Tetracyclines, chloramphenicol, erythromycin, clindamycin, and metronidazole.

The tetracyclines are effective in the treatment of Chlamydia, Mycoplasma pneumoniae, and rickettsial infections and also can be used for gonococcal infections in patients unable to tolerate penicillin. These drugs may cause gastrointestinal irritation, diarrhea, phototoxic dermatitis, and vestibular damage, and fatal reactions due to hepatotoxicity have occurred in pregnant women. Chloramphenicol has a broad spectrum of bacteriostatic activity, but its association with suppression of the bone marrow and aplastic anemia has relegated it to a historical role. Erythromycin is the drug of choice for the treatment of infections caused by M. pneumoniae, Legionella species, group A beta-hemolytic streptococci, and Streptococcus pneumoniae. The frequency of serious adverse effects associated with the use of erythromycin is low; dose-related epigastric distress may occur. Clindamycin is bactericidal to most nonenterococcal gram-positive aerobic bacteria and many anaerobic microorganisms. Although historically it was a frequent cause of antibiotic-associated diarrhea and colitis, clindamycin is considered an excellent alternative to beta-lactam antibiotics for treatment of many staphylococcal infections, and it has therapeutic utility in anaerobic infections and in several protozoan infections in immunosuppressed patients. Metronidazole is efficacious for treating nonpulmonary anaerobic infections, various parasitic infections (trichomoniasis, amebiasis, and giardiasis), nonspecific vaginitis, and Clostridium difficile-mediated colitis. With use of metronidazole, mild side effects such as epigastric discomfort, diarrhea, reversible neutropenia, and allergic-type cutaneous reactions may occur.     

Role of fluoroquinolones in lower respiratory tract infections

Oral quinolones such as ciprofloxacin are promising agents in the treatment of serious bronchopulmonary infections due to susceptible gram-negative micro-organisms such as Haemophilus influenzae, Branhamella catarrhalis, Klebsiella pneumoniae and even Pseudomonas aeruginosa. Their moderative activity against Streptococcus pneumoniae may limit the use of these agents in the treatment of acute exacerbations of chronic bronchitis and in the empiric management of community-acquired bacterial pneumonia. Further prospectively designed studies are needed to address this issue. The ability of quinolones to effectively penetrate bronchial mucosa and to be concentrated within macrophages may afford additional advantage to these agents. They should not be used as a sole agent in the treatment of aspiration pneumonia nor anaerobic pleuropulmonary disease. Quinolones are very active in experimental models of Legionnaire's disease and deserve further clinical study. Ciprofloxacin is a promising alternative to standard parenteral drugs in the management of Pseudomonas aeruginosa infections in adults with cystic fibrosis. The potential for drug interactions with theophylline must be kept in mind for patients on both of these drugs.     

Clindamycin in Treatment of Aspiration Pneumonia in Children

Twenty-eight patients with anaerobic pleuropulmonary infections were treated with clindamycin alone or clindamycin with gentamicin. Sixteen of the patients presented with pneumonitis, nine with necrotizing pneumonia, and three with lung abscesses. The average length of treatment was 13.8 days, and the duration of temperature after initiation of therapy was 3.1 days. The predominant isolates were anaerobic gram-positive cocci (23 isolates), Bacteroides melaninogenicus (14), Bacteroides fragilis (9), and Fusobacterium nucleatum (11). The most frequent aerobic isolates were alpha-hemolytic streptococci (12), Diplococcus pneumoniae (12), Pseudomonas aeruginosa (9), Klebsiella pneumoniae (7), group A beta-hemolytic streptococci (5), Staphylococcus aureus (9), and Escherichia coli (6). All patients responded to the therapy and were cured of the infection. There were no side effects observed from the administration of clindamycin. None of the patients developed any blood dyscrasia, liver damage, diarrhea, or colitis. Clindamycin appears to be effective in the treatment of mixed aerobic and anaerobic pleuropulmonary infections in children, alone or with an aminoglycoside when indicated.     

