A snapshot of the biodiversity and clustering of Mycobacterium tuberculosis in Oman using spoligotyping.

SETTINGS: National Tuberculosis Reference Laboratory, Central Public Health Laboratory, Ministry of Health, Oman. OBJECTIVE: To use spoligotyping to explore the genetic population structure and clustering of Mycobacterium tuberculosis isolates among nationals and immigrants in Oman. METHODS: Using spoligotyping, we characterised all available isolates from 2007, and randomly selected isolates from 2005 and 2006. A total of 312 clinical isolates from the same number of patients diagnosed with tuberculosis (TB) in 2005-2007 were included in the study. RESULTS: Of 312 isolates, 69% were in clusters ranging from 2 to 38 isolates. The proportion of clustering was 58% among 2005-2006 samples and 67% among 2007 samples, with higher clustering among Omanis than among immigrants. The study showed that M. tuberculosis Indian family lineages, CAS1_Delhi, CAS and EAI5 were the predominant strains. Around 50% of the immigrants shared strains with Omanis. Twelve of the 19 INH-monoresistant strains and the two multidrug-resistant strains were in clusters (P = 0.81). CONCLUSION: This study demonstrates the predominance in Oman of the strain family commonly found on the Indian sub-continent. A high proportion of immigrant strains were in the same clusters as Omani strains. To better ascertain the transmission dynamics of M. tuberculosis, we recommend that stringent molecular and conventional epidemiological methods be applied.

Changes in the FEV1/FVC ratio during childhood and adolescence: an intercontinental study.

In children, the ratio of forced expiratory volume in 1 s (FEV1) to forced vital capacity (FVC) is reportedly constant or falls linearly with age, whereas the ratio of residual volume (RV) to total lung capacity (TLC) remains constant. This seems counter-intuitive given the changes in airway properties, body proportions, thoracic shape and respiratory muscle function that occur during growth. The age dependence of lung volumes, FEV1/FVC and RV/TLC were studied in children worldwide. Spirometric data were available for 22,412 healthy youths (51.4% male) aged 4-20 yrs from 15 centres, and RV and TLC data for 2,253 youths (56.7% male) from four centres; three sets included sitting height (SH). Data were fitted as a function of age, height and SH. In childhood, FVC outgrows TLC and FEV1, leading to falls in FEV1/FVC and RV/TLC; these trends are reversed in adolescence. Taking into account SH materially reduces differences in pulmonary function within and between ethnic groups. The highest FEV1/FVC ratios occur in those shortest for their age. When interpreting lung function test results, the changing pattern in FEV1/FVC and RV/TLC should be considered. Prediction equations for children and adolescents should take into account sex, height, age, ethnic group, and, ideally, also SH.

Towards the elimination of tuberculosis in a developing country: 25 years of tuberculosis control in Oman.

OBJECTIVE: To analyse trends of tuberculosis (TB) in Oman (1981-2005) in relation to the socio-economic development of the country. METHODS: Data were used from the National Tuberculosis Control Programme (NTP). Information on TB cases' age, sex and type were obtained from the national book (1981-1991) and the computer database (1992-2005). RESULTS: TB notification rates among Omani nationals declined by more than 85% from 1981 to 1995. During the period 1981-1993, the TB notification rate declined by around 15% per year, compared to only 3.6% per year in subsequent years. Males and the age group > or = 50 years have higher rates than females and younger age groups, respectively. Non-nationals contributed 21% of all TB cases notified and 40% of all smear-positive cases. Of cases among nationals notified between 2004 and 2005, 95% had a family income lower than the national average. CONCLUSION: Although TB notification in Oman has declined by more than 85% over the last 25 years, the decline has slowed down over the last 10 years, requiring a detailed analysis of existing TB control measures and implementation of additional measures for TB elimination.

Exercise responses following heart transplantation: 5 year follow-up.

