Activity of Ceftolozane-Tazobactam against Burkholderia pseudomallei.

We investigated the in vitro activity of a novel fifth-generation cephalosporin-tazobactam combination, ceftolozane-tazobactam against Burkholderia pseudomallei, the etiological agent of melioidosis. Using both disc diffusion and minimum inhibitory concentration (MIC) strip techniques against 56 clinical isolates and an national collection of type cultures (NCTC) strain, the MIC to ceftolozane-tazobactam was found to be between 0.75 and 4 mcg/mL. The MIC50 was found to be 1.5 mcg/mL and MIC90 was 2.0 mcg/mL. This study provides initial evidence of ceftolozane-tazobactam as a novel agent in the management of melioidosis.

Epidemiological cut-off value of clinical isolates of Burkholderia pseudomallei from Northern Queensland to meropenem, ceftazidime, trimethoprim/sulfamethoxazole and doxycycline by the microbroth dilution method.

OBJECTIVES: Melioidosis is caused by the bacterium Burkholderia pseudomallei. The most common antibiotics used to treat melioidosis in Australia are meropenem, ceftazidime, trimethoprim/sulfamethoxazole (SXT) and doxycycline. The European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Clinical and Laboratory Standards Institute (CLSI) do not provide standards for assessing the susceptibility of B. pseudomallei for these agents. The International Standards Organisation (ISO) microbroth dilution method is accepted both by the CLSI and EUCAST as the gold standard of antimicrobial susceptibility testing. Many previous studies of the susceptibility of B. pseudomallei used Etest or disk diffusion and presented the results as aggregate data. Etest and disk diffusion methods have not been standardised for B. pseudomallei and aggregate data cannot be used to determine an epidemiological cut-off value (ECOFF). An ECOFF is vital for the setting of clinical breakpoints. METHODS: In this study, minimum inhibitory concentrations (MICs) of meropenem, ceftazidime, SXT and doxycycline were assessed by microbroth dilution for a library of 234 well characterised clinical isolates of B. pseudomallei from Northern Queensland, Australia. RESULTS: The resultant histograms and aggregate data represent the first MIC profile of a large library of B. pseudomallei that has been successfully produced using microbroth dilution. CONCLUSIONS: The MIC profiles can be used to contribute towards a determination of an ECOFF for this species for these agents, which will aid in the setting and refining of clinical breakpoints for the most important antimicrobials used to treat melioidosis.

Evaluation of the Remel RapID NF plus rapid biochemical method for identification of Burkholderia pseudomallei.

Typical methods for the identification of Burkholderia pseudomallei colonies produce results in 18 h. The Remel RapID NF Plus kit produces results in 4 h. We used the kit for 190 stored B. pseudomallei isolates and correctly identified 189 of them. This kit produces consistent results for known B. pseudomallei isolates.

Comparative in vitro susceptibility of Burkholderia pseudomallei to doripenem, ertapenem, tigecycline and moxifloxacin.

Burkholderia pseudomallei, the causative agent of melioidosis, continues to present therapeutic challenges in endemic areas. A number of clinical issues have prompted consideration of alternative antimicrobial therapies. These include stability in 24-h infusion pumps, broad-spectrum coverage in the empirical treatment of community-acquired pneumonia, cost, the need for effective oral agents and rare reports of emerging resistance. This study aimed to examine the in vitro susceptibility of B. pseudomallei to four new antimicrobial agents, namely moxifloxacin, tigecycline, ertapenem and doripenem. A total of 100 clinical isolates were tested by Etest and disk diffusion. As there are no interpretative standards for these antimicrobials, MIC(90) values (minimum inhibitory concentrations for 90% of the isolates) were compared with those for meropenem. MIC values for each agent were correlated with zone of inhibition diameters. MICs for doripenem were broadly similar to those for meropenem, with a MIC(90) of 1.5 µg/mL (range 0.38-4 µg/mL). There was good correlation (r=-0.71; P<0.001) between the MIC and disk diffusion for doripenem. Ertapenem, tigecycline and moxifloxacin had limited in vitro activity in this study, although no interpretative criteria exist for these agents. Further in vitro, animal and clinical studies are suggested to validate the efficacy of doripenem in the management of melioidosis.

Trichophyton tonsurans-Ringworm in an NICU.

Ringworm is very rarely found in the neonate, especially infants who have been confined from birth to an intensive care unit. We report an infection with the dermatophyte Trichophyton tonsurans, the most common cause of tinea capitis in children but not yet described in a premature baby who has never left the nursery. Our case illustrates the need to consider this diagnosis among the causes of dermatitis in the newborn, especially in at-risk populations such as indigenous Australians. Though our infant's presentation was the classic "ring" shape, a literature review revealed varied presentations. In contrast to the usual need for long-term antifungal medication, our case responded rapidly to a topical azole preparation. Although we did not screen visiting family members, screening would have been appropriate, and those found positive might have benefited from at least antifungal shampoo.

Comparison of routine bench and molecular diagnostic methods in identification of Burkholderia pseudomallei.

This study compared the identification of Burkholderia pseudomallei with that of related organisms. Bench tests and latex agglutination were compared with molecular identification. Using bench tests and latex agglutination alone, 100% (30/30) of B. pseudomallei isolates were correctly identified. Amoxicillin-clavulanate susceptibility testing was also a good and simple discriminatory test.

Activity of tigecycline in the treatment of acute Burkholderia pseudomallei infection in a murine model.

Burkholderia pseudomallei is the causative agent of melioidosis. Standard therapy includes ceftazidime alone or in combination with co-trimoxazole. Tigecycline, a novel agent, has displayed activity against B. pseudomallei. We evaluated the in vivo efficacy of tigecycline using a murine model of melioidosis. Mice were infected with either a high or low virulence B. pseudomallei isolate followed by administration of antibiotics alone or in combination (tigecycline, ceftazidime, tigecycline plus ceftazidime) for 7 days. Bacterial loads were assessed up to 7 days and survival was determined up to 7 days post infection. Tigecycline in combination with ceftazidime was the most effective and conferred the lowest mortality, suggesting the use of this new agent in B. pseudomallei infection.