The efficacy of immediate versus delayed antibiotic administration on bacterial growth and biofilm production of selected strains of uropathogenic Escherichia coli and Pseudomonas aeruginosa.
OBJECTIVE
The treatment of urinary tract infections (UTI) with antibiotics is commonly used, but recurrence and antibiotic resistance have been growing and concerning clinicians. We studied whether the rapid onset of a protective biofilm may be responsible for the lack of effectiveness of antibiotics against selected bacteria.


METHODS
Two established uropathogenic Escherichia coli strains, UTI89 and CFT073, and two Pseudomonas aeruginosa strains, PA01 and Boston-41501, were studied to establish a reliable biofilm formation process. Bacterial growth (BG) was determined by optical density at 600 nm (OD 600) using a spectrophotometer, while biofilm formation (BF) using crystal violet staining was measured at OD 550. Next, these bacterial strains were treated with clinically relevant antibiotics, ciprofloxacin HCl (200 ng/mL and 2 μg/mL), nitrofurantoin (20 µg/mL and 40 µg/mL) and ampicillin (50 µg/mL) at time points of 0 (T0) or after 6 hours of culture (T6). All measurements, including controls (bacteria -1% DMSO), were done in triplicates and repeated three times for consistency.


RESULTS
The tested antibiotics effectively inhibited both BG and BF when administered at T0 for UPEC strains, but not when the antibiotic administration started 6 hours later. For Pseudomonas strains, only Ciprofloxacin was able to significantly inhibit bacterial growth at T0 but only at the higher concentration of 2 µg/mL for T6.


CONCLUSIONS
When established UPEC and Pseudomonas bacteria were allowed to culture for 6 hours before initialization of treatment, the therapeutic effect of selected antibiotics was greatly suppressed when compared to immediate treatment, probably as a result of the protective nature of the biofilm.
UT Southwestern Medical Center, Dallas, Texas, USA.
Leah
L
Gandee
UT Southwestern Medical Center, Dallas, Texas, USA.
Jer-Tsong
JT
Hsieh
UT Southwestern Medical Center, Dallas, Texas, USA.
Vanessa
V
Sperandio
UT Southwestern Medical Center, Dallas, Texas, USA.
Cristiano G
CG
Moreira
UT Southwestern Medical Center, Dallas, Texas, USA.
Chih-Ho
CH
Lai
UT Southwestern Medical Center, Dallas, Texas, USA.
Philippe E
PE
Zimmern
D000667:Ampicillin / Q000008:administration & dosage; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D000892:Anti-Infective Agents, Urinary; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D002939:Ciprofloxacin / Q000008:administration & dosage; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects* / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D008826:Microbial Sensitivity Tests; D009582:Nitrofurantoin / Q000008:administration & dosage; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000502:physiology; D012016:Reference Values; D015203:Reproducibility of Results; D013997:Time Factors; D014552:Urinary Tract Infections / Q000188:drug therapy
D000900:Anti-Bacterial Agents; D000892:Anti-Infective Agents, Urinary; D002939:Ciprofloxacin; D000667:Ampicillin; D009582:Nitrofurantoin