State public health laboratories receive Salmonella
isolates from clinical diagnostic laboratories as part of routine surveillance. State and local health department officials report demographic, clinical, and travel information about laboratory-confirmed typhoid fever on a standard form to the Centers for Disease Control and Prevention (CDC, Atlanta, GA, USA). Participating states began submitting all S. enterica
serotype Typhi isolates to NARMS in 1999; since 2003, all state public health laboratories have participated. Isolates were tested for susceptibility by using broth microdilution (Sensititre; Trek Diagnostics, Westlake, OH, USA). MICs were determined for 15 antimicrobial agents and interpreted by using Clinical and Laboratory Standards Institute (CLSI) criteria when available () (7,13
). For ciprofloxacin-resistant isolates, subtyping by pulsed-field gel electrophoresis (PFGE) was performed by using the protocol established by the National Molecular Subtyping Network for Foodborne Disease Surveillance (PulseNet) (14
). PFGE pattern similarity was assessed by cluster analysis (Dice, UPGMA [unweighted pair group method using arithmetic averages]) and band-matching applications of BioNumerics software (Applied Maths, Sint-Martens-Latem, Belgium) and confirmed by visual comparison (). For ciprofloxacin-resistant isolates detected for 1999–2005, sequencing of the quinolone resistance–determining region (QRDR; defined as amino acids 67–106 for gyrA
) was performed according to the methods described by Crump et al. (6
), and additional patient information (e.g., antimicrobial drug treatment) was requested by using a questionnaire with institutional review board approval.
MICs of antimicrobial agents tested for 9 ciprofloxacin-resistant Salmonella enterica serotype Typhi isolates detected in the National Antimicrobial Resistance Monitoring System, United States, 1999–2008
Figure Pulsed-field gel electrophoresis (PFGE) XbaI (A) and BlnI (B) patterns of 9 ciprofloxacin-resistant Salmonella enterica serotype Typhi isolates detected in the National Antimicrobial Resistance Monitoring System, 1999–2008. PFGE pattern similarity (more ...)
During 1999–2005, we detected 2 (0.1%) cases of ciprofloxacin resistance among 1,690 S. enterica serotype Typhi isolates. Case reports follow.
In 2003, a 1-year-old girl had onset of fever 1 day before arriving in the United States from India. A blood specimen collected 3 days after fever onset yielded S. enterica serotype Typhi. Diarrhea or vomiting at time of specimen collection was not reported. Information about antimicrobial drug treatment was not available. The child was hospitalized for 14 days.
In 2005, a 2-year-old girl had onset of diarrhea, which was treated with ofloxacin, 2 days before she arrived in the United States from India. Seven days later, she continued to have diarrhea, and fever, vomiting, and abdominal cramps developed. She was hospitalized and treated with antimicrobial agents, including ciprofloxacin. Blood and fecal specimens collected 3 weeks after illness onset yielded S. enterica serotype Typhi. The patient was discharged after 14 days of hospitalization. She had lived in India for 6 months before traveling to the United States.
The S. enterica serotype Typhi isolates were resistant to ciprofloxacin (, ) and had indistinguishable PFGE patterns when restriction enzymes XbaI and BlnI were used: PulseNet-designated XbaI pattern JPPX01.0026 and BlnI pattern JPPA26.0110 (; Figure). QRDR sequencing showed gyrA mutations resulting in a serine to tyrosine substitution at codon 83 and an aspartic acid to asparagine substitution at codon 87, and a parC mutation conferring a serine to isoleucine substitution at codon 80.
Table 2 Patient and isolate description, resistance to other antimicrobial agents, PFGE pattern, and travel reported for 9 ciprofloxacin-resistant Salmonella enterica serotype Typhi infections detected in the National Antimicrobial Resistance Monitoring System, (more ...)
Seven (0.6%) ciprofloxacin-resistant infections were detected among patients from whom 1,131 S. enterica serotype Typhi isolates were submitted during 2006–2008 (). The 7 cases occurred in 2006 and 2007. Patients were a median of 22 years of age (range 5–48 years); 5 (71%) were male. All 6 patients with known travel histories reported travel to India in the 30 days before illness onset. In addition to XbaI JPPX01.0026 and BlnI JPPA26.0110, 3 different XbaI and BlnI pattern combinations were detected in the 7 isolates (; Figure).