- Email: [email protected]
Homocysteine and endothelial vascular function
CORRESPONDENCE 1
2
3
Wynn RF, Cross MA, Hatton C, et al. Accelerated telomere shortening in young recipients of allogeneic bone-marrow transplants. Lancet 1998; 351: 178–81. Weng NP, Levine BL, June CH, Hodes RJ. Human naive and memory T lymphocytes differ in telomeric length and replicative potential. Proc Natl Acad Sci USA 1995; 92: 11091–94. Felizarta F, Drew W, Solomon WB, Seligman SJ. Telomere length of polymorphonuclear cells and PBMCs in HIV+ and control subjects. Fifth conference on retroviruses and opportunistic infections, Chicago, IL. Feb 1–5, 1998: abstr 566.
Intravenous immunoglobulins and transforming growth factor  Sir—Jörn Kekow and colleagues (Jan 17, p 184)1 report substantial but variable amounts of transforming growth factor  (TGF) in different intravenous immunoglobulin (IVIg) preparations. They also report increased TGF2 concentrations in vivo during IVIg infusion. TGF is a powerful inhibitor of proliferation and its administration led to immunosuppression in various animal studies on autoimmune diseases, as reviewed by Jörn Kekow et al. The investigators postulate that TGF contributes to the therapeutic effect of IVIg in autoimmune diseases. We and others2–5 have shown in vitro that IVIg inhibits proliferation of antigen-specific and non-antigenspecific stimulated peripheral blood lymphocytes and have speculated that this strong immunosuppressive effect of IVIg contributes to its therapeutic effect. In 1991, we suggested that TGF could be one of the candidate factors in IVIg to mediate this in-vitro effect. To test this hypotheses, we investigated whether addition of antiTGF neutralising antibodies abolished the suppressive effect of IVIg when added to peripheral blood lymphocytes stimulated in a mixed lymphocyte reaction. The anti-TGF neutralising antibody (British Biotechnology Ltd, Abingdon, UK) we used has a high titre for neutralisation of the biological activity of human TGF1 and TGF1.2 Since the antibody has a lower titre for neutralisation of TGF2,
about 100-fold more antibody is required. The concentration of antibody required to yield 50% maximum inhibition of the cytokine, when that cytokine is present at five times its normal median effective dose, is defined as the neutralising dose50 (ND50). The ND50 is 2–3 g/mL according to the manufacturers instructions. The mixed lymphocyte reactions between unrelated donors were set up as previously described.2 3 H-thymidine incorporation was measured. We added IVIg in a concentration of 30 mg/mL to peripheral blood lymphocytes before stimulation in a mixed lymphocyte reaction. In more than 30 experiments this dose resulted in about 99% inhibition. IVIg was also added after preincubation with 1000 g/mL antiTGF neutralising antibody for 2 h at room temperature. This high dose of neutralising antibody would surely also block a possible TGF2 effect. The results are shown in the table. We found no evidence that the observed immunosuppressive effect of IVIg in vitro is due to TGF, because high doses of a neutralising antibody could not abolish this inhibitory effect. Moreover, with anti-IgG affinity column purification of IVIg, the inhibitory effect was recovered from IgG of the column eluate and not in the void.2 Kekow and co-workers mention the TGF mobility absent in the eluate from a protein-A column. As is commonly the case with IVIg, not one mechanism seems responsible for the many (sometimes opposite) effects observed in vivo and in vitro. Also, extrapolating in-vitro findings to in-vivo application seems too simple with IVIg. Although the 15 patients treated by Kekow and colleagues showed a small increase in plasma concentration of TGF2, they do not say whether this increase correlates with clinical improvement. We support the view that further studies are needed before any conclusions can be drawn on the role of TGF in IVIg. *I N van Schaik, M Vermeulen, A Brand *Department of Neurology, Academic Medical Center, PO Box 22700, 1100 DE Amsterdam, Netherlands; and Deparment of Immunohematology, Academic Hospital, Leiden (e-mail: [email protected])
Mixed lymphocyte reactions
Donor 1 versus donor 2
Donor 2 versus donor 1
Medium Medium+IVIg 30 mg/mL Medium+anti-TGF neutralising antibody 1000 g/mL Medium+IVIg 30 mg/mL and anti-TGF neutralising antibody 1000 g/mL
51 915 296 (99%) 46 046
471 411 401 (99%) 44 588
129 (99%)
206 (99%)
3
H-thymidine incorporation in counts per min (% inhibition) of mixed lymphocyte reactions between unrelated donors by IVIg, anti-TGF neutralising antibody, or both
1288
1
2
3
4
5
