Dipstick Test for Rapid Diagnosis of Shigella dysenteriae 1 in Bacterial Cultures and Its Potential Use on Stool Samples

International audienceBACKGROUND: We describe a test for rapid detection of S. dysenteriae 1 in bacterial cultures and in stools, at the bedside of patients. METHODOLOGY/PRINCIPAL FINDINGS: The test is based on the detection of S. dysenteriae 1 lipopolysaccharide (LPS) using serotype 1-specific monoclonal antibodies coupled to gold particles and displayed on a one-step immunochromatographic dipstick. A concentration as low as 15 ng/ml of LPS was detected in distilled water and in reconstituted stools in 10 minutes. In distilled water and in reconstituted stools, an unequivocal positive reaction was obtained with 1.6×10⁶ CFU/ml and 4.9×10⁶ CFU/ml of S. dysenteriae 1, respectively. Optimal conditions to read the test have been determined to limit the risk of ambiguous results due to appearance of a faint yellow test band in some negative samples. The specificity was 100% when tested with a battery of Shigella and unrelated strains in culture. When tested on 328 clinical samples in India, Vietnam, Senegal and France by laboratory technicians and in Democratic Republic of Congo by a field technician, the specificity (312/316) was 98.7% (95% CI:96.6-99.6%) and the sensitivity (11/12) was 91.7% (95% CI:59.8-99.6%). Stool cultures and the immunochromatographic test showed concordant results in 98.4 % of cases (323/328) in comparative studies. Positive and negative predictive values were 73.3% (95% CI:44.8-91.1%) and 99.7% (95% CI:98-100%). CONCLUSION: The initial findings presented here for a simple dipstick-based test to diagnose S. dysenteriae 1 demonstrates its promising potential to become a powerful tool for case management and epidemiological surveys

Clonal Diversity among Streptogramin A-Resistant Staphylococcus aureus Isolates Collected in French Hospitals

We analyzed 62 clinical isolates of streptogramin A-resistant (SGA(r)) Staphylococcus aureus collected between 1981 and 2001 in 14 hospitals located in seven French cities. These isolates, including five with decreased susceptibility to glycopeptides, were distributed into 45 antibiotypes and 38 SmaI genotypes. Each of these genotypes included between 1 and 11 isolates, the SmaI patterns of which differed by no more than three bands. Although numerous clones were identified, we observed the spread of monoclonal isolates either within the same hospital or within hospitals in distinct cities and at large time intervals. Hybridization with probes directed against 10 SGA(r) genes (vatA, vatB, vatC, vatD, vatE, vgaA, vgaB, vgaAv, vgbA, and vgbB) revealed six patterns: vgaAv (21 isolates), vatA-vgbA (24 isolates), vgaAv-vatB-vgaB (14 isolates), vgaAv-vatA-vgbA (1 isolate), vgaAv-vatA-vgbA-vatB-vgaB (1 isolate), and vgaA (1 isolate). We detected at least one SGA(r) determinant in all of the tested isolates. vgaAv, which is part of the recently characterized transposon Tn5406, was found in 59.7% of the tested isolates. Of the 16 streptogramin B-susceptible isolates, 14 carried vgaAv alone and were susceptible to the mixtures of streptogramins, whereas the 2 isolates carrying vgaAv-vatB-vgaB were resistant to these mixtures. vatA-vgbA was found on plasmids of the same apparent size in 26 (42%) of the tested clinical isolates from 18 unrelated SmaI genotypes. The possible dissemination of some of the multiple clones characterized in the present study with an expected increased selective pressure of streptogramins following the recent licensing of Synercid (quinupristin-dalfopristin) must be carefully monitored

Arthrobacter bergerei sp. nov. and Arthrobacter arilaitensis sp. nov., novel coryneform species isolated from the surfaces of cheeses

International audienceFourteen isolates of two different bacterial species isolated from the surface of smear-ripened cheeses were found to exhibit many characteristics of the genus Arthrobacter. The isolates were aerobic, Gram-positive, catalase-positive, non-spore-forming and non-motile. The cell-wall peptidoglycan contained lysine, alanine and glutamic acid. rrs sequence analysis indicated that the new isolates Re117T and Ca106T are closely related to the Arthrobacter nicotianae group and showed highest sequence similarity (>98 %) to Arthrobacter nicotianae and Arthrobacter protophormiae. However, DNA–DNA hybridization studies indicated that the strains represented two novel genomic species within the genus Arthrobacter and did not belong to A. nicotianae or A. protophormiae (<43 % DNA–DNA relatedness). On the basis of the phylogenetic and phenotypic distinctiveness of the new isolates, these bacteria should be classified as two novel Arthrobacter species, for which the names Arthrobacter bergerei sp. nov. and Arthrobacter arilaitensis sp. nov. are proposed. Type strains have been deposited in culture collections as Arthrobacter bergerei Ca106T (=CIP 108036T=DSM 16367T) and Arthrobacter arilaitensis Re117T (=CIP 108037T=DSM 16368T)

Predictive values (PV) for <i>Shigella dysenteriae</i> 1 diagnosis.

