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Shigella spp. antimicrobial drug resistance, Papua New Guinea, 2000-2009.

To the Editor: Approximately half the Shigella spp. infections in developing countries are caused by endemic shigellae (1), which in these countries are responsible for [approximately equal to]10% of all episodes of diarrhea among children <5 years of age and up to 75% of deaths from diarrhea (2). Deaths from epidemic Shigella spp. in the community are estimated to outnumber deaths within the healthcare setting. In Papua New Guinea, diarrhea is a major cause of hospital admission and death (3); Shigella spp. are among the most common causes of enteric bacterial infection (4,5), and S. flexneri is the most common serotype (3,6). Outbreaks of bloody diarrhea are frequently reported; however, diagnosis in remote settings is challenging, partly because the storage requirements for the organism are difficult to meet.

Multidrug resistance of shigellae is not new (1); many countries have reported resistance to amoxicillin, cotrimoxazole, and chloramphenicol. For this reason, the World Health Organization recommends that all patients with bloody diarrhea be treated with either ciprofloxacin or 1 of the 3 second-line drugs: pivmecillinam, azithromycin, and ceftriaxone (7). The antimicrobial drug currently recommended for patients with bloody diarrhea in primary healthcare settings in Papua New Guinea is co-trimoxazole (8); ciprofloxacin is available only in hospitals.

In August 2009, an epidemic of multidrug-resistant S. flexneri infection associated with widespread illness and death across 4 provinces of Papua New Guinea was reported to health authorities. To understand the trends and to inform antimicrobial drug policy makers, we reviewed retrospective microbiological data for 2000-2009. With the exception of 3 isolates collected during an outbreak in the border regions of the 4 provinces during 2009 (excluded from analysis), all isolates in our study were obtained as part of routine surveillance. Fecal samples were collected by clinicians from any patient seeking care for severe diarrhea at Port Moresby General Hospital.

Before serologic testing was conducted, samples were spread directly on desoxycholate citrate agar and MacConkey agar plates for culture. Antimicrobial drug resistance testing was performed by using the Kirby-Bauer method.

From a total of 3,419 fecal samples cultured, 136 (4.0%) were positive for Shigella spp. The most commonly isolated species was S. flexneri (90.4%); less frequently isolated were S. boydii (3.7 %), S. dysenteriae (2.9%), and S. sonnei (1.5%). Of the 123 S. flexneri isolates, 20 (16%) were further characterized; the most frequent serovars were serovar 2 (40%) and serovar 3 (30%). Many (48%) Shigella spp.-positive isolates were from children <5 years of age. The highest rates of antimicrobial drug resistance of all Shigella spp. were to amoxicillin (96%), co-trimoxazole (86%), and chloramphenicol (60%); no resistance to ciprofloxacin and cephalexin was found (Table).

Current evidence supports the use of ciprofloxacin, ceftriaxone, and pivmecillinam for treatment of bloody diarrhea (9). It also suggests that dysentery rarely relapses if an infected child has received a full course of treatment with 1 of these drugs and the causative pathogen is sensitive to the drug. Reducing the risk for relapse of bacterial infections among children is beneficial because it reduces the likelihood of subsequent episodes of dysentery occurring in that child and of transmission to others (9). In our study, most isolates were resistant to co-trimoxazole and the other available antimicrobial drugs, indicating that their use would not have reduced illness and subsequent transmission in this setting. The lack of resistance to ciprofloxacin and cephalexin indicates that these drugs may be more effective; however, they are neither available at the primary healthcare level nor recommended in Papua New Guinea, which is cause for concern.

Surveillance for antimicrobial drug resistance is essential for the containment of antimicrobial drug resistance globally. However, international surveillance depends on strong national surveillance systems. Despite the existence of a network of subnational laboratories where fecal sample cultures had been performed, these laboratories no longer perform these cultures. In 1964, the laboratory in 1 provincial hospital analyzed and subtyped 1,000 stool samples over a 15-month period (6). In our study, conducted at the national referral hospital (which limits the representativeness), we analyzed 3,419 fecal samples over a 10-year period.

Outbreaks of bloody diarrhea are common in remote settings in Papua New Guinea, yet with the exception of the 3 isolates from 2009 that were excluded from analysis, no Shigella spp.-positive samples have been identified during outbreaks. Molecular methods may serve as an adjunct to traditional laboratory methods by improving sensitivity and also enabling diagnosis of Shigella spp. outbreaks among remote populations where specimen storage and transport requirements may be challenging (10).

We describe extremely high rates of resistance of Shigella spp. to cotrimoxazole, the recommended treatment for bloody diarrhea in Papua New Guinea. Strengthening national surveillance for antimicrobial drug resistance would provide the evidence to better inform policy decision makers. A review of the national antimicrobial drug policy for management of bloody diarrhea is urgently needed.


We thank Darrel Cecil, Temas Ikanofi, Leomeldo Latorre, and Luisa Wanma for their diagnostic support and Anthony Gomes and Eigil Sorensen for their technical support.

