 specimens of pleural or spinal fluid.

CONCLUSIONS

There is a growing demand for NAA in the rapid diagnosis of TB with a high proportion of non-respiratory specimens. The number of additional diagnostic tests performed on each specimen should be limited. In routine clinical practice, the AMPLICOR assay is a useful confirmatory test for active pulmonary TB. The utility of the AMPLICOR assay for MTB detection in exudative fluid specimens needs further evaluation.

The activity of a combination of penicillin and novobiocin against bovine mastitis pathogens: development of a disk diffusion test

The combination of penicillin and novobiocin is currently available for the treatment of bovine mastitis, but methods are not available for susceptibility testing of the combination by veterinary diagnostic laboratories. The minimum inhibitory concentration (MIC) and disk diffusion data were determined for penicillin, novobiocin, and a combination of the two in a 1:2 ratio for 225 staphylococcal, streptococcal, and Gram-negative isolates from bovine intramammary infections. Based on the drug concentrations in milk following infusion, linear regression analysis, and error rate bounding, the interpretive zone diameters selected were < or = 16 mm for resistant isolates and > or 17 mm for susceptible isolates with a disk containing 10 U of penicillin and 30 micrograms of novobiocin. Additionally, MIC breakpoints of < or = 2 micrograms/ml of penicillin and 4 micrograms/ml of novobiocin were selected to categorize isolates as susceptible and > or = 4 micrograms/ml of penicillin and 8 micrograms/ml of novobiocin were selected to categorize isolates as resistant. The MIC and disk diffusion results, as well as studies to monitor bacterial killing by antimicrobial agents over time, indicated that the combination of penicillin and novobiocin in a 1:2 ratio was more active than were the individual drugs. Kinetics of the kill curves with the penicillin and novobiocin combination (1:2 ratio) showed that the combination was bactericidal for Staphylococcus aureus and Staphylococcus xylosus.

A mechanism of rifamycin inhibition and resistance in Pseudomonas aeruginosa

We sought to study the nature of rifampicin resistance in Pseudomonas aeruginosa. We hypothesized that the rifamycin regions of RNA polymerase are conserved in P. aeruginosa and that rifampicin resistance is mediated by a mutation in the rpoB gene encoding the beta subunit of RNA polymerase. Transcription assays showed that 50 nM of rifampicin inhibited transcription > 99% in a clinical isolate (MIC = 32 mg/L) and only < 40% in the rifampicin resistant mutant (MIC = 1000 mg/L). DNA sequencing revealed that the rifampicin regions are conserved in P. aeruginosa and the rifampicin regions of the rifampicin-resistant strain contained a mutation. Sodium hexametaphosphate lowered rifamycin MIC in a rifamycin-resistant mutant four-fold and in the clinical isolate 32-fold, suggesting that P. aeruginosa has a natural membrane barrier to rifamycins.

Comparative activity of eight antimicrobial agents against clinical bacterial isolates from the United States, measured by two methods

In a surveillance study conducted during 1992-1993 at 83 medical institutions of different types and sizes (e.g., laboratories, community hospitals, teaching hospitals) and from different geographical areas of the United States, clinical bacterial isolates were tested for their susceptibility to eight comparative antimicrobial agents (cefepime, ceftazidime, cefotaxime, ceftriaxone, ciprofloxacin, gentamicin, imipenem, and piperacillin). A total of 12,574 isolates were tested by either the Etest method (AB Biodisk) or a microdilution method (MicroScan) in the participating laboratories; 11.8% of these isolates were subsequently retested for quality assurance purposes by both methods in a central laboratory. The results obtained in the central laboratory were essentially the same as the results obtained in the participating laboratories. This article presents data for gram-negative and gram-positive isolates other than Streptococcus pneumoniae, the results of which have been previously published. Antimicrobial susceptibility results obtained with the two different minimum inhibitory concentration (MIC) methods--MicroScan and Etest--showed that most isolates of Enterobacteriaceae were susceptible to cefepime, exceeding the activity of ceftazidime, ceftriaxone, and cefotaxime, principally because of the greater activity of cefepime against the species that produce Bush group 1 beta-lactamases (predominantly Enterobacter cloacae, Enterobacter aerogenes, and Citrobacter freundii). In addition, the activity of cefepime against Pseudomonas aeruginosa isolates was essentially equivalent to that of ceftazidime and greater than that of third-generation cephalosporins. Most methicillin-susceptible Staphylococcus aureus were susceptible to all the cephalosporins, whereas methicillin-resistant S. aureus and enterococci were resistant. Overall, the most active antimicrobials in this study were imipenem, ciprofloxacin, and cefepime, but the activity of all the antimicrobials varied with different species. Categorically, the results from the microdilution and Etest methods were equivalent.