Kekow J, Reinhold D, Pap T, Ansorge S. Intravenous immunoglobulins and transforming growth factor . Lancet 1998; 351: 184–85. Van Schaik IN, Lundkvist I, Vermeulen M, Brand A. Polyvalent immunoglobulin for intravenous use interferes with cell proliferation in vitro. J Clin Immunol 1992; 12: 1–10. Anderson UG, Bjork L, Skansen-Saphir U, Andersson JP. Down-regulation of cytokine production and interleukin-2 receptor expression by pooled human IgG. Immunology 1993; 79: 211–16. Klaesson S, Ringdén O, Markling L, Remberger M, Lundkvist I. Immune modulatory effects of immunoglobulins on cell-mediated immune responses in vitro. Scand J Immunol 1993; 38: 477–84. Amran D, Renz H, Lack G, Bradley K, Gelfand EW. Suppression of cytokinedependent human T-cell proliferation by intravenous immunoglobulin. Clin Immunol Immunopathol 1994; 73: 180–86.
Homocysteine and endothelial vascular function Sir—Hyperhomocysteinaemia is an independent risk factor for vascular disease;1 investigators have postulated that it might cause atherosclerosis by damaging the endothelium 2 either directly or by altering oxidative status.3 John Chambers and colleagues (Jan 3, p 36)4 report an association between impaired endothelial function and an acute increase in plasma homocysteine after oral methionine (L-methionine) 0·1 g/kg loading dose. We found no change in endothelial function or oxidation status with methionine supplementation in 16 healthy volunters (median age 23 [range 20–30] years). The study had three phases. First, we assessed the acute effects of randomly allocated methionine 250 mg or placebo on baseline measurements. A second study was carried out after 1 month of treatment with methionine 250 mg or placebo four times daily. For the final phase, eight volunteers were given unblinded treatment with methionine 0·1 g/kg daily for 1 week. We used strain gauge venous occlusion plethysmography to measure forearm blood flow after local intra-arterial infusion of acetylcholine (to assess endothelium-dependent vasodilatation) and sodium nitroprusside (to assess endothelium-independent vasodilatation). Lipid peroxidation was measured as thiobarbituric acid reactive substances (TBARS), expressed as malondialdehyde equivalents. Each volunteer abstained from alcohol and caffeine-containing products and fasted for 6 h before the start of the study. A 27-gauge needle was inserted into the non-dominant
THE LANCET • Vol 351 • April 25, 1998
CORRESPONDENCE
brachial artery to allow local intraarterial drug infusion. A mercury in silastic strain gauge was coupled to an electronically calibrated plethysmograph (Medasonics model SPG16, CA, USA). The voltage output was transferred to a Macintosh personal computer with a MacLab analogue-todigital converter and CHART software (version 3.4.3). Acetylcholine and sodium nitroprusside were infused intra-arterially in four incremental doses for 3 min and forearm blood flow measured in the last min of the infusion. We took the mean of five consecutive forearm-blood-flow measurements for the statistical analysis. Forearm blood flow was expressed as mL/100 mL forearm volume/min. We measured plasma homocysteine by high-performance liquid chromatography. Change in forearm blood flow from baseline was analysed by a two-way ANOVA. Basal blood flow, plasma concentration of homocysteine, and TBARS were analysed by one-way ANOVA. We found no significant difference in homocysteine concentration, TBARS, or endothelial-dependent or endothelial-independent vascular responses after the first administration of methionine or placebo (p>0·05) or after 1 month of treatment (p>0·05). 1 week of methionine 0·1 g/kg led to a significant increase in homocysteine (from 8·2 [95% CI 6·5–10·2] to 20·2 [14·4–26·2] mol/L, p<0·0015), but with no associated change in TBARS or endothelial vascular responses (p>0·05). This finding suggests that acute increases in homocysteine concentrations do not significantly impair endothelial function or oxidative status (as measured by TBARS) in healthy volunteers. *Colm G Hanratty, Daniel F McAuley, Colm McGurk, Ian S Young, G Dennis Johnston *Department of Therapeutics and Pharmacology, Queen’s University of Belfast, Belfast BT9 7BL, UK; and Department of Clinical Biochemistry, Institute of Clinical Science, Royal Victoria Hospital, Belfast 1
2
3
4
Stampfer MJ, Malinow MR, Willeth WC, et al. A prospective study of plasma homocysteine and risk of myocardial infarctions in US physicians. JAMA 1992; 268: 877–81. Loscalzo J. The oxidant stress of hyperhomocyst(e)inemia. J Clin Invest 1996; 98: 5–7. Lentz SR, Sobey CG, Piegors DJ, Bhopatkar MY, Faraci FM, Malinow MR. Vascular dysfunction in monkeys with diet-induced hyperhomocysteinaemia. J Clin Invest 1996; 98: 24–29. Chambers JC, McGregor A, Jean-Marie J, Kooner JS. Acute hyperhomocysteinaemia and endothelial dysfunction. Lancet 1998; 351: 36–37.
