Risk factors for isolation of Streptococcus pneumoniae with decreased susceptibility to penicillin G from patients infected with human immunodeficiency virus

Invasive Pneumococcal Disease in People Living with HIV: A Retrospective Case-Control Study in Brazil

HIV-infected patients are at particular risk for invasive pneumococcal disease (IPD). We describe cases of IPD in people living with HIV/AIDS (PLWHA) and find associated risk factors for infection and death.

METHODS

A retrospective case-control study, nested in a cohort, including PLWHA with and without IPD, conducted in Brazil, 2005-2020. Controls were of the same gender/age and seen at the same time/place as cases.

RESULTS

We identified 55 episodes of IPD (cases) in 45 patients and 108 controls. The incidence of IPD was 964/100,000 person-years. A total of 42 of 55 (76.4%) IPD episodes presented with pneumonia and 11 (20%) with bacteremia without a focus and 38/45 (84.4%) were hospitalized. Blood cultures were positive in 54/55 (98.2%). Liver cirrhosis and COPD were the only factors associated with IPD in PLWHA in univariate analysis, although no associated factors were found in multivariate analysis. Penicillin resistance was found in 4/45 (8.9%). Regarding antiretroviral therapy (ART), 40/45 (88.9%) cases vs. 80/102 controls (74.1%) were in use (p = 0.07). Patients with HIV and IPD had a higher CD4 count of 267 cells/mm³ compared with the control group, in which it was 140 cells/mm³ (p = 0.027). Pneumococcal vaccination was documented in 19%. Alcoholism (p = 0.018), hepatic cirrhosis (p = 0.003), and lower nadir CD4 count (p = 0.033) were associated with the risk of death in patients with IPD. In-hospital mortality among PLWHA and IPD was 21.1%, and it was associated with thrombocytopenia and hypoalbuminemia, elevated band forms, creatinine, and aspartate aminotransferase (AST).

CONCLUSIONS

The incidence of IPD in PLWHA remained high despite ART. The vaccination rate was low. Liver cirrhosis was associated with IPD and death.

Pneumococcal vaccination for HIV-infected individuals in Singapore

Susceptibility to infections with pneumococcal bacteria ( Streptococcus pneumoniae) is substantially higher among human immunodeficiency virus (HIV)-infected individuals, and accounts for a significant burden of morbidity and healthcare costs. Pneumococcal vaccination is recommended in most countries for HIV-infected adults. Current policy in Singapore and Australia recommends the use of the 23-valent pneumococcal polysaccharide vaccine (PPSV23) as a booster dose following the use of 13-valent pneumococcal conjugate vaccine (PCV13). Despite this, adherence to this policy has been suboptimal in Singapore. This may be related to the fact that PPSV23 has not been shown to have any impact on pneumococcal carriage (the necessary prerequisite for disease development). PPSV23 has also been associated with immune hyporesponsiveness, raising concerns over the use of this vaccine globally and, in particular, in high-risk populations. The lack of data from studies comparing PCV13 and PPSV23 has also contributed to the suboptimal uptake of pneumococcal vaccines by healthcare professionals for HIV-infected individuals. This review article discusses the key issues and importance of rigorous pneumococcal vaccination programmes for HIV-infected individuals. Current recommendations for pneumococcal vaccination of HIV-infected individuals in Singapore should be adopted more readily to reduce the burden of pneumococcal disease in this high-risk group.

Antibiotics susceptibility pattern of Streptococcus pneumoniae isolated from sputum cultures of human immunodeficiency virus infected patients in Yaoundé, Cameroon

Introduction

The susceptibility of Streptococcus pneumoniae to commonly used antibiotics is threatened by the emergence of resistance of S. pneumonia strains. So, to improve the management of lower respiratory tract infections (LRTIs) in human immunodeficiency virus infected patients, we assessed the antibiotic susceptibility of Streptococcus pneumoniae which is the most common bacterial cause of LRTIs in patients.

Methods

A cross sectional study was carried out from May to October 2014. HIV infected patients suspected of LRTIs attending the Center Medical laboratory and those followed up at the authorized treatment center of Yaounde Military Hospital in Cameroon were enrolled. Sputum was collected from each patient and cultured; identification of microorganisms was performed following standard methods. The disk diffusion method was used for antibacterial susceptibility testing according to the Antibiogram Committee of French Society for Microbiology guidelines.

Results

A total of 51 (25.5%) isolates of S. pneumoniae were recovered from sputum samples obtained from 200 HIV infected patients aged 19-66 years old (mean age: 36±10.087 years old); 144 (72%) of them were female (sex ratio M/F: 1/3). S. pneumoniae carriage was not age dependent (P = 0.384) and was significantly higher in male compared to female (P = 0.008). S. pneumoniae isolates were susceptible to amoxicillin-clavulinic acid (100%), pristinamycin (100%), erythromycin (100%) and cefixime (98.04 %). Highest resistance rates were recorded with fusidic acid (100%), fosfomycin (100%) and tetracyclin (100%).

Conclusion

S. pneumoniae is still susceptible to some agents in our study area however; ongoing surveillance for antimicrobial susceptibility remains essential to identify emerging resistance and attempt to limit its spread.