Carbapenems and monobactams: imipenem, meropenem, and aztreonam

Imipenem and meropenem, members of the carbapenem class of beta-lactam antibiotics, are among the most broadly active antibiotics available for systemic use in humans. They are active against streptococci, methicillin-sensitive staphylococci, Neisseria, Haemophilus, anaerobes, and the common aerobic gram-negative nosocomial pathogens including Pseudomonas. Resistance to imipenem and meropenem may emerge during treatment of P. aeruginosa infections, as has occurred with other beta-lactam agents; Stenotrophomonas maltophilia is typically resistant to both imipenem and meropenem. Like the penicillins, the carbapenems have inhibitory activity against enterococci. In general, the in vitro activity of imipenem against aerobic gram-positive cocci is somewhat greater than that of meropenem, whereas the in vitro activity of meropenem against aerobic gram-negative bacilli is somewhat greater than that of imipenem. Daily dosages may range from 0.5 to 1 g every 6 to 8 hours in patients with normal renal function; the daily dose of meropenem, however, can be safely increased to 6 g. Infusion-related nausea and vomiting, as well as seizures, which have been the main toxic effects of imipenem, occur no more frequently during treatment with meropenem than during treatment with other beta-lactam antibiotics. The carbapenems should be considered for treatment of mixed bacterial infections and aerobic gram-negative bacteria that are not susceptible to other beta-lactam agents. Indiscriminate use of these drugs will promote resistance to them. Aztreonam, the first marketed monobactam, has activity against most aerobic gram-negative bacilli including P. aeruginosa. The drug is not nephrotoxic, is weakly immunogenic, and has not been associated with disorders of coagulation. Aztreonam may be administered intramuscularly or intravenously; the primary route of elimination is urinary excretion. In patients with normal renal function, the recommended dosing interval is every 8 hours. Patients with renal impairment require dosage adjustment. Aztreonam is used primarily as an alternative to aminoglycosides and for the treatment of aerobic gram-negative infections. It is often used in combination therapy for mixed aerobic and anaerobic infections. Approved indications for its use include infections of the urinary tract or lower respiratory tract, intra-abdominal and gynecologic infections, septicemia, and cutaneous infections caused by susceptible organisms. Concurrent initial therapy with other antimicrobial agents is recommended before the causative organism has been determined in patients who are seriously ill or at risk for gram-positive or anaerobic infection.     

Colitis associated with clindamycin therapy.

Clindamycin (7-chloro-7-deoxylincomycin) may induce mild or severe colitis. In 28 months, clindamycin-associated diarrhea was encountered in 8 patients who had received oral therapy. Severe, acute colitis was seen in 4 older patients, 3 of whom had acute pseudomembranous colitis and one who had an adynamic ileus mimicking an acute abdomen. Mild colitis with protracted diarrhea occurred in 4 younger patients who had mild, nonspecific inflammation in the rectum which responded to symptomatic treatment. The mechanism and true incidence of diarrhea as a sequel of clindamycin therapy are unknown. In all 8 patients, the use of clindamycin was arbitrary. Because of potentially serious gastrointestinal disturbance, including acute pseudomembranous colitis, clindamycin should be reserved for anaerobic and other serious infections.     

Current use for old antibacterial agents: polymyxins, rifamycins, and aminoglycosides

This article reviews three classes of antibacterial agents that are uncommonly used in bacterial infections and therefore can be thought of as special-use agents. The polymyxins are reserved for gram-negative bacilli that are resistant to virtually all other classes of drugs. Rifampin is used therapeutically, occasionally as a companion drug in treatment of refractory gram-positive coccal infections, especially those involving foreign bodies. Rifaximin is a new rifamycin that is a strict enteric antibiotic approved for treatment of traveler's diarrhea and is showing promise as a possible agent for refractory Clostridium difficile infections. The aminoglycosides are used mainly as companion drugs for the treatment of resistant gram-negative bacillary infections and for gram-positive coccal endocarditis.     

