Campylobacter spp. is one of the main cause of bacterial gastroenteritis in the world. The increase of antibiotic resistance in this species is a threat to public health. A Campylobacter spp. surveillance study was performed in Italy in the 2013–2016 period by the Enter-Net Italia network. The most prevalent Campylobacter species identified causing gastroenteritis was Campylobacter jejuni (73.4%) and 45% of all the annual cases of campylobacteriosis were reported in the summer period. High rates of ciprofloxacin and tetracycline resistance in Campylobacter spp. have been observed. An increasing percentage of Campylobacter coli strains simultaneously resistant to ciprofloxacin, tetracycline and erythromycin has been found. Molecular mechanisms of resistance have been investigated and the role of efflux pumps evaluated. Antibiotic resistance in Campylobacter spp. is an increasing serious threat that requires coordinated action to minimize the emergence and spread of antimicrobial resistant strains from animals to humans throughout the food chain.

Background: A collection of human-epidemiologically unrelated S. enterica strains collected over a 3-year period (2016 to 2018) in Italy by the national surveillance Enter-Net Italia was analysed. Methods: Antimicrobial susceptibility tests, including the determination of minimal inhibitory concentrations (MICs) for colistin, were performed. Colistin resistant strains were analysed by PCR to detect mobile colistin resistance (mcr) genes. In mcr-negative S. enterica serovar Enteritidis strains, chromosomal mutations potentially involved in colistin resistance were identified by a genomic approach. Results: The prevalence of colistin-resistant S. enterica strains was 7.7%, the majority (87.5%) were S. Enteritidis. mcr genes were identified only in one strain, a S. Typhimurium monophasic variant, positive for both mcr-1.1 and mcr-5.1 genes in an IncHI2 ST4 plasmid. Several chromosomal mutations were identified in the colistin-resistant mcr-negative S. Enteritidis strains in proteins involved in lipopolysaccharide and outer membrane synthesis and modification (RfbN, LolB, ZraR) and in a component of a multidrug efflux pump (MdsC). These mutated proteins were defined as possible candidates for colistin resistance in mcr-negative S. Enteritidis of our collection. Conclusions: The colistin national surveillance in Salmonella spp. in humans, implemented with genomic-based surveillance, permitted to monitor colistin resistance, determining the prevalence of mcr determinants and the study of new candidate mechanisms for colistin resistance.

According to the data collected at the Rome-based National Reference Centre for Enterobacteria, 266,547 Salmonella strains isolated from human sources (226,513) and from non human sources (40,034) were characterised in Italy during the period 1973-1995. The serotype of all isolates, and the antibiotype and phage type of selected isolates were determined. Human-source isolations grew from 4372 in 1973 to 12,310 in 1995: non-human source isolations, from 339 in 1973 to 3459 in 1995. Salm. Typhimurium ranked first in the list of the most common serotypes isolated from both sources in the period 1973-1988 except in the years 1975 and 1976 when it was overtaken by Salm. Wien. Since 1983 Salm. Enteritidis has been among the top ten isolates from animals, and ranked first in the list of isolates from humans in 1988 and from non human sources in 1991. During the last years the number of multidrug-resistant strains, mostly belonging to phage types 104 and 193 of Salm. Typhimurium has been rising. Salmonella strains have also been isolated from numerous extraintestinal infections, almost exclusively caused by Salm. Enteritidis and Typhimurium.

Salmonella enterica serovar typhimurium (STM) con resistenza multipla agli antibiotici appartenente al fagotipo (DT) 104 è un patogeno che si è diffuso rapidamente in tutto il mondo a partire dagli anni 80. Nell'ambito del progetto di sorveglianza delle salmonellosi Enter-net Italia, gli stipiti di STM isolati dai laboratori della rete vengono inviati a campione all'Istituto Superiore di Sanità per essere caratterizzati attraverso fagotipizzazione, profilo di antibiotico resistenza e analisi molecolare mediante elettroforesi in campo pulsato (PFGE). Durante il mese di Giugno 2004, 63 ceppi di STM, sono risultati DT104A, un sottotipo di DT104 piuttosto raro, mai osservato tra i ceppi pervenuti nel corso degli ultimi tre anni. Tutti i ceppi risultavano sensibili al pannello di antibiotici previsti dal protocollo Enter-net e mostravano lo stesso profilo elettroforetico in PFGE. Tutti i ceppi, eccetto 2 provenienti dall'ospedale di Spoleto, erano stati isolati da casi di gastroenterite, apparentemente non correlati tra loro, verificatisi a Roma e provincia a partire dalla fine di marzo 2004 e per la maggior parte concentrati nel mese di Aprile. Al fine di identificare il veicolo di trasmissione delle infezioni nell'area di Roma è stato condotto uno studio caso-controllo. Per ogni caso (soggetto con coprocoltura positiva per STM DT 104A) sono stati selezionati fino a 4 controlli appaiati per età e area di residenza. L'analisi statistica è stata effettuata applicando la regressione logistica condizionata realizzata con il software EpiInfo, ver.3.2. Lo studio analitico che ha incluso 26 casi e 63 controlli ha mostrato che l'acquisizione dell'infezione è associata in modo statisticamente significativo (OR=5,9; 95% C.I.: 1,6 -22,1) al consumo di un salume tipico del periodo pasquale ("corallina"). Questo lavoro mostra ancora una volta l'importanza della sorveglianza di laboratorio e la subtipizzazione dei ceppi batterici isolati nel riconoscimento di episodi epidemici.