Multiple antibiotic resistance among salmonellae in India

Salmonella Alachua: causative agent of a foodborne disease outbreak

Objectives

The aim of this study is to report the occurrence of the first outbreak of food poisoning caused by Salmonella Alachua in Brazil, as well as the antimicrobial susceptibility and the genetic relatedness of Salmonella Alachua strains isolated from clinical and food samples.

Material and methods

To elucidate the outbreak, an epidemiological investigation was carried out, and two samples of common food were tested – mayonnaise salad and galinhada (a traditional Brazilian dish of chicken and rice) – according to the Compendium of methods for the microbiological examination of foods. Five stool samples were tested employing classic methods for the isolation and identification of enterobacteria. Strains of Salmonella were characterized for antibiotic susceptibility according to the Clinical and Laboratory Standards Institute guidelines (2013), and submitted to pulsed-field gel electrophoresis analysis, performed according to the Centers for Disease Control and Prevention PulseNet protocol.

Results

A total of 94 people were interviewed after ingesting the food, 66 of whom had become ill. A 60-year old female patient who was hospitalized in a serious condition, developed septic shock and died two days after consuming the food. The presence of Salmonella Alachua was confirmed in all the analyzed stool samples, and in the two types of food. The five strains showed higher than minimum inhibitory concentration values of nalidixic acid (≥256 μg/mL) and reduced ciprofloxacin susceptibility (minimum inhibitory concentration = 0.5 μg/mL). The pulsed-field gel electrophoresis analysis revealed indistinguishable patterns in Salmonella Alachua strains isolated from clinical and food samples.

Conclusion

The data presented herein confirm the foodborne disease outbreak. They also allowed for the identification of the source of infection, and suggest that products from poultry are potential reservoirs for this serotype, reinforcing the importance of warning consumers about the danger of possible contamination.

Changes in antimicrobial resistance among Salmonella enterica Serovar typhimurium isolates from humans and cattle in the Northwestern United States, 1982-1997

We compared antimicrobial resistance patterns of Salmonella enterica serovar Typhimurium (ST) of isolates from humans (n = 715) and cattle (n = 378) in the Pacific Northwest from 1982 through 1997. The major changes in antimicrobial resistance can be attributed to the widespread clonal dissemination of multidrug-resistant definitive phage type 104 ST.

Antimicrobial drug resistance and resistance factor transfer among clinical isolates of salmonellae in Iran

508 salmonella strains isolated during 1983-1986 in Tehran, Iran from cases of diarrhoea in children less than 5 were tested for sensitivity to 10 antimicrobial drugs and their ability to transfer the resistance determinants. Salmonella typhimurium and S. havana were most common (45.7% and 30.9%, respectively) followed by S. typhi (2.9%) and S. larochelle (2.4%). The antimicrobial agents used were chloramphenicol (C), gentamicin (G), tetracycline (T), ampicillin (A), cephalothin (Cf), trimethoprim-sulfamethoxazole (SXT), kanamycin (K), nalidixic acid (Na), streptomycin (S), and furoxone (F). 91% of the salmonellae isolates contained resistance determinants, of which 89.6% were resistant to more than one agent. Strains resistant to 4-7 drugs comprised 85.6% of the total isolates. Ampicillin resistance was found in 85.4% and nalidixic acid in 2.7%. 58 different patterns of resistance to the antimicrobial agents used were observed, of which C/T/A/SXT/K/S and C/T/A/SXT/K/S/Cf were the most frequently encountered. 71.9% of the resistant strains contained transferable resistance factors and S. typhimurium had the highest rate of transfer (80.8%). Resistance to chloramphenicol had the highest rate of transfer among the agents used (77.4%) and streptomycin the lowest (20.0%). The pattern most frequently transferred was C/T/A/SXT/K (41.9%).

Genetic and molecular characterization of an epidemic plasmid coding for multidrug resistance in Salmonella typhimurium of human origin

All 201 multidrug resistant Salmonella typhimurium strains isolated from epidemics in India contained nonconjugative (157 strains) or conjugative (44 strains) Inc F1me multiresistance plasmids. Two small R-plasmids of 7 MDa which coded for resistance to either ampicillin or streptomycin and sulfamethoxazole were also detected along with other plasmids. The small plasmids were members of group 1 and group 2 incompatibility groups. Restriction endonuclease analysis of conjugative (96 MDa) and nonconjugative (88 MDa) Inc F1me plasmids showed considerable similarity except for the presence of unique fragments among both the groups and the loss of fragments corresponding to the smaller size of the nonconjugative plasmid. A single Inc F1me plasmid appears responsible for various outbreaks of multiresistant S. typhimurium in different parts of India.

