Prevalence and antimicrobial resistance of non-typhoid Solmonella in military personnel,1988-2013

Objective:To describe the spanning 25 years data for the occurrence, magnitude, and trends regarding antimicrobial resistance of non-typhoidalSalmonella (NTS) isolated from non-immune travelers to Thailand participating in joint military operations.Methods:A total of 355 NTS isolates, obtained from 2052 fecal samples from US soldiers deployed for military maneuvers in Thailand during 1988-2013, were examined for NTS serogroup/serotypes and tested for antimicrobial susceptibility by disk diffusion to these 10 antibiotics:ampicillin, azithromycin (AZM), ciprofloxacin, colistin, gentamicin, kanamycin, nalidixic acid, streptomycin (STR), tetracycline (TET), and trimethoprim/sulfamethoxazole. Identified AZM-resistant NTS isolates were further evaluated for their minimal inhibitory concentration by the E-test method.Results:NTS infections accounted for 17.3％ (355/2052), including 11 serogroups and 50 different serotypes. The most prevalent serogroup wasSalmonella group C2-C3 (35.8％, 127/355) followed by groups B (21.1％, 75/355) and C1 (18.6％, 66/355). Identified serotypes includedSalmonellahadar (n=60),Salmonellarissen (n=45), andSalmonella blockley (n=34). Among the predominate serogroups, antimicrobial resistance was consistently high against TET (76.9％, 273/355) followed by STR (40.8％, 145/355). OneSalmonella senftenberg isolate demonstrated decreased ciprofloxacin susceptibility. Most isolates (94.6％) were resistant to one or more antimicrobials, and the most common multidrug resistance was TET-STR-nalidixic acid (11.5％, 41/355).Conclusions:The prevalence of NTS serotypes and the growing magnitude of antibiotic resistant bacteria isolated from deployed US military in Thailand are documented from 1988-2013. This study demonstrates the antibiotic resistance profiles, highlighting the effectiveness of AZM that is a first-line treatment for travelers to Southeast Asia. AZM-resistant NTS isolates are periodically observed over a 25-year period. Hence, the ongoing surveillance and prevalence efforts are required to monitor NTS resistant strains causing further treatment failure.

Prevalence and antimicrobial resistance of non-typhoid Solmonella in military personnel,1988-2013

Objective:To describe the spanning 25 years data for the occurrence,magnitude,and trends regarding antimicrobial resistance of non-typhoidal Salmonella(NTS)isolated from non-immune travelers to Thailand participating in joint military operations.Methods:A total of 355 NTS isolates,obtained from 2052 fecal samples from US soldiers deployed for military maneuvers in Thailand during 1988-2013,were examined for NTS serogroup/serotypes and tested for antimicrobial susceptibility by disk diffusion to these 10 antibiotics:ampicillin,azithromycin(AZM),ciprofloxacin,colistin,gentamicin,kanamycin,nalidixic acid,streptomycin(STR),tetracycline(TET),and trimethoprim/sulfamethoxazole.Identified AZM-resistant NTS isolates were further evaluated for their minimal inhibitory concentration by the E-test method.Results:NTS infections accounted for 17.3%(355/2052),including11 serogroups and 50 different serotypes.The most prevalent serogroup was Salmonella group C2-C3(35.8%,127/355)followed by groups B(21.1%,75/355)and C1(18.6%,66/355).Identified serotypes included Salmonella hadar(n=60),Salmonella rissen(n=45),and Salmonella blockley(n=34).Among the predominate serogroups,antimicrobial resistance was consistently high against TET(76.9%,273/355)followed by STR(40.8%,145/355).One Salmonella senftenberg isolate demonstrated decreased ciprofloxacin susceptibility.Most isolates(94.6%)were resistant to one or more antimicrobials,and the most common multidrug resistance was TET-STR-nalidixic acid(11.5%,41/355).Conclusions:The prevalence of NTS serotypes and the growing magnitude of antibiotic resistant bacteria isolated from deployed US military in Thailand are documented from 1988-2013.This study demonstrates the antibiotic resistance profiles,highlighting the effectiveness of AZM that is a first-line treatment for travelers to Southeast Asia.AZM-resistant NTS isolates are periodically observed over a 25-year period.Hence,the ongoing surveillance and prevalence efforts are required to monitor NTS resistant strains causing further treatment failure.