HIV-related pneumococcal disease prevention in adults

INTRODUCTION

HIV-infected persons are particularly susceptible to the development of severe pneumococcal disease, even in the setting of combination antiretroviral therapy (cART), due to slow, incomplete recovery of anti-pneumococcal host defenses. This risk is increased by avoidable aspects of lifestyle, particularly smoking, which intensify immunosuppression. Clearly, more effective preventive measures are needed to counter this threat. Areas covered: This is a detailed review of the published literature focusing on currently available strategies for prevention of pneumococcal infection in HIV-infected patients, including cotrimoxazole prophylaxis, cART, pneumococcal vaccination, and smoking cessation strategies. This is preceded by a consideration of the epidemiology, clinical presentation, risk factors, and outcome of pneumococcal disease. Expert commentary: Cotrimoxazole prophylaxis has been shown to reduce morbidity and mortality in HIV-infected patients, although there is inconsistent data on the preventive efficacy against pneumococcal infections. Some recent studies have documented unchanged incidences of IPD in adult patients in the cART era. With regard to pneumococcal vaccination, routine acceptance of the efficacy of the PCV13/PPV23 sequential administration prime-boost strategy awaits the outcome of clinical trials in those with HIV infection. Smoking cessation, and discontinuation of excessive alcohol consumption and intravenous drug abuse, are priority strategies to prevent severe pneumococcal infection.

Epidemiological interpretation of studies examining the effect of antibiotic usage on resistance

Bacterial resistance to antibiotics is a growing clinical problem and public health threat. Antibiotic use is a known risk factor for the emergence of antibiotic resistance, but demonstrating the causal link between antibiotic use and resistance is challenging. This review describes different study designs for assessing the association between antibiotic use and resistance and discusses strengths and limitations of each. Approaches to measuring antibiotic use and antibiotic resistance are presented. Important methodological issues such as confounding, establishing temporality, and control group selection are examined.

Invasive pneumococcal disease in HIV-infected adults in France from 2000 to 2011: antimicrobial susceptibility and implication of serotypes for vaccination

PURPOSE

Invasive pneumococcal diseases (IPD) remain frequent and severe events in human immunodeficiency virus (HIV)-infected subjects despite the use of antiretroviral therapy and the availability of vaccines. Our aim was to assess the antibiotic susceptibilities and serotypes of strains responsible for IPD in HIV-infected patients.

METHODS

We retrospectively analyzed all Streptococcus pneumoniae strains isolated from normally sterile sites between 2000 and 2011 in HIV-infected patients from a single reference center in Paris. The minimum inhibitory concentrations were determined by the E-test, and serotyping was performed by the antiserum agglutination method.

RESULTS

Among our study group, 41 HIV-infected adults presented 43 IPD during the study period. Of these 41 patients, 78 % were men, and the median age was 43 (range 23-62) years. the median CD4 cell count was 184/mm(3) (6-1,090/mm(3)), 51 % were receiving antiretroviral therapy, and 24 % had plasma HIV-RNA levels of <400 copies/mL. Only two patients had received the pneumococcal polysaccharide 23-valent vaccine (PPV23). Isolates were susceptible to penicillin G, amoxicillin, and cotrimoxazole in 44, 70, and 59 % of cases, respectively, and were significantly less susceptible to these antibiotics than isolates in the French general population during the same period. Among the 27 strains serotyped, 18 different serotypes were observed, of which 19A, 14, 7F, and 6A were the most frequent. Serotype distribution was similar to that in the French general population. The PPV23 vaccine and the 13-valent conjugate vaccine (PCV13) would have theoretically covered 78 and 70 % of cases, respectively.

CONCLUSIONS

In our HIV-infected patient cohort, S. pneumoniae isolates demonstrated higher levels of resistance to beta-lactamines and cotrimoxazole than in the French general population. HIV-infected patients should benefit from the herd protection effect expected from the large-scale vaccination of children by PCV13.

Does trimethoprim-sulfamethoxazole prophylaxis for HIV induce bacterial resistance to other antibiotic classes? Results of a systematic review

BACKGROUND

Trimethoprim-sulfamethoxazole (TMP-SMX) prophylaxis has long been recommended for immunosuppressed HIV-infected adults and children born to HIV-infected women. Despite this, many resource-limited countries have not implemented this recommendation, partly because of fear of widespread antimicrobial resistance not only to TMP-SMX, but also to other antibiotics. We aimed to determine whether TMP-SMX prophylaxis in HIV-infected and/or exposed individuals increases bacterial resistance to antibiotics other than TMP-SMX.

METHODS

A literature search was conducted in Medline, Global Health, Embase, Web of Science, ELDIS, and ID21.

RESULTS

A total of 501 studies were identified, and 17 met the inclusion criteria. Only 8 studies were of high quality, of which only 2 had been specifically designed to answer this question. Studies were classified as (1) studies in which all participants were infected and/or colonized and in which rates of bacterial resistance were compared between those taking or not taking TMP-SMX and (2) studies comparing those who had a resistant infection with those who were not infected. Type 1 studies showed weak evidence that TMP-SMX protects against resistance. Type 2 studies provided more convincing evidence that TMP-SMX protects against infection.

