Drug-resistant pathogens in community- and hospital-acquired pneumonia

Management and prevention of ventilator-associated pneumonia caused by multidrug-resistant pathogens

Ventilator-associated pneumonia (VAP) due to multidrug-resistant (MDR) pathogens is a leading healthcare-associated infection in mechanically ventilated patients. The incidence of VAP due to MDR pathogens has increased significantly in the last decade. Risk factors for VAP due to MDR organisms include advanced age, immunosuppression, broad-spectrum antibiotic exposure, increased severity of illness, previous hospitalization or residence in a chronic care facility and prolonged duration of invasive mechanical ventilation. Methicillin-resistant Staphylococcus aureus and several different species of Gram-negative bacteria can cause MDR VAP. Especially difficult Gram-negative bacteria include Pseudomonas aeruginosa, Acinetobacter baumannii, carbapenemase-producing Enterobacteraciae and extended-spectrum β-lactamase producing bacteria. Proper management includes selecting appropriate antibiotics, optimizing dosing and using timely de-escalation based on antiimicrobial sensitivity data. Evidence-based strategies to prevent VAP that incorporate multidisciplinary staff education and collaboration are essential to reduce the burden of this disease and associated healthcare costs.

Clinical practice guidelines for hospital-acquired pneumonia and ventilator-associated pneumonia in adults

Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) are important causes of morbidity and mortality, with mortality rates approaching 62%. HAP and VAP are the second most common cause of nosocomial infection overall, but are the most common cause documented in the intensive care unit setting. In addition, HAP and VAP produce the highest mortality associated with nosocomial infection. As a result, evidence-based guidelines were prepared detailing the epidemiology, microbial etiology, risk factors and clinical manifestations of HAP and VAP. Furthermore, an approach based on the available data, expert opinion and current practice for the provision of care within the Canadian health care system was used to determine risk stratification schemas to enable appropriate diagnosis, antimicrobial management and nonantimicrobial management of HAP and VAP. Finally, prevention and risk-reduction strategies to reduce the risk of acquiring these infections were collated. Future initiatives to enhance more rapid diagnosis and to effect better treatment for resistant pathogens are necessary to reduce morbidity and improve survival.

Signature-tagged mutagenesis of Klebsiella pneumoniae to identify genes that influence biofilm formation on extracellular matrix material

Klebsiella pneumoniae causes urinary tract infections, respiratory tract infections, and septicemia in susceptible individuals. Strains of Klebsiella frequently produce extended-spectrum beta-lactamases, and infections with these strains can lead to relatively high mortality rates (approximately 15%). Other virulence factors include production of an antiphagocytic capsule and outer membrane lipopolysaccharide (LPS), which mediates serum resistance, as well as fimbriae on the surface of the bacteria. Type 1 fimbriae mediate adherence to many types of epithelial cells and may facilitate adherence of the bacteria to the bladder epithelium. Type 3 fimbriae can bind in vitro to the extracellular matrix of urinary and respiratory tissues, suggesting that they mediate binding to damaged epithelial surfaces. In addition, type 3 fimbriae are required for biofilm formation by Klebsiella pneumoniae on plastics and human extracellular matrix; thus, they may facilitate the formation of treatment-resistant biofilm on indwelling plastic devices, such as catheters and endotracheal tubing. The presence of these devices may cause tissue damage, allowing Klebsiella to grow as a biofilm on exposed tissue basement membrane components. Though in vivo biofilm growth may be an important step in the infection process, little is known about the genetic factors required for biofilm formation by Klebsiella pneumoniae. Thus, we performed signature-tagged mutagenesis to identify factors produced by K. pneumoniae strain 43816 that are required for biofilm formation. We identified mutations in the cps capsule gene cluster, previously unidentified transcriptional regulators, fimbrial, and sugar phosphotransferase homologues, as well as genetic loci of unknown function, that affect biofilm formation.

