Increasing prevalence of multidrug-resistant non-typhoidal salmonellae, Kenya, 1994-2003

Over the last decade there has been a steady increase in the proportion of multidrug resistance among non-typhoidal salmonellae (NTS) isolated from adult patients with bacteraemia in Kenya. The prevalence of NTS multiply resistant to all commonly available drugs including ampicillin, streptomycin, co-trimoxazole, chloramphenicol and tetracycline rose from 31% in 1994 to 42% at present, with concomitantly higher MICs of each drug. Resistance is encoded on large self-transferable 100-110 kb plasmids. Pulsed field gel electrophoresis of XbaI and SpeI digested chromosomal DNA revealed three main digest patterns for Salmonella enterica serotype Typhimurium and two main patterns for Salmonella enterica serotype Enteritidis. Although the genotypes of NTS remained fairly stable over the last decade, the large increase in MICs of all commonly used drugs and increased MICs of ciprofloxacin, poses a major challenge for treatment of invasive NTS infection.     

NRAMP1 and hGPX1 gene polymorphism and response to bacillus Calmette-Guérin therapy for bladder cancer

Background

The natural resistance-associated macrophage protein 1 (NRAMP1) gene is associated with susceptibility to Mycobacterium tuberculosis in humans and to bacillus Calmette-Guérin (BCG) in mice. The detoxification enzyme, human glutathione peroxidase 1 (hGPX1), is associated with recurrence of bladder cancer (BCa).

Objective

To determine whether NRAMP1 and hGPX1 gene polymorphisms correlate with response to BCG immunotherapy for non–muscle-invasive BCa (NMIBC).

Design, setting, and participants

DNA was obtained from the peripheral blood of 99 NMIBC patients who were prospectively randomized to receive postresection intravesical BCG (81 mg [n = 50] or 27 mg [n = 19]) or BCG (27 mg) with interferon alpha (IFN-α; n = 30). The median follow-up time was 60 mo.

Intervention

Intravesical BCG or BCG–IFN-α.

Measurements

Restriction fragment length polymorphism (RFLP) analysis was performed to identify polymorphisms in the NRAMP1 promoter region (GT repeat number) and at position 543 (aspartate [D] and/or asparagine [N] expression) within the NRAMP1 protein (D543N) and position 198 (proline and/or leucine expression) within the hGPX1 protein (Pro198Leu). Data were analyzed using χ² analysis, multivariate analysis, and Kaplan-Meier curves.

Results and limitations

On univariate analysis, the NRAMP1 D543N G:G genotype had decreased cancer-specific survival (CSS; p = 0.036). The hGPX1 CT genotype (Pro-Leu) had decreased recurrence time (p = 0.03) after BCG therapy. On multivariate analysis, patients with the NRAMP1 D543N G:G genotype and allele 3 (GT)n polymorphism had decreased recurrence time (p = 0.014 and p = 0.03) after BCG therapy. The limitation of this study was its small sample size.

Conclusions

Polymorphisms of the NRAMP1 and hGPX1 genes may be associated with recurrence of BCa after BCG immunotherapy.     