CONCLUSION

There was some evidence that TMP-SMX prophylaxis protects against resistance to other antibiotics. However, more carefully designed studies are needed to answer the question conclusively.

Bacteraemic pneumococcal pneumonia: Impact of HIV on clinical presentation and outcome

OBJECTIVES

The objectives of this study were to investigate the clinical and laboratory features, hospital course and outcome of patients with bacteraemic pneumococcal pneumonia, comparing HIV with non-HIV patients, as well as HIV patients from different parts of the world.

METHODS

This was a multicentre prospective observational study of consecutive adult cases with bacteraemic pneumococcal pneumonia in 10 countries on 6 continents.

RESULTS

A total of 768 cases were recruited, of which 200 were HIV-infected; 166 were from South Africa. Lower age, i.v. drug use, fewer co-morbid illnesses, and a higher frequency of respiratory symptoms were significantly more likely to occur in HIV patients. The 14-day mortality for the group as a whole was 14.5%, being 16% in the HIV patients and 13.9% in the non-HIV patients (not significant). When adjustments were made for age and severity of illness, HIV patients had significantly higher 14-day mortality with significant trend for increasing 14-day mortality in those with lower CD4 counts. Despite differences in various clinical and laboratory parameters in patients from different parts of the world, on multivariate analysis, when adjusting for regional differences, the HIV-infected patients were still noted to have poorer 14-day mortality.

CONCLUSIONS

This study, in contrast to previous investigations, indicates that there are significant differences in the clinical presentation and outcome of bacteraemic pneumococcal pneumonia when comparing HIV and non-HIV patients.

Clinical impact and cost-effectiveness of co-trimoxazole prophylaxis in patients with HIV/AIDS in Côte d'Ivoire: a trial-based analysis

BACKGROUND

In 2000, WHO/UNAIDS recommended co-trimoxazole prophylaxis for persons at early stages of HIV infection (WHO stage > or = 2) in sub-Saharan Africa.

OBJECTIVE

To assess the cost-effectiveness of alternative strategies for initiation of co-trimoxazole in Côte d'Ivoire.

DESIGN

Cost-effectiveness analysis with an HIV simulation model using clinical and cost data from a randomized trial of co-trimoxazole in HIV-infected adults.

METHODS

The study included HIV-infected patients in Côte d'Ivoire, with median age 33 years. Thirty-four percent were classified as WHO stage 2, 59% as stage 3, and 7% as stage 4. The mean CD4 cell count was 331 x 10(6) cells/l. The interventions were no prophylaxis, clinical criteria-based co-trimoxazole initiation (early: WHO stage > or = 2; late: WHO stage > or = 3), CD4-based co-trimoxazole initiation (< 500, < 200, < 50 x 10(6) CD4 cells/l). The outcome measures were life expectancy, lifetime costs, and incremental cost-effectiveness.

RESULTS

The most effective strategy, initiation of co-trimoxazole prophylaxis at WHO stage > or = 2, increased undiscounted life expectancy by 5.2 months, discounted life expectancy by 4.4 months, and lifetime costs by US dollars 60, compared with no prophylaxis. Delaying prophylaxis initiation until WHO stage >or = 3 was less costly and less effective. All CD4-based strategies were dominated. The incremental cost-effectiveness of early versus late co-trimoxazole prophylaxis initiation was US dollars 200/year of life gained. Results were stable despite wide variations in plausible assumptions about bacterial resistance and the prophylaxis efficacy on co-trimoxazole-resistant strains.

CONCLUSIONS

For HIV-infected adults in Côte d'Ivoire, co-trimoxazole prophylaxis is reasonably cost-effective and most effective if initiated when WHO stage > or = 2. Early co-trimoxazole prophylaxis will prevent complications prior to antiretroviral therapy initiation and should be considered an essential component of care for early HIV in sub-Saharan Africa.

Low colonization prevalence of Staphylococcus aureus with reduced vancomycin susceptibility among patients undergoing hemodialysis in the San Francisco Bay area

BACKGROUND

Staphylococcus aureus exhibits varying degrees of reduced vancomycin susceptibility, and strains with intermediate levels of resistance are thought to emerge by antibiotic selection of subpopulations in heterogeneously resistant precursor strains exposed to this antibiotic. We sought to determine the prevalence of and risk factors for carriage of potential heterogeneous vancomycin-intermediate S. aureus (hVISA).

METHODS

We prospectively observed a cohort of 211 patients undergoing hemodialysis and performed quarterly surveillance cultures for up to 2 years. We screened for reduced vancomycin susceptibility using brain-heart infusion agar with 4 microg/mL vancomycin.

RESULTS

We identified 10 colonizing potential hVISA isolates recovered from 7 patients among both methicillin-susceptible and methicillin-resistant S. aureus strains. No confirmed hVISA isolates were identified; we can be 95% certain that the prevalence of confirmed hVISA carriage does not exceed 1.4%. When compared with noncolonized hemodialysis patients, neither vancomycin exposure, duration of hospitalization, nor any baseline clinical or demographic factor was found to predict colonization with potential hVISA on univariate analyses; increased number of months receiving hemodialysis was associated with potential hVISA colonization on multivariate analysis.