Heart transplantation is an established treatment for end stage heart failure. In addition to increased life expectancy, heart transplant recipients report a remarkable improvement in symptoms and functional capacity. Exercise performance following heart transplantation, however, remains impaired even in the absence of exertional symptoms. We have assessed the response to exercise in 47 patients with cardiac failure prior to and then at yearly intervals to five years post transplantation. All patients performed incremental symptom limited exercise tests during which minute ventilation (V'E), oxygen consumption (V'O2) and carbon dioxide production (V'CO2) and heart rate (HR) were measured. Ventilatory response (V'E/V'CO2), anaerobic threshold (V'O2 AT %predicted) and heart rate response (HR/VO2) were calculated. The dead space to tidal volume ratio (VD/VT) and alveolar-arterial oxygen gradient (A-aO2) were computed from transcutaneous monitoring. Despite substantial improvement in subjective functional capacity, heart transplant recipients continue to have limited exercise performance [Maximal V'O2% predicted pre-transplant 41.3 (2.2); 1 year 48.6 (1.7), p <0.001: V'O2 AT% 31.5 (1.1); 1 year 35.6 (1.0); respectively p<0.05]. The maximal oxygen uptake continued to improve at two years post-transplant but, thereafter, there was no further significant change at up to 5 years post transplant [50.9 (1.5)]. At one year post-transplantation peak HR [65.2 (0.9) vs 79.1(1.4)] and the HR/VO2 response [24.0(1.8) vs 79.6(4.2)] were significantly reduced compared to pre-transplant values. The heart rate response remained lower compared to predicted at 5 years post-transplant although there was a significant increase compared to one year post-transplant (32.9 vs 24.0mls/bt). There was a weak but significant relationship between maximal VO2 and peak HR (0.39, p<0.05) and HR/VO2 (r= 0.37, p<0.05) at one year post-transplant. Prior to transplantation the ventilatory response to exercise was elevated [V'E/V'CO2 45.6 (2.5)] and decreased significantly following transplantation [1 yr 34.1 (1.3), respectively p<0.001]. In addition, despite significant improvement in VD/VT after transplantation, it remained higher than normal [Pre VD/VT at maximum exercise 0.35 (0.02); 1 yr 0.31 (0.02); p<0.05]. There was a further fall in the VE/VCO2 and VD/VT at two years post-transplantation with no further change at up to 5 years post transplantation [VE/VCO2 32.0 (1.0); VD/VT 0.29 (0.01)]. Although cardiac output is markedly improved after transplantation, due to chronotropic incompetence associated with denervation, its response remains subnormal and this may explain the residual abnormalities of ventilatory and gas exchange responses to exercise following transplantation.

Nature of bacteria found on some wards in Sultan Qaboos University Hospital, Oman.

This study aims to determine what objects lying in the hospital environment or brought in from outside contribute to the introduction of bacteria associated with nosocomial infections. One hundred swab specimens collected from children's toys, sinks, door handles, telephone handsets and flowers brought into the hospital were plated on different culture media. Colonial growth on the media was purified and identified subsequently using standard bacteriological methods. Of the 100 samples cultured, 61 (61%) grew a range of bacteria including Pseudomonas aeruginosa (n=14, 23.0%), Acinetobacter spp. (n=13, 21.3%), Serratia spp. (n=9, 14.7%), Staphylococcus epidermidis (n=9, 14.7%), Stenotrophomonas maltophilia (n=4, 6.6%), Staphylococcus aureus (n=4, 6.6%), Enterobacter cloacae (n=3, 4.9%), Pantoea sp. (n=2, 3.3%), Chryseobacterium sp. (n=2, 3.3%) and Klebsiella pneumoniae (n=1, 1.6%). Although all the Serratia, Enterobacter, Klebsiella and Pantoea species isolates showed varying degrees of resistance to gentamicin, ceftriaxone, cefuroxime and cefotaxime, all were resistant to ampicillin. Chryseobacterium and Stenotrophomonas species isolates were resistant to amikacin, imipenem, gentamicin and ceftazidime, to which only three isolates of Pseudomonas species were resistant. All the staphylococcal isolates were susceptible to methicillin. Although there has been no major outbreak of a nosocomial infection in the hospital, it is strongly recommended that effective control measures (e.g., sampling the hospital water supply, disinfecting children's toys, use of appropriate hand washing and checking some of the disinfectants for presence of bacteria) are needed. These measures are necessary to ensure that the antibiotic-resistant strains identified in this study are not allowed to spread in the hospital.

Assessment of aerobic fitness and its correlates in Omani adolescents using the 20-metre shuttle run test: A pilot study.

