Staphylococcus lugdunensis: an emerging pathogen

Staphylococcus lugdunensis endocarditis: lower mortality in the contemporary era?

Background

Staphylococcus lugdunensis is a virulent coagulase-negative Staphylococcus that is a rare cause of infective endocarditis (IE) associated with high mortality. A linear growth of IE has occurred over the past several years in Saskatchewan, with overlapping epidemics of human immunodeficiency virus (HIV)/hepatitis C virus driven by injection drug use (IDU). We hypothesized that given the unique challenges faced by our population with IDU and inequitable healthcare access, our cases of S. lugdunensis IE might differ from those in the published literature.

Methods

We retrospectively reviewed the cases of S. lugdunensis endocarditis admitted at our tertiary care hospitals in Saskatoon over a 6-year period and analyzed their baseline characteristics, antimicrobial susceptibility data, management, and outcome data, where available, for each patient.

Results

Of the 24 blood cultures positive for S. lugdunensis, as identified by our laboratory, we verified 6 cases of definite IE, and 2 cases of probable IE, applying the modified Duke’s criteria. A total of 5 of 8 cases involved native valves, with only 1 infection of the bioprosthetic mitral valve, seen in patient with IDU. A total of 5 of 8 cases involved the left-sided valves, with 1 of 8 involving the tricuspid valve. Only 1 death was recorded.

Conclusions

The male predominance and primarily left-sided valve infection we noted in our review were similar to results in the published literature. We noted a lower rate of surgical intervention and mortality than previously observed, which merits further study. We did not find coinfection with HIV and/or hepatitis C virus as an epidemiologic risk factor, likely owing to the low rate of IDU in our study.

Infectious diseases specialist consultation in Staphylococcus lugdunensis bacteremia

Background

Commensal coagulase negative Staphylococcus lugdunensis may cause severe bacteremia (SLB) and complications. Treatment of SLB is not fully established and we wanted to evaluate if infectious diseases specialist consultation (IDSC) would improve management and prognosis.

Methods

Multicenter retrospective study of SLB patients followed for 1 year. Patients were stratified according to bedside (formal), telephone (informal) or lack of IDSC within 7 days of SLB diagnosis.

Results

Altogether, 104 SLB patients were identified: 24% received formal bedside and 52% informal telephone IDSC whereas 24% were managed without any IDSC. No differences in demographics, underlying conditions or severity of illness were observed between the groups. Patients with bedside IDSC, compared to telephone IDSC or lack of IDSC, had transthoracic echocardiography more often performed (odds ratio [OR] 4.00; 95% confidence interval [CI] 1.31–12.2; p = 0.012) and (OR 16.0; 95% CI, 4.00–63.9; P<0.001). Bedside IDSC was associated with more deep infections diagnosed compared to telephone IDSC (OR, 7.44; 95% CI, 2.58–21.4; p<0.001) or lack of IDSC (OR, 9.56; 95% CI, 2.43–37.7; p = 0.001). The overall mortality was 7%, 10% and 17% at 28 days, 90 days and 1 year, respectively. Considering all prognostic parameters, patients with IDSC, compared to lack of IDSC, had lower 90 days and 1 year mortality (OR, 0.11; 95% CI, 0.02–0.51; p = 0.005) and (OR, 0.22; 95% CI, 0.07–0.67; p = 0.007).

Conclusion

IDSC may improve management and outcome of Staphylococcus lugdunensis bacteremia.

The Role of the Coagulase-negative Staphylococci (CoNS) in Infective Endocarditis; A Narrative Review from 2000 to 2020

Coagulase-negative staphylococci (CoNS) are part of the microbiota of human skin and rarely linked with soft tissue infections. In recent years, CoNS species considered as one of the major nosocomial pathogens and can cause several infections such as catheter-acquired sepsis, skin infection, urinary tract infection, endophthalmitis, central nervous system shunt infection, surgical site infections, and foreign body infection. These microorganisms have a significant impact on human life and health and, as typical opportunists, cause peritonitis in individuals undergoing peritoneal dialysis. Moreover, it is revealed that these potential pathogens are mainly related to the use of indwelling or implanted in a foreign body and cause infective endocarditis (both native valve endocarditis and prosthetic valve endocarditis) in patients. In general, approximately eight percent of all cases of native valve endocarditis is associated with CoNS species, and these organisms cause death in 25% of all native valve endocarditis cases. Moreover, it is revealed that methicillin-resistant CoNS species cause 60 % of all prosthetic valve endocarditis cases. In this review, we describe the role of the CoNS species in infective endocarditis, and we explicated the reported cases of CoNS infective endocarditis in the literature from 2000 to 2020 to determine the role of CoNS in the process of infective endocarditis.