THE LANCET • Vol 351 • April 25, 1998
Quinolone-resistant Salmonella typhi in Vietnam SIR—We share the worries of D A Murdoch and colleagues (Jan 31, p 339)1 about the spread of quinoloneresistant Salmonella typhi in Asia. Typhoid fever has been endemic in Vietnam for many years and is a common cause of admission to the Centre for Tropical Diseases (CTD) in Ho Chi Minh City, an infectious disease referral centre for the south of the country.2 80% of blood culture isolates of S typhi at this centre carry plasmidmediated resistance to chloramphenicol, ampicillin, and trimethoprimsulphamethoxazole (co-trimoxazole). Over the past 5 years we have observed a steady increase in the incidence of quinolone-resistant typhoid fever. These isolates have an ofloxacin MIC90 of 0·5 mg/L (the concentration inhibiting growth in 90% of isolates) compared with 0·06 mg/L in sensitive isolates. Although they still appear sensitive to fluoroquinolones by disc sensitivity testing (albeit with reduced zone sizes) they are clinically resistant. Time to fever clearance is prolonged and cure rates are only 50% compared with over 97% for sensitive strains.3 These quinolone-resistant S typhi are characterised by resistance to nalidixic acid (MIC90 128 mg/L). The proportion of quinolone-resistant S typhi at CTD increased slowly from 4% (10/246) in 1993 to 12% (27/228) in the first 9 months of 1997. Since then there has been an alarming increase; over the past 4 months 76% (161/213) of blood culture isolates of S typhi were nalidixic acid (ie, quinolone) resistant. The MICs of these recent isolates to ofloxacin (MIC90 1·0 mg/L) and ciprofloxacin (MIC900·5 mg/L) were significantly higher than that for the nalidixic-acid-resistant isolates seen in the previous 4 years. These resistant strains are sensitive to ceftriaxone, cefixime, and azithromycin, but clinical response to these drugs is slow (fever clearance takes 7 days or more) and failure rates can be over 20%.4,5 These epidemics of quinoloneresistant typhoid fever in Vietnam and Tajikistan1 highlight an approaching crisis in the antibiotic therapy of typhoid fever since resistant infections require expensive treatments which are less effective and associated with higher stool carriage rates, and thus greater transmission potential than quinolonesensitive infections. Long courses of fluoroquinolones at a high dose may be clinically effective, but this would increase the cost of treatment and reassert worries about fluoroquinolone use in children. Full fluoroquinolone resistance is likely to appear soon, under continued selection pressure.
Fluoroquinolone treatment of nalidixic-acid-sensitive typhoid fever in Vietnam costs $US6–10. To treat quinolone-resistant strains a prolonged course of fluoroquinolone would cost $28–42, azithromycin $35–50, oral cephalosporins $80–90, and parenteral cephalosporins $150–200. Treatment may become unaffordable for patients in typhoid endemic areas and the clinical evaluation of new affordable regimens for resistant strains is pressing. We thank N J White for his contribution.
