Viral influenza-like illnesses: dynamic interrelationships during the 2015-2016 influenza season in hospitalized patients

In hospitalized children and adults, the temporal relationship of viruses causing influenza-like illnesses (ILIs) and influenza has not been well described. During the 2015-2016 influenza season at our hospital, the dynamic interrelationships between ILI viruses (human metapneumovirus, respiratory syncytial virus, human parainfluenza viruses 3 and 4, rhinoviruses/enteroviruses, and coronaviruses) and influenza A were characterized in 768 hospitalized children and adults.

Three Clusters of Bacillus Pseudobacteremia Related to a Radiometric Blood Culture Analyzer

During a ten-month period from September 1981 to July 1982 three episodes of pseudobacteremia due to Bacillus species occurred at this 550-bed institution. The first involved eight isolates, the second 11, and the third seven isolates of the organism, all with the same antibiogram.

The patients involved did not exhibit clinical signs of septicemia, and in only one case was more than one specimen per patient positive when multiple blood samples were obtained. Occasional blood cultures of Bacillus species identified in between clusters revealed a different antibiogram.

Extensive epidemiologic investigation of patient locations, phlebotomists, and time of cultures yielded no common source. Components involved in the transport and processing of blood cultures, including the radiometric blood culture processor, were also sampled but without recovery of the organism. After the last episode, a layer of dust was noted inside the machine, and culture of this dust grew Bacillus spp. with the same antibiogram as those found in the blood cultures. The filter from an air conditioning unit in close proximity to the machine grew several species of Bacillus.

It is presumed that Bacillus spores in the dust were introduced into the blood culture bottles following the heat sterilization of the gas sampling (inoculation/removal) needles.

Modification of the cover of the machine was undertaken to prevent access of dust bearing microbes to the inside of the machine. In addition, maintenance now includes regular disinfection/cleaning of the “floor” of the machine, and more frequent changes of the air conditioner filter.

Metronidazole Single versus Multiple Daily Dosing in Serious Intraabdominal/Pelvic and Diabetic Foot Infections

The purpose of the study was to compare the clinical efficacy of once-daily versus multiple dose regimens of metronidazole in inpatients with serious/systemic Bacteroides fragilis infections, i.e., intraabdominal/pelvic and diabetic foot infections. A retrospective chart review was performed on 145 adult inpatients who received combination therapy with metronidazole for B. fragilis abdominal/pelvic infection or diabetic (deep) foot infections/osteomyelitis. Exclusion criteria included metronidazole given for indications other than those mentioned, patients who received only one dose of metronidazole, and patients who received oral metronidazole only. The 145 patients were in two groups: 66 patients in the metronidazole 1 g (i.v.) q24h (Group A) and 79 patients who received metronidazole 500 mg (i.v./p.o.) q6-8h dosing (Group B). Patient demographics included age, gender, indications of metronidazole, concomitant, antibiotics, and co-morbidities. Data collection also included length of stay (LOS), antibiotic days, and clinical outcomes. The 145 patients in our study had a mean age of 66 years, 61% were female and 39% male. Most patients were being treated for definitive intraabdominal/pelvic infections (82%), or probable intraabdominal/pelvic infections (22%). Only 6% had deep diabetic foot infections of osteomyelitis (percentages exceed 100% since a patient can have more than one indication) and were included since B. fragilis is also and important pathogen in diabetic osteomyelitis. Group A patients had more concomitant antibiotics and co-morbidities (p < 0.0001 and p < 0.05 respectively, chi-square test for trend) than Group B patients. There were no statistically significant differences between groups A and B for LOS and antibiotic days (p = 0.42 and p = 0.92 respectively, by rank-sum test), but after adjusting for concomitant antibiotics and co-morbidities Group A patients had clinically shorter LOS and fewer antibiotic days. Unadjusted mortality and failure rates were non-significantly higher in group A (relative ratios of 12.1%/6.3% = 6.3% = 1.91 and 18.2%/ 10.1% = 1.80 respectively), but after adjusting for concomitant antibiotics and co-morbidities with stratification analysis, groups A and B were virtually the same (risk differences of </= 1%). The authors conclude that for B. fragilis infections, as part of combination therapy, metronidazole 1 g (i.v.) q 24h appears to eb as efficacious and not inferior to multiply-dosed metronidazole regimens. Once daily metronidazole, i.e., 1 g (i.v.) q24h for the treatment of serious systemic infections where B. fragilis is an important co-pathogen (intraabdominal/pelvic and deep diabetic foot infections) has pharmacokinetic and pharmaco-economic advantages.

