Melioidosis is the name given to all diseases caused by the bacterium Pseudomonas pseudomallei. Melioidosis is a tropical disease and prevails in parts of Southeast Asia, northern Australia, and Central and South America. However, in recent years, cases of melioidosis have been reported in the United States and other areas. The organism can infect any organ system, although the lung is the most common organ affected. Pulmonary melioidosis presents either as an acute fulminant pneumonia or as an indolent cavitary disease. In northeastern Thailand, the incidence of P pseudomallei infection is extremely high with significant mortality. One of the key problems with treating melioidosis is its recalcitrance to therapy and high relapse rate. In addition, this Gram-negative rod is resistant to aminoglycosides. In nonendemic regions, patients with melioidosis more typically present with reactivation disease occurring months to years after initial exposure to the organism. The pulmonary disease is mainly in the apices and resembles tuberculosis. With the increasing mobility of people throughout the world and the influx of immigrants from endemic to nonendemic areas, it is important that clinicians be aware of this disease. This article will review the epidemiology, clinical presentations, diagnosis, and treatment of pulmonary melioidosis.

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Ninety-one ampicillin-resistant Shigella flexneri strains from Hong Kong and Shanghai were studied for production of ␤-lactamases. TEM-1-like and OXA-1-like enzymes were identified in 21 and 79% of the strains, respectively, by isoelectric focusing (IEF). No difference in the pattern of ␤-lactamase production was found between strains from Hong Kong and Shanghai. Four ribotypes were detected. Over 88% of OXA-producing strains had the same ribotype. All TEM-1-like strains harbored a plasmid which hybridized positively with the bla TEM probe. Total DNA from OXA-1-like strains failed to hybridize or only hybridized weakly with an OXA probe. The OXA resistance was not transferable. OXA-1-like enzymes exhibited substrate and inhibition profiles similar to that of OXA-1 and were shown to have a pI of 7.3 by further IEF using a narrow-range ampholine gel. The gene encoding the OXA-1-like enzyme from one isolate (CH-07) was cloned, sequenced, and found to differ from bla OXA-1 at codon 131 (AGA3GGA; Arg to Gly), resulting in the novel designation OXA-30. The predominance of OXA-type enzymes in ampicillin-resistant S. flexneri suggests host preference for specific ␤-lactamases.Resistance to multiple antibiotics is common among clinical isolates of shigella. A previous study showed that 79% of the shigella isolates in our locality were resistant to ampicillin (26), among which 81% were also resistant to trimethoprim-sulfamethoxazole. Recently, nalidixic acid resistance was documented among 59.6% of Shigella flexneri isolates in Hong Kong (5). Although only one strain was reported to harbor ciprofloxacin resistance in that study, it is anticipated that resistance will develop quickly with widespread usage. Additionally, the use of quinolones in children, in whom bacillary dysentery most commonly occurs, should be avoided because of evidence of cartilage toxicity in the skeletally immature (9, 23). Alternative antimicrobial agents thus have to be sought.Ampicillin-sulbactam has been suggested for the treatment of multidrug-resistant shigellosis because of its good in vitro activity. In a study of 129 shigella strains obtained between 1984 and 1987, only 2% were resistant to ampicillin-sulbactam (12). However, a recent study yielded contradictory results (5): most shigella isolates were resistant or only moderately susceptible to amoxicillin-clavulanate. Among members of the family Enterobacteriaceae, TEM-1 hyperproduction (25) and harboring of inhibitor-resistant TEM and OXA-1 ␤-lactamases have been reported to be mechanisms of resistance to ␤-lactamase-␤-lactamase inhibitor combinations (14,20). In order to elucidate the situation for shigella isolates in Hong Kong and Shanghai, ␤-lactamases from these isolates were characterized. MATERIALS AND METHODSBacterial strains and screening for antimicrobial susceptibility. S. flexneri isolates were obtained from inpatients with diarrheal disease in a teaching hospital in Hong Kong and from a public health laboratory in Shanghai. Screening for ampicillin resistance was performed b...

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A novel, inhibitor-potentiated disc-diffusion test for detecting extended-spectrum beta-lactamases (ESBLs) in bacteria was evaluated. This test uses the principle of augmentation (by > or = 10 mm) of inhibition zones produced by ceftazidime, cefotaxime, ceftriaxone or aztreonam discs on Mueller-Hinton agar supplemented with clavulanate (4 mg/L). The test was initially compared with the double-disc synergy test, Kirby-Bauer disc-diffusion test and Etest ESBL screen with a panel of 45 reference strains with known resistance profiles. This panel consisted of 27 ESBL-positive Escherichia coli strains expressing 14 Bush group 2be enzymes and 18 other E. coli and Klebsiella pneumoniae strains (14 non-ESBL beta-lactamase producers and four non-beta-lactamase producers). The Kirby-Bauer disc-diffusion test was the least sensitive method: 11-44% of the ESBL-positive control strains were misclassified as susceptible to ceftazidime, cefotaxime, ceftriaxone or aztreonam when interpreted by National Committee for Clinical Laboratory Standards (NCCLS) criteria. The sensitivities of the inhibitor-potentiated disc-diffusion test, the double-disc synergy test (when discs were 25 or 30 mm apart) and the Etest ESBL screen (with a breakpoint of > 4-fold reduction in ceftazidime MIC in the presence of clavulanate) were 100%, 96% and 89-96%, respectively. The inhibitor-potentiated disc-diffusion test was further evaluated with 81 E. coli and K. pneumoniae clinical isolates, which were identified as putative ESBL-producers by the double-disc synergy test. For these isolates, the sensitivity of both the inhibitor-potentiated disc-diffusion test and the Etest ESBL screen was 100%. In conclusion, the inhibitor-potentiated disc-diffusion test is a sensitive, convenient and inexpensive method of screening for ESBLs in E. coli and K. pneumoniae isolates, with potential for incorporation into routine clinical laboratory service.

The ␤-lactamase gene blaA BPS in Burkholderia pseudomallei was cloned and expressed in Escherichia coli. BPS-1 is a cephalosporinase with an isoelectric point of 7.7. Sequence analysis of BPS-1 revealed conserved motifs typical of class A ␤-lactamases and a relationship to the PenA (in B. cepacia) and BlaI (in Yersinia enterocolitica) lineages.

Aims-To assess the routine use of a polymerase chain reaction (PCR) assay for the direct detection of Mycobacterium tuberculosis in expectorated sputum specimens. Methods-A pair of primers (20-mer) were designed to amplify the 38 kilodalton protein of M tuberculosis. The specificity of the assay was evaluated in 31 M tuberculosis strains, 15 atypical mycobacterium species, and several commensal bacteria of the upper respiratory tract. The assay was subsequently applied to 519 sputum specimens from 85 inpatients of a chest hospital in Hong Kong.Results-An amplified product of 239 base pairs was found in all M tuberculosis strains, standard strains of M bovis, and M africanum but not in the other bacterial strains tested. For the 51 patients with pulmonary radiographic lesions, the diagnosis of pulmonary tuberculosis was subsequently confirmed by both culture and PCR in 41 of them. Five patients who were treated before admission were positive by PCR alone. All but one patient in the control group (patients with acute exacerbation of chronic obstructive airway diseases) or those with atypical mycobacterial diseases were PCR negative. The PCR remained positive after four weeks of anti-tuberculosis treatment in 29 patients, 16 of whom had become culture negative. Conclusion-This PCR assay is a useful technique for the diagnosis of untreated and recently treated cases of pulmonary tuberculosis.