*C Parry, J Wain, N T Chinh, Ha Vinh, J J Farrar Centre for Tropical Diseases, University of Oxford,Oxford, UK; and Wellcome Trust Clinical Research Unit, 190 Ben Ham Tu, Quan 5, Ho Chi Minh City, Vietnam 1
2
3
4
5
Murdoch DA, Banatval NA, Bone A, Shoismatulloer BI, Ward LR, Threlfall EJ. Epidemic ciprofloxacin-resistant Salmonella typhi in Tajikistan. Lancet 1988; 351: 339. Hoa NTT, Diep TS, Wain J, et al. Community acquired septicaemia in southern Vietnam: the importance of multi-drug resistant Salmonella typhi. Trans Roy Soc Trop Med Hyg (in press). Wain J, Hoa NTT, Chinh NT, et al. Quinolone-resistant Salmonella typhi in Vietnam: molecular basis of resistance and clinical response to treatment. Clin Infect Dis 1997; 25: 1404–10. White NJ, Parry CM. The treatment of typhoid fever. Curr Opin Infect Dis 1996; 9: 298–302. Tribble D, Girgis N, Habib N, Butler T. Efficacy of azithromycin for typhoid fever. Clin Infect Dis 1995; 21: 1045–46.
New-variant CreutzfeldtJakob disease and treatment of haemophilia Sir—Tony Baxter and colleagues (Feb 21, p 600)1 challenge the view of the Executive Committee of the UK Haemophilia Centre Directors’ Organisation that recombinant factor VIII (rVIII) is safer than UK domestic factor VIII concentrate in relation to the risk of new variant Creutzfeldt-Jakob Disease (nvCJD). 2 They suggest that the prion protein of nvCJD could also be found in the albumin used as a stabiliser in the present generation of rVIII, and imply that rVIII is no safer than plasmaderived factor VIII. They miss the point. The human form of bovine spongiform encephalopathy is nvCJD, and has, with one exception, not been described outside the UK. Although there is no direct evidence of blood transmission of nvCJD, the prion protein has been detected in tonsils and could be within circulating Blymphocytes. Blood transmission is, therefore, a plausible suggestion which, given the long incubation period of the disease, may take many years to manifest. Of the 22 cases reported in the
1289
2
3
Wynn RF, Cross MA, Hatton C, et al. Accelerated telomere shortening in young recipients of allogeneic bone-marrow transplants. Lancet 1998; 351: 178–81. Weng NP, Levine BL, June CH, Hodes RJ. Human naive and memory T lymphocytes differ in telomeric length and replicative potential. Proc Natl Acad Sci USA 1995; 92: 11091–94. Felizarta F, Drew W, Solomon WB, Seligman SJ. Telomere length of polymorphonuclear cells and PBMCs in HIV+ and control subjects. Fifth conference on retroviruses and opportunistic infections, Chicago, IL. Feb 1–5, 1998: abstr 566.
Intravenous immunoglobulins and transforming growth factor  Sir—Jörn Kekow and colleagues (Jan 17, p 184)1 report substantial but variable amounts of transforming growth factor  (TGF) in different intravenous immunoglobulin (IVIg) preparations. They also report increased TGF2 concentrations in vivo during IVIg infusion. TGF is a powerful inhibitor of proliferation and its administration led to immunosuppression in various animal studies on autoimmune diseases, as reviewed by Jörn Kekow et al. The investigators postulate that TGF contributes to the therapeutic effect of IVIg in autoimmune diseases. We and others2–5 have shown in vitro that IVIg inhibits proliferation of antigen-specific and non-antigenspecific stimulated peripheral blood lymphocytes and have speculated that this strong immunosuppressive effect of IVIg contributes to its therapeutic effect. In 1991, we suggested that TGF could be one of the candidate factors in IVIg to mediate this in-vitro effect. To test this hypotheses, we investigated whether addition of antiTGF neutralising antibodies abolished the suppressive effect of IVIg when added to peripheral blood lymphocytes stimulated in a mixed lymphocyte reaction. The anti-TGF neutralising antibody (British Biotechnology Ltd, Abingdon, UK) we used has a high titre for neutralisation of the biological activity of human TGF1 and TGF1.2 Since the antibody has a lower titre for neutralisation of TGF2,