<p>Positive PV is represented by the red line and negative PV by the blue line.</p

Two dispsticks showing typical negative (A) and positive (B) results after being kept for 10 minutes in bacterial cultures ⁽¹⁾, watery or dysenteric stool samples.

<p>¹ The specificity was assessed using pure cultures of the following bacterial strains: <i>S. flexneri</i> serotypes 1a (strain 082429), 1b (strain 085052), 2a (strain 083766), 2b (strain 082831), 3a (strain 084963), 3b (strain 083638), 4 (strain 075519), 4c (strain 08 3649), 6 var Herforshire (strain 083400), 6 var Manchester (strain 080654), Y (strain 075876) and X (strain 08 3347); <i>S. dysenteriae</i> serotypes 2 (strain 083092), 3 (strain 081718), 4 (strain 083171), 5 (strain 071059), 6 (strain 087336), 11 (strain 9410434), 12 (strain 080360), 13 (strain 056376) and untypable strain 97–10607, a panel of six wild <i>S. dysenteriae</i> 1 strains from Central Africa <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0024830#pone.0024830-Germani1" target="_blank">[38]</a> and five <i>S. dysenteriae</i> 1 wild strains from Centre National de Reference des Shigelles at Paris (strains 057331, 100771, 97171, 061306, 061305); <i>S. boydii</i> serotypes 1 (strain 07 7695), 2 (strain 08 3129), 3 (strain 07 8186), 4 (strain 08 3330), 5 (strain 599379), 6 (strain 346756), 8 (strain 06 6360), 9 (strain 0541), 10 (strain 081707), 11 (strain 065905), 12 (strain 06 8162), 13 (strain 161055), 14 (strain 08 0226), 15 (strain 04 8291), 17 (strain E3615 53), 18 (strain 078115), 19 (strain 07 5636), 20 (strain 08 2360); <i>S. sonnei</i> strain 08 7832 (phase 1) and strain 08 7785 (phase 2); <i>Salmonella enterica typhimurium</i> (strains 06-2835, 06-2846, 06-2847), <i>S enteritidis</i> (strains 06-2841, 06-2844, 06-2851, 06-2852), <i>S. hadar</i> (strains 06-2533), <i>S. brandenburg</i> (strain 06-2619), <i>S. heidelberg</i> (06-2843), <i>S. oranienburg</i> (strain 06-2634), <i>S. risen</i> (strain 06-2615), <i>S. stanleyville</i> (strain 06-2832), <i>S. typhi</i> (strain 06-2829), <i>S. paratyphi</i> A (strain 06-2633), <i>S. paratyphi</i> B (strain 06-2696), <i>S. meleagridis</i> (strain 06-2850), <i>S. stubra</i> (strain 06-2384), <i>S. huittingfoss</i> (strain 06-2391), enteroagregative <i>Escherichia coli</i> (strains 55989, JM221, O42, 56390 and 384P), diffusely adherent <i>E. coli</i> (strain AL851, AL847, C1845, AL855 and 3043), enterotoxigenic <i>E. coli</i> (strains EDL1496, 440TL, Tx-1, E2539-C1, 469), enteropathogenic <i>E. coli</i> (strains 135/12 (O55:H-), E6468/62 (O86:H34), 11201 (O125:H6), KK111/1 and F88/6848-2 both O26:H11), <i>E. coli</i> O148 (ref CNR E519-66), <i>Vibrio cholerae</i> O1 (strains CNRVC960255, 970002, 970014, 970025, 970067, 960325, 970022, 970053, 970055, 970056), <i>V cholerae</i> O139 (strains CNRVC 930008, 930381, 930210, 930190), <i>V. cholerae</i> non O1 and non O139 (strains CNRVC 930177, 930429, 950689, 950691, 970037, 950769, 910388, 930121, 930297, 930391), <i>V. alginolyticus</i> (strain CIP103336), <i>V. fluvialis</i> (strains CIP103355, CNRVC356), <i>V. parahaemolyticus</i> (strains CIP75.2, CNRVC-030478, CNRVC030479, CNRVC000204, CNRVC000208), <i>V. furnissii</i> (strain CIP102972), <i>V. hollisae</i> (strain CIP104354), <i>V. mimicus</i> (strain 101888), <i>Aeromonas caviae</i> (strain CIP76.16), <i>A. enteropelogenes</i> (strain CIP104434), <i>A. hydrophila</i> (strain CIP76.15), <i>A. sobria</i> (strain CIP74.33), <i>Plesiomonas shigelloides</i> (strain CIP63.5), <i>Campylobacter jejuni</i>, <i>Yersinia enterocolitica</i> 1A (6 strains of biotype 1A, 2 strains of biotype 2, 2 strains of biotype 3, and 2 strains of biotype I). Three rough wild <i>S. dysenteriae</i> 1 (strains 01587, 061305, 061306) were also tested.</p

Clinical characteristics of patients from India (Chandigarh).

<p>Clinical characteristics of patients from India (Chandigarh).</p