Biomedical subjects
Publications and source records attributed to C M Parry.
Enteric fever continues to be a common and serious problem worldwide, and the need for reliable and cheap alternatives to culture methods for diagnosis remains. Epidemics of different strains may coexist in the same geographical area and the rapid emergence of resistance to fluoroquinolones, independent of plasmid mediated multidrug resistance, means that alternative drugs for chemotherapy are also needed.
Salmonella typhi was isolated from 369 and Salmonella paratyphi A was isolated from 6 of 515 Vietnamese patients with suspected enteric fever. Compared with conventional broth culture of blood, direct plating of the buffy coat had a diagnostic sensitivity of 99.5% (95% confidence interval [CI], 97.1 to 100%). Blood bacterial counts were estimated by the pour plate method. The median S. typhi count in blood was 1 CFU/ml (range, <0.3 to 387 CFU/ml), of which a mean of 63% (95% CI, 58 to 67%) were intracellular. The mean number of bacteria per infected leukocyte was 1.3 (interquartile range [IQR], 0.7 to 2.4) CFU/cell (n = 81). Children (< 15 years old; n = 115) had higher median blood bacterial counts than adults (n = 262): 1.5 (range, <0.3 to 387) versus 0.6 (range, <0.3 to 17.7) CFU/ml (P = 0.008), and patients who excreted S. typhi in feces had higher bacteremias than those who did not: a median of 3 (range, <0.3 to 32) versus 1 (range, <0.3 to 68) CFU/ml (P = 0.02). Blood bacterial counts declined with increasing duration of illness (P = 0.002) and were higher in infections caused by multidrug-resistant S. typhi (1.3 [range, <0.3 to 387] CFU/ml; n = 313) than in infections caused by antibiotic-sensitive S. typhi (0.5 [range, <0.3 to 32] CFU/ml; n = 62) (P = 0.006). In a multivariate analysis this proved to be an independent association, suggesting a relationship between antibiotic resistance and virulence in S. typhi.
The triumph of antibiotics over bacterial pathogens that has occurred in the latter half of this century looks increasingly threatened as we approach the new millennium. Increasing resistance in important pathogens such as Mycobacterium tuberculosis, Shigella, and Streptococcus pneumoniae threatens the lives of millions. The increasing problems with drug resistance in (C. diphtheriae, Salmonella typhi and the pneumococcus in Vietnam are presented as examples of the challenge confronting tropical countries.
A patient probably acquired hepatitis B virus (HBV) from a transfused infected unit of fresh frozen plasma. She had been on regular haemodialysis for four months before her infection was discovered. One hundred and seventy-six patients and 304 staff contacts were screened and there were no secondary cases. At donation the infected blood donor was hepatitis B surface antigen (HBsAg) negative but subsequently proved to be anti-hepatitis B core (HBc)-positive and positive for HBV DNA. Consideration should be given to screening blood donations for anti-HBc in addition to HBsAg. Vigilance needs to be maintained on dialysis units against sporadic cases of hepatitis B. All staff should be immunized and be able to demonstrate protective levels of anti-HBs.
Nalidixic acid-resistant Salmonella typhi (NARST) was first isolated in Viet Nam in 1993. Analysis of the quinolone resistance-determining region of gyrA in 20 NARST isolates by polymerase chain reaction and single-stranded conformational polymorphism yielded two novel patterns: pattern II corresponding to a point mutation at nucleotide 87 Asp-->Gly (n = 17), and pattern III corresponding to a point mutation at nucleotide 83 Ser-->Phe (n = 3). In trials of short-course ofloxacin therapy for uncomplicated typhoid, 117 (78%) of 150 patients were infected with multidrug-resistant S. typhi, 18 (15%) of which were NARST. The median time to fever clearance was 156 hours (range, 30-366 hours) for patients infected with NARST and 84 hours (range, 12-378 hours) for those infected with nalidixic acid-susceptible strains (P < .001). Six (33.3%) of 18 NARST infections required retreatment, whereas 1 (0.8%) of 132 infections due to susceptible strains required retreatment (relative risk = 44; 95% confidence interval = 5.6-345; P < .0001). We recommend that short courses of quinolones not be used in patients infected with NARST.
Confirmation of tuberculosis in young children is difficult as they seldom expectorate sputum. Gastric aspirates are invasive and stressful and like laryngeal swabs are seldom smear positive. Induction of sputum by nebulised hypertonic saline (3%) was attempted in 30 Malawian children aged 3-15 years and was successful in 29. Four sputa were smear positive and Mycobacterium tuberculosis was cultured from three of them. A further four sputa were culture positive though smear negative. In all, the diagnosis of tuberculosis was confirmed in eight (28%) of 29 children. The presence of polymorphonuclear cells in the specimen was indicative of sputum, in contrast to epithelial cells which originate from saliva. A predominance of polymorphonuclear cells in specimens was more common in older children and these specimens were more likely to be smear positive or culture positive. Sputum induction is a useful method for the confirmation of tuberculosis and is possible in young children.
