Non-multiresistant and multiresistant methicillin-resistant Staphylococcus aureus in community-acquired infections.

OBJECTIVE: To survey Staphylococcus aureus strains isolated from patients presenting from the community, comparing clinical features and antibiotic sensitivity profiles between multiresistant and non-multiresistant methicillin-resistant and methicillin-sensitive isolates. DESIGN: Retrospective case series. PARTICIPANTS AND SETTING: Patients who presented to emergency or dermatology departments in hospitals served by the South Western Sydney Area Health Service between 1 May 1998 and 30 April 1999. All patients with methicillin-resistant S. aureus (MRSA) and the first 100 with methicillin-sensitive S. aureus were eligible. MAIN OUTCOME MEASURES: Patient demographic characteristics; risk factors; clinical presentation; treatment; outcome; and isolate antibiotic susceptibility. RESULTS: 139 patients were eligible, and 122 had clinical records available. Ten of these 122 (8%) had multiresistant MRSA, 26 (21%) non-multiresistant MRSA and 86 (70%) methicillin-sensitive S. aureus. Among patients with non-multiresistant MRSA, 29% (7/24) were born in New Zealand, Samoa or Tonga, a higher proportion than among those with multiresistant MRSA or methicillin-sensitive S. aureus (P= 0.03). Nearly half (44%) of non-multiresistant MRSA strains were community-acquired in patients with no risk factors. Two-thirds of patients with non-multiresistant MRSA (17/26) presented with cellulitis or abscess, and 58% (11/19 evaluable patients) required surgical treatment. CONCLUSIONS: Non-multiresistant MRSA strains are common, especially among people born in New Zealand, Samoa or Tonga, and are usually community acquired. Medical practitioners should routinely swab all staphylococcal lesions for culture and sensitivity.

Community-acquired, non-multiresistant oxacillin-resistant Staphylococcus aureus (NORSA) in South Western Sydney.

Community-acquired oxacillin-resistant Staphylococcus aureus (ORSA) infections are an emerging problem in the 1990s in Sydney, Australia. Laboratory data pertaining to all specimens that grew S. aureus between 1/1/1990 and 31/12/1999 were analysed. A total of 12,909 isolates of S. aureus were obtained. The proportions that were nonmultiresistant oxacillin-resistant S. aureus (NORSA) increased from 0.09% in 1990 to 5.5% in 1999. Resistance of NORSA strains to erythromycin was 8.5%, ciprofloxacin 8.4%, tetracycline 13%, rifampicin 0.7%, and fusidic acid 5.3%. A chart review was performed for cases of NORSA infection which occurred 1/1/1998-3/5/1998. Isolates from these cases underwent E-test oxacillin MIC testing, mecA determinant PCR, phage typing and pulsed-field gel electrophoresis. All nine of the patients with NORSA were Polynesians, and all had serious soft tissue infections. Bacteraemia was not seen. Only one patient received vancomycin yet all recovered. Isolates from all nine patients contained the mecA determinant. Oxacillin MICs were 1-8 mg/l. Strain differentiation with phage typing and pulsed-field gel electrophoresis showed isolates from eight patients were closely related and were similar to New Zealand WSPP1 and WSPP2 strains. Medical practitioners should take specimens for culture and sensitivity from lesions where infection with S. aureus is likely. Empirical treatment of staphylococcal infections in Polynesians needs to cover NORSA. Methods to detect oxacillin resistance need to be robust.

Neonatal pneumococcal sepsis in association with fatal maternal pneumococcal sepsis.

A live male infant was born at 37 weeks' gestation after a normal pregnancy to a 34-year-old mother. The baby developed bacteraemia with Streptococcus pneumoniae and recovered completely following treatment with antibiotics. The mother simultaneously developed bacteraemia with the same organism and died from septic shock. Blood culture isolates from mother and child were both serogroup 23F, and were shown to be identical by DNA fingerprinting. The literature reports rare cases of vaginal carriage and/or endometritis with this organism resulting in neonatal sepsis. Transmission to the neonate may have been ascending or haematogenous. A postmortem examination was refused.

Evaluation of the MRSA-Screen Test in detecting oxacillin resistance in community and hospital isolates of Staphylococcus aureus.

