The MAST® D68C test: an interesting tool for detecting extended-spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae.

The Mast® D68C test is a phenotypical test that allows the detection of extended-spectrum ß-lactamase (ESBL) production, even in AmpC-producing Enterobacteriaceae. We assessed its detection accuracy against a large collection of 106 Enterobacteriaceae isolates producing a wide diversity of well-characterized ß-lactamases (53 ESBL producers, 25 Amp. producers, seven AmpC and ESBL producers, five carbapenemase producers, three carbapenemase and ESBL producers, one AmpC, carbapenemase, and ESBL producer, three TEM-1 producers, three SHV-1 producers, three OXA-1 producers, and one hyperOXY producer, ATCC 35218, ATCC 25922 [a ß-lactamase-negative control strain]). The results were compared with those of the double disk test and the Clinical and Laboratory Standards Institute (CLSI) confirmatory test for the detection of ESBL. The sensitivity was 90.6 % for the synergy test, 87.5 % for the CLSI method, and only 73.1 % for D68C, which, however, reached 92.1 % if the strains for which supplementary investigations were recommended and the complex mutant TEM (CMT)-producing strains were excluded versus 94.1 % and 88.2 % for the other methods. The specificity was 90.2 % for the synergy test and 100 % for the CLSI method and D68C. D68C was also efficient in detecting AmpC-overproducing strains (sensitivity = 97 %, specificity = 95.9 %): among the 74 strains belonging to natural AmpC-producing species, the sensitivity and specificity were 100 and 94.8 %, respectively. The Mast® D68C-test is a promising method that is easy to perform for the detection of current ESBLs and could also be useful for the detection of plasmid-encoded AmpC enzymes (sensitivity = 100 %).

IS1R-mediated plasticity of IncL/M plasmids leads to the insertion of bla OXA-48 into the Escherichia coli Chromosome.

The OXA-48 carbapenemase is mainly encoded by ∼ 62-kb IncL/M plasmids. However, chromosome-mediated genes have been observed in Escherichia coli isolates. In this work, we investigated the genetic environment of OXA-48 in members of the family Enterobacteriaceae (n = 22) to understand how the OXA-48-encoding gene is transferred into the E. coli chromosome. The OXA-48-encoding gene was located within intact Tn1999.2 transposons in the ∼ 62-kb plasmids or within a truncated variant of Tn1999.2 for the OXA-48-encoding genes located in the chromosomes of E. coli bacteria. The analysis of the Tn1999.2 genetic environment revealed an inverted orientation of the transposon in five ∼ 62-kb plasmids (5/14 [35%]) and in all chromosome inserts (n = 8). The sequencing of pRA35 plasmid showed that this orientation of Tn1999.2 and the acquisition of an IS1R insertion sequence generated a 21.9-kb IS1R-based composite transposon encoding OXA-48 and designated Tn6237. The sequencing of a chromosomal insert encoding OXA-48 also revealed this new transposon in the E. coli chromosome. PCR mapping showed the presence of this element in all strains harboring an OXA-48-encoding chromosomal insert. However, different insertion sites of this transposon were observed in the E. coli chromosome. Overall, these findings indicate a plasticity of the OXA-48 genetic environment mediated by IS1R insertion sequences. The insertion sequences can induce the transfer of the OXA-encoding gene into E. coli chromosomes and thereby promote its persistence and expression at low levels.

Cytobacteriological testing of drainage pus from peritonsillar abscess is not contributive in clinical practice: A STROBE analysis.

PURPOSE: Peritonsillar abscess (PTA) is a frequent pathology. Treatment consists in drainage of the collection, associated to probabilistic antibiotic therapy. The usefulness of cytobacteriological testing (CBT) of the drainage pus is controversial. MATERIAL AND METHODS: A retrospective study of patients managed for PTA between 2013 and 2020 in our university hospital was performed. The main objective was to assess the usefulness of CBT in the management of PTA. The secondary objectives were to determine the bacteriological profile involved in the onset of PTA and to assess the rate of bacterial resistance to antibiotics prescribed on a probabilistic basis. RESULTS: The study included 207 patients: 70 outpatients (33%) and 137 inpatients (67%). Probabilistic antibiotic therapy was implemented in 100% of patients. CBT was performed systematically and was negative in 106 patients, revealing oropharyngeal flora in 40% of cases, polymicrobial flora in 50% and sterile samples in 10%. In the 101 patients with positive CBT, the bacteria isolated were penicillin-sensitive in 99%. All patients were successfully treated. In the light of the bacteriological results, no changes were made to the probabilistic antibiotic therapy introduced on admission. CONCLUSION: CBT on drainage pus had no impact on the management of PTA. CBT is therefore unnecessary in patients with no comorbidities and no signs of severity at admission.

Accuracy of a rapid intrapartum group B Streptococcus test: A new immunochromatographic assay.

OBJECTIVES: To decrease the incidence of early-onset group B streptococcal (GBS) disease, a culture-based screening of all pregnant women at 35-37 weeks is recommended. This gold standard test requires 24-72hours culture. This delay precludes its use for intrapartum screening. This study assesses a new immunoassay, the DIMA test, for identifying GBS-positive patients in the labor ward. MATERIALS AND METHODS: This was a prospective observational study of 195 pregnant women presenting with full-term labor at a single site in France between June and August 2012. We assessed the diagnostic accuracy of intrapartum DIMA testing as compared to intrapartum GBS culture and prenatal screening at 35-38 weeks. RESULTS: The DIMA test sensitivity and specificity were 57.1% and 83.2%, respectively, as compared to 42.9% and 97% for prenatal culture screening. CONCLUSION: The DIMA test assay is a rapid and inexpensive test for the detection of maternal GBS colonization in the labor ward. Its sensitivity is higher than antepartum culture but its specificity is lower. Its performance was inferior to that reported for rapid polymerase chain reaction assays.

Four-year epidemiological study of extended-spectrum ß-lactamase-producing Enterobacteriaceae in a French teaching hospital.

Since the end of the last century resistance to oxyimino ß-lactams has steadily increased in Enterobacteriaceae. In the present work we studied extended-spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae strains isolated in the teaching hospital of Clermont-Ferrand, France, between 2006 and 2009. A total of 1368 ESBL-producing isolates were collected. Most of these isolates (69%) were CTX-M-producing Escherichia coli. During the study, the clinical incidence increased by more than 400%, even in the emergency department, and especially in community-acquired infections, as is the case elsewhere in the world. Most of the ESBL-producing isolates remained susceptible to furans and fosfomycin, but only 50% to fluoroquinolons. In conclusion, ESBL-producing bacteria constantly increased during the study period. Unlike many studies, this increase was associated with the wide dissemination of three different CTX-M enzymes: CTX-M-14, CTX-M-15 and CTX-M-1.

Three cases of cutaneous mucormycosis with Lichtheimia spp. (ex Absidia/Mycocladus) in ICU. Possible cross-transmission in an intensive care unit between 2 cases.

Mucormycoses are rare but emerging diseases with poor prognosis caused by ubiquitous fungi from the environment. In November 2008, our teaching hospital experienced three cutaneous mucormycosis due to Lichtheimia spp. (ex Absidia/Mycocladus) in the intensive care and orthopaedic units. Environmental and epidemiological investigations suggested a possible cross-transmission of L. ramosa between two patients in intensive care. This is the first report of possible person-to-person transmission of mucormycosis species. These cases show the ineffectiveness of hydro-alcoholic solutions against spores and underline the need to respect standard precautions to prevent fungi dissemination.