SETTING: There has been a marked increase in notified cases of smear-negative pulmonary tuberculosis in Malawi since 1986. One reason for this may be related to the difficulties of getting adequate samples of expectorated sputum from patients. Sputum induction with nebulized hypertonic saline may be a simple way of obtaining a better specimen. OBJECTIVE: To examine the value of sputum induction for detecting cases of smear-positive tuberculosis. DESIGN: Sputum induction was performed on 82 adults presenting to the Queen Elizabeth Central Hospital, Blantyre, Malawi with clinically suspected pulmonary tuberculosis who were expectorated sputum smear-negative or unproductive of sputum. The induced sputum smear was examined for acid-fast bacilli and cultured for mycobacteria. RESULTS: Sputum was successfully induced from 73 of the 82 patients (26 previously smear-negative and 47 previously unproductive). The induced sputum was smear-positive in 18 patients (5 previously smear-negative and 13 unproductive). Cultures were positive for Mycobacterium tuberculosis in the 18 smear-positive patients and a further 12 that had been smear-negative. 94 cases of smear-positive pulmonary tuberculosis were notified during the study period. 18 (19%) were as a result of sputum induction. CONCLUSION: Sputum induction is a useful technique for improving the case detection rate of smear-positive tuberculosis in Malawi.
We report a case of staphylococcal scalded skin syndrome in a 77-year-old man with an infected surgical wound. The patient was immunocompetent and had only mildly impaired renal function. The pathogenic and aetiological factors of the condition are discussed.
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Anthropometric measurements were performed on admission and at four weeks post discharge on 25 adults referred to hospital with acute gastroenteritis. There was a significant change in weight (P < 0.001) and mid-arm circumference (P < 0.05), but no change in skinfold thickness, arm muscle area or arm fat area. The results suggest that weight change during acute gastroenteritis is more a consequence of dehydration than of malnutrition.
The treatment of an infected vascular graft invariably requires an extra-anatomic bypass through a non-infected tissue plane, as simple drainage with antibiotics is rarely successful. We report a case in which an established infection of a prosthetic vascular graft with Salmonella dublin was successfully treated with simple drainage and a prolonged course of oral ciprofloxacin.
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To assess the knowledge of hospital doctors about patients at increased risk of infection with human immunodeficiency virus (HIV) or hepatitis B virus, and the precautions they took during phlebotomy in such patients, an anonymous postal questionnaire was sent to all 307 hospital doctors working at two District General Hospitals in Liverpool, UK. Two hundred and thirty-eight (77.5%) of the questionnaires were returned. More than 90% of respondents considered a history of male homosexuality, intravenous drug abuse, prostitution or a child of a prostitute to indicate an inoculation risk. There was uncertainty about a previous prison sentence in the 1980s, residence in a home for the mentally handicapped, previous residence in the tropics and hospital treatment in the tropics. Thirty-eight percent of doctors would never enquire about sexual preference, 54.1% about a previous prison sentence and 15.7% about intravenous drug abuse in their clinical history. Although 97.4% of doctors would sometimes or always wear gloves during phlebotomy of an inoculation risk patient, 25.5% always resheathed the needle after phlebotomy and 20.8% would never take the sharps box to the patient. More effort is required to identify accurately inoculation risk patients and greater care is needed in phlebotomy techniques.
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Nalidixic acid (NA: 55 mg/kg daily for 5 days) is the recommended treatment for uncomplicated bacillary dysentery in areas where multidrug-resistant Shigella are prevalent. An open randomized comparison of this NA regimen with 2 doses of ofloxacin (total 15 mg/kg) was conducted in 1995/96 in 135 Vietnamese children with fever and bloody diarrhoea. Sixty-six children with a bacterial pathogen isolated were eligible for analysis. Of the 63 Shigella isolates, 39 (62%) were resistant to multiple antibiotics. Resolution times for fever and diarrhoea were similar in the 2 groups, but excretion time of stool pathogen was significantly longer in the NA recipients [median (range) days 1 (1-9) vs 1 (1-2), P = 0.001]. There were 9 (25%) treatment failures in the NA regimen and 3 (10%) in the ofloxacin group; P = 0.1. Two patients had NA-resistant Shigella flexneri. One of these isolates was selected during NA treatment. From a clinical and public health standpoint a 2-dose regimen of ofloxacin is preferable to nalidixic acid in the treatment of bacillary dysentery.
In a prospective study conducted between mid 1993 and 1994, 437 adults and children were admitted with community-acquired septicaemia to an infectious diseases hospital in southern Viet Nam. Gram-negative aerobes accounted for 90% of isolates and were predominantly Salmonella typhi (67%), Sal. para-typhi A (3%), Escherichia coli (10%), and Klebsiella spp. (5%). Other Salmonella spp. (1%), Pseudomonas aeruginosa (1%), Neisseria meningitidis (0.5%) and Haemophilus influenzae (0.2%) were uncommon. Staphylococcus aureus (5.5%) and Streptococcus pneumoniae (2%) were the most common Gram-positive isolates. Patients with enteric fever were younger (median age 16 years, range 1-63) than the other patients (median age 43 years, range 1-88) (P < 0.001) and had a lower mortality rate (0.3% vs. 23%; relative risk 69.5, 95% confidence interval 9.5-507.8; P < 0.0001). Over 70% of the Sal. typhi isolated were multi-drug-resistant, and 4% were resistant to nalidixic acid. Multidrug-resistant Sal. typhi is a major cause of community-acquired septicaemia in Viet Nam.