Quinolones for treatment of nosocomial pneumonia: a meta-analysis

Although quinolones are often used to treat nosocomial pneumonia (NP), there have been few trials documenting their efficacy in treating NP. Given the growing use of quinolones and issues regarding resistance, we conducted a meta-analysis of all trials of quinolones for treatment of NP. We identified 5 randomized trials comparing quinolones with other agents used to treat NP. The studies varied in both quality and sample size and included a total of nearly 1200 subjects. Four of the 5 trials used ciprofloxacin, administered every 8 h, whereas the fifth used levofloxacin administered daily. In 3 trials, the comparator agent was imipenem-cilistatin, whereas, in 2 trials, ceftazadime was the comparator agent. The efficacy of quinolones and comparator antibiotics was similar, with a pooled odds ratio for clinical cure of 1.12 (95% confidence interval, 0.80-1.55). Neither microbiological eradication rates nor mortality rates varied on the basis of antimicrobial selection.

Etiology of community-acquired pneumonia

Community-acquired pneumonia (CAP) is a serious lower respiratory tract infection associated with significant morbidity and mortality that is characterized by disputes over diagnostic evaluations and therapeutic decisions. With the widespread use of broad-spectrum antimicrobial agents and the increasing number of immunocompromised hosts, the etiology and the drug resistance patterns of pathogens responsible for CAP have changed. Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis remain the leading causes of CAP in immunocompetent patients. Opportunistic infections with organisms such as Pneumocystis jiroveci and Mycobacterium tuberculosis and other opportunistic fungal pneumonias should also be considered in the differential diagnosis of CAP in immunocompromised patients. This article examines the current peer-reviewed literature on etiology, risk factors, and outcomes of patients with CAP.

Effectiveness of influenza vaccination of children with recurrent respiratory tract infections in reducing respiratory-related morbidity within the households

To evaluate the effectiveness of influenza vaccination in reducing respiratory-related morbidity among children with recurrent respiratory tract infections (RRTIs) and their household contacts, 127 children aged 6 months-9 years (78 males; median age, 3.7 years) with a history of RRTIs (>/=6 episodes per year if aged >/=3 years; >/=8 episodes per year if aged <3 years) were randomized to receive the intranasal virosomal influenza vaccine (n=64 with 176 household contacts) or a control placebo (n=63 with 173 household contacts). During influenza season, the vaccinated children had fewer respiratory infections, febrile respiratory illnesses, prescribed antibiotics and antipyretics, and missed school days than the controls, and similar benefits and a reduction in the loss of parental work were observed among their household contacts. This study shows that the benefits of influenza vaccination extend to children with RRTIs and their family members and encourages to recommend its use in such children.

Prevalence and clinical significance of community-acquired penicillin-resistant pneumococcal pneumonia in Thailand

OBJECTIVE

The study aimed to evaluate the prevalence, clinical significance and outcome of community-acquired penicillin-resistant Streptococcus pneumoniae (PRSP) pneumonia in Thailand.

METHODOLOGY

We conducted a prospective study in culture-proven pneumococcal pneumonia. Pneumococci were defined as susceptible, intermediate resistance and high resistance according to the definitions of the United States National Committee for Clinical Laboratory Standards (NCCLS).

RESULTS

Forty-six consecutive patients were enrolled. Of the S. pneumoniae isolates collected, 41.3% were resistant to penicillin (37% intermediate resistance and 4.3% high resistance). Resistance to other antibiotics was 13% to ceftriaxone (8.7% intermediate resistance and 4.3% high resistance), 34.8% to erythromycin, 39.1% to tetracycline, 26.1% to chloramphenicol, and 43.5% to trimethoprim -sulfamethoxazole. Prior antibiotic use within 3 months was significantly associated with resistance to penicillin. The overall mortality of pneumococcal pneumonia was 26.1%. Multilobar involvement and requirement for mechanical ventilation proved to be associated with mortality. However, resistance to penicillin or ceftriaxone was not associated with death.

CONCLUSIONS

According to the US NCCLS guidelines, we found a high prevalence of drug-resistant S. pneumoniae in Thai patients with community-acquired pneumonia. Prior antibiotic use was significantly associated with penicillin resistance. However, the outcome was not related to in vitro penicillin susceptibility of S. pneumoniae isolated from the patients.

