Aims: To examine associations between growth rate within bacterial populations and survival patterns following treatment with antimicrobial agents. Methods and Results: Time survival data were generated for the inactivation of Escherichia coli populations, grown as batch and continuous cultures, exposed to ciprofloxacin, benzalkonium chloride and tetracycline. Timesurvivor plots were biphasic. Surviving cells were collected and immediately re-exposed to agent or were regrown and then re-exposed. Survivors were resistant to immediate challenge with any of the treatment agents. This resistance was lost on regrowth suggesting that survival reflects an expressed phenotype within a subset of the culture (persisters) rather than individual resistant clones or nonspecific quenching of the test agent. The fraction of persisters increased with decreasing growth rate when cultures were prepared in continuous culture. Conclusions: Clonal growth rates within populations were determined by culture of individual cells within microtitre plate wells. The fraction of clones, in batch cultures, growing maximally at rates below the apparent threshold for susceptibility to the test agents was sufficient to explain the results of continuous culture experiments. Significance and Impact of the Study: The presence of persisters in populations of bacteria relate to small subset of cells that are growing only slowly or are metabolically quiescent.
Introduction:Extended-spectrum β-lactamases (ESBLs), including the AmpC type, are important mechanisms of resistance among Klebsiella pneumoniae and Escherichia coli isolates.Objective:The aim of the study was to investigate the occurrence of AmpC-type β-lactamase producers isolated from two hospitals in Tripoli, Libya.Methods:All clinical isolates (76 K. pneumoniae and 75 E. coli) collected over two years (2013-2014) were evaluated for susceptibility to a panel of antimicrobials and were analyzed phenotypically for the ESBL and AmpC phenotype using E-test and ESBL and AmpC screen disc test. Both ESBL and AmpC-positive isolates were then screened for the presence of genes encoding plasmid-mediated AmpC β-lactamases by polymerase chain reaction (PCR).Results:Of the K. pneumoniae and E. coli tested, 75% and 16% were resistant to gentamicin, 74% and 1.3% to imipenem, 71% and 12% to cefoxitin, 80% and 12% to cefepime, 69% and 22.6% to ciprofloxacin, respectively. None of the E. coli isolates were multidrug resistant compared with K. pneumoniae (65.8%). K. pneumoniae ESBL producers were significantly higher (85.5%) compared with (17.3%) E. coli isolates (P <0.0001, OR=4.93). Plasmid-mediated AmpC genes were detected in 7.9% of K. pneumoniae, and 4% E. coli isolates. There was low agreement between phenotypic and genotypic methods, phenotypic testing underestimated detection of AmpC enzyme and did not correlate well with molecular results. The gene encoding CMY enzyme was the most prevalent (66.6%) of AmpC positive isolates followed by MOX, DHA and EBC. Only one AmpC gene was detected in 5/9 isolates, i.e, blaCMY (n=3), bla MOX (n=1), blaDHA (n=1). However, co-occurrence of AmpC genes were evident in 3/9 isolates with the following distribution: bla CMY and blaEBC (n=1), and blaCMY and blaMOX (n=2). Neither blaFOX nor blaACC was detected in all tested isolates. All AmpC positive strains were resistant to cefoxitin and isolated from patients admitted to intensive care units.Conclusion:Further studies are needed for detection of other AmpC variant enzyme production among such isolates. Continued surveillance and judicious antibiotic usage together with the implementation of efficient infection control measures are absolutely required.
The isolation of MDR ESBL-producing uropathogens expressing the CTX-M-15 gene will limit the choices clinicians have to treat their patients with UTIs. Continued surveillance and implementation of efficient infection control measures are required.
There is renewed interest in the therapeutic use of honey, including use in the treatment of infected wounds and burn patients. In this study, we have assessed the antibacterial activity of Libyan floral Hannon honey on Escherichia coli and Staphylococcus aureus, both known to infect wounds. The effects of four concentrations (5%–30%) of honey were compared with that of four antibiotics (ampicillin, tetracycline, polymyxin, and ciprofloxacin) on the growth of these bacteria at early log, mid log, and late log phases. It has been shown that E. coli and S. aureus are to some degree susceptible during mid log phase compared with late log phase, demonstrated by their complete resistance to antibiotics. Chemostat culture was used to investigate the effect of honey on E. coli grown at a steady state with specific growth rates between 0.1 to 0.5 hour−1. The rate of killing was distinctively clear during the two stages of growth monitored: there was a relatively moderate reduction at the slow growth phase (0.1 to 0.3 hour−1), while a dramatic reduction was obtained at the fast growth phase (0.3 to 0.5 hour−1), reaching a complete reduction at 0.5 hour−1. These results complement data using the cup-cut technique. The antibacterial effect of honey was concentration and time dependent, the bactericidal effect was indeed observed at low concentrations, it demonstrates that the honey has more impact on slow growing bacteria than antibiotics have. We suggest that more reduction could be achieved at higher concentrations of honey. These results may have important clinical implications, such as for the management of wound and burn patients.
Aims: Diabetic foot ulcer is a significant complication of diabetes mellitus and often proceed lower extremely amputation. Propolis is a naturally occurring anti-inflammatory bee derived protectant resin. Previously, topically applied propolis has been reported to reduce inflammation and improves cutaneous ulcer healing in diabetic rodents. This study aimed to determine the Libyan honey and propolis activity and honey against bacteria isolated from diabetic foot ulcer lesion Study Design: In vitro antimicrobial activities of honey and crude hexane and methanolic extract of Libyan propolis against bacteria isolated from diabetic foot ulcer lesion Place and Duration of Study: Samples collected from patient in Tripoli Iben Nafees Hospital using disc and agar diffusion method. Methodology: Disk diffusion method on groups of aerobic and anaerobic bacteria were obtained from diabetic foot lesion. Results: The result showed that the percentage of aerobic bacteria isolated from diabetic lesion Original Research Article
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