Clinical Characteristics and Outcomes of Staphylococcus lugdunensis Prosthetic Joint Infections: A Multicenter Retrospective Analysis

Staphylococcus lugdunensis has been increasingly recognized as a cause of serious infections, particularly prosthetic joint infections (PJIs). The aim of this study was to describe the clinical characteristics, treatments, and outcomes of S lugdunensis PJIs. This was a retrospective multicenter study of consecutive adult patients with S lugdunensis PJIs from January 2007 through December 2017; 28 patients met inclusion criteria. The knee was the most commonly affected joint (67.9%), followed by the hip (25%). Clinical and microbiologic characteristics, treatment modalities, and outcomes were evaluated. Thirteen (46.4%) patients had two-stage revision, 9 (32.1%) had debridement with or without revision, 5 (21.4%) had no surgical intervention, and 1 (3.6%) had one-stage revision. Twenty-four (85.7%) patients had monomicrobial infection with S lugdunensis, whereas 4 had polymicrobial. Two patients had concomitant bacteremia. All isolates, except 1, were susceptible to oxacillin. Three patients with no surgical intervention received oral antibiotics, 2 were not treated, and 1 was discharged to hospice. Relapse was observed in 2 of 13 (15%) patients who had two-stage revision, 4 of 9 (44%) who had debridement, and 6 of 6 (100%) who had no surgical intervention or one-stage revision regardless of antibiotic treatment regimen. There was a significant difference in cure rate for patients who underwent two-stage revision compared with other treatment modalities (85% vs 33%, P=.009). Appropriate management of S lugdunensis PJI includes both aggressive surgical treatment and a prolonged course of antibiotics and is associated with excellent clinical response. Regardless of route or duration of antibiotic therapy, relapse is high for patients not treated with two-stage revision. [Orthopedics. 2020;43(6):345-350.].

Treatment of a Staphylococcus lugdunensis cervical epidural abscess

First reported in 1988, Staphylococcus lugdunensis is a virulent coagulase-negative Staphylococcus species often associated with endocarditis. This is the first case report describing this infection in the cervical spine. A 58-year-old, left-handed Caucasian woman with no significant medical history presented with neck and left arm pain. Neurological examination revealed mild left deltoid 4/5 weakness and myelopathy. She was found to have an epidural cervical spinal cord mass that was causing severe cord compression and underwent partial anterior cervical decompression of the mass. On entering what was believed to be the mass, yellow-tinged fluid was encountered. An abscess was immediately suspected, so the dura was not entered. The specimen sent for culture was identified a day later as S. lugdunensis A two-dimensional echocardiogram was negative for vegetations. A peripherally inserted central catheter line was placed and the patient discharged on 6 weeks of physical therapy and 6-8 weeks of intravenous cefazolin.

Staphylococcus lugdunensis sepsis and endocarditis in a newborn following lotus birth

A term newborn, who underwent lotus birth, developed Staphylococcus lugdunensis sepsis and endocarditis on the 1st day of life. This case reports an uncommon pathogen known to cause destructive endocarditis in the adult and paediatric populations, causing endocarditis in a neonate. We speculate that lotus birth, an atypical birthing practice, may have contributed to the development of this infection.

Primary lung abscess caused by Staphylococcus lugdunensis

Staphylococcus lugdunensis, a strain of coagulase-negative staphylococci, is part of the normal flora of human skin but can cause multiple infections at various sites. This microorganism has emerged as a major human pathogen. However, no study has reported primary lung abscess caused by S. lugdunensis. A 54-year-old alcoholic man without relevant past medical history was admitted because of primary lung abscesses. Empirical amoxicillin/clavulanate therapy was initially administered; however, the patient had persistent pleuritic chest pain and fever. He subsequently underwent resection of the lung abscess and removal of exudative pleural effusion on the fourth hospital day. Histopathologic examination confirmed the diagnosis of lung abscess, and colonies of gram-positive bacteria were identified. The culture specimen from the abscess was positive for S. lugdunensis, which was susceptible to amoxicillin/clavulanate, cefazolin, ciprofloxacin, clindamycin, erythromycin, oxacillin, teicoplanin, tetracycline, and vancomycin. Following resection and 3 weeks of amoxicillin/clavulanate therapy, the patient eventually recovered well without relapse. This case report is the first to describe S. lugdunensis as a cause of primary lung abscess; this microorganism should be considered a potential monomicrobial pathogen in primary lung abscess.

