Comparison of the performance of three carbapenem inactivation methods for the detection of carbapenemase-producing gram-negative bacilli

IntroductionThe carbapenem inactivation method test (CIM) was developed as a method for detecting carbapenemase-producing Gram-negative bacilli, and the modified CIM (mCIM) was recommended by the CLSI for as an improved method in M100-S27. However, few studies have evaluated the influence of bacterial species and genotype on its sensitivity and specificity. In this study, we evaluate the performance of these improved modified CIM methods with mCIM.MethodsAs strains, clinical isolates from Naga Municipal Hospital and stored strains from the Study of Bacterial Resistance in the Kinki Region of Japan were used. The mCIM, CIM-Tris, and simple CIM (sCIM) test methods were applied to 120 Enterobacterales, 40 Pseudomonas aeruginosa, and 37 Acinetobacter spp. The procedure and criteria for each method were based on the original papers and the CLSI M − 100 S27 documents.ResultsThe sensitivity of the test methods in the detection of carbapenemase in Enterobacterales, Pseudomonas spp., and Acinetobacter spp. was as follows: mCIM, 98.9%, 90.0%, and 76.5%, respectively; CIM-Tris, 94.4%, 100%, 100%; and sCIM 98.9%, 85.0%, 76.5%. All methods showed 100% specificity in Enterobacterales, Pseudomonas spp., and Acinetobacter spp. Each method performed well in the detection of metallo β-lactamase-producing strains, however, the sensitivity tended to be low in the detection of the organisms producing serine-type carbapenemase, such as GES, OXA-23, and OXA-51.ConclusionsCare must be taken when selecting test methods because the sensitivity of the detection differs depending on the bacterial species and genotype.     

Carbapenem resistance and mortality in patients with Acinetobacter baumannii infection: systematic review and meta-analysis

Acinetobacter baumannii has emerged as a major cause of healthcare-associated infections. Controversy exists as to whether antimicrobial resistance increases the risk of mortality. We conducted a systematic review and meta-analysis to examine this association. We searched MEDLINE and EMBASE databases up to May 2013 to identify studies comparing mortality in patients with carbapenem-resistant A. baumannii (CRAB) vs. carbapenem-susceptible A. baumannii (CSAB). A random-effects model was used to pool Odds Ratios (OR). Heterogeneity was examined using I². We included 16 observational studies. There were 850 reported deaths (33%) among the 2546 patients. Patients with CRAB had a significantly higher risk of mortality than patients with CSAB in the pooled analysis of crude effect estimates (crude OR = 2.22; 95% CI = 1.66, 2.98), although substantial heterogeneity was evident (heterogeneity I² = 55%). The association remained significant in the pooled adjusted OR of 10 studies. Studies reported that patients with CRAB compared to patients with CSAB were more likely to have severe underlying illness and also to receive inappropriate empirical antimicrobial treatment, which increases the risk of mortality. Our study suggests that carbapenem resistance may increase the risk of mortality in patients with A. baumannii infection. However, cautious interpretation is required because of the residual confounding factors and inadequate sample size in most studies.     

Risk factors of superinfection following imipenem/cilastatin therapy in hospitalised patients with acute exacerbations of severe chronic obstructive pulmonary disease

Imipenem is often used in treatment of acute exacerbations of severe chronic obstructive pulmonary disease (COPD). Superinfection following imipenem therapy is a common cause of treatment failure and high economic burden. This study is aimed to explore any clinical factors which determine the risk of superinfection after imipenem treatment in acute exacerbations of severe COPD. A prospective observational study was conducted in a 5-bed respiratory intensive care unit of a Chinese University hospital. Fifty-one patients with acute exacerbations of severe COPD who were hospitalised and treated with imipenem for more than 3 days were enrolled during 1.5 year. The associations between the risk of superinfection and potential factors were analysed by logistic regression. Forty-seven out of 51 patients (92.2%) had their symptoms and signs improved at the end of imipenem treatment. Superinfections were developed in 12 patients, and the superinfection rate was as high as 30.8% (12 out of 39 patients with definite bacteriologic responses). The frequent superinfecting organisms were Stenotrophomonas maltophilia and Pseudomonas aeruginosa. Among a wide range of potential risk factors, we found that lower blood pH, previous cephalosporines treatment and longer period of imipenem treatment are independently associated with a higher risk of superinfection. The risk of superinfection following imipenem treatment in hospitalised patients with acute exacerbations of COPD was high. Lower blood pH, previous cephalosporines treatment and longer period of imipenem treatment all increased the risk of superinfection.     

