Changing patterns of susceptibilities of blood, urinary and respiratory pathogens in Hong Kong

In vitro activity of fosfomycin in combination with linezolid against clinical isolates of methicillin-resistant Staphylococcus aureus

The objective of this paper was to investigate the in vitro effects of fosfomycin combined with linezolid against methicillin-resistant Staphylococcus aureus (MRSA). A total of 102 MRSA isolates isolated from clinical specimens of human infections from three hospitals in China were studied. The microdilution checkerboard method was used to determine whether combinations act synergistically against these isolates. The susceptibility results for fosfomycin and linezolid were interpreted according to the guidelines of the Clinical and Laboratory Standards Institute. Synergy and indifference were defined as a fractional inhibitory concentration index of ⩽0.5 and >0.5 but ⩽4, respectively. The combination of fosfomycin and linezolid demonstrated the following interactions: 98.04% (100/102) synergism; 1.96% (2/102) indifference; no antagonism was seen. Thus, the combination between fosfomycin and linezolid shows synergism for most of the MRSA isolates tested in this study. If these findings are confirmed in further in vitro or in vivo studies, the above combination could be tested clinically for difficulty to treat MRSA infections, particularly those warranting prolonged oral therapy.

Evaluation of the LightCycler methicillin-resistant Staphylococcus aureus (MRSA) advanced test for detection of MRSA nasal colonization

Rapid detection of methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization is crucial for the prevention and control of MRSA infections in health care settings. The LightCycler MRSA Advanced Test (Roche Diagnostics) is a commercially available real-time PCR assay for direct detection of MRSA nasal colonization by targeting of the staphylococcal cassette chromosome mec (SCCmec)-orfX junction. The diagnostic performance of the assay was compared with that of ChromID MRSA agar (bioMérieux) culture and an in-house duplex real-time PCR assay. Among 1,246 nasal swab specimens collected from 2 general hospitals in Hong Kong, 174 (14%) were considered true positive for MRSA. Chromogenic culture and the in-house real-time PCR assay identified 147 (84.5%) and 133 (76.4%) true-positive cases with specificities of 100% and 98.6%, respectively. Based on the target melting temperature (Tm) values (57.0 to 62.0 °C) defined by the manufacturer, the LightCycler MRSA Advanced Test identified only 85 (48.9%) true-positive specimens. Interestingly, an additional 60 (34.5%) true-positive specimens were detected despite atypical Tm values of 55 °C, providing overall sensitivity and specificity values of 83.3% and 99%, respectively. Among isolates with Tm values of 55 °C, most were typed as clonal complex 45 (CC45). By sequence analysis of the SCCmec-orfX junction, characteristic single-nucleotide polymorphisms (SNPs) were identified only in isolates with Tm values of 55°C and not in those with typical Tm values. It is conceivable that those SNPs were located inside the target region of the proprietary hybridization probes, which resulted in a Tm shift in the melting curve analysis. Our study highlights the importance of a global evaluation of commercial kits so that the interpretation algorithm covers different lineages of MRSA clones prevalent in various geographical regions.

The use of high-resolution melting analysis for rapid spa typing on methicillin-resistant Staphylococcus aureus clinical isolates

Methicillin-resistant Staphylococcus aureus (MRSA) has been endemic in Hong Kong for three decades. This study evaluated the practical use of high-resolution melting (HRM) real-time PCR analysis on MRSA staphylococcal Protein A (spa) typing on local MRSA isolates. Among 55 clinical MRSA isolates collected in 2011, 12 different spa types were observed by the conventional PCR-sequencing method including the locally predominant spa type t1081 and two locally predominant community acquired MRSA spa types t019 and t437. By using the HRM method, it could differentiate all 12 spa genotypes by distinct melting curves and HRM difference plot analysis. These two methods demonstrated 100% concordance whereas the HRM method required only 3h of turnaround time and one-fifth of reagent cost compared to the conventional method. Our study confirmed that the cost effective and rapid HRM typing approach is practically useful for MRSA community transmission monitoring and nosocomial outbreak control in Hong Kong.