Current issues on resistance,treatment guidelines,and the appropriate use of fluoroquinolones for respiratory tract infections

BACKGROUND: Community-acquired respiratory tract infections comprise a large percentage of diseases treated by primary care physicians, and rates of antimicrobial use for respiratory tract infections are increasing. The fluoroquinolones comprise a drug class with broad-spectrum activity against many of the key pathogens associated with community-acquired respiratory tract infections, including Streptococcus pneumoniae, and other significant pathogens, such as Staphylococcus aureus and Pseudomonas aeruginosa. While fluoroquinolones have gained popularity, the settings for their appropriate use in treating respiratory tract infections remain unclear. OBJECTIVE: In this article, the mechanisms of fluoroquinolone resistance in S. pneumoniae, treatment guidelines, and the mode of spread of resistance are reviewed. METHODS: The authors conducted a MEDLINE search for articles published from 1990 to the present. Search terms included Streptococcus pneumoniae, fluoroquinolones, and resistance. Articles were selected for inclusion based on their relevance to the objective of this review. RESULTS: Although 3 sets of treatment guidelines for community-acquired pneumonia (CAP) currently exist in the United States, a consensus for the role of fluoroquinolones in the outpatient management of CAP has not been achieved. Factors mitigating for restraint in the outpatient use of fluoroquinolones include concern for the spread of resistance to "innocent-bystander" organisms, such as S. aureus and P. aeruginosa, as well as possible inappropriate "trickle-down" use for other, less severe respiratory syndromes, such as bronchitis. CONCLUSION: Although the fluoroquinolones are potent agents against respiratory pathogens and have a clearly defined role in the treatment of hospitalized patients with CAP, their optimal role in the outpatient management of respiratory tract infections remains controversial.     

Clindamycin, metronidazole, and chloramphenicol.

Clindamycin, metronidazole, and chloramphenicol are three antimicrobial agents useful in the treatment of anaerobic infections. Clindamycin is effective in the treatment of most infections involving anaerobes and gram-positive cocci, but emerging resistance has become a problem in some clinical settings. Metronidazole is effective in the treatment of infections involving gram-negative anaerobes, but it is unreliable in the treatment of gram-positive anaerobic infections and is ineffective in treating aerobic infections. Additionally, metronidazole is often the drug of choice in treating infections in which Bacteroides fragilis is a serious concern. Chloramphenicol is effective in the treatment of a wide variety of bacterial infections, including serious anaerobic infections, but is rarely used in Western countries because of concerns about toxicity, including aplastic anemia and gray baby syndrome.     

Pharmacodynamics of fluoroquinolones against Streptococcus pneumoniae in patients with community-acquired respiratory tract infections

Fluoroquinolone antibiotic agents have demonstrated efficacy in the treatment of respiratory tract infections. This analysis was designed to examine the relationship between drug exposure, as measured by the free-drug area under the concentration-time curve at 24 h (AUC(24))/MIC ratio, and clinical and microbiological responses in patients with community-acquired respiratory tract infections involving Streptococcus pneumoniae. The study population included 58 adult patients (34 males, 24 females) who were enrolled in either of two phase III, randomized, multicenter, double-blind studies of levofloxacin versus gatifloxacin for the treatment of community-acquired pneumonia or acute exacerbation of chronic bronchitis. Clearance equations from previously published population pharmacokinetic models were used in conjunction with dose and adjusted for protein binding to estimate individual patient free-drug AUC(24)s. In vitro susceptibility was determined in a central laboratory by broth microdilution in accordance with NCCLS guidelines. Pharmacodynamic analyses were performed on data from all evaluable patients with documented S. pneumoniae infection using univariate and multivariable logistic regression; pharmacodynamic breakpoints were estimated using Classification and Regression Tree analysis. A statistically significant (P = 0.013) relationship between microbiological response and the free-drug AUC(24)/MIC ratio was detected. At a free-drug AUC(24)/MIC ratio of <33.7, the probability of a microbiological response was 64%, and at a free-drug AUC(24)/MIC ratio of >33.7, it was 100% (P < 0.01). These findings may provide a minimum target free-drug AUC(24)/MIC ratio for the treatment of infections involving S. pneumoniae with fluoroquinolone antibiotics and provide a paradigm for the selection of fluoroquinolones to be brought forward from drug discovery into clinical development and dose selection for clinical trials. Further, when target free-drug AUC(24)/MIC ratios are used in conjunction with stochastic modeling techniques, these findings may be used to support susceptibility breakpoints for fluoroquinolone antibiotics and S. pneumoniae.     

Efficacy of ceftriaxone in serious bacterial infections.

