Evaluation of the Haemophilus influenzae EUCAST and CLSI disc diffusion methods to recognize aminopenicillin and amoxicillin/clavulanate resistance.

OBJECTIVES: Implementation of EUCAST susceptibility testing in an Australian hospital laboratory demonstrated higher rates of aminopenicillin and amoxicillin/clavulanate resistance in Haemophilus influenzae than previously recognized. This study aimed to better define the variability in the detection of ß-lactam resistance based on EUCAST and CLSI disc diffusion (DD) methodology, by comparison with the recommended reference method, broth microdilution (BMD), and by concordance with genomic analysis. METHODS: A total of 100 random H. influenzae isolates were assessed for ampicillin and amoxicillin/clavulanate susceptibility by EUCAST and CLSI DD and BMD. WGS was used to analyse the ftsI gene of a subset of isolates with ß-lactam resistance, other than that due to isolated ß-lactamase production. RESULTS: Of the 100 isolates, 32 were categorized as either ß-lactamase negative, ampicillin resistant (BLNAR) (n = 18) or ß-lactamase positive, amoxicillin/clavulanate resistant (BLPACR) (n = 14) by EUCAST DD. All 18 EUCAST BLNAR isolates were genotypically confirmed by WGS. Five of 18 BLNAR isolates were concordant by CLSI DD, 12 by EUCAST BMD and 4 by CLSI BMD. Nine of 14 EUCAST BLPACR isolates were confirmed by WGS; the remaining 5 were 1 mm below the EUCAST DD breakpoint. Only one isolate was detected as BLPACR by CLSI DD. Group III mutations associated with high-level ampicillin resistance were identified in 10/32 isolates. CONCLUSIONS: The EUCAST DD susceptibility method is more reliable than either CLSI or BMD for the detection of genotypically defined BLNAR resistance. However, accurate categorization of amoxicillin/clavulanate resistance remains problematic. Continuous and reproducible surveillance of resistance is needed; for this to be possible, robust susceptibility methods are required.

Optimal phenotypic testing of AmpC beta-lactamases using boronic acid solutions.

Plasmid-mediated class C ß-lactamases are reported from Escherichia coli and Klebsiella pneumoniae with increasing frequency. No screening and confirmatory tests have been uniformly established for these strains. We investigated for the presence of plasmid-mediated AmpC production in 51 clinical isolates of Enterobacteriaceae, comparing two different boronic acid formulations, phenylboronic acid (PB) and 3-(N-Boc-amino)phenylboronic acid (APB), using polymerase chain reaction (PCR). PB performed better than APB.

Admitting service influences the outcomes of patients with small bowel obstruction.

BACKGROUND: Small bowel obstruction (SBO) is a common problem that often requires operation. We tested the hypotheses that patients admitted to a surgical service have improved outcomes and that these outcomes are related to early operation. METHODS: Retrospective review of 281 patients with 336 episodes of SBO between 1992 and 1998 was performed. Parametric and nonparametric analysis was used as appropriate. RESULTS: There were 222 admissions to a surgical service and 114 admissions to a medical service. Patient characteristics were similar between groups. Eighty-seven percent of patients had a previous abdominal or pelvic operation. There were 211 patients (217 admissions) who required operation. Operated patients admitted to the surgical service had a shorter preoperative (2.7 vs 6.3 days, P <.01) and overall length of stay (LOS) (17.9 vs 22.8 days, P <.0001). There was no difference in time to resumption of diet between groups. The number of previous admissions or operations did not affect the need for operative intervention. Unoperated patients admitted to a medical service had a shorter time to resumption of diet (3.1 vs 4.3 days) and LOS (4.8 vs 7.2 days, both P <.05) than the surgical service group. Operative mortality was 3.4%. The likelihood of developing a complication was related to the occurrence of an enterotomy (n = 21, odds ratio = 2.69; 95% confidence interval [CI]: 1.1-6.7, P =.014) or the need for bowel resection (odds ratio = 1.97; 95% CI: 1.2-3.5, P =.02). The occurrence of a complication resulted in a 46% increase in LOS (P <.0001). Patients operated on within 24 hours of admission had a decreased LOS (P <.05) and mortality, with no difference in the occurrence of postoperative complications. CONCLUSIONS: Patients with SBO who require operation benefit from a shorter time to operation and reduced LOS when admitted to a surgical service. Early operation is associated with a reduction in mortality, and avoidance of enterotomy decreases the risk of complications.

Prospective randomized trials affect the outcomes of intraabdominal infection.

