The role of the microbiology laboratory in the diagnosis of multidrug-resistant Gram-negative bacilli infections. The importance of the determination of resistance mechanisms.

Early diagnosis and treatment has an important impact on the morbidity and mortality of infections caused by multidrug-resistant bacteria. Multidrug-resistant gram-negative bacilli (MR-GNB) constitute the main current threat in hospitals and especially in intensive care units (ICU). The role of the microbiology laboratory is essential in providing a rapid and effective response. This review updates the microbiology laboratory procedures for the rapid detection of BGN-MR and its resistance determinants. The role of the laboratory in the surveillance and control of outbreaks caused by these bacteria, including typing techniques, is also studied. The importance of providing standardized resistance maps that allow knowing the epidemiological situation of the different units is emphasized. Finally, the importance of effective communication systems for the transmission of results and decision making in the management of patients infected by BGN-MR is reviewed.

[Infections in patients colonized with carbapenem-resistant Gram-negative bacteria in a medium Spanish city]. / Infecciones en pacientes colonizados con bacterias gramnegativas resistentes a carbapenémicos en una ciudad media española.

OBJECTIVE: Because there are few studies on the clinical implications of colonization by carbapenem-resistant gram-negative bacteria (CRB) this was analyzed in rectal smears (RS) and pharyngeals (PS) and its ability to predict infection/colonization. METHODS: A cross-sectional, retrospective study from adult inpatients between January 2016 and December 2019 was conducted. The isolates were characterized by MicroScan and spectrometry of masses applying EUCAST 2018 cutoff points. The detection of carbapenemases was performed by PCR and Sanger sequencing; sequencies was assigned by MLST. The genetic relationship between the clinical isolates was made by pulsed field electrophoresis using the enzymes Xbal, Spel or Apal. RESULTS: A total of 308 (86.03%) RS and 50 (13.97%) positive PS were detected, the RS had a 85% sensibility, 100% specificity, 100% positive predictive value and 97% negative predictive value. In RS, the following were isolated: 44% (n=135) Acinetobacter baumannii, 26% (n =80) Enterobacterales (20 KPC, 29 OXA-48, 22 VIM, 2 IMP, 7 NDM), 17% (n=53) Pseudomonas aeruginosa and 13% (n=40) Stenotrophomonas maltophilia. In the PS were isolated 44% (n=22) S. maltophilia, 40% (n = 20) A. baumannii, 8% (n=4) P. aeruginosa and 8% (n=4) Enterobacterales (3 VIM, 1 OXA). From the patients with simultaneous RS and PS, 41 (40.6%) had positivity in both smears, 45 (44.6%) only in RS and 15 (14.9%) only in PS. Colonization preceded infection in 81.3% (n=13) of the isolates; association between infection and colonization was found (p<0.001; χ2); and the episodes where the information was found all the isolates from the clinical samples and from the smears were similar. CONCLUSIONS: The probability of predicting infection through the CRB colonized in different clinical samples is feasible. The RS has a major sensibility to detect colonization.

Epidemiologic changes in bloodstream infections in Andalucía (Spain) during the last decade.