Appropriateness of Empiric Gentamicin and Vancomycin Therapy for Bacteremias in Chronic Dialysis Outpatient Units in the Era of Antibiotic Resistance

Bacteremias in inpatient chronic HD units have been described, but there is little information on bacteremias in ambulatory HD units. To determine the frequency of bacteremia and pathogen distribution in ambulatory chronic HD units, we retrospectively reviewed our experience with 107 bacteremias in 5 chronic ambulatory HD units over a 3 year period. The object of the study was twofold. The first objective was to determine if bacteremias in ambulatory HD setting were substantially different in frequency or type than in the inpatient HD setting. Secondly, febrile patients suspected of having bacteremia in chronic HD patients are often empirically treated with vancomycin and gentamicin. Chronic HD patients require repeated and frequent venous access for HD. Bacteremias are common in chronic HD patients and may be primary or secondary and are often related to venous access site infections. The distributions of bacteremia pathogens in chronic HD patients are predominantly reflective of skin flora, i.e., staphylococci and to lesser extent aerobic Gram-negative bacilli. After S. aureus (MSRA/MSSA) and coagulase-negative staphylococcus (CoNS), enterococci are the next most important Gram-positive pathogens in bacteremic HD patients. Most strains of E. faecalis are sensitive to vancomycin and for practical purposes should be considered as vancomycin sensitive enterococci (VSE). In contrast, most strains of E. faecium are resistant to vancomycin and should be considered as vancomycin resistant enterococci (VRE). We retrospectively reviewed 107 patients on chronic ambulatory HD to determine the adequacy of empiric vancomycin and gentamicin prophylaxis. We found amikacin is preferred to gentamicin and that meropenem is an effective alternate substitution for gentamicin and vancomycin combination therapy.

Unnecessary repeat Clostridium difficile PCR testing in hospitalized adults with C. difficile-negative diarrhea

The aim of this study was to determine the extent and associated costs of repeat Clostridium difficile stool polymerase chain reaction (PCR) assays in patients with initially negative PCRs. C. difficile stool PCRs were done on adult hospitalized patients with diarrhea. The number/time course of repeat PCRs on initially negative PCR patients was determined. Of 5,027 C. difficile stool PCRs, 814 (16.2 %) were positive and 4,213 (83.8 %) were negative. Ninety-seven of the initially PCR-negative patients had >2 repeat tests 1-59 days after the initial negative stool PCR. Repeat negative PCR testing rarely resulted in a subsequent positive result (0.05 %). The unnecessary costs of 97 repeat PCRs was $32,658.00. Many of these patients were originally given empiric oral anti-C. difficile therapy, in spite of repeatedly negative PCRs.

Fever of unknown origin (FUO) in an immunocompetent adult due to cytomegalovirus (CMV) with polyclonal gammopathy

Fever of unknown origin (FUO) may be due to infection, malignancy, collagen vascular/inflammatory disorders, or other causes. Cytomegalovirus (CMV) infection is a rare cause of FUO in immunocompetent adults. We present a case of FUO due to CMV in an immunocompetent adult with polyclonal gammopathy on serum protein electrophoresis (SPEP).