Ring chromosome 8 and trisomy 8 in a patient with acute myeloid leukemia

We describe a child with Acute Myeloid Leukemia (AML M7) with trisomy 8 and ring chromosome 8. Ring chromosome 8 associated with AML is uncommon and is reported to have a poor outcome. The combination of trisomy 8 and ring chromosome 8 has not been previously reported. This 15-month-old girl had presented with a history of fever, weight loss of 1 kg, gum bleeds and pallor. Clinical examinations revealed no nodes or organomegaly. Investigations revealed pancytopenia and elevated serum LDH. Bone marrow aspirate confirmed the presence of myeloid blasts positive only for CD 41 and CD 61 on flow cytometry. Chromosomal analysis from the bone marrow showed 46, XX [13]/ 47, XX, +8[2]/ 47, XX, +r (8) [5]. The child was treated as per UK MRC AML protocol (ADE 10+3+5). Bone marrow on day 21 post-induction was in morphological remission. Repeat karyotyping revealed 46,XX suggesting that the patient was in cytogenetic remission. Cytogenetic sub grouping in AML patients provides guidelines for the choice of optimal treatment strategy. There was no HLA matched family donor and hence an unrelated donor search was commenced as she was in the group with unfavourable cytogenetics. She developed acute myelofibrosis soon after the second cycle of chemotherapy with swinging fever and rapidly enlarging spleen. The marrow showed 11% blasts with intense fibrosis. She went through a stormy period during conditioning for unrelated stem cell transplantation. She passed away on day 11 post transplantation of veno-occlusive disease of liver and multiorgan failure. This case illustrates the poor outcome in paediatric AML with trisomy and ring chromosome 8.     

Typhoid in Kenya Is Associated with a Dominant Multidrug-Resistant Salmonella enterica Serovar Typhi Haplotype That Is Also Widespread in Southeast Asia

In sub-Saharan Africa, the burden of typhoid fever, caused by Salmonella enterica serovar Typhi, remains largely unknown, in part because of a lack of blood or bone marrow culture facilities. We characterized a total of 323 S. Typhi isolates from outbreaks in Kenya over the period 1988 to 2008 for antimicrobial susceptibilities and phylogenetic relationships using single-nucleotide polymorphism (SNP) analysis. There was a dramatic increase in the number and percentage of multidrug-resistant (MDR) S. Typhi isolates over the study period. Overall, only 54 (16.7%) S. Typhi isolates were fully sensitive, while the majority, 195 (60.4%), were multiply resistant to most commonly available drugs—ampicillin, chloramphenicol, tetracycline, and cotrimoxazole; 74 (22.9%) isolates were resistant to a single antimicrobial, usually ampicillin, cotrimoxazole, or tetracycline. Resistance to these antibiotics was encoded on self-transferrable IncHI1 plasmids of the ST6 sequence type. Of the 94 representative S. Typhi isolates selected for genome-wide haplotype analysis, sensitive isolates fell into several phylogenetically different groups, whereas MDR isolates all belonged to a single haplotype, H58, associated with MDR and decreased ciprofloxacin susceptibility, which is also dominant in many parts of Southeast Asia. Derivatives of the same S. Typhi lineage, H58, are responsible for multidrug resistance in Kenya and parts of Southeast Asia, suggesting intercontinental spread of a single MDR clone. Given the emergence of this aggressive MDR haplotype, careful selection and monitoring of antibiotic usage will be required in Kenya, and potentially other regions of sub-Saharan Africa.Typhoid fever, caused by Salmonella enterica serovar Typhi, is an important disease in many developing countries. It is estimated that there are approximately 22 million typhoid cases and ∼200,000 deaths per year worldwide (10). However, the true global distribution of typhoid fever is not well documented. For example, in Africa the overall burden of typhoid fever remains largely unknown, mainly because facilities capable of performing the blood culture tests essential for diagnosis are absent from many regions. Some local estimates of typhoid incidences in different African regions have been made. Typhoid incidence rates of 39/100,000 and 59/100,000 have been reported for Kenya/East Africa and Egypt, respectively (10, 28), but these figures may be underestimates due to underreporting, as only severely ill patients seek treatment in hospitals. In other studies, Weeramanthri et al. (30) observed that over a 5-year period typhoid remained a common cause of septicemic illness in The Gambia, while in Nigeria (2) and Ghana (5), cases of ileal perforation due to typhoid were documented.Problems are also emerging with the clinical treatment of typhoid in resource-poor settings. For many years, the antibiotics chloramphenicol, ampicillin, and cotrimoxazole formed the mainstays of typhoid treatment. However, outbreaks of multidrug-resistant (MDR) S. Typhi (20, 24, 25) prompted the widespread use of fluoroquinolones, such as ciprofloxacin and ofloxacin. Fluoroquinolone usage was followed by the emergence of nalidixic acid-resistant S. Typhi exhibiting reduced susceptibility to fluoroquinolones in the early 1990s (18, 22), and it has since become widespread (1, 12, 16, 19, 25). Thus, the spread of MDR and fluoroquinolone resistance in S. Typhi presents significant clinical challenges.Better methods for monitoring the emergence and spread of MDR S. Typhi would facilitate disease control and treatment. However, this monophyletic (clonal) pathogen presents particular challenges in this regard. Studies on the population structure of S. Typhi have shown that this human-adapted pathogen exhibits extremely limited genetic variation, challenging our ability to develop discriminatory tools of value in the field (3, 11, 25, 27). However, the application of novel deep-sequencing and bioinformatics approaches has succeeded in stratifying the S. Typhi population into distinct phylogenetic lineages based on over 1,000 single-nucleotide polymorphisms (SNPs) distributed throughout the chromosome. Typing of these chromosomal SNPs allows isolates from typhoid patients to be mapped to specific points on the phylogenetic tree of S. Typhi (11, 27). This provides an unequivocal test of the genetic relatedness of multiple S. Typhi isolates, which can be inferred from their relative positions in the phylogenetic tree. In particular, isolates sharing identical haplotypes, mapping to the leaf nodes of the S. Typhi phylogenetic tree, are deemed to be very closely related even if they are isolated in widely different geographical locations.In Kenya, MDR S. Typhi isolates from adults and school age children associated with sporadic outbreaks in resource-poor settings, especially in slum areas, have been reported (13, 15). Here, we analyzed a collection of 323 S. Typhi isolates from three hospitals in Nairobi, Kenya, between 1988 and 2008 for their population structure. We used a novel SNP-typing method capable of simultaneously interrogating ∼1,500 points of potential variation on the S. Typhi genome in a single DNA sample. Using this powerful high-throughput approach, we show that a particular MDR-associated haplotype, H58, previously shown to be widespread in several countries in Asia, has become dominant in Kenya, replacing more divergent antimicrobial-susceptible S. Typhi strains.     