CONCLUSIONS

Despite numerous published reports of S. aureus with reduced vancomycin susceptibility, carriage of these isolates remains a rare phenomenon. Given the unclear clinical significance of potential hVISA, it is not clear whether clinical laboratories should identify such strains, or how they should do so.

Invasive pneumococcal disease in patients infected with HIV: still a threat in the era of highly active antiretroviral therapy

We studied all human immunodeficiency virus (HIV)-infected patients with invasive pneumococcal disease who received their diagnosis during 1996-2002 to investigate the incidence of this disease in the highly active antiretroviral therapy era and to study the influence of CD4 lymphocyte count on the clinical presentation and outcome of disease. The overall incidence of invasive pneumococcal disease was 11.3 cases per 100,000 person-years in adult patients without known HIV infection and 677 cases per 100,000 person-years in HIV-infected patients. This incidence remained stable over the study period. Clinical presentation, severity of illness, and number of recurrent episodes were similar in patients with CD4+ cell counts of >200 or < or =200 cells/ microL. Patients receiving trimethoprim-sulfamethoxazole (TMP-SMZ) were more likely to present with TMP-SMZ-resistant pneumococci than were those who were not receiving this agent (76.7% vs. 43.6%; P=.007). The mortality rate was high (21%).

The epidemiology of antibiotic resistance in Streptococcus pneumoniae and the clinical relevance of resistance to cephalosporins, macrolides and quinolones

Invasive non-meningeal pneumococcal infections remain a major cause of morbidity and mortality worldwide. The factors affecting the epidemiology and mortality of pneumococcal infections are discussed. The increase and spread of resistance to antimicrobial agents among pneumococci is a cause of concern to the clinician. There are links between the usage of antibacterial agents and the development of resistance. Resistance to penicillin and other beta-lactams has become widespread but this does not appear to have decreased the efficacy of some of these agents against non-meningeal infections. There is evidence that the good pharmacokinetic and pharmacodynamic features of the third generation cephalosporins (cefotaxime and ceftriaxone) contribute to their efficacy in vivo. New breakpoints for cefotaxime and ceftriaxone against non-meningeal pneumococcal isolates were proposed by the National Committee for Clinical Laboratory Standard (NCCLS, US), based on the clinical evidence of the efficacy of these drugs. In contrast there is increasing evidence that resistance to macrolides can lead to a poor clinical response. Fluoroquinolones have been widely used to treat respiratory tract infections among others, and pneumococcal resistance to these agents in vitro, although currently low, is increasing. There are reports that resistance to fluoroquinolones can develop during treatment and may be reflected in a lack of clinical response. Several clinical and epidemiological variables (e.g. prior antibiotic use) can be useful to identify patients at risk from infections with antibiotic-resistant pneumococci. These patients would be those who would benefit the most from a pneumococcal vaccination programme.

Rapid emergence of resistance to penicillin and trimethoprim-sulphamethoxazole in invasive Streptococcus pneumoniae in Zimbabwe

Pneumococcal pneumonia and meningitis are common infectious disease problems in people who are HIV seropositive in southern Africa. For many years two inexpensive antibiotics, penicillin and trimethoprim-sulphamethoxazole (TMP-SMX) had been effective in treatment, but recently resistance to these agents has been reported from many parts of the world. This study was designed to determine the antimicrobial resistance patterns in invasive pneumococci from hospital patients in Harare, Zimbabwe. A total of 160 isolates of Streptococcus pneumoniae from blood cultures and CSF cultures were examined. The isolates came from adults and children in hospital in Harare between 1994 and 2000. The majority of isolates came from HIV positive adults (74%) and children (75%). Isolates of pneumococci with an MIC of 1.0 mg/l or more were first seen in 1997 and by 2000 they made up 35% of all isolates. Significantly more isolates from HIV seropositive patients (50%) showed reduced susceptibility to penicillin compared with isolates from HIV seronegative patients (16%), and high level resistance (MIC 1.0 mg/l or higher) was found in 16% isolates from HIV positive patients compared with 6% isolates from HIV seronegative patients. Resistance to TMP-SMX was common, with more than 50% isolates from HIV positive and HIV negative patients having reduced susceptibility to this antibiotic combination.

Streptococcus pneumoniae bacteremia: duration of previous antibiotic use and association with penicillin resistance

Previous antibiotic exposure is one of the most important predictors for acquisition of penicillin-nonsusceptible Streptococcus pneumoniae (PNSP) infection. To determine the impact of duration of exposure to different antibiotic classes, a study of 303 patients with S. pneumoniae bacteremia was undertaken. Ninety-eight cases of bacteremia (32%) were caused by a penicillin-nonsusceptible isolate. Bivariate analysis revealed that use of beta-lactams, sulfonamides, and macrolides within the last 1 and 6 months before presentation was associated with PNSP bacteremia (P<.05). Fluoroquinolone consumption was not related to bacteremia due to PNSP (P>.1). Both short- and long-term beta-lactam use significantly increased the risk for PNSP infection. Logistic regression analysis revealed that use of beta-lactams and macrolides in the 6 months before the first positive blood culture result were independent risk factors (P<.05). Risk for acquiring PNSP infection depends on both the class of antibiotic to which the patient was exposed and the duration of therapy.