A comparative study of the in-vitro activity of cefepime and other antimicrobial agents against penicillin-susceptible and penicillin-resistant Streptococcus pneumoniae

Using the national surveillance programme of USA hospitals, we selected 162 strains of Streptococcus pneumoniae for sensitivity testing using the NCCLS breakpoints for benzylpenicillin and the oxacillin discs screen test. Included in the group of isolates were 85 relatively penicillin-resistant and 33 penicillin-resistant strains. The activity of cefepime, a new cephalosporin, was compared with other cephalosporins and penicillins as well as some non-beta-lactam antimicrobials. Imipenem was the most active agent but, cefepime, cefotaxime, ceftriaxone and ciprofloxacin were only slightly less active. The least active agents were ceftazidime, cefuroxime, piperacillin/tazobactam and ticarcillin/clavulanate. Cefepime is a potential alternative treatment to penicillin, particularly when penicillin-resistant and relatively penicillin-resistant S. pneumoniae are encountered. The clinical importance of screening for penicillin resistance by the use of the oxacillin disc is emphasized.

In-vitro activity of cefepime and other antimicrobials: survey of European isolates

Cefepime, a new cephalosporin which has a broad-spectrum of activity was tested in vitro against 1961 Gram-positive and Gram-negative clinical isolates obtained from European hospitals. Cefepime was highly active against Gram-negative organisms, inhibiting over 94% of strains tested. The overall susceptibility rate for cefepime against all isolates was 81%. Cefepime was more active than any of the third-generation cephalosporins tested against species capable of producing type I beta-lactamases, e.g. Enterobacter cloacae, Citrobacter freundii, and Enterobacter aerogenes. The activity of cefepime against Pseudomonas aeruginosa was similar to that of ceftazidime and substantially greater than those of cefotaxime and ceftriaxone. All cephalosporins except ceftazidime exhibited high activity against methicillin-susceptible Staphylococcus aureus but poor activity was observed against methicillin-resistant strains. Overall susceptibility to cefepime is lower in Europe than it is in North America.

Molecular epidemiology of endemic ciprofloxacin-susceptible and -resistant Enterobacteriaceae

OBJECTIVES

To elucidate the epidemiology of widespread ciprofloxacin resistance in our Veterans Affairs medical center using whole cell DNA analysis.

DESIGN

In vitro study of ciprofloxacin resistant and susceptible Enterobacteriaceae isolated during the course of a clinical epidemiologic study of quinolone resistance.

SETTING

Veterans Affairs Medical Center with acute care and long-term care divisions.

RESULTS

We examined 40 ciprofloxacin-resistant strains of Serratia marcescens, Proteus mirabilis, and Providencia stuartii using restriction endonuclease analysis of whole cell DNA and compared them with concomitantly isolated ciprofloxacin sensitive strains. We sought to determine whether resistant strains were identical to susceptible strains, indicating in vivo emergence of resistant strains from susceptible strains, and whether resistant strains were shared among patients. All 26 ciprofloxacin-resistant S marcescens isolates shared a single ecoRI restriction pattern. Multiple patterns were seen in the ciprofloxacin-susceptible S marcescens isolates; however, several isolates had a pattern matching that of the resistant isolates. Similar results were seen among the P mirabilis isolates. Three different ecoRI patterns were found among the ciprofloxacin-resistant P stuartii isolates; none matched those found among the susceptible isolates. The frequency of spontaneous emergence of ciprofloxacin resistance in susceptible S marcescens strains with restriction pattern matching that of the resistant strains was significantly higher than that of nonmatching strains.

CONCLUSIONS

Ciprofloxacin-resistant strains of Enterobacteriaceae became widespread within a short period of time. Resistant strains of S marcescens and P mirabilis arose from endemic susceptible strains. The resistant strain of S marcescens appeared to arise from a susceptible strain with a relatively high frequency of spontaneous ciprofloxacin resistance.

Isolation of Legionella pneumophila serogroup 5 from empyema following esophageal perforation. Source of the organism and mode of transmission

A patient undergoing esophageal dilatation for carcinoma of the esophagus suffered esophageal perforation and development of an empyema. Culture of pleural fluid yielded multiple organisms, including Legionella pneumophila serogroup 5. Epidemiologic investigation showed that the source of L pneumophila was a tap used by the nursing personnel to fill patients' water pitchers. Whole-cell restriction endonuclease analysis of DNA from the clinical and environmental isolates of L pneumophila serogroup 5 yielded identical patterns. Our findings suggest that L pneumophila was acquired by the patient at least 12 h prior to the procedure causing the esophageal perforation and empyema, suggesting that the organism can persist in an infectious form in the upper aerodigestive tract.

Staphylococcus epidermidis bacteremia from transfusion of contaminated platelets: application of bacterial DNA analysis

Septicemia is a rare complication of platelet transfusion. A case is reported of transfusion-associated septicemia in a 66-year-old man who received a 10-unit pool of platelets. During transfusion, he experienced rigors, wheezing, dyspnea, and fever. A total of four blood cultures drawn 10 and 36 hours after discontinuation of the transfusion grew Staphylococcus epidermidis. Culture of the residual platelet pool yielded S. epidermidis with a colony count of 10(5) organisms per mL. Strain identity of all four blood isolates and the platelet pool isolate was confirmed by gel electrophoresis of EcoRI and HindIII restriction digests of whole-cell DNA. There have been 31 prior reported cases of platelet transfusion-associated septicemia, of which 9 have been caused by coagulase-negative staphylococci. Systemic reactions to platelet transfusions should prompt consideration of transfusion-associated bacteremia as the cause.

