Estimating the association between antibiotic exposure and colonization with extended-spectrum ß-lactamase-producing Gram-negative bacteria using machine learning methods: a multicentre, prospective cohort study.

OBJECTIVES: The aim of the study was to measure the impact of antibiotic exposure on the acquisition of colonization with extended-spectrum ß-lactamase-producing Gram-negative bacteria (ESBL-GNB) accounting for individual- and group-level confounding using machine-learning methods. METHODS: Patients hospitalized between September 2010 and June 2013 at six medical and six surgical wards in Italy, Serbia and Romania were screened for ESBL-GNB at hospital admission, discharge, antibiotic start, and after 3, 7, 15 and 30 days. Primary outcomes were the incidence rate and predictive factors of new ESBL-GNB colonization. Random forest algorithm was used to rank antibiotics according to the risk of selection of ESBL-GNB colonization in patients not colonized before starting antibiotics. RESULTS: We screened 10 034 patients collecting 28 322 rectal swab samples. New ESBL-GNB colonization incidence with and without antibiotic treatment was 22/1000 and 9/1000 exposure-days, respectively. In the adjusted regression analyses, antibiotic exposure (hazard ratio (HR) 2.38; 95% CI 1.29-4.40), age 60-69 years (HR 1.19; 95% CI 1.05-1.34), and spring season (HR 1.25; 95% CI 1.14-1.38) were independently associated with new colonization. Monotherapy ranked higher als combination therapy in promoting ESBL-GNB colonization. Among monotherapy, cephalosporins ranked first followed by tetracycline (second), macrolide (fourth) and cotrimoxazole (seventh). Overall the ranking of cephalosporins was lower when used in combination. Among combinations not including cephalosporins, quinolones plus carbapenems ranked highest (eighth). Among sequential therapies, quinolones ranked highest (tenth) when prescribed within 30 days of therapy with cephalosporins. CONCLUSIONS: Impact of antibiotics on selecting ESBL-GNB at intestinal level varies if used in monotherapy or combination and according to previous antibiotic exposure. These finding should be explored in future clinical trials on antibiotic stewardship interventions. CLINICAL TRIAL REGISTRATION: NCT01208519.

Remarkable geographical variations between India and Europe in carriage of the staphylococcal surface protein-encoding sasX/sesI and in the population structure of methicillin-resistant Staphylococcus aureus belonging to clonal complex 8.

OBJECTIVES: sasX is a colonization-virulence factor that potentially underlies the success of methicillin-resistant Staphylococcus aureus (MRSA) sequence type (ST) 239 in Asia. We aimed to study the spread of sasX and the population structure of MRSA in two geographically distinct regions, Europe and India. METHODS: MRSA (n = 128) from screening and clinical samples from tertiary care patients in 12 European countries (n = 119), and from India (n = 9) were multilocus-sequence-typed and screened for sasX and its carrier φSPß-like prophage by PCR. Whole genome sequencing was performed on sasX-harbouring strains from India (n = 5) and Europe (n = 2) and on a selection non-harbouring sasX (n = 36) (2 × 150 bp, Miseq, Illumina). Reads were mapped to the ST239 reference strain, TW20. RESULTS: sasX and sesI, a sasX homologue native to Staphylococcus epidermidis, were detected in five of the nine Indian MRSA belonging to ST239 and to other sequence types of CC8. In contrast, sasX was restricted to two ST239 strains in Europe. The intact sasX and sesI carrier φSPß-like prophages were ∼80 kb and ∼118 kb, and integrated in the yeeE gene. We identified 'novel' ST239 clades in India and Serbia that showed significant differences in base substitution frequencies (0.130 and 0.007, respectively, Tamura-Nei model) (p <0.05). CONCLUSIONS: Our data highlight dissemination of sasX to non-ST239 sequence types of CC8. Detection of the S. epidermidis-associated sesI in MRSA provided unquestionable evidence of transfer between the two species. Stark differences in evolutionary rates between the novel Indian and Serbian ST239 clades identified here might be due to inherent clade characteristics or influenced by other environmental differences such as antibiotic use.

[Reliabilty of the antibiogram and plasmid profile in detection of epidemic strains of Shigella sonnei]. / Pouzdanost primene antibiograma i plazmidskog profila u prepoznavanju epidemijskih sojeva Shigellae sonnei.

The aim of the study was to investigate and compare the type of resistance to antibiotics and plasmid profile of Shigellae sonnei isolated at epidemics of bacillary dysentery to determine which method was most reliable in the identification of epidemic strains of that bacteria. It was investigated 130 isolates of Sh. sonnei isolated from the stools of patients in 14 epidemics of bacillary dysentery in Yugoslav Army and citizens in period from 1987 to 1993 year. On the basis of identity of studied features of all isolates originated from one epidemic, epidemic strains of Sh. sonnei could be identified in 10 (71.4%) of 14 studied epidemics by means of plasmid profile, and in 8 (57.1%) epidemics by means of determination of resistance type to antibiotics. According to that, the method of plasmid profile analysis is more reliable in identification of Sh. sonnei epidemic strains compared to the method of determination of resistance type to antibiotics.