Narrow versus broad spectrum antibacterials: factors in the selection of pneumococcal resistance to beta-lactams

Streptococus pneumoniae represents an interesting model to discuss the relative impact of broad versus narrow spectrum antibacterials as potential selectors for resistance. Indeed, this pathogen is responsible for potentially severe infections in the community, and has a great capacity for acquisition of resistance to antibacterial agents. It has been the focus of many studies to elucidate some unique aspects of molecular biology, including the adaptive mechanisms responsible for emergence and spread of multiresistance. In the past, the use of narrow spectrum agents was recommended in order to try to reduce the risk of selection of resistance. This concept is nowadays somewhat obsolete for several reasons. S. pneumoniae is able to acquire resistance to antibacterials belonging to different families of drugs through different molecular mechanisms. Thus, selection of multiresistant pneumococci can result from exposure to very different agents, including narrow spectrum as well as broad spectrum agents. In vitro studies have shown a different potential for selection of resistance among the beta-lactam agents. Furthermore, several studies have more or less directly established a close relationship between the level of antibacterial use and the rate of selection of resistance. In addition to the overall amount of antibacterials prescribed in the community, several other factors have been shown to influence the rate of selection of resistance, including the use of doses that are too low, the length of therapy and the duration of bacterial exposure to long-acting agents compared to drugs with short half-lives. Therefore, there are three main ways to control selection and spread of resistant strains: by (i) reducing the amount of antibacterials used; (ii) using optimal dosages (avoiding underdosing) and treatments of short duration; and (iii) reducing the risk of transmission among young children attending daycare centres or kindergartens. In order to help physicians reduce the number of unnecessary prescriptions, it is important to develop rapid tests to recognise the bacterial origin of a febrile illness and even more important to detect resistance to antibacterials. However, apart from rapid diagnostic tests for streptococcal pharyngitis, those tests are not currently available. As a consequence, currently, the debate around narrow versus broad spectrum antibacterials remains a false debate. Physicians should use broad spectrum agents in many instances of upper or lower respiratory tract infection, taking into consideration the probable pathogens and the risk of (multi)resistance to antibacterials. Once rapid diagnostic are available in community practice, allowing a precise diagnosis of the offending agent and its susceptibility profile, physicians will be able to add to their current criteria the selective potential for resistance of the antibacterials that appear to be active in vitro.

Clinical aspects and cost of invasive Streptococcus pneumoniae infections in children: resistant vs. susceptible strains

Invasive Streptococcus pneumoniae infections in children are associated with serious consequences in terms of morbidity and mortality. The main objective of the study was to determine if invasive infections caused by penicillin-resistant Streptococcus pneumoniae (PRSP) differed in clinical presentation, outcome, risk factors, or cost from those caused by penicillin-susceptible strains (PSSP) in children. All patients aged 18 or less with invasive Streptococcus pneumoniae infections admitted to two teaching hospitals in Montreal between 1989 and 1998 were included in the study. We present a case-control study in which for each index case of PRSP, 3 controls with PSSP infections were matched for age, sex, and site of infection. One hundred and forty-four patients were included in the analysis (36 cases, 108 controls). There was no difference between the two groups in terms of initial clinical presentation (vital signs, laboratory results) or total length of stay. Mortality was 2.7% in both groups. Hospital antibiotic cost was higher in the PRSP group (211 Canadian dollars (CAD) vs. 74 CAD; P=0.02). Antibiotic consumption in the preceding month was significantly associated with PRSP infection. Underlying diseases or day-care attendance were not shown to be significant risk factors for acquiring invasive PRSP infection. There were no differences between invasive infections caused by PRSP and PSSP in terms of clinical presentation, morbidity or mortality in a paediatric population.

Penicillin-resistant Streptococcus pneumoniae in metropolitan New York hospitals: case control study and molecular typing of resistant isolates

During the 4-month period from January to April, 1998, 476 patients with Streptococcus pneumoniae infections were detected in 12 metropolitan New York hospitals and 112 penicillin-resistant (PRP) isolates (24%) were identified in 11 institutions. A case control study of 100 patients with penicillin-resistant and susceptible pneumococci from four of the widely dispersed hospitals revealed a high incidence of underlying medical illnesses in adult patients (74%), a preponderance of patients with pneumonia (63%), and a majority of patients who had underlying risk factors for pneumonia or invasive disease (51%). In this limited case control study, no difference was noted between cases and controls regarding known risk factors for penicillin-resistant pneumococcal infections. The percentage of single-patient PRP isolates varied among individual hospitals but the mean percentages of PRP from the four participating University Medical Centers and seven community hospitals were similar: 26% and 22% respectively. By E-test, 60% and 26% were high-level penicillin and ceftriaxone resistant, respectively. Pulsed-field gel electrophoresis identified 26 chromosomal macrorestriction patterns among the 103 PRP isolates available for analysis, but almost half (50 isolates or 48%) of these belong to two drug-resistant internationally spread clones, SP(23)-1 and SP(9/14)-3, that were detected in all hospitals and were recovered from invasive and noninvasive sites in both children and adults.