In vitro activity of two old antibiotics against clinical isolates of methicillin-resistant Staphylococcus aureus

The objective of this paper was to investigate the in vitro effects of fusidic acid combined with fosfomycin against methicillin-resistant Staphylococcus aureus (MRSA). In all, 196 MRSA strains isolated from three clinical specimens of human infections from hospitals in China were used in this study. The checkerboard method was used to determine whether combinations act synergistically against these strains. The susceptibility results for fusidic acid and fosfomycin were interpreted according to the guidelines of the Clinical and Laboratory Standards Institute. The combination of fusidic acid and fosfomycin demonstrated the following interactions: 87.76% (172/196) synergism, 12.24% (24/196) indifference and no antagonism was seen (minimum and maximum fractional inhibitory concentration index 0.14 and 0.75, respectively). Thus, combinations of fusidic acid and fosfomycin show synergism for most of the MRSA isolates tested in this study, and may be a future therapeutic alternative for infections caused by MRSA.

Antimicrobial resistance in Escherichia coli outpatient urinary isolates from women: emerging multidrug resistance phenotypes

This study evaluated the antimicrobial resistance profile of outpatient urinary Escherichia coli isolated from women obtained throughout Hong Kong during 2004-2005. Of 1067 single patient isolates analyzed, 60.1% were resistant to ampicillin, 34% were resistant to co-trimoxazole, and 22.1% were resistant to ciprofloxacin. Thirty-four (6.6%) of 519 isolates in 2004 and 55 (10%) of 548 isolates in 2005 were extended-spectrum beta-lactamase (ESBL) producers with a CTX-M phenotype. Rates of non-beta-lactam resistance and ESBL production were strongly influenced by patient age. The age-stratified rates for dual co-trimoxazole and ciprofloxacin resistance and for ESBL production were 10.9% and 7.6% in women aged 18-35 years, 13% and 6.9% in women aged 36-50 years, 20.4% and 8.8% in women aged 51-64 years, and 23.7% and 11.8% in women aged > or =65 years, respectively. Nitrofurantoin and fosfomycin remain active against >90% of the isolates, irrespective of the resistance phenotypes for other drugs. Our results documented the emergence of problematic resistance phenotypes among community urinary E. coli and highlight the need to explore strategies for their containment.

Genomic evidence for antibiotic resistance genes of actinomycetes as origins of antibiotic resistance genes in pathogenic bacteria simply because actinomycetes are more ancestral than pathogenic bacteria

Although in silico analysis have suggested that the antibiotic resistance genes in actinomycetes appear to be the origins of some antibiotic resistance genes, we have shown that recent horizontal transfer of antibiotic resistance genes from actinomycetes to other medically important bacteria have not taken place. Although it has been speculated in Benveniste and Davies' attractive hypothesis that antibiotic resistance genes of actinomycetes are origins of antibiotic resistance genes in pathogenic bacteria because the actinomycetes require mechanisms such as metabolic enzymes (encoded by the antibiotic resistance genes) to degrade the antibiotics they produce or to transport the antibiotics outside the bacterial cells, this hypothesis has never been proven. Both the phylogenetic tree constructed using 16S rRNA gene sequences and that constructed using concatenated amino acid sequences of 15 housekeeping genes extracted from 90 bacterial genomes showed that the actinomycetes is more ancestral to most other bacteria, including the pathogenic Gram-negative bacteria, Gram-positive bacteria, and Chlamydia species. Furthermore, the tetracycline resistance gene of Bifidobacterium longum is more ancestral to those of other pathogenic bacteria and the actinomycetes, which is in line with the ancestral position of B. longum. These suggest that the evolution of antibiotic resistance genes of antibiotic-producing bacteria in general parallels the evolution of the corresponding bacteria. The ancestral position of the antibiotic resistance genes in actinomycetes is probably unrelated to the fact that they produce antibiotics, but simply because actinomycetes are more ancestral than pathogenic bacteria.

Lack of evidence that DNA in antibiotic preparations is a source of antibiotic resistance genes in bacteria from animal or human sources

Although DNA encoding antibiotic resistance has been discovered in antibiotic preparations, its significance for the development of antibiotic resistance in bacteria is unknown. No phylogenetic evidence was obtained for recent horizontal transfer of antibiotic resistance genes from antibiotic-producing organisms to bacteria from human or animal sources.