OBJECTIVE: To compare the characteristics and outcomes of patients with intraabdominal infections enrolled in prospective randomized trials (PRTs) with those of a cohort of patients not enrolled in a trial. SUMMARY BACKGROUND DATA: Prospective randomized trials are the gold standard for the evaluation of new treatments. Patients are screened using rigorous eligibility criteria and sometimes are excluded from PRTs because of associated medical conditions or more severe illness. However, the effect that the exclusion of these patients has on the applicability of clinical trial outcomes has not been defined. METHODS: One hundred sixty-eight adults with intraabdominal infection were treated at a single institution during 7 years. Fifty-three patients were enrolled in four PRTs comparing various antibiotic regimens for treatment; 115 were not enrolled. Patient characteristics and outcomes of these two groups were compared. RESULTS: Patients with infections from appendicitis (n = 68) had a low severity of illness and similar outcomes in both groups. These patients and those for whom a concurrent PRT was unavailable were excluded from subsequent analysis. Eighty-eight patients (42 PRT, 46 not enrolled) with serious infection remained for analysis. Patients enrolled in PRTs were younger, had less severe illness, had a decreased length of stay, a lower incidence of antibiotic resistance, and less frequent extraabdominal infections than those not enrolled in a trial. Patients enrolled in PRTs were more likely to be cured and were less likely to die. Logistic regression analysis demonstrated that cure was associated with a lower initial severity of illness, absence of antibiotic resistance, and participation in a PRT. CONCLUSIONS: Patients with intraabdominal infection enrolled in PRTs have an increased likelihood of cure and survival. This is due in part to a lower incidence of antibiotic resistance, which may reflect improved drug selection. Patients not enrolled in PRTs are at greater risk for treatment failure and death because of concomitant illness. Outcomes from PRTs may not be applicable to all patients with intraabdominal infections.

New chromogenic identification and detection of Staphylococcus aureus and methicillin-resistant S. aureus.

This paper describes a new chromogenic plate medium, CHROMagar Staph aureus (CHROMagar, Paris, France), for the identification of Staphylococcus aureus on the basis of colony pigmentation. The abilities of CHROMagar Staph aureus, thermostable nuclease (DNase), and mannitol salt agar (MSA) to identify S. aureus isolates (n = 114) and discriminate between S. aureus and coagulase-negative staphylococci (CoNS; n = 22) were compared. CHROMagar Staph aureus proved to be more sensitive and specific than DNase and MSA, allowing a reliable, simple, and rapid method for the identification of S. aureus isolates. All CoNS encountered in this study with the exception of S. chromogenes could be easily differentiated from S. aureus on this medium. The supplementation with 4 microgram of oxacillin or methicillin per ml allowed simple identification of methicillin resistance in hospital-acquired S. aureus strains which show multiple-drug resistance profiles. Community-acquired methicillin-resistant S. aureus strains showing non-multi-drug resistance profiles require further evaluation on this new chromogenic medium. Methicillin or oxacillin resistance of all S. aureus isolates was confirmed by the detection of penicillin-binding protein 2a, encoded by the mecA gene, using the latex slide agglutination MRSA-Screen test (PBP 2' Test, DR900M; Oxoid).

A comparison of ventricular function during high right ventricular septal and apical pacing after his-bundle ablation for refractory atrial fibrillation.

This study compares LV performance during high right ventricular septal (RVS) and apical (RVA) pacing in patients with LV dysfunction who underwent His-bundle ablation for chronic AF. We inserted a passive fixation pacing electrode into the RVA and an active fixation electrode in the RVS. A dual chamber, rate responsive pulse generator stimulated the RVA through the ventricular port and the RVS via the atrial port. Patients were randomized to initial RVA (VVIR) or RVS (AAIR) pacing for 2 months. The pacing site was reversed during the next 2 months. At the 2 and 4 month follow-up visit, each patient underwent a transthoracic echocardiographical study and a rest/exercise first pass radionuclide ventriculogram. We studied nine men and three women (mean age of 68 +/- 7 years) with congestive heart failure functional Class (NYHA Classification): I (3 patients), II (7 patients), and III (2 patients). The QRS duration was shorter during RVS stimulation (158 +/- 10 vs 170 +/- 11 ms, P < 0.001). Chronic capture threshold and lead impedance did not significantly differ. LV fractional shortening improved during RVS pacing (0.31 +/- 0.05 vs 0.26 +/- 0.07, P < 0.01). RVS activation increased the resting first pass LV ejection fraction (0.51 +/- 0.14 vs 0.43 +/- 0.10, P < 0.01). No significant difference was observed during RVS and RVA pacing in the exercise time (5.6 +/- 3.2 vs 5.4 +/- 3.1, P = 0.6) or the exercise first pass LV ejection fraction (0.58 +/- 0.15 vs 0.55 +/- 0.16, P = 0.2). The relative changes in QRS duration and LV ejection fraction at both pacing sites showed a significant correlation (P < 0.01). We conclude that RVS pacing produces shorter QRS duration and better chronic LV function than RVA pacing in patients with mild to moderate LV dysfunction and chronic AF after His-bundle ablation.