Comparative in vitro pharmacodynamics of BO-2727, meropenem and imipenem against Gram-positive and Gram-negative bacteria

Objective: To investigate and compare the in vitro pharmacodynamics of three carbapenems: imipenem, meropenem and BO-2727.
Method: The following studies were performed: (1) comparative studies of the rate of killing of the three carbapenems of reference strains of Gram-positive and Gram-negative bacteria at a concentration corresponding to the 1-h serum level following 500 mg intravenously in humans; (2) comparative studies of the rate of killing of BO-2727, meropenem and imipenem at different antibiotic concentrations of reference strains of Gram-positive and Gram-negative bacteria; (3) comparative studies of the rate of killing of BO-2727, meropenem and imipenem of bacteria which are phenotypically tolerant; (4) studies of the postantibiotic effect of BO-2727 using viable counts and optical density; (5) studies of the postantibiotic sub-MIC effect (PA SME) of BO-2727 using optical density.
Results: No difference in killing rate was noted between the three carbapenems, and there was no concentration-dependent killing of the Gram-negative strains after 6 h. A pronounced paradoxical effect was seen against Staphylococcus aureus. All three antibiotics were able to kill phenotypically tolerant bacteria. Only very short or no postantibiotic effect of BO-2727 was found against the investigated strains. Very long PA SMEs were noted for the Gram-negative strains, although there was a pronounced variation for the different strains of Pseudomonas aeruginosa.
Conclusions: There was no significant difference between the studied carbapenems in their pharmacodynamic properties. All three antibiotics acted similarly to other β-lactam antibiotics.     

Effectiveness and Safety of Intra-arterial Imipenem/Cilastatin Sodium Infusion for Patients with Hand Osteoarthritis–Related Interphalangeal Joint Pain

PurposeTo evaluate the effectiveness and safety of intra-arterial imipenem/cilastatin sodium (IPM/CS) infusion for painful interphalangeal joint osteoarthritis (OA).Materials and MethodsFifty-eight patients with interphalangeal joint OA who underwent intra-arterial IPM/CS infusion were retrospectively evaluated. Intra-arterial infusions were performed via percutaneous wrist arterial access. The Numerical Rating Scale (NRS), Functional Index for Hand Osteoarthritis (FIHOA), and Patient Global Impression of Change (PGIC) scale scores were assessed at intervals of 1, 3, 6, 12, and 18 months. Clinical success was evaluated based on PGIC.ResultsAll patients were followed up for at least 6 months after treatment. Of them, 30 and 6 patients were followed up for 12 and 18 months, respectively. No severe or life-threatening adverse events were encountered. The mean NRS score was 6.0 ± 1.4 at baseline, which significantly decreased to 2.8 ± 1.4, 2.2 ± 1.9, and 2.4 ± 1.9 at 1, 3, and 6 months after treatment, respectively (all P < .001). The mean NRS scores were 2.8 ± 1.7 and 2.9 ± 1.9 at 12 and 18 months, respectively, in the remaining patients. The mean FIHOA score significantly decreased from 9.8 ± 5.0 at the baseline to 4.1 ± 3.5 at 3 months (P < .001). The mean FIHOA score was 4.5 ± 3.3 at 12 months in the remaining 30 patients. The clinical success rates based on PGIC at 1, 3, 6, 12, and 18 months were 62.1%, 77.6%, 70.7%, 63.4%, and 50.0%, respectively.ConclusionsIntra-arterial IPM/CS infusion is a potential treatment option for interphalangeal joint OA refractory to medical management.