S. lugdunensisNative-Joint Septic Arthritis: Case Report and Review of the Literature

Staphylococcus lugdunensisis a skin commensal classified as a coagulase-negativeStaphylococcus(CoNS). Though CoNS is typically associated with less aggressive clinical disease thanStaphylococcus aureus, there is growing awareness thatS. lugdunensismay be as virulent asS. aureus. The association betweenS. lugdunensisand infective endocarditis is well known, but few reports of native-joint disease with this organism exist. We report a case a 28-year-old male with no prior medical problems presenting with native-joint septic arthritis. Cultures grewS. lugdunensis. To our knowledge, this is the fifth case reported in the literature.

Multicenter Study of the Clinical Presentation of Staphylococcus lugdunensis Bacteremia in Japan

Staphylococcus lugdunensis (SL) is a bacterium with a highly pathogenicity than most other coagulase-negative Staphylococcus spp. (CoNS). In Japan, data on this pathogen are sparse, and the current prevalence of SL bacteremia is unknown. Therefore, we investigated the prevalence of SL in blood culture specimens in a prospective multicenter study across 5 facilities. A total of 3,284 patients had positive blood cultures, and 2,478 patients had bacteremia. Among the patients with bacteremia, 7 patients (0.28%) had SL bacteremia. A total of 281 patients had CoNS bacteremia, with SL accounting for 2.49% of these cases. Of the 7 patients with SL bacteremia, 1 patient (14.3%) had infective endocarditis, and 1 patient (14.3%) died within 30 days. In this study, SL resulted in the development of bacteremia in select patients. Clinicians in Japan should be aware of the prevalence of SL and the complications of SL bacteremia.

Staphylococcus lugdunensis infections, filling in the gaps: a 3-year retrospective review from a comprehensive cancer center

OBJECTIVE

Staphylococcus lugdunensis is considered to be more aggressive than other coagulase-negative staphylococci (CoNS). There are gaps in knowledge regarding the importance of isolating S. lugdunensis from different sources and in different patient subsets. Our objective was to describe the spectrum, clinical manifestations, and outcomes of infections caused by S. lugdunensis in patients with cancer.

METHODS

A retrospective review of all cancer patients from whom S. lugdunensis was isolated in a pure culture from clinically significant sites.

RESULTS

Between 2011 and 2014, 2263 CoNS were isolated, of them 45 S. lugdunensis were isolated in a pure culture and were included in this analysis. Only three patients were neutropenic. Skin and skin structure infections (SSSIs) occurred most often (36 cases) followed by five blood stream infections, one of which had destructive endocarditis and four infections at other sites. Of the 36 SSSIs, 29 were related to surgical or invasive procedures, and six of these involved an implanted medical device. All isolates were susceptible to vancomycin, 98% to levofloxacin and 89% to oxacillin. All patients responded to the therapy.

CONCLUSIONS

Cancer patients including those with neutropenia do not appear to have an increased frequency of infections caused by S. lugdunensis. SSSIs are predominant and are often associated with surgical procedures and/or implanted medical devices. Blood stream infections caused by S. lugdunensis are uncommon but may have an increased rate of serious complications such as endocarditis. Nevertheless, these organisms are generally susceptible to multiple classes of antimicrobial agents, and the overall response to therapy is high.

The occurrence of infective endocarditis with Staphylococcus lugdunensis bacteremia: A retrospective cohort study and systematic review

BACKGROUND

Staphylococcus lugdunensis is a coagulase-negative staphylococcus with similar virulence characteristics as Staphylococcus aureus. Whether S. lugdunensis causes infective endocarditis (IE) in a similar proportion of cases as S. aureus (reported to be 12.6% in a definitive multicenter prospective study) is unclear.

