Klebsiella pneumoniae carbapenemase (KPC) producer resistant to ceftazidime-avibactam due to a deletion in the blaKPC3 gene.

OBJECTIVES: Carbapenemase-producing strains of Klebsiella pneumoniae (KPC) are a great health concern, and therapy with ceftazidime-avibactam represents a choice for the treatment of infections involving these strains. We report a strain resistant to ceftazidime-avibactam due to a deletion of six nucleotides in the blaKPC gene sequence. METHODS: Two strains, namely AMP920 and AMP2009, were isolated from the same patient a month apart. Antimicrobial susceptibility testing was performed both by broth microdilution and by Etest. Immunoenzymatic assay to detect carbapenemase was performed for both strains. The blaKPC gene of both strains was amplified by PCR and sequenced. Enzyme activity towards carbapenems was tested by the CarbaNP test and hydrolysis spectrophotometer assay. RESULTS: The two isolates differed in antimicrobial susceptibility. AMP920 showed meropenem and imipenem resistance (MIC 32 and 32 mg/mL). A month later the carbapenem MIC decreased to 8 and 1 mg/mL respectively, while the ceftazidime-avibactam MIC increased from 1 to 16 mg/mL. Both isolates showed a positive immunoenzymatic test for the KPC enzyme, but only AMP920 showed a positive CarbaNP test hydrolysing imipenem. The BlaKPC gene was amplified in both strains. After sequencing, the two amplicons showed a KPC3 variant. The gene of the second isolate showed a deletion of six nucleotides at 498-503, resulting in a mutant variant with the deletion of glutamic acid and leucine residues at positions 167 and 168. CONCLUSIONS: We detected a new deletion in the blaKPC gene of a clinical strain of K. pneumoniae which resulted in resistance to ceftazidime-avibactam. The amino acids deleted are in the Ω loop (amino acids 165-179) of the KPC enzyme, enhancing ceftazidime affinity and preventing avibactam binding.

An inhibition of the hypothalamic somatostatinergic tone is not the cause of the enhanced growth hormone response to growth hormone-releasing hormone in patients with liver cirrhosis.

Animal models of liver cirrhosis (LC) display a reduced hypothalamic somatostatinergic tone. To test whether a similar mechanism could explain the enhanced Growth Hormone (GH) secretory response to GH-Releasing Hormone (GHRH), which is seen in human LC, we studied the effect of the cholinesterase inhibitor pyridostigmine (PD), which is able to reduce the release of hypothalamic somatostatin (SS), on the GHRH-stimulated GH secretion. We considered that if PD were unable to increase GH secretion, this would constitute evidence of an already inhibited endogenous somatostatinergic tone. If proved, this in turn could explain the enhanced GH response to GHRH seen in LC. Ten LC patients and nine controls were given GHRH (100 microg, intravenously), or PD (120 mg, orally) plus GHRH. After GHRH alone, the GH peak was four times higher in LC than in controls (40.85+/-15.7 ng/ml in LC and 9.35+/-2.5 ng/ml in controls). In LC, PD administration markedly increased the GH response to GHRH (GH peak: 98.0+/-19.7 ng/ml; +240% vs. GHRH alone). The ability of PD to increase the GH response in patients with LC suggests that in this condition the enhanced GH response to GHRH is not due to a completely inhibited endogenous somatostatinergic tone. SS appears instead to maintain its modulator role on GH secretion in human LC, in contrast with what observed in animal models.

Prevalence of silent celiac disease in patients with autoimmune thyroiditis from Northern Sardinia.

Celiac disease (CD) is frequently associated with other autoimmune diseases such as Type 1 diabetes mellitus, autoimmune thyroiditis (AT), and Addison's disease. The frequency of these associations varies with the populations studied. We conducted this study to ascertain the prevalence of CD in patients with AT from Sardinia, an area with a very high prevalence of CD. To this aim, 297 consecutive patients with AT (as defined by elevated antithyroid antibody levels and a positive ultrasound scan) were studied. Immunoglobulin A and G-class antigliadin antibodies were assayed in serum; if either or both were positive, antiendomysium antibodies were determined. If two markers were positive, serum ferritin, folate, and vitamin B12 levels were measured and jejunal biopsy was suggested. Thirteen out of the 14 patients who showed at least two positive markers consented to jejunal biopsy and all of them showed histological features of CD. The prevalence of CD in AT patients was 4-fold greater than that observed in the general population (4.37 vs 1.06%, p<0.0001). Ferritin was low in 6 and vitamin B12 in 2 out of 13 patients; serum folates were normal in all patients. Molecular typing of HLA class II alleles showed an increased frequency of the extended haplotype DRB1*0301/DQA1*0501/DQB1*0201. None of our patients had a history of gastrointestinal symptoms. We confirm the increased prevalence of silent CD in patients with AT. Patients with AT ought to be regarded as a high-risk group for CD and should be screened routinely for it; if negative, screening tests should be repeated at regular intervals.

Effect of exogenous growth hormone administration on endogenous growth hormone secretion induced by a met-enkephalin analog.

Exogenous growth hormone (hGH) administration in humans attenuates the endogenous growth hormone (GH) response to some pharmacological stimuli; in particular, pretreatment with hGH completely blocks the serum GH response to growth hormone-releasing hormone. In order to evaluate the mechanism(s) whereby opiods induce GH secretion in man, we gave the following treatments to six healthy male volunteers: (a) IV saline; (b) a met-enkephalin analog G-DAMME 250 micrograms IV as a bolus at time 0'; (c) hGH 2 IU as an IV bolus at time -180'; (d) G-DAMME as above, preceded by hGH as above. In our study, G-DAMME stimulated GH secretion both basally (peak 17.9 +/- 6.0 ng/ml) and, to a lesser extent, after hGH pretreatment (6.0 +/- 2.7 ng/ml). Since in our study G-DAMME was able to partially overcome the inhibitory effect of hGH administration, it is suggested that opioids act through an inhibition of somatostatin release and not through a GHRH-dependent pathway. However, an additional direct effect of hGH on pituitary somatotrophes cannot be excluded.