Nosocomial swine influenza (H1N1) pneumonia: lessons learned from an illustrative case

In the spring of 2009, our institution found itself at the epicentre of the "herald wave" of the swine influenza (H1N1) pandemic in New York. We were inundated with hundreds of patients exhibiting influenza-like illnesses (ILIs), presenting for rapid influenza A testing. During this pandemic, an infant with newly diagnosed acute lymphatic leukaemia (ALL) was admitted for induction chemotherapy. After being in hospital for a week, she developed high fever and shortness of breath, although her chest X-ray was clear. She was admitted to the paediatric intensive care unit (PICU) for mechanical ventilation. As we were in the midst of the pandemic, diagnosis of H1N1 pneumonia was considered and reverse transcription-polymerase chain reaction for H1N1 was positive. Contact investigation revealed that none of her family members/visitors had been in recent/close contact with anyone with ILI/H1N1. The investigation also revealed that paediatric healthcare staff, in contact with H1N1 patients, had rotated into PICU to care for the patient. Although no specific individual could be identified, it seems likely that H1N1 was transmitted to the patient by a healthcare worker who worked both in the paediatric ward and the PICU. This is the first known case of nosocomial paediatric transmission of H1N1 pneumonia.

Pulmonary complications of babesiosis: case report and literature review

Reported here is a rare case of babesiosis with pulmonary complications followed by a review of the literature. Babesiosis presents clinically as a malaria-like illness with fever, chills, headache, fatigue with lymphopenia, atypical lymphocytes, mildly or transiently elevated serum transaminases, thrombocytopenia, and increased lactate dehydrogenase (LDH) levels. The diagnosis of babesiosis is based on identification of Babesia spp. on a peripheral blood smear. Babesiosis is usually mild in normal hosts, but it may be severe or even fatal in asplenic patients. Pulmonary manifestations are rare in babesiosis, but non-cardiogenic pulmonary edema (NCPE) is the most frequent manifestation. NCPE in babesiosis does not appear to be related to the degree of parasitemia or splenic function and its onset may be early or late. NCPE usually resolves rapidly with supportive treatment; it is rarely fatal. Clinicians should suspect NCPE in patients with babesiosis who acutely develop shortness of breath and have chest radiograph findings compatible with acute pulmonary edema without cardiomegaly or pleural effusions.

The atypical pneumonias: clinical diagnosis and importance

The most common atypical pneumonias are caused by three zoonotic pathogens, Chlamydia psittaci (psittacosis), Francisella tularensis (tularemia), and Coxiella burnetii (Q fever), and three nonzoonotic pathogens, Chlamydia pneumoniae, Mycoplasma pneumoniae, and Legionella. These atypical agents, unlike the typical pathogens, often cause extrapulmonary manifestations. Atypical CAPs are systemic infectious diseases with a pulmonary component and may be differentiated clinically from typical CAPs by the pattern of extrapulmonary organ involvement which is characteristic for each atypical CAP. Zoonotic pneumonias may be eliminated from diagnostic consideration with a negative contact history. The commonest clinical problem is to differentiate legionnaire's disease from typical CAP as well as from C. pneumoniae or M. pneumonia infection. Legionella is the most important atypical pathogen in terms of severity. It may be clinically differentiated from typical CAP and other atypical pathogens by the use of a weighted point system of syndromic diagnosis based on the characteristic pattern of extrapulmonary features. Because legionnaire's disease often presents as severe CAP, a presumptive diagnosis of Legionella should prompt specific testing and empirical anti-Legionella therapy such as the Winthrop-University Hospital Infectious Disease Division's weighted point score system. Most atypical pathogens are difficult or dangerous to isolate and a definitive laboratory diagnosis is usually based on indirect, i.e., direct flourescent antibody (DFA), indirect flourescent antibody (IFA). Atypical CAP is virtually always monomicrobial; increased IFA IgG tests indicate past exposure and not concurrent infection. Anti-Legionella antibiotics include macrolides, doxycycline, rifampin, quinolones, and telithromycin. The drugs with the highest level of anti-Legionella activity are quinolones and telithromycin. Therapy is usually continued for 2 weeks if potent anti-Legionella drugs are used. In adults, M. pneumoniae and C. pneumoniae may exacerbate or cause asthma. The importance of the atypical pneumonias is not related to their frequency (approximately 15% of CAPs), but to difficulties in their diagnosis, and their nonresponsiveness to beta-lactam therapy. Because of the potential role of C. pneumoniae in coronary artery disease and multiple sclerosis (MS), and the role of M. pneumoniae and C. pneumoniae in causing or exacerbating asthma, atypical CAPs also have public health importance.