about 100-fold more antibody is required. The concentration of antibody required to yield 50% maximum inhibition of the cytokine, when that cytokine is present at five times its normal median effective dose, is defined as the neutralising dose50 (ND50). The ND50 is 2–3 g/mL according to the manufacturers instructions. The mixed lymphocyte reactions between unrelated donors were set up as previously described.2 3 H-thymidine incorporation was measured. We added IVIg in a concentration of 30 mg/mL to peripheral blood lymphocytes before stimulation in a mixed lymphocyte reaction. In more than 30 experiments this dose resulted in about 99% inhibition. IVIg was also added after preincubation with 1000 g/mL antiTGF neutralising antibody for 2 h at room temperature. This high dose of neutralising antibody would surely also block a possible TGF2 effect. The results are shown in the table. We found no evidence that the observed immunosuppressive effect of IVIg in vitro is due to TGF, because high doses of a neutralising antibody could not abolish this inhibitory effect. Moreover, with anti-IgG affinity column purification of IVIg, the inhibitory effect was recovered from IgG of the column eluate and not in the void.2 Kekow and co-workers mention the TGF mobility absent in the eluate from a protein-A column. As is commonly the case with IVIg, not one mechanism seems responsible for the many (sometimes opposite) effects observed in vivo and in vitro. Also, extrapolating in-vitro findings to in-vivo application seems too simple with IVIg. Although the 15 patients treated by Kekow and colleagues showed a small increase in plasma concentration of TGF2, they do not say whether this increase correlates with clinical improvement. We support the view that further studies are needed before any conclusions can be drawn on the role of TGF in IVIg. *I N van Schaik, M Vermeulen, A Brand *Department of Neurology, Academic Medical Center, PO Box 22700, 1100 DE Amsterdam, Netherlands; and Deparment of Immunohematology, Academic Hospital, Leiden (e-mail: [email protected])
Mixed lymphocyte reactions
Donor 1 versus donor 2
Donor 2 versus donor 1
Medium Medium+IVIg 30 mg/mL Medium+anti-TGF neutralising antibody 1000 g/mL Medium+IVIg 30 mg/mL and anti-TGF neutralising antibody 1000 g/mL
51 915 296 (99%) 46 046
471 411 401 (99%) 44 588
129 (99%)
206 (99%)
3
H-thymidine incorporation in counts per min (% inhibition) of mixed lymphocyte reactions between unrelated donors by IVIg, anti-TGF neutralising antibody, or both
1288
1
2
3
4
5
Kekow J, Reinhold D, Pap T, Ansorge S. Intravenous immunoglobulins and transforming growth factor . Lancet 1998; 351: 184–85. Van Schaik IN, Lundkvist I, Vermeulen M, Brand A. Polyvalent immunoglobulin for intravenous use interferes with cell proliferation in vitro. J Clin Immunol 1992; 12: 1–10. Anderson UG, Bjork L, Skansen-Saphir U, Andersson JP. Down-regulation of cytokine production and interleukin-2 receptor expression by pooled human IgG. Immunology 1993; 79: 211–16. Klaesson S, Ringdén O, Markling L, Remberger M, Lundkvist I. Immune modulatory effects of immunoglobulins on cell-mediated immune responses in vitro. Scand J Immunol 1993; 38: 477–84. Amran D, Renz H, Lack G, Bradley K, Gelfand EW. Suppression of cytokinedependent human T-cell proliferation by intravenous immunoglobulin. Clin Immunol Immunopathol 1994; 73: 180–86.