Serotype distribution and antimicrobial resistance patterns of nasopharyngeal and invasive Streptococcus pneumoniae isolates in Hong Kong children

A study was conducted to determine the vaccine coverage of prevalent carriage and invasive pneumococci from children aged less than 6 years in Hong Kong. A total of 383 nasopharyngeal carriage isolates and 88 invasive isolates from diverse sources were serotyped and their antimicrobial susceptibilities determined. The most common carriage serotypes were the same as the invasive isolates (6B, 14, 19F and 23F), although the rank order of specific serotypes was different. Serotypes in the 7-valent conjugate pneumococcal vaccine (4, 6B, 9V, 14, 18C, 19F and 23F) accounted for 89.7 and 66.1% of the invasive and carriage isolates, respectively. The same seven serotypes comprised 87.5% invasive isolates and 82.8% carriage isolates with resistance to penicillin, erythromycin and/or cefotaxime.

Antimicrobial resistance of Gram-negative bacilli isolates from inpatients and outpatients at Yaounde Central Hospital, Cameroon

OBJECTIVE

To determine and compare antimicrobial susceptibility patterns of pathogenic bacteria from inpatients and outpatients at a university teaching hospital in Yaounde, Cameroon.

METHODS

Gram-negative bacilli isolates (n = 522), obtained from a wide range of clinical specimens (urine, pus and blood) from inpatients and outpatients at Yaounde Central Hospital between March 1995 and April 1998, were evaluated for resistance to antibiotics (amoxicillin, amoxicillin/clavulanate, piperacillin, cefazolin, cefoxitin, cefotaxime, ceftazidime, aztreonam, imipenem, gentamicin, tobramicin, ofloxacin and trimethoprim/sulfamethoxazole).

RESULTS

Of the 522 isolates recorded, 80.3% were Enterobacteriaceae. A high incidence of resistance to amoxicillin (85%), piperacillin (75%) and trimethoprim/sulfamethoxazole (71%) was observed. The proportion of antimicrobial-resistant isolates from inpatients was significantly higher than that from outpatients (P < 0.05), except for piperacillin, tobramicin and trimethoprim/sulfamethoxazole. The combinations of antimicrobial and organism showed that the percentage of ceftazidime-resistant Pseudomonas aeruginosa and ceftazidime-resistant Enterobacter cloacae were 26.8% and 24% respectively. The rate of antimicrobial resistance in isolates from inpatients was not significantly higher than that in isolates from outpatients for all the antimicrobial/organism combinations, except for ceftazidime-resistant Escherichia coli, which was exclusively found in isolates from inpatients. Among Enterobacteriaceae, high and low level penicillinase (mostly in E. coli (13.6% and 11% respectively) and Klebsiella spp. (9% and 8% respectively) were the most important beta-lactam resistance phenotypes (31.2% and 23.6%, respectively). Wild type (exclusively observed in E. coli, Proteus mirabilis and Salmonella spp.) and low level penicillinase were higher in outpatient than inpatient isolates (wild type--17.9% vs 10.8% and low level penicillinase--29.4% vs 20.5%, respectively; P < 0.05). However, extended spectrum beta-lactamase strains (Klebsiella spp. (3.5%), E. coli (2.6%), Citrobacter spp. (0.7%), Enterobacter spp. (0.4%) and P. mirabilis (0.2%)) were exclusively recovered from inpatients. Penicillinase and high level cephalosporinase resistance phenotypes were frequently observed in non-fermenter Gram-negative bacilli (46.6% and 29.1% respectively). However, there were no significant differences in penicillinase and cephalosporinase resistance between inpatient and outpatient isolates.

CONCLUSION

As the incidence of antimicrobial resistance is substantially higher in isolates from inpatient than outpatient pathogens, more resources should be allocated within the hospital to encourage good antibiotic practices and good hospital hygiene.

Facilitation of horizontal transfer of antimicrobial resistance by transformation of antibiotic-induced cell-wall-deficient bacteria