Methicillin-resistant Staphylococcus aureus: clinical manifestations and antimicrobial therapy

Methicillin-resistant Staphylococcus aureus (MRSA) is a common skin coloniser and less commonly causes infection. MRSA colonisation should be contained by infection control measures and not treated. MRSA infections cause the same spectrum of infection as MSSA infections, i.e., skin/soft tissue infections, bone/joint infections, central IV line infections, and acute bacterial endocarditis (native valve/prosthetic valve). There is a discrepancy between in-vitro sensitivity and in-vivo effectiveness with MRSA. To treat MRSA infections, clinicians should select an MRSA drug with proven in-vivo effectiveness, i.e., daptomycin. Linezolid, quinupristin/dalfopristin, minocycline, or vancomycin, and not rely on in-vitro susceptibility data. For MRSA, doxycycline cannot be substituted for minocycline. Linezolid and minocycline are available for oral administration and both are also effective in treating MRSA CNS infections. Vancomycin is being used less due to side effects, (increasing MICs/resistance, VISA/VRSA), and increased VRE prevalence. The most potent anti-MRSA drug at the present time is daptomycin. Daptomycin is useful when rapid/effective therapy of MRSA bacteraemia/endocarditis is necessary. Daptomycin is also useful to treat persistent MRSA bacteraemias/MRSA treatment failures with other drugs, i.e., vancomycin. There is no difference in virulence between MSSA and MRSA infections if treatment is started early and with an agent that has in-vivo effectiveness.

Therapeutic implications of antibacterial resistance in community-acquired respiratory tract infections in children

The global spread of antibacterial resistance has important implications for the current and future management of bacterial respiratory tract infections in children. Data suggest that emerging resistance to commonly prescribed antibacterials, such as macrolides and trimethoprim-sulfamethoxazole, is beginning to impact the treatment of these infections, which include acute otitis media, tonsillitis/pharyngitis and community-acquired pneumonia. There is, therefore, a need for additional agents that are active against common respiratory tract pathogens, including resistant strains and are suitable for use in children. Infection control measures to curb the clonal spread of antibacterial resistance are also extremely important.

The chlamydial pneumonias

Chlamydia psittaci and Chlamydia pneumoniae are important causes of community-acquired pneumonias. Less commonly, C. trachomatis may cause pneumonia in adult immunocompromised hosts but more commonly is responsible for pneumonia in neonates. C. psittaci is the cause of psittacosis and is the only chlamydial zoonotic atypical pneumonia. C. pneumoniae is being increasingly recognized as the cause of up to 10% of community-acquired pneumonias. C. pneumoniae pneumonia has a clinical presentation like Mycoplasma pneumoniae pneumonia. C. pneumoniae is also responsible for a variety of other respiratory tract infections, e.g., sinusitis, bronchitis, otitis, pharyngitis and laryngitis. C. pneumoniae, like M. pneumoniae, may result in permanent airway disease, e.g., asthma, following infection. All chlamydia are sensitive to doxycycline. Macrolides are highly active against C. trachomatis, and in spite of in vitro susceptibility, are relatively inactive in vivo against C. psittaci and C. pneumoniae. Fluoroquinolones are also active against chlamydia. Doxycycline remains the preferred antibiotic to treat all chlamydial infections in nonpregnant adults.

Serum ferritin levels in West Nile encephalitis

West Nile encephalitis (WNE) presents clinically as aseptic meningitis, meningoencephalitis, encephalitis, or acute flaccid paralysis. Non-specific laboratory findings, e.g., leukopenia and thrombocytopenia, accompany WNE. Lymphopenia is marked and prolonged with WNE. Three patients with WNE were found to have elevated serum ferritin levels. Severity seemed to be directly related to serum ferritin levels. Although preliminary, the results suggested that serum ferritin levels >or= 500 ng/mL (normal range 5-187 ng/mL) occur late with WNE, and not in a control group of patients with viral meningitis or encephalitis.

