Multidrug-Resistant Salmonella enterica Subspecies I Serovar 4,[5],12:i:- Isolates Recovered from Food Safety and Inspection Service-Regulated Products and Food Animal Ceca, 2007-2016.

Salmonella enterica subspecies I serovar 4,[5],12:i:- (Salmonella I 4,[5],12:i:-) is among the five most common serovars associated with human salmonellosis in the United States. In 2010, human infections with Salmonella I 4,[5],12:i:- which exhibited resistance to ampicillin, streptomycin, sulfonamides, and tetracycline (ASSuT) emerged as a public health concern. Outbreak investigations identified live animal settings, meat and poultry, and pets as confirmed and suspect sources of infection. To shed further light on possible sources of ASSuT-resistant Salmonella I 4,[5],12:i:- infections, we described isolates recovered from meat and poultry products regulated by the Food Safety and Inspection Service (FSIS) and from food animal ceca collected at FSIS-regulated slaughter establishments during 2007-2016. During the time period of interest, ASSuT-resistant Salmonella I 4,[5],12:i:- was found at low levels in multiple FSIS product classes including swine, turkey, cattle and chicken, which suggests this pathogen has a relatively wide host range. Monitoring trends in the various FSIS production classes over time and developing commodity profiles may help focus preventative strategies.

Novel linezolid resistance plasmids in Enterococcus from food animals in the USA.

Objectives: To sequence the genomes and determine the genetic mechanisms for linezolid resistance identified in three strains of Enterococcus isolated from cattle and swine caecal contents as part of the US National Antimicrobial Resistance Monitoring System (NARMS) surveillance programme. Methods: Broth microdilution was used for in vitro antimicrobial susceptibility testing to assess linezolid resistance. Resistance mechanisms and plasmid types were identified from data generated by WGS on Illumina® and PacBio® platforms. Conjugation experiments were performed to determine whether identified mechanisms were transmissible. Results: Linezolid resistance plasmids containing optrA were identified in two Enterococcus faecalis isolates and one Enterococcus faecium. The E. faecium isolate also carried the linezolid resistance gene cfr on the same plasmid as optrA. The linezolid resistance plasmids had various combinations of additional resistance genes conferring resistance to phenicols (fexA), aminoglycosides [spc and aph(3')-III] and macrolides [erm(A) and erm(B)]. One of the plasmids was confirmed to be transmissible by conjugation, resulting in linezolid resistance in the transconjugant. Conclusions: To the best of our knowledge, this is the first identification of linezolid resistance in the USA in bacteria isolated from food animals. The oxazolidinone class of antibiotics is not used in food animals in the USA, but the genes responsible for resistance were identified on plasmids with other resistance markers, indicating that there may be co-selection for these plasmids due to the use of different antimicrobials. The transmissibility of one of the plasmids demonstrated the potential for linezolid resistance to spread horizontally. Additional surveillance is necessary to determine whether similar plasmids are present in human strains of Enterococcus.

Increased recognition of non-O157 Shiga toxin-producing Escherichia coli infections in the United States during 2000-2010: epidemiologic features and comparison with E. coli O157 infections.

BACKGROUND: Shiga toxin-producing Escherichia coli (STEC) are an important cause of diarrhea and the major cause of postdiarrheal hemolytic uremic syndrome. Non-O157 STEC infections are being recognized with greater frequency because of changing laboratory practices. METHODS: Foodborne Diseases Active Surveillance Network (FoodNet) site staff conducted active, population-based surveillance for laboratory-confirmed STEC infections. We assessed frequency and incidence of STEC infections by serogroup and examined and compared demographic factors, clinical characteristics, and frequency of international travel among patients. RESULTS: During 2000-2010, FoodNet sites reported 2006 cases of non-O157 STEC infection and 5688 cases of O157 STEC infections. The number of reported non-O157 STEC infections increased from an incidence of 0.12 per 100,000 population in 2000 to 0.95 per 100,000 in 2010; while the rate of O157 STEC infections decreased from 2.17 to 0.95 per 100,000. Among non-O157 STEC, six serogroups were most commonly reported: O26 (26%), O103 (22%), O111 (19%), O121 (6%), O45 (5%), and O145 (4%). Non-O157 STEC infections were more common among Hispanics, and infections were less severe than those caused by O157 STEC, but this varied by serogroup. Fewer non-O157 STEC infections were associated with outbreaks (7% versus 20% for O157), while more were associated with international travel (14% versus 3% for O157). CONCLUSIONS: Improved understanding of the epidemiologic features of non-O157 STEC infections can inform food safety and other prevention efforts. To detect both O157 and non-O157 STEC infections, clinical laboratories should routinely and simultaneously test all stool specimens submitted for diagnosis of acute community-acquired diarrhea for O157 STEC and for Shiga toxin and ensure that isolates are sent to a public health laboratory for serotyping and subtyping.