Alexander Rosewell, Berry Ropa, Enoch Posanai, Samir R. Dutta, Glen Mola, Anthony Zwi, and C. Raina MacIntyre

Author affiliations: World Health Organization, Port Moresby, Papua New Guinea (A. Rosewell); National Department of Health, Port Moresby (B. Ropa, E. Posanai); Port Moresby General Hospital, Port Moresby (S.R. Dutta); University of Papua New Guinea, Port Moresby (G. Mola); and University of New South Wales, Sydney, New South Wales, Australia (A. Rosewell, A. Zwi, C.R. MacIntyre)

DOI: 10.3201/eid1611.101025


(1.) Niyogi SK. Shigellosis. J Microbiol. 2005;43:133-43.

(2.) World Health Organization. Generic protocol to estimate the burden of Shigella diarrhoea and dysenteric mortality. 1999 May [cited 2010 Mar 10].

(3.) Vince JD. Diarrhoea in children in Papua New Guinea. P N G Med J. 1995;38:26271.

(4.) Miwatani T, Honda T, Higashitsutsumi M, Tanaka R, Sakaue Y, et al. Bacterial aetiology of infantile diarrhoea in Papua New Guinea. J Trop Pediatr. 1990;36:101-3.

(5.) Bukenya GB, Kaiser R, Nneka N. Rotavirus from children of an urban settlement of Papua New Guinea. J Trop Pediatr. 1990;36:66-8.

(6.) Curtis PG. The isolation, incidence and sensitivity of Shigella organisms. P N G Med J. 1964;7:23-6.

(7.) World Health Organization. Guidelines for the control of shigellosis, including epidemics due to Shigella dysenteriae type 1 [cited 2010 Mar 10].

(8.) Standard treatment for common illnesses of children in Papua New Guinea--a manual for nurses, community health workers, health extension officers and doctors. 8th ed. Port Moresby (Papua New Guinea): National Department of Health; 2005.

(9.) Christopher PR, David KV, John SM, Sankarapandian V. Antibiotic therapy for Shigella dysentery. Cochrane Database Syst Rev. 2010;1:CD006784.

(10.) Farfan MJ, Garay TA, Prado CA, Filliol I, Ulloa MT, Toro CS. A new multiplex PCR for differential identification of Shigella flexneri and Shigella sonnei and detection of Shigella virulence determinants. Epidemiol Infect. 2010 Apr;138:525-33. Epub 2009 Sep 18.

Address for correspondence: Alexander Rosewell, World Health Organization, 4th Floor AOPI Centre, PO Box 5896, Port Moresby, Papua New Guinea; email: rosewella@wpro.
Table. Antimicrobial drug resistance of Shigella
spp., Papua New Guinea, 2000-2009 *

                              Shigella sp., no. (%) isolates

                  Total no.
                  isolates                    S.          S.
Drug               tested     Sensitivity    boydi    dysenteriae

Amoxicillin          98            S           0        1 (33)
                                   R        3 (100)     2 (67)

Cephalexin           46            S        2 (67)      2 (100)
                                   I        1 (33)         0
                                   R           0           0

Ciprofloxacin        41            S        2 (67)        NA
                                   I        1 (33)        NA
                                   R           0           0

Chloramphenicol      114           S           0        2 (50)
                                   I           0        2 (50)
                                   R        4 (100)        0

Naladixic acid       13            S        1 (100)        0
                                   R           0        1 (100)

Co-trimoxazole       76            S        1 (25)      1 (33)
                                   R        3 (75)      2 (67)

                          Shigella sp., no. (%) isolates

                     S.        S.      Unknown
Drug              flexneri   sonneii     sp.       Total

Amoxicillin        2 (2)        0      1 (100)     4 (4)
                  87 (98)    2 (100)      0       94 (96)

Cephalexin        38 (100)   2 (100)   1 (100)    45 (98)
                     0          0         0        1 (2)
                    000                              0

Ciprofloxacin     35 (100)   1 (100)   2 (100)    40 (98)
                     0          0         0        1 (2)
                    000                              0

Chloramphenicol    9 (9)     2 (100)    1 (50)    14 (12)
                  28 (28)       0       1 (50)    31 (27)
                  64 (63)       0         0       68 (60)

Naladixic acid    8 (100)    1 (100)    1 (50)    11 (85)
                     0          0       1 (50)    2 (15)

Co-trimoxazole     9 (14)       0         0       11 (14)
                  57 (86)    2 (100)   1 (100)    65 (86)

* S, sensitive; R, resistant, I, intermediate; NA, not applicable.
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Title Annotation:LETTERS
Author:Rosewell, Alexander; Ropa, Berry; Posanai, Enoch; Dutta, Samir R.; Mola, Glen; Zwi, Anthony; MacInty
Publication:Emerging Infectious Diseases
Article Type:Letter to the editor
Geographic Code:8PAPU
Date:Nov 1, 2010
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