Anthrax, tularemia, plague, ebola or smallpox as agents of bioterrorism: recognition in the emergency room

Bioterrorism has become a potential diagnostic consideration in infectious diseases. This article reviews the clinical presentation and differential diagnosis of potential bioterrorist agents when first presenting to the hospital in the emergency room setting. The characteristic clinical features of inhalation anthrax, tularemic pneumonia, plague pneumonia, including laboratory and radiographic finding, are discussed. Ebola vieus and smallpox are also discussed as potential bioterrorist-transmitted infections from the clinical and epidemiologic standpoint. In addition to the clinical features of the infectious diseases mentioned, the article discusses the infectious disease control and epidemiologic implications of these agents when employed as bioterrorist agents. The review concludes with suggestions for postexposure prophylaxis and therapy.

Retroperitoneal suppurative lymphadenitis complicating Staphylococcus aureus acute bacterial endocarditis

Acute bacterial endocarditis is commonly caused by Staphylococcus aureus. Acute bacterial endocarditis due to S. aureus is often complicated by metastatic infection to distant organs, i.e. the central nervous system, the heart, lungs, kidneys and joints. However, metastatic lymph node involvement has not been reported. This is a case report of S. aureus acute bacterial endocarditis complicated by metastatic suppurative lymphadenitis of retroperitoneal lymph nodes. We believe this is the first reported case of suppurative lymphadenitis of the mesenteric lymph nodes secondary to S. aureus acute bacterial endocarditis.

Pneumonia in the elderly

Pneumonia is one of the commonest infections in elderly patients. The pathogens responsible for pneumonias in the elderly are the same as in younger adults. Because of associated cardiopulmonary disease and/or impaired host defenses, pneumonia in elderly patients is associated with increased mortality and morbidity compared to younger patients. The clinical importance of pneumonias in the elderly relates to age-dependent and pathologic changes in the immune system as well as the lungs. Pneumonias in the elderly may be classified, for clinical purposes, according to their location of acquisition, i.e. community-acquired pneumonias, nursing home-acquired pneumonias, or hospital-acquired pneumonias. The clinical presentation of pneumonias in the elderly may be difficult, due to pre-existing cardiopulmonary disease that mimics pneumonia. This review discusses the diagnostic and therapeutic approaches to elderly patients with pneumonia.

Infections associated with steroid use

Patients receiving chronic steroids have an increased susceptibility to many different types of infections. The risk of infection is related to the dose of steroid and the duration of therapy. Although pyogenic bacteria are the most common pathogens, chronic steroid use increases the risk of infection with intracellular pathogens such as Listeria, many fungi, the herpes viruses, and certain parasites. Clinicians should consider both common and unusual opportunistic infections in patients receiving chronic steroids.

Infections in cirrhosis

Infection is a well-described complication of cirrhosis and is a major cause of death in this population. This article examines the types of infections related with cirrhosis, such as bacteremia, urinary tract infections, meningitis, and others.

Pneumonias in the compromised host

The choice of diagnostic modality depends on the patient's status, the expertise of the operator and pathologic resources of the hospital, and is a decision that should be guided by the infectious disease consultant and the clinicians involved in the care of the patient. Although the diagnosis must be tissue based, every attempt must be made to arrive at a tissue diagnosis as soon as possible in order to start specific therapy as soon as possible. It is as important to determine that the cause of the patient's pulmonary infiltrate is noninfectious versus infectious. Pulmonary embolic disease, CHF, ARDS, pulmonary hemorrhage, and pulmonary drug reactions may be reversible and require nonantimicrobially based therapies to treat the patient. Often clinicians are overwhelmed by differential diagnostic possibilities of exotic infectious disease pathogens and overlook easily treatable noninfectious disease mimics of pneumonia. Although differential diagnostic possibilities are great in the compromised host, clinicians should not be overwhelmed by diagnostic possibilities. Instead, clinicians should try to approach the patient syndromically, taking into account the degree and type of immunosuppression, the appearance and behavior of the infiltrates on the chest radiograph and the nature of the host defense defects and time relationships that will limit the differential diagnosis to relatively few diagnostic possibilities. The clinician can then treat empirically patients with presumed bacterial pneumonias and devise a diagnostic plan designed to arrive at a specific tissue diagnosis as soon as possible in patients who are likely to have nonbacterial infection of the lungs.