Efficiency of Plating Media and Enrichment Broths for Isolating <i>Salmonella</i>Species from Human Stool Samples: A Comparison Study

A comparative study was performed to evaluate best practice culture media and enrichment broths for recovering Salmonella species from human stool samples. A total of 1297 human stools were collected and processed in this study. Evaluation of agar media was carried out by direct plating (DP), 1096 stool samples were inoculated on Modified Semisolid Rappaport-Vassiliadis (MSRV), Xylose-Lysine-Deoxycolate (XLD), MacConkey (MAC), and Hektoen Enteric (HE) agars. Evaluation of enrichment broths were carried out by enrichment all 1297 stool samples in Selenite broth (SB), Rappaport-Vassiliadis (RV) broth, and Buffered Peptone Water (BPW), followed by plating on MSRV, MAC, and HE agars. A total of 102 Salmonella-positive stools by DP, 85.3% (87/102) were recovered utilizing MSRV while recovery from XLD, MAC, and HE agars were 34.3% (35/102), 34.3% (35/102), and 29.4% (30/102) respectively. A total 299/1297 stools samples were Salmonella-positive on at least one plating medium after enrichment procedure were 77.3% (177/299) for SB, 86.0% (197/299) and 78.6% (180/299) for RV and BPW respectively. All Salmonella isolated in this study was nontyphi Salmonella. Presently, the data suggest that the use of MSRV over MAC, HE, and XLD agars for isolation nontyphi Salmonella species from human stools is more efficacious. Additionally, use of MSRV in combination with MAC and HE agars following enrichment in RV broth enhances recovery of nontyphi Salmonella species. However, RV broth is inhibitory to typhi Salmonella, thus use of MSRV medium in combination with MAC, HE or XLD agars in direct plating following enrichment in non-selective BPW is an alternate method for recovery of both typhi and nontyphi Salmonella species contaminated in human stool samples.

Field Evaluation of a Transport Medium and Enrichment Broth for Isolation of Campylobacter Species from Human Diarrheal Stool Samples

Campylobacter continues to be a major cause of bacteriamediated diarrheal diseases, both for Thai citizens and travelers to Thailand. For field epidemiological studies, appropriate methods for storage, intralaboratory transport of patients specimens and use of enrichment culture to isolate this organism is critical. Study A, represents patient stool specimens collected in Bangkok and processed for Campylobacter culture within three hours after collection. Study B, represents stool specimens collected from patients in northeast and Southern regions of Thailand in modified CaryBlair transport medium. These specimens were transported and processed for Campylobacter in Bangkok at varying intervals ranging from 1 to 7 days. Of 900 diarrheal samples examined in study A, a total of 158 were Campylobacter positive through culture. Of these, 145 and 141 isolates were cultured by direct plating and enrichment plating respectively (P = 0.5839). From 1,168 diarrheal stool samples examined in study B, 184 were positive for Campylobacter. Direct and enrichment plating resulted in 139 and 168 culture isolates;respectively (P = 0.0003). Samples from study B delayed in processing for 1 to 3 days, resulted in 46 and 50 isolated by direct and enrichment plating;respectively (P = 0.4545). However, among samples delayed in processing for 4 to 7 days, a total of 128 Campylobacter isolates were cultured, having cultured 93 and 118 isolates through direct and enrichment plating;respectively (P = 0.0003). At present these studies demonstrate that enrichment culture has no benefit when stool specimen collection and immediate processing occur and when there is a processing delay period of 1 - 3 days. However, enrichment culture was beneficial in instances where transport and processing was delayed 4 - 7 days.