Typhoid Fever in Africa:

Emerging Flouroquinolone Resistance

S KARIUKI1,3, G REVATHI2, J MUYODI1, J MWITURIA1, A MUNYALO1, S MIRZA3, CA

HART3

1Centre for Microbiology Research, KEMRI, Kenya, 2Department of Medical

Microbiology, Kenyatta National Hospital, Kenya, 3Department of Medical

Microbiology and Genito-Urinary Medicine, Liverpool, UK.

 Introduction

• Salmonella Typhi : cause >10 million cases, 600,000 deaths / year, mainly in developing countries.

• Comprise 8-10% of all Salmonella serotype isolations in Kenya.

• MDR S. Typhi increasingly reported in Africa; chloramphenicol, ampicillin or cotrimoxazole increasingly ineffective.

 Methods

• Between 1999 – 2000: 140 S. Typhi from blood cultures of adults (104) and children (36).

• 3 different regions of the country.

 Methods

• Identification by serotype and phage type

• Antibiotic susceptibility testing - MIC using

E-test method

• Plasmid isolation and in-vitro conjugation

tests

• Genomic DNA characterisation by PFGE

 Methods PCR

• PCR of RepHI1A replicon, present in IncHI plasmids

• PCR of gyrA, gyrB, parC and parE genes within

QRDR

• Digestion with 5 U of Hinf I – determine HinfI

mutations in gyrA site

RESULTSAntimicrobial susceptibility

• Only 19/140 (13.7%) fully susceptible to all drugs tested.

• 82.3% were MDR Strains high MICs

• Ampicillin,chloramphenicol, tetracycline, (MICs > 256µg/ml), streptomycin (MIC > 1024µg/ml) and cotrimoxazole (MIC> 32µg/ml)

RESULTSMICs for Quinolones n=140

MICs (g/mL)

Mode Range

Non-MDR* S. Typhi Nalidixic Acid Ciprofloxacin MDR S. Typhi Nalidixic Acid Ciprofloxacin

2 0.016 8 0.25

1-4 0.016 – 0.032 8-16 0.25 – 0.38

RESULTSPhenotypes and Genotypes of S.

Typhi

 

S. Typhi No. of No. (%) with XbaI and SpeI PFGE patterns

From isolates raised QMICs No. (%) isolates

Pattern I Pattern 2

MDR Sensitive MDR Sensitive

KNH 105 47 (44.7) 42 (40) 13 (12) 47 (44.7) 3 (2.8)

Embu 32 16 (50) 20 (64) 0 9 (28.6) 3 (9.3)

Nakuru 3 3 (100) 0 0 3 (100) 0

RESULTSPCR of QRDR

• No resultant mutations observed after sequencing PCR products of high Quinolone MIC strains.

 

Plasmids

• Resistance encoded on a 110-kb self-transferable plasmid of incHI1 incompatibility group.

• Increase in MICs of the quinolones had not resulted from any significant mutation

Inc groups of S. Typhi

1 2 3 4 5 6 7 8 9 10 11 M

365 bp

Genotypes of S. Typhi

M 1 2 3 4 5 6 7

Conclusions

• Prior to 1991, all S. Typhi were fully susceptible to Abs

• Resistance 1st seen 1992, at 25%

• 1997 at 68% steadily rising to 76% by 2002.

CONCLUSIONS

• Two main genotypes in circulation – both S and R strains.

• NalR and Cipro high MIC strains (47%) have 10X MIC of sensitive strains

• Rx failures already being observed even within sensitive MIC bracket.

References1. Kariuki S, Revathi G, Muyodi J, Mwituria J, Munyalo A, Mirza S, Hart CA.

Characterization of multidrug-resistant typhoid outbreaks in Kenya. J Clin Microbiol. 2004 Apr;42(4):1477-82.

2. Kariuki S, Gilks C, Revathi G, Hart CA. Genotypic analysis of multidrug-resistant

Salmonella enterica Serovar typhi, Kenya. Emerg Infect Dis. 2000 Nov-Dec;6(6):649-51

3. Kariuki S, Hart CA. Global aspects of antimicrobial-resistant enteric bacteria. Curr Opin Infect Dis. 2001 Oct;14(5):579-86.