Infections associated with uremia and dialysis

Patients with chronic renal failure are predisposed to infections. Infections in end-stage renal disease patients are caused by immunosuppressive effects of uremia. Patients with renal failure on dialysis have impaired host defenses and may develop infections related to vascular access. This article reviews the infectious complications related to chronic renal failure in dialysis.

Central nervous system infections in the compromised host: a diagnostic approach

The diagnostic approach to the compromised host with CNS infection depends on an analysis of the patient's clinical manifestations of CNS disease, the acuteness or subacuteness of the clinical presentation, and an analysis of the type of immune defect compromising the patient's host defenses. Most patients with CNS infections may be grouped into those with meningeal signs, or those with mass lesions. Other common manifestations of CNS infection include encephalopathy, seizures, or a stroke-like presentation. Most pathogens have a predictable clinical presentation that differs from that of the normal host. CNS Aspergillus infections present either as mass lesions (e.g., brain abscess), or as cerebral infarcts, but rarely as meningitis. Cryptococcus neoformans, in contrast, usually presents as a meningitis but not as a cerebral mass lesion even when cryptococcal elements are present. Aspergillus and Cryptococcus CNS infections are manifestations of impaired host defenses, and rarely occur in immunocompetent hosts. In contrast, the clinical presentation of Nocardia infections in the CNS is the same in normal and compromised hosts, although more frequent in compromised hosts. The acuteness of the clinical presentation coupled with the CNS symptomatology further adds to limit differential diagnostic possibilities. Excluding stroke-like presentations, CNS mass lesions tend to present subacutely or chronically. Meningitis and encephalitis tend to present more acutely, which is of some assistance in limiting differential diagnostic possibilities. The analysis of the type of immune defect predicts the range of possible pathogens likely to be responsible for the patient's CNS signs and symptoms. Patients with diseases and disorders that decrease B-lymphocyte function are particularly susceptible to meningitis caused by encapsulated bacterial pathogens. The presentation of bacterial meningitis is essentially the same in normal and compromised hosts with impaired B-lymphocyte immunity. Compromised hosts with impaired T-lymphocyte or macrophage function are prone to develop CNS infections caused by intracellular pathogens. The most common intracellular pathogens are the fungi, particularly Aspergillus, other bacteria (e.g., Nocardia), viruses (i.e., HSV, JC, CMV, HHV-6), and parasites (e.g., T. gondii). The clinical syndromic approach is most accurate when combining the rapidity of clinical presentation and the expression of CNS infection with the defect in host defenses. The presence of extra-CNS sites of involvement also may be helpful in the diagnosis. A patient with impaired cellular immunity with mass lesions in the lungs and brain that have appeared subacutely or chronically should suggest Nocardia or Aspergillus rather than cryptococcosis or toxoplasmosis. Patients with T-lymphocyte defects presenting with meningitis generally have meningitis caused by Listeria or Cryptococcus rather than toxoplasmosis or CMV infection. The disorders that impair host defenses, and the therapeutic modalities used to treat these disorders, may have CNS manifestations that mimic infections of the CNS clinically. Clinicians must be ever vigilant to rule out the mimics of CNS infections caused by noninfectious etiologies. Although the syndromic approach is useful in limiting diagnostic possibilities, a specific diagnosis still is essential in compromised hosts in order to describe effective therapy. Bacterial meningitis, cryptococcal meningitis, and tuberculosis easily are diagnosed accurately from stain, culture, or serology of the CSF. In contrast, patients with CNS mass lesions usually require a tissue biopsy to arrive at a specific etiologic diagnosis. In a compromised host with impaired cellular immunity in which the differential diagnosis of a CNS mass lesion is between TB, lymphoma, and toxoplasmosis, a trial of empiric therapy is warranted. Antitoxoplasmosis therapy may be initiated empirically and usually results in clinical improvement after 2 to 3 weeks of therapy. The nonresponse to antitoxoplasmosis therapy in such a patient would warrant an empiric trial of antituberculous therapy. Lack of response to anti-Toxoplasma and antituberculous therapy should suggest a noninfectious etiology (e.g., CNS lymphoma). Fortunately, most infections in compromised hosts are similar in their clinical presentation to those in the normal host, particularly in the case of meningitis. The compromised host is different than the normal host in the distribution of pathogens, which is determined by the nature of the host defense defect. In compromised hosts, differential diagnostic possibilities are more extensive and the likelihood of noninfectious explanations for CNS symptomatology is greater. (ABSTRACT TRUNCATED)