Pneumococcal bacteremia in adults in Soweto, South Africa, during the course of a decade

We retrospectively reviewed 414 episodes of pneumococcal bacteremia that occurred in adults from July 1986 through June 1987 (1986/1987) and from July 1996 through June 1997 (1996/1997) to monitor the incidence and clinical and laboratory characteristics and to assess the influence of human immunodeficiency virus (HIV) infection on any changes. The incidence increased from 26 per 100,000 persons in 1986/1987 to 36 per 100,000 persons in 1996/1997; the increase was most marked among patients who were aged 25-44 years (24 cases per 100,000 persons to 45 per cases 100,000 persons) and > or =65 years (43 cases per 100,000 persons to 50 cases per 100,000 persons). Of 161 patients who were tested for HIV in 1996/1997, 108 (67%) were HIV seropositive. Among the general population, the prevalence of other underlying diseases and smoking decreased from 45% and 67%, respectively, in 1986/1987 to 23% (P<.0001) and 35% (P<.0001) in 1996/1997. Strains of pneumococci that were not susceptible to penicillin were found in 4% patients in 1986/1987 and 12% in 1996/1997 (P=.005). This increase occurred exclusively among the HIV-infected patients (22% of the HIV-seropositive patients versus 4% of HIV-seronegative patients; P=.008), and there was a parallel increase for childhood serotypes (51% of HIV-seropositive patients versus 17% of HIV-seronegative patients; P<.0001).

Methodological principles of case-control studies that analyzed risk factors for antibiotic resistance: a systematic review

Case-control studies that analyze the risk factors for antibiotic-resistant organisms have varied epidemiological methodologies, which may lead to biased estimates of antibiotic risk factors. A systematic review of case-control studies that analyzed risk factors for antibiotic-resistant organisms addressed 3 methodological principles: method of control group selection, adjustment for time at risk, and adjustment for comorbid illness. A total of 406 abstracts were reviewed. Thirty-seven studies met the inclusion and exclusion criteria and were reviewed and evaluated for the 3 methodological principles. Thirteen (35%) of 37 studies chose the preferred control group. Eleven adjusted for time at risk. Twenty-seven adjusted for comorbid illness. Future studies need to consider more closely the optimization of control group selection, adjusting for confounding caused by time at risk, and adjusting for confounding caused by comorbid illness.

Colonization by Streptococcus penumoniae in human immunodeficiency virus-infected children

OBJECTIVE

Children with HIV infection are particularly susceptible to invasive pneumococcal disease, yet the effect of HIV infection and its medical management on colonization and resistance to antibiotics are poorly described. To provide a basis for medical practice, we determined the prevalence of nasopharyngeal colonization and antibiotic resistance of Streptococcus pneumoniae in children with HIV infection.

METHODS

Cross-sectional prevalence sample of children attending the pediatric HIV and pulmonary clinics to examine nasopharyngeal colonization with S. pneumoniae and antibiotic resistance to beta-lactams and trimethoprim-sulfamethoxazole (T/S). Subjects were matched by age and date of clinic visit.

RESULTS

The colonization rate with S. pneumoniae of HIV-infected and -indeterminate children was equal to that of controls (20% vs. 19%). HIV infection, CDC staging or receipt of oral antibiotic therapy did not affect colonization. Isolates from HIV-infected and -indeterminate children were less likely to be penicillin-resistant than those from controls (18% vs. 50%). There was no difference in pneumococcal resistance to T/S among isolates from subjects and controls, despite 72% T/S use in the HIV clinic.

CONCLUSION

Colonization with S. pneumoniae in HIV disease is no different from that of comparable children. The high incidence of pneumococcal disease and prophylaxis with T/S are not related to nasopharyngeal colonization. Antibiotic prophylaxis of HIV-infected children does not necessarily lead to increased resistance of S. pneumoniae.

Pneumococcal bacteremia during a decade in children in Soweto, South Africa

OBJECTIVES

To monitor for a decade the incidence and the clinical and microbiologic characteristics of pneumococcal bacteremia in children in Soweto and to assess the influence of HIV infection on any changes.

METHODS

Case records of children with pneumococcal bacteremia at Chris Hani Baragwanath Hospital from July, 1986, to June, 1987 (1986/ 1987), and from July, 1996, to June, 1997 (1996/ 1997), were retrospectively reviewed.

RESULTS

There were 194 episodes, 62 in 19861 1987 and 132 in 1996/1997. The minimum annual incidence for children younger than 5 years of age increased from 61 per 100000 (179 per 100000 for those <12 months old) in 1986/1987 to 130 per 100000 (349 per 100000 for those <12 months old) in 1996/1997. Sixty-seven (60%) of 111 patients tested in 1996/1997 were HIV-seropositive; none were tested in 1986/1987. The HIV-infected compared with HIV-noninfected were more likely to be malnourished (61% vs. 36%, P = 0.02), less likely to have other underlying disease (12% vs. 50%, P = 0.00001) and more frequently used antibiotics recently (69% vs. 43%, P = 0.008). Penicillin-nonsusceptible isolates were found in 22 (35%) patients in 1986/1987 and 52 (39%) in 1996/1997. There was no significant change in antimicrobial susceptibility during the decade or by HIV serostatus.