METHODS

We conducted a retrospective cohort study of adult patients with at least one blood culture positive for S. lugdunensis at our institution from January 2006 to December 2014. We examined microbiology data, ascertained disease severity and determined the proportion of patients with definite or possible IE based on the 2000 Modified Duke Criteria. Because coagulase-negative staphylococci were routinely identified to the species level at our institution from 2012 onwards, we determined the proportion of patients with definite or possible IE before and after implementation of routine speciation. We also compared our results with reported proportions of IE among patients with S. lugdunensis bacteremia (SLB) in other institutions by conducting a systematic review of the scientific literature. Nonparametric bootstrapping methods were performed to determine 95% confidence intervals (CI) for proportions of IE in patients with SLB.

RESULTS

Seventy-four patients with SLB were identified, of whom 64% (47/74) had sepsis by SIRS criteria, and 18% (13/74) had severe illness by Pittsburgh bacteremia score (PBS). Kaplan-Meier survival analysis showed that one-year survival among patients with severe illness was worse than patients with non-severe illness (p = 0.02). Fifteen percent (11/74) of patients had definite or possible IE (95% CI 6.8-23.0%). The proportion of SLB patients with definite or possible IE was 15.8% (6/38, 95% CI 5.3-28.9%) prior to routine speciation and 13.9% (5/36, 95% CI 2.8-27.8%) after routine speciation (p = 0.71). Among patients with at least two positive blood cultures for S. lugdunensis, 25% (10/40, 95% CI 12.5-40.0%) had IE. Systematic review of the literature yielded eight relevant retrospective studies. Of studies that included patients with one or more positive blood cultures for S. lugdunensis, the proportion of IE ranged from 6.3% to 27.0%.

CONCLUSION

The proportion of definite or possible IE among patients with SLB is similar to the proportion of IE among patients with S. aureus bacteremia. The proportions of IE among patients with SLB at other institutions fall within the 95% CI yielded by bootstrapping. Our findings suggest that growth of S. lugdunensis in two separate blood cultures should prompt consideration of workup for IE.

Retropubic Midurethral Sling Colonization With Staphylococcus lugdunensis

BACKGROUND

We present a case of Staphylococcus lugdunensis colonization of a midurethral sling. Staphylococcus lugdunensis is a common skin colonizer and has been isolated in cases of implanted prosthetic devices.

CASE

A 52-year-old female presented with suprapubic pain and recurrent urinary tract infections with S. lugdunensis starting 3 months after a retropubic sling procedure. After several months of continued pain and a suspicion of a mesh-related infection, the sling was removed. Culture of the sling material grew oxacillin-susceptible S. lugdunensis. Her symptoms resolved after sling removal and a postoperative course of antibiotics.

CONCLUSIONS

To our knowledge, this is the first reported case of S. lugdunensis colonization of vaginal mesh. Surgeons should be aware and knowledgeable about the possible complications arising from insertion of midurethral slings.

Neonatal Staphylococcus lugdunensis urinary tract infection

Staphylococcus lugdunensis is a known pathogen of infective endocarditis, but not of urinary tract infection. We report a previously healthy neonate without congenital anomalies of the kidney and urinary tract who developed urinary tract infection due to Staphylococcus lugdunensis, illustrating that Staphylococcus lugdunensis can cause urinary tract infection even in those with no urinary tract complications.

Staphylococcus lugdunensis gluteal abscess in a patient with end stage renal disease on hemodialysis

A 57-year-old end stage renal disease patient on hemodialysis (HD) presented with sepsis secondary to right buttock abscess and overlying cellulitis. She was started on broad-spectrum antibiotic therapy and underwent incision and drainage with marked improvement. Her cultures grew methicillin-resistant Staphylococcus lugdunensis. This bacterium is more virulent than other coagulase negative staphylococci and has been implicated in causing a variety of serious infections but it has been underreported as a cause of skin infections in HD patients and possible other patient populations.

Staphylococcus lugdunensis: A Rare Pathogen for Osteomyelitis of the Foot

Staphylococcus lugdunensis is an aggressive gram-positive bacteria that can lead to devastating infections in humans. S. lugdunensis has been associated with rare cases of osteomyelitis of the vertebra, prosthetic implants, and endocarditis. Reports of this organism associated with osteomyelitis of the foot or ankle have been infrequent. We present a unique case of acute osteomyelitis of a foot caused by S. lugdunensis after a patient stepped on a thorn. Our case is unique, because the radiographic changes were noted within 4 days, despite normal plain films and magnetic resonance images on the day of admission. This finding suggests the aggressiveness and virulence of S. lugdunensis. In addition, we report the first case of foot osteomyelitis as a result of isolated S. lugdunensis that involved 2 distinct specimens with 2 different antibiotic sensitivity reports.