The MRSA-Screen Test (Denka Seiken Co., Japan), a latex agglutination test to detect penicillin-binding protein 2a, was compared with PCR for the detection of oxacillin resistance in Staphylococcus aureus. A total of 77 oxacillin-sensitive and 269 oxacillin-resistant (ORSA) isolates were evaluated. Of the ORSA isolates, 186 were non-multiresistant (NORSA), defined as being resistant to two or fewer antibiotics other than beta-lactams. Eighty-three were multiresistant ORSA (MORSA) strains. If PCR is considered the gold standard test, then the sensitivity, specificity, positive and negative predictive values of the MRSA-Screen Test were 100, 99, 99 and 100%, respectively. The endpoint was hard to read with NORSA strains that took longer than 60 s to react. MORSA strains took a median 12 s (range 5-60 s) to give a positive reaction with the MRSA-Screen Test, whereas NORSA strains took a median 30 s (range 5-180 s), a difference which was significantly different (P < 0.0001, two-tailed Mann-Whitney unpaired two sample test). NORSA strains had an MIC50 of 128 mg/l and MIC90 of 256mg/l, whereas MORSA strains had an MIC50 and MIC90 of >256mg/l. The time that the MRSA-Screen Test took to agglutinate with ORSA strains correlated weakly with the MIC (r2 = 0.26). Detection of methicillin resistance cost AUD$9 per isolate with the MRSA-Screen Test, compared with AUD$13 per isolate with mecA PCR. The MRSA-Screen Test gave excellent sensitivity and specificity, and was quicker and cheaper than PCR. The full 3 min should be allowed to elapse before calling a test negative. Organisms giving indeterminate reactions should be tested for the mecA gene by PCR.

Detection and serogroup determination of Neisseria meningitidis in CSF by polymerase chain reaction (PCR).

A PCR protocol for the detection and serogroup determination of Neisseria meningitidis in CSF from 85 cases of suspected meningitis was evaluated. Screening assays for both IS1106 and the ctrA gene were used to detect meningococcal DNA, and a further two assays using the siaD gene were performed to determine the serogroup. PCR results were compared with results of bacteriological culture and discrepant results resolved by analysis of clinical data and further laboratory test results. The resolved sensitivity and specificity of the PCR screening assay were 89 and 100%, and those of bacteriological culture were 37 and 100%, respectively. The siaD B/C PCR assay was able to determine a serogroup in 85% of cases positive by the PCR screening assay compared with 50% of cases where a serogroup was determined by traditional methods. PCR is a useful tool for diagnosis of meningococcal meningitis when Gram stain and culture tests are negative, a situation that may arise when antibiotic treatment has commenced prior to lumbar puncture.

A comparison between the inlet and outlet diameters of the normal aortic valve.

Two studies are described comparing the inlet and outlet diameters of the normal aortic valve. Both studies show the valve inlet to be smaller than the valve outlet. The first study is of measurements made on 12 casts of physiologically pressurised human aortic valves. The mean ratio between the diameter of the aortic ring and of the aorta just distal to the sinus ridge was 1.1, and the mean ratio between the diameter of the aortic ring and the maximum diameter of the valve leaflets was 1.18. The second study presents echocardiographic data from normal volunteers. The mean ratio between the diameter of the aortic ring and of the aorta just distal to the sinus ridge was 1.17. It is suggested that stents made to support the leaflets of prosthetic valves are made in conical or hyperbolic form, with the outlet being approximately 20% larger than the inlet.

Mitral valve replacement in patients with severe mitral regurgitation and impaired left ventricular function.

We have studied short- and mid-term effects of preservation and excision of the mitral subvalvar support during mitral valve replacement in 40 patients, who had developed moderate to severe degree of left ventricular function impairment, secondary to pure severe mitral regurgitation. These patients had valve replacement, because valve anatomy was unsuitable for reconstructive procedures. Mitral subvalvar support was excised and valve replaced with a Björk-Shiley prosthesis, in 10 patients with moderately impaired left ventricular ejection fraction (mean 32% +/- 1.2%) and in 18 patients with severely impaired left ventricular function (left ventricular ejection fraction: 22% +/- 0.8%). In 12 patients with severely impaired left ventricular function (left ventricular ejection fraction: 20% +/- 1%) posterior subvalvar apparatus was preserved and valve replaced with a bioprosthesis. Prognosis of patients with moderately impaired left ventricular function was not influenced by the loss of chordopapillary support. Actuarial survival at 8 and 10 years was 46% +/- 7.8% for patients with severely impaired left ventricular function with chordopapillary support excised and 70% +/- 10% for patients with severely impaired left ventricular function with chordopapillary support preserved (p less than 0.01). Preservation of mitral subvalvar support is important in patients with severely impaired left ventricular function (left ventricular ejection fraction less than 25%).