CONCLUSIONS

Children in Soweto had a high incidence of pneumococcal bacteremia which doubled during the decade mainly as a result of the impact of the HIV epidemic. There has been no significant change in antimicrobial susceptibility for the decade.

Discontinuation of prophylaxis against Mycobacterium avium complex disease in HIV-infected patients who have a response to antiretroviral therapy. Terry Beirn Community Programs for Clinical Research on AIDS

BACKGROUND

Several agents are effective in preventing Mycobacterium avium complex disease in patients with advanced human immunodeficiency virus (HIV) infection. However, there is uncertainty about whether prophylaxis should be continued in patients whose CD4+ cell counts have increased substantially with antiviral therapy.

METHODS

We conducted a multicenter, double-blind, randomized trial of treatment with azithromycin (1200 mg weekly) as compared with placebo in HIV-infected patients whose CD4+ cell counts had increased from less than 50 to more than 100 per cubic millimeter in response to antiretroviral therapy. The primary end point was M. avium complex disease or bacterial pneumonia.

RESULTS

A total of 520 patients entered the study; the median CD4+ cell count at entry was 230 per cubic millimeter. In 48 percent of the patients, the HIV RNA value was below the level of quantification. The median prior nadir CD4+ cell count was 23 per cubic millimeter, and 65 percent of the patients had had an acquired immunodeficiency syndrome-defining illness. During follow-up over a median period of 12 months, there were no episodes of confirmed M. avium complex disease in either group (95 percent confidence interval for the rate of disease in each group, 0 to 1.5 episodes per 100 person-years). Three patients in the azithromycin group (1.2 percent) and five in the placebo group (1.9 percent) had bacterial pneumonia (relative risk in the azithromycin group, 0.60; 95 percent confidence interval, 0.14 to 2.50; P=0.48). Neither the rate of progression of HIV disease nor the mortality rate differed significantly between the two groups. Adverse effects led to discontinuation of the study drug in 19 patients assigned to receive azithromycin (7.4 percent) and in 3 assigned to receive placebo (1.1 percent; relative risk, 6.6; P=0.002).

CONCLUSIONS

Azithromycin prophylaxis can safely be withheld in HIV-infected patients whose CD4+ cell counts have increased to more than 100 cells per cubic millimeter in response to antiretroviral therapy.

Effect of antimicrobial use and other risk factors on antimicrobial resistance in pneumococci

Penicillin-resistant and multi-resistant pneumococci have spread globally and reached high prevalence in many countries. Antimicrobial use is considered a major driving force for resistance, although the influence in the community has not been as clearly demonstrated. Other risk factors may be important, and only with a clear understanding of the risk factors can effective control measures be introduced. The main habitat of the pneumococcus is the nasopharynx of children. Carriage increases from birth and is maximal at pre-school age. Antimicrobial use in children is likely to have a significant influence on the susceptibility of pneumococci. Most studies looking for risk factors for resistance in pneumococci have identified antimicrobial use as a risk factor, especially the following aspects: ongoing, recent, repeated, frequent, and prophylactic antibiotic use. The effect of individual classes of antimicrobials has not been studied in detail but use of beta-lactam antibiotics and trimethoprim-sulpha has been associated with increased risk. Other risk factors are young age, nosocomial acquisition, prior hospitalization, and HIV infection. Day-care centers can facilitate the spread of resistant pneumococci and an Icelandic study showed that carriage of resistant pneumococci was associated with young age, domicile in an area with high antimicrobial consumption, recent antimicrobial use, frequent antimicrobial use, and use of trimethoprim-sulpha. The rapid increase of penicillin-resistant pneumococci in Iceland was met with propaganda against overuse of antimicrobials, which lead to reduction of antimicrobial use and subsequently a reduced incidence of penicillin-resistant pneumococci. This reduction may be related to reduced antimicrobial use. Reducing antimicrobial use should be considered important for programs aimed at reducing antimicrobial resistance.

Invasive pneumococcal disease in the immunocompromised host

A normal constituent of the human upper respiratory flora, Streptococcus pneumoniae also produces respiratory tract infections that progress to invasive disease at high rates in specific risk groups. The individual factors that contribute to the development of invasive pneumococcal disease in this distinct minority of persons, include immune (both specific and innate), genetic, and environmental elements. Specific defects in host responses may involve age, deficiencies in levels of antibodies and complement factors, and splenic dysfunction. Combinations of these immune defects contribute to the increased rates of invasive pneumococcal disease in patients with sickle cell disease, nephrotic syndrome, neoplasms, and underlying medical conditions such as diabetes and alcoholic liver disease. The number of risk factors are greatest and the rates of invasive disease are highest in patients with HIV-1 infection, which has emerged as a major risk factor for serious S. pneumoniae infection worldwide.