Homocysteine and endothelial vascular function Sir—Hyperhomocysteinaemia is an independent risk factor for vascular disease;1 investigators have postulated that it might cause atherosclerosis by damaging the endothelium 2 either directly or by altering oxidative status.3 John Chambers and colleagues (Jan 3, p 36)4 report an association between impaired endothelial function and an acute increase in plasma homocysteine after oral methionine (L-methionine) 0·1 g/kg loading dose. We found no change in endothelial function or oxidation status with methionine supplementation in 16 healthy volunters (median age 23 [range 20–30] years). The study had three phases. First, we assessed the acute effects of randomly allocated methionine 250 mg or placebo on baseline measurements. A second study was carried out after 1 month of treatment with methionine 250 mg or placebo four times daily. For the final phase, eight volunteers were given unblinded treatment with methionine 0·1 g/kg daily for 1 week. We used strain gauge venous occlusion plethysmography to measure forearm blood flow after local intra-arterial infusion of acetylcholine (to assess endothelium-dependent vasodilatation) and sodium nitroprusside (to assess endothelium-independent vasodilatation). Lipid peroxidation was measured as thiobarbituric acid reactive substances (TBARS), expressed as malondialdehyde equivalents. Each volunteer abstained from alcohol and caffeine-containing products and fasted for 6 h before the start of the study. A 27-gauge needle was inserted into the non-dominant
THE LANCET • Vol 351 • April 25, 1998
CORRESPONDENCE
brachial artery to allow local intraarterial drug infusion. A mercury in silastic strain gauge was coupled to an electronically calibrated plethysmograph (Medasonics model SPG16, CA, USA). The voltage output was transferred to a Macintosh personal computer with a MacLab analogue-todigital converter and CHART software (version 3.4.3). Acetylcholine and sodium nitroprusside were infused intra-arterially in four incremental doses for 3 min and forearm blood flow measured in the last min of the infusion. We took the mean of five consecutive forearm-blood-flow measurements for the statistical analysis. Forearm blood flow was expressed as mL/100 mL forearm volume/min. We measured plasma homocysteine by high-performance liquid chromatography. Change in forearm blood flow from baseline was analysed by a two-way ANOVA. Basal blood flow, plasma concentration of homocysteine, and TBARS were analysed by one-way ANOVA. We found no significant difference in homocysteine concentration, TBARS, or endothelial-dependent or endothelial-independent vascular responses after the first administration of methionine or placebo (p>0·05) or after 1 month of treatment (p>0·05). 1 week of methionine 0·1 g/kg led to a significant increase in homocysteine (from 8·2 [95% CI 6·5–10·2] to 20·2 [14·4–26·2] mol/L, p<0·0015), but with no associated change in TBARS or endothelial vascular responses (p>0·05). This finding suggests that acute increases in homocysteine concentrations do not significantly impair endothelial function or oxidative status (as measured by TBARS) in healthy volunteers. *Colm G Hanratty, Daniel F McAuley, Colm McGurk, Ian S Young, G Dennis Johnston *Department of Therapeutics and Pharmacology, Queen’s University of Belfast, Belfast BT9 7BL, UK; and Department of Clinical Biochemistry, Institute of Clinical Science, Royal Victoria Hospital, Belfast 1
2
3
4
Stampfer MJ, Malinow MR, Willeth WC, et al. A prospective study of plasma homocysteine and risk of myocardial infarctions in US physicians. JAMA 1992; 268: 877–81. Loscalzo J. The oxidant stress of hyperhomocyst(e)inemia. J Clin Invest 1996; 98: 5–7. Lentz SR, Sobey CG, Piegors DJ, Bhopatkar MY, Faraci FM, Malinow MR. Vascular dysfunction in monkeys with diet-induced hyperhomocysteinaemia. J Clin Invest 1996; 98: 24–29. Chambers JC, McGregor A, Jean-Marie J, Kooner JS. Acute hyperhomocysteinaemia and endothelial dysfunction. Lancet 1998; 351: 36–37.