OBJECTIVES: During the last decade, some changes in the epidemiology of invasive infections have been reported; however, specific studies with patient-level data are scarce. The aim of this study was to describe and evaluate the epidemiologic changes in bloodstream infections (BSI) during the last decade in Andalucía, Spain. METHODS: Data from two prospective cohorts of BSI in adults with the same methodology performed 10 years apart in 11 hospitals (eight tertiary and three community) in Andalucía, Spain, were compared; the 2006-7 cohort study was performed between October 2006 and March 2007, and the 2016-17 cohort study was performed between October 2016 and March 2017. Population-based incidence rates were calculated and extrapolated for 1 year. Relative risk ratios were calculated between the 2 periods. Multivariate analyses were performed by logistic regression. RESULTS: Overall, 1262 episodes of BSI were included, 563 (44.6%) in 2006-7 and 699 (55.3%) in 2016-17. Multivariate models selected the following changes in patients' features in 2016-17, after controlling for type of acquisition: higher age (odds ratio (OR) = 1.02; 95% confidence interval [CI] 1.01-1.03), lower urinary catheter (OR = 0.37; 95% CI, 0.26-0.48) and lower Pitt score (OR = 0.76; 95% CI, 0.71-0.82). Adjusted estimations considering patients' features and exposure to procedures showed a reduction in coagulase-negative staphylococci (OR = 0.47; 95% CI, 0.32-0.69), and an increase in Proteus spp. (OR = 3.12; 95% CI, 1.18-8.23) and Candida spp. (OR = 3.01; 95% CI, 1.03-8.86). CONCLUSIONS: We found relevant epidemiologic changes in BSI in our area, including rates, frequency of acquisition types, changes in patient's profiles and aetiologic agents.

First report of linezolid dependence in methicillin-resistant Staphylococcus aureus.

Linezolid is used to treat infections caused by methicillin-resistant Staphylococcus aureus (MRSA). We describe the first report of linezolid dependence in MRSA. The strain was isolated from a respiratory sample of a cystic fibrosis patient, and it showed a thymidine-dependent small-colony variant phenotype. The effect was not related to any known mechanisms implicated in S. aureus resistance to linezolid. The clinical significance of this phenomenon needs further investigation.

Sustained leukaemic phenotype after inactivation of BCR-ABLp190 in mice.

Pharmacological inactivation of cancer genes or products is being used as a strategy for therapy in oncology. To investigate the potential role of BCR-ABLp190 cessation in leukaemia development, we generated mice carrying a tetracycline-repressible BCR-ABLp190 transgene. These mice were morphologically normal at birth, and developed leukaemias. Disease was characterized by the presence of B-cell blasts co-expressing myeloid markers, reminiscent of the human counterpart. BCR-ABLp190 activation can initiate leukaemia in both young and adult mice. Transitory expression of BCR-ABLp190 is enough to develop leukaemia. Suppression of the BCR-ABLp190 transgene in leukaemic CombitTA-p190 mice did not rescue the malignant phenotype, indicating that BCR-ABLp190 is not required to maintain the disease in mice. Similar results were obtained by inactivation of BCR-ABLp190 with STI571 (Gleevec; Novartis, East Hanover, NJ, USA) in leukaemic CombitTA-p190 mice. However, gradual suppression of BCR-ABLp190 in leukaemic CombitTA-p190 mice identified a minimum level of BCR-ABLp190 expression necessary to revert the specific block in B-cell differentiation in the leukaemic cells. Overall, the findings indicate that BCR-ABLp190 appears to cause epigenetic and/or genetic changes in tumour-maintaining cells that render them insensitive to BCR-ABLp190 inactivation.

Spread of amikacin resistance in Acinetobacter baumannii strains isolated in Spain due to an epidemic strain.

Sixteen amikacin-resistant clinical Acinetobacter baumannii isolates from nine different hospitals in Spain were investigated to determine whether the high incidence of amikacin-resistant A. baumannii was due to the dissemination of an amikacin-resistant strain or to the spread of an amikacin resistance gene. The epidemiological relationship studied by repetitive extragenic palindromic PCR and low-frequency restriction analysis of chromosomal DNA showed that the same clone was isolated in eight of nine hospitals, although other clones were also found. The strains were studied for the presence of the aph(3')-VIa and aac(6')-I genes, which encode enzymes which inactivate amikacin, by PCR. All 16 clinical isolates had positive PCRs with primers specific for the amplification of the aph(3')-VIa gene, whereas none had a positive reaction for the amplification of the aac(6')-I gene. Therefore, the high incidence of amikacin resistance among clinical A. baumannii isolates in Spain was mainly due to an epidemic strain, although the spread of the aph(3')-VI gene cannot be ruled out.