Pneumonia acquired in the community through drug-resistant Streptococcus pneumoniae

The aim of the study was to determine the incidence of and risk factors for drug resistance of Streptococcus pneumoniae, and its impact on the outcome among hospitalized patients of pneumococcal pneumonia acquired in the community. Consecutive patients with culture-proven pneumococcal pneumonia were prospectively studied with regard to the incidence of pneumococcal drug resistance, potential risk factors, and in-hospital outcome variables. A total of 101 patients were studied. Drug resistance to penicillin, cephalosporin, or a macrolide drug was found in pneumococci from 52 of the 101 (52%) patients; 49% of these isolates were resistant to penicillin (16% intermediate resistance, 33% high resistance), 31% to cephalosporin (22% intermediate and 9% high resistance), and 27% to a macrolide drug. In immunocompetent patients, age > 65 yr was significantly associated with resistance to cephalosporin (odds ratio [OR]: 5.0; 95% confidence interval [CI]: 1.3 to 18.8, p = 0. 01), and with the presence of > 2 comorbidities with resistance to penicillin (OR: 4.7; 95% CI: 1.2 to 19.1; p < 0.05). In immunosuppressed patients, bacteremia was inversely associated with resistance to penicillin and cephalosporin (OR: 0.04; 95% CI: 0.003 to 0.45; p < 0.005; and OR: 0.46; 95% CI: 0.23 to 0.93; p < 0.05, respectively). Length of hospital stay, severity of pneumonia, and complications were not significantly affected by drug resistance. Mortality was 15% in patients with any drug resistance, as compared with 6% in those without resistance. However, any drug resistance was not significantly associated with death (relative risk [RR]: 2. 5; 95% CI: 0.7 to 8.9; p = 0.14). Moreover, attributable mortality in the presence of discordant antimicrobial treatment was 12%, as compared with 10% (RR: 1.2; 95% CI: 0.3 to 5.3; p = 0.67) in the absence of such treatment. We conclude that the incidence of drug-resistant pneumococci was high. Risk factors for drug resistance included advanced age, comorbidity, and (inversely) bacteremia. Outcome was not significantly affected by drug resistance.

Risk factors and course of illness among children with invasive penicillin-resistant Streptococcus pneumoniae. The Streptococcus pneumoniae Working Group

OBJECTIVES

To assess differences in risk factors, clinical presentation, and course of illness between children infected with penicillin-sensitive and drug-resistant Streptococcus pneumoniae (DRSP).

DESIGN

A retrospective cohort study conducted in Uruguay and Argentina using information from a hospital-based surveillance system. Hospitalized children 5 years of age and younger who had S pneumoniae isolated from a normally sterile site between June 1993 and October 1996 were eligible. Hospital records were linked with surveillance data. Both stratified univariate analysis and logistic regression was completed.

RESULTS

Of the 380 children eligible for the study, 274 records (72%) were available for review. Ninety-nine children (36%) had DRSP; 46 showed intermediate susceptibility (minimum inhibitory concentration, 0.12-1.0 microg/mL) and 53 showed high-level resistance (minimum inhibitory concentration >/=2.0 microg/mL). Children with meningitis were less likely to have DRSP than those with other forms of invasive disease (relative risk = 0. 5; 95% confidence interval [CI], 0.2-0.9). Risk factors associated with DRSP were use of penicillin or ampicillin in the 3 months before illness (odds ratio = 2.9; 95% CI, 1.5-5.7) and possession of private medical coverage (odds ratio = 2.4; 95% CI, 1.2-5.0). Response to therapy, including response to penicillin or ampicillin among children with nonmeningeal invasive disease, course of illness, and clinical outcome did not differ significantly between children infected with penicillin-susceptible or penicillin-resistant isolates.

CONCLUSION

In this study, previous use of penicillin or ampicillin and private medical coverage were associated with having DRSP. Children with nonmeningeal invasive disease responded equally well to penicillin regardless of the penicillin susceptibility of their pneumococcal isolate.

Prior antimicrobials and staphylococcal bacteremia in HIV-infected patients

OBJECTIVE

Many drugs used for prophylaxis against opportunistic infections in AIDS also have activity against common bacteria. This study was performed to delineate relationships between prior use of antimicrobials and Staphylococcus aureus bacteremia.

DESIGN

To compare prior exposure to selected antimicrobial drugs in patients who had S. aureus bacteremia and in controls who did not, a nested case-control study was conducted within a cohort of HIV-infected persons followed in an outpatient clinic.

METHODS

Using a computerized database based on HIV clinic records, 48 cases with S. aureus bacteremia were compared against 188 controls selected from patients with CD4 cell counts < 200 x 10(6)/l. Information on demographic risk factors and antimicrobial drug use was analysed using conditional logistic regression.

RESULTS

Injecting drug use was strongly associated with S. aureus bacteremia. Rifabutin use was associated with decreased risk of S. aureus bacteremia [conditional relative risk (RR) 0.308, 95% confidence interval (CI) 0.096-0.991] in univariate analysis, near statistical significance in multivariate analysis (RR 0.314, 95% CI 0.096-1.023). The bacteremias were not significantly associated with use of trimethoprim-sulfamethoxazole, quinolones, newer macrolides (azithromycin and clarithromycin), clindamycin or dapsone.

CONCLUSIONS

Rifabutin may be associated with diminished risk of S. aureus bacteremia incidental to use for other purposes in HIV infection. Further study is needed to assess effects on microbial resistance.