THE LANCET • Vol 351 • April 25, 1998
Quinolone-resistant Salmonella typhi in Vietnam SIR—We share the worries of D A Murdoch and colleagues (Jan 31, p 339)1 about the spread of quinoloneresistant Salmonella typhi in Asia. Typhoid fever has been endemic in Vietnam for many years and is a common cause of admission to the Centre for Tropical Diseases (CTD) in Ho Chi Minh City, an infectious disease referral centre for the south of the country.2 80% of blood culture isolates of S typhi at this centre carry plasmidmediated resistance to chloramphenicol, ampicillin, and trimethoprimsulphamethoxazole (co-trimoxazole). Over the past 5 years we have observed a steady increase in the incidence of quinolone-resistant typhoid fever. These isolates have an ofloxacin MIC90 of 0·5 mg/L (the concentration inhibiting growth in 90% of isolates) compared with 0·06 mg/L in sensitive isolates. Although they still appear sensitive to fluoroquinolones by disc sensitivity testing (albeit with reduced zone sizes) they are clinically resistant. Time to fever clearance is prolonged and cure rates are only 50% compared with over 97% for sensitive strains.3 These quinolone-resistant S typhi are characterised by resistance to nalidixic acid (MIC90 128 mg/L). The proportion of quinolone-resistant S typhi at CTD increased slowly from 4% (10/246) in 1993 to 12% (27/228) in the first 9 months of 1997. Since then there has been an alarming increase; over the past 4 months 76% (161/213) of blood culture isolates of S typhi were nalidixic acid (ie, quinolone) resistant. The MICs of these recent isolates to ofloxacin (MIC90 1·0 mg/L) and ciprofloxacin (MIC900·5 mg/L) were significantly higher than that for the nalidixic-acid-resistant isolates seen in the previous 4 years. These resistant strains are sensitive to ceftriaxone, cefixime, and azithromycin, but clinical response to these drugs is slow (fever clearance takes 7 days or more) and failure rates can be over 20%.4,5 These epidemics of quinoloneresistant typhoid fever in Vietnam and Tajikistan1 highlight an approaching crisis in the antibiotic therapy of typhoid fever since resistant infections require expensive treatments which are less effective and associated with higher stool carriage rates, and thus greater transmission potential than quinolonesensitive infections. Long courses of fluoroquinolones at a high dose may be clinically effective, but this would increase the cost of treatment and reassert worries about fluoroquinolone use in children. Full fluoroquinolone resistance is likely to appear soon, under continued selection pressure.
Fluoroquinolone treatment of nalidixic-acid-sensitive typhoid fever in Vietnam costs $US6–10. To treat quinolone-resistant strains a prolonged course of fluoroquinolone would cost $28–42, azithromycin $35–50, oral cephalosporins $80–90, and parenteral cephalosporins $150–200. Treatment may become unaffordable for patients in typhoid endemic areas and the clinical evaluation of new affordable regimens for resistant strains is pressing. We thank N J White for his contribution.
*C Parry, J Wain, N T Chinh, Ha Vinh, J J Farrar Centre for Tropical Diseases, University of Oxford,Oxford, UK; and Wellcome Trust Clinical Research Unit, 190 Ben Ham Tu, Quan 5, Ho Chi Minh City, Vietnam 1
2
3
4
5
Murdoch DA, Banatval NA, Bone A, Shoismatulloer BI, Ward LR, Threlfall EJ. Epidemic ciprofloxacin-resistant Salmonella typhi in Tajikistan. Lancet 1988; 351: 339. Hoa NTT, Diep TS, Wain J, et al. Community acquired septicaemia in southern Vietnam: the importance of multi-drug resistant Salmonella typhi. Trans Roy Soc Trop Med Hyg (in press). Wain J, Hoa NTT, Chinh NT, et al. Quinolone-resistant Salmonella typhi in Vietnam: molecular basis of resistance and clinical response to treatment. Clin Infect Dis 1997; 25: 1404–10. White NJ, Parry CM. The treatment of typhoid fever. Curr Opin Infect Dis 1996; 9: 298–302. Tribble D, Girgis N, Habib N, Butler T. Efficacy of azithromycin for typhoid fever. Clin Infect Dis 1995; 21: 1045–46.
New-variant CreutzfeldtJakob disease and treatment of haemophilia Sir—Tony Baxter and colleagues (Feb 21, p 600)1 challenge the view of the Executive Committee of the UK Haemophilia Centre Directors’ Organisation that recombinant factor VIII (rVIII) is safer than UK domestic factor VIII concentrate in relation to the risk of new variant Creutzfeldt-Jakob Disease (nvCJD). 2 They suggest that the prion protein of nvCJD could also be found in the albumin used as a stabiliser in the present generation of rVIII, and imply that rVIII is no safer than plasmaderived factor VIII. They miss the point. The human form of bovine spongiform encephalopathy is nvCJD, and has, with one exception, not been described outside the UK. Although there is no direct evidence of blood transmission of nvCJD, the prion protein has been detected in tonsils and could be within circulating Blymphocytes. Blood transmission is, therefore, a plausible suggestion which, given the long incubation period of the disease, may take many years to manifest. Of the 22 cases reported in the
1289