Ceftriaxone is a new semisynthetic cephalosporin with broad-spectrum in vitro activity and an unusually long serum half-life. The clinical efficacy of ceftriaxone was evaluated in 35 infections in 34 patients; 12 of these patients had skin and soft tissue infections, 10 had infections of the urinary tract, 8 had pneumonia, 2 had biliary tract infections, 1 had sinusitis, 1 had diverticulitis, and 1 had a retroperitoneal abscess. Of the 35 infections, 9 were bacteremic. The bacteria isolated included Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Streptococcus faecalis, other streptococcal species, Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Serratia marcescens, Enterobacter cloacae, Haemophilus influenzae, Pseudomonas aeruginosa, Bacteroides fragilis, other Bacteroides species, and anaerobic cocci. Improvement or cure occurred in 32 episodes, for a response rate of 91%. There were three treatment failures in patients with soft tissue infections. No serious drug toxicities were observed. At a dosage regimen of 1 g every 12 h the peak and trough serum antibiotic concentrations were well above the minimal inhibitory concentrations of most pathogens. Our findings suggest that ceftriaxone is a safe and effective antibiotic for therapy of serious bacterial infections.     

Antiviral drugs for common respiratory diseases. What's here, what's to come

Progress is being made in the development of drugs for the prevention and treatment of viral respiratory infections. Two drugs currently available to clinicians are amantadine (Symmetral) and ribavirin (Virazole). Oral amantadine is effective for both treatment and prevention of uncomplicated influenza A infections. Although vaccination continues as the mainstay of influenza prevention, amantadine is useful for unvaccinated patients if complications are likely. When used for treatment, it must be started within the first 48 hours of illness. Ribavirin appears to be safe for treatment of respiratory syncytial virus infections in nonintubated infants. It must be delivered by aerosol in a hospital setting. Patients at risk for complications should be given the drug as early as possible in the course of the disease. Efficacy has yet to be proven in intubated patients, but the drug is probably safe to use with proper supervision. On the horizon are rimantadine and the interferons. Rimantadine is similar to amantadine in its action and indications for use and has a lower incidence of side effects. The interferons have not been the hoped-for panacea for viral respiratory infections but may be useful in a nasal spray for the prevention of colds caused by rhinovirus.     

Results of a Clinical Trial of Cefoxitin, a New Cephamycin Antibiotic

Cefoxitin was administered intravenously to 143 patients, 67% of whom were seriously ill. The rate of cure or improvement was 93%. The study was conducted in two phases; the first was an open, controlled clinical comparison of cefoxitin and cephalothin. In this phase, 28 patients received cefoxitin and 29 received cephalothin. In the second phase, cefoxitin alone was used for the treatment of an additional 115 patients. Twenty bacteremic patients treated with cefoxitin were cured or improved in 95% of cases. The infecting organism was eradicated in all bacteremic patients. All of 14 anaerobic or predominantly anaerobic infections were cured or improved. The infecting anaerobic organism was eliminated in 86% of the cases. Twenty-five patients infected by cephalothin-resistant, cefoxitin-susceptible gram-negative rods were cured. Three patients each with infective endocarditis and osteomyelitis were cured. The incidence of adverse experiences was: 1.4% drug eruption; 2% each asymptomatic serum transaminase elevation and leukopenia; and 2.5% asymptomatic eosinophilia. The incidence of severe thrombophlebitis was 5%. No permanent or serious adverse reactions were encountered. Although the numbers of patients in some categories were too small to permit statistical evaluation, I feel that cefoxitin may be a useful new antibiotic for treatment of infections caused by cehalothin-resistant bacteria and by anaerobic organisms.     

Therapeutic efficacy of liposome-encapsulated gentamicin in rat Klebsiella pneumoniae pneumonia in relation to impaired host defense and low bacterial susceptibility to gentamicin