Activities of bismuth thiols against staphylococci and staphylococcal biofilms

Indwelling medical devices are associated with infectious complications. Incorporating antimicrobials into indwelling materials may reduce bacterial colonization. Bismuth thiols are antibiofilm agents with up to 1,000-fold-greater antibacterial activity than other bismuth salts. Staphylococci are particularly sensitive, as determined by agar diffusion and broth dilution susceptibility testing. Bismuth-ethanedithiol inhibited 10 methicillin-resistant Staphylococcus epidermidis strains at 0.9 to 1.8, Staphylococcus aureus ATCC 25923 at 2.4, and S. epidermidis ATCC 12228 at 0.1 microM Bi(3+). Antiseptic-resistant S. aureus was sensitive to bismuth-2-3-dimercaptopropanol (BisBAL) at < or = 7 microM Bi(3+). Hydrogel-coated polyurethane rods soaked in BisBAL inhibited S. epidermidis for 39 days (inhibitory zone diameter in agar, > or = 30 mm for > 25 days). Slime from 16 slime-producing S. epidermidis strains was inhibited significantly by bismuth-3,4-dimercaptotoluene (BisTOL), but not by AgNO3, at subinhibitory concentrations. In conclusion, bismuth-thiols are bacteriostatic and bactericidal against staphylococci, including resistant organisms, but are also inhibitors of slime at subinhibitory concentrations. At subinhibitory concentrations, BisTOL may be useful in preventing the colonization and infection of indwelling intravascular lines, since staphylococci are important pathogens in this setting.

New uses of older antibiotics

Despite the development of extended-spectrum penicillins, cephalosporins, and quinolones, the older antimicrobial agents, doxycycline, minocycline, TMP-SMX, clindamycin, and metronidazole, still play an important role in the treatment of infectious diseases. All of these older drugs are well absorbed by the oral route, attaining serum levels equivalent to those achieved by parenteral administration. The availability of generic forms of the older drugs reduces their cost. Besides traditional uses, some older drugs have become the preferred therapy for newly recognized infectious diseases. Doxycycline is the preferred drug for rickettsial tickborne diseases, ehrlichiosis and early Lyme disease. TMP-SMX is the preferred drug for I. belli and Cyclospora. Minocycline has been used to treat MRSA and MRSE infections. Clindamycin or metronidazole combined with a quinolone is an excellent oral regimen for polymicrobial infections. [table: see text]

Antibiotic side effects

Antibiotic side effects are approached best from an individual agent perspective rather than from a class-related standpoint. As this article indicates, with the exception of drug fevers and drug rashes, most antibiotic side effects are related to individual agents and not class side effects. Clinicians should view antimicrobial side effects as related to each organ system and be aware that more often a nonmicrobial medication is the explanation for the drug side effect rather than the antimicrobial. Nonantimicrobial medications are the most common cause of drug fever; among antimicrobials, beta-lactams and sulfonamides are the most common causes of drug-induced fevers. Antimicrobial side effects have important implications for the patient, legal and economic implications for the hospital, and medicolegal implications for the physician. Antibiotic side effects that prolong hospitalization in today's managed care environment have important economic implications. Clinicians should be familiar with the most common side effects of the most frequently used antimicrobials, to minimize the potential of having adverse reactions occur in patients. Most adverse events related to antimicrobials are reversible rapidly on cessation of the medication. Irreversible toxicities include aminoglycoside-induced ototoxicity, Stevens-Johnson syndrome, and toxicity secondary to nitrofurantoin. The most common acute fatal drug reactions include hypersensitivity reactions resulting in anaphylaxis or the Stevens-Johnson syndrome and fatal hepatic necrosis secondary to trovafloxacin. Clinicians should eliminate the use of drugs associated with chronic or fatal toxicities because multiple therapeutic alternatives exist for virtually every potential infection.