Functional tricuspid regurgitation following replacement of the mitral valve.

In this series, the effect of replacement of the mitral valve was examined in 86/900 (9.6%) patients who had developed moderate functional tricuspid regurgitation, secondary to rheumatic mitral valvar disease. These patients were subdivided according to the severity of pulmonary hypertension and impairment of right ventricular function. Forty-six patients presented with severe pulmonary hypertension and 40 patients had moderate pulmonary hypertension (mean main pulmonary arterial pressure: 78 +/- 14 mmHg vs 41 +/- 6 mmHg; P less than 0.05). The latter had more advanced disease, greater impairment of right ventricular function and dilatation of the right heart chambers. Functional tricuspid regurgitation regressed in 38/42 survivors with severe pulmonary hypertension and persisted or progressed significantly in 22/34 survivors with impaired right ventricular function despite successful replacement of the mitral valve. The latter underwent replacement of the tricuspid valve (n = 16) or tricuspid annuloplasty (n = 6), at a mean interval of 44 +/- 4.4 months after replacement of the mitral valve, which resulted in 8/22 (23.5%) early deaths. Functional tricuspid regurgitation is more likely to persist in patients with advanced right ventricular failure. Tricuspid valvar competence should be restored in these patients at initial replacement of the mitral valve.

Combined mitral and aortic valve replacement with Bjørk-Shiley prostheses: long term survival and valve-related complications.

Between 1974 and 1985, combined aortic and mitral valve replacement (DVR) was performed in 209 patients using Bjørk-Shiley tilting-disc prostheses. Early and late mortality were 9.5% and 10.5% respectively for the entire series. Factors significantly influencing early mortality were: Emergency DVR, preoperative NYHA Class IV, double valve, critical stenosis, and small aortic replacement prostheses. The effect of the latter was augmented by the suboptimal orientation of the implanted prostheses. The overall survival was 74 +/- 4.4% at 12 years; but was only 40 +/- 6.1% at 8 years in patients who were in NYHA class IV preoperatively. Intermittent disc occlusion (DO) and thrombotic disc occlusion (TO), presented as early, anticoagulant related haemorrhage (AH) and prosthetic valve endocarditis (ENDO) as sporadic, and thromboembolism (TE) and paravalvular leak (PVL) as continuous risk factors. Freedom from all known valve-related complications was 77 +/- 4.5% at 12 years (DO, TO, AH, ENDO, TE, PVL: 98%, 97%, 96%, 96%, 88% and 89% respectively). Lethal DO and TO occurred in mitral prostheses. Freedom from reoperation was 95% at 5 and 12 years. Patient-related valve failure rate in this series is comparable with the other series which used mechanical prostheses and is lower than those which used bioprostheses.

Tricuspid valve replacement: factors influencing early and late mortality.

Seventy four patients underwent tricuspid valve replacement (TVR), between 1968 and 1983. 93% were female, mean age was 44 +/- 4 years. Tricuspid valve was replaced with a mechanical prosthesis in 52 and a bioprosthesis in 22 patients. Fifty seven patients underwent primary TVR and 17 underwent a secondary TVR following a mean interval of 41 +/- 2 months (SEM) following a previous mitral or tricuspid valve operation. Preoperatively 86% patients were in NYHA class III-IV and congestive cardiac failure (CHF). Early mortality for primary TVR was 36.8% and 35.2% for secondary TVR. Early mortality has been significantly reduced since the introduction of cardioplegic protection for the associated valve lesions. Early mortality was significantly influenced by the reduced preoperative values of FVC and FEV1 in patients with long standing mitral valve disease and by raised preoperative levels of plasma bilirubin and alkaline phosphate in patients with CHF. Risk of thrombotic occlusion and late deaths remained high during the first year after TVR with a mechanical prosthesis.

The results of surgery for atrial septal defect in patients aged fifty years and over.

