Treatment of Morganella morganii UTI in a 2-Year-Old Child
Treat this 2-year-old child with oral trimethoprim-sulfamethoxazole or a third-generation cephalosporin (cefixime, cefpodoxime) for 7-14 days, guided by antibiotic susceptibility testing, as Morganella morganii is specifically listed as a susceptible organism for TMP-SMX and responds well to third-generation cephalosporins in pediatric UTIs. 1, 2
Initial Antibiotic Selection
- Trimethoprim-sulfamethoxazole is FDA-approved specifically for UTIs caused by Morganella morganii and should be considered first-line if local resistance patterns are favorable 1
- Third-generation cephalosporins (cefixime, cefpodoxime, cefprozil) are recommended first-line options by the American Academy of Pediatrics for pediatric UTIs and show excellent activity against M. morganii 3, 2
- Oral therapy is appropriate for this child unless they appear toxic, cannot retain oral medications, or have uncertain medication compliance 3, 4
Antibiotic Susceptibility Considerations
- M. morganii typically shows 100% susceptibility to ceftazidime, cefepime, carbapenems, and piperacillin-tazobactam 2
- Almost all pediatric patients with M. morganii UTIs respond well to third-generation cephalosporin therapy 2
- Test the isolate for AmpC β-lactamase production, as M. morganii can harbor blaDHA genes that confer resistance to multiple antibiotics 5, 6
- Gentamicin combined with a third-generation cephalosporin is recommended for invasive M. morganii infections, though this is typically reserved for more severe presentations 5
Treatment Duration and Monitoring
- Administer antibiotics for 7-14 days total, as shorter courses (1-3 days) are inferior for pediatric UTIs 3, 4, 7
- The child should show clinical improvement within 24-48 hours of starting appropriate antibiotics 3, 7
- Adjust therapy based on culture and sensitivity results when available 3, 4, 7
Special Considerations for This Pathogen
- M. morganii is an opportunistic pathogen that commonly causes UTIs in children with underlying conditions, particularly nephrotic syndrome (72.7% of cases) or immunosuppression 2
- Evaluate for underlying urologic abnormalities or immunosuppression, as these are significant risk factors for M. morganii UTI in children 2
- Most pediatric M. morganii UTIs present as lower tract infections with normal or slightly elevated inflammatory markers 2
Critical Pitfalls to Avoid
- Do not use nitrofurantoin for this infection, especially if the child is febrile, as it does not achieve adequate serum concentrations to treat pyelonephritis 3, 4, 7
- Avoid empiric use of TMP-SMX without considering local resistance patterns, as E. coli resistance can reach 19-63% in some areas (though M. morganii remains susceptible) 3, 1
- Do not treat for less than 7 days, as this increases treatment failure rates 3, 4, 7
- Be aware that M. morganii can develop multidrug resistance and may carry resistance genes like blaNDM-1, requiring susceptibility-guided therapy 5, 8