OBJECTIVE: To assess aerobic fitness in male and female adolescents using the multistage 20-metre shuttle run test and correlate it with selected fitness variables. METHOD: The subjects comprised 83 girls and 64 boys aged 15-16 years, randomly selected from two segregated government schools in Muscat. After the pupils filled in a short questionnaire on their personal leisure time activities of the preceding week, their heights and weights were measured. Aerobic fitness was assessed by estimating each pupil's minimal oxygen uptake levels (VO2max) using the multistage 20-metre shuttle running test (20-MST). RESULTS: Boys spent more time than girls on leisure physical activities, television, computer and video games and the Internet. The estimated VO2max in both boys and girls showed high correlation with their weekly physical activities. The time spent on television and computer negatively correlated with VO2max in girls but not in boys. Girls had higher body mass index (BMI) and less VO2max compared to boys; BMI showed a negative correlation with VO2max in girls but not in boys. CONCLUSION: Aerobic fitness in this sample was higher in boys than in girls and was strongly influenced by weekly physical activities in both genders. The 20-MST has proved a simple and inexpensive field test for aerobic fitness that could be implemented on a wide scale.

Exercise intolerance following heart transplantation: the role of pulmonary diffusing capacity impairment.

STUDY OBJECTIVES: Although impairment of the diffusing capacity of the lung for carbon monoxide (DLCO) in heart transplant recipients is well-documented, there are limited data on its impact on exercise capacity in these patients. The aim of this study was to determine the effect of DLCO reduction on exercise capacity in heart transplant recipients. DESIGN: Descriptive cohort study. SETTING: A regional cardiopulmonary transplant center. PARTICIPANTS: Twenty-six heart transplant recipients who were studied before and after transplantation compared with 26 healthy volunteers. MEASUREMENTS: Spirometry and static lung volumes were measured using body plethysmography, DLCO was measured using the single-breath technique, and progressive cardiopulmonary exercise was performed using a bicycle ergometer, continuous transcutaneous blood gas monitoring, and on-line analysis of minute ventilation, oxygen uptake (VO(2)), and carbon dioxide production. RESULTS: Before transplantation, the mean percent predicted for hemoglobin-corrected DLCO was reduced in patients (73.2%) compared to healthy control subjects (98.8%; p < 0.001) and declined significantly after transplantation (60.1%; p < 0.05). Although the mean maximal symptom-limited VO(2) (VO(2)max) increased after transplantation (increase, 41.3 to 48.6% of predicted; p < 0.05), it remained substantially lower than normal (92.9%; p < 0.001). There was a significant correlation between DLCO and VO(2)max after transplantation (r = 0.61; p = 0.001), but not before transplantation (r = 0.09; p = 0.66). DLCO was also inversely correlated with other respiratory responses to exercise, including the following: the ventilatory response to exercise (r = -0.44; p < 0.05); dead space to tidal volume ratio (r = -43; p < 0.05); and the alveolar-arterial oxygen gradient (r = -0. 45; p < 0.05), but there was no correlation between any of these variables and DLCO before transplantation. CONCLUSION: DLCO reduction after heart transplantation appears to represent persistent gas exchange impairment and contributes to exercise limitation in heart transplant recipients.

Mechanisms of pulmonary transfer factor decline following heart transplantation.

OBJECTIVE: Although the decline in the pulmonary transfer factor (TL(CO)) following heart transplantation is well documented, the causes and mechanisms of this decline remain unknown. The aim of this study was to determine the relative contribution of each of TL(CO) components (the diffusing capacity of the alveolar-capillary membrane (D(M)), the pulmonary capillary blood volume (V(C)) and haemoglobin concentration) to TL(CO) reduction in heart transplant recipients. METHODS: TL(CO) and its components were measured in 75 heart transplant recipients (mean age 48 years, range 19-61) between 6 weeks and 36 months after transplantation using the Roughton and Forster method and the single-breath technique. Results were compared with data from 38 heart transplant candidates (mean age 51 years, range 34-61) and 26 normal subjects (mean age 47 years, range 27-62). RESULTS: The mean percentage predicted TL(CO) was reduced in recipients compared to candidates (56.9 and 69.9%, respectively, P<0. 001) and both were lower than normal controls (97.7%, P<0.001). The mean percent predicted V(C) was also reduced in recipients compared to candidates (52.8% vs. 80.2 (4.2)%, P<0.001) which was also lower than normal subjects (102%, P<0.001). D(M) was equally reduced in recipients and candidates (77.7 and 81.4%, respectively, P=0.48) compared to normal subjects (100.0%, P<0.001). Correction for haemoglobin concentration increased TL(CO) in recipients to 63.5% (P<0.001), but it remained lower than haemoglobin-corrected TL(CO) in candidates (71.1%, P<0.001). In recipients, the intra-capillary resistance (1/thetaV(C)) formed 60% of the total resistance to CO transfer (1/TL(CO)) compared to 50% in candidates and normal subjects. CONCLUSIONS: TL(CO) decline following heart transplantation is due to an increase in the intra-capillary resistance, and this appears to be due to a combination of anaemia and reduced pulmonary capillary blood volume, with the diffusing capacity of the alveolar-capillary membrane remaining unchanged.