Culture-independence for surveillance and epidemiology

Culture-independent methods in microbiology (quantitative PCR (qPCR), sequencing, microarrays, direct from sample matrix assisted laser desorption/ionization time of flight mass spectroscopy (MALDI-TOF MS), etc.) are disruptive technology. Rather than providing the same results as culture-based methods more quickly, more cheaply or with improved accuracy, they reveal an unexpected diversity of microbes and illuminate dark corners of undiagnosed disease. At times, they overturn existing definitions of presumably well-understood infections, generating new requirements for clinical diagnosis, surveillance and epidemiology. However, current diagnostic microbiology, infection control and epidemiology rest principally on culture methods elegantly optimized by clinical laboratorians. The clinical significance is interwoven; the new methods are out of context, difficult to interpret and impossible to act upon. Culture-independent diagnostics and surveillance methods will not be deployed unless the reported results can be used to select specific therapeutics or infection control measures. To cut the knots surrounding the adoption of culture-independent methods in medical microbiology, culture-dependent methods should be supported by consistent culture-independent methods providing the microbial context. This will temper existing biases and motivate appropriate scrutiny of the older methods and results.

Multiplex identification of gram-positive bacteria and resistance determinants directly from positive blood culture broths: evaluation of an automated microarray-based nucleic acid test

BACKGROUND

A multicenter study was conducted to evaluate the diagnostic accuracy (sensitivity and specificity) of the Verigene Gram-Positive Blood Culture Test (BC-GP) test to identify 12 Gram-positive bacterial gene targets and three genetic resistance determinants directly from positive blood culture broths containing Gram-positive bacteria.

METHODS AND FINDINGS

1,252 blood cultures containing Gram-positive bacteria were prospectively collected and tested at five clinical centers between April, 2011 and January, 2012. An additional 387 contrived blood cultures containing uncommon targets (e.g., Listeria spp., S. lugdunensis, vanB-positive Enterococci) were included to fully evaluate the performance of the BC-GP test. Sensitivity and specificity for the 12 specific genus or species targets identified by the BC-GP test ranged from 92.6%-100% and 95.4%-100%, respectively. Identification of the mecA gene in 599 cultures containing S. aureus or S. epidermidis was 98.6% sensitive and 94.3% specific compared to cefoxitin disk method. Identification of the vanA gene in 81 cultures containing Enterococcus faecium or E. faecalis was 100% sensitive and specific. Approximately 7.5% (87/1,157) of single-organism cultures contained Gram-positive bacteria not present on the BC-GP test panel. In 95 cultures containing multiple organisms the BC-GP test was in 71.6% (68/95) agreement with culture results. Retrospective analysis of 107 separate blood cultures demonstrated that identification of methicillin resistant S. aureus and vancomycin resistant Enterococcus spp. was completed an average of 41.8 to 42.4 h earlier using the BC-GP test compared to routine culture methods. The BC-GP test was unable to assign mecA to a specific organism in cultures containing more than one Staphylococcus isolate and does not identify common blood culture contaminants such as Micrococcus, Corynebacterium, and Bacillus.

CONCLUSIONS

The BC-GP test is a multiplex test capable of detecting most leading causes of Gram-positive bacterial blood stream infections as well as genetic markers of methicillin and vancomycin resistance directly from positive blood cultures.

Staphylococcus Lugdunensis, An Aggressive Coagulase-Negative Pathogen not to be Underestimated

The new emerging coagulase-negative pathogen Staphylococcus lugdunensis is responsible for severe cardiac and joint infections. Since the biochemical phenotypic systems designed for the identification of CoNS do not appear to be species specific and are hardly reliable for the discrimination of S. lugdunensis from other staphylococci, its precise identification requires fine molecular methods. The pathogenic mechanisms by which S. lugdunensis causes severe infections are not yet completely elucidated and in this review its virulence and toxic determinants are surveyed as well as its adhesins and biofilm production.