Salmonella enterica serotype Enteritidis: increasing incidence of domestically acquired infections.

BACKGROUND: Salmonella enterica causes an estimated 1 million cases of domestically acquired foodborne illness in humans annually in the United States; Enteritidis (SE) is the most common serotype. Public health authorities, regulatory agencies, food producers, and food processors need accurate information about rates and changes in SE infection to implement and evaluate evidence-based control policies and practices. METHODS: We analyzed the incidence of human SE infection during 1996-2009 in the Foodborne Diseases Active Surveillance Network (FoodNet), an active, population-based surveillance system for laboratory-confirmed infections. We compared FoodNet incidence with passively collected data from complementary surveillance systems and with rates of SE isolation from processed chickens and egg products; shell eggs are not routinely tested. We also compared molecular subtyping patterns of SE isolated from humans and chickens. RESULTS: Since the period 1996-1999, the incidence of human SE infection in FoodNet has increased by 44%. This change is mirrored in passive national surveillance data. The greatest relative increases were in young children, older adults, and FoodNet sites in the southern United States. The proportion of patients with SE infection who reported recent international travel has decreased in recent years, whereas the proportion of chickens from which SE was isolated has increased. Similar molecular subtypes of SE are commonly isolated from humans and chickens. CONCLUSIONS: Most SE infections in the United States are acquired from domestic sources, and the problem is growing. Chicken and eggs are likely major sources of SE. Continued close attention to surveillance data is needed to monitor the impact of recent regulatory control measures.

Salmonella Enteritidis in meat, poultry, and pasteurized egg products regulated by the U.S. Food Safety and Inspection Service, 1998 through 2003.

The U.S. Food Safety and Inspection Service (FSIS) tests for Salmonella in meat, poultry, and egg products through three regulatory testing programs: the Pathogen Reduction-Hazard Analysis and Critical Control Point (PR-HACCP) program, the ready-to-eat program for meat and poultry products, and the pasteurized egg products program. From 1998 through 2003, 293,938 samples collected for these testing programs were analyzed for the presence of Salmonella enterica serotypes. Of these samples, 12,699 (4.3%) were positive for Salmonella, and 167 (1.3%) of the positive samples (0.06% of all samples) contained Salmonella Enteritidis. The highest incidence of Salmonella Enteritidis was observed in ground chicken PR-HACCP samples (8 of 1,722 samples, 0.46%), and the lowest was found in steer-heifer PR-HACCP samples (0 of 12,835 samples). Salmonella Enteritidis isolates were characterized by phage type, pulsed-field gel electrophoretic pattern, and antimicrobial susceptibility. Phage typing of 94 Salmonella Enteritidis isolates identified PT13 (39 isolates) and PT8 (36 isolates) as the most common types. One isolate from a ready-to-eat ham product was characterized as PT4. Electrophoretic analysis of 148 Salmonella Enteritidis isolates indicated genetic diversity among the isolates, with 28 unique XbaI electrophoretic patterns identified. Of these 148 isolates, 136 (92%) were susceptible to each of 16 antimicrobials tested. Two isolates were resistant to ampicillin alone, and 10 isolates were resistant to two or more antimicrobials. Isolation of Salmonella Enteritidis from FSIS-regulated products emphasizes the need for continued consumer education on proper food handling and cooking practices and continued work to decrease the prevalence of Salmonella in meat, poultry, and pasteurized egg products.

Environmental Survey by Manure Drag Sampling for Salmonella enteritidis in Chicken Layer Houses.

The Salmonella enteritidis Pilot Project (SEPP) was started in April 1992 as a cooperative effort between federal and state agencies, university laboratories, and the poultry industry in Pennsylvania to identify on-farm management practices which would reduce the S. enteritidis threat to public health. The SEPP evolved into the Pennsylvania Egg Quality Assurance Program (PEQAP) in 1994. This program uses many production practices and testing protocols outlined in the SEPP. A survey was conducted in 1995 to help evaluate the effectiveness of the program in reducing the prevalence of S. enteritidis in layer flocks. Forty-seven egg laying houses that had been in the SEPP since 1992 were evaluated in 1995 for the presence of S. enteritidis in the environment. Six of 47 houses (13%) were found positive for S. enteritidis on the basis of data collected by manure drag sampling, whereas in 1992 18 of the 47 houses (38%) had been positive for S. enteritidis . The percentage of S. enteritidis -positive samples declined from 21% in 1992 to 3.2% in 1995. This survey provides some evidence that the on-farm risk-reduction management practices identified in the SEPP and subsequently incorporated into the PEQAP have reduced S. enteritidis infections in Pennsylvania flocks.