The alveolar-capillary membrane diffusing capacity and the pulmonary capillary blood volume in heart transplant candidates.

OBJECTIVES: To determine the mechanism of impairment of pulmonary transfer factor for carbon monoxide (TL(CO)) in heart transplant candidates, as this is the most common lung function abnormality. SETTING: Regional cardiopulmonary transplant centre. METHODS: TL(CO) and its components (the diffusing capacity of the alveolar-capillary membrane (D(M)) and the pulmonary capillary blood volume (V(C))) were measured using the Roughton and Forster method and the single breath technique in 38 patients with severe chronic heart failure awaiting heart transplantation (mean age 51 years, range 19 to 61; mean left ventricular ejection fraction 12.8%). Results were compared with data from 26 normal subjects (mean age 47 years, range 27 to 62). RESULTS: Mean per cent predicted TL(CO), D(M), and V(C) were significantly reduced in patients (69.9%, 81.4%, and 80.2% of predicted, respectively) compared with controls (97.7%, 100.1%, and 102.3% of predicted, respectively, p < 0.001). The relative contribution of the two components of TL(CO) in patients was similar to that of normal subjects, with each component accounting for approximately 50% of the total resistance to diffusion (1/TL(CO)). CONCLUSIONS: TL(CO) impairment in patients with severe chronic heart failure awaiting heart transplantation results from a proportionate reduction in both D(M) and V(C), suggesting a significant disturbance of the pulmonary vascular bed.

The measurement of the single-breath transfer factor for carbon monoxide and its components using the Morgan Transflow system.

In contrast to the standard single-breath transfer factor for carbon monoxide (TLCO), there are no specific guidelines or recommendations for the measurement of its components, the pulmonary capillary blood volume (VC) and membrane component (DM), by the Roughton and Forster method. Ten randomly selected heart transplant patients (three life-long non-smokers, seven ex-smokers > 1 yr, age range 24-55 years) were assessed on two occasions using either the standard or high-oxygen mixture as the first inspired gas in random order. Ten normal subjects (all non-smokers, age range 23-54 years) were assessed on two occasions using either a long protocol (30 min waiting time between repeat measurements in an individual set) or a short protocol (5 min waiting time). Two technically acceptable results of TLCO were used to derive a mean value for DM and VC for each set of measurements (Transflow, P. K. Morgan, Kent, U.K.). The different sequences of gas mixtures produced no significant differences between the values obtained in ten heart transplant patients for mean TLCO (mmol min-1 kPa-1) (standard first 5.13 +/- 1.15, high-oxygen first 5.14 +/- 1.12; limits of agreement -0.57 to 0.59 for DM or for VC. The long or short protocol produced no significant differences between the means of TLCO (mmol min-1 kPa-1) (long 8.0 +/- 1.9, short 8.0 +/- 1.9; limits of agreement -0.5 to 0.5), DM or VC. This allows the development of a standard test protocol of short duration (about 40 min) making it practical for clinical use without compromising the precision or reproducibility of the results obtained.

Home treatment of exacerbations of chronic obstructive pulmonary disease by an acute respiratory assessment service.