Long-circulating liposomes (LCL) may be used as targeted antimicrobial drug carriers as they localize at sites of infection. As a result, LCL-encapsulated gentamicin (LE-GEN) has demonstrated superior antibacterial activity over the free drug in a single-dose study of immunocompetent rats with Klebsiella pneumoniae pneumonia. In the present study, the therapeutic efficacy of LE-GEN was evaluated by monitoring rat survival and bacterial counts in blood and lung tissue in clinically relevant models, addressing the issue of impaired host defense and low bacterial antibiotic susceptibility. The results show that in immunocompetent rats infected with the high-GEN-susceptibility K. pneumoniae strain, a single dose of LE-GEN is clearly superior to an equivalent dose of free GEN. Yet complete survival can also be obtained with multiple doses of free GEN. In leukopenic rats infected with the high-GEN-susceptible K. pneumoniae strain, free GEN at the maximum tolerated dose (MTD) was needed to obtain survival. However, with the addition of a single dose of LE-GEN to free-GEN treatment, complete survival can be obtained using a sevenfold-lower cumulative amount of GEN than with free-GEN treatment alone. In leukopenic rats infected with low-GEN-susceptible K. pneumoniae cells, free GEN at the MTD did not result in survival. The use of LE-GEN is needed for therapeutic success. Increasing LE-GEN bilayer fluidity resulted in an increased GEN release from the liposomes and hence improved rat survival, thus showing the importance of the liposome lipid composition for therapeutic efficacy. These results warrant further clinical studies of liposomal formulations of aminoglycosides in immunocompromised patients with severe infections.     

Comparison of once-daily cephalosporin regimens for community-acquired lower respiratory tract infections in patients with chronic lung disease

The efficacy of cefonicid and of ceftriaxone, administered once daily for the treatment of lower respiratory tract bacterial infections (pneumonia or bronchitis), was evaluated and compared in 118 patients with chronic lung disease. The patients were randomly assigned to receive 1 gm of either drug, intravenously or intramuscularly, daily for three to 11 days (mean, seven days). Pathogenic bacteria were isolated from sputum in 59% of patients; Haemophilus influenzae and Streptococcus pneumoniae predominated. Clinical cure or improvement was noted in 95% and 93% of patients treated with cefonicid and ceftriaxone, respectively, and bacteriologic cure or improvement in 69% and 81% (the differences were not significant). Side effects were infrequent and similar in the two treatment groups, except that diarrhea was more common in the ceftriaxone group (11%, versus 4.4% in the cefonicid group). It is concluded that patients with chronic lung disease who experience acute exacerbations associated with infection caused by H influenzae or S pneumoniae, or other susceptible organisms, can be effectively treated with once-daily administration of either cefonicid or ceftriaxone.     

Intravenous metronidazole for treatment of infections involving anaerobic bacteria.

Intravenous metronidazole was administered, either by continuous or intermittent infusion, to 20 patients with infections involving anaerobic bacteria; 14 of the 20 patients were changed to oral administration of metronidazole for completion of therapy. Six of eight patients with infections derived from oropharyngeal bacterial flora were cured; the addition of ampicillin was required in one patient, however, because of an incomplete response to metronidazole. Eight of eleven evaluable patients with infections derived from bowel flora were also cured by metronidazole or metronidazole plus an aminoglycoside. Of 93 anaerobic bacteria isolated before therapy, 89 were susceptible to 16 micrograms or less of metronidazole per ml. Mean plasma levels of metronidazole were 27.6 +/- 11.4 micrograms/ml in patients receiving continuous infusions of drug and 19.9 +/- 10.7 micrograms/ml (trough) in patients receiving intermittent infusions. Two patients developed peripheral neuropathy during therapy. Metronidazole is an effective agent for the treatment of anaerobic infections. Because metronidazole is not active against facultative and aerobic bacteria, the addition of a second antimicrobial agent may be required for the treatment of mixed anaerobic-aerobic infections.     

Pneumonia. Patient profiles, choice of empiric therapy, and the place of third-generation cephalosporins.

Choosing appropriate antimicrobial therapy for patients with pneumonia requires knowledge of the etiologic agents seen in specific kinds of patients at specific times and places. For community-acquired pneumonia, there is an important difference in the agents seen in the normal and the compromised host. The normal host most often presents with viral, mycoplasmal, or pneumococcal pneumonia. The exact place of Chlamydia pneumoniae is still under study. A normal host who aspirates is at risk of anaerobic pneumonia. Normal hosts with influenza may acquire superinfection with Streptococcus pneumoniae, Haemophilus influenzae, or Staphylococcus aureus. Under specific epidemiologic conditions, community-acquired pneumonia may be due to Legionella species, Yersinia pestis, Francisella tularensis, Coxiella burnetii, Chlamydia psittaci, a mycotic agent, or tuberculosis. Patients with chronic bronchitis and emphysema are predisposed to H. influenzae, Moraxella catarrhalis, and S. pneumoniae infections. HIV-infected patients are likely to have Pneumocystis carinii pneumonia and pneumonia due to cytomegalovirus, S. pneumoniae, and H. influenzae. Patients with diabetes, nursing-home patients, hospitalized patients, immuno-compromised patients, and patients with recent antibiotic therapy are predisposed to pneumonia due to Gram-negative aerobic bacilli of enteric and environmental origin. Initial therapy should be directed at the likely organism or organisms based on hospital susceptibility surveillance. In the normal host with community-acquired pneumonia, the therapy will often be penicillin G or erythromycin. In the patient predisposed to Gram-negative pneumonia, a third-generation cephalosporin with or without an aminoglycoside is the usual choice.     