Community-acquired pneumonia. Diagnostic and therapeutic approach

Optimal empiric therapy of CAP is with appropriate monotherapy (e.g., doxycycline, levofloxacin). Combination therapy is problematic because of potential side effects and high cost. Empiric coverage should have a high degree of activity against both typical and atypical pathogens. The antibiotic selected should have an excellent side-effect profile and be relatively inexpensive. Clinicians should be selective in their choice of antibiotic for CAP and choose an antimicrobial that has little or no resistance potential, is relatively inexpensive, and permits i.v.-to-PO switch monotherapy.

Nosocomial pneumonia. Diagnostic and therapeutic considerations

Many patients with presumed nosocomial pneumonia probably have infiltrates on the chest radiograph, fever, and leukocytosis resulting from noninfectious causes. Because of the high mortality and morbidity associated with nosocomial pneumonias, however, most clinicians treat such patients with a 2-week empiric trial of antibiotics. Before therapy is initiated, the clinician should rule out other causes of pulmonary infiltrates, fever, and leukocytosis that mimic a nosocomial pneumonia (e.g., pre-existing interstitial lung disease, primary or metastatic lung carcinomas, pulmonary emboli, pulmonary drug reactions, pulmonary hemorrhage, collagen vascular disease affecting the lungs, or congestive heart failure). If these disorders can be eliminated from diagnostic consideration, a 2-week trial of empiric monotherapy is indicated. The clinician should treat cases of presumed nosocomial pneumonia as if P. aeruginosa were the pathogen. Although P. aeruginosa is not the most common cause of nosocomial pneumonia, it is the most virulent pulmonary pathogen associated with nosocomial pneumonia. Coverage directed against P. aeruginosa is effective against all other aerobic gram-negative bacillary pathogens causing hospital-acquired pneumonia. The clinician should select an antibiotic for empiric monotherapy that is highly effective against P. aeruginosa, has a good side-effect profile, has a low resistance potential, and is relatively inexpensive in terms of its cost to the institution. The preferred agents for empiric monotherapy for nosocomial pneumonia are cefepime, meropenem, and piperacillin. Single organisms are responsible for nosocomial pneumonia, not multiple pathogens. S. aureus rarely, if ever, causes nosocomial pneumonia but is mentioned frequently in studies based on cultures of respiratory tract secretions. S. aureus, unless accompanied by a necrotizing pneumonia with rapid cavitation within 72 hours, in the sputum indicates colonization rather than infection and should not be addressed therapeutically. Antibiotics associated with a high resistance potential should not be used as monotherapy or included in combination therapy regimens (i.e., ceftazidime, ciprofloxacin, imipenem, or gentamicin). Combination therapy is more expensive than monotherapy and is indicated only when P. aeruginosa is extremely likely, based on its characteristic clinical presentation, or is proved by tissue biopsy. Therapy should not be based on respiratory secretion cultures regardless of technique. Optimal combination regimens include cefepime or meropenem plus levofloxacin or piperacillin or aztreonam or amikacin. Nosocomial pneumonias usually are treated for 14 days. Lack of radiographic or clinical response to appropriate empiric nosocomial pneumonia monotherapy after 14 days suggests an alternate diagnosis. In these patients, a tissue biopsy specimen should be obtained to determine the cause of the persistence of pulmonary infiltrates unresponsive to appropriate antimicrobial therapy.