It is universally accepted that the use of antibiotics will lead to antimicrobial resistance. Traditionally, the explanation to this phenomenon was random mutation and horizontal gene transfer and amplification by selective pressure. Subsequently, a second mechanism of antibiotic-induced antimicrobial resistance acquisition was proposed, when Davies et al. discovered that genes encoding antimicrobial resistance are present in bacteria that produce antibiotics, and during the process of antibiotic purification from these antibiotic-producing organisms, remnants of the organisms' DNA that contain antibiotic resistance genes are also co-extracted, and can be recovered in antibiotic preparations. In addition to selective pressure and antimicrobial resistance genes in antibiotic preparations, we hypothesize the third mechanism by which administration of antibiotics leads to antimicrobial resistance. beta-Lactams and glycopeptides damage bacteria by inhibiting cell wall murein synthesis. During the process, cell-wall-deficient forms are generated before the bacteria die. These cell-wall-deficient forms have an increased ability to uptake DNA by transformation. It has been demonstrated that plasmids encoding antimicrobial resistance of Staphylococcus aureus can be transformed to Bacillus subtilis after the B. subtilis was treated with penicillin or lysostaphin, a chemical that damage the cell walls of some Gram-positive bacteria; and that short treatment of Escherichia coli with antibiotics disturbing bacterial cell wall synthesis rendered the cells capable of absorbing foreign DNA. Since bacteria occupying the same ecological niche, such as the lower gastrointestinal tract, is common, bacteria are often incubated with foreign DNA encoding resistance coming from the administration of antibiotics or other bacteria that undergone lysis unrelated to antibiotic-induced killing. As few as a single antibiotic resistant gene is taken up by the cell-wall-deficient form, it will develop into a resistant clone, despite most of the other bacteria are killed by the antibiotic. If the hypothesis is correct, one should reduce the use of antibiotics that perturb bacterial cell wall synthesis, such as beta-lactams, which is the largest group being manufactured, in both humans and animals, in order to reduce the acquisition of antibiotic resistance through this mechanism. In contrast to the old theory that antibiotics only provide selective pressures for the development of antimicrobial resistance, antibiotics by themselves are able to generate the whole chain of events towards the development of antimicrobial resistance. Antibiotics provide a source of antimicrobial resistance genes, facilitate the horizontal transfer of antimicrobial resistance genes through facilitating transformation, and provide selective pressures for amplification of the antimicrobial resistance genes. That is perhaps an important reason why antimicrobial resistance is so difficult to control. Further experiments should be performed to delineate which particular type of beta-lactam antibiotics are associated with increase in transformation efficiencies more than the others, so that we can select those less resistance generating beta-lactam for routine usage.

Bacteraemia in Europe—antimicrobial susceptibility data from the MYSTIC surveillance programme

The in vitro antimicrobial susceptibility of organisms isolated from bacteraemic versus non-bacteraemic patients was evaluated using data (1997-2001) from the Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) Programme. Minimum inhibitory concentration values and susceptibility breakpoints of meropenem and other broad-spectrum antimicrobials were determined using standard methodology. Three thousand one hundred and thirty-six blood culture (BC) isolates and 17261 non-BC isolates were obtained from 51 European MYSTIC centres. Gram-positive bacteria appeared to be more prevalent in BC isolates compared with other sources. Escherichia coli, methicillin-susceptible Staphylococcus aureus and Pseudomonas aeruginosa were isolated most frequently. Antimicrobial susceptibility of isolates from bacteraemic versus non-bacteraemic patients was similar. Meropenem and imipenem were the most active agents against the majority of the Gram-positive and Gram-negative organisms. Ceftazidime, gentamicin and ciprofloxacin generally exhibited the lowest activities against the most commonly isolated organisms. Meropenem was most active against P. aeruginosa and showed the highest potency and activity against all extended-spectrum and AmpC beta-lactamase producers. These results are relevant to the choice of initial, empirical therapy for patients with suspected bacteraemia.

Worldwide trends in antimicrobial resistance among common respiratory tract pathogens in children

BACKGROUND

Respiratory tract infections among children are a common reason for health care provider visits and the primary reason for antimicrobial prescribing in this population. The increased prevalence of resistance among Streptococcus pneumoniae and Haemophilus influenzae pathogens poses a serious challenge in the successful treatment of respiratory tract infections caused by these pathogens.

METHODS

This paper reviews worldwide trends in antimicrobial resistance among common respiratory tract pathogens, highlighting data obtained from the pediatric population where available.

RESULTS

S. pneumoniae resistance to beta-lactams is mediated through alterations in the penicillin-binding proteins and macrolide resistance to acquisition of efflux or methylation genes. The mechanisms of resistance to the fluoroquinolones include target enzyme alterations via genetic mutations and transport out of the bacterial cell via an efflux pump. Beta-lactamase production is the primary mechanism of resistance to penicillins among H. influenzae isolates. Although S. pneumoniae with reduced susceptibility to penicillin was first documented > 30 years ago, resistance has increased at an alarming rate worldwide in the past decade. According to recent surveillance data, the worldwide prevalence of S. pneumoniae with reduced susceptibility to penicillin is 18.2%. Beta-lactamase production among H. influenzae ranges from approximately 4% in Russia to 26% in the United States and to 31% in France. The prevalence of beta-lactamase-negative, ampicillin-resistant H. influenzae remains very low (< 1%) worldwide, except in Japan, where the incidence is higher. In general, the highest rates of resistance are observed in isolates obtained from children, and risk factors for infection with a resistant pathogen include young age, the site of infection, day-care center attendance and recent antimicrobial use.

