Detection of novel gyrA mutations in nalidixic acid-resistant isolates of Salmonella enterica from patients with diarrhoea.

The aim of the current study was to detect mutations in the gyrA gene of quinolone-resistant Salmonella spp. isolates recovered in Tehran, Iran. Between April 2008 and September 2009, 174 Salmonella spp.

Prevalence of putative virulence markers in Campylobacter jejuni and Campylobacter coli isolated from hospitalized children, raw chicken, and raw beef in Tehran, Iran.

The incidence of the virulence-associated genes cdtA, cdtB, cdtC, cadF, dnaJ, racR, and pldA has been investigated in Campylobacter jejuni and Campylobacter coli collected from raw chicken and beef from retailers in Tehran, Iran, and from hospitalized children (age, ≤14 years) suffering from diarrhea. Campylobacter spp. were collectively identified by morphological and biochemical methods.

Emergence of extended-spectrum beta-lactamases in clinical isolates of Salmonella enterica in Tehran, Iran.

The purpose of the current study was to investigate the presence and molecular type(s) of extended-spectrum beta-lactamases (ESBLs) in Salmonella spp. isolates obtained from patients with diarrhea in hospitals of Tehran, Iran. Over a period of 17 months, 129 Salmonella spp.

Class A carbapenemases.

Carbapenems, such as imipenem and meropenem, are most often used to treat infections caused by enterobacteria that produce extended-spectrum beta-lactamases, and the emergence of enzymes capable of inactivating carbapenems would therefore limit the options for treatment. Carbapenem resistance in Enterobacteriaceae is rare, but class A beta-lactamases with activity against the carbapenems are becoming more prevalent within this bacterial family. The class A carbapenemases can phylogenetically be segregated into six different groups of which four groups are formed by members of the GES, KPC, SME, IMI/NMC-A enzymes, while SHV-38 and SFC-1 each separately constitute a group.

Extended-spectrum beta-lactamases in Taiwan: epidemiology, detection, treatment and infection control.

Extended-spectrum beta-lactamases (ESBLs) efficiently hydrolyze extended-spectrum beta-lactams such as cefotaxime, ceftriaxone, ceftazidime, and aztreonam. ESBLs are most often plasmid-mediated. In Taiwan, the prevalence of ESBLs in bacteria has risen, ranging from 8.

OXA-type carbapenemases.

In recent years, the number of class D beta-lactamases with carbapenem-hydrolysing properties has increased substantially. Based on amino acid sequence identities, these class D or OXA-type carbapenemases are divided into eight distantly related groups, and they are only remotely related to other class D beta-lactamases. A putative ancestor to one of the plasmid-encoded OXA-type carbapenemases has been found.

Cefotaximases (CTX-M-ases), an expanding family of extended-spectrum beta-lactamases.

Among the extended-spectrum beta-lactamases, the cefotaximases (CTX-M-ases) constitute a rapidly growing cluster of enzymes that have disseminated geographically. The CTX-M-ases, which hydrolyze cefotaxime efficiently, are mostly encoded by transferable plasmids, and the enzymes have been found predominantly in Enterobacteriaceae, most prevalently in Escherichia coli, Salmonella typhimurium, Klebsiella pneumoniae, and Proteus mirabilis. Isolates of Vibrio cholerae, Acinetobacter baumannii, and Aeromonas hydrophila encoding CTX-M-ases have also been reported.

Plasmid-borne AmpC beta-lactamases.

Historically, it was thought that ampC genes encoding class C beta-lactamases were located solely on the chromosome but, within the last 12 years, an increasing number of ampC genes have been found on plasmids. These have mostly been acquired by ampC-deficient pathogenic bacteria, which consequently are supplied with new and additional resistance phenotypes. This review discusses the phylogenetic origin of the plasmid-encoded AmpC beta-lactamases, their occurrence, and mode of spread, as well as their hydrolytic properties.