Modifying risk for extracorporeal circulation: trial of four antiinflammatory strategies.

BACKGROUND: Despite recent rediscovery of beating heart cardiac surgical techniques, extracorporeal circulation remains appropriate for most heart operations. To minimize deleterious effects of cardiopulmonary bypass, antiinflammatory strategies have evolved. METHODS: Four state-of-the-art strategies were studied in a prospective, randomized, preoperatively risk stratified, 400-patient study comprising primary (n = 358), reoperative (n = 42), coronary (n = 307), valve (n = 27), ascending aortic (n = 9), and combined operations (n = 23). Groups were as follows: standard, roller pump, membrane oxygenator, methylprednisolone (n = 112); aprotinin, standard plus aprotinin (n = 109); leukocyte depletion, standard plus a leukocyte filtration strategy (n = 112); and heparin-bonded circuitry, centrifugal pumping with surface modification (n = 67). RESULTS: Analysis of variance, linear and logistic regression, and Pearson correlation were applied. Actual mortality (2.3%) was less than half the risk stratification predicted mortality (5.7%). The treatment strategies effectively attenuated markers of the inflammatory response to extracorporeal circulation. Compared with the other groups the heparin-bonded circuit had highly significantly decreased complement activation (p = 0.00001), leukocyte filtration blunted postpump leukocytosis (p = 0.043), and the aprotinin group had less fibrinolysis (p = 0.011). Primary end points, length of stay, and hospital charges, were positively correlated with operation type, age, pump time, body surface area, stroke, pulmonary sequelae, predicted risk for stroke, predicted risk for mortality, and risk strata/treatment group interaction (p = 0.0001). In low-risk patients, leukocyte filtration reduced length of stay by 1 day (p = 0.02) and mean charges by $2,000 to $6,000 (p = 0.05). For high-risk patients, aprotinin reduced mean length of stay up to 10 fewer days (p = 0.02) and mean charges by $6,000 to $48,000 (p = 0.0007). CONCLUSIONS: These pharmacologic and mechanical strategies significantly attenuated the inflammatory response to extracorporeal circulation. This translated variably into improved patient outcomes. The increased cost of treatment was offset for selected strategies through the added value of significantly reduced risk.

Chromogenic tube test for presumptive identification or confirmation of isolates as Candida albicans.

This report describes a new, modified, simple, and cost-effective method for the use of CHROMagar Candida (CHROMagar Company, Paris, France) for the presumptive identification of isolates as Candida albicans after preliminary growth. Sixty randomly selected clinical isolates were evaluated, including 38 of C. albicans. With incubation at 37 degrees C for 24 h, the sensitivity and specificity appeared to be excellent and the test performed better than the traditional germ tube test. However, at earlier times, C. tropicalis isolates gave false-positive results.

Application of lipovitellin-salt-mannitol agar for screening, isolation, and presumptive identification of Staphylococcus aureus in a teaching hospital.

Lipovitellin-salt-mannitol (LSM) plate medium was examined for its ability to directly isolate, recover, and presumptively identify Staphylococcus aureus from 418 clinical specimens. The criteria for medium evaluation included colony morphology reactions, selectivity, and ease of isolation. For 298 specimens used for screening, LSM agar medium was compared with the other conventional media used, mannitol salt agar (MSA), 5% horse blood agar (HBA), and phenolphthalein phosphate agar (PPA), to detect and recover S. aureus and methicillin-resistant S. aureus. The results indicated that LSM agar is more effective than MSA, HBA, or PPA for the recovery and isolation of S. aureus and methicillin-resistant S. aureus. On a replicator multipoint inoculation system, we compared the reactions on LSM agar, MSA, and DNase agar of 227 different strains of staphylococci, which included 178 different strains of S. aureus and 49 different strains of coagulase-negative staphylococci isolated from clinical specimens. By using the lipovitellin precipitation activity and mannitol fermentation characteristics, LSM agar gave a 100% correlation in presumptively identifying S. aureus. LSM agar may be an alternative plate medium for large hospital extensive screening for the detection and isolation of S. aureus.

Evaluation of CHROMagar Orientation for differentiation and presumptive identification of gram-negative bacilli and Enterococcus species.