Incidence of plasmids in multiply-resistant Salmonella isolates from diarrhoeal patients in Hong Kong from 1973-82

Plasmids present in multiply-resistant salmonella strains including Salmonella typhimurium, S. johannesburg, S. wandsworth, S. derby, S. newport, S. london and S. choleraesuis causing diarrhoea in patients in Queen Mary Hospital in Hong Kong from 1973-82 were studied. In multiply-resistant S. typhimurium, plasmids belonging to groups FIme, H1 or H2 and plasmids encoding trimethoprim-resistance which were compatible with standard plasmids of testable incompatibility groups were detected. In S. johannesburg, both the ASTCKSu- and ASCKSu-resistant strains which were predominant in two consecutive periods of an outbreak were found to harbour the same plasmid which belonged to the incompatibility group FIme. S. wandsworth strains isolated from a hospital outbreak in 1980 harboured an identical R-plasmid belonging to group N. A few strains of the other salmonellae showing resistance to multiple antibiotics were found to harbour R-plasmids belonging to groups H1, H2 and FIme. The only salmonella of the enteric fever group resistant to ampicillin, chloramphenicol and trimethoprim was an S. paratyphi B strain. The resistances were encoded on a plasmid of an unknown incompatibility group. The occurrence and distribution of plasmids in these salmonellae isolated within the 10-year period are discussed.

Does chloramphenicol remain the drug of choice for typhoid?

Of 2356 strains of Salmonella typhi isolated in Britain in the 8-year period 1978-85, 2345 (99.53%) were sensitive to all antibiotics tested and 11 (0.47%) were chloramphenicol-resistant; chloramphenicol resistance was plasmid-mediated in 6 strains. It is concluded that chloramphenicol remains a satisfactory first-line choice of drug for typhoid fever in Britain.

Antimicrobial resistance and incompatibility groups of R plasmids in Salmonella typhimurium isolated from human sources in Bombay from 1978 to 1980

Salmonella typhimurium isolated in Bombay from fecal samples of 145 patients suffering from gastroenteritis (group 1) and from the cerebrospinal fluid, feces, or blood of 42 patients with systemic salmonellosis (group 2) were examined for the antimicrobial resistance and incompatibility groups of their R plasmids. Multiple drug resistance was encountered in 88.9% of the isolates from group 1 and in all the isolates from group 2. The resistance found was mainly against ampicillin, chloramphenicol, kanamycin, streptomycin, sulfonamides, and tetracycline. In addition to these resistances, a number of isolates were also resistant to sulfamethoxazole-trimethoprim and gentamicin. The overall isolation frequency of strains resistant to these last drugs was significantly higher in group 2. The drug resistance in 95.3% of the isolates from group 1 and in all the isolates from group 2 was plasmid mediated. Incompatibility grouping of the R plasmids and phage typing of the isolates indicated that a clone of S. typhimurium with phage type pattern 66/122/untypable carrying Tra- IncF1me, Tra- Inc1, and Tra- Inc2 plasmids was most prevalent in Bombay from 1978 to 1980, and examples of this clone, especially those resistant to sulfamethoxazole-trimethoprim and gentamicin, were most often responsible for severe septicemic infection. A majority of the remaining S. typhimurium isolates were untypable and harbored plasmids of groups IncC, IncF1me, IncFII, IncH1, IncH2, IncI1 and IncI2; these isolates were rarely associated with systemic infection.

In vitro susceptibility of Salmonella to various antimicrobial agents, including a new cephalosporin, Ro 13-9904

The in vitro susceptibility of 363 strains of Salmonella isolated in Honk Kong to various antimicrobial drugs was tested, and the minimum inhibitory concentrations of ampicillin, mecillinam, and six cephalosporins (cephalexin, cephradine, cefamandole, cefoxitin, cefuroxime, and Ro 13-9904) for these strains were determined by an agar dilution method. Although strains of the typhoid and paratyphoid group remained susceptible to most antibiotics tested, many strains of the gastroenteric group of salmonellae were found to be resistant to multiple antibiotics, including ampicillin, chloramphenicol, and, occasionally, trimethoprim. Mecillinam and cefamandole, although active against most of the Salmonella strains tested, were shown to be less active against ampicillin-resistant strains. By contrast, Ro 13-9904 exhibited remarkably uniform and high activity against all the Salmonella strains tested, irrespective of their ampicillin resistance.