CONCLUSIONS

Increased prevalence of antimicrobial resistance among respiratory tract pathogens isolated from children and adults is evident worldwide. Treatment of infections caused by S. pneumoniae and H. influenzae with older agents or ineffective dosing regimens may not eradicate infections and may contribute to the spread of resistance. These observations confirm the need for appropriate antimicrobial use to halt or at least limit the spread of resistance.

Carriage of methicillin-resistant Staphylococcus aureus, ceftazidime-resistant Gram-negative bacilli, and vancomycin-resistant enterococci before and after intensive care unit admission

OBJECTIVE

To measure patients' risk for acquiring antibiotic-resistant microorganisms associated with intensive care unit admission.

DESIGN

Prospective, observational study.

SETTING

Ten public hospitals including one university medical center.

PATIENTS

Consecutive patients admitted to ten intensive care units.

INTERVENTIONS

Serial patient surveillance cultures were screened for vancomycin-resistant enterococci, methicillin-resistant Staphylococcus aureus (MRSA), ceftazidime-resistant Gram-negative bacilli (CR-GNB), Acute Physiology and Chronic Health Evaluation II score, and antibiotic and medical device exposures.

MEASUREMENTS AND MAIN RESULTS

A total of 1,697 patient admissions in ten intensive care units were enrolled. The overall carriage rate of antibiotic-resistant bacteria at intensive care unit entry was 12.1% for MRSA, 14% for CR-GNB and 4.7% for both. At discharge from the intensive care unit, new carriage of MRSA, CR-GNB, and both was found in 11.1%, 14.2%, and 2.4% of the patients, respectively. The acquisition rates in the individual units correlated highly and positively with proportion of patients with carriage at intensive care unit entry for both MRSA (n = 10, Pearson's r =.89, p < 0.001) and CR-GNB (n = 10, Pearson's r =.92, p < 0.001). By logistic regression, severity of illness (odds ratio, 1.4), length of stay (odds ratio, 1.7), use of penicillins (odds ratio, 1.9), and number of antibiotics (odds ratio, 1.2) and medical devices (odds ratio, 1.2) were independently associated with intensive care unit acquisition of MRSA. In comparison, variables independently associated with intensive care unit acquisition of CR-GNB were Acute Physiology and Chronic Health Evaluation II score (odds ratio, 1.5), number of antibiotics (odds ratio, 1.1), and artificial airway (odds ratio, 1.5).

CONCLUSIONS

These data suggest that hospitalization in the intensive care unit introduces significant risk to patients in terms of transmission of MRSA and/or CR-GNB. This risk seems to be influenced strongly by the proportion of patients with colonization at intensive care unit admission and is associated with severity of illness, length of stay, and exposures to antibiotics and medical devices.

Nasopharyngeal carriage of antimicrobial-resistant Streptococcus pneumoniae among young children attending 79 kindergartens and day care centers in Hong Kong

Resistance to penicillin and multiple antimicrobial agents among Streptococcus pneumoniae strains is becoming an increasing problem worldwide and in Asia. To determine the prevalence of carriage of S. pneumoniae isolates not susceptible to penicillin in young children, we obtained nasopharyngeal swab specimens from 1,978 children (ages, 2 to 6 years) attending 79 day care centers or kindergartens. Three hundred eighty-three strains of S. pneumoniae were isolated from these children. Fifty-eight percent of these isolates had reduced susceptibility to penicillin, 123 (32.1%) were intermediate, and 100 (26.1%) were resistant. A very high penicillin MIC (4 microg/ml) was found in 3.3% of the isolates. The isolates also demonstrated high rates of resistance to other antimicrobial agents (51.2% to cefaclor, 50.2% to cefuroxime, 42.8% to cefotaxime, 80.7% to trimethoprim-sulfamethoxazole, 77% to erythromycin, 60% to clindamycin, and 33.7% to chloramphenicol). No isolate was resistant to fluoroquinolone. Multidrug resistance (not susceptible to the beta-lactams and three or more other classes) was found in 39.4% of the isolates. Risk factors for the carriage of S. pneumoniae not susceptible to penicillin were multiple physician visits in the preceding 3 months and use of antimicrobial agents by the individual or by household members in the preceding 3 months. In the logistic regression analysis, only the use of antimicrobial agents in the preceding 3 months was an independent risk factor (P = 0.004; odds ratio, 2; 95% confidence interval, 1.2 to 3.2). This study demonstrated the high prevalence of antibiotic-resistant S. pneumoniae in healthy young children in the community in Hong Kong.

