Linearization of the Brevicidine and Laterocidine Lipopeptides Yields Analogues That Retain Full Antibacterial Activity.

Brevicidine and laterocidine are macrocyclic lipodepsipeptides with selective activity against Gram-negative bacteria, including colistin-resistant strains. Previously, the macrocyclic core of these peptides was thought essential for antibacterial activity. In this study, we show that C-terminal amidation of linear brevicidine and laterocidine scaffolds, and substitution of the native Thr9, yields linear analogues that retain the potent antibacterial activity and low hemolysis of the parent compounds. Furthermore, an alanine scan of both peptides revealed that the aromatic and basic amino acids within the common central scaffold are essential for antibacterial activity. This linearization strategy for modification of cyclic peptides is a highly effective way to reduce the time and cost of peptide synthesis and may be applicable to other non-ribosomal antibacterial peptides.

Synthesis and structure-activity relationship studies of N-terminal analogues of the lipopeptide antibiotics brevicidine and laterocidine.

The brevicidine and laterocidine family of lipopeptide antibiotics exhibit strong activity against multidrug-resistant Gram-negative bacteria, while showing low propensity to induce resistance. Both peptides feature a branched lipid tail on the N-terminal residue, which for brevicidine is chiral. Here, we report the synthesis and biological evaluation of a library of brevicidine and laterocidine analogues wherein the N-terminal lipid is replaced with linear achiral fatty acids. Optimal lipid chain lengths were determined and new analogues with strong activity against colistin-resistant E. coli produced.

Synthetic studies with the brevicidine and laterocidine lipopeptide antibiotics including analogues with enhanced properties and in vivo efficacy.

Brevicidine and laterocidine are two recently discovered lipopeptide antibiotics with promising antibacterial activity. Possessing a macrocyclic core, multiple positive charges, and a lipidated N-terminus, these lipopeptides exhibit potent and selective activity against Gram-negative pathogens, including polymyxin-resistant isolates. Given the low amounts of brevicidine and laterocidine accessible by fermentation of the producing microorganisms, synthetic routes to these lipopeptides present an attractive alternative. We here report the convenient solid-phase syntheses of both brevicidine and laterocidine and confirm their potent anti-Gram-negative activities. The synthetic routes developed also provide convenient access to novel structural analogues of both brevicidine and laterocidine that display improved hydrolytic stability while maintaining potent antibacterial activity in both in vitro assays and in vivo infection models.

An outbreak of Salmonella serotype Typhimurium infections with an unusually long incubation period.

A 1998 investigation of an outbreak of Salmonella serotype Typhimurium infections among children tasting unpasteurized milk during tours of a dairy farm demonstrated a distribution of unusually long incubation periods (median, 8 days; interquartile range [IQR], 6-14 days). Bacterial isolates were highly acid tolerant and contained genes associated with protection against destructive phagocytic reactive oxygen intermediates. We hypothesize that exposure to low-dose oral inoculum of a pathogen with these properties could have contributed to cases of non-typhoidal salmonellosis with the longest incubation period reported to the Centers for Disease Control and Prevention (CDC).

An outbreak of enterotoxigenic Escherichia coli associated with sushi restaurants in Nevada, 2004.

BACKGROUND: In August and November 2004, 2 clusters of diarrhea cases occurred among patrons of 2 affiliated sushi restaurants (sushi restaurant A and sushi restaurant B) in Nevada. In August 2004, a stool sample from 1 ill sushi restaurant A patron yielded enterotoxigenic Escherichia coli (ETEC). In December 2004, we investigated a third cluster of diarrhea cases among sushi restaurant B patrons. METHODS: We defined a case as diarrhea in a person who ate at sushi restaurant B from 3 December through 13 December 2004. Control subjects were individuals who dined with case patients but did not become ill. Duplex polymerase chain reaction was used to detect genes coding for heat-stable and heat-labile enterotoxins of ETEC. RESULTS: One-hundred thirty patrons of sushi restaurant B reported illness; we enrolled 36 case patients and 29 control subjects. The diarrhea-to-vomiting prevalence ratio among patients was 4.5. Illness was associated with consumption of butterfly shrimp (estimated odds ratio, 7.2; 95% confidence interval, 1.1 to infinity). The implicated food was distributed to many restaurants, but only sushi restaurant B patrons reported diarrhea. We observed poor food-handling and hand hygiene practices at sushi restaurant B. Stool samples from 6 of 7 ill patrons and 2 of 27 employees who denied illness yielded ETEC. CONCLUSIONS: ETEC was identified as the etiologic agent of a large foodborne outbreak at a sushi restaurant in Nevada. Poor food-handling practices and infected foodhandlers likely contributed to this outbreak. Although ETEC is a well-documented cause of domestic foodborne outbreaks, few laboratories can test for it. Earlier recognition of ETEC infections may prevent subsequent outbreaks from occurring.

Farm visits and undercooked hamburgers as major risk factors for sporadic Escherichia coli O157:H7 infection: data from a case-control study in 5 FoodNet sites.

In 1996, active surveillance in 5 Foodborne Diseases Active Surveillance Network (FoodNet) sites revealed up to a 9-fold difference in Escherichia coli O157:H7 (O157) infection incidence between sites. A matched case-control study of sporadic O157 cases was conducted in these sites from March 1996 through April 1997. Case subjects were patients with non-outbreak-related diarrheal illness who had O157 isolated from their stool samples. Control subjects were healthy persons matched by age and telephone number exchange. Overall, 196 case patients and 372 controls were enrolled. O157 infections were associated with farm exposure, cattle exposure, eating a pink hamburger (both at home and away from home), eating at a table-service restaurant, using immunosuppressive medication, and obtaining beef through a private slaughter arrangement. Variations in cattle exposures may explain a part of the regional variability of O157 infection incidence. O157 control measures should focus on reducing risks associated with eating undercooked hamburger, dining at table-service restaurants, and farm exposures.