Interactions of Staphylococci with Osteoblasts and Phagocytes in the Pathogenesis of Implant-Associated Osteomyelitis

In spite of great advancements in the field of biomaterials and in surgical techniques, the implant of medical devices is still associated with a high risk of bacterial infection. Implant-associated osteomyelitis is a deep infection of bone around the implant. The continuous inflammatory destruction of bone tissues characterizes this serious bone infectious disease. Staphylococcus aureus and Staphylococcus epidermidis are the most prevalent etiologic agents of implant-associated infections, together with the emerging pathogen Staphylococcus lugdunensis. Various interactions between staphylococci, osteoblasts, and phagocytes occurring in the peri-prosthesis environment play a crucial role in the pathogenesis of implant-associated osteomyelitis. Here we focus on two main events: internalization of staphylococci into osteoblasts, and bacterial interactions with phagocytic cells.

Iron-regulated surface determinant (Isd) proteins of Staphylococcus lugdunensis

Staphylococcus lugdunensis is the only coagulase-negative Staphylococcus species with a locus encoding iron-regulated surface determinant (Isd) proteins. In Staphylococcus aureus, the Isd proteins capture heme from hemoglobin and transfer it across the wall to a membrane-bound transporter, which delivers it into the cytoplasm, where heme oxygenases release iron. The Isd proteins of S. lugdunensis are expressed under iron-restricted conditions. We propose that S. lugdunensis IsdB and IsdC proteins perform the same functions as those of S. aureus. S. lugdunensis IsdB is the only hemoglobin receptor within the isd locus. It specifically binds human hemoglobin with a dissociation constant (K(d)) of 23 nM and transfers heme on IsdC. IsdB expression promotes bacterial growth in an iron-limited medium containing human hemoglobin but not mouse hemoglobin. This correlates with weak binding of IsdB to mouse hemoglobin in vitro. Unlike IsdB and IsdC, the proteins IsdJ and IsdK are not sorted to the cell wall in S. lugdunensis. In contrast, IsdJ expressed in S. aureus and Lactococcus lactis is anchored to peptidoglycan, suggesting that S. lugdunensis sortases may differ in signal recognition or could be defective. IsdJ and IsdK are present in the culture supernatant, suggesting that they could acquire heme from the external milieu. The IsdA protein of S. aureus protects bacteria from bactericidal lipids due to its hydrophilic C-terminal domain. IsdJ has a similar region and protected S. aureus and L. lactis as efficiently as IsdA but, possibly due to its location, was less effective in its natural host.

Case-control study of Staphylococcus lugdunensis infection isolates from small companion animals

BACKGROUND

Coagulase-negative Staphylococcus lugdunensis has recently been shown to cause invasive infections of people, which are similar in pathogenic effect to those caused by Staphylococcus aureus. Little is known about the pathogenicity of S. lugdunensis in companion animals.

OBJECTIVES

To compare potential risk factors for infection, body sites affected, and whether cases and controls had been treated with antimicrobial drugs based upon susceptibility test results.

ANIMALS

Thirty-three cases of S. lugdunensis infection (25 dogs, six cats and two small mammals) were identified between January 2003 and August 2011. Two Staphylococcus pseudintermedius controls, which were identified by the microbiology laboratory immediately before and after each S. lugdunensis case, were host-species matched to each case.

METHODS

A retrospective case-control analysis.

RESULTS

During the period evaluated, the prevalence of S. lugdunensis infection was 1.3 cases per 10,000 hospital admissions for dogs and 0.95 cases per 10,000 admissions for cats (P = 0.453). In univariate analyses, S. pseudintermedius isolation was significantly associated with skin infections (P < 0.0001), while S. lugdunensis isolation was associated with the respiratory tract (P = 0.03) and other deep tissues (P = 0.005). Cases were less likely than controls to have been treated based upon susceptibility test results (P = 0.02). A conditional logistic regression analysis showed isolation of S. lugdunensis to be associated with recent (≤ 30 days) steroid administration (odds ratio, 17.72; 95% confidence interval, 2.35-132.82; P = 0.005); and in-patient status (odds ratio, 9.67; 95% confidence interval, 2.18-42.88; P = 0.003).

CONCLUSIONS

These results suggest that S. lugdunensis may cause invasive infections in companion animals, which should be treated with antimicrobials based upon susceptibility tests when available.