Emergence of fluoroquinolone resistance among multiply resistant strains of Streptococcus pneumoniae in Hong Kong

The MICs of 17 antimicrobial agents for 181 Streptococcus pneumoniae strains were determined by the E-test. Overall, 69.1% were penicillin resistant (MIC > 0.06 microgram/ml). Resistance to ciprofloxacin (MIC > 2 microgram/ml), levofloxacin (MIC > 2 microgram/ml), or trovafloxacin (MIC > 1 microgram/ml) was found in 12.1, 5.5, or 2.2% of the strains, respectively. These high rates of resistance raise concerns for the future.

The effect of Pseudomonas aeruginosa infection on clinical parameters in steady-state bronchiectasis

STUDY OBJECTIVE

To investigate the effect of Pseudomonas aeruginosa infection on clinical parameters in Chinese patients with noncystic fibrosis and steady-state bronchiectasis.

DESIGN

Prospective, cross-sectional clinicomicrobiological study with informed consent.

SETTING

Consecutive outpatient recruitment from a specialist bronchiectasis respiratory clinic.

PATIENTS

Outpatients (n = 100; 62 women; 55.1+/-16.7 years old; FEV1/FVC 1.4+/-0.7/2.1+/-0.9 L), who had stable respiratory symptoms for more than 3 weeks.

MEASUREMENTS AND RESULTS

Respiratory pathogens isolated from the sputum were: Pseudomonas aeruginosa (33), Haemophilus influenzae (10), Moraxella catarrhalis (2), other Gram-negative bacilli (5), Streptococcus pneumoniae (6), Staphylococcus aureus (5), mycobacteria (3), and yeast (1). Clinical parameters in patients with positive isolation of P aeruginosa were compared with those without the organism in the sputum culture (non-P aeruginosa). In the P aeruginosa group, the FEV1/FVC ratio and sputum volume were lower (p < 0.005) and higher (p < 0.0001), respectively, than those of the non-P aeruginosa group. The FEV1/FVC ratio (< 60%) and sputum volume (grading > 5) were independently associated with a positive sputum isolation of P aeruginosa with odds ratios of 3.1 (confidence interval [CI] 1.2 to 8.4; p < 0.01) and 4.7 (CI 1.6 to 13.3; p < 0.001), respectively.

CONCLUSIONS

P aeruginosa is the predominant respiratory pathogen isolated in the sputum of Chinese patients with steady-state bronchiectasis, and its isolation is associated with high sputum output (> or = 75th quartile) and moderately severe airflow obstruction (FEV1/FVC < 60%).

A population-based survey of Haemophilus influenzae type b nasopharyngeal carriage prevalence in Lombok Island, Indonesia

BACKGROUND

The Haemophilus influenzae type b (Hib) nasopharyngeal carriage prevalence and invasive disease incidence rates are unknown in Indonesia; consequently Hib vaccine is not included in the routine vaccine schedule.

METHODS

To determine carriage prevalence we conducted a population-based, island-wide prospective study of a systematic sample of 484 children 0 to 2 years of age in Lombok, Indonesia. We conducted a risk factor questionnaire and determined serotypes and antibiotic sensitivity patterns.

RESULTS

We identified 155 H. influenzae isolates, of which 22 were type b and 12 were encapsulated but not type b. The age- and population-weighted Hib carriage prevalence, adjusted for the sampling design, was 4.6% (95% confidence interval, 3.7 to 5.5%). Children younger than 6 months of age had a carriage prevalence less than one-half that of older children, and carriage varied within the four administrative regions of the island; otherwise no risk factors for Hib carriage were identified. All Hib specimens were sensitive to ampicillin and 20 (91%) were sensitive to chloramphenicol.

CONCLUSIONS

The Hib carriage prevalence in Lombok is similar to that found in developed countries before vaccine introduction. This suggests that further studies should proceed to determine whether Lombok has invasive disease rates as high as those that justified vaccine introduction in developed countries.