We examined the cases of 31 patients over the age of 50 years undergoing operative closure of isolated ostium secundum atrial septal defect. The lesion had been diagnosed in all cases prior to cardiac catheterization. To assess the importance of pre-operative data on surgical outcome, the patients were first divided into three groups according to mean pulmonary artery pressure (PAP): less than 16 mmHg (Group A), 16-30 mmHg (Group B) and greater than 30 mmHg (Group C). Symptomatic improvement occurred in all groups but more patients in Group C, although symptomatically improved, remained short of breath and in atrial fibrillation than in Group A. Patients in Group A had a higher actual forced vital capacity expressed as a percentage of the predicted value (FVCa/FVCp) than patients in Group B or Group C (P less than 0.015). There was a good correlation between FVCa/FVCp and percentage oxygen saturation of the arterial blood (P less than 0.0009). This simple non-invasive investigation was therefore found to correlate with previously documented parameters, pulmonary artery pressure and percentage oxygen saturation of the arterial blood, affecting surgical outcome. Patients were also divided into groups according to FVCa/FVCp: less than 75% (Group 1), 50-75% (Group 2) and less than 50% (Group 3). Postoperative symptoms were more common in Group 3 than in Group 1. We conclude that respiratory function tests, as well as measurement of pulmonary artery pressures, are useful in predicting improvement following atrial septal repair.

Late results of aortic valve replacement with Bjork Shiley prostheses: a comparison of standard aortic valve prosthesis with reversed mitral valve prosthesis implanted in aortic position.

Between 1976 and 1983, 435 patients underwent aortic valve replacement (AVR) with Bjork Shiley prostheses. Standard aortic Bjork Shiley prostheses (ABP) were used in 150 patients (Group I) and a reversed mitral Bjork Shiley prostheses in 285 (MBP in 250 and MBC in 35) patients (Group II). There was no significant difference in the number of the patients with valve calcification or the size of aortic root in the 2 groups. There was no significant difference in the early mortality in these two groups. The total follow up period in Group I was 912 years and 2130 years in Group II. The incidence of major aseptic prosthetic dehiscence and valve occlusion with tissue ingrowth were higher in Group I than in Group II. Reversed Bjork Shiley mitral valve prosthesis was successfully used in aortic position with reduced incidence of valve related complications.

Plasma albumin and calcium levels following cardiopulmonary bypass.

A significant fall in the levels of plasma albumin and a corresponding fall i in the levels of extracellular calcium occurred following cardiopulmonary bypass with the crystalloid prime. Postoperative hypoalbuminaemia was well tolerated, except in the patients with poor left ventricular function. Postoperative hypocalcaemia may increase digoxin sensitivity and may augment the negative inotropic effect of verapamil.

A modified technique for mitral valve replacement.

Between 1976 and 1983 254 mitral valve prostheses (243 Björk-Shiley and 14 bioprostheses) were implanted in 252 patients using a modified technique. The age of patients varied from 26-72 years (mean 56 +/- 18 years). This technique allows an equidistant placement of sutures and accurate stitching of mitral valve annulus to the prosthetic valve ring. Follow-up averaged 67 +/- 21.6 months (3-7 years). Linearized aseptic dehiscence was 0.17 per 100 patient years. This technique was especially useful in patients with small left atrium and minimised the risk of a major prosthetic detachment.

Late results of total correction of tetralogy of Fallot in adults.

Between 1966 and 1986, 30 patients underwent total correction of the tetralogy of Fallot. Preoperative presenting features were: dyspnoea on exertion, clubbing, cyanosis and polycythaemia. Twenty-six patients had one or more palliative procedures prior to definitive repair. Preoperatively, all patients had a significant gradient across the right ventricular outflow tract (mean gradient 70 +/- 46 mmHg). Peak right ventricle to left ventricle systolic pressure ratio (pRV/LV) was 0.9 +/- 0.2. A functioning Blalock Taussig shunt was ligated in 11 patients prior to the institution of cardiopulmonary bypass. All patients had a patch closure of the ventricular septal defect. An additional muscle bundle resection from the right ventricular outflow tract was performed in 15, pulmonary valvotomy in 6 and enlargement of the right ventricular outflow tract in 2 patients. There was a significant fall in pRV/LV ratio postoperatively (P less than 0.05). There were 3 early and 2 late deaths. Mild right ventricular outflow tract obstruction has persisted in all survivors. Four patients have remained on antiarrhythmic drugs. Long term results after definitive repair were satisfactory in this group of adult patients who have survived due to palliative procedures performed during childhood.

Re-operation for aortic and mitral prosthetic dysfunctions.

The overall incidence of re-operation and prosthetic valve endocarditis was low in the present series as mechanical prostheses were used predominantly. The prosthetic dysfunctions were less frequent following the primary implantation with Bjork Shiley prostheses, but high operative risk was associated with the clotted Bjork Shiley prostheses. We also had unusual experience of strut fracture and sticking of Bjork Shiley discs in the closed position in both aortic and mitral positions. The early deaths were nil since the use of cardioplegic protection. Intra-operative bleeding due to adhesions can be minimised by using synthetic or heterologous pericardium during the primary operation.