Legionella pneumophila in residential water supplies: environmental surveillance with clinical assessment for Legionnaires' disease

Although cases of community-acquired Legionnaires' disease have been epidemiologically linked to residential water supplies, the risk of acquiring Legionnaires' disease from exposure to Legionella pneumophila in residential water systems is uncertain. The residential water supplies of 218 members of the American Legion in six different geographical areas in Pittsburgh were cultured for L. pneumophila. Residents of the homes provided a recent medical history and a blood sample for detection of antibodies to legionella. A urine sample for legionella urinary antigen testing was also requested from individuals residing in legionella-positive homes and individuals with a positive antibody test. Six percent (14/218) of the homes yielded L. pneumophila (range within six areas 0-22%). Lower hot water tank temperature was significantly associated with legionella positivity (P less than 0.01). Analysis of water samples for mineral content showed no association between legionella positivity and concentrations of calcium and magnesium. Water samples from the area where 22% of the homes surveyed were positive for legionella had a higher iron content than water samples from the other areas tested. None of the individuals residing in legionella-positive homes showed elevated antibody titres to legionella or the presence of legionella antigen in urine. For the immunocompetent hosts, the risk of contracting Legionnaires' disease from exposure to contaminated household water supplies in the Pittsburgh area appears to be low.

Methicillin-resistant staphylococcal colonization and infection in a long-term care facility

OBJECTIVE

To determine the natural history of colonization by methicillin-resistant Staphylococcus aureus (MRSA) among patients in a long-term care facility. We specifically sought to determine if MRSA colonization was predictive of subsequent infection.

DESIGN

Cohort study.

SETTING

Long-term Veterans Affairs Medical Center.

PATIENTS

A total of 197 patients residing on two units were followed with regular surveillance cultures of the anterior nares.

MAIN OUTCOME MEASUREMENT

The development of staphylococcal infection.

RESULTS

Thirty-two patients were persistent carriers of MRSA and 44 were persistent carriers of methicillin-susceptible strains (MSSA). Twenty-five percent of MRSA carriers had an episode of staphylococcal infection compared with 4% of MSSA carriers and 4.5% of non-carriers (P less than 0.01; relative risk 3.8; 95% CI, 2.0 to 6.4). The rate of development of infection among MRSA carriers was 15% for every 100 days of carriage. Using logistic regression analysis, persistent MRSA carriage was the most significant predictor of infection (P less than 0.001; odds ratio, 3.7). Seventy-three percent of all MRSA infections occurred among MRSA carriers. Isolates of MRSA from 7 patients were typed. Colonizing and infecting strains had the same phage type in all 7 patients and the same pattern of plasmid EcoRI restriction endonuclease fragments in 5 patients.

CONCLUSIONS

Colonization of the anterior nares by MRSA predicts the development of staphylococcal infection in long-term care patients; most infections arise from endogenously carried strains. Colonization by MRSA indicates a significantly greater risk for infection than does colonization by MSSA. The results offer a theoretic rationale for reduction in MRSA infections by interventions aimed at eliminating the carrier state.

Legionnaires' disease in the work environment: implications for environmental health

Legionnaires' disease is a severe pneumonia caused by the bacterium Legionella pneumophila. Outbreaks of Legionnaire's disease have occurred in hotels, hospitals, and homes but had not been reported yet in the work environment. The authors report the occurrence of Legionnaires' disease in three employees of two industrial plants. The potable water in the two plants contained high numbers of Legionella pneumophila. Monoclonal antibody subtyping of environmental and patient isolates of L. pneumophila implicated one of the plants as the source for the disease. L. pneumophila was eradicated from this plant using acidic and caustic scale removers, calcium hypochlorite, and a biocide. A systematic approach to Legionnaires' disease in the work environment, a problem which can be expected to be recognized with increasing frequency, is presented.

Discovery of occult legionella pneumonia in a long stay hospital: results of prospective serological survey

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Interaction between rifampin and fusidic acid against methicillin-resistant coagulase-positive and -negative staphylococci

We studied the interaction between rifampin and fusidic acid against a group of staphylococci. Of the 20 coagulase-positive strains studied, checkerboard studies revealed synergy in 3 and indifference in 17; time-kill studies revealed synergy in 18 of 19 coagulase-positive strains at both 24 and 48 h. Of the 19 coagulase-negative strains, checkerboard studies revealed synergy in 6 and indifference in 13; time-kill studies revealed synergy in 6 of 18 coagulase-negative strains at 24 h and in 17 of 18 coagulase-negative strains at 48 h. The combination of rifampin and fusidic acid warrants further evaluation in the therapy of staphylococcal disease.