A new chromogenic plate medium, CHROMagar Orientation, was evaluated for use in the differentiation and presumptive identification of gram-negative bacilli and Enterococcus species by a multipoint inoculation (replicator) technique. In this study, 1,404 gram-negative bacilli and 74 enterococcal isolates were tested on CHROMagar Orientation. Six control American Type Culture Collection strains were also included with the testing to ensure quality control of the media. Of the Escherichia coli isolates (n = 588) tested, 99.3% produced a pink-to-red color. Only in four isolates that were O-nitrophenyl-beta-D-galactopyranoside (ONPG) negative did this result differ. Proteus mirabilis and P. vulgaris were well differentiated on this medium. P. mirabilis (n = 184) produced a clear colony with diffusible brown pigment around the periphery. By contrast, 15 of 16 P. vulgaris isolates produced bluish-green colonies with a slight brown background. All Aeromonas hydrophila isolates (n = 26) tested produced clear to pink colonies at 35 to 37 degrees C. This colony color changed to blue after 2 to 3 h of incubation at room temperature. A. hydrophila exhibited stronger color and better growth at 30 degrees C. Serratia marcescens (n = 29) demonstrated an aqua blue color that deepened to a darker blue when exposed to room temperature. All enterococcal isolates (n = 74) resulted in a blue color and gave pinpoint colonies on purity subcultures at 35 to 37 degrees C after 18 h of incubation. Similarity in color resulted in failure to discriminate accurately between Klebsiella, Enterobacter, and Citrobacter species. However, these species could be readily differentiated from other members of the family Enterobacteriaceae. Pseudomonas aeruginosa (n = 151) was easily differentiated from members of the Enterobacteriaceae but was less easily distinguishable from other gram-negative nonmembers of the Enterobacteriaceae. The medium was found to facilitate easy visual detection of mixed bacterial isolates in culture. When used in a replicator system, it easily detected mixed growths of organisms which may have otherwise led to false antibiotic susceptibility results. These mixed growths were not obvious on the routine susceptibility testing medium (Isosensitest).

Successful behavioral intervention to treat children who are reluctant to ambulate.

The authors report two patients with marginal ambulation skills whose severe behavioral problems prevented participation in physical therapy. The problem behavior also limited the patients' participation in activities of daily living and social interaction. Because of the risks of loss of ambulation to overall health, an aggressive behavioral intervention was implemented to decrease problem behavior and to increase participation in physical therapy. With the use of the behavioral interventions, the authors demonstrated concomitant increases in compliance to requests to ambulate, distances ambulated, and decreases in the rates of self-injury and aggression.

Absence of defects in SPECT thallium-201 myocardial images in patients with systemic hypertension and left ventricular hypertrophy.

Hypertension is common in patients undergoing stress and delayed single-photon emission computed tomography (SPECT) thallium-201 myocardial perfusion imaging. Investigators have reported that patients with end-stage renal disease and left ventricular hypertrophy due to hypertension have diminished lateral/septal count ratios on stress and delayed imaging mimicking lateral myocardial infarction in approximately 35% of patients. Subsequently, hypertension has been cited as a frequent cause of thallium-201 artifacts. The purpose of this study was to compare myocardial SPECT thallium-201 distribution in a broader group of patients with left ventricular hypertrophy resulting from hypertension with normal file subjects in order to determine the prevalence of abnormal studies and to compare the lateral/septal count ratio. Average counts in all myocardial regions in the male study group (n = 16) were compared with those in the normal male file patients (n = 49), with particular attention to the lateral and septal walls. In the group of 16 men with hypertension and left ventricular hypertrophy, as a whole, the mean lateral/septal wall count ratio was 4.4% lower (1.09 +/- 0.07) than that in the normal file (1.14 +/- 0.07; p < 0.01). At 3-hour delay, the ratio was virtually the same in the study group (1.06 +/- 0.09) as in the normal file (1.08 +/- 0.06; p = NS). Most important, for clinical purposes no patient had a defect, defined as a lateral/septal count ratio > 2.0 SD below normal limits. All thallium-201 studies were interpreted as normal. In conclusion, myocardial thallium-201 distribution is normal in patients with left ventricular hypertrophy due to hypertension.

Diagnosis of main-stem pulmonary thromboemboli by transesophageal echocardiography.

The aim of this report is to describe the usefulness of transesophageal echocardiography in the diagnosis of pulmonary emboli. A biplane transesophageal probe was used to examine the pulmonary artery in multiple views in three patients with suspected pulmonary emboli. The diagnosis of pulmonary emboli was made by transesophageal echocardiography in each of three patients when an echodense, circular or linear mass was seen in more than one view of the main or right pulmonary artery. In conclusion, our findings, coupled with previous case reports, suggest that transesophageal echocardiography should be considered in all critically ill patients with suspected pulmonary emboli.