Phase 2 study of pegylated liposomal doxorubicin, vincristine, decreased-frequency dexamethasone, and thalidomide in newly diagnosed and relapsed-refractory multiple myeloma

OBJECTIVE: To evaluate the efficacy and safety of adding thalidomide to the pegylated liposomal doxorubicin, vincristine, and decreased-frequency dexamethasone (DVd) regimen for multiple myeloma. PATIENTS AND METHODS: Patients newly diagnosed as having active multiple myeloma and those with relapsed-refractory disease were studied between August 2001 and October 2003. Patients received DVd as previously described. Thalidomide was given at 50 mg/d orally and the dose increased slowly to a maximum of 400 mg/d. At the time of best response, patients received maintenance prednisone, 50 mg orally every other day, and daily thalidomide at the maximum tolerated dose for each patient. The primary end point was the rate of complete responses plus very good partial responses as defined by the European Group for Blood and Marrow Transplantation criteria and the Intergroupe Fran?ais du Myélome, respectively. RESULTS: Of 102 eligible patients, 53 were newly diagnosed as having multiple myeloma, and 49 had been previously treated for multiple myeloma. The complete response plus very good partial response rate was 49% and 45%, with an overall response rate of 87% and 90% for patients with newly diagnosed and previously treated multiple myeloma, respectively. Furthermore, better responses were associated with improved progression-free and overall survival. The most common grade 3 and 4 adverse events were thromboembolic events (25%), peripheral neuropathy (22%), and neutropenia (14%). CONCLUSIONS: The addition of thalidomide to the DVd regimen significantly improves the response rate and quality of responses compared with the DVd regimen alone. This improvement is associated with longer progression-free and overall survival. The rate of observed quality responses is comparable to responses seen with high-dose therapy.