Community-acquired pneumonia in the emergency department: a practical approach to diagnosis and management

Pneumonia is one of the most common conditions for which patients seek emergency care. It is a challenging infection in that the spectrum of illness ranges from the nontoxic patient appropriate for outpatient antibiotics to the critically ill patient requiring intensive care hospitalization. Current data and diagnostic technology provide the emergency physician with the tools for an appropriately rapid evaluation and consideration of the differential diagnosis. Key critical thinking and application of published findings allow for intelligent empirical antibiotic treatment and risk stratification for the best disposition. Although antibiotic-resistant organisms increasingly are being identified, patients continue to benefit from early institution of standard ED treatment. Coverage for atypical organisms improves patient response and outcome. Finally, identification and treatment of the complications of pneumonia and accompanying sepsis must be considered by the ED physician when evaluating critically ill patients.

Clinical resistance encountered in the respiratory surveillance program (RESP) study: a review of the implications for the treatment of community-acquired respiratory tract infections

The Respiratory Surveillance Program (RESP) is a large-scale surveillance study of potential bacterial pathogens from respiratory tract infections that was performed over a 10-month period (July to April) during the 1999-2000 respiratory infection season. It is also the first study of its kind to derive its information entirely from community-based medical practices. This study, therefore, provides insight into the identity, frequency, and susceptibility of the possible pathogens isolated from patients encountered by primary care physicians. Reduction of antibiotic susceptibility in various bacterial pathogens may be of academic interest. However, it is only the emergence of clinical resistance (strains exhibiting minimum inhibitory concentrations above the resistance breakpoint) to commonly used antibacterial agents in the most prevalent species that has significant impact on empiric therapy choices. A review of data from RESP indicated that the most prevalent species were Moraxella catarrhalis, Haemophilus influenzae, Staphylococcus aureus, and Streptococcus pneumoniae. As expected, the prevalence of these bacterial isolates varied by disease state. The prevalence of clinical resistance to various antibiotics ranged, within these 4 species, between 0% and 92%. Resistance to the greatest number of drugs was expressed by S pneumoniae, followed by S aureus, H influenzae, and M catarrhalis. The prevalence of antibiotic resistance found among these community-isolated pathogens was surprisingly similar to that reported in hospital-based studies, suggesting that resistance is as important an issue in the community as it is in hospitals. With few exceptions, the prevalence of resistance was fairly uniform across disease states. The antibiotics most likely to encounter clinically resistant isolates during the treatment of community-acquired respiratory tract infections were penicillins, macrolides, and trimethoprim/sulfamethoxazole. The antibiotics least likely to encounter resistance were quinolones, followed by ceftriaxone and amoxicillin/clavulanate.

Antibiotic resistance in hospital pathogens--acquisition or spread?

Hospital resistant pathogens are a problem of hospital use allowing acquisition of multi-resistant strains. The use of antibiotics in the community and on the farm has little impact on hospital infection rates and prevalence of resistance in hospital bacteria. Once acquisition occurs the main problem is spread of clones to highly vulnerable patients. Attention to protective methods for such patients ought to be a priority in hospital infection control.

Improving inpatient antibiotic prescribing: insights from participation in a national collaborative

BACKGROUND

Increasing rates of antimicrobial resistance and the role antibiotic overuse plays in contributing to this problem have been widely documented and have prompted appeals to change prescribing practices. How to actually achieve such changes represents a major challenge. As part of the Institute for Healthcare Improvement (IHI) Breakthrough Series project Improving Prescribing Practices (IPP), in 1997-1998, Cook County Hospital (Chicago) worked with other institutions that chose antibiotics as their focus in this national collaborative.

PRACTICAL SUGGESTIONS

Practical suggestions are offered within six categories--adopting a general approach to improving antibiotic prescribing (marshalling credible evidence, addressing physician concerns and skepticism, and removing barriers to make it easier for prescribers to change); rethinking guidelines (providing syndrome-based guidance, revising national guidelines for local use, defining scenarios in which drug(s) can be safely withheld, offering alternatives, prospectively resolving conflicts over drug of choice and empiric regimens, and defining situations in which immediate treatment is and is not critical); getting the message out and changes implemented (using antibiotic order forms, computer order entry, and infectious disease specialist consultation); building viable linkages to leverage change (bridging disciplines); improving measurement; and promoting nondrug strategies and patients' roles in treating and preventing infection.

CONCLUSION

Antimicrobials are unique, being the only class of drug therapy that affects not only the patient to whom it is prescribed but other current and future patients as well. Institutions therefore have a special responsibility to ensure their efficient and judicious use. It is often easier to prescribe antibiotics than to exercise restraint.