BACKGROUND: Exacerbations of chronic obstructive pulmonary disease are a major cause of hospital admissions, but do not require intensive investigation or complex therapy. We investigated the suitability of home care for severe uncomplicated exacerbations. METHODS: Over 3.5 years we assessed 962 patients with exacerbations of chronic obstructive pulmonary disease after referral to a hospital respiratory department by their family physicians. All patients had chest radiographs, oxygen-saturation or arterial-gas analysis, spirometry, and physical assessment. Unless admission was thought to be essential, patients were allowed home with a customised treatment package. Each patient was visited daily by a respiratory nurse who monitored progress and treatment compliance and provided education and reassurance. FINDINGS: 145 (15%) of 962 required admission at initial referral and 115 (12%) were admitted later. 653 (68%) patients were managed entirely at home and 49 (5%) were referred inappropriately. One patient died at home. All patients had severe disease with a mean forced expiratory volume in 1 s of 1.02 L and 395 (41%) had required hospital admission in the previous year. INTERPRETATION: After formal assessment in a hospital respiratory unit, many patients with exacerbations of chronic obstructive pulmonary disease can be treated at home by respiratory nurses.

The time course of pulmonary transfer factor changes following heart transplantation.

OBJECTIVE: The pulmonary transfer factor for carbon monoxide (TLCO) has been reported to decline following heart transplantation, but the time course of this decline is not well documented. The aim of this study was to define the longitudinal changes in TLCO after heart transplantation. METHODS: Single breath TLCO, lung volumes and expiratory flow rates were prospectively measured in 57 patients (mean age 49 years, range 19-61) before and at least once after heart transplantation. Thirty seven of the 57 patients had four post-transplant assessment which were performed at 6 weeks, 3, 6 and 12 months in 26 patients and at 12, 18, 24 and 36 months in 11 patients. Results were compared with data from 28 normal subjects (mean age 40 years, range 19-61). RESULTS: Before transplantation there was a mild impairment of lung volumes and expiratory flow rates. At 6 weeks after transplantation, there was a further reduction in the forced expiratory volume in one second, forced vital capacity, residual volume and total lung capacity, but all of these increased in the subsequent measurements to exceed their pre-transplant values at about 1 year after transplantation. Haemoglobin-corrected TLCO was also reduced before transplantation compared to normal controls (74.3% and 98.6% of predicted respectively, P < 0.001). Although TLCO per unit alveolar volume (KCO) was relatively preserved in heart transplant candidates, it was still significantly lower than that of normal controls (92.6% and 105.3% of predicted respectively, P < 0.05). After transplantation, mean haemoglobin-corrected TLCO and KCO declined by 12% and 20% of predicted respectively) with the majority of patients having reductions greater than 10% of predicted. The decline in TLCO and KCO was evident at 6 weeks after transplantation with no further changes in the subsequent measurements. CONCLUSIONS: TLCO is reduced in heart transplant candidates and declines further after heart transplantation despite improvement in lung volumes and airway function. The early and non-progressive nature of TLCO decline suggests an aetiology exerting its effect on TLCO within the first 6 weeks after transplantation.

Ventilatory and gas exchange abnormalities on exercise in chronic heart failure.

The mechanism of breathlessness on exertion in patients with chronic heart failure are still not fully understood. We therefore investigated the effects of ventilatory and gas exchange abnormalities on exercise capacity in chronic heart failure. Exercise testing was performed in 30 patients with exertional breathlessness due to chronic heart failure and in 30 controls, using continuous transcutaneous blood gas monitoring. Maximal symptom-limited oxygen consumption as (V'O2) as a percentage predicted was reduced in patients (45 +/- 10%; mean +/- SD) compared to controls (87 +/- 7). The ventilatory response (minute ventilation/carbon dioxide production (V'E/V'CO2)) was significantly increased in patients compared to controls (39.9 +/- 7.7 and 25.9 +/- 3.6, respectively). The dead space to tidal volume ratio (VD/VT) was raised in patients compared to controls at rest (0.45 +/- 0.04 vs 0.35 +/- 0.02, respectively) and this persisted on exertion (0.40 +/- 0.05 in patients and 0.20 +/- 0.05 in controls). At maximal symptom-limited exercise, V'E/V'CO2 was inversely related to the % predicted V'O2 in patients, but not in controls (r = -0.62 and r = -0.24, respectively). In patients, V'E/V'CO2 was significantly correlated with VD/VT at maximum exercise (r = 0.82). Patients with chronic heart failure have a significant degree of "wasted ventilation" on exertion, which is associated with increased ventilatory response. The increased ventilatory response on exertion appears to contribute to exercise limitation in these patients.