Feasibility of radioimmunotherapy of experimental pneumococcal infection

Streptococcus pneumoniae is an important cause of community-acquired pneumonia, meningitis, and bacteremia. The problem of pneumococcal disease is exacerbated by increasing drug resistance. Furthermore, patients with impaired immunity are at high risk for invasive pneumococcal infections. Thus, there is an urgent need for new approaches to antimicrobial therapy. Antibody therapies take advantage of the specificity and high affinity of the antigen-antibody interaction to deliver antibacterial compounds to a site of infection in the form of naked or conjugated antibodies. We have recently established that radioimmunotherapy (RIT) can be used to treat experimental fungal infections in mice. In the present study, we investigated the feasibility of applying a RIT approach to the treatment of S. pneumoniae infection by evaluating the susceptibility of S. pneumoniae to radiolabeled antibody in vitro and in an animal infection model. For the specific antibody carrier, we used human monoclonal antibody D11, which binds to pneumococcal capsular polysaccharide 8. We have selected the alpha particle emitter (213)Bi as the radionuclide for conjugation to the antibody. Incubation of serotype 8 S. pneumoniae with (213)Bi-D11 resulted in dose-dependent killing of bacteria. RIT of S. pneumoniae infection in C57BL/6 mice showed that 60% more mice survived in the (213)Bi-D11-treated group (80 micro Ci) than in the untreated group (P < 0.01). The treatment did not cause hematological toxicity, as demonstrated by platelet counts. This feasibility study establishes that RIT can be applied to the treatment of bacterial infections.     

儿童下呼吸道肺炎克雷白杆菌感染临床及药敏分析

目的探讨儿童下呼吸道肺炎克雷白杆菌感染的临床情况以及细菌的耐药性,给予临床用药指导性建议。方法选取湖北省十堰市妇幼保健院2011年4月至2013年6月下呼吸道感染患儿720例,其中肺炎克雷白杆菌感染患者178例,并选取同期非下呼吸道感染患儿640例,总结患儿临床特点,实施药敏试验,分析结果。结果下呼吸道感染患儿发生肺炎克雷白杆菌感染的例数远高于其它感染患儿,对比差异有统计学意义。性别、湿啰音及哮鸣音对感染发生率影响不大;患者临床表现有发热、住院时间长、存在并发症、胸片肺纹理增粗、应用抗菌药均导致较高的KB感染率,对比差异有统计学意义。肺炎克雷白杆菌对于喹诺酮类、氨基糖甙类、第三代头孢菌素等抗菌物耐药率较高,其中耐药率较低的是亚胺培南、头孢哌酮/舒巴坦。结论婴幼儿是肺炎克雷白杆菌感染的高发群体,合理使用以第三代头孢菌素为主的抗菌药物对抗肺炎克雷白杆菌感染意义重大。     

Therapy of lower respiratory tract infections with moxalactam.

Moxalactam was evaluated in the therapy of lower respiratory tract infections in 40 patients. The most common organisms isolated were Streptococcus pneumoniae (37.2%) and Haemophilus influenzae (21.5%). Gram-negative enteric organisms were isolated from six patients. No patient was evaluated as a treatment failure; however, two patients died of unrelated causes either during therapy or in the immediate posttherapy period. We determined the comparative minimal inhibitory concentrations of moxalactam, cefamandole, and cephalothin for our aerobic clinical isolates. Susceptibilities of the anaerobic isolates were measured by the Kirby-Bauer method. All isolates were susceptible to moxalactam. Moxalactam was found to be highly effective in the therapy of lower respiratory tract infections.